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Al Khalil, Jwan Ahmad - One of the best experts on this subject based on the ideXlab platform.
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STRUCTURAL RESPONSE OF FLEXURE-DEFICIENT REINFORCED CONCRETE CONTINUOUS SLABS STRENGTHENED WITH COMPOSITES
Scholarworks@UAEU, 2015Co-Authors: Al Khalil, Jwan AhmadAbstract:Accidental reduction in the amount of steel in continuous reinforced concrete (RC) floor slabs is a typical problem that might occur due to an error in design, unclear drawings, or overlooked verification of reinforcement prior to concrete casting. Existence of such deficiencies would compromise the load capacity and serviceability of RC floor slabs. This research examines the effectiveness of using fiber-reinforced polymers (FRP) to improve the structural response of flexure-deficient continuous RC slab strips. The study comprised experimental testing and finite element (FE) modeling. Sixteen two-span RC slab strips, 400 x 125 x 3800 mm each, were tested. Test parameters included the deficiency location, strengthening regime, and amount of FRP. The unstrengthened slab strip deficient in the Sagging Region had 22% lower load capacity and 64% higher deflection-based ductility index compared with those of its counterpart deficient in the hogging Region. Strengthening with FRP improved the load capacity and stiffness of the deficient slab strips. The FRP strengthening tended to decrease the ductility index of the slab strips deficient in the Sagging Regions. Conversely, the ductility index of the slab strips deficient in the hogging Region tended to increase after strengthening. The strength gain caused by strengthening was in the range 29% to 69% for the slab strips deficient in the Sagging Regions and 14% to 44% for those deficient in the hogging Region. Increasing the amount of FRP resulted in an increase in the load capacity but the additional strength gain was, generally, not proportional to the added amount of FRP. Increasing the amount of FRP had, typically, less significant effect on the load capacity of the slabs deficient in the hogging Region than in the Sagging Region. vii Strengthening of deficient Regions reduced the moment redistribution ratios. The ratios further decreased as the amount of FRP in the deficient Region increased. A maximum moment redistribution ratio of +32% was recorded for the strengthened slab strips. The FE models developed in this study predicted the nonlinear structural response of the tested continuous RC slab strips with a hig
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Structural Response of Flexure-Deficient Reinforced Concrete Continuous Slabs Strengthened With Composites
Scholarworks@UAEU, 2015Co-Authors: Al Khalil, Jwan AhmadAbstract:Accidental reduction in the amount of steel in continuous reinforced concrete (RC) floor slab is a typical problem that might occur due to an error in design, unclear drawings, or overlooked verification of reinforcement prior to concrete casting. Existence of such deficiencies would compromise the load capacity and serviceability of RC floor slab. This research examines the effectiveness of using fiber-reinforced polymers (FRP) to improve the structural response of flexure-deficient continuous RC slab strips. The study comprised experimental testing and finite elements (FE) modeling. Sixteen two-span RC slap strips, 400 x 125 x 3800 mm each, were tested. Test parameters included the deficiency location, strengthening regime, and amount of FRP. The unstrengthened slab strip deficient in the Sagging Region had 22% lower load capacity and 64% higher deflection-based ductility index compared with those of its counterpart deficient in the hogging Region. Strengthening with FRP improved the load capacity and stiffness of the deficient slab strips. The FRP strengthening tended to decrease the ductility index of the slab strips deficient in the Sagging Regions. Conversely, the ductility index of the slab strips deficient in the hogging Region tended to increase after strengthening. The strength gain caused by strengthening was in the range 29% to 69% for the slab strips deficient in the Sagging Regions and 14% to 44% for those deficient in the hogging Region. Increasing the amount of FRP resulted in an increase in the load capacity but the additional strength gain was, generally, not proportional to the added amount of FRP. Increasing the amount of FRP had, typically, less significant effect on the load capacity of the slabs deficient in the hogging Region than in the Sagging Region. Strengthening of deficient Regions reduced the moment redistribution ratios. The ratios further decreased as the amount of FRP in the deficient Region increased. A maximum moment redistribution ratio of +32% was recorded for the strengthened slab strips. The FE model developed in this study predicted the nonlinear structural response of the tested continuous RC slab strips with a high level of accuracy. The numerical and experimental results were in good agreement
Alshawa, Jafer Husni - One of the best experts on this subject based on the ideXlab platform.
