Vol.31/No.1 (121) (2016)
| Title | Development of Windows-Based Automatic Design and Drawing Integrated System on Prestressed Concrete Bridges |
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| Author | Ping-Hsun Huang, Chi-HengChiang, Shu-Jen Chi, Yu-Chi Sung, Chun-Ying Wang, Jim-Ming Nian,Yu-Yang Lai, Yun Chuang, I-Chau Tsai |
| Keywords | Prestressed Concrete Bridge, Windows-based platform, Visual C# .NET |
| Abstract | Prestressed concrete bridge is the commonly used type of bridges in Taiwan. According to the planning considerations of this bridge, the longitudinal and cross-section analysis results need to be checked repeatedly in the design process to determine the span lengths, cross dimensions, load combinations, working procedure restrictions, tendon profiles and tensioning sequences, etc., and the interrelated work activities of engineering drawing, structural computation statement and quantity estimation would be very complicated and cumbersome. Hence, once the civil engineering drawing software has been connected with structural analysis program, the design process can be expedited to identify sketches and quantities automatically. As a consequence, based on the basic design theory and construction methods of prestressed concrete box girder bridge, this paper aims at progressing an automatic design and drawing system performed by the Visual C# .NET programming language and further development technology of AutoCAD. As practical bridge design course, the window-based platform and devisable results presented in this paper are expected to provide a useful perception in structural engineering. |
| Title | Lateral Load Displacement Curves of Low-Rise Reinforced Concrete Shear Walls |
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| Author | Pu-Wen Weng, Yi-An Li, Ren-Jie Tsai, Shyh-Jiann Hwang |
| Keywords | reinforced concrete, shear wall, lateral load displacement curve, shear strength, shear deformation, low-rise |
| Abstract | Reinforced concrete shear wall is commonly used as a structural member and possesses the characteristics of high stiffness and strength. During earthquake attacks, shear walls usually receive the major lateral forces and are prone to fail in shear. Therefore, prediction of the lateral load displacement curve of shear walls is essential for the seismic assessment of existing buildings. In accordance with the Technology Handbook for Seismic Evaluation and Retrofit of School Buildings published by National Center for Research on Earthquake Engineering, this paper employs the Softened Strut-and-Tie Model to estimate the seismic behavior of low-rise shear walls. By using the simplified strut-and-tie index and shear deformation estimated from the associated strain field at peak load, the proposed curve is greatly simplified and correlates well with the available test results. The current ACI 318-14 Code over-estimates the contribution of shear strength from the shear reinforcement and the proposed model can correct this drawback. In addition to predicting the shear strength of existing shear walls, the proposed model can also provide estimation of shear strength of RC infilled walls in new construction buildings. This application can assist engineers to evaluate accurately the influence of RC infilled walls on the seismic behavior of frames. |
| Title | Seismic Tests of Full-Scale Dual-Core Self-Centering Braces (DC-SCBs) and Sandwiched Buckling-Restrained Braces(SBRBs) |
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| Author | Chung-Che Chou, Ping-Ting Chung, Yu-Tsen Cheng |
| Keywords | Dual-core self-centering brace (DC-SCB), Sandwiched buckling-restrained brace (SBRB), Seismic tests |
| Abstract | This paper presentsseismic tests of full-scale dual-core self-centering braces (DC-SCBs) and sandwiched buckling-restrained braces (SBRBs). The DC-SCB has a flag-shaped hysteretic response with high axial stiffness and minimal residual deformation, exhibiting a self-centering mechanism. The SBRB like conventional BRBs has much higher energy dissipation capacity than the DC-SCB, but larger residual deformations are expected for structures equipped with SBRBs. The primary objective of the study was to conduct seismic tests that established a direct comparison basis between two DC-SCBs and two SBRBs designed with similar axial capacity and length. A total of DC-SCBs and SBRBs that were about 7.5 mlong and had maximum axial forces from 1500 to 6000 kN were tested to evaluate their cyclic behavior and durability. In general, these tests showed that the DC-SCB and SBRBexhibit robust cyclic performanceswith good deformation capacity and durability. The axial elastic and post-elastic stiffnesses of DC-SCB were around two and five times those of SBRB, indicating that DC-SCB is more effective to resist lateral forces than SBRB in structures. Some new buildings in Taiwan and China have adopted SBRBs as main earthquake-resisting members. |
| Title | Dynamic Stability of Frictional Isolation Systems Excited by Simple Harmonic Waves |
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| Author | Sheng-Hsuan Wang, Lap-Loi Chung, Yong-An Lai, Cho-Yen Yang |
| Keywords | frictional isolation systems, simple harmonic waves, dynamic stability |
| Abstract | According to the equivalent damping ratio formula of frictional isolation systems, the damping ratio becomes lower as the isolation displacement gets larger. Therefore, if the excitation is a simple harmonic wave with constant amplitude and ongoing input energy, then the displacement response of isolation systems will increase with time; on the contrary, the equivalent damping ratio of isolation system will decrease with time. The relationship between isolation displacement and damping ratio will make frictional isolation systems fall into the vicious circle and become dynamic unstable finally. To investigate the issue about dynamic stability of frictional isolation systems, we assumed the super-structure is rigid and the excitation is simple harmonic, and transformed the motion equation of isolation systems into the dimensionless form. We also set the response indices to help practical engineers preliminarily estimate the isolation design. Actually, real ground excitations will not make isolation systems dynamic unstable, but the vicious circle between displacement response and equivalent damping ratio of isolation systems is undoubted. For the reason that we proposed practical engineers take the characteristic into consideration to enhance the safety of isolation design. |
| Title | Seismic Vibration Control of Off-Shore Wind Turbines |
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| Author | Lyan-Ywan Lu, Hsuan-Teh Hu, Tzu-Yao Lin, Bo-Hua Lin |
| Keywords | Off-shore wind turbines, seismic mitigation, mass damper, anti-resonance, energy dissipation, wind energy |
| Abstract | Since Taiwan has one of the best wind-farms in the world, it is beneficial to develop renewable energy by using off-shore wind turbines. Nevertheless, since Taiwan is prone to earthquakes, the problem of seismic protection for the offshore wind turbines becomes an important issue. On the other hand, although current Taiwanese seismic design code is very stringent, it aims to ensure live safety in a major earthquake rather than the functionality of equipment in the structural system. In order to simultaneously ensure the safety and functionality of a wind turbine during a major earthquake, in this study, the possibility of using a mass damper (MD) system for mitigating the seismic response of offshore wind turbines is investigated. A MD system is established by introduced a soft and energy-dissipative layer between the nacelle and the supporting tower structure of a wind turbine. As a result, the interacting motion between the nacelle and underneath tower structure creates a significant anti-resonant phenomenon that is able to avert the seismic energy transmitted into the system. Different from a traditional tuned mass damper (TMD), the MD uses the mass of the nacelle itself as the reactive mass and its frequency may not be tuned to that of the structure. In this study, the seismic performance of a 5MW mono-pile off-shore wind turbine with the MD subjected to 16 seismic excitations is simulated. The simulation results have demonstrated that by properly selecting the MD parameters, i.e., the frequency and damping ratios, the acceleration of the nacelle and the base shear and moment of the supporting structure can be significantly reduced, as compared with a TMD-controlled or uncontrolled wind turbine. This implies that the MD technology is able to maintain the safety and functionality of a wind turbine in a major earthquake, simultaneously. |