Journal

Vol.36/No.2 (140) (2021)

作者:

Vol.36/No.2(140)(2021)

TitleLong-Span Buckling-Restrained Braces using Truss-Confined Restrainers
AuthorChun Chen, Yu-Cheng Lin, An-Chien Wu, Lu-An Chen, Keh-Chyuan Tsai
Keywordsbuckling-restrained brace, mega brace, truss-confined restrainer, flexural rigidity, shear rigidity, stability analysis
AbstractLong span buckling-restrained braces (BRBs) are getting popular for applications in seismic tall buildings. Recently, a novel type of BRB, namely the truss-confined BRB (TC-BRB) with a constant-depth truss built into the restrainerhas been investigated. The TC-BRB’s restrainer is constructed by attaching an additional truss system composed of several steel open-web truss frames outside the central steel casing in order to develop the overall restraining rigidity. Thus, the cross-sectionof the central steel casing and the weight of the infilled mortar in the TC-BRB can be significantly reduced in comparison with the conventional BRBs. The initial crookedness caused by the BRBs’ self-weight can also be reduced in the cases of long-span and large axial capacity BRB designs. This study investigates a new type of TC-BRB using a varying-depth truss system in the restrainers. This type of TC-BRB could save construction material and achieve the structural aesthetic more effectively than those using the constant-depth trusses. In this study, stability analytical model and seismic design procedures are developed and verified. Key mechanical properties including equivalent flexural rigidity and shear rigidity of the truss system are firstly presented. It is illustrated that the TC-BRBs’ elastic flexural buckling strength (Pcr) can be satisfactorily computed by incorporating Timoshenko shear effect into the classical stability theory. TC-BRBs’s buckling failure strength (Plim) can be further computed by considering the initial imperfections and inelastic material property.Abaqus finite element model (FEM) analysis results indicate that the proposed analytical model can satisfactorily predict the restrainers’ Pcr with errors less than 10%; and predict the TC-BRBs’ Pcr with errors less than 3%. In the first phase experiment, two 1/5-scale TC-BRB specimens, each of 6.3m long with the 1016-kN nominal yield strength anda constant- or varying-depth truss design, were tested in NCREE. Cyclic test results confirm that the Plim of the two TC-BRB specimens can be accurately predicted using the proposed analytical model with errors less than 6% when the effects of residual stresses in the truss members are considered. In the second phase experiment, two additional specimens were fabricated with significantly increased stability capacities. Cyclic test results show that the Plim of these two specimens can also be accurately predicted with the errors less than 7%, further confirm the reliability of the proposed analytical model. The TC-BRBs’ experimental performance also suggests that the proposed design procedures are generally conservative and practical. This study concludes with the recommendations, produres and examples on the seismic design of the proposed TC-BRBs using the constant- or varying-depth trussses.
TitleThe seismic performance of reinforced concrete columns using the lap-spliced crosstie with various axial load
AuthorTai-Kuang Lee, Cheng-Cheng Chen
Keywordslap-spliced crosstie, lap splice length, axial tension, RC columns, seismic performance
AbstractA lap-spliced crosstie consists of two J-shaped steel bars (rebars) that have a straight end and an end featuring a 180° hook. In this study, the cyclic lateral load test of four large-scale reinforced concrete columns with axial force proportional to the lateral force was conducted to discuss the seismic performance of RC columns with lap-spliced crossties and investigate the axial tension load effect. The research results are presented as follows: (a) The seismic performance of the specimens that adopted lap-spliced crossties is superior to that of the specimen using conventional crossties and worse than that of the specimen using crossties featuring a 180° hook on the two ends. (b) The ductility of RC columns comprising lap-spliced crossties, crossties featuring a 180° hook on the two ends and conventional crossties under axial tension is superior to that under axial compression. (c) For RC columns under axial compression, when the axial force ratio is less than 30%, lap-spliced crossties can be used instead of conventional crossties. (d) The inner columns of the building structure are subjected to large axial compression. When the columns are only subjected to axial compression during the earthquake, and the column axial force ratio is greater than 30%, the use of lap-spliced crossties can not only meet the ACI design requirements, but also facilitate the construction. (e) When the columns are subjected to repeated axial forces (axial compression and axial tension) during the earthquake, generally speaking, the column axial force ratio in this case is less than 30%. In this case, lap-spliced crossties can be used to replace conventional crossties.
TitleLoad demand assessment of liquid storage tank in water supply facilities
AuthorYuan-Tao Weng, Gee-Yu Liu, Wen-Cheng Shen, Min-Lang Lin, Lap-Loi Chung, Chao- Hsien Li
Keywordswater supply facilities, seismic evaluation, liquid storage tank
AbstractWhen carrying out the seismic evaluation and analysis procedure of the liquid storage tank, the static load, live load, soil load, fluid load, temperature load and seismic load must be estimated first. The seismic load can be divided into earthquake-induced fluid dynamic load, dynamic load of the soil and the seismic force induced by the self-weight of the structure. Firstly, the dynamic load of the fluid caused by the earthquake can be further divided into the fluid impulsive modal load, the fluid convective modal load, and the horizontal dynamic load caused by the vertical vibration of the fluid. Secondly, the soil dynamic load caused earthquakes can also be divided into active soil pressure and passive soil pressure. In addition, the vertical seismic force of the liquid storage tank and the lateral inertial force of the tank wall should also be considered. This study focuses on load demand assessment methods and seismic evaluation process for the common pool-like water tank structure in Taiwan to make the seismic evaluation and analysis procedures more feasible and reasonable.
TitleSeismic Performance of Crossing–fault Bridges
AuthorHsiao-Hui Hung, Lian-Gui He, Yi-Che Ho, Ching-Chiang Chuang, Chang-Wei Huang
KeywordsCrossing-fault bridge, nonlinear time history, multiple excitation, ground displacement input
AbstractThe influences of near-fault earthquakes are taken into account only by the magnification factors in the seismic design code for highway bridges. There are no related specifications about crossing-fault bridges in the design code. However, cross-fault bridges which are subjected to different ground motions at opposite sides of the fault line suffer more attacks in earthquakes. In this study, the seismic responses of cross-fault bridges are simulated with the multiple-excitation method and solved by nonlinear dynamic time history analyses. The displacement time history of each excitation is obtained by integrating the acceleration time history of a near-fault ground motion. The influences of the velocity impulse and residual displacements of near-fault earthquakes on the seismic responses of cross-fault bridges are discussed. In addition, the effects of the boundary conditions of the bridge deck and the angle between the bridge and fault line on the seismic responses of cross-fault bridges are also elaborated here. Numerical results demonstrate that the multiple-excitation simulation obtained larger local deformation and internal forces. On the other hand, the single-excitation simulation obtained larger absolute acceleration. Moreover, the ground displacements from integration are further divided into absolute displacements and relative displacements, which are assigned to the ground motions at opposite sides of the fault line. Numerical results show that there are no obvious differences on internal forces between these two displacement distributions. However, the absolute displacement generates larger member deformation. Moreover, the torsions at the bottom of bridge columns are magnified when the fault angle is 45°. Finally, the influences of different boundary conditions between bridge slabs and columns on the seismic responses are investigated. The seismic responses of rigid connections are similar to those of pin connections while the seismic responses of simply supported bridges have different characteristics
TitleProbabilistic Assessment of Seismic Performance and Collapse Risk for Irregularly Bridge
AuthorKuang-Yen Liu, Yi-Han Lu
KeywordsScouring Effect, Soil Spring, Group Pile Effect, Probabilistic Assessment Method, Collapse Risk Analysis, Incremental Dynamic Analysis, Static Pushover Analysis
AbstractThis study investigates the seismic performance and collapse risk of a group pile foundation irregularly bridge after scouring, which use API soil spring method to build a group pile foundation, four-span bridge models, and use probabilistic assessment to discuss the seismic performance due to different scouring places. This methodology was presented by previous researcher. For numerical analysis, this study uses SAP2000 to do incremental dynamic analysis (IDA). Afterward, based on the result, also establish fragility curve considering IO, LS, and CP performance. This study also uses pushover analysis to evaluate the seismic performance of bridge after scouring. The result shows the first yielding point for group pile will appear at the top of the pile. Second, Seismic performance for the bridge will have the greatest influence when scouring was taken place at the pier which has the biggest stiffness difference compare to its nearby pier. Last, pushover analysis for irregularly bridge may underestimate its reaction compare to nonlinear time history analysis. All in all, this simplified probabilistic procedure can be used as a reference for future seismic performance evaluation for bridges.

