دانلود رایگان مقاله رفتار پس از آتش اتصال برشی نوآورانه برای سازه های کامپوزیت فولاد و بتن

Abstract

Steel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three types of connectors were investigated. They are conventional headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post-fire condition of 200 °C, 400 °C and 600 °C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. This research showed that the headed studs performed well compared to Blind Bolts 1 and 2 at ambient and target temperatures. The stress concentrations around the casing of Blind Bolt 1 were found to cause a reduction in strength of the specimens. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure.

4. Conclusions

The behaviour of headed studs, Blind Bolt 1 and Blind Bolt 2 as shear connectors at both ambient temperature and post-fire condition were tested using the push-out test specimens. Additionally, the experimentally determined test failure loads were compared to the theoretically predicted failure loads using the Eurocode 4, AISC [4] and AS2327.1- 2003 method of analysis. The results of the experimental tests showed that all specimens were dominated by the concrete failure of the slab at both ambient temperature and at post-fire. The following observations were made based on the experimental tests and comparison with predictions from the current standards: 1. The experimental test failure loads of headed studs and Blind Bolt 2 specimens, at ambient temperature, were of the same magnitude. Blind Bolt 1 specimens, however, showed less failure capacity due to the stress concentrations around the casing of the bolts. 2. Headed studs performed well compared to Blind Bolt 1 and 2 at ambient temperature and all post-fire target temperatures. On the other hand, Blind Bolt 2 performed better than Blind Bolt 1 at ambient temperature and all post-fire target temperatures. 3. The residual strength of the headed studs in all post-fire target temperatures was better compared to the Blind Bolt 1 and 2. When compared to the failure loads at ambient temperature, the residual strength of Blind Bolt 1 and Blind Bolt 2 are comparable at all post- fire target temperatures. 4. Following exposure to various degrees of temperatures, all the specimens exhibited minor structural damage, with slight separation of the steel and concrete evident and minor spalling. However, thermal damage to the specimen causes the concrete to become brittle. As a consequence, a sudden drop in load was observed for all specimens at post-fire. 5. For the 30 MPa strength of concrete used for all specimens, the eight shear connectors per specimen had greater shear strength compared to concrete. Therefore, no shear connector yield failure was observed at both ambient temperature and at post-fire.