A new method for rapidly capturing the strength and full nonlinear response of partially interacting steel-concrete composite beams

A semi-analytical procedure is presented for predicting the complete flexural response of partially interacting steel-concrete composite beams up to failure. The governing equation of the Euler-Bernoulli beam theory is solved wherein concrete, steel and the shear connectors joining the concrete slab to the steel beam are assumed to have nonlinear stress-deformation relationships. The adopted constitutive relationship for the connectors allows for partial or full composite action. The solution is applicable to beams and one-way slabs subjected to concentrated or uniform load and/or their combination. The governing equation is numerically solved by satisfying the equilibrium and compatibility requirements along the member. For the reinforced concrete part of the composite beam, a nonlinear moment-curvature relationship is developed that accounts for concrete nonlinearity in compression and for cracking and tension-stiffening in tension as well as for steel reinforcement nonlinearity. The steel profile is assumed to have a bilinear elasto-plastic strain-hardening moment-curvature relationship. Comparison of the proposed model results with the corresponding experimental load-deflection curves and interfacial shear-slip curves of several beams tested by others shows good agreement. The relative simplicity, efficiency and easy application of the present solution make it possible to accurately predict the failure load, interfacial slip and full nonlinear response of partially interacting composite beams.