STRUCTURAL RESPONSE OF REINFORCED CONCRETE FLAT SLAB EXPOSED TO HEAT

Over the past century, fire protection design approaches have been traditionally based on prescriptive fire resistance ratings achieved from standard tests. Standard approaches do not consider a wide range of typical structural conditions such as size, restrain conditions and loadings that are encountered in real practice. On the other hand, fire resistance behaviour of a single structural member is different from that of complete structure because of factors such as continuity, interaction between members and moment redistribution which are present in the whole structure. In the past few decades, there has been significant progress in structural fire safety analysis and design. However, such analysis relies on simplified methods and experimental data related to structural components, not of the complete structure. There has been very limited attention given on fire safety evaluation at the whole structure level. Two-way concrete flat slabs provide a number of benefits for office buildings and apartments – for example, reducing formwork, flexibility of partitions, relatively high ceiling, and prompt erection. The fire resistance of concrete flat slab structures is affected by many factors including concrete cover, cross section of the structural elements and the material properties of concrete and reinforcing steel bars which is not essentially constant during fire exposure. Concrete has fairly excellent fire resistance properties; however, the strength of concrete reduces as temperature rises. There is a lack of studies, both analytical and experimental, on flat plate concrete slabs in the literature. This thesis presents a review of the available experimental and numerical studies on structural systems under fire, and identifies the research gaps in this area. Ultimate punching and moment capacity of concrete flat slab systems are studied numerically and experimentally. The numerical study includes the investigation of the effects of different parameters such as concrete and reinforced steel bars behaviour and the structural behaviour of two-way slab at elevated temperature. The fire performance of a concrete flat plate slab at elevated temperature is complicated. The existing concrete codes cannot predict the capacity under fire exposure and detail investigation is needed to predict fire resistance of flat slabs. Structural concrete design for fire is still in the developing stage in various parts of the world. There is a lack of experimental studies, mainly because of the difficulties associated with a setup for high temperature and high cost of experiments. The main work of this study is the experimental and numerical analysis of slab prototype under combined elevated temperatures and gravity loading. Thermal exposure may cause sudden failure of the concrete slab structures. An experimental program conducted on six concrete, slab-column assemblies are presented to investigate their performance in high and ambient temperature. A numerical model is also presented and compared against test results. One of the main costs is the additional specification or protection required to provide adequate safety in the event of a fire. Current structural fire protection systems focus on limiting the rate of temperature rise of formwork and concrete cover. This work addresses the parameters that can affect the slab behaviour under fire exposure to prevent collapse. Fire protection by fire barrier or structural modifications is concerned with safeguarding the occupants in the building where the fire may occur. Structural modification should be investigated in detail because some of them have direct effect where others do not have significant effects