A Practical Method for the Elastic Buckling Design of Network Arch Bridges

Network arch bridges under the action of vertical loads are affected by out-of-plane instability phenomena, which strongly reduce their structural integrity. Current design codes on steel arch bridges do not provide complete and adequate methodologies for the buckling design since they are based on linear buckling analyses, whose predictions in many cases overestimate the actual bridge capacity. In the present paper, a numerical procedure is implemented with the purpose to derive simple analytical expressions for the evaluation of critical axial force in network arch bridges. The proposed study is developed by means of progressive analyses, in which at first variability screening analysis is developed to identify worst instability scenarios with respect to all geometrical and mechanical characteristics in typical allowable ranges. Subsequently, explicit parametric analyses are developed to identify instability curves for several bridge configurations. The validity of the formulation is verified by means of comparisons with advanced analyses based on the FEM. The proposed results in terms of buckling curves may help the designer to achieve a proper estimation of the critical buckling load without developing sophisticated and complex nonlinear analyses.