Abstract:
The aim of this research is to generate optimised design solutions for a range of long span Laminated Veneer Lumber (LVL) portal frames and trusses under different loadings. These optimised design solutions respect the required structural capacities and deformation performances under the New Zealand design standards while using the minimum volume of LVL. Three types of efficient timber roof configurations have been included in this study. They are the mono-pitch portal frames, the double-pitch portal frames and the Pratt trusses. Each of these three roof configurations has been designed at a range of large clear spans and at different clear heights, varying from 10 meters to 70 meters. All portal frames solutions are designed in box section of LVL. All truss solutions are designed using solid sections of LVL. Extensive finite element analysis have been carried out for every roof configuration designs to ensure the highest material saving solution had been reached. Result tables and configuration drawings of the final optimised solutions for portal frames and trusses are generated. Mathcad design tools and supporting materials for portal frame design are also generated to ease future design processes. Using the results and supporting materials generated in this study along with design examples, a Long Span Roof Guide has also been written and is to be published. Engineers and future owners of the buildings may use the solutions from this research to estimate the structural costs and allow comparisons with other design options. The average volume of LVL for mono-pitch portal frames from clear spans of 10 meters (total span of 20 meters) to clear spans of 50 meters (total span of 100 meters) are about 1.97 cubic meters to 52.97 cubic meters. The average volume of LVL for double-pitch portal frames from clear spans of 15 meters to clear spans of 45 meters are about 1.57 cubic meters to 15.34 cubic meters. The volume of LVL for Pratt trusses from clear spans of 50 meters to clear spans of 70 meters are about 4.83 cubic meters to 13.05 cubic meters. Overall, this study demonstrated that it is feasible to construct large span LVL portal frames and trusses. Further studies may be carried out to even larger spans and heights, alternative configurations of timber roof structures, alternative cross sections and material.