INFLUENCE OF THERMAL HISTORY ASSUMING FIRE DAMAGE ON MECHANICAL PROPERTIES OF STEELS FOR BRIDGE HIGH PERFORMANCE STRUCTURE

Many cases of bridge fires have been reported in Japan and overseas. When bridges are taken out of service due to fire, it is feared that economic activities will be greatly affected. Therefore, fire-damaged bridges must be recovered to service as soon as possible. It is important to accurately diagnose the degree of fire damage by estimating the thermal history of the damaged members and inspecting the external appearance of the bridge during a detailed investigation. Although data on mechanical properties of fire-affected steel materials is being accumulated, the mechanical properties after fire heating for newly developed high-performance steel materials are unknown. This study aims to investigate the influence of thermal history assuming fire damage on the mechanical properties of Steels for Bridge High Performance Structure (SBHS), standardized by JIS in 2008. A series of experiments were conducted to clarify the change in mechanical properties of SBHS400 and SBHS500 by heating and cooling. The heating up to 600 degrees C and cooling after that kept the mechanical properties of SBHS within the JIS standard. The heating up to 900 degrees C and cooling after that changed the mechanical properties of SBHS significantly. Furthermore, a method by using a portable hardness tester for estimating the change in mechanical properties after heating and cooling was proposed. The results indicated the possibility of quick investigation on after-fire site. Copyright (c) 2024 by The Hong Kong Institute of Steel Construction. All rights reserved.