Elevated temperature mechanical properties of solid section structural steel

[Display omitted] •Extensive closed-loop strain-rate controlled tensile tests of solid section steels.•Novel and accurate temperature-dependent data for advanced structural fire design.•Novel investigation on temperature-dependence of inhomogeneities of YS and UTS.•Inhomogeneities in YS and UTS in solid sections vanish with increasing temperature.•Inhomogeneities in YS and UTS in thick as-rolled solid sections less significant.•Existing code models also suitable to predict degradation of solid section steels. In structural fire design thick solid steel sections are often used for steel columns without fire protection or more recently in innovative composite column systems as for example concrete-filled steel tube columns with solid steel core. The data in the literature on the mechanical properties of commercially available solid section mild carbon steel used in structural fire engineering is scarce and limited to investigations at ambient temperature, showing high inhomogeneity in the yield strength between peripheral and core material, especially in the as hot-rolled condition. This paper presents the results of an extensive series of closed-loop strain-rate controlled tensile tests, performed at elevated temperatures of 400, 475, 550, 626, 700 and 900°C under steady-state conditions and at ambient temperature with coupon specimens of core and peripheral material of commercially available mild carbon steel from round solid sections of various diameters. The resulting temperature-dependent relations for the yield strength and ultimate tensile strength (1) indicate for normalised small sections and as hot-rolled thick sections only a moderate difference between core and peripheral material that vanishes with increasing temperatures, and (2) can be predicted reasonably well by the European and North American design code models for structural steels at elevated temperature.