Experimental Research On Seismic Damage Performance Of Steel Reinforced Concrete T-shaped Columns

Steel reinforced concrete(SRC) special-shaped columns structure, making better use of available space and improving the esthetic appearance of structure, is a kind of mechanical system with the combination of power and beauty. Because of steel embedded in the section of special-shaped columns, the bearing capacity and the ductility capacity of special-shaped columns can be improved and the structure weight can be reduced. Due to these advantages, special-shaped columns win the favor of proprietors and developers.This paper mainly discusses the damage evolution rules of SRC T-shaped columns. 10 specimens with different axial compression ratio and shaped steel ratio are tested under horizontal low-cyclic reversed loading by adopting the loading device of parallel four-linkage. Lateral load-displacement curves, skeleton curves, the regularity of strength deterioration and stiffness degradation, the capacity of deformation and hysteretic energy are obtained after different loading processes. Meanwhile, by analyzing and summarizing the process of destruction from a damage point of view, conclusions can be drew as the following: characteristic of flexural failure appeares when SRC T-shaped columns with a shear span ratio of 2.5 are damaged with the applied load along the web. The hysteretic curves of specimens are plump and symmetry. Ductility factors are greater than 3.5 and the ultimate elastic-plastic story drift angles are between 1/36 and 1/9. After different loading cycles and displacement amplitudes, the ultimate deformation capacity of T1, T2 and T3 decreases by 10.09%, 18.54% and 28.23% compared with T1 and the ultimate energy dissipation capacity also decreases in varying degrees under monotonic loading. Adopting variable amplitude cyclic loading can increase strength deterioration while adopting constant amplitude cyclic loading is much better in energy dissipation capacity.Results of simulation by using the finite element software Open Sees are analyzed and compared with testing results. Study shows that the positive and negative load-displacement curves of simulation are symmetry well which conforms to the boundary conditions of ideal consolidation at both ends. Meanwhile, simulation curves are consistent with testing curves well which can provide strong support for the subsequent chapter to establish the damage model.The defects of existing damage models are summed up and based on the testing results of SRC T-shaped columns, a nonlinear damage model of maximum deformation and accumulated energy dissipation is established by considering the influence of loading cycles and displacement amplitude to the ultimate deformation and capacity. This model can well describe the damage evolution rules of SRC T-shaped columns. At the same time this paper also analyzes the relevant parameters of the damage model and the corresponding expressions are presented. Through calculating the damage index of specimens, combined with the test phenomenon, the damage process of SRC T-shaped columns can be divided into five stages with the corresponding damage index respectively as follows: undamaged(0-0.05), slightly damaged(0.05-0.25), stably damaged(0.25-0.55), seriously damaged(0.55-0.85) and totally damaged(?0.85).Research results above will supply the theory support for the seismic damage assessment and the reinforcement of SRC T-shaped columns and lay the theoretical foundation to establish the damage evolution and destruction rules of SRC special-shaped columns from a low-order dimension to a high-order dimension.