Mechanical Properties of Steel–Concrete Composite Girder Subjected to Thermal History due to Fire

Fire damage to bridges occurs frequently in Japan and in other countries. Previous bridge fire accidents suggest that it is important to understand the structural performance of bridges after their exposure to fire. The Japan Society of Civil Engineering has proposed guidelines for the diagnosis and repair of steel bridges that have been exposed to fire. This guideline shows that the judgement temperature of steel members is 400°C. This temperature was established based on previous bridge fire accident reports and material testing after fire. It is unclear if the basis for evaluation has been the structural members. Therefore, it is necessary to clarify the effect of the rigidity reduction on the structural performance and judgement temperature of steel girder bridges after fire. The authors have studied the mechanical properties of steel–concrete composite girders as a medium span bridge before and after fire. A fire test was carried out to clarify the temperature distribution of the steel–concrete composite girder and static loading tests before and after fire were conducted to confirm the effect of the rigidity reduction from the fire. This study considers the validity of the judgment temperature from the test results. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.