Behaviour of a two-pinned steel arch at elevated temperatures.

Because of their geometrical shape, two-pinned steel arches (TPSAs) have special internal force distributions and deformations compared with conventional straight beams. However, the present studies on TPSAs exposed to fire are still quite limited with regard to their fire-induced deflection modes or deflection limits and ultimate temperatures. This paper employs several numerical models to analyse the high-temperature performance of TPSAs at elevated temperatures in terms of the effects of the load ratios, horizontal restraints, rise-to-span ratios, fire fields and geometrical sizes of the cross-section. The results show that TPSAs exposed to high temperatures are more sensitive to the load ratios than the horizontal restraint stiffness and geometrical size of the cross-section. The TPSAs could not develop catenary actions such as those of straight beams in fire; previous investigations have not predicted the behaviour of TPSAs in fire. The in-plane buckling and excessive mid-span sagging of TPSAs are the final failure modes regardless of the location of the fire actions. To date, the acceptable rise-to-span ratio is approximately 0.25–0.35 for TPSAs in fire. Finally, this paper presents a prediction formula for the limit state of TPSAs at elevated temperatures by using trigonometric functions and logarithmic regression. [ABSTRACT FROM AUTHOR]