Journal

Vol.40/No.2 (156) (2025)

作者:

Vol.40/No.2 (156) (2025)

Title Statistical Study on the Relationship Between the Depth of Neutralization and the Age of Concrete in RC Buildings
Author Chia-Chin Hsu, Wen-I Liao, Fu-Pei Hsiao
Keywords concrete, neutralization depth, age, compressive strength, durability
Abstract Neutralization of concrete is one of the main factors causing the aging of reinforced concrete (RC) structures and shortening their service life. Neutralization of concrete leads to the loss of functionality of the protective film on the reinforcement, which in turn causes corrosion of the reinforcement and a decrease in structural bearing capacity. Therefore, estimating the depth of concrete neutralization is an important research topic for the durability assessment of reinforced concrete structures. In this study, the material testing data by core sampling from 454 Taiwan RC school buildings were collected. By using relevant formulas used in Japan and Taiwan for predicting neutralization depth, regression analysis was carried out on the material test data base on those formula. Parameters such as concrete neutralization depth, region, concrete age, and concrete compressive strength were used to regressively analyze and derive a durability assessment model suitable for Taiwan’s environment and characteristics of concrete material. Corresponding formulas for neutralization depth and time-variable properties such as building age were obtained. The estimated concrete neutralization depth curve from this study can be used to evaluate the neutralization depth of RC structures during their service life, thereby determining whether neutralization depth affects the durability of the structures, and executing appropriate maintenance or repair and retrofit measure.
Title A Preliminary Exploration of the Traction-Based Deep Energy Method (tDEM) for Solving Elastic Body Problems
Author Kuan-Chung Lin, Hung-Liang Wang, Kuo-Chou Wang
Keywords deep learning, PINNs, DEM, tDEM, engineering applications, accuracy
Abstract With the rapid advancement of deep learning technologies in addressing complex physical problems and engineering applications, physics-informed neural networks (PINNs) and deep energy method (DEM), as two primary deep learning approaches integrating physical knowledge, have emerged as hot topics in computational science and engineering research. PINNs enable efficient and accurate predictions under data-scarce conditions by embedding physical laws into the neural network training regimen. In contrast, DEM utilize deep learning frameworks to establish energy models of systems, adept at simulating complex physical processes such as material deformation and fracture. Despite the significant strides made by PINNs and DEM in simulating complex physical systems, challenges remain in the computational costs of model training and enhancing model generalizability. This study introduces a novel traction-based deep energy method (tDEM), considering the boundary effects of tractions, evolved from the mixed DEM (mDEM) and amalgamating the strengths of both PINNs and DEM. Whereas mDEM introduced constitutive behavior during training, incurring higher computational expenses, tDEM concentrates on traction boundary conditions, aiming to reduce computational overhead. Future research will delve into these issues to further augment model precision and application scope. This paper not only reviews the latest advancements and engineering applications of PINNs and DEM but also proposes improvements, discusses the main challenges faced, and envisages future directions. It aims to provide valuable insights for researchers in the field and to propel the innovative application of deep learning in solving physical problems.
Title Seismic Design, Testing and Analysis of CoverPlate Stiffened Steel Panel Damper
Author Shun-Wei Hsu, Keh-Chyuan Tsai, An-Chien Wu
Keywords steel panel damper, capacity design, stiffener, cover plate, finite element model analysis
Abstract The three-segment steel shear panel damper (SPD) consists of an inelastic core (IC) that controls overall strength and could dissipate energy through large inelastic shear deformation. The two elastic joints (EJs) at the both ends of the SPD that remain elastic and provide lateral stiffness. Stiffeners are welded to the IC web to delay the shear buckling. This study employs hot-rolled, as opposed to built-up, sections to fabricate the SPD. This study proposes a cover-plate stiffened steel panel damper (CSPD). It involves cutting specific hot-rolled steel beam to obtain the doubler plates and cover plates, which are welded respectively to the web and the outer surfaces of the f lange at the both ends of the same hot-rolled steel beam. For example, with a section depth of 800mm, height of 2600mm, the same design shear force, and similar lateral stiffness, the proposed CSPD weighs only 87% of the conventional 3-segment SPD. This study intentionally uses SN490B steel for specimens to validate the design procedures for stiffeners in the IC. Test results, of two 2.60 m tall full-scale CSPD specimens using RH800 × 300 × 14 × 26 section with different IC height and stiffeners, confirm that the cover plates and doubler plates work as expected. This study confirms that the proposed CSPD design procedures can effectively estimate the IC shear deformational capacity, lateral stiffness and maximum shear strength of the CSPD. The proposed finite element model can accurately simulate the strength, stiffness, and hysteretic behavior of the CSPDs. This study tabulates the complete design results for CSPDs using American Institute of Steel Construction (AISC) sections with typical heights and inter-story drift demands. Results of additional finite element model parametric studies confirm that different IC stiffener arrangements can achieve the targeted shear deformational capacities as predicted using the proposed design procedure.
Title Seismic Compactness and Risk Assessments of Circular Steel Bridge Piers
Author Wen-Yu Xiao, Tung-Yu Wu, Chi-Rung Jiang, Yu-Chen Ou
Keywords single-column steel bridge piers, compactness requirements, finite element analysis, ductility capacity, risk analysis, near-fault ground motions
Abstract Bridge piers, which are ductile components of bridges, need to exhibit sufficient energy dissipation under earthquakes. However, there is little emphasis on the compactness requirements for steel bridge piers in Taiwan seismic design codes. Structural engineers can only refer to seismic design guidelines from other countries, but the difference in the seismic design concept makes them potentially inappropriate for Taiwan. To address this shortcoming, this study investigates single-column steel bridge piers with varied compactness and axial load levels. The ductility capacity of each pier is determined by quasi-static analysis and considered as the failure criteria in the subsequent risk assessment. Assuming located in the Taipei basin zone II, the seismic risk of steel bridge piers is evaluated using the failure probability during the 50-year lifespan and under the seismic scenario of the Shanchiao fault. Based on the results of ductility capacity and risk assessment, the seismic compactness requirements are proposed for single-column steel bridge piers.
Title Experimental Study of High-Mode Buckling Behavior of Flat Steel Core in a Buckling-Restrained Brace
Author Chih-Wei Chang, Pao-Chun Lin, Bing-Cheng Wu
Keywords buckling-restrained brace, local bulging failure, high-mode buckling, cyclic loading test, all-steel restrainer
Abstract Buckling-restrained braces (BRBs) featuring flat steel core plates can be susceptible to local bulging failures when the restrainer lacks the necessary stiffness and strength. These failures arise from outward forces generated by high-mode buckling waves within the steel core. However, the methods for evaluating these high-mode buckling waves and the associated outward forces have remained elusive. This study addresses this gap by conducting cyclic loading tests on five BRB specimens with all-steel restrainers. These tests allow for direct observation of high-mode buckling waves during loading. Among the specimens, three have core segment lengths of 300 mm, each with varying debonding layer thicknesses (0.6 mm, 2 mm, and 4 mm). The remaining two specimens have approximately 900 mm core segments with a 2 mm thick debonding layer. All f ive specimens displayed stable hysteretic responses until the steel core fractured. Load cells were used to directly measure the outward forces induced by the steel core plate during testing. Strain gauges attached to the steel core surface provided insights into the distribution of strain variations at the high-mode buckling waves. The results indicate that adopting the tangent modulus theorem is a suitable method for estimating high-mode buckling wavelengths. Furthermore, this study establishes relationships between the outward forces and gap dimensions, including their growth over time. This research proposes a method to estimate outward forces, accounting for bending moments developed at the crests of high-mode buckling waves and considering restrainer stiffness. This method can serve as a valuable tool for assessing the risk of local bulging failure in BRBs.

Vol.40/No.1 (155) (2025)

作者:

Vol.40/No.1 (155) (2025)

