Creep buckling of shallow parabolic concrete arches

This paper addresses, both theoretically and experimentally, the buckling of shallow concrete arches that may occur due to the effects of creep and shrinkage deformations of the concrete. Under sustained loading, these viscoelastic effects cause time-dependent changes of the deflections of a shallow arch and can lead to the establishment of a geometric configuration at which the arch is no longer stable, and which heralds the onset of creep buckling. By using a virtual work formulation, the equilibrium and buckling equations of an arch with horizontal spring supports are derived in closed form, and using the algebraically tractable age-adjusted effective modulus method to model the time-dependent behavior of the concrete allows the buckling load and the prebuckled life of the arch to be determined using prescriptive equations. Long-term tests on three 4.25 m span arches under sustained loading are described. Each arch failed because of creep buckling several months after first loading. These tests are used to validate the theory developed in the paper and to provide benchmark data for calibration. The study shows that creep and shrinkage of the concrete have a profound influence on the structural behavior of shallow concrete arches.