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Abstract
This research presents an experimental-analytical investigation in the flexural behavior of reinforced self-compacting lightweight concrete (LWC) beams. LWC was obtained through the use of polystyrene foam as a partial aggregate’s replacement to reduce the concrete dry unit weight from 23.0 kN/m3 to 18.5 kN/m3. The experimental investigation consisted of two phases; namely, the LWC mechanical properties and the flexural behavior of reinforced LWC beams. The mechanical properties incorporated the compressive and tensile strengths as well as its tension stiffening capability. In the second phase, experiments were conducted on six medium scale RC beams under static four-point bending setup till failure. The concrete type, the flexural reinforcement ratio and stirrups amount at the constant moment zone, were the main parameters investigated. Key test results first demonstrated that the beneficial effect of LWC in reducing the members’ self-weight was at the price of minimal structural disadvantages; namely, the slightly reduced pre-cracking stiffness gradually decreasing at post-cracking till failure as well as reduced ductility. Secondly, it was found that although increasing the flexural reinforcement ratio logically resulted in enhanced flexural capacity for the tested beams, the μmax of ECCS-203 is no longer valid for LWC beams, since over reinforcement was obtained in a beam with μ values less than μmax. Finally, the previous disadvantages were found to be partially compensated by the increase of stirrups, which inevitably resulted in partially increased ductility, due to the additional confinement provided to the concrete in compression. In the analytical phase of the research, a numerical model based on the strain compatibility approach was developed and validated in light of the experimental results. Key results of the validated model were then used to conduct a sectional analysis study in the light of the sectional stress and strain distributions adopted by the ECCS 203-01. The latter analyses resulted in proposed design equations and charts for LWC sections subjected to pure bending. A parametric study was also conducted on the element level to establish the maximum and minimum reinforcement ratios for LWC RC sections subjected to flexure.