TitleLong-Term Health Monitoring of Steel Arch Bridges—A Case Study of the Dayuan Bridge on National Highway No. 2
Author Po-Hsin Lee, Yu-Chi Sung, Chun-Wei Chuang, Chin-Kuo Su, Min-Chun Lai, Kuo-Hung Chao, Tz-Wei Wang, Tsair-Yi Luo
Keywords bridge monitoring, cable force assessment, forced vibration analysis, monitoring threshold 
AbstractIn cable-supported bridge types (such as suspension bridges, cable-stayed bridges, steel arch bridges, and extra-dosed bridges), the primary load-bearing components are cables, and their stability directly impacts the bridge’s overall structural integrity. Therefore, long-term monitoring of cable forces is particularly crucial. Common cable force evaluation formulas used internationally, including string theory, beam column theory, and Zui theory, produce varying results depending on the bridge’s structural system and the boundary conditions at the ends of the cables. To accurately account for the boundary conditions of the cables, this study adopts a forced vibration analysis approach, using the National Highway No. 2 Dayuan Steel Arch Bridge as a case study. The study establishes a cable force-frequency relationship curve that aligns with the actual conditions of the cables. Based on the validated numerical model and one year of on site monitoring data, it performs long-term monitoring and structural analysis in terms of deck subsidence, cable force, and environmental temperature. This includes reviewing the established alert and action thresholds, applying these findings to predict future bridge behavior, and providing bridge management authorities with data for decision-making and timely interventions.
TitleEstablishment and Preliminary Result of Long Term Inspection and Monitoring System in Wuxi No. 1 Bridge on National Highway 3
AuthorMeng-Kang Chung, Ming-Xing Wu, Chien-Hung Chen, Kang-Yu Peng
Keywordsbridge deflection, bridge monitoring, automated monitoring, instant monitoring, prestressed tendon inspection
AbstractWith the proliferation of prestressed concrete bridges and the aging of existing structures, the demand for maintenance and retrofitting has surged. The inspection and monitoring system play a crucial role in verifying the effectiveness of maintenance and strengthening efforts, as well as bridge management during service life. This article presents a comprehensive case study based on the retrofitting project of Wuxi No. 1 Bridge on National Highway 3, detailing the installation, configuration, and outcomes of the long-term inspection and monitoring system implemented following the strengthening of the bridge’s superstructure. The aim is to validate the effectiveness of the strengthening work and provide a reference for other bridge management and maintenance cases in the future. For monitoring the bridge’s deck profile changes, settlement gauges and displacement meters were employed, with thermometers installed to account for temperature effects. To measure the forces in the external prestressed tendons, an elasto-magnetic sensor (EMS) was used, and additional measurement wires were installed to facilitate non-destructive testing of tendon corrosion. According to the inspection and monitoring results following the retrofitting, the strengthening project has successfully mitigated the previous continuous downward deformation of the bridge, and no corrosion or significant loss of tension in the prestressed tendons has been observed.
TitleImpulse Response Technique for Assessing the Quality of Post-Installed Rebar
AuthorPei-Wun Wu, Jian-Hong Lai, Chih-Peng Yu
Keywordsquality assessment of planting bars, nondestructive evaluation, stress waves, impact responses
AbstractThis study evaluates the bond condition of post-installed rebars using an impact response method, providing a feasible detection technique for current post-installed rebar construction in civil engineering. The primary theory relies on the stress waves propagating through the rebar, and a methodology for detecting the effective embedded length of the rebar is developed through numerical simulation analysis. From the high-frequency peak differences in the time-frequency spectrum, the total length of the rebar can be obtained, and by subtracting the exposed length, the total embedded length can be confirmed. Additionally, by observing the trend of peak frequencies, one can determine whether the rebar has reached the critical bond length. For cases where the relative stiffness is not high, the proposed evaluation formula estimates the equivalent ratio of rebar bond length. Preliminary research results indicate that using impact vibration response to assess the bond quality of post-installed rebars allows simultaneous identification of the relationship between the exposed rebar length, embedded depth, and the epoxy bond length for quantitative evaluation. Therefore, this technique, with its quick operation and accessible analysis, can effectively provide a general understanding of the embedded condition of the rebar on-site.
TitleExperimental and Simulation Study on the Residual Seismic Performance of Low-Rise Earthquake-Damaged Reinforced Concrete Walls
AuthorWen-I Liao, Fang-Fei Lin, Syuan-Jhen Chen, Yu-Ze Chen
KeywordsRC wall, damage, residual stiffness, residual strength, seismic performance
AbstractResearch on the residual strength, stiffness, and energy dissipation capacity of earthquakedamaged reinforced concrete (RC) shear walls remains relatively limited. This lack of studies leads to the difficulty in simulating and evaluating the seismic capacity of damaged RC structures, making the accuracy of safety assessments for earthquake-damaged structures challenging. Therefore, this study focuses on shear-controlled low-rise RC shear walls damaged by earthquakes, conducting tests on their post-earthquake seismic capacity, numerical simulations, and presentation of simplified capacity curves for damaged walls. First, cyclic loading tests were conducted on three low-rise RC shear walls with different pre-damage levels to investigate the impact of damage severity on stiffness, strength, and energy dissipation capacity. In addition, a simplified capacity curve model was proposed to describe the residual lateral capacity of RC walls at different damage levels, facilitating the execution of nonlinear pushover analyses. This model enables engineers to easily convert the capacity of undamaged walls to that of earthquakedamaged walls. Lastly, the test results were compared with numerical simulations using the cyclic softening membrane model in open system for earthquake engineering simulation (OpenSees) to validate the accuracy of the simulations and confirm appropriate model parameter settings, allowing for subsequent extensive parameter studies to reduce the costs of large-scale experiments. By integrating all research findings, this study thoroughly explores the residual seismic performance of earthquake-damaged RC shear walls and provides reliable simulation recommendations, offering valuable reference for evaluating the residual seismic performance of damaged RC structures in practical engineering applications.
TitleEarthquake Damage Assessment Model for Natural Gas Distribution Pipelines
AuthorGee-Yu Liu, Pao-Ching Chou, Hsiang-Yuan Hung
Keywordsnatural gas systems, gas distribution pipelines, scenario earthquake, damage assessment, repair rate
AbstractNatural gas plays a vital role in daily life, serving as one of the primary lifelines. The distribution of natural gas to customers occurs through extensive pipeline systems that span a wide area, facing high seismic risk due to Taiwan’s location in one of the world’s most earthquakeprone areas. A literature review of methodologies of damage prediction models of gas pipes has been conducted. As the development and practice of natural gas distribution systems in Taiwan are very similar to those in Japan, the review was more focused on the models that have been implemented in Japan. In this study, a model for assessing the damage of natural gas distribution pipelines resulting from earthquakes has been proposed. It comprises a repair rate formula for ground shaking hazard, a correction model to account for the likeliness of soil liquefaction hazard, and a set of correction factors specifying the relative fragility of different gas pipes. The proposed repair rate formula is a derivation from a Japanese formula, which employs the peak ground velocity (PGV) as seismic intensity factor. It has been proven feasible in Taiwan, too, as it agrees well with a previous study based on the damage data of the 1999 Chi-Chi earthquake. Finally, an earthquake scenario simulation of the two natural gas utilities in Tainan has been demonstrated.

Vol.39/No.4 (154) (2024)

作者:

Vol.39/No.4 (154) (2024)

TitleInvestigation, Evaluation, Strengthening Design & Construction and Long-Term Monitoring of Wuxi No. 1 Bridge on National Highway 3
AuthorMeng-Kang Chung, Ming-Xing Wu, Chien-Hung Chen, Kang-Yu Peng, Sheng-Fa Lin, Tsair-Yi Luo, Jiunn-Jye Jeng, Yen-Tiem Pai
Keywordsprestressed concrete girder retrofitting, carbon fiber reinforced polymer, external tendon, electrically isolated tendon system, replaceable post-tensioned external tendon system, bridge monitoring
AbstractWith the proliferation of prestressed concrete bridges and the aging of existing structures, the demand for maintenance and retrofitting has surged. This article presents a comprehensive case study based on the retrofitting project of Wuxi No. 1 Bridge on National Highway 3, detailing the methodology and considerations employed at each stage, encompassing investigation, evaluation, strengthening design, construction, and long-term monitoring. The retrofitting strategy for the superstructure of Wuxi No. 1 Bridge involved the utilization of carbon fiber reinforced polymer (CFRP) to enhance both flexural and shear capacity. To validate the effectiveness of CFRP, supplementary experiments were conducted during construction, with the results iteratively provided to the designer. External tendons were adopted to adjust superstructure stress, achieving Protection Level 3 (PL3) in accordance with the corrosion protective classification of The International Federation for Structural Concrete (fib) and Post-Tensioning Institute (PTI). Various techniques, including vacuum-assisted grouting, the electrically isolated tendon (EIT) system, elasto-magnetic sensor (EM Sensor), and a replaceable post-tensioned external tendon system, were amalgamated to ensure the durability, monitorability, and replaceability of the external tendon system. A long-term monitoring system was implemented to evaluate the effectiveness of retrofit by continuously assessing structural behavior. The insights gained from this project serve as a valuable reference for future bridge management and maintenance.
TitleDevelopment of Auxiliary Program for Seismic Capacity Assessment of RC Structures
AuthorYa-Ching Chang, Chien-Kuo Chiu, Tsung-Chih Chiu, Wen-I Liao
Keywordsseismic capacity assessment, nonlinear hinge, auxiliary program
Abstract

This research develops a seismic analysis auxiliary program for structures. The main objectives are (1) to provide automation assistance for input file of TEASPA (Taiwan earthquake assessment and strengthening of structures by pushover analysis) V3 and V4 developed by the National Center for Research on Earthquake Engineering, such as calculating the effective flange width of beams, the effective length of beams and columns, adjusting the plastic hinge position of windowsill columns, etc. This aims to reduce the tedious input work and minimize human errors for engineers. (2) Based on the theory of TEASPA V4, a modified model for column plastic hinges is proposed. It offers automated calculation of nonlinear hinge parameters, addressing to improve the slow convergence in using P-M interaction plastic hinges for columns. This modification also enables users of ETABS versions with only M3 plastic hinge function to conduct seismic assessments for high-rise buildings according to TEASPA V4. In modified P-M column hinges, the seismic-induced moment and axial force are assumed to increase proportionally. The corresponding axial force at the yield point of the P-M curve is determined, and the capacity of the column is calculated based on this force. Additionally, the program provides a function for determining seismic capacity using the ATC-40 capacity spectrum method or the method based on design code, obtaining seismic performance corresponding to different ductility. Two buildings are analyzed as examples, and the results are compared against TEASPA V3 and V4, including base shear strength, seismic performance, and discussions on failure modes to validate the accuracy of this program. The program can be downloaded at:                          https://teaspa.ncree.org.tw/Home/ DownloadFile/13

TitleEffect of Shear Strength Formula for Masonry Window Spandrel in Pushover Analysis of RC Building
AuthorShuenn-Yih Chang, Fen-Chyi Chan, Karen Chang
Keywordspushover analysis, short column effect, shear strength of masonry window spandrel, reinforced concrete
Abstract

It has been shown that the current formula for predicting the shear strength of masonry window spandrel may not be reliable. Thus, a series of cyclically loading tests were conducted for the reinforced concrete (RC) frames with different heights of masonry window spandrels and then a new formula is proposed to predict the shear strength. Herein, a further study is focused on the effect of using these new and old formulas in pushover analysis of old RC buildings with masonry window spandrel. The results reveal: (1) The use of the old formula for high masonry window spandrel may underestimate its shear strength. Hence, it might be damaged first and there is no short column failure. As a result, the performance-target ground acceleration (Ap ) of the building under analysis will be overestimated; (2) There is no significant difference in Ap value for using either new or old formula if the building has low masonry window spandrel; (3) Some masonry window spandrels look like high masonry window spandrels and it is expected that a short column failure will occur for the RC building under analysis. However, it shows no short column failure. This is because these masonry window spandrels are low masonry window spandrels because they may have a large width or their brick bond has a large critical failure angle. Since the old shear strength formula underestimates the shear strength of the high masonry window spandrels, it is likely to cause these high masonry window spandrels fail first without short column failure in the pushover analysis. Consequently, the Ap value is overestimated. Thus, buildings with insufficient seismic resistance cannot be detected early. Based on this, it is strongly recommended that the authority should revise the old shear strength formula for masonry window spandrel to improve the reliability of seismic evaluation of RC buildings.

TitleApplying Variational Autoencoder for Generating Artificial Earthquake Waveforms
AuthorYi-Xun Lin, Shieh-Kung Huang
Keywordsvariational autoencoder, feature learning, artificial earthquake waveforms
Abstract

As one of the major disasters on earth, earthquakes and their impacts cover a wide range of social, economic, and environmental aspects. However, forecasting earthquakes is currently impracticable, so many researchers have adopted various measures to cope with possible earthquake effects, such as earthquake early warning (EEW), structural health monitoring (SHM), earthquake-resistant structures, etc. This development allows us to respond to events and reduce impacts quickly. Although those advances are successful, they heavily rely on the availability and variety of earthquake data, which is often limited for large earthquakes or areas that are not earthquake-prone. Therefore, not much earthquake data can be used for structural analysis due to the deficiency of observation. In order to address this issue, this study introduces the variational autoencoder (VAE), a machine learning (ML) based approach. VAE is a generative model capable of automatically extracting the seismic features and reproducing the earthquake data. Moreover, it can generate artificial earthquake waveforms with diversity by using the extracted features, which provides a new way to synthesize waveforms. In this study, the 921 earthquake was first adopted, and a total of 293 waveforms were used for training. The preliminary results show that VAE is great while generating artificial earthquake waveforms. Subsequently, VAE is applied to the earthquake data from seven regions in Taiwan, and the final results verify the feasibility. As a result, VAE can provide merits for the development of structural and earthquake engineering, and the paper ends by suggesting future research.

