Damage model for FRP-confined concrete columns under cyclic loading

In structural engineering, seismic vulnerability reduction of existing structures is a crucial issue. External reinforcement with fiber-reinforced polymer (FRP) holds interest in achieving this aim. Its use as a retrofitting method is limited, however, for a number of reasons, including the lack of numerical tools for predicting cyclic loading. This paper presents a simplified stress–strain model suitable for monotonic and cycling loading capable of predicting the FRP’s effect on reinforced-concrete columns. The model was inspired by two well-known concrete constitutive laws: one based on damage mechanics (La Borderie’s concrete-damage model, 1991); the other on extensive experimental studies (Eid and Paultre’s confined-concrete model, 2008). Validation is provided using experimental results on reinforced concrete columns subjected to axial and flexural cyclic loading. The proposed approach also deals with steel-bar rupture, considering low-cycle fatigue effects. All the simulations were conducted with multifiber Timoshenko beam elements.

► A new damage model for FRP-confined RC columns under cyclic loading.
► Experimental validation on retrofitted columns subject to cyclic loading.
► Capacity increase and hysteretic behavior of the model are well reproduced.
► Ignoring low-cycle fatigue of steel bars can lead to overestimating capacity.
► Numerical modeling is performed using a multifiber beam finite element strategy.