Flexural and shear capacity of composite steel truss and concrete beams with inferior precast concrete base

The paper presents a set of 24 lab tests on 12 composite steel truss and concrete beams with inferior precast concrete base completed by second phase concrete cast. The experiments investigate the shear and flexural strengths of the beams with different depth, width and transverse reinforcement inclination. The beams failure modes are studied focusing on the crack patterns and on the interaction between concrete cast at different times. The obtained results are compared with theoretical evaluations of typical resisting mechanisms of steel-concrete composite and reinforced concrete structures using updated European and American design Standards. The main features of the composite steel truss and concrete beams are quantitatively and qualitatively discussed.

► We present the results of 24 tests on composite steel truss and concrete beams.
► No notable sliding between concrete base and topping is detected in flexural tests.
► At the ultimate shear strength the cracks appear wider than in ordinary RC beams.
► International Codes formulas adequately capture the beam flexural strength.
► Transverse bars are effective connector between concrete cast at different times.