Incorporation Of Modified Compression Field Theory Model Into An Nonlinear Laminated Reinforced Concrete Shear Wall Element

As main defense of high-rise buildings to resist lateral force, much energy will be consumed by shear wall when structures meet with strong earthquakes, for what reasonable design and layout will remarkably improve the ductility of structures. Multi-dimensional constitutive model of concrete or choice of element model and so on, must be fully considered in simulating the mechanical behavior of shear wall, however, mature nonlinear finite element model for shear wall has not been formed so far, it is necessary to study on nonlinear finite element model for shear walls as a result.First of all, study on development history of nonlinear finite element model for shear wall has been carried out, common models are classified and summarized, and inherent tendency of the development of these models has been expounded. From the viewpoint of applicability and development progress, the layered shell element model is chose as the first focus of this article. Based on relative finite element theory, layered shell element model has been built up and integrated in programming platform by c++language, which is based on shell element ShellMITC4 in OpenSEES. Basic frame of layered shell element is constructed, emphatically from the establishment of the unit displacement mode shape function, the unit matrix of integration, interface of material and element stiffness matrix, etc. Functions of stratification and calculating on section stiffness and resilience are added to the element. Assumption on shear strain field and dealing with drill degree save layered shell element from shear locking and spurious mode, the calculation precision of layered shell element coupled is checked compared with OpenSEES, which is finally integrated on finite element analysis platform.Another study priority is integration of two-dimensional constitutive model for concrete material, which will join with layered shell element in finite element analysis platform. MCFT is a smeared rotated crack model based on total loading and integral model, whose elastic matrix is made up by secant modulus. Constitutive model for concrete material and smeared rotated crack model can be applied to nonlinear layered shell model, and secant modulus is replaced by tangent modulus in consideration of low speed of secant iteration method in nonlinear analysis. In addition, smoothing process is taken into tension for concrete to reflect negative stiffness phenomenon in softening stage and improve the stability of the numerical calculation at the same time, which results in smooth transition of stiffness.It is found that nonlinear layered shell model makes good performance in simulating shear wall structures compared with test results. Smoothing in tension is helpful to improve the stability of shear wall model in nonlinear time history analysis. Stability is not only influenced by solver, load control and stability of model can also cause big problems. However, there is still much room for shear wall model, such as nonlinear constitutive of resisting shear force, improvement on calculating method, complex hysteresis characteristics of concrete materials, etc. which are significate for the development of numerical simulating of shear wall.