Browsing by Author "Seleem, Hosam"

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Effect of Using Lightweight Concrete on the Behavior of L and T- Beams under Combined Stresses
(azharcermjournal, 2019) Awad, Ahmed; Deifalla, Ahmed; Seleem, Hosam
This paper presents an experimental investigation for the behavior of flanged reinforced lightweight concrete (LWC) under combined stresses. 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 18.1 kN/m3. The experimental work was consisted from two phases; The first phase quantified the mechanical properties of lightweight concrete; namely the compressive and tensile strengths as well as the tension stiffening capability of the concrete mix and The second phase was concerned with testing specimens of lightweight and normal-weight concrete beams (L and T-shaped) under combined stresses for determination of the ultimate resistance, mode of failure, ultimate angle of twist, and load-deflection curve for all tested beams. The experimental program consisted of four full scale T & L beams with cross-section of (150 x 400 mm.). Two T-sections having a width of slab 550 mm and slab thickness of 150 mm, span of 1300 mm, load eccentricity of 50mm, with varying material type (LWC, and NWC). Two L-sections having a width of slab 350 mm and slab thickness of 150 mm, span of 1300 mm, load eccentricity of 50mm, with varying material type (LWC, and NWC).The main variables of this study were the material type, and the shape of cross section. The observed behavior of the light weight concrete specimens up to failure greatly encourages the use of light weight concrete in all structural elements.
Investigating the behavior of lightweight foamed concrete T-beams under torsion, shear, and flexure
(Elsevier Ltd, 9/15/2020) Deifalla, A; Awad, A; Seleem, Hosam; Abdelrahman, Amr
Compared to conventional normal weight concrete, Lightweight Concrete (LWC) has significantly lower own-weight-to-strength ratio and good thermal insulation. Previous studies showed that the design codes underestimate the strength of LWC beams under pure shear force or pure torsion moment. In addition, the behavior and design of LWC T-beams under combined bending, shear and torsion was never investigated. Thus, this current study explores the effect of various parameters on the behavior of lightweight foamed concrete (LWFC) T-beams under combined shear, torsion and moment. Investigated parameters included the following: shear-span-to-depth ratio, torsion-to-shear-depth ratio, flange-to-web-width ratio, and transversal reinforcement ratio. An experimental program was conducted which included testing five T-beams under various ratios of combined loading. In addition, a numerical model was developed for LWFC T-beams under combined loading and verified using available experimental results. Moreover, a parametric study was performed to further investigate the effect of the selected parameters on the behavior of LWFC T-beams. Last but not least, the most recent internationally recognized design code is selected and used to calculate the T-beams strength, which was compared with the ones from the experimental and numerical investigations. For small values of the shear-span-to-depth ratio, the LWFC T-beams strength increased with the decrease of the torsion-to-shear-depth ratio compared to those with large values of the shear-span-to-depth ratio. In addition, the effect of the flange width was found to be insignificant. Moreover, the failure mode for beams with transversal reinforcement ratio above 1.2%, changed from under-reinforced mode to an over-reinforced one. Last but not least, the strength predicted using selected design code was found to be overly conservative compared to that experimentally measured and that numerically predicted for LWFC T-beams under combined loading.