Vol.36/No.1 (139) (2021)

作者:

Vol.36/No.1 (139) (2021)

TitleStudy on a Post-earthquake Seismic Performance Evaluation Method for Low-rise RC buildings
AuthorChien-Kuo Chiu, Hsin-Fang Sung, Tsung-Chih Chiou
Keywordsresidual seismic capacity, damage level, reduction factor.
AbstractTo quantify the post-earthquake residual seismic capacity of reinforced concrete (RC) column members, the static-cyclic loading and dynamic loading experimental results obtained in previous work, and the “Pacific Earthquake Engineering Research Center Structural Performance Database (PEER)” are used to obtain reduction factors of strength, stiffness and energy dissipation. This work also applies the method of the modified nonlinear hinge and proposes the preliminary and detailed seismic performance assessment method for the residual seismic performance of earthquake-damaged RC buildings. In the case study, this work selects one actual earthquake-damaged building to display the post-earthquake assessment of seismic performance for a damaged RC building.
TitleConstruction cost analysis of school building seismic retrofit
AuthorYuan-Sen Yang,Yun-Ting Peng,Yu-Hsuan Huang, Tsung-Chih Chiou, Lap-Loi Chung, Shyh-Jiann Hwang
Keywordsschool building seismic retrofit, wing wall, RC jacketing, shear wall, construction cost
AbstractThe cases in the school building seismic retrofit have significant values for data analysis. The school building seismic retrofit data has been accumulated since 2009. More than 30,000 school building structures have been generally surveyed. More than 17,000 of them were preliminarily evaluated, and more than 10,000 of them which had significant risk of damage from earthquakes were evaluated. More than 6,000 of them have been retrofitted. As long as the analysis results are properly utilized, we will have more comprehensive understanding of construction cost, as well as potential for improving the administrative processes.
Based on the aforementioned database, this research analyzed the factors affecting the construction cost based on school locations, retrofit methods, and seismic capacity increment. In the statistics of the use of school building retrofit methods, it is found that wing walls, RC jacketing, and shear walls are the most commonly used retrofit methods. There are many factors that affect the project cost. This article studied the relationship between the retrofit cost and the above three factors through the data analysis.
TitleDesign of base-isolation systems subjected to pulse-like ground motions
AuthorNing-Kai Yang,Yin-Nan Huang,Hsun-Jen Liu, Shu-Hsien Chao
KeywordsNear-Fault Ground Motions; Base Isolation; Lead-Rubber Bearings; Non-Linear Response-History Analysis; GMPE
AbstractModernbuilding codes do not provide clearguidelineson the design of base-isolation systems against pulse-like ground motions, which may produce excessive displacement demand for isolators and endanger the systems. A procedureis proposed in this paper to address the impact of pulse-like ground motionson isolation systems. The procedure involves 1) the development of an “evaluation spectrum” using newly developed Taiwan ground motion prediction equations and a model for the ratio of spectral accelerations of pulse-like to non-pulse ground motions, and 2) selection and scaling of pulse-like records for nonlinear response-history analysis of the isolated building of interest. This paper presents an example of a 15-story steel special moment resisting frame isolated using lead-rubber bearings to demonstrate the proposed procedure.
TitleSeismic Isolation Retrofit and Foundation Replacement of Freeway Bridge
AuthorYin-Xuan Chen,Tien-Jen Hsiao,Ming-Shing Wu, Kang-Yu Peng, Guo-Long Chen
Keywordssystem of retrofit method, seismic isolator, foundation replacement method
AbstractTaiwan’s bridge seismic design specifications have evolved several version from 1987. In order to meet the seismic requirements under newest version specification. Freeway Bureau, MOTC has started existing bridge seismic capability evaluation and retrofitted after Chi-Chi Earthquake in 1999.
Because foundation retrofitting are expansive, we prefer to use “system retrofit method”. Conduct the feasibility studies on seismic isolation and damping devices. While the superstructure and pier are rigid connected, isolation bearing can’t install directly. An example of this is “Dong-Shan Bridge”. In this study, we explain the design considerations and methods of adding seismic isolation bearing to existing rigid piers. Furthermore, there are some cases where the spread foundation base will be scouring. An example of this is “Mei-Lin Bridge”. In order to increase earthquake and flood resistance at the same time. We use foundation replacement method to make spread foundation replace to pile foundation..
TitleSeismic Evaluation and Retrofit of the Isolated Bridge near Active Faults: Chianan Irrigation, Beigan No. 1 bridge
AuthorChih-Siou Gao, Tien-Jen Hsiao, Ming-Shing Wu,Kang-Yu Peng,Guo-Long Chen
KeywordsIsolated bridge, Near-fault effect, Seismic Evaluation and Retrofit, Fluid Viscous Damper
AbstractWith the development of the seismic isolation technology in Taiwan, Seismic isolation bearing has been used in some bridges to resist earthquakes. Since the construction of freeway NO.3 and the reconstruction of the bridge damaged by Chi-Chi earthquake,isolation technology has been used in three decade.MOTC also added a chapter “Seismic Isolation and Energy Dissipation Design” to “Specification for Seismic Design of Highways and Bridges” (2008).But the pulses in the near fault ground motion have a large ­ displacement response which is exceed the design displacementon isolated bridges due to their long period property.
Take “Chia-nan Irrigation Channel No.1 Bridge” for example. We studied the effects of earthquakes near and far fault region on seismic behavior of isolated bridge, and suggest the retrofit method. This research shows that resultant displacement of the existing seismic isolated bearings may exceed the design displacement under the far-fault earthquake due to the seismic force increased.Furthermore, the resultant displacement will be much larger under the near-fault earthquake when the period of the isolated bridge is closed to the pulse period.Finally, we install fluid viscous damper (FVD) to increase the overall bridge system damping and to reduce the displacement response of the seismic isolated bearing.
TitleRegression of Creep Prediction Formula of Concrete in Taiwan Basedon Database Analysisandits Applicationon Prestressed Concrete Bridge
AuthorWen-Cheng LIAO, Ho-Cheng HUANG, Jian-Jyun GAO , Ping-Hsun HUANG , Jumbo C.H. CHIANG
KeywordsDatabase, Long-term deformation, Creep,Prestressed concretebridge,Prestress loss
AbstractThis research integrates the test data of the past 40 years in Taiwan and establishes the “Shrinkage and Creep Database in Taiwan”. After comparing the domestic and foreign database, it is found that concrete in Taiwan has high cementitious material content, low water-cement ratio, and low aggregate stiffness, and it is not conservative if the foreign prediction model is directly applied. Therefore, Bažant’s Model B4 was selected as the basis of the prediction model, and the above parameters were localized and revised, and the prediction model of Taiwan ordinary concrete was proposed. In addition, this study extends the prediction model of ordinary concrete and revises the concrete with pozzolanic materials. Creep of concrete has a great influence on the long-term deformation of long-span prestressed bridges. In order to compare the difference between the domestic and foreign shrinkage and creep prediction models on the long-term deformation of the bridge, this study uses MIDAS Civil to establish a prestressed concrete bridge, and compares the analysis results between domestic and foreign prediction models. It is found that the foreign prediction models have seriously underestimated the deformation and prestress loss.

Vol.35/No.4 (138) (2020)

作者:

Vol.35/No.4 (138) (2020)

