Innovative design of FRP combined with concrete: long-term behavior

The time-dependent behavior of a new class of hybrid elements consisting of glass-fiber-reinforced-plastic (GFRP) box beams combined with a layer of concrete in the compression flange and a carbon-fiber-reinforced-plastic laminate (CFRP) as additional tension reinforcement is presented in this study. Shrinkage, creep, and fatigue models for concrete are combined with creep and fatigue models for GFRP (based on both laminate theory and semiempirical approaches) to yield a general analysis procedure for predicting the deformation and residual strength response of hybrid GFRP/CFRP/concrete beams subjected to sustained and/or alternating loading. The analytical model predictions are compared with experimental results obtained from creep and fatigue testing of large-scale members, giving very good agreement. The present study shows that the new hybrid beams possess very good time-dependent response characteristics, and the models described here, along with those given in the companion paper for short-term behavior, can be used as analytical tools for the optimum design of such members under both short-term and long-term loading actions.