Vol.33/No.2 (130) (2018)
| Title | Improving Seismic Performance of Hollow Steel Reinforced Concrete Members with Inclined Bars |
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| Author | Hsieh-Lung Hsu, Ming-Te Hong |
| Keywords | steel reinforced concrete, flexural-torsional behavior, inclined bars |
| Abstract | This study focused on the improvement of flexural-torsional behavior of hollow composite members subjected to eccentric cyclic loads. A series of composite members composed of encased steel tubes and reinforced concrete with various inclined bars were fabricated for testing. Member performance was evaluated by the strength, stiffness and energy dissipation during the loading history. Test results showed that the strength of members with inclined bars was significantly increased when subjected to torsion and combined loading coupled with torsion. Enhancement in energy dissipation further validated the applicability of incline bars to the performance improvement of hollow composite members. |
| Title | The Effect of Different Transverse Reinforcement Schemes on the Confinement of Encased Concrete-Filled Box Columns |
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| Author | Cheng-Cheng Chen, Pin-Da Wu, Jia-Xi Zhou |
| Keywords | Encased Concrete-Filled Steel Box Columns, steel reinforced concrete column, SRC column, encased box column, concrete filled box column. |
| Abstract | The concrete in a concrete-filled steel box column is confined by the box column. However, the confinement of the concrete outside the box column(referred as outer concrete hereafter) in an encased concrete-filled box column 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 note be implemented here. In this article, the confinement effect of so called corner tie, combined tie and lateral tie are investigated experimentally. Ten large-sized concrete-encased concrete-filled steel box short columns were tested under monotonic axial compression. Based on the test results obtained, the following conclusions are made: (a) the corner tie was unable to provide sufficient lateral support to the longitudinal bar and corner concrete that required by the design code; (b) the use of combined tie can provide sufficient confinement to the outer concrete, (c) the potential of lateral tie in providing sufficient confinement to the outer concrete is high, however, further research is needed to confirm it. |
| Title | Study on Short-Stroke Damper Assembled in Tuned Mass Damper |
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| Author | Yong-An Lai, Fan-Yen Meng, Kuan-Hua Lien, Lap-Loi Chung |
| Keywords | tuned mass damper, short-stroke damper, optimal design, damper stroke |
| Abstract | In the conventional tuned mass damper (TMD), the damper stroke and the mass stroke must be the same, thus the long-stroke dampers are required for implementation in TMD. In addition, a considerable size and higher precision for manufacture of long-stroke damper majorly cause expensive budget for installation and maintenance of the TMD. According to the above features, the“Short-Stroke Damper assembled in Tuned Mass Damper (SSD-TMD)” is proposed in order to reduce the damper stroke in the TMD. In the SSD-TMD, the stiffness of SSD-TMD is separated into two parts. The first part is connected with the viscous damper in parallel. Then, the paralleled system is connected with the stiffness of the second part in series. Afterwards, the mass block is further attached to form the SSD-TMD. This assemblage will produce different strokes between the damper and the mass so that the damper stroke can be significantly mitigated under appropriate design of the stiffnesses and damping coefficient. In this article, the model of the SSD-TMD is firstly proposed. The design formulae and procedure of the SSD-TMD is also proposed by following the optimal design parameters for conventional TMD. The case study of the Taipei 101 structure implemented with the SSD-TMD shows that the damper stroke of the SSD-TMD can be dramatically reduced, so that the short-stroke dampers can be used to replace the long-stroke dampers. Furthermore, with suitable design of the SSD-TMD, both effectiveness of structural vibration reduction and mass stroke of the SSD-TMD can outperform the conventional TMD. |
| Title | Simplified Seismic Evaluation Method on Old Buildings |
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| Author | Yu-Chih Lai, Tao Lai, Lap-Loi Chung, Guo-Luen Huang, Yao-Sheng Yang, Chien-Chuang Tseng, Sheng-Hsueh Lin, Chu-Yuan Chang |
| Keywords | seismic evaluation, maximum base shear, in-situ test |
| Abstract | The earthquakes happen in Taiwan, such as Chi-Chi earthquake, let us know seismic capacity of old buildings is not enough. Because it may cause casualty, it is important to raise seismic ability of those old buildings. School buildings belong to public facility and provide people shelters when their home are damaged seriously by earthquake. Therefore their seismic ability should be raised as soon as possible. National Center for Research on Earthquake Engineering (NCREE) proposed complete procedures for seismic evaluation. The procedures of seismic evaluations include: simple survey, preliminary evaluation and detailed evaluation. After screening out school buildings which have less seismic capacity than seismic demand, we need to do seismic retrofit for them. However, there are lots of other old buildings in Taiwan (such as street houses, hospitals and executive agency) need to raise their seismic ability. In this paper, the method use Ultimate Moment Balanced Method to do Simplified Detailed Seismic Evaluation is proposed. The method first evaluates the lateral strength of each column line and multiplied by reduction factor which decided by failure mode of column. And then add lateral strength of each column after reduction, the result is the maximum base shear strength of building. Also, decides the ductility capacity of each column by its failure mode. The ductility capacity of building can be decided by the ductility capacity of each column weighted its lateral strength. Finally, using the ratio of seismic capacity and seismic demand can get the seismic performance of the building before detailed evaluation. Since Ultimate Moment Balanced Method consider both failure mode of strong beam weak column and strong column weak beam, the method can be used on old building either before or after retrofit. This paper takes Ruei Pu elementary school in Taoyuan county as an example to do Simplified Detailed Seismic Evaluation. It is proved that both maximum base shear and seismic capacity are conservative compared to in-situ test. So the method can be used on existing buildings for seismic evaluation. The Simplified Detailed Seismic Evaluation method can be used on establishing the preliminary evaluation method of buildings in addition to school buildings for engineers to application. |
| Title | Probabilistic assessment of seismic performance and collapse risk for mid-rise buildings |
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| Author | Wei-Huan Hsieh, Lyan-Ywan Lu, Fu-PeiHsiao, Yu-Shi Tang, Yin-Nan Huang |
| Keywords | Wei-Huan Hsieh, Lyan-Ywan Lu, Fu-PeiHsiao, Yu-Shi Tang, Yin-Nan Huang Mid-rise building, seismic performance assessment, probabilistic assessment, collapse fragility analysis, risk assessment, incremental dynamic analysis, nonlinear time history analysis |
| Abstract | Mid-rise buildings, which are usually heavily populated, are very common structures in urban areas. The casualty and social impact caused by the collapse of mid-rise buildings in an earthquake can not be overestimated. Therefore, developing suitable assessment methods to identify the buildings with high collapse risk becomes a critical issue. Even though traditional seismic assessment methods, which usually employ nonlinear static pushover analysis, have been successfully applied to regular low-rise buildings, these methods are unable to reflect higher-mode effect on the responses of mid-rise buildings. Furthermore, a traditional approach usually leads to a deterministic result that could not account for the uncertainty in seismic motions and structural responses of a mid-rise building, which is usually more complicated and involves more structural uncertainties than a low-rise building. To this end, this paper presents a procedure and methodology to assess the collapse risk of a mid-rise building. This methodology is developed based on the collapse fragility analysis proposed by FEMA P-58, the collapse criteria proposed by PEER-TBI and ASCE 41-13, and acceptance criteria suggested by ASCE 41-13 and FEMA 356. To establish the fragility curves, this approach employs nonlinear time history analysis together with the method of incremental dynamic analysis (IDA) to estimate structural response parameters. Finally, for demonstration, the proposed assessment method is applied to assess the collapse risk of a mid-rise building that collapsed in an earthquake. |