# Numerical Investigation of the Collapse of a Steel Truss Roof and a Probable Reason of Failure
###### Abstract  
This study investigated the failure of the roof, with steel truss construction, of a factory building in Tekirdag in the northwestern part of Turkey. The failure occurred under hefty weather conditions including lightning strikes, heavy rain, and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof were studied. Finite element analysis, using the commercial software Abaqus (Dassault Systemes, Velizy-Villacoublay, France), was performed several times under different assumptions and considering different factors with the aim of determining the dominant factors that were responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. In addition, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure. steel truss; roof structure; partial collapse; finite element analysis; lightning strike 0000-0000-0000-0000-00000-00000-00000-00000-00000-00000-00000-000000-00000-000000-00000-000000-000000-000000-000000-000000-00000-00000-00000-000000-  
improve the performance of structures against dynamic loads is to add damping to the structure [20]. Earthqu are not the only sources that cause dynamic loads on structures. One of the main dynamic effects that may lead to sudden or progressive collapses is wind [21; 22; 23; 24]. The wind is a very significant factor that leads to lateral loads to which building structures are relatively more sensitive than they are to vertical loads [25]. A crucial dynamic effect that is a very complicated phenomenon is lightning strike [26]. A lightning strike can cause partial damage or complete failure of structures [27; 28]. Specifically, there are cases where the main reason reported for structural failure is lightning strike [29; 30; 31; 32]. In Australia, it is reported that 21% of insurance claims for damage to buildings are caused by lightning strikes [33]. A lightning strike can affect a structure in many different ways, with the two most dangerous processes being blast (local and rapid pressure oscillations) and heating [34]. Previous research proved the heating effects of the lightning strike phenomenon [35; 36]. It is known that a lightning strike increases the temperature rapidly in a very short period of time [29; 37]. The electric current that is caused by the lighting strike heats up the structure so that it can start fires [38]. Besides, fire alone can also be the main factor that leads to structural failure [39; 40; 41; 42]. Lightning is one of the key points of this study. Of course, structures are not affected just by one of the consequences of the lightning strike phenomenon. Instead, the combination of these enumerated parameters creates a synergy effect, which increases the resultant influence of the factors so that the combination becomes greater than a superposition of these contributing load components [43]. The effects of a lightning strike can be even more dramatic on the structures when there is accumulated water on top of the structure, since the local blasts are amplified by the presence of the water and thermal changes influence the structure [34; 44]. There are different types of failure mechanisms as well as different types of reasons for the collapse. Thus, it is possible to find possible reasons for the failure just from the mode/form of the failure. One of the most important types of failure mechanisms is fatigue [45]. Fatigue may lead to the progressive collapse of structures [46; 47]. Progressive collapse may happen instantly following the changed load distribution of members due to buckling and/or failure of some members [48; 49]. However, it does not have to happen at the time of the initial failure of individual members but can happen after a certain number of members have failed successively [50; 51].