TitleIncreasing slip coefficient of bolted slip-critical joints using thermal sprayed coating technique
AuthorCheng-Chih Chen, Tsung-Cheng Hsieh, Cheng Chang, Sui-Wei Lee
KeywordsSlip-critical joint; thermal sprayed coating; slip coefficient
AbstractThe design philosophy of slip-critical joints is to utilize the friction force developed through the clamping force exerted by the pretension of the high-strength bolt. Thus, the slip-critical joint can have resistance in the direction of the bolt shear. This resistance is affected by the bolt clamping force and slip coefficient on the faying surface. The objective of this study is to increase the slip coefficient of bolted slip-critical joints by applying a thermal sprayed coating on faying surface. The specimens were designed to explore the effects of the coating material (aluminum or aluminum-magnesium alloy), coating thickness (150, 300 and 450 µm), and corrosion on the steel plate on the slip coefficient. The test results showed that exist of the rust increased the slip coefficient. In the case of slight corrosion, the blasted-cleaned faying surface resulted in an average slip coefficient of 0.74. The average slip coefficient was 0.88 for either the aluminum or aluminum-magnesium coatings. These slip coefficients are higher than the slip coefficient of 0.33 for unpainted clean mill scale specified in the design code. The coating material and thickness had insignificant effect on the slip coefficient. However, in the case of corrosion, the bolt pretension loss at slip was increased when the coating thickness was increased. The thermal sprayed coating of either aluminum or aluminum-magnesium on the faying surface can enhance the slip coefficient, increase the resistance of the slip-critical joint, and result in a smaller joint size and less high-strength bolts.
TitleStudy on the sliding shear design for reinforced concrete beams
AuthorYung-Chih Wang, Yu-Ting Kuo
KeywordsNew RC, plastic hinge, hinge relocation design, sliding shear, diagonal reinforcement.
AbstractThis study follow up the previous research on the hinge relocation design by using T-headed bars. The main conclusion is that the T-headed bars as extra reinforcement can successfully relocate the plastic hinge zone from the column face to a distance away from the face, however the final failure mode of sliding shear occurred. The similar sliding shear failure could be also found in the plastic hinge zone occurred at the traditional column face, or in the precast cold connection located in the plastic zone. Therefore, the main purpose of this study is to discuss how to design the diagonal reinforcement of the beam to prevent the occurrence of vertical sliding shear cracks for the general RC beam members subjected to the major earthquake.
This article mainly collected the tested beams subjected seismic loading to verify the design of the sliding shear specified in the NZS 3101-2006. It was concluded that the sectional shear stress , 0.25ඥf ୡᇱ(MPa), to check the potential sliding shear failure occurred in the plastic zone of RC beams is suitable for normal-span beams (a/d≧2.5). Therefore, if the potential vertical sliding shear cracks may be occurred in the plastic hinge zone of RC beams, the diagonal reinforcement shall be considered. Meanwhile, the cyclic testing performed comparing two types of beams between with and without diagonal bars repealed that the RC beams with diagonal bars can prevent the sliding shear cracks from occurring, and improve their seismic resistance. The design flow chart for prevention of sliding shear failure occurred in RC beams is finally suggested in the paper.
TitleEffect of geometric initial imperfections on seismic collapse capacity of steel special moment frames with deep columns
AuthorTing-Hao Chang ,Tung-Yu Wu
KeywordsGeometric initial imperfections; steel special moment frames; seismic collapse capacity
AbstractAlthough wide-flange (W-shape) steel members are known to have initial geometric imperfections (IGIs) due to fabrication and installation, the effect of IGIs on seismic behavior of steel special moment frames (SMFs) is still not well understood. To address this shortcoming, seismic collapse capacity of 4-story and 8-story prototype SMFs with various types of IGIs is computationally evaluated to quantify the effect of IGIs created by combining buckling shapes. The results show that even though IGIs can affect column buckling behavior and frame collapse mode under certain conditions, their effect on seismic collapse capacity is generally small and inconsistent. Their influence also greatly depends on the directions of applied IGIs and column buckling shapes and may be positive if the directions are misaligned. As a result, it is suggested that initial geometric imperfections need not be incorporated in high fidelity numerical models with high precision, which can generate their own IGIs when loaded.
TitleSeismic Performance and Backbone Curve Development of Steel Box Columns Considering Compactness Ratios, Axial Loads and Near-Fault Motions
AuthorChung-Che Chou, Guan-Wei Chen, Te-Hung Lin
KeywordsSteel built-up box column, High axial compression force, Lateralcyclic test, Cyclic backbone curve
AbstractThis paper presents the seismic evaluation of high-strength steel columns in a seven-story buckling-restrained braced frame under two sets of 11 far-field motions and 11 near-fault motions, representative of maximum considered earthquake (MCE) level. The proposed near-fault displacement protocol contains a large displacement pulse from -2% to +4% drift with several small displacement cycles and a residual drift of 2.5%.The AISC 341 (2016) has a more stringent width-to-thickness (b/t) limit for highly ductile hollow box columns (HBCs) than the AIJ (2010) or Taiwan Code (2010), resulting in significant thickness difference in design. For example, the b/t limits for a highly ductile box column member with a nominal yield strength, Fyn=420 MPa, and an over-strength factor, Ry=1.2, are 12.9 and 21 based on AISC 341 (2016) and Taiwan Code (2010), respectively.Moreover, the cyclic backbone curves based on ASCE 41 (2013) and NIST (2017) underestimate the post-buckling flexural strength of HBCs, particularlyin high axial compression force.The authors conducted cyclic tests of six full-scale, built-up HBCs using SM 570M steel with the actual yield strength of 460-530 MPa using standard and proposed loading protocols.The gathered test data, supported by more test data in this work, are analyzed by a multiple regression method to obtain empirical formulations for the backbone curves of box columns that can predict the maximum column moment, plastic rotation and post-yield hardening stiffness. The proposed formulation reasonably predicts the first-cycle envelope curves of built-up HBCs, significantly improving prediction results based on both ASCE 41 (2013) and NIST (2017).
TitleTheoretical and experimental study on vibration mitigation of off-shore wind-turbine using TMD
AuthorGing-Long Lin, Lyan-Ywan Lu, Kai-Ting Lei, Kuang-Yen Liu
Keywordsoffshore wind turbine, tuned mass damper, jacket-type structure, shaking table test, supporting structure, seismic vibration reduction, simplified model.
AbstractWind energy is clean and sustainable. Taiwan is establishing offshore wind farms using wind turbines in the Taiwan Strait. Since Taiwan is located in an earthquake active zone, in order to ensure the safety and reliability of offshore wind turbines under waves, wind and earthquakes, this study aims to investigate the suitability of using a tuned mass damper (TMD) to reduce the vibration of offshore wind turbine supporting structures. The TMD can be integrated as a part of the wind turbine structure, so it has less influence on the supporting structure of a wind turbine. In this study, based on the specifications of a 5-MW jacket-type offshore wind turbine suggested by the National Renewable Energy Research Center (NREL, USA), a 1/25 scaled-down test model and its corresponding TMD were fabricated and tested by a shaking table. Additionally, for numerical simulation, a simplified theoretical model for a jacket-type offshore wind turbine structure is proposed and its equation of motion was derived in this study. The proposed theoretical model was verified both in time domain and frequency domain using the result of the shaking table test. The experimental seismic responses of the offshore wind turbine model before and after the installation of TMD were compared, and the control performance of the TMD system for vibration mitigation of the wind turbine structure was evaluated in this study.
TitleSeismic Behavior of Bridge Columns with Partially Unbonded and Non-prestressed Steel Strands
AuthorYu-Chen Ou, Jhen-Wei Wu, Ade Yuniati Pratiwi
KeywordsColumns, near-fault ground motions, residual displacement, self-centering, post-yielding stiffness, cover concrete
AbstractThe impulse vibrations generated by near-fault earthquakes are likely to cause large residual displacements of RC bridge columns after the earthquake, which seriously endangers the safety and the serviceability of the bridge. A new type self-centering bridge column is developed in this research. The new column uses high-strength steel strands as the elastic element, which can reduce the large residual displacement of the bridge after the near-fault ground motions. In this study, four large-scale columns were tested using single-curvature cyclic loading, including a conventional column and three new self-centering bridge columns. The test parameters were the use of steel strands and different cover concrete thicknesses.
According to the post-yielding stiffness ratio and the actual thickness of the cover concrete from the test results, a linear regression formula for the ratio between the depth of the column to the thickness of the cover concrete and the post-yielding stiffness ratio was established. For the same specimen, the lower the thickness of the cover concrete on the compression side, the higher the post-yielding stiffness. The use of steel strands in the tension zone is important to maintain the post-yield stiffness of the bridge column. The maintenance of the strength in the compression zone is also an important factor. Because the steel strands in the tension zone remain elastic, the tension in the tension zone continues to increase after the conventional longitudinal steel bars yield. Due to force equilibrium of the section, the compression force has to increase accordingly. Test results show that the aforementioned increased compression force is likely to cause early crushing of the cover concrete of the compressive zone, which leads to the loss of the compressive zone and decrease the distance between the tension and compression resultant forces of the section. The test results of CSC3 show that when the ratio between the depth of the bridge column to the thickness of the cover concrete is 30, the average post-yield stiffness ratio can reach 5.7%.

Vol.35/No.3 (137) (2020)

作者:

Vol.35/No.3 (137) (2020)