TitleInvestigation of the Essential Parameters of the Bi-Axial Dynamic Testing System in the Tainan Laboratory
AuthorWang-Chuen Lin, Chung-Han Yu, Cho-Yen Yang, Chin-Cheng Lin, Yu-Fan Tseng, Shen-Kai Peng, Shiang-Jung Wang
Keywordsbi-axial dynamic testing system, friction performance, system identification, iteration methodology, direct force measurement system
Abstract

Large-scale testing machines with dynamic compression and shear testing capabilities play a crucial role in developing seismic isolation technology and testing full-scale seismic isolators. However, to date, relatively little research has been conducted on its dynamic performance verification and system parameter identification. Only a few studies have established the empirical model to predict the relationship between system friction and peak velocity of the Caltrans seismic response modification device (SRMD) test system in the University of California, San Diego (UCSD), based on the various characterization testing. To support academia and industry, the dynamic characteristics of the biaxial dynamic testing system (BATS) at the National Center for Research on Earthquake Engineering (NCREE) must be thoroughly investigated. When no specimens are installed, the system friction of BATS generated by the various sliding surfaces can be identified and mathematically characterized using the horizontal triangular reversed loading test results; then, the effective mass of BATS can be estimated using the horizontal sinusoidal reversal loading test results to solve the inertia force problem. Under vertical compression loading, it is assumed that the system friction of BATS and the shear force of the specimen are simply related to the applied total normal force (or vertical compression load) and horizontal excitation rate. An iteration methodology is proposed to identify and mathematically describe the dependency of the friction performance of BATS and the specimen on total normal forces (or vertical compression loads) and horizontal excitation rates by iterating the horizontal triangular and sinusoidal reversed loading test results. To simplify the tests, a lubricated flat sliding bearing is used as the specimen, subjected to horizontal triangular and sinusoidal reversed loading with a constant vertical compression load. The reliability of the proposed mathematical model for BATS and the feasibility of the proposed direct force measurement strategy are further demonstrated by comparing the calibrated force response with the directly measured response.

Vol.39/No.3 (153) (2024)

作者:

Vol.39/No.3 (153) (2024)

TitleDevelopment of Electromagnetic Variable Damping Seismic Isolation System
AuthorGing-Long Lin, Yi-Chun Huang, Ming-Bin Chang
Keywordselectromagnetic damping, variable damping, semi-active control, seismic isolation,
near-fault earthquake, shaking table test
AbstractThis study aims to develop an electromagnetic variable-damping seismic isolation system(EM-VDSIS), which incorporates a variable electromagnetic damper into a sliding isolation system. This allows the damping ratio of the EM-VDSIS to be a controllable parameter that can change in real-time according to a defined control law, enhancing the effectiveness of seismic isolation. The principle of the EM-VDSIS is first introduced in this study, and a mathematical model is constructed based on the mechanical behavior of the EM-VDSIS to derive its equations of motion and numerical simulation methods. Subsequently, numerical simulations are used to verify the variable damping function of the EM-VDSIS, with the potential to meet the seismic isolation requirements of both near-field and far-field ground motions. In terms of implementation, the EM-VDSIS (I) was first designed and manufactured, with a controllable resistance provided by an electronic load machine to alter the damping ratio of the isolation system. However, the electronic load machine fails to achieve ideal control of electromagnetic damping. Therefore, the EM-VDSIS (II) upgraded the power of the electromagnetic damper and used a mechanical variable resistor mechanism to provide controllable resistance values. The results of open-loop control with EM-VDSIS (II) using a shaking table demonstrate that the mechanical variable resistor mechanism can change the damping ratio of the isolation system in real-time according to control commands. Additionally, the theoretical analysis of the isolation system matches the experimental dynamic responses, confirming the accuracy of the theoretical model and related formulas in this study.
TitleSemi-Active Sloped Rolling-Type Isolators Based on Earthquake Early Warning Techniques
AuthorZi-Ting Chuang, Shieh-Kung Huang, Ting-Yu Hsu, Shiang-Jung Wang
Keywordsslope rolling-type seismic isolators, semi-active control, earthquake early warning, magnetorheological damper 
AbstractPassive rolling seismic isolators, once designed, manufactured, and installed on-site, have fixed parameters. They can effectively control the maximum acceleration response of the protected object within a certain range when subjected to typical far-field seismic waves, showing remarkable performance. However, when subjected to near-fault seismic waves with velocity pulses, their displacement response may exceed the limits, leading to collisions and damage to the protected object. Therefore, this study proposes the development of a semi-active rolling seismic isolator that integrates sloped rolling-type isolators (SRI) with magnetorheological dampers (MRDampers) and utilizes earthquake early warning technology. This research involves the development of a convolutional neural network (CNN) prediction model to estimate the peak ground velocity (PGV) based on the characteristics of the initial arriving wave. Additionally, control laws are established to determine the required voltage forthe MR Damper based on the predicted PGV. By measuring the initial wave arrival information, the system can predict the PGV using the CNN model and apply the control laws to obtain the required voltage for the MR Damper. This enables the adjusting the damping force of the rolling seismic isolator to prevent its displacement response from exceeding the limits during near-fault strong motions with velocity pulses. The feasibility of this proposed approach is verified through experimental tests of a SRI system. The experimental results demonstrate that this system effectively limits the displacement of SRI below the threshold value, validating the concept and feasibility of the proposed method.
Title Development and Performance Analysis of Seismic Isolation Bearings With Angled Viscous Damper
Author Chieh-Yu Liu, Chia-Ming Chang
Keywords seismic isolation, geometric nonlinearity, multiple performance objectives
Abstract Earthquakes pose a significant impact on machinery requiring high-precision manufacturing in advanced facilities. Meanwhile, severe earthquakes cause enormous economic losses and threaten lives. Base isolation is a popular method for controlling seismic impact, extensively employed to mitigate structural response and lessen seismic risk. However, certain studies suggest that base isolation could lead to excessive displacement during severe earthquakes. To enhance safety and functionality, supplemental damping is recommended to be integrated into the isolation system to mitigate large displacements. However, isolation parameters are typically designed for design-level earthquakes, resulting in increased absolute acceleration during small-to-moderate earthquakes and limited displacement control capacity during large earthquakes due to the lack of adaptability in damping. This study proposes an isolation system with geometrically nonlinear damping and first examines the dynamic characteristics. Subsequently, the relationship between seismic input and isolation responses in the frequency domain is analyzed using the averaging method. The seismic performance of the proposed system is then evaluated using earthquake records from the 2016 Kaohsiung Meinong earthquake to assess time-domain performance set at various initial inclining angles. Through a series of investigations, it is observed that the geometrically nonlinear damping configuration offers advantages by providing adaptive damping forces to isolation bearings and achieving multiple performance objectives across different earthquake magnitudes. Additionally, the proposed isolation system with a geometrically nonlinear viscous damper is experimentally validated to confirm the displacement-force relationship through shake table testing. In the experimental setup, the isolation system comprises three single-curvature grooves moving on fixed ball bearings alongside an angled linearly viscous damper. During the test, this isolation system is subjected to harmonic excitation on a uniaxial shake table to obtain force-displacement behaviors. The results demonstrate a close behavior between the simulated force displacement relationship and the experiment, thus indirectly carry out the multiple performance objectives of the proposed system against earthquakes.
Title Automatic Generation of an Active Structural Controller Using Direct Excitation With Machine Learning
Author Che-Wei Chou, Wei-Jung Wang, Pei-Ching Chen
Keywords direct excitation method, machine learning, autoregressive with exogenous inputs, optimal control, active mass damper, shake table testing
Abstract For active control structural systems, it is necessary to obtain a simplified numerical model of the structure through system identification. Controller design and analysis for vibration control are conducted based on this numerical model. Therefore, the representativeness and accuracy of the numerical model directly affect the performance of active structural control. Additionally, common structural controllers such as the linear-quadratic regulator (LQR) require the additional design of an observer to estimate the state of the structure for feedback control. However, both system identification and the design of structural controller and observer rely on the experience of engineers, thus increasing the practical application barrier of active structural control. In view of this, this study proposes a method for automatically generating structural controllers to mitigate seismic responses of structures. By using active control devices to generate small excitations on the structure and measuring the associated acceleration response, the inverse relationship between excitation force and structural acceleration response can be obtained through machine learning with a recurrent dynamic neural network called the autoregressive with exogenous inputs (ARX) model. Two structural models with 9-story, and 27-story configurations were assumed for numerical simulation. An active mass damper (AMD) was installed at the top of each structural model. Time history analyses were performed using 14 earthquake acceleration records to compare the control performance of the controller generated by the proposed method and LQR with optimized weighting matrices. Finally, a three-story shear building specimen was fabricated in the structural laboratory for shake table verification testing. An AMD driven by a servo motor was installed at the top floor. The experimental results show that the automatically-generated structural controller can effectively reduce the displacement and acceleration responses of the specimen and has similar structural control performance to structural controllers obtained through conventional design approaches.
TitlePerformance-Based Design and Assessment of Friction Dampers for Seismic Retrofit of a Reinforced-Concrete Structure
AuthorShih-Wei Yeh, Lyan-Ywan Lu, Fu-Pei Hsiao, Sheng-Qin Quo, Pin-Tsun Chen, Chia-Shang Chang Chien
Keywordsseismic retrofit, friction damper, performance-based design, seismic assessment, Bouc-Wen-Baber-Noori model, reinforced-concrete structure
AbstractThe use of dampers for seismic retrofit of a building structure is an advanced retrofitting technique, and many researchers have proposed various damper design methods. However, viscous and metallic-type dampers are more commonly used in practice, and studies on the design and assessment of friction dampers for seismic retrofit of structures are limited. To this end, this paper proposes a performance-based design method for friction dampers. The method, which combines the capacity-spectrum method with the codified damper design formulas, can improve the retrofitted building to a desired performance level. To validate the proposed performance-based design method, this paper employs the design procedure to determine the design parameters of a friction damper used in seismic retrofit of a seven-story reinforced concrete (RC) building. The seismic performance of the RC building with the friction damper is then assessed through the nonlinear time-history analysis using 11 spectrum-compatible ground motions. This paper adopts the Bouc-Wen-Baber-Noori model in the numerical model to accurately simulate the post-yield behavior of the RC columns in the first story. Under the DBE (design basis earthquake) intensity ground motions, the numerical results indicate an improvement in the seismic performance level of the RC building from the CP (collapse prevention) level to the LS (life safety) level, which meets the pre-set performance design objective. This validates the effectiveness of the proposed friction damper design method. Additionally, the numerical
simulation also demonstrates that the friction damper achieves a reduction rate of 40% on the peak inter story drift ratio of the first story and a reduction rate of 6% on the peak acceleration of the top floor. 
TitleDesign Passive Tuned Mass Damper With Optimal Target Response Using Static Output Feedback and Parameter Updating Iterative Method
AuthorYong-An Lai, Chi-Hung Chang, Xian-Zheng Hong
Keywordstuned mass damper (TMD), optimal passive control, optimal stiffness and damping coefficient, optimal mass, static output feedback, wind and seismic loads
AbstractThis study proposes a comprehensive passive tuned mass damper (TMD) optimization design method to minimize structural mean square responses. The optimization design problem for passive TMD is reformulated as an optimal control problem, specifically, the optimal gain matrix design problem in static output feedback (or direct output feedback). By solving for the optimal gain matrix, the optimal stiffness and damping coefficients, or optimal mass, of the passive tuned mass damper can be obtained. The proposed method is applicable to both single degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) structures, whether damped or undamped structures, and subjected to wind or seismic loads. Moreover, for different vibration reduction objectives, only different output matrices need to be selected, and the corresponding weighting matrices can be combined for the solving process, making it intuitive and straightforward. In the case of SDOF structures, numerical simulations validate that the optimal design parameters of the passive TMD obtained through this method are identical to the analytical solutions derived from random vibration theory, or closely approach to the approximate solutions, confirming the correctness and feasibility of the proposed design method. Additionally, using the proposed method, the optimal TMD frequency ratio and TMD damping ratio for minimizing the mean square response of velocity or absolute acceleration of SDOF structures under seismic forces are presented, providing reference for engineers in design. Finally, demonstrations are conducted with a passive TMD installed on a five-story MDOF structures and a ten-story ETABS structure, respectively, to design TMD optimal stiffness and damping coefficients, or optimal TMD mass. The results confirm that the proposed method is applicable to MDOF structural systems.

