Investigation of buckled truss bars of a space truss roof system

Abstract

Some bars of space truss roof a major shopping market chain in Adana, Turkey have experienced flexural buckling without any circumstance of overloading induced by snow and rain together with wind that has led to the buckling phenomenon. However, according to the on-site geotechnical surveys that have demonstrated that an increase in consolidation settlement of foundation soil has occurred, it has been realized that differential support settlements may cause the truss bars to buckle. This paper investigates the probable cause of the buckling phenomenon observed in some truss bars based on the soil condition. For this, a photogrammetric survey has initially been performed to determine the existing vertical position of the roof supports located on the top of the cantilever columns. To obtain the amount of settlements of the supports, initial vertical coordinates of the tips of the columns that were determined before assembling of the roof are subtracted from those obtained by the photogrammetric measurement with respect to the reference point. An observation has also been made in site to visually inspect the distribution pattern of the buckled truss bars. A 3D analytical model of the roof has been developed to understand whether or not the buckling failure of the truss bars is resulted from the soil settlement under the individual foundations. When the observed distribution pattern of the buckled truss bars is compared to that obtained by the nonlinear analysis, a reasonably good agreement has been achieved, which shows that the truss bars have buckled because of the effects caused by differential settlements among the individual foundations due to increase in consolidation settlement occurred within the soil that surrounds the structure.