TitleEffects of SM570M-CHW steel beam flange eccentricity and box-column flange thickness on electro-slag welding failure
AuthorYu-Jun Huang, You-Wei Hu, Chih-Kuang Chin, Ching-Yi Tsai, Chao-Hsien, Li,Sheng-Jhih Jhuang, Ker-Chun Lin, Keh-ChyuanTsai
Keywordssteel box column, SM570M-CHW steel, electro-slag welding, circumferentially notched tensile test, steel fracture prediction model, finite element analysis, overlapping distance of beam flange and diaphragm
AbstractSteel box columns are widely used in seismic steel building structures in Taiwan. In order to effectively transfer the beam-end moment to the column, diaphragm plates are welded inside the box column at the same elevations of the welded beam flanges. Electro-slag welding (ESW) procedure is common applied to attach the diaphragm plates to the column. Recently, the SM570M-CHW grade high strength steel is prevailingas it reduces the column sizes. In this study, four full-scaled welded SM570M-CHW steel beam-to-column (BC)joint specimens and eleven ESW component specimens were fabricated and tested. The key design parameters of these specimens include column flange thickness, beam flange eccentricity with respect to the diaphragm plate. This study investigates the applicability of stress modified critical strain and degraded significant plastic strain modelsin predicting the crack initiation fracture of the diaphragm-to-column ESW joint. The ESW component specimens were subjected to monotonic tensile loads, while the welded BC joint specimenswere subjected to cyclically increasing displacement to investigate the effects of beam flange eccentricity and column flange thickness on the ESW fractures. Test results show that when the ESW was subjected to monotonic tension only, it could fracture when the “overlapping distance of beam flange and diaphragm” (OD) was smaller or equal to zero. On the contrary, it remained intact even when the ODwas greater or equal to thickness of beam flange. Cyclic test results of the welded BC joints show that the connection with the 25mm thick column flange failed at the 3% inter-story drift (IDR) cycle, while the specimen with the 45mm column flange went through 5% IDR cycle without failure. The finite element model analysisresults show that when the column flange thickness increases from 25mm to 45mm, the stress concentrations are reduced and the crack tip opening displacement is decreased by 3 times. This study also carried out parametric study, focusing on the effects of the column flange thickness, the beam flange thickness and the OD on ESW fracture. Results show that increasing the column flange thickness, or the OD and decreasing the beam flange thickness reduce the stress concentration near ESW. In order to avoid the ESW fracture, the results of this study suggest that column flange thickness be equal to or larger than diaphragm or beam flange thickness; and the ODbe larger than one quarter of the diaphragm or beam flange thickness.
TitleDevelopment of Ground Motion Characteristics Prediction Module and its Application to the Control of Intelligent Isolation System
AuthorChia-En Hsiao, Kuang-Yi Lin, Tzu-Kang Lin, Lyan-Ywan Lu
KeywordsGround motion characteristics, Support vector machine, Structural control, Genetic algorithm, Fuzzy control.
AbstractIn recent years, researches on structural control combining earthquake early warning have been widely studied. In the field of seismic engineering, ground motions can be mainly classified into near-fault and far-field ground motions. While the ground motion characteristics have a great influence on control performance; however, the existing earthquake early warning system can only predict the peak ground acceleration, and the optimal control efficiency cannot be promptly achieved. Therefore, a prediction module for ground motion characteristics is proposed in this study. A database of near-fault ground motions and far-field ground motions is first collected, and the six p-wave features and the high-frequency energy accumulations of the ground dynamic spectrum are used to establish the ground motion characteristic prediction module by utilizing support vector machine. In order to develop the intelligent structural control system, the Leverage-type Stiffness Controllable Isolation System (LSCIS) is used as the structural control mechanism. The effective isolation stiffness of the LSCIS can be swiftly changed to control the dynamic response of the structure. The control parameters corresponding to different types of ground motion are optimized by genetic algorithm, and fuzzy control is adopted for the intelligent isolation system.
TitlePiezoelectric Tuned Mass Damper for Vertical Vibration Reduction and Energy Harvesting
AuthorYong-An Lai, Wei-Ling Chou, Lap-Loi Chung
Keywordstuned mass damper, piezoelectric material, energy harvesting, vertical vibration reduction, optimal design
AbstractIn recent years, the energy consumption has continually grown. However, due to climate change, the use of fossil fuel to generate electrical power forces to be reduced. Therefore, looking for environmental friendly energy sources is one of the current research priorities. Because of the development of civil engineering technology, the design and construction of structures turn into more economical. The weight of the bridge structure is becoming lighter, the appearance is accomplishing slender, and the structural period is therefore prolonged, making the bridge structure more susceptible to external forces such as pedestrian loads. In order to effectively reduce the vibration, civil engineers designed and installed Tuned Mass Damper (TMD). Through the tuning of the natural frequency of TMD to the structure, the vibration energy of the structure was absorbed and then dissipated by dashpot. However, this absorbed energy is a kind of green energy source to waste to be dissipated. In view of this, this article studies “Piezoelectric Tuned Mass Damper (Piezo-TMD)”, which uses piezoelectric materials to convert the mechanical vibration energy into electricity for energy harvesting. This research proposes the model and derives the equation of motion of the Piezo-TMD system. Different from the conventional TMD, Piezo-TMD has a circuit equation in addition to the mechanical equation, and these two equations are mutually coupled. The design goal of the Piezo-TMD in this paper is to maximize the average power for energy harvesting, and the numerical simulations are carried out with a pedestrian bridge structure. The simulation results show that the Piezo-TMD achieves the similar performance of vibration reduction as the conventional TMD and thus the vibration comfort requirement can be satisfied. Moreover, the vibration energy is further transferred to electricity for harvest to verify the feasibility of Piezo-TMD. In addition to tuning the mechanical natural frequency of the Piezo-TMD, the natural frequency of the circuit also needs to be tuned to the structure, so that the vibration energy of the structure can be effectively transferred to the circuit by using the resonance effect.
TitleDouble-curvature cyclic test of columns with five-spiral reinforcement and discreet computational shear strength model
AuthorYu-Chen Ou and Jhe-Yan Li
Keywordsshear strength; five-spiral reinforcement; columns; discreet computational shear strength model; cyclic test
AbstractFive-spiral reinforcement has been proved to have superior confinement capability to conventional rectilinear hoops. The objective of this research is to investigate the shear strength of five-spiral reinforcement. Large-scale columns with five-spiral reinforcement and control columns with conventional rectilinear reinforcement were tested in this research using double-curvature cyclic loading. Test results showed that with the same volume of reinforcement and similar reinforcement yield strength and concrete compressive strength, the shear strength of columns with five-spiral reinforcement was slightly less than that with conventional rectilinear reinforcement. However, the strength degradation after the peak strength for columns with five-spiral reinforcement was slower than that for columns with conventional rectilinear reinforcement. Under high axial load, the failure mode of columns with five-spiral reinforcement was fracture of spirals.In contrast, the failure mode of columns with conventional rectilinear reinforcement was the loosening of hook anchorage of the reinforcement. An improved discreet computational shear strength model is developed in this research and validated by the test results. The model can be conservatively used for estimating the shear strength of five-spiral reinforcement. Moreover, the model shows a conservatism for estimating the shear strength of five-spiral reinforcement similar tothat shown by the code shear strength equations for conventional rectilinear reinforcement.
TitleEffect of sensor deploymentonen on the accuracy of ambient vibration method incorporating mode shape functions for cable tension estimation
AuthorChien-Chou Chen, Wen-Hwa Wu, Shin-Yi Chen and Gwolong Lai
Keywordsambient vibration method, cable tension estimation, mode shape, effective vibration length, multiple synchronous measurements, sensor deployment
AbstractThe complicated boundary conditions resulted from the anchorage systems at both ends usually deteriorate the accuracy of the ambient method for cable tension estimation. Motivated by tackling such a problem, a novel method incorporating the mode shape functions was recently proposed by this research group. More specifically, the fitting for the sinusoidal components of mode shape functions was adopted to determine the effective vibration length for each mode such that the interference from the complicated boundary conditions can be eliminated. The success of this method is most critically decided by the accurate reproduction of the sinusoidal components of mode shape functions based on multiple synchronous measurements. The current paper first explains the basic concepts of this cable tension estimation method with the theoretically derived mode shape functions and frequency equations. The finite element models are further employed to evaluate the accuracy of this method and establish the guidelines for the preferred sensor deployment in measurement points and spacing with the consideration of practical measurement limitations. Finally, the applicability of the developed guidelines and the corresponding accuracy in tension estimation are verified by demonstrative laboratory experiments with a prestressed strand.

Vol.35/No.2 (136) (2020)

作者:

Vol.35/No.2 (136) (2020)

TitleStudy of the Influence of Creep and Shrinkage on Concrete-Filled Steel Tubular Columns and Design Suggestions
AuthorYa-Ju Yu, Jenn-ChuanChern, Wen-Cheng Liao
KeywordsCFT, creep, autogenous shrinkage, stress transfer,B4-TW creep and shrinkage prediction model
AbstractConcrete-filled steel tubular (CFT) columns show not only high strength and high ductility but also exhibit favorable seismic performance. The primary intent of concrete infill is to increase lateral stiffness of member and delay the local buckling of the steel tubular. Once concrete is subjected to load, development of concrete creep begins. In order to maintain the equilibrium of forces of CFT section, part of axial load of concrete will be transferred to steel tubular which leads to the growth of steel stress. Furthermore, high strength self-consolidating concrete (SCC) with low water-to-cement ratio intensifies the rise of steel stress in CFT columns on account of high autogenous shrinkage.A three-dimensional finite element model of CFT column, which takes account of the phenomenon of concrete creep and shrinkage, is developed to evaluate stress transfer between concrete and steel in ABAQUS. B4-TWcreep and shrinkage prediction model is also applied to reflect a characteristic of high amount of paste in concrete mix designs in Taiwan owing to the soft nature of coarse aggregates. The analysis results show that under the condition of initial steel stress of 0.6݂௬, the final steel stress of CFT column is probably not qualified according to “Design and Technique Specifications of Steel Structures for Buildings” owing to the long term deformation of infilled concrete whether the load is eccentric or not. In the extreme case of high concrete compressive strength of SCC and high diameter to thickness ratio, the steel stress significantly exceeds the original design value with 0.33݂௬. It is suggested that relevant specifications should be revised accordingly in Taiwan.
TitlePreliminary Seismic Performance Evaluation Method of RC Buildings Considering the Corrosion Effect of Reinforcement
AuthorChien-Kuo Chiu, Zong-Han Jhan, Yi-Jing Cai
KeywordsPreliminary seismic performance evaluation, Visual inspevtion, Deterioration de gree, Corroded reinforcement
AbstractThis research establishes a mechanical evaluation model of a corroded RC member and reduces its plastic hinge capacity on the basis of the past research project. In addition to do the comparison and verification with the relevant experiment data, this research collects the general information of the size of column members and reinforcement arrangement in a typical reinforced concrete building and street house for investigation on the reduction factor of strength. Restated, the reduction factor of strength can be used to consider effect of the deterioration or corrosion in the strength or seismic capacity for a corroded RC column member. Therefore, this work can provide a preliminary seismic performance evaluation method for a corroded RC building structure. Additionally, for a corroded column member, its reduction factor of strength is determined based on the deterioration degree, which can be judged based on the visual inspection of deterioration following the technical textbook of the durability assessment of deteriorating RC building structures. Finally, taking an existing school building for an example, TEASPA which is established by NCREE is used to evaluate the seismic performance considering the corrosion and verify the application of the proposed preliminary seismic performance evaluation method for a corroded RC building structure.
TitleVerification of Preliminary Seismic Evaluation Methods Using the Damaged Building Data of  2018 Hualien Earthquake
AuthorYi-Hsuan Tu and Tung Yeh
Keywordsearthquake damage, seismic evaluation, preliminary evaluation, reinforced concrete
AbstractData of thirteen buildings that damaged differently in the 2018 Hualien earthquake were collected and used to verify three preliminary seismic assessment methods. The three methods are all widely used in Taiwan, including the Preliminary Seismic Evalureliminary seismic evaluation of RC Buildings (PSERCB), the Preliminary Seismic Evaluation Method for Typical Building Structures of Primary and Secondary Schools by NCREE, and the Preliminary Seismic Evaluation Method for Typical Street-houses by NCREE. Comparison between the evaluation results and the observed damage states of the thirteen buildings showed that all three methods can identify the buildings that were heavily damaged. All three methods can sort the buildings in an approximately reasonable order. However, all three methods tended to give conservative results. The results from different methods for the same building were usually close. Only two buildings obtained different results between the NCREE method for street-houses and the other two methods. The PSERCB and the NCREE method for school buildings showed more conservative results than the NCREE method for street-houses in the two buildings.
TitleAn approach for probabilistic seismic performance assessment of buildings considering multiple performance levels
AuthorLyan-Ywan Lu, Fu-Pei Hsiao,Yu-Shi Tang,Yin-Nan Huang,Ching-Huei Chen, Kuan Feng Lee
Keywordsseismic performance assessment, probabilistic assessment, multiple performance levels, isolated building, performance design, incremental dynamic analysis, nonlinear time history analysis, plastic hinge
Abstract Most of current seismic assessment methods for buildings aim to evaluate the collapse risk of buildings, since the damage criteria of these methods are associated with the mechanism of building collapse. These methods may not be suitable for the assessment of functional facilities or seismic isolated buildings, whose performance objective is usually required to maintain their functionality after a strong earthquake. For this reason, this study proposes an approachfor probabilistic seismic assessment of buildings considering multiple performance levels. This approach adopts the performance levels defined by FEMA 356 and ASCE 41-13, namely, immediate occupancy (IO), life safety (LS) and collapse prevention (CP). For each performance level, both global and local damage criteria are defined according to FEMA 356 and ASCE 41-13, respectively. Based on these damage criteria together with the result of incremental dynamic analysis, the fragility curves for each performance level can be established for seismic assessment. For buildings with isolators, a performance level called isolation limit (IL) is also considered, in order to include safety of the isolation system in the assessment procedure. The damage criterion for IL performance level is defined as when the isolator drift exceeds the maximum total isolator displacement   given in the current isolation design code of Taiwan. For demonstration of the proposed assessment method, a 5-story old apartment building was consideredas an example. The building was retrofitted by using sliding isolators, and the seismic performance of the building before and after the implementation of isolation was evaluated using the proposed method and the results were compared, so that the benefit of retrofitting can be quantified. Theassessment results show that the retrofit with the isolators greatly reduces the damage probabilities of the building at all performance levels. This demonstrates that the proposed method can be applied to evaluate seismic performance of either fixed-based or isolated building with consideration of multiple performance levels.
TitleSeismic evaluation and strengthening methods for fire protection sprinkler piping systems in hospitals
AuthorYung-An Tsai, Fan-Ru Lin, Juin-Fu Chai, Kuo-Chun Chang
KeywordsFire protection sprinkler system, fragility curve, numerical analysis, simplified assessment, seismic strengthening design
Abstract

