الفهرس 
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Abstract
Performance of concrete strengthened with high performance concrete under fire I ABSTRACT Application of HPC is spread widely in all worlds in tall building, tunnels, and high way bridges. The use of HPC allows higher load carrying capacity of members at a lower cost, decreases the member dimensions consequently increases in usable space, and decreases the unit weight for a given strength which can be advantageous in seismic zones. In addition, HPC is widely using in hybrid structure with NSC especially in making precast composite members to enhance its structural performance. On the other hand, repairing as well as strengthening of the existing structures has become essential from both of technical and financial points of views. Moreover, as HPC are being intensively used as a repairing or strengthening material for different structures, its post-fire performance needs to be investigated. So, this study is directed to investigate the post-fire (residual) flexural behavior of reinforced concrete slab cast with traditional normal strength concrete (NSC) and strengthened with high performance concrete (HPC). This investigation consists of two parts include experimental work and analytical work. The experimental investigation compresses two sections. The first section attempts to investigate the mechanical properties of NSC and HPC after exposed to different temperatures up to 800 oC. In preparing HPC, different parameters were considered; using 0.5% polypropylene or steel fibers or hybrid fibers, fly ash and ground granulated blast furnace slag. The second section aims to investigate the post-fire (residual) flexural behavior of reinforced concrete slab cast with traditional normal strength concrete (NSC) and strengthened with high performance concrete (HPC). Twenty one reinforced concrete slab specimens were prepared and tested. The conducted slabs were divided into two main groups including casting the whole thickness of the slab specimens with the same mixture (NSC for control (two specimens) and HPC for other parameters (7 specimens)) or as a composite from NSC and HPC (12 specimens). The parameters include HPC parameters in addition, more factors were considered during preparation and testing of specimens; joining the HPC layer to NSC (using epoxy resin ABSTRACT Performance of concrete strengthened with high performance concrete under fire II or shear studs) and the fire exposure side (tension or compression sides). The slabs were exposed to temperature up to 600 oC, after the furnace temperature reaches to the target temperature it stay another 2 hrs, then cooled down to room temperature and tested under a four-point loading test. The analytical part divided to two parts includes ABAQUS software and artificial neural net work (ANNW). Three dimensional finite element model has been conduct using ABACUS software to predict the thermal and structural behavior of reinforced concrete (RC) slab made-up of different concrete types under ISO834 standard fire curve. The parameters include concrete type, load-intensity, aggregate types, concrete cover thickness, slab thickness, concrete tensile strength, and steel yield strength. Besides, ANNW model is used as alternative approach for predicting the temperature distribution of RC slab and its fire resistance. This model is used to study the effect of different parameters include aggregate type, slab thickness, concrete cover and reinforcement type on the fire resistance of RC slab. The results of the proposed investigation showed that strengthening RC slab in tension or compression by using HPC remarkably enhanced the slab performance after exposure to fire. Specially, HPC containing hybrid fibers (steel + polypropylene fibers) in tension side of composite slab in case of fire exposure from tension side recorded the highest cracking load, ultimate load, stiffness, toughness, and ductility index as compared to the control slab (NSC slab) and recorded an increment of 92.8%, 116%, 157%, 335%, and 86.9%, respectively. Moreover, the results of finite element model showed that the behaviors of RC-slab under fire depend on the concrete types, where HPC with polypropylene fiber proved better fire resistant than other concrete types in lower deflection and lower reinforcement temperature. Concrete cover and concrete slab thickness significantly delayed the failure of slabs exposed to fire. In contrary, increases load intensity lead to decrease the fire resistance for both concrete types. Furthermore, the ANNs models are succeed in predicting the effect of different parameters in the resistance of RC slab. ABSTRACT Performance of concrete strengthened with high performance concrete under fire III Keywords: Post-fire, Composite RC slab, High performance concrete, Thermal behavior, Structural behavior, Fire resistance, Finite modeling, Artificial neural network.