NONLINEAR FINITE ELEMENT ANALYSIS OF FLANGED RC SHEAR WALLS BASED ON MULTI-LAYER SHELL ELEMENT

Nonlinear simulations for structures under earthquakes have been widely focused on in recent years. However, precise modeling for the nonlinear behavior of reinforced concrete shear walls, which are the major lateral-force-resistant structural member in high-rise R.C. buildings, still has many items to be investigated. In this paper, based on the principles of composite material mechanics, a multi-layer shell element model is proposed to simulate the in-plane bending and the coupled in-plane bending-shear nonlinear behaviors of RC shear wall. The multi-layer shell element is made up of many layers with different layers of thickness, and different material models (concrete or rebar) are assigned to various layers so that the structural performance of the shear wall can be directly connected with the material constitutive law. Besides the traditional elasto-plasticfracture constitutive model for concrete, which is efficient but does not give satisfying performance for concrete under complicated stress condition, a novel concrete constitutive model, referred as microplane model, which is originally proposed by Bazant et al., is developed to provide a better simulation for concrete in shear wall under complicated stress conditions and stress histories. Three flanged shear walls under static push-over load were analyzed with the proposed shear wall model for demonstration. The simulation results show that the multilayer shell elements can correctly simulate the in-plane bending failure for tall flanged walls and the coupled in-plane bending-shear failure for short flanged walls. In addition, with microplane concrete constitutive law, the behavior and the damage accumulation of flanged shear wall can be appropriately modeled, which is very important for the performance-based design of structures under disaster loads.

Keywords:

flanged shear wall , nonlinear analysis , microplane , multi-layer shell element