Vol.39/No.2 (152) (2024)

作者:

Vol.39/No.2 (152) (2024)

TitleExperimental Study on Reinforced Concrete Box Girder Strengthened in Shear With Carbon Fiber Reinforced Polymer (CFRP) Patches
AuthorHsiao-Hui Hung, Chi-Rung Jiang, Chun-Chung Chen, Fang-Yao Yeh, Kuo-Long Chen, Tsair-Yi Luo, Yi-Ting Lee, Kang-Yu Peng, Ming-Shing Wu, Chien-Hung Chen
KeywordsCFRP patch, shear strength, RC box girder
AbstractThe purpose of this research is to investigate the shear strengthening effect of carbon fiber reinforced polymer (CFRP) patched on reinforced concrete (RC) box girder with concrete shear cracks through specimen tests. Therefore, Two RC box girder specimens with insufficient shear strength were designed and fabricated, and the loading tests were carried out after strengthening of girders by CFRP was applied. The CFRP shear reinforcement was designed according to the guide specification published by American Association of State Highway and Transportation Officials (AASHTO). In order to simulate the state of RC box girder after shear cracks already occurred, one of the box girder specimens was loaded at first until shear cracks occurred and then strengthened with CFRP patches, while the other box girder specimen was directly strengthened with CFRP patches. Then, both strengthened specimens were respectively subjected to loading tests. Through the comparison of the loading test results of the specimens before and after strengthening with CFRP patches, the shear strengthening effect of the CFRP patch was confirmed. In addition, through the comparison of the test results of two strengthened specimens performed under different conditions, the benefits of shear strengthening with CFRP patch on RC box girder with existed damage can also be confirmed.
TitleShear Behavior of Prestressed Concrete Girders With High-Strength Transverse Reinforcement
AuthorYu-Chen Ou, Dwi Prasetya, Jhen-Wei Wu
Keywordsbridges, prestressed concrete, girder, shear strength, high-strength steel reinforcement, SD790
AbstractThis study investigated the influence of high-strength shear reinforcement on the shear behavior of prestressed concrete girders. Six I-girders, with a cross-sectional height of 600 mm and a total length of 5 m, were constructed and tested in the laboratory using two types of rebar as shear reinforcement: high-strength steel (SD790) and normal-strength steel (SD420W). The test parameters included the transverse reinforcement ratio and prestressing level. Monotonic-static loading was applied in all girders using two loading points. The test results indicated that a direct replacement of normal-strength shear reinforcement with high-strength shear reinforcement increased the shear capacity of the girder. The equivalent shear strength replacement of normalstrength shear reinforcement with high-strength shear reinforcement based on the specified yield strength showed a decrease in the ultimate shear strength. Thus, the use of fy = 790 MPa in shear design calculation is not recommended. In addition, the equivalent shear strength replacement based on a yield strength limit of fy = 600 MPa resulted in similar ultimate shear strengths between the specimen with the normal-strength shear reinforcement and that with the high-strength shear reinforcement. Furthermore, the experimental results were evaluated using the ACI 318-19 and AASHTO LRFD 2020 shear strength models. The findings showed that the yield strength limitation for shear strength design in the ACI 318 could be increased up to 600 MPa. Using 690 MPa as the yield strength limit with the AASHTO LRFD shear strength model still provided a high degree of conservatism.
TitleHybrid Simulation of a Steel Seven-Story Dual System With Measured Buckling-Induced First-Story Box Column Shortening in Subassemblage Tests
AuthorCheng-Wei Huang, Kung-Juin Wang, Chung-Che Chou, Hou-Kuan Shen, Claudio Sepulveda, Gilberto Mosqueda, Chia-Ming Uang
Keywordshybrid simulation, moderately ductile built up box column, buckling, forced control, displacement compatibility
AbstractThis paper presents a series of hybrid simulation (HS) conducted on full-scale steel beam-column connection subassemblages to study the seismic responses of a two-dimensional steel dual frame, considering first-story steel column shortening caused by local or global buckling during the seismic events. A seven-story two-bay dual frame system is composed of a special moment frame (SMF) and a buckling-restrained braced frame (BRBF) using built-up box columns. The experimental substructure consists of a full-scale interior column and beam cruciform subassemblage, including a moderately ductile first-story built-up box column and two I-shaped beams. Under combined axial and lateral loads, local buckling can occur near the column base, resulting in column shortening. The specimen is loaded through a four degree of freedom (DOF) mixed-mode control (three displacement- and one forcecontrol) actuation system that simplifies the laboratory loading conditions given the complex boundary conditions of the frame structure. To account for column shortening in the HS, a new approach is applied to enforce compatible displacements between the experiment and numerical model. With the column axial load in force control and column shortening, a set of fictitious equivalent forces is applied to columns in the numerical model to achieve compatible displacements. Shortening of two exterior columns in the model is simulated through finite element analysis using the computer program ABAQUS. The test results confirm that the proposed modeling and control methods could successfully integrate the information available in the laboratory and ABAQUS simulation into the HS, resulting in a more realistic frame response that captures the effect of column shortening in the analysis. The moderately ductile built-up box column is also verified to perform well in near-fault earthquake loadings.
TitleA Simplified Seismic Design Method for Steel-Timber Hybrid Buildings Considering Shear Force Modification
AuthorKai-Jun Huang, Pei-Ching Chen
Keywordssteel-timber hybrid building, structural dynamic interaction, design seismic force, incremental dynamic analysis
AbstractA steel-timber hybrid building consists of a conventional steel moment-resisting frame in its lower section, while the upper part is constructed with timber. In this study, a simplified method for structural design of steel-timber hybrid buildings has been proposed. It incorporates the dynamic interaction between the superstructure and the substructure into the existing Seismic Design Specifications and Commentary of Buildings in Taiwan. First a steel-timber hybrid building is simplified into a two degrees-of-freedom (2DOF) linear model. Parameter analysis is conducted to investigate the effects of the mass ratio and the frequency ratio of the superstructure to the substructure on the dynamic response of the 2DOF model. Accordingly, a seismic force modification factor can be defined, and the design seismic force for the upper timber structure can be calculated directly by using this modification factor. Meanwhile, the design seismic force for the lower steel structure can be determined individually by considering the base shear of the upper timber structure transmitted to the top of the lower steel structure. Four steel-timber hybrid buildings with different elevation have been designed based on the proposed method. OpenSees is used to build the nonlinear numerical model of the steel-timber hybrid buildings to perform nonlinear pushover analysis and incremental dynamic analysis (IDA). A total number of 44 earthquakes recommended in FEMA P695 are used for IDA. Based on FEMA P695 and relevant literature recommendations, the limit states of the steel-timber hybrid buildings can be assessed. The IDA results indicate that the Collapse Margin Ratios suggested in FEMA P695 is satisfied which demonstrates the applicability of the proposed simplified design method for design of steeltimber hybrid buildings in Taiwan.
TitleApplication and GUI Program Development of Empirical and Statistical Green’s Function Method in Earthquake Motion Simulation
AuthorWen-I Liao, Yuan-Ting Chen
Keywordsempirical Green’s function method, statistical Green’s function method, MATLAB, strong ground motion simulation
AbstractThis study primarily utilizes the empirical Green’s function method for seismic motion simulation graphical user interface (GUI) program development. The main theoretical concept involves the superposition of observed small earthquake event acceleration time histories to simulate the strong earthquake time history that occurs at the same site during a large earthquake. This method can effectively simulate acceleration time history of large earthquakes. To address the issue of the empirical Green’s function method being unable to simulate strong ground motion for locations without records of small earthquake events, this study proposes the statistical Green’s function method to simulate the strong ground motion acceleration time history at such sites. The main theory behind this approach is to use the recorded acceleration time histories of small earthquakes from surrounding monitoring stations to statistically analyze the relationship between ground acceleration amplitude spectra, phase spectra, and source-toreceiver distance. Subsequently, by calculating the results, the source-to-receiver distance for the desired simulation site can be used to calculate the amplitude spectra and phase spectra at that site. Then, by performing a Fourier inverse transform on the amplitude spectra and phase spectra, the acceleration time history of small earthquakes at that site can be obtained. Finally, this small earthquake event acceleration time history is used in place of actual small earthquake records in the empirical Green’s function method to simulate the strong ground motion at that site. Additionally, the developed GUI interface program includes functions for generating response spectrum-compatible acceleration time histories and amplifying acceleration time histories at specified period range.

Vol.39/No.1 (151) (2024)

作者:

Vol.39/No.1 (151) (2024)

Special Issue: The Sixteenth National Conference on Structural Engineering and The Sixth National Conference on Earthquake Engineering
Guest Editor:  Professor Chien-Kuo Chiu, Professor Pei-Ching Chen

TitleAnalysis and Validation of Isolation Systems With Multi-Functional Friction Damper
AuthorChia-Shang Chang Chien, Shan-Ru Chen, Mei-Ting Guo
Keywordsperformance test, conical friction pendulum isolators, multi-functional friction damper, seismic isolation system, shaking table test
AbstractIn recent years, earthquake disasters have gradually attracted global attention. Due to the unpredictability of earthquakes, whenever strong earthquakes occur, they often cause losses of people’s lives and property. In serious cases, they even affect the overall economic development of the country. The conical friction pendulum isolators (CFPI) is a seismic isolation system with the characteristic of extended structural period, which can improve the resonance effect produced by long-period velocity pulses of near-field seismic waves and fixed-period seismic isolation structures. Nevertheless, although the CFPI has an excellent seismic isolation effect in reducing acceleration of the superstructure, its base sliding displacement will amplify with the peak surface acceleration. The multi-functional friction dampers provide multi-stage activation mechanisms, and studies have shown that they have great shock absorption effects under different earthquake intensities when configured to structures. Therefore, the study in turn installed them in seismic base isolation layers to form a supplementary damping isolation system, improving the safety of the seismic isolator system under the effect of near-field seismic waves. According to the results of numerical simulation, the seismic isolation system with supplementary damping isolation has satisfactory vibration isolation effects regardless of affected by far- or near-field seismic waves. Additionally, to verify the theoretical formulas, the study also conducted the seismic performance test of the multifunctional supplementary damping system by shaking table and fit the results of the shaking table test and numerical simulation analysis. The results showed a fairly good fitting effect, which validates the accuracy of the theoretical formulas in this study.
TitleBridge Scour Depth Prediction Using Phase Space Attractor and Deep Learning
AuthorChang-Yi Lee, Zu-yi Chen, Yen-Yu Yang, Shu-Wei Chang, Chang-Wei Huang
Keywordsbridge scouring, deep learning, embedding theorem, convolutional neural network
AbstractCross-river bridges often suffer attacks of the foundation scour. Scour can significantly reduce the stiffness and strength of a bridge foundation, resulting in damage or even collapse of the bridge. To ensure the safety of a soured bridge, it is important to develop a real-time scour monitoring system to measure the scour depth of the bridge. In this study, a data-driven method is proposed to measure the scour depth using time series data from accelerometers. The concept of attractor in the phase space is used to describe the dynamic characteristics of scoured bridges. High-dimensional attractors for scoured bridges are reconstructed by a single sensor based on Takens’ embedding theorem. The reconstructed attractors are converted into two-dimensional grayscale images, which are then identified by the convolutional neural network (CNN) to obtain the scour depth. The accuracy of the proposed method is verified by the dynamic responses of bridges with different scour depths subjected to ambient vibrations from numerical simulations. The results demonstrate that the proposed data-driven method can determine the scour depth more accurately than conventional vibration-based methods in the case when the scour is not severe.
TitleStudy of Aspect Ratios for Base Isolated Buildings With Lead-Rubber Bearings
AuthorYi-Chian Wu, Chia-Ming Chang, Cho-Yen Yang
Keywords

base isolation, elastomeric bearing, stability, aspect ratios, nonlinear time history analysis

