دانلود رایگان مقاله ظرفیت زمانی و حفاظت حریق از ورق جوش داده شده مشترک

Abstract

Specimens of reinforced concrete (RC) cantilever beams connected by a welded plate joint to an RC main beam were investigated. Load tests and fire tests were conducted to examine structural behavior and fire resistance of the joint. Under flexural load, the main failure modes of the joint were splitting of the welded plate and rebar yielding. The joint moment capacity depended on ability of the joint to resist tensile forces in the beam rebars. The ultimate loads were about 50% and 70% of corresponding cast-in-place specimens, for the joints with 4-mm and 6-mm thick plates, respectively. To simply estimate the moment capacity, the plate in its width direction was modeled as a beam with fixed ends, and the forces in tensile rebars acted as point loads. The proposed computation of the moment capacity was validated with the tests and with FE simulations, for both moment magnitudes and failure types. By using fire tests, fire protections of the joint such as thin or thick mortar plaster, or a flexible sealant, were investigated. The thick plaster and the sealant provided fire resistances exceeding 2 h. However, the flexible sealant coped better of these two with the separating and swelling behaviors.

7. Discussion and conclusions

Structural behavior of a loaded cantilever with welded plate joint and its fire resistance while subjected to a flexural load were examined. The investigated specimens were reinforced concrete (RC) cantilever beams connected to an RC main beam with welded plate joints. Seven load tests and four fire tests were conducted as physical experiments. The varied parameters of the load tests were joint section dimensions, plate thicknesses, and rebar dimensions, in such ranges that are practical for use in small construction. Furthermore, finite element simulations of the specimens were used to assess in detail the structural behavior, and partly based on these simulations a simplified method was devised to estimate the moment capacity of a welded plate joint. However, further experiments on thicker plate are required to investigate an improvement of the moment capacity. The main conclusions are as follows: - The load bearing capacity of a joint depends on its ability to resist the tensile forces induced in the steel rebars. Separation and swell of the joint occur when the load becomes excessive. The main failure of the welded plate joint was splitting of the plate. However, once the welded plate can resist higher tensile forces than the connected rebars, the joint will failed from tensile yielding in the rebars.