In recent years, due to the vigorous development of performance design concepts, the seismic capacity of critical building structures (such as hospitals and high-tech factories) has been improved, and the major disasters and economic losses caused by the earthquake have changed from structural to non-structural systems, which include piping systems.

This study takes the medium-scale hospital in Southern Taiwan as an example to discuss the effects of installing strengthened elements on sprinkler piping systems which recommended by NFPA13. First, this research uses detailed analysis results to construct the fragility curves, and compares the fragility curves between before- and after-strengthened systems. Second, according to the dynamic characteristics of the sprinkler piping system, the simplified assessment method of original system and strengthened system are proposed in this study. It provides engineers with an alternative, rapid and approximate judgment in the seismic performances of piping systems based on in-situ observations and generic floor response spectrum.

  

Vol.35/No.1 (135) (2020)

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Vol.35/No.1(135)(2020)

TitleExperimental study of reinforced concrete frame filled with high masonry window spandrel
AuthorShuenn-Yih Chang, Bo-Han Su, Tsui-Huang Wu, Kuang-Ming Lou
Keywordsreinforced concrete building, highmasonry window spandrel, seismic evaluation, pushover analysis
AbstractTaiwan areais characterized by high temperature and high humidity in summer. Hence, light and air are important in designing a building. To permit light and air to enter, windows are designed as large as possible. As a result, a window is located below the RC concrete beam, above the masonry window spandrel and between the two adjacent RC columns. This type of window is very unique in Taiwan area. Furthermore, to meet the requirement of concealment for storage room or restroom, high masonry window spandrels appear. Experimental studies of this type of masonry window spandrels are very rare. This might be due to the lack of large laboratories for conducting prototype tests. In the recent, a series of experimental studies on this type of window spandrels have been conducted by National Taipei University of Technology. In fact, the critical condition to experience a short-column failure has been identified and the cyclic-loading test results for the reinforced concrete frame filled with low masonry window spandrelshas been completed and published. In this work, two reinforced concrete frames filled with low masonry window spandrels were designed and fabricated. A cyclically loading test was performed for each test specimen. A formula for estimating the shear strength of a masonry window spandrel was proposed.
TitleThe Effectiveness of Combined Ties on the Confinement of Encased Concrete-Filled Box Columns
AuthorCheng-Cheng Chen, Pin-Da Wu, Yu-Lin Hsu
KeywordsEncased Concrete-Filled Box Columns, steel reinforced concrete column, concrete filled box column, SRC column, encased box column, combined tie
AbstractIn an encased concrete-filled box column, the concrete inside the steel box column is confined by the box column. However, the confinement of the concrete outside the box column (referred as outer concrete hereafter) need to be provided by the steel cage which is composed of main reinforcement and transverse reinforcement. Due to the existence of the steel box column, the traditional ties used in RC columns can not be implemented here. The use of so called combined tie was introduce to solve this problem. The confinement force was transferred from the first short tie bar to the box column and then to the second short tie bar located at the opposite side of the box column. In this article, six large scale (column size larger than 550×550) was tested under cyclic lateral loading to investigate the effectiveness of using the combined tie.The range of the width-to-thickness ratio of steel plate investigated was between 27 and 37, therefore the test result was applicable to column with width-to-thickness ratio less than 37. Some conclusion can be drawn based on the test results: (1) the combined tie can substitute the use of conventional tie bar, (2) the combined tie is effective in confining the outer concrete, and (3) the confinement effect contributed by combined tie can be determined using the cross section of the short tie bar.
TitleAxial Behavior and Test of Concrete-Filled Spiral Corrugated Steel Tubes Wrapped with Glass Fiber Reinforced Polymer
AuthorChung-Sheng Lee, Chung-Che Chou, Hao-Hsiang Tan, V-Liam Chin
KeywordsSteel Corrugated Tube, Glass Fiber Reinforced Polymer (GFRP), Confined Concrete, Axial Compression
AbstractThis paper presents the axial behavior of concrete cylinders confined by a novel composite tube. This composite tube consists of a spiral corrugated steel tube and Glass Fiber Reinforced Polymer (GFRP) shell. The spiral corrugated steel tube serves as a mold for wrapping GFRP shell. The concave area of spiral corrugated tube are filled with pre-preg fiber strands and epoxy resins to form an enhanced flat tube, and a multilayer GFRP jacket are wrapped around the enhanced steel tube. Thirty-six cylinder specimens were designed and tested under uniaxial compression. The test parameters included different types of confinement tube and cross section. This paper proposes an analytical method to predict the axial behavior of concrete filled GFRP-wrapped spiral corrugated tube, and a calculation method for the ratio of effective confined area to predict the axial behavior of hollow section specimens.
TitleBuckling-Restrained Brace Out-of-Plane StabilityAssessment Using Notional Load and Failure Mechanism Analysis with Multi-Case Study
AuthorI-Chia Ou, Li-Wei Chen, Ching-Yu Tsai, An-Chien Wu, Keh-Chyuan Tsai
Keywordsbuckling-restrained brace, flexural effect, out-of-plane stability, notional load, failure mechanism, second-order effects
AbstractWhen the out-of-plane (OOP) instability of the BRB and the end gusset connections occurs, the energy dissipation capability of the BRB will be significantly reduced. This study develops a simplified analytical model using the concept of the notional load and considering the flexural restrainer to assess the BRB global stability. Cyclic loading tests on six full-scale BRBs with different lengths, steel casing sizes, and gusset connection stiffness were conducted under various initial imperfections and OOP drifts to demonstrate the effectiveness of the proposed method. Test results indicate that the effects of the initial imperfection, OOP drift, and gusset edge stiffener on the BRB stability are reasonably captured. Moreover, parametric analyses were conducted using the proposed method on 581 BRB and connection cases, detail designed by the Brace-on-Demand cloud service, with varying frame span-to-height ratios and brace yield strengths. Analytical results suggest that the stability limit strength is reduced by 12% to 15% with the OOP drift ratio increased from 1% to 2%,while it is reduced by 5% to 20% without the presence of gusset edge stiffeners.It is concluded that the global stability is vulnerable to the OOP drift and adequately stiffening the gusset is recommended in BRB practices. It also shows that as long as the demand-to-capacity ratio (DCR) is less than 0.9 for steel casing stability calculated by using the practical evaluation method, the overall stability can be effectively conserved.

 

Vol.34/No.2 (134) (2019)

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Vol.34/No.2 (134) (2019)

 

TitleThe Strength of A New Type Connection for Rectangular Steel Tube Structures
AuthorCheng-Cheng Chen, Xiao-Fang Lin
Keywordssteel tube structure, steel tube construction
AbstractIn order to improve construction efficiency of low-rise buildings, a new type of connection for steel tube structures was developed.The new type connection for horizontal and vertical members are designated as BJ and CJ connections, respectively. Each of the new type connection is composed of two identical parts and assembled by two high strength bolts. The strength of this new type connection and the strength of the welds connecting the connection and steel tube were experimentally studied. A total of 51 successful tests were carried out and the following conclusions then are made accordinly: (1) The welds connecting the new type connection and the steel tube possess enough strength to transfer member forces from tubes to the connection. Therefore, it is suggested that the type and size of welds used in the test specimen should be used in the real structures. (2) The design shear strengths for BJ connection are proposed. (3) The design tensile strength and design compressive strength for CJ connection are also proposed.

