3D Continuum MDOF Model For Seismic Analysis Of Wall-frame Structures

Since wall-frame structure is one of the most commonly used form in high-rise buildings, so performance-based seismic analysis of wall-frame structures has great application value and economic value for disaster prevention. At this moment, the Increamental Dynamic Analysis (IDA) which base on nonlinear time history analysus is one of the accurate methods. Because the number of real structural members is huge, it is time comsuming to to carry out nonlinear dynamic analysis, which limits the applications of nonlinear dynamic analysis in practical engineering,. So it is urgent to explore a kind of reasonable and easy simplified calculation method for wall-frame structure to meet the engineering requirements and to be accepted by the majority of engineers. The 2D comtinuum MDOF model can only be applied to structures with regular plan and the torsional displacement is neglected. However, torsional behavior can not be ignored in most of the buildings and torsion is one of the major factors leading to the destruction of the building. Therefore, this paper proposes the three-dimensional continuum simplified model to consider the effect of torsion. For this purpose, the main contents of this article include the following aspects:(1) The theoretical study for the simplified nonlinear analysis model of frame-shear wall structure. The proposed MDOF model maintains the use a combination of flexural cantilever and shear cantilever to represent a wall-frame structure.Based on the continuous method, the backbone curve of flexural cantilever and shear cantilever are obtained using the detail information of wall’s cross-section and design wind loads, the total flexural stiffness and the total shear stiffness in both X and Y directions are also obtained respectively. Tthe total shear stiffness is distributed to every single-bay frame according to the their shear stiffness which is based on shear strength principle. Based on the theoretical study, this paper proposed and describes the process to develop the simplied analysis model(2) The verification study of simplified analysis models is carried out. To discuss the accuracy of simplified models, a 15-story asymmetric frame-shear wall structure was chosen as the example, pushover analysis and nonlinear incremental dynamic analysis were conducted by software OpenSees. The results indicated that, the continuum MDOF model produce good estimates of the shear force of shear wall, story drift and torsion angle of simplified models compared to those of detailed model.(3) The parametric study of simplified models is conducted. Some parameters in the process of developing model, such as a, shear yield strength and static eccentricity are selected to conducted parametric analysis. The results show that the affect of a on the value of seimic displacement is small under low intensity earthquake,which will increase when the intensity of earquake increases. Changes in the yield shear force does not affect the structure elastic stiffness in the capacity spectrum curve, but will affect the value of the yield base shearforce.It has no significant effect on the seismic displacement.Torsion angle is increasing with the increasing of static eccentricity and PGA.(4) The results show that the proposed simplified nonlinear analysis model having the advantage of simplicity, efficiency, and cccuracy. When reinforcement data of shear wall and design wind loads were input for modeling, the seismic performance for frame-shear wall structure can be assessed preliminarily, which is of practical value in engineering.