Experimental study of laser-welded stainless steel I-section columns

Abstract

Stainless steel, an iron-carbon alloy, is traditionally not used in structural applications, due to the high initial costs and inadequate in-depth research into its structural properties. It is mostly used for architectural requirements and corrosion resistance. Over the years, developments in research and industrial applications have propelled viability of stainless steel as a structural material. This can be correlated to the increasing availability and accessibility to materials, and the paradigm shift towards durability. In particular, there has been increasing interest in the fire-resistant property of stainless steel, fuelled by the detrimental consequences of past fire accidents in buildings. Developments in stainless steel have also led to innovations in its fabrication process such as laser welding, in which laser beams are utilised to join metals or thermoplastic, forming a weld. It is a high precision fabrication process and the quality of the laser weld cannot be replicated easily. As this technology is largely in its infancy, experimental data on structural stainless steel members is insubstantial. The current international standards established in Europe, America and Australia/New Zealand do not cover laser-welded stainless steel members exposed to elevated temperatures. An experimental study of the axial compressive performance of laser-welded austenitic stainless steel I-section stub columns after exposure to elevated temperatures is conducted. A total of 17 stub column tests were performed on laser-welded stainless steel I-section members after exposure to elevated temperatures to address the lack of test data and to investigate their structural response. Initial local geometric imperfection measurements and 24 tensile coupon tests were carried out and recorded for the investigation of their material properties. Prior to testing, the stainless steel tensile coupon specimens and stub column specimens were placed in the furnace and heated to the eight different predefined temperatures. The experimental setups, procedures and key observations are fully reported. Based on the test results, the design provisions of European, American, Australian/New Zealand standards and a modified stress-strain curve are assessed.