Experimental evaluation of the load‐bearing capacity of steel‐reinforced CFST stub columns under a fire scenario

Composite construction is becoming increasingly used across the world, since it enables to exploit the benefits of steel and concrete working together, leading to cost‐effective solutions. Recent technological developments have facilitated the introduction of new typologies, which combined with the use of high performance materials allow for significant load‐bearing capacities with reduced cross‐sectional dimensions. One of these innovative composite sections are the so‐called steel‐reinforced concrete‐filled steel tubular (SR‐CFST) columns, where an open steel profile is embedded into a CFST section. Apart from the broadly recognized benefits of these typologies at room temperature, they show an enhanced fire performance due to the inherent fire protection offered by the surrounding concrete to the inner steel profile, which delays its loss of mechanical capacity at elevated temperatures. However, the experimental evidence on the fire behaviour of SR‐CFST columns is still scarce, being much needed for the development of specific design provisions that consider the use of the inner steel profile in CFST columns.

In this paper, a new testing program on the thermo‐mechanical behaviour of SR‐CFST columns is presented to extend the available experimental database. A cylindrical electric furnace attached to a loading rig equipped with a 5000 kN hydraulic jack is used. In total six SR‐CFST stub columns are tested, three circular and three square sections, combining high strength steel and concrete.