Reliability-based safety map for Howe-type trusses under uncertain Nigerian wind loading

Abstract The current practice in civil engineering is to provide designs with a certain level of safety, which makes it necessary to forecast how a system will perform with minimal or no prior knowledge. These current design methodologies commonly fall short of expectations in unexpected contexts since they are typically only learned via several iterations of trial and error. This study examined the reliability of a typical Howe-type steel roof truss system used for a recently constructed mega-church in one of Nigeria’s main cities. To help the designer determine the expected performance and suitable safety levels for such steel roof truss construction, the design data were applied to the other 11 major cities from the six geopolitical zones in Nigeria. To produce identical policy guidelines to the designer, the dimensional requirements for the roof truss were also reproduced for a span of 12 m, a truss height of 3 m and 28 m, and a height of 5 m in all the zones. For every truss element, a reliability index was developed to measure the structural performance based on the likelihood of failure. The reliability indices were found to be quite sensitive to the size of the steel sections employed. Therefore, as the number of steel sections employed in the design increases, the safety indices, reduce, suggesting an increase in dead loads. Based on the system-level probability of failure of the truss members, contour maps were developed. Therefore, it is advised that the reliability concept be used in the reevaluation of both new and old civil structures.