Abstract—To determine the potential of a low cost Irish engineered timber product to replace high cost solid timber for use in bending active structures such as gridshells a single Irish engineered timber product in the form of orientated strand board (OSB) was selected. A comparative study of OSB and solid timber was carried out to determine the optimum properties that make a material suitable for use in gridshells. Three parameters were identified to be relevant in the selection of a material for gridshells. These three parameters are the strength to stiffness ratio, the flexural stiffness of commercially available sections, and the variability of material and section properties. It is shown that when comparing OSB against solid timber, OSB is a more suitable material for use in gridshells that are at the smaller end of the scale and that have tight radii of curvature. Typically, for solid timber materials, stiffness is used as an indicator for strength and engineered timber is no different. Thus, low flexural stiffness would mean low flexural strength. However, when it comes to bending active gridshells, OSB offers a significant advantage. By the addition of multiple layers, an increased section size is created, thus endowing the structure with higher stiffness and higher strength from initial low stiffness and low strength materials while still maintaining tight radii of curvature. This allows OSB to compete with solid timber on large scale gridshells. Additionally, a preliminary sustainability study using a set of sustainability indicators was carried out to determine the relative sustainability of building a large-scale gridshell in Ireland with a primary focus on economic viability but a mention is also given to social and environmental aspects. For this, the Savill garden gridshell in the UK was used as the functional unit with the sustainability of the structural roof skeleton constructed from UK larch solid timber being compared with the same structure using Irish OSB. Albeit that the advantages of using commercially available OSB in a bending active gridshell are marginal and limited to specific gridshell applications, further study into an optimised engineered timber product is merited. Keywords—Bending active gridshells, High end timber structures, Low cost material, Sustainability. I. INTRODUCTION RIDSHELLS are doubly curved structures, constructed from initially straight elements that resemble shell structures. Shell structures are inherently effective in their structural performance leading to high span to thickness ratios. They inherit their strength and stiffness from their three Financial support was given by the Irish Research Council (IRC) M. Collins is with the Department of Civil Engineering and Material Science at the University of Limerick, Ireland (phone: +353 (0) 61 234733; e- mail: matthew.collins@ul.ie). B. O’Regan is with the Department of Chemical and Environmental Science at the University of Limerick, Ireland (e-mail: bernadette.oregan@ul.ie). T. Cosgrove is with the Department of Civil Engineering and Material Science at the University of Limerick, Ireland (e-mail: tom.cosgrove@ul.ie). dimensional geometry and curvature. Large open plan spaces can be created with a minimum amount of material. Gridshells represent a state of the art in structural timber engineering, which are difficult to engineer. There are two principle categories of gridshells, classified as bending active and bending inactive gridshells. The term bending active means that the structural elements have to bend considerably to give the structure its shape, a type of bending pre-stress [1]. Alternatively, bending inactive describes a structure whereby the structural elements do not need to bend to give the structure its shape. A typical bending inactive structure would be a truss, portal frame and a geodesic dome. The majority of bending inactive gridshells have been constructed from steel whereby the structure is comprised of numerous straight elements each inclined at a different angle to its adjacent element to give the structure its curved shape. Bending active gridshells on the other hand are not all that common, however a number of them have been constructed such as the Multihalle in Mannheim [2], the Weald and Downland Museum [3], and the Savill Garden centre [4] (Fig. 1). Notably, the majority of bending active gridshells is constructed from solid timber sections. However, there was a high cost associated with these gridshells because solid timber was used. Many natural defects such as knots, splits and grain discontinuities occur in solid timber. These defects become critical when using small sections, as the defects do not scale with section size. Therefore, the solid timber material used for the gridshells mentioned in [2]-[4] had to be specially selected from the timber available. For the latter two gridshells described in [3] and [4], from the lengths of sawn timber, the defects were identified, removed and the defect free pieces finger jointed back together. The average defect free piece was 600mm with the distances to be spanned for the Savill garden gridshell being 90m and 25m [5]. The time and labour required to carry this out led to a high processing cost along with an initial high base cost for the actual material, which is unsuitable for the sustainability of these structures. However, in more recent years, alternative engineered materials have been used in the construction of gridshells, more so for bending active gridshells such as cardboard tubes [6] and glass fibre reinforced polymers (GFRP) [7]. Potential of Irish Orientated Strand Board in Bending Active Structures M. Collins, B. O’Regan, T. Cosgrove G World Academy of Science, Engineering and Technology International Journal of Civil, Structural, Construction and Architectural Engineering Vol:9, No:3, 2015 305 International Scholarly and Scientific Research & Innovation 9(3) 2015 International Science Index Vol:9, No:3, 2015 waset.org/Publication/10001017