In-plane buckling and design of steel arches

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 equivalen t beam-column, which uses the maximum elastic bending moment and axial comp ression in the arch. However, the linear interaction equation for a beam-co lumn may not be suitable for an arch because it does not consider the stren gth characteristics of steel arches. This paper studies the in-plane buckli ng of arches in uniform compression and uses a nonlinear inelastic finite-e lement 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. Analytic al solutions for the buckling loads of shallow arches in uniform compressio n are obtained. It is found that the design equation for steel columns cann ot be used directly for steel arches in uniform compression, nor can the de sign interaction equations for steel beam-columns be used directly for stee l arches under nonuniform compression and bending. The proposed design equa tions provide close predictions for the in-plane buckling strengths of both shallow and nonshallow steel arches in uniform compression. The modified i nteraction equation proposed provides good lower bounds for the in-plane st rengths of both shallow and nonshallow steel arches in bending and compress ion 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.