Experimental and numerical studies on the fire resistance of reactive powder concrete-filled steel tubular columns

Abstract

Reactive powder concrete-filled steel tubular (RPCFST) column is composed of high strength reactive powder concrete (RPC) wrapped by outer steel tube. At present, the failure mechanism, stress variation law, decisive factors of fire resistance limit and its calculation method of RPCFST column in fire still need to be further studied. To study the fire resistance of RPCFST columns under exposure to fire conditions, 7 RPCFST column specimens were designed and produced. The constant load heating test was carried out. Considering the influence of steel tube wall thickness (5 mm, 6 mm, 8 mm), load ratio (0.4, 0.5, 0.6) and fiber type (plain concrete, 2% steel fibers, 0.3% polypropylene fibers), the internal temperature, axial displacement, failure mode and related experimental curves of different specimens under fire were observed and analyzed. Results indicate：under fire exposure, the surface of the steel tube of RPCFST column becomes orange-red, and there are different degrees of local buckling and overall buckling. The load ratio has the greatest influence on the fire resistance of RPCFST columns. The influence of steel tube wall thickness on the fire resistance is second. The type of fiber has the least influence on the fire resistance of RPCFST columns. As the load ratio increases from 0.4 to 0.5 and 0.6, the fire resistance limit decreases by 29% and 55%, respectively. A simplified formula for calculating the fire resistance limit is also derived in this paper. The results of the formula are in good agreement with the experimental results, which verifies the accuracy of the proposed equation.

The authors' abstract, as published at the source. Structures, 2026 · DOI ↗