Vol.34/No.1 (133) (2019)
| Title | Seismic design and analysis on boundary elements in bidirectional steel plate shear walls |
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| Author | Yi-Hsuan Yang, Tung Huang, Chao-Hsien Li, Ching-Yi Tsai, Keh-Chyuan Tsai |
| Keywords | bi-directional steel plate shear walls, capacity design, axial, shear and flexural interaction, finite element model analysis, composite beam |
| Abstract | The aim of this research is to propose a seismic design method for the corner vertical boundary elements (VBEs) in bidirectional steel plate shear walls (SPSWs) through a series of analytical and experimental studies. The VBEs at the intersection of bidirectional SPSWs must sustain the force demands induced from the two SPSWs simultaneously. The column axial force, bi-directional moments and shears are incorporated in the proposed procedures in computing the reduced column flexural capacities. The location of the bottom column flexural hinge is set at an elevation of 0.3 times the first story column height in order to achieve both performance and economy goals. In this paper, the effectiveness of the proposed design method is verified by four two-story L-shape bidirectional SPSW finite element model (FEM) analyses. The pushover analyses on the FEMs confirm that the flexural demands and the plastic hinge locations of the bottom corner VBEs can be predicted by the proposed method. This research also investigates the effectiveness of the composite action of the concrete slab and steel beam in the SPSW’s top boundary element using FEM analysis. Analysis results show that the composite action is not pronounced since the vertical downward panel forces are applied on the beam bottom flange. |
| Title | Optimization of Steel Panel Dampers for Moment Resisting Frame Designs |
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| Author | Chu-Hung Chang, Keh-Chyuan Tsai |
| Keywords | steel panel damper, seismic design, capacity design, shear buckling, optimization design, moment resisting frame |
| Abstract | The proposed 3-segment steel panel damper (SPD) consists of one middle inelastic core (IC) and two end elastic joint (EJ) wide-flange sections. During earthquakes, the two EJs of the same cross-sectional property, are designed to remain elastic while the IC could undergo large inelastic shear deformation thereby dissipating seismic energy. In order to sustain a large deformation and delay the shear buckling of the IC web, stiffeners must be properly devised. In this study, optimization algorithm is adopted to proportion the SPDs and the boundary beams, and achieve the minimum steel weight design. It is assumed that two identical SPDs, one above and one below, are attached to the boundary beam mid-span. The MATLAB optimization toolbox combined the simulated annealing algorithm with the gradient-descent method is adopted to find the minimum steel weight design. The objective function is the total weight of the SPD, the boundary beam and the panel zone. The design variables are the sectional properties of the SPD, the boundary beam and the doubler plate thickness. Constraints include the capacity design of the SPD, boundary beam and panel zone, the stiffeners of the IC web, compact section and lateral torsional buckling limit state design requirements. The ”basic design” is the lightest sections meeting all the constraints. The lateral stiffness of the two SPDs- to-boundary beam subassembly can be enhanced by either increasing the stiffness of the SPDs or the boundary beam. As examples, the optimization designs of increasing 50% more stiffness of the subassemblies as the new constraint were conducted also. While complying with the aforementioned constraints, the steel weight is increased by about 9% to achieve a 50% more stiffened design. The stiffness of the subassemblies are found enhanced most effectively by increasing the beam depths and web thicknesses. |
| Title | Development and Seismic Tests of Steel Self-Centering Sandwiched Buckling-Restrained Braces (SC-SBRBs) |
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| Author | Chung-Che Chou, Wen-Jing Tsai, Ping-Ting Chung |
| Keywords | Self-centering sandwiched buckling-restrained brace (SC-SBRB), Cyclic test, Residual deformation, Energy dissipation |
| Abstract | Earthquake-resisting frame systems that are designed based on current seismic provisions provide life safety performance in a large earthquake, but may have significant structural damage or residual drift due to energy dissipation in designated structural members. The damage leads to difficult or expensive repairs after a large earthquake. Therefore, development of a structural system that has both energy dissipation and self-centering properties in earthquakes is needed to improve the seismic performances of buildings. This paper presents a viable solution that was validated by multiple cyclic tests of an innovative brace, called a dual-core self-centering sandwiched buckling-restrained brace (SC-SBRB). The proposed brace combines the self-centering property of a dual-core self-centering brace (DC-SCB) and the energy dissipation of a sandwiched buckling-restrained brace (SBRB) together. The dual-core SC-SBRB is essentially a DC-SCB that is positioned concentrically with a SBRB to create both the self-centering and energy dissipation properties in either tension or compression. A 7860 mm-long dual-core SCSBRB, which uses ASTM A572 Gr. 50 steel as bracing members and ASTM A416 Grade 270 steel tendons as tensioning elements, was cyclically tested six times to validate its kinematics and cyclic performance. The test program demonstrated that the proposed dual-core SC-SBRB provides stable hysteretic responses with appreciable energy dissipation, self-centering behavior and large deformation capacity before low-cycle fatigue failure of the SBRB core. |
| Title | Development and Application of a Variable Stiffness Isolation System Considering Ground Motion Characteristic |
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| Author | Zheng-Jia Liu, Chia-En Hsiao, Tzu-Kang Lin, Lyan-Ywan Lu |
| Keywords | Stiffness-variable, energy of velocity, isolation system, semi-active control, minimum energy weighting |
| Abstract | In recent years, the research of isolation and mitigation system has become more and more important. In the traditional isolation and mitigation system, the control effect may be reduced because of unknown earthquake types. To have the best effect of response reduction, the systems have to be adaptive with the earthquake type. To achieve that, an upgraded algorithm, Feed-forward Predictive Earthquake Energy Analysis (FPEEA), is proposed by considering the energy of earthquake velocity to have the optimal response. The new algorithm quickly evaluates the velocity energy to have the optimal weighting of minimum energy weighting (MEW). With the optimal weighting of the potential energy and the kinetic energy, the PFEEA can reduce the structural responses efficiently. In order to demonstrate the performance of the proposed algorithm, a single-degree-of-freedom structure is used as a benchmark in both numerical simulation and experimental verification. With predicting the optimal weighting in advance, the type of earthquake can be defined before the main shock of earthquake comes. The results have shown that the dynamic response of the structure can be effectively alleviated. Comparing to the structural responses of the MEW method, the performance of the proposed algorithm is similar to MEW or even better. The shaking table test also demonstrates the feasibility of applying the proposed algorithm in practical application. |
| Title | A Life Cycle Consideration Structural Design Method for Concrete-Filled Steel Tubes Structure |
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| Author | Jenn-Chuan Chern, Zu-Liang Wu |
| Keywords | creep, autogenous shrinkage, drying creep, CFT, structural design |
| Abstract | The concrete-filled steel tubular structure has become a common structural type for buildings, which is matched with the use of self-compacting concrete, which is helpful for increasing the bearing capacity and stiffness of the high-rise building and increasing the effective use of the building area. However, the existing specifications and designs adopt the composite design method, and the structural design and the creep & Shrinkage behavior of the in-filled concrete and the interaction between concrete and steel tube are not fully considered in the existing structural design. This study introduces the time-dependent deformation characteristics of concrete and the necessity of applying local developed prediction formulas and proposes a design analysis method for concrete-filled steel tubular structures considering life cycle, and proposes design procedures and case studies to ensure the life expectancy in life cycle. During the period, the structural safety and serviceability of the structure can be ensured. |