Experimental Study On Seismic Performance Of Mid-rise Concrete Shear Wall With Built-in Vertical Steel

Composite steel-concrete shear wall – SRC shear wall- has been widely used in plenty of high-rise buildings. In recent years, a new type of composite shear wall has been developed in engineering applications, which encased vertical steel elements both in the end and middle of wall section. Compared with ordinary SRC shear wall which encases vertical steel elements in the end of wall section only, the vertical steel elements encased in the middle of wall section can reduce the calculated axial compression ratio effectively. Therefore, the additional steel elements encased in this new type of shear wall can reduce the design axial compression ratio, which is a critical requirements in design codes. In engineering applications, the steel elements which encased in the middle of wall section were applied only for reducing the design axial compression ratio, not for improving the shear capacity, ductility etc of walls. At present, there are rare research reports on the mid-rise concrete shear wall with built-in vertical steel elements at home and abroad, the seismic performance of this new type concrete shear wall was not clear enough, therefore, studing on mid-rise steel concrete shear wall with built-in vertical steel elements has important theoretical significance and engineering application value.In this thesis, the research work on seismic performance of mid-rise SRC shear wall with built-in vertical steel was conducted by means of quasi-static tests of scaled model walls. The main research objective is on the seismic performance of model walls which varied by following factors: setup of encased steel elements, the loading mode, the axial compression ratio. Five shear wall specimens were designed in this test, which had following features: the concrete strength is C40, the aspect ratio is 1.85, the test axial compression ratio is from 0.12 to 0.225, the design axial compression ratio is from 0.258 to 0.509. All the shear wall specimens were tested by quasi-static cyclic horizontal loading except SRCW2 which was tested by monotonic horizontal loading. The axial load was applied by a vertical hydraulic jack and a pressure distribution beam, the horizontal pushing and pulling loads were applied by a horizontal hydraulic jack; the mixed loading scheme was applied to test control, which composed of force control stage before concrete crack has been observed in specimens and displacement control stage after concrete crack has been observed in specimens. During test, the vertical and horizontal deformation of two vertical sides and horizontal displacement of the loading point in the wall were monitored by using a series of displacement transducers. The strain of steel elements, vertical reinforcement bars and horizontal reinforcement bars were monitored by using strain gauges and rosettes. During each loading step, the wall damage, crack distribution and development were observed, recorded and taken photographs carefully.The results of tested model walls were processed and analyzed after the test been finished, which include the related curves of loading force versus displacement at the loading point, the deformation of wall and the strain of steel elements and reinforcement bars. Analysis results can be summarized as follows:(1) when using different loading mode, the specimens have almost same horizontal load capacity, energy dissipation capacity, stiffness and ductility;(2) if axial compression ratio increased, the horizontal load capacity, energy dissipation of specimen become larger;(3) compared to the SRC shear wall with vertical steel encased in the end of the wall section only, walls with vertical steel elements encased in the middle of the wall section show no enhancement in the horizontal load capacity, energy dissipation capacity, ductility and stiffness;(4) the strain at the bottom of the shear wall are basically complied to linear plane section assumption;(5) neglecting influence of the middle vertical steel elements in the analysis, the results of flexural bearing capacity calculation formula of code based on linear plane assumption and OpenSEES based on fiber wall section are coincident with the test results.