Study Of The Effect Of Opening On The Behaviour Of Composite Steel-Concrete Diaphragms In Low-rise Steel Structures

The most important function of structural diaphragms is to support and transmit gravity loads to vertical structural elements such as columns. In addition, diaphragms play an important role in collecting lateral loads at specific elevations and distributing them to the lateral resistance system. Thus, in-plane behaviour of diaphragms can be considered for structural analysis and design of structural elements and securing the optimum seismic performance of the structure. In order to investigate structural behaviour of composite steel-concrete diaphragms in low-rise steel structures, one to six storey steel structures with planar aspect ratios of one, three and five with different areas of openings have been analysed by the ETABS code. Results from response spectrum dynamic analysis indicate that the assumption of rigid diaphragms in the studied structures, in particular in the lower floors, is inappropriate. Diaphragms with openings of 20 to 50 percent of area have a flexible behaviour. An opening area of more than 20 percent increases the natural frequency of the structure; hence, necessity for an expansion joint.