In-Plane Buckling and Design of Steel Arches

Abstract

Many design codes do not give methods for designing steel arches against in-plane failure. The few that do provide methods that are essentially based on a linear interaction equation for the in-plane strengths of an equivalent beam-column, which uses the maximum elastic bending moment and axial compression in the arch. However, the linear interaction equation for a beam-column may not be suitable for an arch because it does not consider the strength characteristics of steel arches. This paper studies the in-plane buckling of arches in uniform compression and uses a nonlinear inelastic finite-element model to develop a method for designing steel arches against uniform compression, and also to develop an interaction equation for the design of steel arches against nonuniform in-plane compression and bending. Analytical solutions for the buckling loads of shallow arches in uniform compression are obtained. It is found that the design equation for steel columns cannot be used directly for steel arches in uniform compression, nor can the design interaction equations for steel beam-columns be used directly for steel arches under nonuniform compression and bending. The proposed design equations provide close predictions for the in-plane buckling strengths of both shallow and nonshallow steel arches in uniform compression. The modified interaction equation proposed provides good lower bounds for the in-plane strengths of both shallow and nonshallow steel arches in bending and compression because it considers the nonuniform distributions of the bending moment and axial compression around the arch, the behavior of shallow arches, and the favorable moment redistribution after the first hinge forms.