Nonlinear Seismic Response Analysis Of Reinforced Concrete Buildings Including Effects Of Masonry Infill Walls

Multi-storey reinforced concrete frame structure is widely used in the construction of a structure. On the "5 ? 12" Wenchuan Earthquake, different types of frame structures suffered damages in different degree. According to the post-earthquake field investigation, it shows that most of the major structures of frameworks suffered much less severe damage because of possessing reasonable and astigmatic infill walls and the damage mainly occurred in the maintenance structure and infill walls. However, some frameworks received severe damage or even come to collapse because of unreasonable building of infill walls.In this paper, a framework of a typical five-storey commercially residential structure is selected as the prototype of calculation. Through the analysis and discussion of various infill walls calculation models, the equivalent strut stress - strain relationship is established, which can be applied to the three-dimensional non-linear analysis using software OpenSees. At the same time, for the realization of multi-space structure of multi-span three-dimensional nonlinear analysis, SAP2000 is used to establish the structure model. Through the conversion program, the model parameters are transformed into Tcl format and the OpenSees-term non-linear response analysis can be applied by using the text of that format. Three models of the pure framework, complete infill framework and weak bottom framework are established and their dynamic responses are compared, from which the following conclusions can be gotten:The stiffness effect of infill walls exerts an important impact on the natural period and frequency. Combined with the computational examples in this paper, we found that the complete infill wall possesses 0.44 cycle time of pure framework structure. According to the present standard, we can only approximately size up the impact of infill walls upon the structure period by using the same cycle decreasing coefficient. But the impact of materials and layout of infill walls cannot be considered enough.If the infill walls are reasonably and evenly arranged, the lateral stiffness of the structure will be large and deformations at all levels will be small. The maximum story drift ratio is 1/213 under the Dayiyingping ground motion which is adjusted to the peak acceleration at 0. 80g. Compared with the pure frame, the seismic capacity of the structure considered the impact of the infill walls is significantly increased, which showed that the infill walls has a beneficial effect on the anti-seismic behavior.Weak structure of the underlying section under the action of an earthquake, due to the infill wall's contribution of lateral stiffness to middle and upper part of framework, the middle and upper's inter-layer deformation decreases, but as to the lower layer (Especially for the bottom), it becomes fragile because of the existence of middle and upper infill walls, and the inter-layer deformation hugely increases. When input ground motion takes on the wave of Taft with the peak value 0.80g, the biggest story drift angle of the bottom weak structure is 1/57, which brings about bigger inter-layer deformation in comparison with the pure framework with the same input ground motion. The weak layer deformation is the major factor to determine the structure's earthquake damage. The infill wall exerts a negative effect on the anti-seismic function with the unreasonable layout of it.Finally, based on the Wenchuan Earthquake spot damage examples, types of the damage of the infill walls and frameworks are analyzed and the advice about how to deploy the infill walls when designing and reinforcing the infill walls is put forward.