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FLEXURAL STRENGTHENING OF ONE-WAY CONTINUOUS REINFORCED CONCRETE SLABS WITH CUTOFFS IN Sagging AND HOGGING RegionS Jafer Husni
Scholarworks@UAEU, 2014Co-Authors: Alshawa, Jafer HusniAbstract:Installation of cutouts in existing reinforced concrete (RC) floor slabs to accommodate utility services reduces the slab load capacity and ductility. This research examines the effectiveness of using near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) reinforcement to improve the flexural response of continuous RC slabs with cutouts. The study comprised experimental testing and analytical modeling. A total of eleven two-span RC slab strips, 400 x 125 x 3800 mm each, were tested. Test parameters included the location of the cutout, and amount and distribution of the NSM-CFRP reinforcement between the Sagging and hogging Regions. Installation of a cutout in the Sagging Region reduced the load capacity and ductility index by 27% and 12%, respectively. When the cutout was installed in the hogging Region, a 23% reduction in both load capacity and ductility index was recorded. The NSM-CFRP strengthening fully restored the original load capacity of all deficient specimens, except one specimen with a cutout in the hogging Region where only 90% of the original load capacity was restored. The enhancement in load capacity due to strengthening was in the range of 53% to 81% for the specimens with a cutout in the Sagging Region and 18% to 54% for the specimens with a cutout in the hogging Region. The ductility index of the specimens strengthened in the Sagging Region only was, on average, 16% lower than that of the control specimen, whereas for the specimens strengthened in the hogging Region only, the ductility index was almost the same as that of the control slab. For the specimens heavily strengthened in both Sagging and hogging Regions, the ductility index was on average 40% lower vii than that of the control slab. A maximum moment redistribution ratio of 26% was recorded for the continuous RC slabs strengthened with NSM-CFRP. An analytical model that can predict the load capacity of two-span RC slab strips containing cutouts and strengthened with NSM-CFRP has been introduced. The ratio of the predicted to measured load capacity was in the range of 0.74 to 1.02 with an average of 0.85, standard deviation of 0.09, and coefficient of variation of 10%
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Flexural Strengthening of One-Way Continuous Reinforced Concrete Slabs with Cutoffs in Sagging and Hogging Regions
Scholarworks@UAEU, 2014Co-Authors: Alshawa, Jafer HusniAbstract:Installation of cutouts in existing reinforced concrete (CR) floor slabs to accommodate utility services reduces the slab load capacity and ductility. This research examines the effectiveness of using near-surface-mounted (NSM) carbon fiber reinforced polymer (CFRP) reinforcement to improve the flexural response of continuous RC slabs with cutouts. The study comprised experimental testing and analytical modeling. A total of eleven two-span RC slabs strips, 400 x 125 x 3800mm each were tested. Test parameters included the location of the cutouts, and amount and distribution of the NSM-CFRP reinforcement between the Sagging and hogging Regions. Installation of a cutout in the Sagging Region reduced the load capacity and ductility index by 27% and 12% respectively. When the cutout was installed in the hogging Region, a 23% of reduction in both load capacity and ductility index was recorded. The NSM-CFRP strengthening fully restored the original load capacity of all deficient specimens, expect one specimen with a cutout in the hogging Region where only 90% of the original load capacity was restored. The enhancement in load capacity due to strengthening was in the range of 53% to 81% for the specimens with cutout in the hogging Region. The ductility index of the specimens strengthened in the Sagging Region only was, on average, 16% lower than that of the control specimen, whereas for the specimens strengthened in the hogging Region only, the ductility index was almost the same as that of the control slab. For the specimens heavily strengthened in both Sagging and hogging Regions, the ductility index was on average 40% lower than that of the control slab. A maximum moment redistribution ratio of 26% was recorded for the continuous RC slabs strengthened with NSM-CFRP. An analytical model that can predict the load capacity of two-span RC slab strips containing cutouts and strengthened with NSM-CFRP has been introduced. The ratio of the predicted to measured load capacity was in the range of 0.74 to 1.02 with an average of 0.85, standard deviation of 0.09, and coefficient of variation of 10%
Shiming Chen - One of the best experts on this subject based on the ideXlab platform.
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Required and available moment redistribution of continuous steel–concrete composite beams
Journal of Constructional Steel Research, 2008Co-Authors: Shiming Chen, Yuanlin JiaAbstract:Abstract Based on the ultimate limit state analysis, the required moment redistribution to enable full plastic mechanism for continuous composite beams is derived. The composite beams studied are continuous over the internal support and with a uniform section along the beams which are one of the conventional steel structural forms in Chinese construction practice for buildings and medium span bridges. It is illustrated that the required moment redistribution for the beam increases as the ratio of negative to positive moment resistance reduces, but decreases as the span difference, or the difference of load in the two spans increases. A method to assess the available moment redistribution based on the rotation capacity at the notional plastic hinges of a composite beam is developed. The potential moment redistribution in a continuous composite beam is also assessed when the available rotation capacity at the notional hinge fails to satisfy the required capacity capable of a plastic design. For a continuous composite beam to develop full plastic design, the available moment redistribution for the beam should be greater than or at least equal to the moment redistribution required, hence the full moment redistribution from the hogging Region to the Sagging Region in the beam is capable. The derived available moment redistributions agree with the test results and computer simulations, but in a general lower bound of the strength capacity. An example is given and the results are compared with that based on the moment redistribution proposed in the present Chinese design code for steel–concrete composite beams. The present study provide a design approach to assess the load carrying capacity for a continuous composite beam based on the available moment redistribution capable depending on the rotation capacity or the force ratio etc rather than a fixed value of moment redistribution proposed, so that in most cases, an economic design is capable.