 

TitleRevisions of CNS 560 Steel Bars Standard in 2018
AuthorKer-Chun Lin
Keywordsdeformed bars, threaded bars, relative projected area of rib, total elongation, uniform elongation
AbstractThis paper is intended to introduce and describe the major revisions of CNS 560 standard for steel bars using in reinforced concrete structures that include: (1) Adding two types of steel grade, SD 550W and SD 690. For the SD 550W steel, it is weldable and applicable for seismic members. For the SD 690 normal steel, a minimum ratio of 1.25 for the actual tensile-to-yield strength ratio is requested for seismic members, but welding is not allowed due to no limitations on its chemical compositions. (2) Creating a new type of threaded bars. The threaded bars are suitable for the grouted and threaded couplers. The requirements of deformation dimensions for the threaded bars are identical to those for the deformed bars, except that the rib pitch shall not exceed 0.5 times the diameter of steel bar. That is to get the same level of bond performance with the deformed bars. Therefore, the threaded bars can be regarded as one kind of the deformed bars. (3) Revising the method of bend test. For the bend test, based on the requirements of ASTM A615 or A706 standard, the steel bar shall not be restricted movement in its longitudinal direction to prevent from effects of the additional axial stress during the bend testing. In addition, it is recommended that the requirements of uniform elongation corresponding to actual tensile strength should be incorporated into the future version of CNS 560 standard as an assessment criterion of steel bar ductility. This conforms to the principles of performance-based design and provide the corresponding deformation demands of structural members.

 

TitleSeismic retrofit of existing high-rise RC buildings: full-scale test and nonlinear dynamic frame analysis using ETABS program
AuthorChung-Che Chou, Ping-Ting Chung, Ping Nian, V-Liam Chin, Yu-Fang Liu, Chen-Yang Ko, Chu-Chun Wang, Ching-Cheng Chen
Keywordshigh-rise RC building, shear retrofit, double K-braced steel frame, U-shaped steel plate, one-sided steel plate, seismic test, nonlinear static pushover analysis, nonlinear dynamic frame analysis
AbstractThis study evaluates the seismic retrofit of existing high-rise RC buildings in New Taipei City, Taiwan. The paper presents structural test results for verifying the design of member retrofit, nonlinear static pushover analysis and dynamic analysis of the high-rise RC building. The superstructure is mainly retrofitted by two methods. One way adopts a one-sided shear retrofit scheme for RC coupling beams, which are retrofitted with reinforced cement mortar or a steel side plate, respectively, from only one side of the beam to simulate the actual condition on site. The other way is to add a double K-type braced steel frame to increase the shear capacity of the RC frame. The RC beams in the basement are retrofitted with steel plates to increase the shear capacity. The full-scare members with shear retrofits were tested at the National Center of Research on Earthquake Engineering (NCREE) in 2016 and 2017. The test results meet the requirements of the strength and ductility based on Taiwan Seismic Specification and ACI 374.2R-13 (2013). In this study, a 24-story high-rise RC building was analyzed using the computer program, ETABS (2016). The nonlinear static pushover analysis and nonlinear dynamic analysis were conducted to evaluate the seismic performance of the building frame under a set of 2500 year-return period earthquakes, further verifying the seismic demands and technology of the seismic retrofit.

 

TitleStudy of Influences of Reduced Elastic Modulus of Concrete on Related Structural Design Codes in Taiwan
AuthorWei-Hsiu Hu, Wen-Cheng Liao
Keywordsmodulus of elasticity, design code for structural concrete in Taiwan
AbstractIn Taiwan, the prediction of Ec calculated by current design code is usually overestimated by 20% of that obtained by experimental results. The revision code of Ec = 12000 (f’c)^0.5 is 80% of current Ec = 15000 (f′c)^0.5 . The reduction of Ec would influent the size of beam and column, design value of base shear and other related structural design codes in Taiwan, such as “Design Code for Concrete Structures”, “Seismic Design Specifications and Commentary of Buildings” and “Allowable Stress Design Specifications and Commentary of Steel Structures”. The objectives of this research are to clarify those influences on these related structural design codes with reduced Ec and to comment and give suggestions to the engineering society. The results show that because of the reduction of Ec, the minimum thickness of reinforced concrete slab should increase by 7.7％ times, moment magnification factor would increase by 1.15 times (if slenderness ratio of column is 40), number of shear concrete stud would increase by 1.124 times (if compressive strength of concrete f′c < 360 kgf/cm^2). Structural design codes that directly or indirectly related to Ec should be modified accordingly because of the reduction of Ec.

 

TitlePreliminary discussions on analysis and design of floating houses
AuthorJhih-Rong Wang, Shih-Hsun Yin, Che-Hao Chang
Keywordsflood-proof house, floating house
AbstractThe main purpose of this paper is to introduce the concept and procedure needed to design a floating house which has flood-proof capability. The house was composed of steel box substructure and lightweight cold-form steel truss superstructure. Several columns were built up around the house, which can guide the house move up and down through a ring system connected to it. The house can float up along the columns due to buoyancy when flood waters invade and return back to the original location of the base when flood waters recede. Since the house has such a floating mechanism, it cannot be fixed to ground directly. Rubber Bearings were needed to pass vertical and horizontal loadings. In this paper, a real case study will be conducted for designing a floating house including a steel box structure preventing from invasion of flood waters, a lightweight truss structure forming the main house structure, rubber bearing pads transferring loads to foundation when the house is located on the ground, and guide columns limiting the horizontal movement of the house when it floats. The design and analysis procedure presented here may provide industry, government, and academic institutions in Taiwan with some design guidance and be beneficial to the development of floating houses.

Vol.34/No.1 (133) (2019)

作者:

Vol.34/No.1 (133) (2019)

Title Seismic design and analysis on boundary elements in bidirectional steel plate shear walls
Author Yi-Hsuan Yang, Tung Huang, Chao-Hsien Li, Ching-Yi Tsai, Keh-Chyuan Tsai
Keywords bi-directional steel plate shear walls, capacity design, axial, shear and flexural interaction, finite element model analysis, composite beam
Abstract The aim of this research is to propose a seismic design method for the corner vertical boundary elements (VBEs) in bidirectional steel plate shear walls (SPSWs) through a series of analytical and experimental studies. The VBEs at the intersection of bidirectional SPSWs must sustain the force demands induced from the two SPSWs simultaneously. The column axial force, bi-directional moments and shears are incorporated in the proposed procedures in computing the reduced column flexural capacities. The location of the bottom column flexural hinge is set at an elevation of 0.3 times the first story column height in order to achieve both performance and economy goals. In this paper, the effectiveness of the proposed design method is verified by four two-story L-shape bidirectional SPSW finite element model (FEM) analyses. The pushover analyses on the FEMs confirm that the flexural demands and the plastic hinge locations of the bottom corner VBEs can be predicted by the proposed method. This research also investigates the effectiveness of the composite action of the concrete slab and steel beam in the SPSW’s top boundary element using FEM analysis. Analysis results show that the composite action is not pronounced since the vertical downward panel forces are applied on the beam bottom flange.
Title Optimization of Steel Panel Dampers for Moment Resisting Frame Designs
Author Chu-Hung Chang, Keh-Chyuan Tsai
Keywords steel panel damper, seismic design, capacity design, shear buckling, optimization design, moment resisting frame
Abstract The proposed 3-segment steel panel damper (SPD) consists of one middle inelastic core (IC) and two end elastic joint (EJ) wide-flange sections. During earthquakes, the two EJs of the same cross-sectional property, are designed to remain elastic while the IC could undergo large inelastic shear deformation thereby dissipating seismic energy. In order to sustain a large deformation and delay the shear buckling of the IC web, stiffeners must be properly devised. In this study, optimization algorithm is adopted to proportion the SPDs and the boundary beams, and achieve the minimum steel weight design. It is assumed that two identical SPDs, one above and one below, are attached to the boundary beam mid-span. The MATLAB optimization toolbox combined the simulated annealing algorithm with the gradient-descent method is adopted to find the minimum steel weight design. The objective function is the total weight of the SPD, the boundary beam and the panel zone. The design variables are the sectional properties of the SPD, the boundary beam and the doubler plate thickness. Constraints include the capacity design of the SPD, boundary beam and panel zone, the stiffeners of the IC web, compact section and lateral torsional buckling limit state design requirements. The ”basic design”  is the lightest sections meeting all the constraints. The lateral stiffness of the two SPDs- to-boundary beam subassembly can be enhanced by either increasing the stiffness of the SPDs or the boundary beam. As examples, the optimization designs of increasing 50% more stiffness of the subassemblies as the new constraint were conducted also. While complying with the aforementioned constraints, the steel weight is increased by about 9% to achieve a 50% more stiffened design. The stiffness of the subassemblies are found enhanced most effectively by increasing the beam depths and web thicknesses.
TitleDevelopment and Seismic Tests of Steel Self-Centering Sandwiched Buckling-Restrained Braces (SC-SBRBs)
AuthorChung-Che Chou, Wen-Jing Tsai, Ping-Ting Chung
KeywordsSelf-centering sandwiched buckling-restrained brace (SC-SBRB), Cyclic test, Residual deformation, Energy dissipation
AbstractEarthquake-resisting frame systems that are designed based on current seismic provisions provide life safety performance in a large earthquake, but may have significant structural damage or residual drift due to energy dissipation in designated structural members. The damage leads to difficult or expensive repairs after a large earthquake. Therefore, development of a structural system that has both energy dissipation and self-centering properties in earthquakes is needed to improve the seismic performances of buildings. This paper presents a viable solution that was validated by multiple cyclic tests of an innovative brace, called a dual-core self-centering sandwiched buckling-restrained brace (SC-SBRB). The proposed brace combines the self-centering property of a dual-core self-centering brace (DC-SCB) and the energy dissipation of a sandwiched buckling-restrained brace (SBRB) together. The dual-core SC-SBRB is essentially a DC-SCB that is positioned concentrically with a SBRB to create both the self-centering and energy dissipation properties in either tension or compression. A 7860 mm-long dual-core SCSBRB, which uses ASTM A572 Gr. 50 steel as bracing members and ASTM A416 Grade 270 steel tendons as tensioning elements, was cyclically tested six times to validate its kinematics and cyclic performance. The test program demonstrated that the proposed dual-core SC-SBRB provides stable hysteretic responses with appreciable energy dissipation, self-centering behavior and large deformation capacity before low-cycle fatigue failure of the SBRB core.
Title Development and Application of a Variable Stiffness Isolation System Considering Ground Motion Characteristic
Author Zheng-Jia Liu, Chia-En Hsiao, Tzu-Kang Lin, Lyan-Ywan Lu
Keywords Stiffness-variable, energy of velocity, isolation system, semi-active control, minimum energy weighting
Abstract In recent years, the research of isolation and mitigation system has become more and more important. In the traditional isolation and mitigation system, the control effect may be reduced because of unknown earthquake types. To have the best effect of response reduction, the systems have to be adaptive with the earthquake type. To achieve that, an upgraded algorithm, Feed-forward Predictive Earthquake Energy Analysis (FPEEA), is proposed by considering the energy of earthquake velocity to have the optimal response. The new algorithm quickly evaluates the velocity energy to have the optimal weighting of minimum energy weighting (MEW). With the optimal weighting of the potential energy and the kinetic energy, the PFEEA can reduce the structural responses efficiently. In order to demonstrate the performance of the proposed algorithm, a single-degree-of-freedom structure is used as a benchmark in both numerical simulation and experimental verification. With predicting the optimal weighting in advance, the type of earthquake can be defined before the main shock of earthquake comes. The results have shown that the dynamic response of the structure can be effectively alleviated. Comparing to the structural responses of the MEW method, the performance of the proposed algorithm is similar to MEW or even better. The shaking table test also demonstrates the feasibility of applying the proposed algorithm in practical application.
Title A Life Cycle Consideration Structural Design Method for Concrete-Filled Steel Tubes Structure
Author Jenn-Chuan Chern, Zu-Liang Wu
Keywords creep, autogenous shrinkage, drying creep, CFT, structural design
Abstract The concrete-filled steel tubular structure has become a common structural type for buildings, which is matched with the use of self-compacting concrete, which is helpful for increasing the bearing capacity and stiffness of the high-rise building and increasing the effective use of the building area. However, the existing specifications and designs adopt the composite design method, and the structural design and the creep & Shrinkage behavior of the in-filled concrete and the interaction between concrete and steel tube are not fully considered in the existing structural design. This study introduces the time-dependent deformation characteristics of concrete and the necessity of applying local developed prediction formulas and proposes a design analysis method for concrete-filled steel tubular structures considering life cycle, and proposes design procedures and case studies to ensure the life expectancy in life cycle. During the period, the structural safety and serviceability of the structure can be ensured.

