Seismic Performance Research On Pre-pressed Disc Springs Self-centering Energy Dissipation Brace And Braced Substructures

A new type of pre-pressed spring self-centering energy dissipation (PS-SCED) brace is proposed to reduce residual deformation after earthquakes and improve the seismic performance of structures. Disc springs are used to provide self-centering force for the proposed brace and friction devices are used to provide energy dissipation. The prediction model which can portray the hysteretic behavior of PS-SCED braces has been developed, verification tests are carried out under low cyclic reversed loadings to study the hysteretic behavior of PS-SCED brace, and numerical simulations for seismic performances of PS-SCED braced substructures are analyzed at the same time. The main research contents are as follows:(1) The prediction hysteretic model of brace is developed based on the study of the hysteretic models of friction device and disc spring device which can provide energy dissipation capacity and self-centering capability, respectively. The seismic performances of PS-SCED brace under low cyclic reversed loading are analyzed through numerical simulation, and results indicate that the PS-SCED brace exhibits stable flag-shaped hysteretic performances with strong energy dissipation capacity and good self-centering behavior.(2) A 1.8m long PS-SCED brace component was fabricated, and a series of low cyclic reversed loading tests of the specimen under three initial conditions of same pre-pressed force and different friction forces were carried out. Results indicate that the flag-shaped hysteretic curve of PS-SCED brace has stable the first and the second stiffness, the energy dissipation capacity is enhanced with the increase of friction force provided by the friction device, the brace specimen is still within the elastic state when the deformation rate is 1.36%, it demonstrates that the brace has a good ductility behavior, and the residual deformation of brace can be controlled by adjusting the ratio between the pre-pressed force of disc springs and the initial friction force. Hysteretic curves of prediction model have good agreement with that of tests, it demonstrates that the prediction model can better reflect the actual force situation of the bracing system.(3) Taking a single-story and single-span frame substructure as numerical example, comparisons of the seismic performance of substructure with PS-SCED braces and substructure with traditional braces are conducted. Results indicate that the PS-SCED braced substructure exhibits better energy dissipation capacity and self-centering behavior under dynamic load, the bearing capacity has increased by 44%, the accumulated energy dissipation capacity has increased by 20% and the residual drift ratio has reduced by 64% as compared with the traditional braced substructure, and the seismic performance of structure has been improved effectively by PS-SCED braces.(4) Seismic performance analysis of the PS-SCED braced substructures with rigid and hinged connections are carried out, respectively, and results indicate that the hinged braced substructure has better ductility, more stable flag-shaped hysteretic performance and higher bearing capacity, and has a better ability to control the residual deformations than the rigid connected braced substructure. The mechanical behavior of rigid connected brace is greatly influenced by the transfer bending moment of connection plate. The energy dissipation capacity of the hinged brace is 1.4-2.3 times of the rigid connected brace, the energy dissipation contribution of the hinged brace to substructure has increased by 34%-40% compared with that of the rigid connected brace, the maximum residual deformation of the hinged brace is 25.5% of the rigid connected brace, which indicates that the residual deformations are eliminated by the hinged braces basically.