AbstractSeismic isolation shifts the fundamental frequency of structures away from the dominant frequencies of earthquakes by employing bearings with low horizontal stiffness, resulting in reduced responses of superstructures. However, an isolated building with a higher aspect ratio may introduce excessive overturning moments that can further cause tensile failure to bearings. Moreover, the elastomeric bearings, which are familiar and common in Taiwan, consist of laminated rubber layers with in-between steel shims, yielding complicated and coupled mechanics. Thus, the stability of the isolation bearings and the overall structural system should be concurrently considered. Such complicated behavior for an isolated building with elastomeric bearings as mentioned above may not be simulated or presented by conventional analysis in practical application. Therefore, this research studies the coupling effect for base isolated buildings with lead-rubber bearings, and then the relationship between aspect ratios and selected isolation bearings is constructed. In this research, the superstructure is simplified to be single-degreeof-freedom and mounted on an isolation system consisting of a rigid floor and two bearings. Each bearing is modeled by a simple mechanical model proposed by Koh and Kelly to consider the coupling effect. Based on the tension prevention of bearings, an aspect ratio criterion is also
derived and proposed. This aspect ratio criterion is further verified by time history analyses which consider various factors, such as the period of superstructure, isolation period, fault effect, and layout of bearings. As found in the parametric study, an isolated building designed by the proposed aspect ratio formula has a pretty low probability of tensile failures on bearings, as compared to the recommendation in the Japanese design code. Thus, the proposed aspect ratio criterion is more conservative and can be consequently a reference for engineers in the preliminary design phases of base isolated buildings with lead-rubber bearings.
TitleApplication of Hybrid Testing in a RC Structure With Seismic Retrofitting
AuthorFu-Pei Hsiao, Lyan-Ywan Lu, Hung Cheng, Bo-Tse Hsu, Shih-Wei Yeh
Keywordshybrid testing, RC structure, seismic retrofitting, open framework, OpenSees, OpenFresco
AbstractThe most realistic experimental method for evaluating the behavior of reinforced concrete (RC) structures under ground motion is a shaking table test (STT). However, the construction of RC shaking table test specimens is costly, and the shaking table equipment usually has limited
capabilities; therefore, conducting a large-scale structure test using a STT is difficult. To this end, this paper aims to develop a cost-effective hybrid testing (HT) technique that combines numerical simulation with large-scale structural experiments to test the nonlinear response of large-scale RC structures under strong ground motions. To make the result more applicable, this paper adopts the framework of an open-source hybrid testing technology. The technique used the OpenSees (Open System for Earthquake Engineering Simulation) as an open-source finite-element analysis software to build the RC nonlinear numerical substructure (NS) and the OpenFresco (Open source Framework for Experimental Setup and Control) as an open-source middle software to connect the physical substructure (PS) and a controller, which was connected to the hydraulic facility in Tainan Laboratory of the National Center for Research on Earthquake Engineering (NCREE). In the HT of this study, the target structure was a seven-story RC structure. The PS was taken to be the first-floor middle span retrofitted by an embedded RC portal frame, while the remaining structure, treated as the NS, was simulated by an OpenSees nonlinear numerical model with plastic hinges. The HT result demonstrates that the seismic responses of the retrofitted RC structure predicted by the HT experimental result match very well with the theoretical values predicted by a nonlinear finite-element model. The average difference between the experimental
and theoretical first-floor displacements is merely 5%. The nonlinear behavior contributed by the plastic hinge was also observed in the test. This study confirms that by cooperating with the existing hydraulic facility in Tainan Laboratory of the NCREE, the established open-framework HT technique with a nonlinear numerical substructure is a feasible means for the experimental study of a large-scale RC structure.
TitleNew Seismic Attenuation Technology: Resonator-Type Metamaterial
AuthorYuan-Yu Lo, Tung-Yu Wu, Shiang-Jung Wang
Keywordsseismic metamaterial, finite element analysis, local resonance, bandgap
AbstractSeismic metamaterials represent a novel earthquake-resistance technology. By manipulating wave propagation through artificial structures, they create regions where waves of specific frequencies cannot pass, preventing seismic waves of primary frequencies from reaching structures. Currently, seismic metamaterials face two major challenges: (1) the band gap frequency of the metamaterial is relatively higher than the primary frequency of earthquakes, and (2) there is a lack of metamaterials specifically designed for body waves. In light of this, our study designs a new low-frequency (0.35–1.5 Hz) seismic metamaterial unit targeting body waves based on duallayer tube-type resonators. Row and ordering analyses were conducted to determine the optimal arrangement of metamaterial units for reduction effects. The influence of the soil layer outside the metamaterial on its reduction effect was also investigated. Simulation results show that a group of four consecutive metamaterial units is the most economical arrangement, and the reduction effect of the metamaterial on SH waves was sensitive to the thickness of the soil layer. A subsequent ground response analysis demonstrated that when excited by actual seismic waves, the designed metamaterial units can reduce the spectral acceleration at the corresponding metamaterial band gap period to half, indicating the promising potential of the dual-layer tube-type resonators.

Vol.38/No.4 (150) (2023)

作者:

Vol.38/No.4 (150) (2023)

TitleStudy on analysis of a reinforced concrete portal frame retrofitted with an elliptically hollow steel frame infilled with rubber cylinders
AuthorChia-Chuan Hsu,Chia-Wei Hsu,Hsiao-Hui Hung, Kuang-Wu Chou,Chin-Kuo Su,Yu-Chi Sung
Keywordsnear-fault ground motion, seismic retrofit, RC frame, steel oval
hollow section, rubber, equivalent brace
AbstractThis study proposes an analysis procedure for engineers to apply a new method of retrofitting a reinforced concrete frame. This retrofitting method uses an elliptically hollow member, which is created with a steel frame infilled with rubber cylinders. This method enables rapid retrofitting construction and could help the retrofitted structure bear more loadings, resist strong earthquakes, and recenter, without sacrificing too much space for usage. Moreover, applying this method could effectively reduce structural damage caused by near-fault earthquakes. The proposed analysis procedure separates the three-dimensional finite element modeling of such a complex retrofitting member from the frame analysis that engineers need to perform for design. A retrofitting member alone gets detailed finite element modeling and pushover analysis to create a brace that can equivalently represent the retrofitting member in the frame analysis of the retrofitted RC frame. The comparison of the structural analysis result and the experiment result shows the proposed analysis procedure can prudently predict the behavior of a retrofitted RC frame with acceptable bias.
TitleFlexural Behavior of Steel Beam-to-Column Connections with Concrete as Fire Protection Material
AuthorCheng-Cheng Chen, Pin-Da Wu and Chen-Wei Fan
Keywordssteel structure, steel girder, beam-to-column connection, steel
reinforced concrete structure, fire protection layer
AbstractThe mechanical properties of steel are greatly affected by high temperature; thus, steel structure buildings need to have appropriate fire protection measures to prevent premature collapse of buildings in the event of fire. In some cases, steel structure buildings use concrete as fireproofing material. Although longitudinal and transverse steel bars are also provided as auxiliary reinforcements, but the strength that can be contributed by these steel bars is not considered in the strength calculation during design process. In engineering practice, this kind of structure is known as SC structure. In this study, five beamcolumn sub-assemblage was tested under cyclic loading to investigate the influence of SC beam structural details on beam strength, ductility, and crack development. The test results show that the use of reduced beam section beamtocolumn connection detailing is necessary since it can significantly increase the flexural ductility of the SC beams. The SC beams can develop the full composite action even though without using any shear stud. The use of isolation layer between beam flange and concrete in plastic hinge region is not necessary since it only slightly increase the plastic rotation capacity of the SC beams but causes larger crack in the concrete at the beam-to-column interface. The auxiliary longitudinal rebar is provided up to the face of box column and the use of 90° hooks are not recommended since it will cause additional cracks. The local buckling of the auxiliary longitudinal rebar can be effectively avoided when the distance between the rebar is less than ten times of its diameter.
TitleStudy on New Retrofit Methods for an Reinforced Concrete Beam with the Opening
AuthorChien-Kuo Chiu ,Min-Yuan Cheng, Yu-Chen Ou, Sheng-Huei Wang, Jie-Cih Jhou, Yin-Yi He
KeywordsReinforced concrete beam, plastic hinge, opening, retrofitting method, one-piece double-square hoop, inclined U-shape stirrup, strength, deformation capacity
AbstractTo prevent a reinforced concrete (RC) beam member from undergoing shear failure instead of flexural failure or flexure-shear failure under earthquakes, it is generally not recommended to make the opening within a region extending twice the beam depth from the face of the support column toward the central position of the span of the beam. However, in recent years, for actual requirements of the pipeline configuration, the problems of arranging the openings in the plastic hinge zone of an RC beam member have been already faced in the design and construction. Therefore, it is necessary to establish a set of design guidelines for the retrofit of the openings in the plastic hinge zone of an RC beam member. A total of nine specimens are tested in this study. The main test variables include: (1) opening location, (2) retrofitting methods of the openings. All specimens are subjected to cyclic lateral load. This work investigates the crack development and mechanical behavior of reinforced concrete beams with the circular openings, and provide the novel retrofitting methods with one-piece double-square hoops and inclined U-shape stirrups for the beams with circular openings. The experimental results are used to to verify the effectiveness of the proposed retrofitting methods. Additionally, based on the experimental results, this work also investigates the application of the design formulas that are recommended from AIJ-1999 and AIJ-2010 for an RC beam with the opening.
TitleShear Strength Design for Reinforced Concrete Shear Walls of Dual System
AuthorShyh-Jiann Hwang, Shao-Kai Huang, Pu-Wen Weng, Yu-Chen Ou, Ming-Huoy Huang
KeywordsDual system, Reinforced concrete, Shear strength design, Shear wall, Softened strut-and-tie model.
Abstract

Past earthquake reconnaissance already demonstrated that the reinforced concrete dual system, which consists of ductile moment resisting frames and shear walls, is one of the most effective earthquake resisting systems. A dual system can provide the 2nd line of defense when shear walls are coupled with frames. In seismic design, the 2nd line of defense is a secure protection against impulsive earthquakes. The shear walls of the dual system provide a continuity over height, which effectively prevent the story sway mechanism and provide uniform and reduced lateral drift resulting in a better damage control. The new building design code of Civil 401-110 requires the shear capacity design of the special shear wall. After the inclusion of the over-strength effect and the dynamic amplification factor, the shear strength demand can be doubled or even tripled, which leads to the shear walls with highly improbable thickness. This strict demand will hamper the application of the dual system in seismic design. This problem should be resolved.

