Vol.30/No.4 (120) (2015)
| Title | Research on the seismic resistance of steel bridge piers with energy dissipation plates |
|---|---|
| Author | Sheng-Jin Chen , Nan-jiao Lin |
| Keywords | seismic resistance , steel bridge piers , energy dissipation plates |
| Abstract | A new type steel bridge column is proposed and examined for its seismic resistance. In this study, an innovated method is proposed for bridge column with enhanced force transmission and energy dissipation for seismic resistance. At the connection of the column, the force transmission is the same as the conventional design method. However in the connection plate, besides the conventional force transmission, part of the connection plate is designed to dissipate the seismic energy. In the designated energy dissipation area, a serial of slot-hole connections are provided. With this arrangement, the joint can provide a mechanism for force transmission and energy dissipation. A series of experimental study is carried out on the new type of bridge column. From this study, it is found that the new type steel column is able to reach seven times of yielding deformation, 6.55% radium of rotation angle, without decay on its strength. The plastic zone is moved to the connection plate. The dissipated energy based on the new method is more than two times as compare with the traditional steel bridge column. The energy dissipation zone can be preselected. After earthquake, it is easier to perform inspection, retrofit, or replace the damaged connection plate if necessary. |
| Title | Seismic Retrofit of Reinforced Concrete Frames with Buckling-restrained Braced Frames |
|---|---|
| Author | Kuan-Yu Pan , An-Chien Wu, Chao-Hsien Li , Keh-Chyuan Tsai |
| Keywords | seismic retrofit, reinforced concrete frame, buckling-restrained brace, bearing block, post-installed anchor, softened strut-and-tie model |
| Abstract | Instead of applying the post-installed anchors to transfer the seismic loads, the proposed retrofitting brace system consists of high-strength mortar bearing blocks constructed at the four corners of the existing reinforced concrete (RC) frame to transfer the earthquake forces. In comparison with the traditional retrofitting methods, it avoids the complex on-site anchor installation process. Thus, the brace force capacity is not directly limited by the anchor resisting strength. Buckling-restrained braces (BRBs) are adopted in the proposed retrofitting system to improve the structural strength, stiffness and energy dissipation efficiency. In this study, cyclically increasing lateral displacements were imposed on two RC frames retrofitted with the same WT steel frames for different BRB strength capacities. Cyclic loading test on the third RC frame infilled with the same WT frame only was also conducted to evaluate the strength and stiffness enhancements. Test results indicate that the proposed retrofitting method is efficient in increasing the lateral strength up to the 3% drift ratio while achieving rather good ductility and energy-dissipating capacity. The increased lateral strength and stiffness were more than 2.2 and 3.5 times those of RC frame infilled with WT frame only, respectively. A simplified structural calculation and a detailed PISA3D analysis are proposed to show the effectiveness in predicting member demands to within 13.8% of the test measured test results. Under cyclic lateral loads, the steel braced frame imposes additional shear forces through the bearing blocks to both ends of the RC beam and column member discontinuity regions. In this research, the softened strut-and-tie model was satisfactorily applied in estimating the shear capacities for the discontinuity regions. |
| Title | Structural Isolation Design Procedures with Optimal Viscous Damping |
|---|---|
| Author | Cho-Yen Yang , Sheng-Hsuan Wang , Shao-Kuei Liu , Lap-Loi Chung, Wei-Liang Hung, Lu-Min Chen |
| Keywords | isolation design procedures, optimal viscous damping, non-design earthquake |
| Abstract | Based on the concept of seismic design spectrum, the design seismic force is smaller when a structure possesses longer fundamental period. It is the main purpose for isolation system. The damping plays a significant role with function of energy dissipation and reducing the isolation displacement. Because of the uncertainty about earthquake intensity and fault activity, the structure may encounter a non-design earthquake with greater peak ground acceleration (PGA) or a near-fault earthquake within the structural service life. For this reason, we attempted to integrate the optimal viscous damping ratio formula into the conventional design procedures, called optimized design procedures, and chose a real case to do the time history analysis and then discussed the feasibility of optimized design procedure. Three earthquake types were utilized as input, one was the design earthquake, another was a non-design earthquake with PGA which was 1.5 times the design earthquake, the other was a near-fault earthquake. Regardless of the types of input, the isolation system with optimal damping ratio can play a good result about isolation effect and displacement. Therefore, we confirm integrating the optimal damping ratio formula into the conventional procedures is essential. For engineers, there is just one more step in the optimized design procedures than the conventional one, and the requirement of damping can be determined according to the proposed procedures. |
