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In this study, a re-centering energy-dissipation brace with a pendulum (REBP) is proposed for high-rise structures. The REBP can consume energy by friction under the action of a horizontal external load, and then re-center the structure by means of cable pretension after removing the load. Through the lever action of the pendulum, the deformation capability of the REBP is significantly amplified with the small deformation of the cables, and can satisfy the inter-story drift requirement for a severe earthquake. The REBP is optimized from a prestressed re-centering energy-dissipation brace (PTSEB) previously proposed by the authors. In particular, the T-shaped pendulum in the PTSEB is replaced by a truss pendulum. The pendulum-wing, vertical bar, and diagonal bars form a truss with high strength. This increases the initial stiffness and energy consumption capability of the REBP, and decreases the weight of the REBP. Two semicircle rollers are set on the top and bottom of the blocker to facilitate its rotation. An hysteretic model and design formulas are proposed for the REBP. Through cyclic testing and a finite element (FE) analysis of REBPs with five different cable pretensions, the cyclic behaviors of the REBP and the influences of cable pretension on the energy consumption, re-centering, stiffness, friction, and cable tension are determined. The results indicate that the REBP has good energy consumption and a good re-centering capability. An increase in cable pretension leads to an increases in the friction between the blocker and pendulum-wing, energy consumption capability, and stiffness.

In this study, high-strength cables were used to create a prestressed T-type self-centering energy-dissipation brace (PTSEB), which can be used for multi-story and high-rise frame structures. The brace can dissipate energy through friction, provide lateral stiffness through prestressed cables, and automatically return to its original position under the action of cable tension after the external load disappears. Lever action is used to significantly amplify the deformation ability of the brace. Moreover, the energy-dissipation ability of the brace is considerably better than that of a traditional self-centering brace. A test and a finite element analysis were performed on the PTSEB, and the results indicated that the brace had a strong energy-dissipation ability, as well as a high deformation capacity and self-centering capacity. ABAQUS was used to analyze and compare the performance of braces with different sizes. The results showed that in a certain range, as the shell height increased, the seismic performance of the PTSEB was improved significantly; however, an increase in the shell width did not improve the seismic performance of the PTSEB significantly. Reasonable sizes for the PTSEB were proposed based on a finite element parameter analysis to ensure that the brace would have improved energy-dissipation and self-centering abilities. A restoring force model of the PTSEB was constructed, and the key points of the restoring force model were obtained using some proposed formulas. The design parameters of the PTSEB could be determined based on these formulas.

Steel cable with its superior performance is used in steel structure as a brace. An X-deployed cable-braced bolt-assembly steel frame (CBBSF) was proposed. The seismic behaviors of an unbraced moment-resisting bolted steel frame (BSF) and four pairs of CBBSFs were tested and analyzed by the finite-element model under cyclic load. The steel frames of CBBSF are the same, while the cables have the same sectional area in each pair and have varying sectional areas between different pairs. In each pair of CBBSF including CBBSF-F and CBBSF-W, the cables of CBBSF-F are pre-slacked, while the cables of CBBSF-W are not pre-tensioned or pre-relaxed. A formula for the lateral stiffness of the CBBSF was proposed. The hysteresis performance, strength, ductility, stiffness, self-centering capability, and failure mode of the CBBSFs were obtained and compared with each other and with the BSF. The influence of the cable sectional area and pre-slack on these behaviors was obtained. It was found that CBBSFs exhibit reasonable hysteresis performance, energy dissipation capacity, self-centering capability, and have large stiffness and strength. The hysteretic performance and energy dissipation capacity of CBBSF is better than BSF. The CBBSF with a larger cable sectional area has better self-centering capability. The energy dissipation capacity and ductility increased initially with the increase of cable sectional area, then, followed by a subsequent decrease. The cable pre-relaxation decreased the maximum cable force to avoid break, increased the yield displacement, ultimate displacement, and ductility of CBBSF, and slightly decreased the yield and ultimate strength.

In this study, the square steel tube column is connected by bolted flange instead of traditional welding. For multi-rise structure, tension, bending moment, and shear force may act on the connection under vertical and horizontal loads. To investigate the mechanical behavior of flange connections, full-scale model tests and finite element analyses of 10 bolted-flange joints were carried out. The mechanical properties of the specimens and the influence of the flange thickness, flange size, and bolt hole diameter under a tension–bend–shear combination were obtained. The size of the bolt hole and flange has little effect on the load-carrying capacity of the connection. With the increase of the thickness of flange, the flexural rigidity and load-carrying capacity of the connection increase obviously, and the yield mechanism of the specimen changes from flange yield to bolt yield. The influence of the axial tension ratio on the bolt tension was investigated by the experiment-verified finite element models. The axial tension ratio is the value that the axial force of column divided by the cross-sectional area and the material design strength of the column. Increasing the axial tension ratio may increase the bolt tension, which has a harmful effect on the bolts at the tension side of the flange. Using yield line theory, formulas for calculating the static load-bearing capacity resisting the bending moment, shear and tension were deduced and verified by comparing with the result of experiment and finite element analysis.