Structural performance of modern roofs with thick over-purlin insulation - Experimental investigation

In conventional roof and purlin systems, it is generally known that the roof cladding restrains the purlins from lateral buckling. However, during the past recent years, the requirement of increased insulation thickness for energy saving has led to a proliferation of roof systems and fixing methods for industrial-type buildings in the UK. The modern roofs are likely to behave differently in their interaction with the purlins compared to conventional trapezoidal sheeting with relatively thin insulation. At worst, the restraint provided to the purlins by the modern roofs may not be sufficient, and the purlins may fail under heavy snow load or wind suction (negative pressure). This paper presents an experimental investigation (Chung, K. F., Final technical report to ECSC Project 7210/SA/834, Steel Construction Insitute, Report No. SCI-RT-398, 19941) on the structural performance of five modern roof systems with thick over-purlin insulation. Three full-scale test series with a total of 12 single and five double span roofs supported by purlins of zed and sigma sections were carried out under both gravity and uplift loading conditions. Comparison on the structural performance of the modern roof systems are presented in detail and the implication of thick over-purlin insulation is fully discussed.