A feasible solution to overcome this difficulty is to adopt the dual system with the shear walls designed by the strut-and-tie method. The structural walls of the dual system are equipped with substantial boundary members appearing as both beams and columns, which create a special shear force transferring mechanism within the framed squat walls. The framed squat walls possess very high shear resisting capacities, which can effectively reduce the thickness of shear walls, if well designed by the strut-and-tie method. The objective of this paper is to demonstrate the merits of the dual system and to promote its application in seismic design. The content of this paper includes the requirements of the new building design code, the softened strut-and-tie model, the shear strength design of framed squat walls of the dual system, design verification using Japanese shaking table tests, design suggestions for shear wall and the related case study.

TitleSeismic Performance of Reinforced Concrete Buildings with Viscoelastic Damping Wall under Shanchiao Fault Earthquakes
AuthorChung-Che Chou, Jian-Lin Lai, Kuan-Hua Chen, Shu-Hsien Chao
Keywordsviscoelastic damping wall, lever viscoelastic damping wall, Shanchiao fault, near-fault effect, nonlinear response time history analysis
AbstractViscoelastic damping wall (VEW) is a common velocity-dependent energydissipating device, which is used to reduce the lateral deformation of building frames in small earthquake or wind loadings. Its allowable deformation is smaller than the displacement-dependent energy-dissipating device so that VEW is unable to reduce the earthquake response under large earthquakes. The lever viscoelastic damping wall (LVEW) is a new velocity-dependent and displacement-dependent energy dissipating device, which is composed of viscoelastic and frictional damping in one single device. Under small or service level earthquakes, the LVEW could amplify its interstory drift by using a leverage mechanism so it can amplify the shear deformation and energy dissipation of a viscoelastic mechanism to reduce the frame response. Under large earthquakes, the stopper in the LVEW limits the deformation of viscoelastic damper, and activates frictional damping for energy dissipation. In this study, 8-story and 14-story reinforced concrete (RC) buildings with moment-resisting frames and shear walls were designed, representing a fundamental period of 1.0 second and 1.8 seconds. The frames were added with the traditional viscoelastic damping wall (VEW) and the leveraged viscoelastic damping wall (LVEW) for studying their seismic response. The building site was assumed to be located in Taipei Zone 1, close to the Shanchiao fault so the analysis was conducted by using acceleration time histories obtained based on the movement of Shanchiao fault. The work was focused on investigating the seismic response of RC frames with VEWs or LVEWs under Shanchiao fault ground motions.

Vol.38/No.3 (149) (2023)

作者:

Vol.38/No.3 (149) (2023)

Special Issue: The Sixteenth National Conference on Structural Engineering and The Sixth National Conference on Earthquake Engineering
Guest Editor:  Professor Chien-Kuo Chiu, Professor Pei-Ching Chen

TitleOptimal Design of Steel Panel Damper in MRF and Optimal Design Software
AuthorYe-Ying Jan, Keh-Chyuan Tsai
Keywords

steel panel damper, moment resisting frame, seismic design, optimization, software development, web service.

Abstract

Incorporating a steel panel damper (SPD) into a moment resisting frame (MRF) can increase the stiffness, strength, and energy dissipation ability of the MRF. This research improves the previous optimization algorithm by using Sequential Least Squares Programming (SLSQP) nonlinear programming algorithm. The chosen algorithm takes less than one second to complete the optimization.Time-efficient algorithm has helped the authors to implement an optimization software into a web service to users. This paper demonstrates the optimization of single-cruciform (SC) and double-cruciform (DC) types of SPDs-to-beam subassemblies. Each SC or DC type has “Basic Design (BD)” and “1.5 times stiffened Design (1.5KD)” In the BD, the optimal depth of SPD in SC type is around 700~1200mm, while around 500~800mm in DC type. The optimal beam depth of SC type is around 700~1100mm, while around 600~800mm in DC type. The DC type can save up to 300 mm less beam depth than the SC type for a strong SPD of 1500kN nominal shear strength. Comparing the BD with the 1.5KD for both the SC and DC type subassemblies, the top three largest increases of dimensions are web thickness of elastic joint (EJ), boundary beam depth and web thickness. Applying a gravity load effect ratio 𝜉, it’s found that one can consider a ratio of 𝜉 up to 0.15 to consider the gravity load effect in the optimization without much additional cost. In the case of an 8-meter boundary beam with an SPD location eccentricity of 0.2 times the beam span, the induced SPD axial force would exceed 0.15 times of compression yield capacity of the EJ segment. It is recommended that the eccentricity be limited to less than 0.2 times the beam span. In the cases when boundary beam sizes are specified first, it is found that the DC type designs are more efficient in increasing structural stiffness than the SC type designs for the SPD-MRFs with long-span beams.

TitleShaking table test of damped-outrigger structure incorporating friction dampers
AuthorMing-Ching Chen,Meng-Lin Chung, Pao-Chun Lin
Keywordsoutrigger, large-scale test, friction damper, numerical analysis, steel structure
Abstract

The main purpose of this study is to investigate the seismic performance of damped-outrigger system incorporating friction dampers through numerical analysis and shaking table tests. A 9 m tall steel structure specimen was designed by scaling down a 20-story benchmark model. The specimen was equally divided into ten floors and the outrigger beams together with the friction dampers can be installed in different floors. The normal force in the friction damper is adjustable so that its energy performance can be modified during the test. The seismic response of the specimen was evaluated by performing response spectral analysis (RSA) using the OpenSees numerical model. The equivalent damping ratio was included in the RSA in order to evaluate the energy dissipation resulted from the friction dampers. Based on the RSA results, the specimen configurations when outrigger locates at the sixth (6F), eighth (8F), and roof floors (RF) and when the normal force in the friction damper varies between 5 kN, 10 kN, and 20 kN were tested by imposing five different ground motions with the peak ground acceleration of 0.64g. Both the RSA and test results indicated that the maximum roof drift of the specimen was around 0.7% 0.4%, and 0.3% rad., when the outrigger locates at the RF, 8F, and 6F, respectively. The greater normal force applied in the friction damper generally result in a greater amount of energy dissipation and a smaller roof drift response. Based on the experimental and numerical results, the optimal design of the damped-outrigger system incorporating friction dampers are demonstrated in this study.

TitleThe Study on Prediction of Lateral Load Displacement Force and Behavior of High Strength Steel Fiber Reinforced Concrete Walls with Opening
AuthorChun-Yi Huang, Yi-Ching Ho, Binh Nguyen Doan, Wen-Cheng Liao
KeywordsNew RC, Shear wall with opening, Steel fiber reinforced concrete, Vertical wall segment, Discontinuous zones
Abstract

With the gradual increase in the demand for high-rise buildings, countries all over the world have developed high-strength concrete in order to reduce the size of components to reduce the weight of the structure and increase the usable space efficiently. The New RC project in Taiwan has also begun to promote the use of high-strength materials. It mainly conducts research on construction materials with concrete compressive strength (𝑓c′) above 70MPa and steel yield strength ( 𝑓y ) above 685MPa. However, as the compressive strength of the concrete material increases, its properties will gradually become brittle. Therefore, according to the current code, it is necessary to deploy a large amount of shear reinforcements in the stress interference area or the geometric discontinuity zone (D zone) such as beam-column joints. Stirrups are used to maintain the toughness and shear strength of the parts, but dense shear stirrups cause difficulties in reinforcement assembling during construction, and poor workability of concrete during casting, which results in the poor quality of concrete components. Adding steel fibers to high-strength concrete can delay brittle failure. Since the bridging effect between steel fibers can effectively inhibit the expansion of crack width, it can greatly reduce the configuration of transverse stirrups and solve construction problems.

According to the past experiments on the structural discontinuity area (D area), such as beam-column joints and deep beams, etc., the results show that the use of steel fibers in high-strength concrete can improve the toughness and shear strength of components, so the benefits of steel fiber reinforced concrete in structural discontinuities is known. This study carried out 4 high-strength steel fiber reinforced concrete shear wall experiments as the shear walls that are also members of the structural discontinuity area. The test parameters include the presence or absence of openings, the type of openings, the ratio of steel bars in the wall, the amount of stirrups in the boundary columns, and the configuration of reinforcement bars in the openings. Through the observation of the strength and deformation behavior of the test body and the development of cracks, the role played by steel fibers and the benefits of collocation with transverse reinforcement will be clarified in order to revise the prediction model and provide reference for future design.

TitleShaking Table Test of RC Columns Using High-Strength Flexural Reinforcement with Low Axial Load
AuthorChih-Hsuan Chin, Shun-Bang Yan ,Min-Yuan Cheng
Keywordsshaking table, drift, stiffness, high-strength reinforcement.
AbstractShaking table tests of reinforced concrete columns using high-strength flexural reinforcement and under low axial force (around 0.01 Ag fc’, where Ag and fc’ was the column gross section area and concrete cylinder strength, respectively) were investigated in this research. Two reinforced concrete frame specimens were tested. Each specimen consisted of a concrete base block, two columns with a clear-height-to-depth ratio greater than 12, and a top concrete block. The two specimens were first tested on the shaking table with 16 input ground motions, followed by static test on the strong floor. Specimen C1 used conventional strength longitudinal reinforcement (yield strength of 453 MPa) and specimen H1 used high-strength longitudinal reinforcement (yield strength of 716 MPa). The two specimens were designed to have the same flexural strength. Except for flexural reinforcement ratio and strength, all other design parameters were identical in the two specimens. Shaking table test results indicated the maximum drift of specimen H1 consistently larger than that of specimen C1 in all 16 table motions. The ratio of the maximum drift between the two specimens ranged from 1.3 to 2.4. Before yielding of the longitudinal reinforcement, lateral stiffness of the two specimens decreased as the maximum drift demand increased. Specimen H1 exhibited lower lateral stiffness and damping ratio. The inelastic responses indicated that the maximum strength of the two specimens were similar. Using Shimazaki and Sozen model provided an acceptable upper bound to estimate the maximum drift of specimen C1 but was not conservative for specimen H1. Static test results showed that both specimens sustained the maximum lateral force up to 10% drift ratio. Specimen C1 had severe concrete spalling at the column base. Specimen H1, in addition to severe concrete spalling at the column base, had two longitudinal reinforcement fracture during the 2nd cycle of 10% drift cycle. In general, specimen C1 had larger normalized energy absorption ability than that of specimen H1.
TitleSeismic demand acceleration of non-structural elements attached to building floors using nonlinear pushover analysis.
AuthorTsung-Chih Chiou, Lap-Loi Chung ,Yu-Chih Lai, Yi-Han Chao, Jae-Do Kang, Koichi Kajiwara
Keywordsnonlinear pushover analysis, TEASPA, capacity Spectron, demand acceleration of building floor
AbstractTaiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA) can provide a capacity spectron of an equivalent single degree of freedom system. The predicted structural response can be applied to determine seismic demand acceleration of non-structural elements attached to building floors. The study adopts the shaking table testing results of ten-story RC building by E-defense in 2015 to verify TEASPA’s predicted response of the building. The predicted capacity Spectron Sa is compared to the maximum acceleration of an equivalent SDOF under a real excitation history. The comparison will be discussed in this paper. Eventually, the study proposed a procedure on seismic demand acceleration for non-structural components attached to building floors.

