Modeling of RC Shear Walls Retrofitted with Steel Plates or FRP Sheets

Abstract

Advancements in the nonlinear finite-element method have resulted in reliable simulations of response for reinforced concrete (RC) structures, provided that an analysis program with comprehensive models for material and structural behavior is employed. However, a need to provide simple, yet adaptive modeling guidelines for engineers and researchers using these tools exists, specifically for structures retrofitted with external materials for which bond behavior with the existing concrete surface is critical. Nonlinear analyses were conducted in this study to provide modeling procedures that can satisfactorily replicate the response of retrofitted RC shear walls. The retrofitting strategies included bolting of steel plates, bonding of external steel plates and fiber-reinforced polymer (FRP) sheets, and addition of steel plates with delay mechanisms. The modeling used simple rectangular and triangular membrane elements for concrete with smeared internal reinforcement, truss bar elements for external steel and FRP retrofitting materials, and bond-link elements for the bonding interface between steel and FRP to concrete. Critical to the success of the analyses was the development of constitutive bond-slip models for the link elements to simulate slotted steel connections, which function as a delay mechanism, and for anchorage of FRP sheets to concrete foundations. The analyses satisfactorily simulated seismic behavior, including lateral load capacity, displacement capacity, energy dissipation, hysteretic response, slip between the retrofitting material and the concrete structure, and failure mode.