Experimental Study On Seismic Performance Of Mid-Rise SRC Shear Walls With Improved Measures On Strengthened Bottom Region

Based on our team's previous experimental research on built-in vertical steel mid-rise SRC shear wall's component: SRCW1~SRCW5, it is found that:Under the impact of cyclic loading, the concrete which lies in the bottom of the compressive zone of the wall, crushed and peeled off, meanwhile the average shear stress of this section increased, which can lead the walls' bottom crack to cut through that causes the walls losing the carrying capacity suddenly. In order to solve the problem that mid-rise SRC shear wall's ductility performs poor under earthquake, Strengthened bottom region structure model is proposed. At the same time the components SRCW11, SRCW12 and SRCW14 are also designed and manufactured. By enhancing the restriction effect of border concealed column region of the wall, the seismic performance of the wall is increased. The above three component tests are compared with SRCW1 and SRCW3 components. The results show that :(1)The constraint effect of two types of steel in the border region on the concrete is not obvious, and the seismic performance of the component can not be improved;(2) Effective improvements were achieved on later stiffness and deformation capacity by constraining bottom concrete of each concealed column region above the foundation with short steel sleeves. Concrete shown better compression performance when constrained by steel sleeves, but such strengthening method had little contribution on energy dissipation capacity of the ordinary SRC wall.For the problems found in the previous study, this thesis has conducted an experimental study on seismic performance of 4 steel reinforced concrete mid-rise shear walls(the shear span ratio is 1.85) with different steel sleeve height, steel sleeve embedded beam, and steel sleeve and built-in type steel, based on the experimental study of bottom strengthened steel reinforced concrete mid-rise shear walls. All specimens were tested under a constant axial load and incremented reversal lateral loading to investigate their seismic performance. Main contents observed and recorded in detail at each loading step include lateral force and displacement at the horizontal loading point, fracture and deformation characteristics at front and back surfaces, displacements and strains at concerned points of the wall.Test results show that:(1)Increasing the height of steel sleeves can change the failure mode of SRC shear walls, at the same time it can improve the ductile deformation capacity and energy dissipation capacity of tested walls effectively;(2) compared to wall specimens with steel sleeves not embedded in foundation,when the steel sleeve confined height of concrete is same, steel sleeve embedded in the foundation without anchorage can improve the ultimate displacement of the shear wall, but can't improve the ductility and energy dissipation capacity;(3) compared to wall specimens with steel sleeves not embedded in foundation,it can increase the horizontal bearing capacity of the wall by adding two short steel in the middle of concrete web, but such measure can't improve the seismic performance of the wall;(4) For the wall specimen with steel sleeve embedded in the foundation without anchorage, when the steel sleeve confined height of concrete is equal to the wall width, experimental results show that concrete failure occurred at the bottom of the wall and at the top of the steel sleeve in the same time. Compared to ordinary SRC shear walls, walls with this kind of detailed design would significantly improve the limit displacement, ductility and energy dissipation capacity under earthquake.