Study On Seismic Behavior And Design Method Of New Type High Damping Concrete Shear Wall With Concealed Bracings

The high damping concrete has good impact toughness and high damping, which can absorb and dissipate earthquake energy if used in structure engineering, and it is a development direction of the concrete technology. The present vibration and absorption measures are mostly attached the vibration controlling device in structures engineering, which can absorb energy and avoid the premature failures under severe earthquakes, however, it always makes structural design and construction more inconvenient. Based on the studies of high damping concrete and shear walls, A new type of high damping concrete shear walls with steel plate bracing(HDCSW) is proposed in this paper. To improve the economic benefit of anti-seismic, partly high damping concrete shear wall with concealed bracings was proposed. In order to improve the ductility of high damping concrete, high damping ECC materials with ultra-high toughness was used to replace the high damping concrete in shear wall with concealed bracings. The experiment mentioned above and corresponding theory are studied in this paper, and the main contents and results are presented as follows:(1) Two groups of material tests with different mix ratio for ECC is finished, which is constructed of 9 specimens. In addition, the influences of polymer-cement ratio, the polymer mix single emulsion and the polymer mix emulsions on the basic mechanical properties were analyzed. Subsequently, the optimal mixture ratio of the high damping concrete was obtained; the damping tests on nine ECC cantilever beams with different mix ratios were carried out, then the relationship between the damping ratio and deformation of ECC cantilever beams were obtained. Based on these results, some new calculation formula for the damping ratio of the ECC members was proposed.(2) The cyclic loading tests of 2 specimens, one partly high damping shear wall and one partly high damping ECC shear wall, are designed and finished, and the quasi-static cyclic loading test on the two shear walls carried out, the bearing capacity, ductility, energy dissipation, failure characteristics of the two shear walls are obtained. The results show that, compared with high damping concrete shear wall with concealed bracings, partly high damping concrete shear wall with concealed bracings have been reduce slightly on the ultimate bearing capacity, the energy dissipation and the deformation capacity, but it can make the investment cost decline; compared with high damping concrete shear wall with concealed bracings, partly high damping ECC shear wall with concealed bracings on high axial compression ratio have greater the ultimate bearing capacity, stiffness and energy dissipation capacity, and its seismic performance is improved significantly.(3) The seismic tests of 2 high damping concrete coupled shear walls(HDCSW) with steel plate bracing is finished. The failure modes, bearing capacity, ductility, energy dissipation, failure characteristics are obtained. The results shows that, Compared to HDCSW with mixed concealed bracings, HDCSW with steel plate concealed bracings have the greater bearing capacity, stiffness attenuation and energy dissipation performance. In the experiment process, the plastic hinge appears obviously at the end of coupling beams, and then the edge columns at the bottom occurs obviously damaged due to the concrete crushed, which indicated that HDCSW with steel plate concealed bracings have two clear anti-seismic lines. This new type coupled shear walls can improve the anti-seismic performance efficiently, and have a certain practical significance in engineering. This new type coupled shear walls applied in engineering will great helpful for the structures to anti-seismic.(4) Based on the experiment, four-linear skeleton including stiffness degradation for the shear wall with concealed bracings was proposed, which was defined through cracking point, yielding point, peak point and ultimate point. The formula to calculate these points are recommended through theoretical analysis. The results show that, the calculated restoring model agrees well with the experimental result. Finite model of experimental shear walls has been established reasonably by using nonlinear finite element analysis software MSC.MARC and ABAQUS, respectively. The results show that, the simulate results agrees well with the experimental result.(5) The shear-span ratio, axial compression ratio and reinforcement ratio of wall limb are the main influence factors for the shear wall plastic hinge length. Based on the finite element simulation, the single factor influence on the plastic hinge length was studied by regression analysis using software MATLAB. Then, on this basis, an equivalent length of equivalent plastic hinge length calculating model with multiple parameter combination was fitted and proposed. According to the different shear-span ratio and axial compression ratio, the performance goals were obtained by using the experimental results, which can provide reference and basis for the design displacement- based deformation capacity. Then, a displacement-based deformation capacity design method was developed for RC shear walls with an expression for the stirrup characteristic value for a specified drift demand.