| As the main compression member and horizontal resistance member of building structure,the shear capacity and deformation capacity of reinforced concrete columns affect the seismic performance of the whole structure.Reinforced concrete columns with high axial compression ratio and small shear span ratio are prone to shear failure.This kind of failure has obvious brittleness,poor ductility,and very difficulty in strengthening and repairing.Therefore,it is necessary to reinforce such members.High Ductile Concrete(HDC)is a new type of material with high toughness,crack resistance and damage resistance.Under tensile and shear loads,HDC has the characteristics of multi-crack development and strain hardening.The HDC is used for concrete structure reinforcement,which is simple in construction,good in effect and has broad application prospects.Therefore,this paper proposes that using HDC to reinforce concrete stub columns to improve their shear behavior.The research content of this paper mainly includes the following aspects:(1)Seven RC columns were designed and fabricated and subjected to pseudo-static loading tests.one of them was reinforced with HDC,three were reinforced with steel mesh and HDC,and the rest were contrastive test specimens,including one reinforced by high performance composite mortar and two unreinforced specimens,including one reinforced by steel mesh and high-performance composite mortar and two unreinforced specimens.The effects of reinforcement method,axial compression ratio and reinforcement ratio on the shear behavior of specimens with HDC jacket are studied.The failure process,failure pattern,load-displacement hysteresis curve,skeleton curve,ductility,energy dissipation capacity,stiffness degradation curve,strength attenuation and performance index of each test piece were analyzed.The test results show that the failure pattern and energy dissipation capacity of reinforced concrete stub columns with HDC jacket can be improved significantly.The shear capacity increases by 38%～51%,and the ultimate deformation increases by 25%～110%.(2)The shearing mechanism of RC stub columns with HDC jacket was analyzed,and the restraining effect of the jackt on existing concrete was studied.Based on the experimental data,the actual utilization coefficient of the steel mesh and HDC jacket was determined,and the relationship between the utilization coefficient and test parameters such as the axial compression ratio was analyzed,and the calculation formula was fitted by Matlab software.Based on the theory of variable angle truss-arch,considering the constraints of the jacket to the existing concrete,the jacket is equivalent to the stirrup,and the calculation formula of the shear capacity of the reinforced concrete column with HDC jacket is proposed.The shear capacity of the specimens in the test and related literatures is calculated by this formula,and the calculated values agree well with the experimental values.Compared with the existing calculation formula of shear capacity of RC columns with HDC jacket,the formula of shear capacity proposed in this paper is more reasonable.(3)Under the action of compression,bending and shearing,the deformation of column specimens is composed of bending deformation,shearing deformation and slip of reinforcing bar deformation,and the calculation models under different states are studied respectively.The stress mechanism of the reinforced specimens was analyzed.The influences of axial compression ratio and stirrup ratio of jacket volume on the deformation capacity of HDC reinforced specimens were taken into account.And based on the experimental datas,Matlab software was used to fit the calculation formula of the section curvature of HDC reinforced concrete columns.According to the deformation calculation model of RC specimens,the deformation of each specimens in yield state,peak state and limit state in this test and related literature are calculated,and the results are in good agreement with the test results. |
PDF Full Text Request