Progressive Collapse Analysis of Steel Framed Structures with I-Beams and Truss Beams using Linear Static Procedure

ABSTRACT: Progressive collapse starts with a local damage or loss of some members of the structure leading to failure at large parts of a structure. Due to the recent disastrous events like world Trade Center in USA, taking measures in reducing the potential of progressive collapse (PC) of structures during the analysis and design stages is becoming a necessity for the structures. A number of computational analysis programs, such as ETABS, SAP2000, ABAQUS can be used to simulate the structures and look into their potential of PC and also how to improve their design against PC. This study investigates the potential of progressive collapse in steel framed structures using normal I-beams and truss beams in their floor systems. For this reason two steel framed buildings are considered having floors with normal I-beams and truss beams of 9 m,12 m and 15 m spans to investigate the effect of increasing the span of the beams onto the potential of progressive collapse of the buildings. General service Administration (GSA) guidelines with linear static procedure is used for the analysis of the above mentioned buildings and as a result of the analysis Demand Capacity Ratio (DCR), deflections and steel weights were also compared. Results indicate that due to column removal of all the frames with normal I-beams spanning 9 m,12 m and 15 m have higher potential of PC than the frame with truss beams since the additional loads are distributed onto the truss vertical and diagonal members. Furthermore, vertical displacement of the normal I-beams is also more than the truss beams. When 12m and 15m beam spans are considered buildings with truss beam floors have less steel weight than those with normal I-beam floors. However, when 9m beam spans are used then the case is opposite. In the long side of the buildings generally the truss beam members manage to absorb the additional loads created by loosing a main column member. In the short side additional vertical bracings are used to reduce the DCR values below the acceptable limits of GSA. Keywords: Progressive collapse, truss beam, normal I-beam, steel structure, linear static procedure. …………………………………………………………………………………………………………………………