Geometric Nonlinearity and Long-Term Behavior of Crown-Pinned CFST Arches

Abstract

Concrete-filled steel tubular (CFST) arches are often used in engineering structures, particularly in bridge construction. In some instances, to expedite their construction and transport, curvilinear steel tube segments are fabricated and delivered to the construction site and then joined together at the crown to create a pin, so the arch becomes a crown-pinned arch. Wet concrete is then pumped into the steel tubes to form the concrete core after curing, which experiences time-dependent shrinkage and creep. This paper investigates the effects of geometric nonlinearity on the long-term in-plane behavior of crown-pinned circular CFST arches under a sustained central concentrated load, and derives analytical solutions for their nonlinear response and buckling loads. It is found that the geometric nonlinearity influences the long-term behavior of crown-pinned CFST arches significantly. The long-term deformations predicted by the nonlinear analysis are larger than those predicted by linear analysis, and they may be so large that the reserve of the serviceability limit state of crown-pinned CFST arches may be reduced significantly. The nonlinear analysis also predicts significant long-term increases of the axial forces and bending moments in crown-pinned CFST arches, which is quite different from linear analysis that predicts no long-term changes of the axial force and bending moment for thee-pinned CFST arches and only small long-term changes for singly pinned CFST arches. It is also found that the nonlinear long-term in-plane buckling loads of crown-pinned CFST arches are smaller than their counterpart values determined from linear analysis. Hence, the geometric nonlinearity together with the shrinkage and creep of the concrete core may reduce the reserve of the stability limit state of crown-pinned CFST arches in the long term. To determine the long-term structural response and buckling of crown-pinned CFST arches correctly, nonlinear analysis is required.