Abstract
The purpose of this study was the investigation of thin-walled stressed-skin sheet pyramids for use as structural elements in lightweight roof systems. Exploratory tests were carried out on commercially produced glass reinforced polyester (GRP) hexagonal- base pyramids to determine the behaviour of thin-sheet units under load. The units were found to act mainly in the large deflection and post-buckled ranges. A review of the relevant literature was made, with much of the information originating from the field of aeronautical engineering. The calculation of the critical buckling load of the trapezoidal plates under uniformly distributed load at the apex and base was carried out using the method of collocation. Several effective width formulas developed for simply supported buckled rectangular plates in compression were applied to the results of tests on a full-scale hexagonal-base unit. To these was added a formula for the effective width of a buckled plate, proposed by the author. This formula took into account the geometry of the trapezoidal plate. Ultimate load tests were carried out on four GRP pyramids to determine the accuracy of the effective width formulas when applied to practical structures containing variations in thickness and mechanical , properties. The results of tests on individual pyramids were used to develop a method of analysis for structures composed of many pyramids by assuming that the pyramidal elements were equivalent pin-connected skeleton space frames. The analysis was then carried out by established methods developed for such skeleton structures. The results of this approximate method of analysis applied to the pyramidal structures were compared with the results of tests on two prototype structures, a stressed-skin space grid and a stressed-skin barrel vault. Conclusions were drawn, and suggestions were made for future research into some of the problems encountered.