Research On Mechanical Behavior And Ultimate Axial Compression Ratio Of T-Shaped Short-Leg Shear Walls

Short-leg shear wall structural system is a new-style structural system developing in practice, and owing to the flexible layout, low cost and good building function, short-leg shear wall structural system is widely used in high-rise residence structures. Because of reasonable structure type and good mechanical behavior, T-shaped short-leg shear walls are widely used in short-leg shear wall structural system. Although short-leg shear wall structural systems are widely used, the relevant design codes and theoretical study are both lagging behind the engineering practice. Through studying mechanical behavior and ultimate axial compression ratio of T-shaped short-leg shear walls, the reasonable mechanical model is established, and the design theory can be perfected, as well, it can provide guidance for the theoretical study of short-leg shear walls with other section forms. Based on the above research purposes, this paper mainly completes the following work:Ⅰ. Research on calculation theory for the shear lag effect of T-shaped short-leg shear walls. Firstly, the vertical displacement of the flanges of T-shaped short-leg shear walls is simplified to three parts:shear lag warping displacement, plane section bending displacement and axial displacement. The shear lag warping displacement is assumed as the cubic parabola distribution along the flange, and based on the minimum potential energy principle, the differential equations are deduced; with the deformation and force boundary conditions, the calculation theory for the shear lag effect of T-shaped short-leg shear walls is established. Based on the relevant design codes, eight T-shaped short-leg shear wall models are designed. The vertical stresses of the flanges of the eight models are obtained by the calculation theory for shear lag effect and the finite element calculation software respectively, and the analytical results and the FEA results are compared and analyzed. At last, the parameter analysis is carried out based on the calculation theory for shear lag effect, and the influence of shear force, shear span ratio and height-thickness ratio of cross section on the shear lag coefficient of T-shaped short-leg shear walls is obtained. Research shows that:the analytical results are in good agreement with the FEA results, and each parameter has different influence on the shear lag coefficient.Ⅱ. Calculation theory and test verification for skeleton curve of T-shaped short-leg shear walls. The moment-curvature skeleton curve of cross section, and the force-displacement skeleton curve of T-shaped short-leg shear walls, are both simplified to four lines represented by four reference points:the cracking, yield, peak, and ultimate points. Based on traditional flexural theory and plane section assumptions, considering the effect of the constraints in the end-zones on the values of the peak and ultimate points, a theory for calculating the four reference points of moment-curvature skeleton curve is established. Based on the four reference points of moment-curvature skeleton curve, a theory for calculating the four reference points of force-displacement skeleton curve of T-shaped short-leg shear walls is established. Based on the equations in this paper, self-made programs are made to obtain the force-displacement skeleton curves precisely through inputting section size, reinforcement form and material properties. To validate the accuracy of the theory, some examples of analyses in the relevant literature are used to compare the analytical values with the test values. Research shows that the analytical results are in good agreement with the test results, and they can provide references for performance-based seismic analysis and design of T-shaped short-leg shear walls.III. Research on ultimate axial compression ratio of T-shaped short-leg shear walls. Based on the plane assumption, the calculation equations of ultimate axial compression ratio are derived with the known condition that the normal section of T-shaped short-leg shear wall is in critical reinforcement, and the influence of constraints in the end-zones on ultimate axial compression ratio is considered. Based on the derived equations, the influence of section dimensions, height-thickness ratio, constraints and reinforcements in the end-zones on ultimate axial compression ratio is researched respectively. Aiming at the fact that T-shaped short-leg shear walls have lower ultimate axial compression ratios, some design suggestions are put forward. Research shows that:each parameter has different influence on ultimate axial compression ratio, and ultimate axial compression ratio can be increased by tuning the parameters.