Cambering structural steel I-girders using cold bending

Abstract

Cambering is often required in structural steel beams to compensate for dead load deflections. In this process, permanent deformations are induced in the girder after it is fabricated in order to match a required vertical profile under service loads. Traditionally, cambering is achieved by application of heat (heat cambering) or force (cold cambering). As in heat curving, heat cambering is time-consuming and costly. Cold cambering is faster and is most commonly used by fabricators. However, in the absence of data relating loads to deformations, the process is based on trial and error and relies on the fabricators skills and expertise. Recently, closed form equations and fabrication aids were derived for cold curving based on an available proprietary cold bending system. This paper extends this analysis to cambering where a girder is bent about its strong axis compared to weak axis bending in curving. New equations are derived and guidelines proposed that set limits on the maximum load and permanent residual strains to ensure they are within acceptable norms and prevent local failure. A comprehensive numerical example is included to illustrate this procedure.