In the current design of steel eccentrically braced frames (EBFs), the yielding link is coupled with the floor beam. This causes the design of cross-sectional dimensions of links to be enlarged, resulting in over-designed structures and foundations, and increasing the cost of the overall structure. In addition, the beams are forecast to sustain severe damage through repeated inelastic deformations under design-level earthquakes, and thus the structure may require extensive repair or need to be replaced. To improve upon these drawbacks, a shear device with replaceable links based on EBFs was designed. The hysteresis curve, the stress distribution, and the deformation of the specimen were obtained by cyclic loading tests of the eight replaceable links. The energy dissipation behavior, the bearing capacity, the failure modes, and the plastic rotation angle of those specimens were analyzed. The results indicated clearly that the links in this shear device had inelastic deformation concentrated in the link showing very stable hysteresis behavior, and damaged links were replaced easily as end-plate connections were adopted. The energy dissipation capacity and the plastic rotation angle of the specimens were mainly dependent on the arrangement of stiffener, length ratio, and welding access holes. Experimental studies performed in this research and the related damage analyses reveal that cracks are the major causes of damage to the EBF and there is a lack of research on real-time monitoring of the onset and development of these cracks in EBF structures. As a future work, this paper proposes a piezoceramic patch transducer-based active sensing approach to monitor the crack onset and development of the EBF when subjected to dynamic loadings.

A steel plate shear wall often uses partially encased composite (PEC) columns instead of edge frame columns. Such a steel plate shear wall not only bears the gravity load of the structure and resists the bending moment caused by lateral force by taking advantage of the high bearing capacity and bending stiffness of PEC columns, but also effectively anchors with the frame column to counteract the tension field generated by the steel plate. Therefore, the performance of the steel plate shear wall after buckling can be fully exerted and the seismic performance of the structure can be improved. In order to investigate the seismic performance of the structure, a 1/3-scale specimen test of steel plate shear wall with PEC columns is designed and fabricated, and a finite element model is established with the same size of test. It is found that the test and simulation results are in good agreement, which confirms the reliability of the simulation. Subsequently, 20 models with different parameters of steel plate shear wall with PEC columns are analyzed using ABAQUS. Finally, the failure mode, hysteretic behavior, skeleton curve, and bearing capacity of steel plate shear wall with PEC columns are obtained. The results show that PEC columns have a good anchoring effect on the diagonal tension field and can fully exert the plasticity of the infill steel plate, so that steel plate shear wall with PEC columns has superior seismic performance. Experiments also reveal that the crack type of damages appear in a steel plate shear wall with PEC columns, and, as a future work, the authors will explore the use of structural health monitoring methods, such as piezoceramic transducer-based method, to monitor such cracks.

In the current design method of the eccentrically braced frame structure, the energy dissipation link and the frame beam are both designed as a whole. It is difficult to accurately assess the degree of damage through this method, and it is also hard to repair or replace the energy dissipation link after strong seismic events. Meanwhile, the overall design approach will increase the project’s overall cost. In order to solve the above mentioned shortcomings, the energy dissipation link is designed as an independent component, which is separated from the frame beam. In this paper, the energy dissipation link is bolted to the web of the frame beam. Both finite element simulation and test study of eight groups of energy dissipation links have been completed to study their mechanical behaviors, and the energy dissipation links have been studied in the aspects of length, cross section, and stiffener spacing. The mechanical behaviors include the energy dissipation behavior, bearing capacity, stiffness, and plastic rotation angle. The results indicate clearly that the hysteretic loop of links in the test and finite element analysis is relatively full. By comparing the experimental and finite element simulation data, it can be found that the general shape and trend of hysteretic loop, skeleton curve, and stiffness degradation curve are basically the same. The experiment data explicitly shows that the energy dissipation link of web-connected displays good ductility and stable energy dissipation ability. In addition, the replaceable links possess good rotational capacity when the minimum rotation angle of each specimen in the test is 0.16 rad. The results of the experiment show that the energy dissipation capacity of the link is mainly related to the section size and the stiffening rib spacing of the link. The energy dissipation ability and deformation ability of the link is poorer as the section size becomes larger; meanwhile, these abilities are reduced with the decrease of the stiffening spacing. The experiment result shows that the damage and excessive inelastic deformations are concentrated in the link to avoid any issues for the rest of the surrounding elements, and the links can be easily and inexpensively replaced after strong seismic events. The results are thought provoking, as they provide a theoretical basis for the further study of the eccentrically braced frame structure with replaceable links of web-connected. In future work, the author aims to carry out his studies through optimized design methodology based on the yielding criterion.

Abstract:In order to improve the behavior of double-tube buckling restrained braces (BRBs), it is proposed to set contact rings between inner tube and outer tube of the brace. As a result, they can provide lateral constraint for the inner tube; this is the improved buckling restrained braces (IBRBs). In this paper, a program was edited by the language of MATLAB based on theoretical model formulation of IBRBs and applied to the calculation of overall stability strength capacity. Finite element models of IBRBs were carried out and both load displacement curves and strength capacity were obtained. Tests on IBRBs were also conducted. The results of numerical simulation agreed with the ones of the program and tests. It indicated that the program was reasonable so it could provide a basis for the analysis of overall stability strength capacity of these kinds of IBRBs.

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