Abstract This paper highlights the structural performance of steel–concrete composite girders strengthened using advanced composite laminates. Nonlinear 3-D finite element models have been developed to investigate the flexural behaviour and load carrying capacity of the girders. The composite laminates comprised carbon fibre reinforced polymer (CFRP) plates and sheets as well as steel reinforced polymer (SRP) sheets. The elastic modulus and ultimate tensile strength of the laminates varied from low to high 60–300GPa and 700–3100MPa, respectively. The nonlinear material properties of the strengthened composite girder components comprising concrete, structural steel beam, reinforcement bars, adhesive and composite laminates were incorporated in the finite element model. The interfaces between the composite girder components were also considered allowing the contact and bond behaviour to be modelled and the different components to retain its profile during the deformation of the strengthened composite girder. Furthermore, the load-slip characteristic of headed stud shear connectors was incorporated in the finite element models based on previous experimental and numerical investigations conducted by the author. The finite element models have been validated against published tests on composite girders strengthened using different advanced composite laminates and having different cross-section geometries, lengths, layers of laminates with different elastic moduli and ultimate tensile strengths, concrete strengths and structural steel strengths. The load carrying capacity of strengthened composite girders, load–vertical displacement behaviour and failure modes were predicted from the finite element analyses and compared against test results. Parametric studies were conducted to study the effects on the load carrying capacity and structural behaviour of strengthened composite girders owing to the change in the composite laminate elastic modulus, number of laminate layers, concrete strengths and structural steel strengths. The study has shown that the increase in the load carrying capacity and ductility of strengthened composite girders due to the increase in steel beam strength is significant with high strength concrete slab. Also, it has been shown that the increase in concrete strength offers a considerable increase in the initial stiffness of strengthened composite girders, while the increase in structural steel strength offers a considerable increase in the stiffness of strengthened composite girder in the post-yielding stage.

Highlights ► Structural performance of strengthened composite girders was highlighted. ► Nonlinear 3-D finite element models have been developed. ► Different advanced composite laminates have been considered. ► Load capacity, load-mid-span deflection and failure modes were predicted. ► Parametric studies were conducted considering different variables.