INVESTIGATION ON FATIGUE FAILURE MODES AND MECHANISMS OF STEEL REINFORCED CONCRETE GIRDERS

Previous studies at home and abroad have revealed that solid-web steel reinforced concrete (SRC) girders have two failure modes under static loading, that is, flexural failure at the normal section and shear failure at the oblique section. It aims to study the failure mode, mechanical performance and mechanism of solid-web SRC girders under fatigue loading through experiments. Fatigue tests were carried out on a total of 50 SRC girders. The effects of various parameters were taken into account, including steel ratio of H-steel, steel ratio of tensile reinforcements, shear span-to-depth ratio, concrete grade and whether to install stud connectors. The shear span-to-depth ratio ranged from 1.0 to 4.2. In order to compare the fatigue performance of steel beams inside SRC girders, fatigue tests on 8 pure steel beams were also conducted. This paper elaborated the fatigue failure process of each component inside SRC girder and compared the mechanical behaviors in constant moment region and shear span region. Test results show that as the shear span-to-depth ratio ranges from 1.0 to 4.2, the flexural fatigue failure mode is absolutely the dominant failure mode for the solid-web SRC girder, which is a key issue in anti-fatigue design, and the shear fatigue failure mode at the oblique section is very unlikely to occur. The shear fatigue strength at the oblique section of pure steel beam is much higher than the flexural fatigue strength at the normal section, and there is the same observation on the fatigue performance of steel beam inside SRC girder. The flexural fatigue failure of internal steel beam is a sign of fatigue failure of the entire SRC girder. Constructional measures to improve the fatigue strength of steel beam are of great significance to the improvement of fatigue performance of SRC girder.