Analysis And Experimental Research On A New Type Of Pre-pressed Disc Springs Self-centering Energy Dissipation Brace

General braces have the disadvantages of easy buckling in compression and asymmetric hysteretic response, and buckling restrained braces exhibit full hysteretic curves and have large energy dissipation capacity, while the exiting large residual deformation after earthquake makes it difficult to be reinforced and repaired, therefore, a new type of self-centering energy dissipation brace is proposed by researchers. Most of these braces adopt shape memory alloys or pre-pressed tendons to offer self-centering ability to return to initial position and reduce or eliminate the structural residual deformations after earthquakes. But shape memory alloys need to be heat treated to realize self-centering ability, pre-pressed tendons have the disadvantage of small elastic deformation, and can not satisfy the ductility demands when step into plastic state. Thus a new type of pre-pressed disc springs energy dissipation (PS-SCED) brace, which utilizes disc springs to supply self-centering capability and friction energy dissipation device to dissipate input energy, has been proposed in this paper. The restoring force, stiffness and deformation demands can be realized by changing the combined form of disc springs, which can satisfies the actual demands of engineering. The hysteretic behavior and functional restorability of PS-SCED brace are studied in this paper, the restoring force model which can portray the mechanical behaviors of PS-SCED braces has been developed, and a series of quasi-static tests of the full scale PS-SCED brace member are carried out. The main contents are as follows:(1) A new type of PS-SCED brace is proposed, and the hysteretic behaviors under low reversed cyclic loads are researched. Based on the changes of stiffness, the bearing force computation method of PS-SCED brace is established, the restoring force model is developed according to the elastic deformation of inner and outer tubes, the bilinear elastic model of disc springs and the ideal elastic-plastic model of friction device;(2) The seismic performances of a full scale PS-SCED brace model with1.2m long under low reversed cyclic loads are simulated using the finite element software. The changing rules of energy dissipation capacity, secant stiffness with its degradation rule and equivalent damping ratio are researched. PS-SCED brace exhibits full flag-shaped hysteretic curves, and the increment of energy dissipation is proportional to the increment of deformation after the first stiffness of brace is turned into the second stiffness, and the secant stiffness decreases stably, the equivalent damping ratio increases. When the energy dissipation is stable, the restoring behavior of the brace makes the equivalent damping ratio decrease. The hysteretic responses of PS-SCED brace is simulated by the established restoring force model under low reversed cyclic loads, and comparisons with the simulated results by solid element model are conducted, results indicate that the hysteretic curves are consistent, and the developed restoring force model can portray the hysteretic behavior of the brace member well;(3) Compressing experiments of the same standard disc springs before and after compression with or without bearing surface are conducted to comparatively study the changes of resilience performance parameters of disc springs before and after compression. It is obtained that the stiffness and energy dissipation capacity of disc springs after compression increase, while compression height decreases. The stiffness of disc springs with bearing surface is bigger than that of disc springs without bearing surface, while the compression height of disc springs with bearing surface is smaller than that of disc springs without bearing surface. The tests of friction devices with non-asbestos organic friction material under the initial scheme with different bolt torques due to low reversed cyclic loads are carried out. The friction device exhibits ideal elastic-plastic performance with full hysteretic curves and strong energy dissipation capacity, and the increment of energy dissipation is proportional to the increment of deformation;(4) A series of quasi-static tests of a full scale PS-SCED brace with1.2m long under the initial condition of same pre-pressed force and different friction forces are carried out. Results indicate that the brace exhibits full hysteretic curves, the energy dissipation capacity increases with the increase of friction force, and the residual deformation occurs when the friction force is bigger than the pre-pressed force of disc springs, but the brace still has a certain self-centering capacity. When the inner and outer tubes are within the scope of elastic deformation, the skeleton curve is bilinear elastic model, which reflects that the brace has good ductility performance and stable energy dissipation capacity. The experiments of ultimate bearing force under low reversed cyclic loads are conducted, results indicate that the compressive bearing force is much bigger than the bearing force of inner or outer tube, also bigger than the tensile bearing force, but the ductility performance in tension is better than that of the brace is in compression. The residual deformation occurs after the inner or outer tube generates plastic deformation, and which increases with the increase of the deformation of brace. When the connecting plate is about to buckling, the residual deformationsare respectively about32%and10%of the maximum deformation of brace when the brace is in tension and in compression, which reflects that the PS-SCED has good self-centering performance.