Vol.33/No.4 (132) (2018)

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Vol.33/No.4 (132) (2018)

Title Strongback systems for enhancing the seismic performance of buildings
Author Meng-Kwee Kek, Jui-Liang Lin, Keh-Chyuan Tsai
Keywords inter-story drift ratio, generalized building model, strongback, nonlinear response history analysis
Abstract In order to reduce the variations of peak inter-story drifts occurred in earthquakes along the building height, this research conducts the parametric study of the buildings with strongback systems through simplified numerical models. The generalized building model (GBM) and generalized building model with strongback (GBMSB) are employed as the simplified numerical models in the parametric study. This study investigated 3, 6, 9 and 20-story buildings.The peak inter-story drift ratios along the building height are computed by using the response spectrum analysis method, in which the peak modal responses are combined according to the SRSS method. The optimization objective is to minimize the standard deviation of the peak inter-story drift ratios. The optimal stiffness distribution of a strongback is thus obtained.The results of parametric study show that when a pure shear-type strongback, whose first story is stiffened and its story stiffness decreases linearly along the height, the standard deviation of inter-story drifts is minimized. The effectiveness of the proposed method is verified by investigating one 9-story steel building and one 3-story reinforced concrete (RC) building.The 9-story steel moment resisting frame, designated as SAC9, was a prototype building located in Los Angeles adopted in SAC steel research project. In addition, the 3-story RC building, designated as T3,was tested using shaking table at Tainan Laboratory of National Center for Research on Earthquake Engineering. The optimal designs of SAC9 and T3 with the strongbacks are designated as SAC9-SB and T3-SB, respectively. Nonlinear response history analyses (NRHA) of SAC9, T3, SAC9-SB, T3-SB models and the others with different properties of strongback systems were conducted using PISD3D program. The NRHA result shows that SAC9-SB and T3-SB have smaller standard deviations than those using other strongback properties. The analysis results confirm the effectiveness of the proposed method in proportioning the strongback for buildings.
Title Fracture Tests and Finite Element Analysis of Diaphragm Connection in Steel Beam-to-Box Column Joints
Author Chung-Che Wu, Chao-Hsien Li, Ching-Yi Tsai, Ker-Chun Lin, Sheng-Jhih Jhuang, Keh-Chyuan Tsai
Keywords steel box column, electro-slag welding, heat affected zone, fracture prediction model, steel beam-to-box column connection, finite element model analysis, circumferential notched tensile test, ultrasonic test
Abstract Steel box columns are widely used in steel building structures in Taiwan due to the strong axes in two directions. In order to transfer the beam end moment to column, diaphragm plates of the same thickness and elevations as beam flanges are usually welded inside box column. Electro-slag welding (ESW) process is typically used in attaching the diaphragms to column flanges. This ESW process has been widely used in steel beam-to-box column joints in Taiwan because of its’ convenience and efficiency. However, ESW may increase the hardness of the welds and heat affected zones (HAZs), while reduce the Charpy-V Notch (CVN) strength in HAZ. This situation could cause the diaphragm to column flange weld to suffer premature fracture before a large plastic rotation is developed in beam-to-box column joints. In order to quantify the critical eccentricity and the effectiveness of predicting the fractures, this study utilizes the fracture prediction model and finite element model (FEM) analysis to correlate the test results. In this study, three beam-to-box column connection subassembly tests have been conducted with a different loading protocol or the shape of ESW chamber. Test results show that the fracture instances can be predicted based on the cumulative plastic deformation in the HAZs. Tests confirm that the possible fracture of the diaphragm to column flange welds can be mitigated by enlarging the chamber of the ESW. When the fracture prediction model is applied, the material parameters were firstly established from the Circumferential Notched Tensile (CNT) tests and FEM analysis. Subsequently, these parameters were used to predict the fractures observed in the ESW component tests and beam-to-box column connection subassembly tests. The fracture locations and instances can be reasonably well predicted by a suitable FEM model analysis. Thus, the effectiveness of CNT and the fracture model are confirmed. Analytical results also show fracture instances and locations are sensitive to the relative locations of the ESW and the beam flange. Thus, the importance of ultrasonic test in assuring the quality of the ESW is evident.
Title Life-cycle Cost Assessment Method Development for Steel Bridges Considering the Effect of the Renewal Periods of Coating Systems
Author C. K. Chiu, C. C. Chen, M. Y. Chen
Keywords steel bridge, deterioration rate, life-cycle maintenance cost, anti-corrosion coating system
Abstract In the maintenance stage of steel bridges, the costs can be divided into the regular maintenance cost and anti-corrosion coating cost. For the regular maintenance cost, this work adopts the Bayesian updating to determine the deterioration rate of each component or member. Additionally, based on the minimal regular maintenance cost, the corresponding maintenance period can be obtained. In order to quantify the renewal cost of the anti-corrosion coating system, this work conducts the accelerated-weathering test and site exposure test for the anti-corrosion coating materials. In addition to the testing results, the past investigations on the consuming rates of the specified coating materials for steel bridges are referred to determine the renewal periods of the anti-corrosion coating system. Finally, an assessment method of the life-cycle cost (LCC) of steel bridges is developed to investigate effect of the renewal period of the anti-corrosion coating system on the LCCs for 26 steel bridges located in a special municipality in Taiwan.
Title Capacity-Based Inelastic Displacement Spectra for Seismic Design and Evaluation of Reinforced Concrete Bridges
Author Ping-Hsiung Wang, Kuo-Chun Chang, Yu-Chen Ou
Keywords spectrum, inelastic displacement ratio, damage index, smooth hysteretic model, far-field earthquake, near-fault earthquake, seismic design and evaluation, RC bridges
Abstract Capacity-based inelastic displacement spectra that comprised an inelastic displacement (CR) spectrum and a corresponding damage state (DI) spectrum was proposed in this study to aid seismic evaluation and design of reinforced concrete (RC) bridges. Nonlinear time history analyses of SDOF systems were conducted using a versatile smooth hysteretic model that accounted for the influences of various column design parameters when subjected to far-field and near-fault ground motions. It was proved that the Park and Ang’s damage index not only can be used to accurately predict the onset of strength deterioration, but also can be a good indicator for assessing the actual visible damage condition of column regardless of its loading history, providing a better insight into the seismic performance of bridges. The computed spectra show that the CR for far-field ground motions approximately conforms to the equal displacement rule for structural period (Tn) larger than around 0.8 seconds, but that for near-fault ground motions departs from the rule in the whole spectral regions. Moreover, the near-fault ground motions would lead to significantly greater CR and DI than far-field ground motions and most of the design scenarios investigated in this research cannot survive the near-fault ground motions when relative strength ratio R = 5.0. Based on the computed spectra, CR and DI formulae are presented as a function of Tn, R, and various design parameters for far-field and near-fault ground motions. Finally, application of the proposed spectra to the performance-based seismic design and evaluation of RC bridge was presented using DI as the performance objective.
Title Estimation of Design Pressure Coefficient Based on Extreme Value Analysis Theory
Author Yuan-Lung Lo, Michael Kasperski
Keywords Design wind speed, Extreme value distribution, Pressure coefficient, Optimal design fractile
Abstract To determine a proper design wind load relies on correct evaluations on design wind speed and design wind pressure coefficient. The evaluation on design wind speed requires the understanding of local meteorological information accumulated for a long-term period and the knowledge of extreme value analysis; wind pressure coefficient of the target structure can be obtained via properly arranged wind tunnel test fulfilling the satisfactory demand of all non-dimensional aerodynamic parameters. By satisfying the target exceedance probability of failure of a target building, convolution process of probability densities of design wind speed and pressure coefficients is carried out and then the optimal design pressure coefficient can be found through iterative calculation. This study intends to apply local meteorological information in Taiwan and a simple wind tunnel test to demonstrate the determination of the optimal design fractile and its corresponding design wind pressure coefficient and design wind load.