| Title | Model fitting of the experiment of buckling-restrained brace by using gradient descent method |
|---|---|
| Author | Ming-Chieh Chuang, Shang-Hsien Hsieh, An-Chien Wu |
| Keywords | model fitting, optimization, gradient descent method, buckling-restrained brace, nonlinear simulation experiments |
| Abstract | In simulation of structural behavior, researchers often need to calibrate the parameters of a nonlinear material model with corresponding experimental data by using the trial and error method, which is very tedious and time consuming. To improve the efficiency of the calibration task, this research proposes an optimization approach using the classical gradient descent method to perform automated model fitting for the hardening material model of the buckling-restrained brace (BRB). Two component tests of the BRB conducted in the National Center for Research on Earthquake Engineering are used to test and validate the proposed approach. The results show that the proposed approach is not only more efficient but also more accurate in simulation of the BRB test results than the trial and error method. |
The Study for Engineering Properties of Cement Mortar added with Fly Ash and Piezoelectric Materials
| Title | The Study for Engineering Properties of Cement Mortar added with Fly Ash and Piezoelectric Materials |
|---|---|
| Author | Her-Yung Wang, Shyh-Haur Chen, Shu-Chuan Chang, Jhan-Cyue Lin |
| Keywords | intelligent, disaster prevention, cement mortar, fly ash, piezoelectric materials (PZT), electromechanical properties |
| Abstract | Taiwan, which is located in the plate junction, experiences frequent earthquakes, abundant rainfall during the typhoon season, and frequent natural disasters. Improvements in the intelligent disaster prevention functions of buildings are imperative. The development of piezoelectric composite materials has become more popular in recent years. Piezoelectric composite materials are used in civil engineering to compensate for the functional deficiencies of the original base materials. The piezoelectric effect of these materials can also be used for the preparation of controllers or sensors, which greatly increase the technological capabilities of civil engineering structures. The function of concrete, the most common material in civil engineering, is no longer to simply resist pressure; with the advent of intelligent piezoelectric materials. In this study, the piezoelectric material with recycled materials, for each group to explore the impact of cement mortar mechanical and electrical, the understanding of cement mortar in different farm environment and water content, the relevance of their impedance characteristics and mechanical behavior of recycled materials and to establish their piezoelectric materials cement mortar Electro relationship database to identify the relationship between the various variables. The cement mortar materials prepared by replacing the cement component with varying amounts of fly ash 0%, 10%, 20% and 30%, respectively (control group). The piezoelectric materials were prepared by replacing the 5% fine aggregate with piezoelectric powder (PZT group). The electromechanical properties were tested to assess the correlations among flow, compressive strength, water absorption, and electricity at 50 V and 100 V. The correlations between these properties were also investigated. At the curing age of 28 days, the compressive strength of the control group was in the range of 31.0-20.4 MPa, whereas the compressive strength of PZT group was in the range of 29.0-19.0 MPa. The control group exhibited higher results (1870-1588Ω.cm) in the electricity property test under 50 V, whereas PZT group exhibited lower results (1419-1286Ω.cm). The compressive strength and results of the electricity property tests demonstrated that the compressive strength and electrical resistance decreased as the replacement of fly ash increased. The strength of the control group was higher than the strength of PZT group because 5% of the fine aggregate was replaced by the piezoelectric material and the piezoelectric material was water-resistant. However, this study was just 5% of the fine aggregate replaced by the piezoelectric material that regarding the compressive strength. |