Experimental and FE parametric study on continuous steel-concrete composite beams strengthened with CFRP laminates

•Flexural testing of continuous steel-concrete composite beams.•FE simulation of strengthened beams as well as plain beams.•An improvement in the composite action between the strengthened concrete flange and the steel beam.•Higher stiffness and capacity but more reductions in the ductility for the strengthened beams.•A reduction in the fatigue cracks of the steel rebars by extending CFRP laminates through the full length. This study investigates the improvement in the flexural capacity and cracking resistance of continuous steel-concrete composite beams strengthened with carbon-fiber-reinforced polymers (CFRP) laminates at the hogging moment regions. The experimental program involves flexural testing of three specimens in an inverted position under four-point loading to simulate a part of continuous steel-concrete composite beams at the hogging moment region. The experimental findings are used to develop and validate a finite element (FE) model to simulate the nonlinear flexural performance of strengthened beams as well as plain beams. The good agreements between the proposed model and the test data assure an accuracy for the proposed model to predict the influence of various parameters that affect the beam capacity. The CFRP laminates enhance the beam capacity by 18% and 22% when using one and two layers, respectively. Yielding in steel rebars followed by a rupture in the CFRP laminates accompanied by diagonal cracking in the vicinity of supports is the mode of failure for the strengthened beams. To achieve optimum performance of CFRP strengthening, it is recommended that the technique be used for bridges with at least 80% composite action between the steel beam and concrete slab.