Vol.38/No.2 (148) (2023)

作者:

第三十八卷第二期 (期別148) (112年)

TitleEffects of chamber geometry on electro-slagwelding failure
AuthorChun-Yao Yang, Keh-Chyuan Tsai
Keywordssteel box column, welded moment connection, electro-slag welding,SM570M-CHW steel, flared chamber, finite element model analysis, steel fracture prediction model.
Abstract“In order to transfer the steel beam moment, diaphragm plates are welded inside the box column at the beam flange elevations. Electro-slag welding (ESW) is commonly used to attach the diaphragms to the column. Due to the fabrication imperfection or the frame beam depth difference, eccentricity between beam flange and diaphragm elevations may exist. This situation could lead to brittle fracture initiated at the tip of initial slit near heat affected zone (HAZ). By changing the ESW chamber from a rectangular to a flared cross section, the fusion zone can be increased, but with a price of increasing the thermal input. Considering its advantage of high heat tolerance, SM570M-CHW high strength steel column is considered. This study firstly applied the MM-CVGM fracture prediction model to the tests of two ESW component specimens and seven full-scaled steel beam-to-box column (BC) subassembly specimens conducted in previous studies. Analytical results indicate that the difference between MM-CVGM prediction and test results is no more than one loading cycle, which is more accurate and conservative than the previous model. Additionally, four full-scale BC specimens were fabricated and tested to investigate the effects of chamber geometry and column flange thickness on ESW performance. Results show that the joint with a rectangular ESW failed at the 1.5% inter-story drift ratio (IDR) cycle, while the fractures were delayed until the 4% IDR when the ESW sections were changed to a large or small flared shape. The fracture criterion of the MM-CVGM model was modified in this study. The overall failure initiation is determined by the difference of the first crack initiation between the element and the group. Applying this conditional fracture criterion to the test results, the difference between the prediction and test results is no more than one loading cycle. Circumferential-notched tensile coupon tests were conducted to investigate the ductility difference between the base and weld metals. This study utilized representative volume element models in finite element model analyses. Results show that even the steels are from different sources, very similar failure response can be observed for the same grade of steel with a difference less than 10%. Analytical results indicate that the slope of damage evolution curve of HAZ in the SM570M-CHW base metal is 114% of ESW zone and 88% of CJP zone. Three regions have the same critical damage threshold and the difference is within 5%. When the base metal is changed to SN490C, the critical damage threshold of HAZ is reduced to 29%. Based on the research results, it is recommended that the ESW chamber be considered with a flared section when grade SM570M-CHW or SN490C steel is selected for the column in order to effectively delay the ESW crack initiation.”
TitleExperimental Study on the Effect of Crosstie Configuration on the Seismic Performance of Reinforced Concrete Beams
AuthorTai-Kuang Lee, Cheng-Cheng Chen
Keywordsreinforced concrete beams, crossties, seismic performance
Abstract“The current Building Code Requirements for Structural Concrete stipulates that in the plastic hinge zone of reinforced concrete beams, the longitudinal reinforcement at each corner and every other longitudinal reinforcement must be enclosed by the corner of the closed hoop or the hooks of crossties used as lateral support. However, in Taiwan reinforced concrete construction practice, the longitudinal reinforcement of RC beams is densely arranged, making construction difficult. In this study, four large-scale reinforced concrete beam specimens were planned and fabricated to conduct experiments to verify the effect of crosstie configuration on the seismic performance of reinforced concrete beams. The transverse reinforcement spacing of S6D and S4D specimens is 6 and 4 times the minimum beam longitudinal reinforcement diameter (D25) respectively, and the longitudinal reinforcements in the middle of the beam are not enclosed with crossties. The transverse reinforcement spacing of S6D-SHB S6D-SHT specimens is 6 times the minimum beam longitudinal reinforcement diameter (D25), the longitudinal reinforcement in the middle is enclosed with crossties, and the seismic hook engages the longitudinal reinforcement at the bottom and the top of the beam, respectively. The total confining force of the transverse reinforcement of S6D-SHB and S6D-SHT specimens (3-D10 reinforcements of SD 280W) is the same as that of S6D specimen (2-D10 reinforcements of SD 420W). It is found that: (1) With respect to the seismic performance in the negative direction (the longitudinal reinforcement at the top of the beam is under tension and the longitudinal reinforcement at the bottom is under compression), the S6D-SHB specimen is the best, the S6D-SHT specimen is second, and the S4D specimen is the third. S6D specimen is the worst. It is because that the middle vertical crosstie is configured in the S6D-SHB specimen and its seismic hook engages the longitudinal reinforcement at the bottom of the beam, delaying the effect of buckling of the longitudinal reinforcement at the bottom. (2) In the same transverse reinforcement total confining force, the ultimate drift angle and plastic rotation angle of the specimen with outer closed hoop and middle vertical crosstie and its seismic hook engaging the longitudinal reinforcement at the bottom of the beam are 5% and 12% higher than those of the specimen with outer closed hoop. It is recommended that during construction, within a range close to 2 times the depth of the beam at the RC beam-column connection, the bottom and side forms are not assembled in advance, and then after the crossties are assembled, the bottom and side forms are installed to solve the construction difficulties. (3) The ultimate drift angle and plastic rotation angle of the specimen with the transverse reinforcement spacing of 4 times the minimum beam longitudinal reinforcement diameter are equal to and 8% higher than those of the transverse reinforcement spacing of 6 times the minimum beam longitudinal reinforcement diameter. The transverse reinforcement spacing of RC beams has no significant effect on the seismic performance of RC beams. (4) Under the same total confining force of transverse reinforcements, when the outer closed hoops and the middle vertical crossties are configured and the
seismic hooks engage the longitudinal reinforcement at the bottom of the beam, the ultimate drift angle and plastic rotation angle of the specimen are 5% and 12% higher than those of the specimen with outer closed hoop. When the outer closed hoops and middle vertical crossties are configured and the seismic hooks engage the longitudinal reinforcements at the top of the beam, the ultimate drift angle and plastic rotation angle of the specimen are 2% and 4% higher than those of the specimen with outer closed hoops. This study found that in Section 15.4.3.3 of Building Code Requirements for Structural Concrete, for the plastic hinge zone of RC beams, the rule that the longitudinal reinforcement at each corner and every other longitudinal reinforcement must be enclosed by the corner of the closed hoop or the hooks of crossties used has no significant effect on the seismic performance of RC beams. (5) All four specimens have no significant attenuation in the positive lateral strength, and the negative lateral strength has significant attenuation. In addition, the pinching effect is obvious, and the ultimate drift angle can reach more than 4.0% rad. The required plastic rotation angle is 0.03 rad, so the seismic performance (plastic rotation angle) of all specimens basically does not meet the requirement of 3.0% rad for earthquake-resistant structures. It is speculated that the reason should be caused by flexural-shear failure. (6) For RC beam-column connections, the amount of longitudinal reinforcement at the top is generally slightly greater than the amount of longitudinal reinforcement at the bottom. Therefore, the main failure mode of the T-shaped beam should be the compression failure of the longitudinal reinforcement at the bottom, and the expansion of the closed hoops and crossties. The seismic hook of vertical crosstie engaging the longitudinal reinforcement at the bottom of the beam should also have the effect of delaying the compression and buckling of the longitudinal reinforcement at the bottom.”
TitleThe Shear Strength of Brick Wall of Window Spandrel
AuthorShuenn-Yih Chang , Hao-En Hung
KeywordsReinforced concrete frame, window spandrel, pushover analysis, failure theory of brick wall, shear strength of brick wall of window spandrel
AbstractThe previous experimental study of reinforced concrete frames infilled with brick wall of window spandrel revealed that the shear strength of the brick wall cannot be reliably predicted by the current computing formula. This might result in an unreliable result that is obtained from a pushover analysis. To overcome this difficulty, a series of cyclically loading tests of the eight reinforced concrete frames infilled with this type of brick walls were conducted and thus a new computing formula can be proposed for reliably predicting the shear strength of the brick wall of window spandrel. There are two drawbacks of the current computing formula for predicting the shear strength of brick wall of window spandrel: (1) the height of the infilled brick wall of window spandrel is not considered; and (2) the strength for the rupture of brick is not accounted by the current computing formula for high brick walls of window spandrel. Based on the failure modes of brick walls, the main contributions to shear strength include the horizontal friction force between the mortar and brick, the rupture of motor in vertical direction and the rupture of brick. These two drawbacks will disappear after considering the effect of the ratio of the height over width of brick walls and the rupture of brick for the high brick walls of window spandrel. After modelling the computing formula for predicting the shear strength, a regression analysis is conducted to determine the coefficients of the computing formula based on the test results of eight specimens. To affirm the feasibility of this formula, two test results that were reported in the literature are also compared. Although they adopt the Flemish bond for bricklaying and is different from the use of the English cross bond for the eight specimens for developing the new computing formula, the calculated results are still in good agreement with the test results.
TitleSeismic Testing and Design of Steel Panel Dampers
AuthorJin-Ting Lai, An-Chien Wu, Wei-Yang Li, Keh-Chyuan Tsai
Keywordsseismic stud column, steel panel damper, shear yielding, web stiffener, seismic design, cyclic loading test
AbstractThe 3-segment steel (shear) panel damper (SPD) can be viewed as a type of seismic stud column capable of dissipating energy through inelastic core (IC) shear deformations. In this study, the concept of capacity design is adopted to design a novel SPD with a continuous web plate and doubler plates in the elastic joint (EJ) segments. Considering the IC web buckling resisting stiffeners design guides for SPDs from Japan, and for shear links from the US, this research proposed a simplified design procedure for the IC stiffeners. Cyclic loading tests were conducted on two full-scale 3-segment SPDs with the same EJ doubler plates but different IC web stiffeners. Specimens are 2.6m high and 1.0m deep with a nominal shear strength of 1128kN. Test results show that both specimens had remarkably similar strength and hysteresis response until the 4% inter-story drift ratio was reached. The cumulative plastic deformation index was more than 400. After calibrating the finite element material model, parametric analysis results confirm that the properly deigned plug welds are required for the doubler plates in the EJs thereby delaying shear buckling. Using six additional analysis models for three different target shear deformations of 2%, 4% and 6% radians in the IC segments, it is demonstrated that AISC design specifications on shear link web stiffeners are more conservative and costly. Seismic design recommendations for the IC web stiffeners are concluded.
TitleSeismic performance and design of high-rise building incorporating buckling-restrained brace outrigger system
AuthorShou-June Tsai, Pao-Chun Lin
KeywordsHigh-rise structures, outrigger truss systems, buckling beam bracing, nonlinear response spectrum analysis, Nonlinear response yime history analysis
AbstractThe keen purpose of this study is to investigate the seismic performance of buildings equipped with damped-outrigger system using the buckling-restrained brace (BRB) system (BRB-outrigger) and to propose the optimal design recommendation for buildings with a different height. The numerical models with building heights of 72, 144, 216 and 288m, each contains two layers of BRB-outrigger and a 40m by 40m structural plan are analyzed using response spectral analysis (RSA) and nonlinear response history analysis (NLRHA) procedures. To get more closer to the actual reality, the member-by-member benchmark models are designed based on the seismic code requirement. In the response spectral analysis procedure, the equivalent damping ratio is computed in order to include the BRB’s inelastic response. For the main purpose of parametric study, a simplified model which will be using a Timoshenko beamcolumn element in order to capture shear-type to flexural-type lateral deformation for a lower to higher raising buildings are proposed. The dimensionless parameters that actually describe the relationships between the core structure stiffness, outrigger flexural stiffness, the axial stiffness of BRB and perimeter column in the parameter study are considered based on practical design and allowable structural sections. The optimization targets include the maximum roof drift, inter-story drift ratio, core structure base shear, core structure overturning moment and the BRB energy dissipation performance. Based on the analyzed result, the ranges of optimal design parameters vary in the different optimization targets and building heights. This study concludes with a design recommendation for building equipped with BRB-outrigger system with different building heights.

