Vol.32/No.1 (125) (2017)
| Title | Seismic Behavior of Reinforced Concrete Beams with Rectangular Spiral Reinforcement |
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| Author | Ping-Hsiung Wang, Kuo-Chun Chang, Yu-Chen Ou, Samuel Y. Yin, Jui-Chen Wang, Chih-Hsuan Chen, Chen-Wei Wu |
| Keywords | rectangular spiral, beam, plastic hinge, cyclic loading |
| Abstract | This paper presents an experimental study on reinforced concrete beam with continuous rectangular spiral as transverse reinforcement. Three exterior beam-column joint specimens with different beam detailing were devised to exhibit beam hinging and to examine their seismic performance under pseudo-static cyclic loading. Two beams with single and double rectangular spirals were introduced to compare with the one with traditional hoops. Test results show that beam specimen with single rectangular spiral has comparable hysteresis behavior compared to the traditional one, while the one with double rectangular spiral exhibits more degradation due to inadequate detailing at the end of spiral. Without the need of anchored hooks on each hoop, beam with rectangular spiral can save around 25% of transverse reinforcement in comparison with traditional hoops. Moreover, rectangular spiral can be automatically produced and easily erected with less labor effort. |
| Title | Seismic Tests of High Strength Concrete Filled Box Columns under Large Axial Loads |
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| Author | Chung-Che Chou, Sung-Cheng Wu |
| Keywords | High strength material, Concrete filled box column, High axial load beam-column specimen |
| Abstract | The cyclic behavior of high strength Concrete Filled Box Column (CFBC) under large axial loads was experimentally investigated. The parameters in the study included the width-to-thickness (b/t) ratio, axial load level and section type. Total six beam-column specimens were tested under a constant axial load and an increasing cyclic loading. The CFBC specimens were 280 to 420 mm in width and 2000 mm in height. Nominal b/t ratios varied from 11 to 30. All specimens were made of high strength steel SM 570M with a nominal yield strength of520~580 MPa.Three specimens were filled with high strength (80 MPa) concrete. Experimental results indicated that ductility decreases significantly with an increase in either axial load level or b/t ratio of the steel. The ductility does not change significantly whether concrete is infilled in the steel box column. Eurocode (EC 2004) and Architectural Institute of Japan (AIJ 2010) have good prediction in the flexural strength of high strength CFBC. AISC-LRFD (2010), ACI 318 (2011) and Taiwan Steel Design Code (2010) are too conservative in predicting the flexural strength of high strength CFBC. All the design codes are conservative in predicting high strength steel column moment capacity, especially for small b/t ratios. |
| Title | Performance-based design for earthquake-resistant coupled structural walls |
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| Author | Chung-Chan Hung , Yu-Hsiang Cheng ,Wei-Ting Lu |
| Keywords | coupled structural walls, performance-based design, nonlinear time-history analysis |
| Abstract | Coupled structural walls are often used in the buildings located in regions with high seismic risk. A coupled wall structure consists of two or more structural walls linked by coupling beams. It is able to provide efficient lateral strength and stiffness, which effectively reduces the drift response of buildings under earthquakes. Current seismic design codes are based on strength methods. Although they are able to prevent structures that are designed accordingly from collapse, the designers and users have limited knowledge about the seismic behavior of the designed structures under different levels of earthquakes. The objective of the present study is to develop a performance-based design method for coupled walls. The developed method allows engineers to pre-select the desirable coupling ratio and performance objectives for coupled walls, and then design the structures accordingly. In addition, it also facilitates the ideal yielding mechanism of coupled walls under earthquakes. Four example coupled wall structures are designed in this study using the proposed method. Their computational models are also built and analyzed using nonlinear time history procedures. The results show that the designed coupled walls are able to exhibit satisfactory structural yielding mechanisms and show the seismic behavior satisfying the pre-selected performance objectives for different seismic hazard levels. |
| Title | Optimal Design Formula for Viscous Damping Ratio in Isolation System with Consideration of Site Classification |
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| Author | Cho-Yen Yang,Yang-Chih Fan, Lap-Loi Chung, Bao-Jyun Lu |
| Keywords | design formula, isolation, viscous damping, optimal, site classification |
| Abstract | In this paper, the optimal viscous damping ratio for isolation system is studied. The linear restoring and damping force are considered. According to the previous literature in optimal design formulas, the white-noise excitation is considered. However, the case analysis in previous study was not doing well because the formulas could not retain the regional feature. Therefore, the numerical analysis intended to input several ground motion records in Taiwan. After that, the rigid and non-rigid superstructures for isolation system with various structure parameters are numerically simulated. The root mean square of absolute structure acceleration is selected to be the objection function for obtaining optimal isolation damping ratio. Repeating the optimal process with various structural parameters, the proposed simple design formula was developed by regression of those optimal isolation damping ratios from numerical simulations. Finally, we conducted the case analysis to verify the feasibility of proposed optimal design formulas. |
| Title | Seismic Analysis of Ceiling Lateral Bracing and Vertical Motion Effects on Suspended Ceilings |
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| Author | George C Yao, Wei-Chung Chen, Ching-Yao Lin |
| Keywords | suspended ceilings, lateral bracing assembly, bracing wire, shaking table experiment, vertical motion |
| Abstract | Past earthquakes have shown widespread damage to the suspended ceilings. Despite their frequent use in Taiwan, many suspended ceilings experienced damage in earthquakes owing to the lacked proper seismic design or efficient installation. In 2011, Taiwan Building Code issued the seismic installation of the suspended ceiling systems which are similar to the ASTM E580-09. However, the construction of the lateral bracing assembly has always been a difficult challenge. Problems include slack installation or omission of the bracing wires due to obstructions result in uneven quality of the bracing system in-situ. In recent years, some researches have demonstrated that the lateral bracing assembly may not adequately resist the lateral force. The other researches have even shown that unbraced ceiling systems may perform well when providing both sufficient clearance and wide closure. Therefore, there is an increasing concern about the necessity of the bracing system. In order to understand the dynamic behavior of bracing systems of the suspended ceilings, full scale shaking table experiments of suspended ceiling systems were conducted in this study. The first series of experiments on 5.7m × 2.7m ceiling systems looked into the seismic effects of the bracing assemblies. Some ceiling specimens were subjected to unidirectional ground motions while the others were subjected to a horizontal and a vertical ground motions acting together. The results clearly showed that the bracing wire bore only a small portion of the inertial force, and this situation became more obvious while the ceiling systems were subjected to vertical excitations. The second series of experiments on 5.7m × 2.7m ceiling systems compared the seismic performance of the braced and unbraced ceilings. The preliminary observations revealed that the use of the lateral bracing including compression post may not improve the seismic performance of the ceiling system. The unbraced ceiling systems performed well just as the braced ceiling systems when excited only by horizontal ground motions, and it performed better when the vertical ground motions were added to the ceiling systems. In this study, a conceptual computer model was developed based on the experiment data. The accuracy of the computer model was verified by using modal analysis. In comparison with the experiment results, this computer model provides the time-history analysis with reliable accuracy and helps simulate the dynamic response of different conditions of ceiling systems. |