Numerical prediction of the shear response of semi-prefabricated steel-concrete trussed beams

In this study, the shear behavior of hybrid steel-trussed-concrete beams (HSTCBs) realized with prefabricated steel trusses embedded into a concrete core cast in situ, is investigated by means of Finite Element (FE) numerical simulations. HSTCBs do not behave as classical RC elements nor composite beams. Up to now, there are not specific design criteria in the building codes and the calculation of this type of beams is conducted by means of design-by-testing procedures. The knowledge of the material behavior as well as the understanding of the interaction between materials in contact is the first requirement for the definition of proper design procedures and calculation methods for practitioners to be inserted in the international building codes. In the present study, the numerical simulation of the global beam behavior through the modeling of the local material response and contact properties, allow a detailed knowledge of the shear resisting mechanism aimed at the definition of simplified calculation formula. The accuracy of the numerical prediction is validated against the results of a reference experimental campaign of three-point bending tests with shear failure carried out by the author in a previous work. A first analytical approach for the interpretation of the FE results is conducted applying the variable strut inclination method currently prescribed in Eurocode 2 for classical RC beams. Conversely, in the paper it is shown how all information coming from the FE analysis are of paramount importance for the possible development of more proper simplified calculation methods of the shear capacity of this particular beam typology.