Vol.38/No.1 (147) (2023)

作者:

Vol.38/No.1 (147) (2023)

TitleDiscussion on Influence of Reinforced Concrete Beam Reinforcement Detail with Flush Outside Faces of Beams and Columns on Seismic Performance
AuthorTai-Kuang Lee, Cheng-Cheng Chen
Keywordsreinforced concrete beams, columns, flush outside faces of beams and columns, seismic performance
Abstract        In domestic buildings, the eccentric beam-column connections with the flush outside faces of beams and columns are common, and the ductility of RC beams with eccentric connections has not been experimentally verified. In view of such domestic engineering practice problems, this study plans four large-scale reinforced concrete beam specimens, and conducts experimental verification at the Materials Experiment Center of the Architecture and Building Research Institute, Ministry of the Interior, Taiwan. In this study, the R specimen (the main reinforcement of the beam is not offset, and the stirrups are of normal size), the RH/SU specimen (the main reinforcement of the beam is offset inward and the stirrups are reduced in size, the side is equipped with U-shaped transverse auxiliary reinforcement and two longitudinal auxiliary reinforcements are fixed), the RH specimen (beam main reinforcement is shifted inward and stirrups are reduced in size), and the SH/SLB specimen (beam main reinforcement is shifted inward and the stirrups are normal size, and two longitudinal auxiliary reinforcements are arranged at the corners of the stirrup) are fabricated. The research results show that: (1) All specimens (including 3 beam reinforcement details with flush outside faces) can develop beam end rotation angle of 4% radian, which can meet the seismic requirement of the specification. For the seismic performance in the negative direction, the RH/SU specimen is the best, the RH specimen is the second, the R specimen is the third, and the SH/SLB specimen is the worst. There is only one top and bottom main reinforcement of the SH/SLB specimen, which is surrounded by the corner of the stirrup. The longitudinal auxiliary reinforcement is arranged at the corner of the stirrup of the beam, which may have an adverse effect on the seismic performance of the RC beam. Therefore, it is recommended that the corners of the stirrups should be equipped with the main beam reinforcement. (2) The concrete cover on one side of the RH specimen is 85 mm, but the results of this study show that the lateral strength and seismic performance of the RH specimen are not inferior to the R specimen. It is acceptable to use the type of the RH specimen in practice. (3) The seismic performance of the RH/SU and RH specimens is better than that of the R specimen, but the RH specimen has wider crack width and the degree of spalling of the concrete cover is obviously more serious than that of the RH/SU specimen. Therefore, it is recommended to use the type of the RH/SU specimen in practice.
TitleAnalyses and designs of the connections jointing the new steel structure and the existing RC structure in NCREE’s office building extension
AuthorYu-Cheng Lin, Ming‐Chieh Chuang, Guan-Hong Lin, Pin-Pin Deng, Keh-Chyuan Tsai, Ching-Yi Tsai, An-Chien Wu, Jui-Liang Lin
Keywordsseismic design, strengthened connection, chemical anchor, finite element analysis, nonlinear response history analysis
Abstract        The existing six-story office building of the National Center for Research on Earthquake Engineering (NCREE) was extended to thirteen-story from October 2019 to November 2020. This study presents the analysis and design of the connections jointing the existing RC structure and the new steel service core from the second to seventh floors. A steel bracket, which is welded to the steel beam bottom flange and connected to the RC column using chemical anchors, was considered as the basic design of the connection to transfer the gravity shear from the steel beam. This shear connection detail could avoid the congested reinforcing bars inside the RC beam-to-column joint, however, three alternative designs using strengthened schemes are investigated in this study.
        Nonlinear response history analyses (NRHAs) using PISA3D program for the NCREE’s 13-story composite building were conducted in order to gain insight into the possible maximum seismic force and deformational demands on the connections. The features of dual mass centroids and dual rigid diaphragms for the second to seventh floors are incorporated into the PISA3D model. The 6DOF joint elements are utilized to represent the aforementioned bracketed connections on the interface. The axial push-pull stiffness of 100 tf/mm, computed from an Abaqus finite element model (FEM) analysis for the connections, is utilized for all the 6DOF joint elements. A total of sixteen sets of ground accelerations are utilized. NRHA results indicate that the maximum axial force and maximum in-plane rotation of the connection at the steel beam end are about 165 tf and 0.01 radian, respectively.
        The Abaqus FEM analyses were conducted for investigation of four connection types including the basic design and three improved designs. The FEM analysis results indicate that the beam bracket of the basic design exhibits obvious shear yielding. The uneven anchor bolt forces developed are very evident. The improved load-carry capacity and a more uniform bolt forces developed are found in the strengthened designs, such as the stiffened steel angles at the beam web and bracket with cover plate. In addition, an approximately 200×200 mm triangular region on the cover plate corner with a low stress demand is observed. Based on these connections’ FEM analysis results, this study confirms that the strengthened scheme adopts double-sided stiffened steel angles at the beam web, the straight bracket with the angular cuts on the cover plates is suitable. The strengthened scheme adopted in the project not only meets the seismic demands but also allows the inspections of the anchor bolts in the future, if necessary.
TitleMechanical Characteristics and Testing Device Development
of Headed Reinforcements for Uniaxial Tension Test
AuthorKer-Chun Lin, Chen-Yu Ou, Kai-Ning Chi, Sheng-Jhih Jhuang, Wen-I Liao
Keywordsheaded reinforcement, testing device to test single headed reinforcement in tension, slip of head part, elongation, tensile strength
Abstract        This paper mainly investigates mechanical characteristics of headed reinforcements in tension popular used in Taiwan and develops a fixture for testing to effectively shorten test time. A total of 41 headed reinforcement specimens that include four types of steel grade, SD 420W、SD 490W、SD 550W and SD 690, and three main types of head part, welded head, threaded head, grouted sleeve head. Test results related to head part slip showed that upper loading bounds of 0.7Py and 0.95Py to assess head part slip can acquire the same identified results those are qualified or not. The slip results for the various head parts indicated that the slip of welded head by friction was very limit. The slips of head part with the other heads from small to large in sequence were threaded head and grouted sleeve head. For the threaded heads of the headed reinforcements, all the slips were smaller than 0.2 mm. For the grouted sleeve heads of them, the slips of head part without a restraining-slip nut were more significant than 0.3 mm, but the slips of head part with a restraining-slip nut enable to be reduced under 0.3 mm as long as using proper fabricated process. Test results also presented that the maximum tensile strengths of each specimen exceeded its minimum specified ultimate strength and 1.25 times its minimum specified yield strength. The testing device developed in this study can install measure instruments quick and visually and get reliable measure results of head part slip. It also significantly reduces 78% of testing time per piece compared with the existed testing fixture. The load capacity of the fixture is for #12 reinforcement of SD 690.
TitleA Study on Nonlinear Dynamic Behavior of Reinforced Concrete Structures using Concentrated Plasticity Model
AuthorFu-Pei Hsiao, Lyan-Ywan Lu, Hsuan-Wen Huang, Hung Cheng
Keywordsconcentrated plasticity model, nonlinear RC, shaking table test, TEASDA, ASCE 41, ETABS, OpenSees, ModIMK
AbstractIn recent years, some strong earthquakes, including the 921 Chi-Chi Earthquake, the 0206 Meinong Earthquake, and the 0206 Hualien Earthquake, have caused the collapse of med-to-high rise reinforced concrete (RC) buildings, and resulted in heavy casualties and severe property losses. Because of this, it is crucial to perform accurate numerical simulation for the nonlinear structural response of med-to-high rise RC buildings. This paper establishes a 7-story RC frame model with different plastic hinges using the commercial software ETABS and the open-source finite element software OpenSees developed by the University of California at Berkeley, USA. The effect of different plastic hinge settings on nonlinear time history analysis of the RC building is explored in this study. Then, based on the shaking table test results of the 7-story RC building, it is judged which plastic hinge analysis results are closer to the experimental structural response. Furthermore, since ETABS is a commercial software, its extensibility is relatively limited. In other words, users cannot add newly developed materials and elements to ETABS, nor connect ETABS with the experimental control system to conduct experiments. Therefore, this paper proposes a method to convert an ETABS model to a OpenSees model. This method will enable researchers to establish the plastic hinges for an equivalent OpenSees model with the help of ETABS, and to take the openness advantage of OpenSees software for analysis.
TitleRegional evaluation of resilience based on FEMA P58: a case study for nonductile reinforced concrete frames in Los Angeles
AuthorPeng-Yu Chen, Ertugrul Taciroglu
KeywordsProbabilistic seismic assessment, regional evaluation, FEMA P58, nonductile reinforced concrete frames, incremental dynamic analysis, resilient index
Abstract        Seismic damage and loss assessment are highly related to buildings’ performance. However, the current nonlinear static analysis for performance evaluation is a deterministic methodology, where the uncertainties and variation of ground motion and numerical modeling cannot be considered. Furthermore, the outcome of engineering parameters is difficult to be utilized by decision-makers who may not have engineering backgrounds. While the world is toward developing resilient city, it is still not clear to structural engineers how to quantify the seismic resilience and evaluate it for large-scale regions. Hence, this research proposes a framework for regional resilience evaluation, which is based on probabilistic seismic assessment (i.e., FEMA P58) to incorporate incremental dynamic analysis and Monte Carlo simulation for damage and loss assessment. Moreover, the outcome of the regional evaluation is used to quantify the resilience index to illustrate the ability of a city for recovering from an earthquake. To demonstrate the application of the proposed framework, 1,452 nonductile reinforced concrete frames in Los Angeles are simulated by developing an automatic modeling program. Around 950,000 nonlinear time history analyses are conducted through a supercomputer, and the outcomes are used for loss estimation and resilience quantification. The results show that the mean loss ratio for nonductile frames under maximum-considered earthquake is 37.3%, and the resilience index indicates that the city needs at least 3 years to recover. While the presented work is a US-based case study, the authors hope the framework can be extended and localized for Taiwan’s development of resilient city.