Modeling the roof deck and determining its effect on the stability of a glulam timber dome
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A finite element modeling and geometrically nonlinear static analysis of the top portion of a glued-laminated timber dome is presented. The modeling assumptions and analysis procedures are applied to a dome model whose geometry is based on an existing glulam timber dome of 133 ft. span and 18 ft. rise above the tension ring. This dome consists of triangulated network of curved southern pine glulam members connected by steel hubs. The dome is covered with a tongue-and· groove wood decking. The role of decking towards the stability of the overall structure is studied. The lateral resistance of the nail fasteners connecting the beams and the purlins to the decking is considered . The stabilizing effect of the decking is shown to be mathematically analogous to that acting on the beams along the line of the deck attachment. The axial pull, in this study is modeled by truss members. Three distinct analyses are performed for rigid and flexible joints: a linear analysis to check design adequacy of the members, a linearized eigenvalue buckling prediction analysis to estimate the buckling load, and finally an incremental, iterative, geometrically nonlinear analysis to trace the complete response of the structure up to failure. Analyses are done for the structure with and without the decking on top of the beams and purlins to assess the role of decking on the overall stability of the structure. It is shown that decking plays a considerable role in the load-carrying behavior of the whole structure. A discussion of the results is presented and recommendations for future extensions are included.
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