ABSTRACT
A two-dimensional bus frame of complex construction was deformed to large deflections by a static testing method. It collapsed at a constant load via the formation of a complex structural collapse mechanism which allowed the frame to maintain its basic rectangular shape during collapse, deformation being concentrated in the plastic hinges which formed in the rectangular hollow sections that comprised its floor, the rest of the frame essentially rotating as a rigid-body. An upper-bound rigid-plastic approach utilising the principle of virtual displacements was applied to estimate the collapse load of the frame. This allowed its loaddeflection curve to be modelled by simply superimposing separate elastic and rigid-plastic models of its behaviour.
