Étude expérimentale du comportement sismique des assemblages utilisés dans les contreventements en X en acier

Concentrically X-bracing is frequently used to resist lateral loads in steel structures. Hollow square sections (HSS) and back-to-back angles are often used for these braced frames. In this case, one diagonal is continuous and the second one is discontinuous. A mid-connection detail is then achieved at the intersection point by inserting a plate through the continuous diagonal and by using transfer plates at the ends of the discontinuous diagonals. The discontinuous brace segments are then bolted to the through plate. The aim of this research project is to study the behaviour of these connections, especially their stability response when subjected to compressive loading. Seventeen tests were performed on full-scale X-bracing specimens in the vertical frame at École Polytechnique de Montréal. HSS and back-to-back angles sections were used for the braces. The bracing members and their connections were sized according to the requirements of the Canadian standard of steel structures (CSA S16-09). Two connection's configurations were tested: single shear and double shear. For single shear connections, the load transfer is done using a single plate inserted in the braces. The configuration is eccentric. For double shear connections, the load transfer is done by means of two plates inserted in the brace; in this case, the configuration is concentric. In addition, two modified connections were tested; one where a stiffener was added to a single shear connection and one where the transfer plates were replaced by double angles welded to the HSS braces.