Reliability analysis of steel roof trusses subjected to wind loads

The main aim of this investigation is determination of system reliabilities of roof trusses of an industrial structure located in the coastal region, and subjected to extreme wind loads. Two, commonly used types of trusses, namely, Howe and Pratt trusses, are considered. To study the effect of cross-section shape of the member on the reliability of truss, two types of cross-sections (nomely, angle and tubular sections are considered. The reliabilities of these trusses are estimated using Betg-unzipping method. A parametric study is undertaken to determine the effects of changes in coefficient of variation of resistance and load on the system reliability. To examine whether an optimised truss is safe with respect to the reliability considerations, reliabilities of two optimised trusses have been determined. Based on the results obtained from the studies carried out the points that emerged are; (i) from the comparisons of system reliabilities of the two types of trusses considered (convering the same span and subjected to same loading) it is noted that Howe truss is more reliable than the Pratt truss, (ii) from system reliability point of view, trusses with tubular cross-section members perform better than those with angle crass-section members, and (iii) weight optimised trusses need not possess the required safety and hence, target reliability index should be included as one of the constraints in the optimisation.