Nonlinear finite element analysis of composite RC shear walls

Composite Reinforced Concrete (RC) wall system refers to a cantilever composite wall, where steel or Fiber Reinforced Polymer (FRP) components are embedded in or attached to an RC wall. The results of an analytical and parametric study on the effectiveness of using externally bonded steel plates and FRP sheets on RC shear walls as a retrofit technique so as to improve their seismic behavior have been investigated in this paper. Calibration and verification of a base RC wall has been done by comparing the results of the finite element model and also the experimental model. Analytical results are used to evaluate the capacity curves (Load-Displacement relationships) of strengthened RC shear walls. Analysis results of a model with an optimized thickness of a steel jacket instead of an over-hanging part of the boundary element show the ductile behavior of a strengthened wall close to the behavior of the base RC wall with boundary elements; this achievement would lead to the theory that steel jacketing could be an alternative for the boundary elements of RC shear walls. The application of externally bonded Carbon Fiber Reinforced Polymer (CFRP) sheets is an effective seismic strengthening procedure in order to improve the behavior of reinforced concrete shear walls. In the retrofit method, using CFRP sheets, the flexural and shear strength would be increased by applying the CFRP sheets with the fibers oriented in the vertical or horizontal direction. The carbon fiber sheets are used to increase the precracked stiffness, the cracking load (up to 35%) and the ultimate flexural capacity (up to 18%) of the RC walls. Finally, a wrapped CFRP sheet around the plastic hinge area of the RC wall in parallel with boundary elements, provides not only enough shear strength, resulting in a ductile flexure failure mode, but also the confinement of concrete in the plastic hinge leads to an increase in the ductility of the RC wall.