Estudo teórico-experimental de parafusos utilizados como dispositivos de transferência de carga em pilares mistos tubulares preenchidos com concreto

Abstract

The recent published standard titled Design of steel and composite structures for buildings using hollow sections (Brazilian Standard ABNT NBR 16239:2013) recommends the application of bolts as shear connectors in concrete-filled composite tube columns. This technical investigation presents a preliminary theoretical and experimental study on the behavior of these shear connectors, as well as analyzes the load transfer between the steel tube components and the concrete core. For this particular study, two test configurations are proposed: push-out-BA (bases of the steel tube and concrete core are supported) and push-out-BL (only the concrete core is supported). Two welding procedures for the junction between the shear connectors and steel tube are also analyzed: spot and effective welding. The experimental tests follow the procedures for standard push-out test recommended by the European standard for composite steel and concrete structures (EN 1994-1-1:2004), with a centralized loading being applied to the steel tube. The theoretical study was carried out through numerical simulation using the finite element method. In these simulations, the material geometrical nonlinearities and physical nonlinearities are considered. Two alternatives are proposed to determine the experimental ultimate load. The first alternative is more conservative as compared to the analytical model of ABNT Standard NBR 16239:2013, while the second alternative presented results closer to the values expressed by the ABNT standard. For both the experimental and numerical analysis, the concrete core rupture was observed as one of the main failure modes.