On dynamic snap buckling of shallow arches.

The general problem of large dynamic elastic deflections of a shallow circular arch under uniform dynamic-pressure loading is considered both analytically and experimentally. The basic nonlinear integrodifferential equation of motion for normal deflection is solved, for both simply supported and clamped boundary conditions, using the Galerkin method and an analog computer. Specifically, cases of initial-velocity (impulsive) loading, step loading, and rectangular-pulse loading are treated, both with and without various types of initial imperfections. Critical values for dynamic snap buckling are defined as those for which a very small increase in load produces a large increase in deflection of the **snap-through" type. The effect on these values of varying imperfection size and pulse length is studied in some detail.