Timber constructions have during the past two or three decades become more andmore common, mostly due to the easy prefabrication and the cheap, sustainablematerial. For long-span applications it is vital to find design solutions that optimizethe structure from the point of view of material consumption, number of theconnections, structural reliability etc.This thesis focuses on the structural optimization of a long span timber structureearlier developed by a Swedish glulam company for industry buildings and sport hallapplications. The main goal of this study has been the minimization of the volume ofwood required to built the structure, given a set of geometrical restrictions and theassigned loads.The optimal shape of the structure and the arrangement of the different elementshas been investigated by means of theoretical analyses taking into account theprincipal directions of stress which would occurr in similar structures with massivecross sections. The results of this investigations give some guidelines to design newtypes of structures, where both mechanical efficiency and manufacturing issues havebeen taken into consideration.Comparisons of the structural models proposed in this thesis with the originalproposal provided by the Swedish glulam company conclude the work, suggestingsome possible improvements.