Vol.30/No.3 (119) (2015)
| Title | Shear Crack Control for High-strength Reinforced Concrete Beams Considering the Shear-span to Depth Ratio of Member |
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| Author | Chien-Kuo Chiu, Fang-Cing Lin, Shao-Cian Chen, Kai-Ning Chi |
| Keywords | high-strength reinforced concrete, shear crack, span-depth ratio, serviceability, reparability |
| Abstract | This work tests ten full-size simple-supported beam specimens with the high-strength reinforcing steel bars (SD685 and SD785) using the four-point loading. The measured compressive strength of the concrete is in the range of 70-100 MPa. The main variable considered in the study is the shear-span to depth ratio. Base on the experimental date that include maximum shear crack width, residual shear crack width, angle of the main crack and shear drift ratio, a simplified equation are proposed to predict the shear deformation of the HSRC beam member. Besides of the post-earthquake damage assessment, these results can also be used to build the performance-based design for HSRC structures. And using the allowable shear stress at the peak maximum shear crack width of 0.4 mm and 1.0 mm to suggest the design formulas that can ensure serviceability (long-term loading) and reparability (short-term loading) for shear-critical high-strength reinforced concrete (HSRC) beam members. |
| Title | A Study of Mechanical Behavior of Reinforced Lightweight Concrete Slab |
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| Author | Yu-Cheng Kan, Ruey-Sheng Lin, Tsong Yen, Chung-Ho Hwang |
| Keywords | Lightweight aggregate, RC slab, flexural, shearing |
| Abstract | The mechanical behavior of simply-supported reinforced lightweight concrete slab under a concentrated load is investigated herein. The test results were also compared to those obtained from normal concrete slabs. Totally 32 slabs in various strengths, thicknesses and rebar arrangements were fabricated and tested. The ultimate load, ductility and failure pattern were examined in each load test. The test results showed that the ultimate load of the slabs turned out very close to those calculated based on yield line theory. For the slab with the same amount of reinforcement, the slab including singly-reinforcement in 95 mm spacing performs higher load capacity than those including double- reinforced rebar with 190 mm spacing, but the latter needs more fracture energy and performs more ductile. |
| Title | Ultimate Base Shear by Direct Moment Equilibrium |
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| Author | Yang-Chih Fan, Lap-Loi Chung, Cho-Yen Yang, Shao-KueiLiu, Wei-Liang Hung , Lu-Min Chen |
| Keywords | ultimate base shear, seismic evaluation, plastic moment |
| Abstract | The verification of ultimate story shear is asked by building code to ensure the shear strength is sufficient and no significant variation of stiffness for each story. However, there is no exact definition about calculation of ultimate story shear from the current building code. In this paper, a new method named direct moment equilibrium method is proposed. The ultimate shear is determined by directly taking moment equilibrium for each column. The ultimate story shear is obtained by taking summation of ultimate shear from each column. The proposed direct moment equilibrium method is also compared with two other methods which are familiar in practical application. Finally, the complexity of calculation and feasibility of the direct moment equilibrium method are verified. |
| Title | The latest development of using non-destructive test method for detecting the bonding condition of steel plate reinforced structure with field study |
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| Author | Chia-Chi Cheng, Keng-Tsang Hsu, Chi-Luen Huang, Tsung-Chi Lin, Yeng-Ting Pan |
| Keywords | concrete, steel plate reinforcement, non-destructive test, stress wave, impact-echo, Lamb wave |
| Abstract | In Taiwan, many infrastructural facilitiesuse steel plate to reinforce the structural member. Some of the repaired structures has been operated for 20 years. For example, cracks were found on the pier capping beams of more than 200 viaducts alone the Taipei MRT Wenhu lineduring construction and were repaired by covering the steel jacket. Experiencing long-term operational vibrations and earthquakes events for 20 years, the bonding condition between the steel plate and concrete isleft unknown. In this article, twomethods based on stress wave propagation for assessing the bonding condition between the steel plate and concrete were introduced – impact-echo normalized spectrum and the dispersion curve of the fundamental Lamb wave mode of steel plate. The validation of the two methods in field study is realized by applying tests on the steel plate reinforced floor of a food factory. The areas lack of epoxy fillings between the steel plate and concrete were identified using both methods andthe bonding conditions are confirmed by core drilling. The Lamb wave method, which is able to assess the bonding condition under the 400 mm test line, can be served as the tool for quick assessment while the impact-echo tests can be applied on the questionable area for detail identification of the poor-bond area. |
| Title | Development and Application of Vibration Isolation System with Adaptive Stiffness Considering Potential Energy |
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| Author | Chi-Jen Chen, Tzu-Kang Lin, Lyan-Ywan Lu |
| Keywords | Potential energy, Semi-active control, near-fault earthquake, MEW |
| Abstract | In recent years, a study of semi-active isolation system named Leverage-type Stiffness Controllable Isolation System (LSCIS) was proposed. The main concept of the LSCIS is to adjust the stiffness in the isolator for the fundamental period of the superstructure by a simple leverage mechanism. Although great performance has been achieved with the support of an algorithm considering the least input energy in far-field earthquakes, some result still reveal that the proposed system is not suitable in application for near-fault strong ground motion. To overcome this problem, an upgraded algorithm is proposed by considering the potential energy effect in the semi-active structural control system in this study. Firstly, the new algorithm is developed with the combination of the potential energy (Ep) and the kinetic energy (Ep) as the control objective to reduce the structural displacement responses efficiently. The optimal weightings between the potential and kinetic energy are then determined through a series of near-fault earthquake simulation. In order to demonstrate the performance of the proposed algorithm, a two-degree-of-freedom structure is used as a benchmark in both numerical simulation and experimental verification. The results have shown that the dynamic response of the structure can be effectively alleviated by the proposed algorithm under both far-field and near-fault earthquakes, while the structural responses by the original algorithm may be worse than the pure passive control. The feasibility of implementing the proposed system has also been experimentally verified. |