Vol.33/No.3 (131) (2018)

作者:

Vol.33/No.3 (131) (2018)

TitleThe confinement effectiveness of transverse reinforcement in circular reinforced concrete columns
AuthorTai-Kuang Lee, Cheng-Cheng Chen
KeywordsCircular RC Columns, Transverse Reinforcement, Confinement Effectiveness
AbstractIn this study, a lateral cyclic load test was conducted on eight specimens of large-sized circular reinforced concrete (RC) columns to investigate the confinement effectiveness of circular ties and lap-spliced crossties. Totally, there are four series of specimens including R, S33, S17 and D33 constructed and tested. In single-cross crossties, the confining force of transverse reinforcement is calculated by adding the confinement effectiveness of one crosstie cross-sectional area. On the other hand, in double-cross crossties, the confining force of transverse reinforcement is calculated by adding the confinement effectiveness of two crosstie cross-sectional areas. The research results are presented as follows: (a) The seismic performance of circular RC columns with single-cross and double-cross lap-spliced crosstie correlates with the lateral loading direction. But its influence is not significant (b) The confinement effectiveness of circular tie is better than that of single-cross and double-cross lap-spliced crosstie. The reduction influence of lap-spliced crossties depends upon crosstie layout and the confinement force ratio. More details need further studies.
TitleUse of Stress Wave methods for Nondestructive Inspection of Epoxy-Bonded Length of Post-installed Rebars in Concrete
AuthorKai-Chung Teng, Chiang-Lung Chuang, Yiching Lin, Guo-Ruei Jiang
Keywordsquality of planting bars, nondestructive evaluation, stress waves, impact-echo
AbstractThis article develops a stress wave-based technology to detect non-destructively the epoxy-bonded length and embedded depth of post-installed rebars in concrete. Firstly, the finite element method (FEM) was used to simulate the stress wave propagation signal of the post-installed rebars in concrete to understand the wave propagation behavior of anchorage rebar. The results of the numerical analysis were verified by the impact-echo test performed on the concrete specimens containing post-installed rebars. The results show that a high amplitude peak can be found at the dominant frequency in the spectrum. The dominant frequency is mainly controlled by the exposed length and the epoxy-bonded length of the post-installed rebar. For a specific exposed length of the planting rebar, the longer the epoxy-bonded length, the higher the dominant frequency. In this paper, numerical analysis of three different exposed lengths (10,15 and 20 cm) were considered to establish the relationship between the dominant frequency and the epoxy-bonded length. The experimental results are in good agreement with those obtained from the numerical simulation. The results obtained from this study suggested that the epoxy-bonded length of post-installed rebar can be evaluated as follows: (1) The total length of the post-installed rebar can be measured by ultrasound. The embedded depth of the post-installed rebar is obtained by deducting the exposed length from the measured total length; (2) Impact-echo test measured the dominant frequency. The epoxy-bonded length can be predicted by substituting the dominant frequency into the established regression equation. The test results show that the estimated error of embedding length of post-installed rebar is mostly within 1 cm, which proves that the test method developed in this paper can be used to evaluate the quality of planting bars.
TitleEstablishment of B4-TW Prediction Model for Concrete Deformation in Taiwan ( I ) :Basic Creep, Drying Creep and Total Creep
AuthorTing-Kai Liu, Jenn-Chuan Chern
KeywordsConcrete, Long-term Deformation, Creep, Shrinkage, Database
AbstractAt present the concrete design code in Taiwan lacks any predictive model for concrete creep, which is why most engineers in Taiwan follow the models of the American Concrete Institute (ACI) or the American Association of State Highway and Transportation Officials (AASHTO) of the US; the European CEB-FIP and RILEM ; or the methods of the JSCE or JCI of Japan. Although the physical and chemical characteristics of concrete are essentially the same all across the world, each location uses its own constituent materials and mix design. In the present study, looking at the establishment of a concrete creep database for concrete in Taiwan, we have seen that the aggregate used in concrete of Taiwan is of lower quality. When formulating a mix design to attain higher strength, the resulting concrete will tend to have a high paste content, high cement content, low water cement ratio, and low aggregate/cement ratio. These local characteristics of concrete in Taiwan may lead to inaccuracies when they are applied to foreign predictive formulas, and in turn influence the structural behavior and safety of the concrete structures. Taiwan therefore has a manifest need for developing better localized predictive models for concrete creep. This study first presents the results from the predictive models for concrete creep (foreign and domestic formulas) applied to concrete in Taiwan. At present, it may be seen that the norms tend to undervalue. Then, it evaluates and actually uses the Model B4 predictive model for concrete creep suggested by Bažant in 2015 as a basis for the correction of characteristics in localized concrete in Taiwan in multiple situations: in instantaneous deformation items the reduction of the elasticity modulus in concrete due to low-quality aggregate was considered; in basic creep items the phenomenon of high levels of deformation due to high paste content and aggregate property were considered; in drying creep items the effect of sandstone aggregate, which is often used in Taiwan, was considered. Our results were as follows: after using the Model B4-TW model, which has been corrected for localized concrete in Taiwan, we may compare the two models (Model B4 and Model B4-TW); when predicting basic creep for Taiwan concrete, the coefficient of determination R2 rose from 0.52 to 0.78; when predicting the total strain, R2 rose from 0.76 to 0.81. In addition to R2, the statistical indicators given by scholars from around the world have shown that the predictive capabilities of the Model B4-TW model for concrete creep data in Taiwan are superior to other models; thus it can be further developed as a predictive model for concrete creep in Taiwan.
TitleEstablishment of B4-TW Prediction Model for Concrete Deformation in Taiwan ( II ) : Drying Shrinkage, Autogenous Shrinkage and Total Shrinkage
AuthorWei-Yi Chin, Jenn-Chuan Chern
Keywordsconcrete, long-term deformation, shrinkage, blast-furnace slag cement, fly ash, dataset
AbstractAt present, there is no definite formula for concrete shrinkage calculation in the concrete engineering design code of Taiwan, which cannot link with the nature of local concrete material. Most engineers in Taiwan often use the formula of American Concrete Institution (ACI), the American Association of State Highway and Transportation Officials (AASHTO), and European CEB-FIP and RILEM codes. The problem of concrete deformation is still different because it involves the climate environment, mix design, proportion and construction practice in different areas. The aggregate quality of the concrete used in Taiwan is poor, and the mix is designed to achieve the strength with the use of high paste volume, high cement content, low water/cement ratio, low aggregate/cement ratio and other characteristics. The localization characteristics described above cannot be mastered by foreign prediction formula, so Taiwan really needs to develop a good local concrete shrinkage prediction formula. Based on the evaluation of the existing domestic and foreign concrete shrinkage prediction formulae, this paper chooses the model B4 shrinkage prediction formula developed in 2015 by Bažant of Northwestern University. With regard to the local characteristics of the concrete in Taiwan, and the effect of the commonly used sandstone aggregate in Taiwan, the modified parameters of the aggregate are found. In this paper, the influence of concrete containing mineral admixture is modified: the FIB2000 is selected as autogenous shrinkage time growth curve; and the mineral admixture parameter table of model B4 is modified. These local modifications led to the establishment of the Model B4-TW. The results show that the model B4-TW shrinkage prediction formula, which included autogenous shrinkage, after localization correction has excellent performance in predicting the shrinkage of normal concrete or concrete containing mineral admixture in Taiwan, and can be developed as a concrete shrinkage prediction formula for Taiwan.
TitleExperimental Study of Reinforced Concrete Frame Filled with Low Masonry Window Spandrel
AuthorShuenn-Yih Chang, Ping-Chi Wu, Tsui-Huang Wu
KeywordsReinforced Concrete Building, Low Masonry Window Spandrel, Seismic Evaluation, Pushover Analysis
AbstractIn Taiwan area, structural damages caused by short column effect are very common in school buildings. The short column failure is closely related to the shear strength of the masonry window spandrel infilled within a reinforced concrete frame. The shear strength of a masonry window spandrel might be highly affected by its height-width ratio. However, this factor is not considered in the current evaluating formula and thus this formula seems unable to faithfully predict the shear strength. In fact, a formula for estimating the shear strength of a masonry window spandrel has been proposed. Because the height-width ratio of the masonry window spandrel was not considered in the formula its application is limited or might be inappropriate. To improve thisformula, three reinforced concrete frames were designed and fabricated for the cyclic loading tests for predicting the shear strength of a low masonry window spandrel within a reinforced concrete frame. One is a pure frame and the other two frames were infilled with different height of the masonry window spandrels. After conducting the cyclic loading tests of the three frames, the pushover analysis of each frame was also performed. Hence, after comparing the analytical result with the experimental results, the shear strength of the masonry window spandrel can be estimated. In this work, the height-weight ratio is chosen as an important factor for the newly proposed formula to estimate the shear strength of a low masonry window spandrel within a reinforced concrete frame. As a result, an improved formula for predicting the shear strength of the low masonry window spandrel within a reinforced concrete frame is proposed in this work.