Mechanical properties of S355 butt welds at elevated temperatures

The performance of welded connections in steel structures under fire depends on the mechanical properties of welds at elevated temperatures. Currently, EN 1993‐1‐2 [1] provides the following information for the design strength of welds: for butt welds, up to 700 °C, the design strength shall be taken as equal to the strength of the weaker part joined considering the reduction factors for material properties of the steel, while for butt welds above to 700 °C, and also for fillet welds, specific reduction factors for the design strength are proposed.

This paper presents the preliminarily results of an experimental investigation of specimens of butt welds realised with GMAW process under elevated temperatures. Steady‐state tensile tests, at 20 °C, 300 °C and 600 °C, were conducted on tensile coupon specimens extracted from welded steel plates. Results from these experiments have been used to evaluate the stress‐strain response, yield strength, modulus of elasticity, ultimate strength, and ultimate strain, as a function of the temperature for butt welds. Reduction factors were predicted for these mechanical properties. Some differences were achieved, especially at 600 °C, between the calculated reduction factors and those proposed by the EN 1993‐1‐2 [1]. Finally, it was also observed that the temperature has an impact on the tension fracture surface in welds.