الفهرس 
Chapter 1 : IntroductionOnly 14 pages are availabe for public view
 |  | from | 160 |  |  |
| | | from | 160 | | |
Abstract
High Strength Concrete (HSC) characterized by high compressive strength but lower ductility compared to normal strength concrete. This low ductility limits the benefit of using HSC in building safe structures. Nanomaterials have gained increased attention because of their improvement of mechanical properties of concrete. In this search we present an experimental study and 3D fnite element analyzing of the flexural behaviour of reinforced concrete beams made of nanomaterials and high strength concrete. For this experimental study Eight simply supported rectangular beams were fabricated with identical geometries and reinforcements, and then tested under two third-point loads. The study investigated the concrete compressive strength (50 and 75〖N/mm〗^2) as a function of the type of nanomaterial (nanosilica, nanotitanium and nanosilica/nanotitanium hybrid) and the nanomaterial concentration (0%, 0.5% and 1.0%). The results of the experiments indicated that nanoparticles can greatly enhance compressive and tensile strength of HSC, nanotitanium is more effective than nanosilica in compressive strength. Also, Comparing the compressive and tensile strength of the hybrid mixture (nanosilica + nanotitanium) to the same percentage of each type of nanomaterial utilised separately, a significant improvement was seen. Nanomaterials can be used to compensate for the reduction of flexural ductility caused by the use of high strength concrete. The percentage of concentration, concrete grade and the type of nanomaterials, could predominantly affect the flexural behavior of High Strength Reinforced Concrete (HSRC) beams. Studying the indicators of structural behavior like load at first crack, load at ultimate capacity, toughness, deflection, crack pattern , concrete compressive strain, tension steel strain and ductility index. The load-deflection, Load-concrete compressive strain and Load –tension steel strain curves were further used to compare the structural characteristics. Applying ANSYS software, theoretical studies confirm experimental results. The ratio of each nanomaterial in the concrete mixture has been determined by experimental and theoretical results to have various flexural and crack effects on the HSRC beams for numerical tests.
The non-linear finite element Ansys Release 19 computer programme was used for theoretical studies. Analysis was done on the experimental models and other structural variables like span-to-depth ratio and shear span-to-depth ratio that could not be included in the experimental programme. This programme was used to research how concrete cracks and crushes appear. To predicate deflection at any stage of loading as well as the maximum load capacity.
Analytical study was conducted using stress, block models for different codes to determine the ultimate moment capacity for experimental models. The results show that stress, block models proposed by different codes of practice underestimate the maximum moment capacity for rectangular cross- section.