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load carrying capacity of composite slabs with various end constraints
Journal of Constructional Steel Research, 2003Co-Authors: Shiming ChenAbstract:Abstract In many cases, the load carrying capacity of composite slabs depends on the shear-bond resistance at the sheet-concrete interface. At the ultimate state, the tension forces in the hogging Region of a continuous composite slab are mainly transferred by the negative bending reinforcement and the shear-bond resistance in the Region do not significantly influence the load carrying capacity of the slab. To identify the shear-bond action in composite slabs, seven simply supported one-span composite slabs and two continuous composite slabs were tested. Different end restraints had been used in the simply supported slabs. The slabs with end anchorage of steel shear connectors were found to bear a higher shear-bond strength than that of slabs without end anchorage. The shear-bond strength was calibrated based on a linear regression of the test results of the one-span composite slabs with end anchorage. The prediction of the shear-bond resistance was also found in close agreement with the vertical shear force at the onset of the initial shear-bond slip in the two-span continuous composite slabs. It is suggested that the shear-bond slip model be reasonable to predict the shear-bond resistance of a continuous composite slab. However, the shear span of the continuous composite slabs must be related to the Sagging Region, which could be derived on an elastic analysis base, or simply taken as 0.8 L for the side span and 0.6 L for the interior span. At the onset of the initial shear-bond slip, the mean ratios of the vertical shear force to shear-bond resistance ( V e V u ) are 1.065 for the one-span slabs and 1.165 for the two-span continuous composite slabs, which are on the safe side. Because of the shear-bond failure at the sheet-concrete interface, composite slabs would not be capable of developing full plastic moments in the spans.
Dezi L. - One of the best experts on this subject based on the ideXlab platform.
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Response uncertainty evaluation of continuous steel-concrete composite girders designed with plastic theory
Aesse Stampa, 2009Co-Authors: Zona A., Barbato M., Dall'asta A., Dezi L.Abstract:Continuous steel-concrete composite girders are extensively used for construction of short and medium span bridges. In the Sagging Regions, where the compressed flange of the steel beam is connected to the reinforced concrete slab, the cross sections generally belong to class 1 or class 2 (compact sections) and plastic design is acceptable. In the hogging Regions the cross sections commonly belong to class 3 or class 4 (slender sections), thus there is insufficient ductility for plastic design and elastic verification is required. However, in this combined design approach that uses the cross section plastic resistance in the Sagging Regions and the elastic resistance in the hogging Regions, the design must satisfy the condition that the plastic moment in the Sagging Region can develop while still leaving the bending moment resisted by the hogging Regions sufficiently far from the elastic limit. The objective of this work is to assess this combined elastic-plastic design approach for continuous composite girders by using probabilistic nonlinear finite element analysis
Yuanlin Jia - One of the best experts on this subject based on the ideXlab platform.
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Required and available moment redistribution of continuous steel–concrete composite beams
Journal of Constructional Steel Research, 2008Co-Authors: Shiming Chen, Yuanlin JiaAbstract:Abstract Based on the ultimate limit state analysis, the required moment redistribution to enable full plastic mechanism for continuous composite beams is derived. The composite beams studied are continuous over the internal support and with a uniform section along the beams which are one of the conventional steel structural forms in Chinese construction practice for buildings and medium span bridges. It is illustrated that the required moment redistribution for the beam increases as the ratio of negative to positive moment resistance reduces, but decreases as the span difference, or the difference of load in the two spans increases. A method to assess the available moment redistribution based on the rotation capacity at the notional plastic hinges of a composite beam is developed. The potential moment redistribution in a continuous composite beam is also assessed when the available rotation capacity at the notional hinge fails to satisfy the required capacity capable of a plastic design. For a continuous composite beam to develop full plastic design, the available moment redistribution for the beam should be greater than or at least equal to the moment redistribution required, hence the full moment redistribution from the hogging Region to the Sagging Region in the beam is capable. The derived available moment redistributions agree with the test results and computer simulations, but in a general lower bound of the strength capacity. An example is given and the results are compared with that based on the moment redistribution proposed in the present Chinese design code for steel–concrete composite beams. The present study provide a design approach to assess the load carrying capacity for a continuous composite beam based on the available moment redistribution capable depending on the rotation capacity or the force ratio etc rather than a fixed value of moment redistribution proposed, so that in most cases, an economic design is capable.
