Finite Element Stability Analysis of a Glulam Dome

Abstract

The paper centres on stability investigations of a glued-laminated timber (glulam) dome under several snow load conditions. The dome consists of a triangulated network of curved glulam beams, a decking supported by curved purlins, and a steel tension ring. The dome is represented by two different models. The first model is a rigid-jointed space frame composed of curved beam elements. The second model consists of straight beam elements, with rigid or flexible joints, and a bracing to simulate the lateral support of the beams provided by the decking. Two finite element methods are presented and used in the analyses: A nonlinear method that computes the buckling load and a combined nonlinear/linear eigenvalue method that provides estimates of the buckling load. The results presented include buckling pressures, buckling modes, effects of joint stiffness and bracing on the stability of the dome, and the status of the material prior to buckling.

Effect of Ring Beam Stiffness on Behaviour of Reticulated Timber Domes

“…For unsymmetric loads (over half the dome), the buckling mode shows a localised pattern in that half of the dome where the load is applied. The critical buckling load increases for unsymmetric loads because bifurcation in form of twist buckling does not occur all over the dome as in the case of symmetric loads [11].…”

“…For reticulated domes, the main problems are buckling and optimisation. A practical tool for investigating the stability of complex structures is the combination of accurate nonlinear analysis and efficient linear eigenvalue predictions to estimate the critical buckling loads [11]. The size and shape of imperfections, the rigidity of joints, and the bracing effect and composite action of the decking must be known and introduced in the design stage.…”

“…The different instability modes that can occur in reticulated domes are member buckling, node buckling, twist (or torsional) buckling, ring buckling, general buckling, and coupled buckling, depending on the geometrical parameters of the dome [11][12][13]. For a sparse network, member instability is the decisive criterion, and for a dense network, overall instability is the governing phenomenon.…”

“…The main loads for reticulated shells are local and unsymmetrical wind and snow loads. Point loads are particularly detrimental to dome stability [11][12][13]15].…”

“…The bracing is important because it suppresses the premature twist buckling of the dome. There is a limited effect of the joint stiffness, particularly in the presence of bracing and symmetric loads [11].…”