The Experts below are selected from a list of 118614 Experts worldwide ranked by ideXlab platform
Omar Qarani Aziz - One of the best experts on this subject based on the ideXlab platform.
-
Shear Behavior of dry and epoxied joints in precast concrete segmental box girder bridges under direct Shear loading
Engineering Structures, 2019Co-Authors: Ghafur H Ahmed, Omar Qarani AzizAbstract:Abstract Precast segmental concrete bridge construction involves multiple concrete elements joint together by post-tensioning. The joints that represent locations of discontinuity are the prominent factors affecting the overall Behavior of segmental bridges. In this study, a series of single cell, box shaped specimens, with a geometry closely resembling the keyed joint of actual segments, were subjected to direct Shear test. The joints are flat and keyed, dry and epoxied, having web and flange keys. Tests were carried out to assess the Shear capacity, Shear Behavior, crack propagation and deformations of different kinds of joints. It was found that epoxy can minimize joint imperfections and letting Shear stresses to be distributed uniformly. Perfect joint closure and Shear transfer was observed for epoxied joint when fully posttensioned immediately. Shear capacity of epoxied joints had consistently higher than dry joints by 25–28%; while, the failure of the epoxied joints was found to be sudden and brittle. The average Shear transfer of a single key is higher for specimens with less number of keys. Four flange Shear keys are capable to increase Shear capacity by 14% and the elastic stiffness of the joints by 73%. It was determined that, the AASHTO design criterion can conservatively predict Shear capacity of all kinds of epoxied joints and flat dry joints; however, it is greatly overestimating the Shear capacity of multi-key dry joints.
-
influence of intensity eccentricity of posttensioning force and concrete strength on Shear Behavior of epoxied joints in segmental box girder bridges
Construction and Building Materials, 2019Co-Authors: Ghafur H Ahmed, Omar Qarani AzizAbstract:Abstract Precast concrete segmental bridges have the advantages of rapid construction speed, excellent quality control and low cost. The structural Behavior of segmental bridges largely depends on the Behavior of the joints between segments. In this study, a series of specimens with epoxied joints, were tested to assess Shear Behavior of box girder segmental bridges, under direct Shear loading. The study parameters were: confining stress level, prestressing eccentricity, and the concrete compressive strength. Shear Behavior, Shear capacity, and crack patterns of the joints were investigated as well. Mechanisms of sequential Shear failure and a detailed analysis of failure events are also presented. It was found that the Shear capacity of the joints increased approximately 40% for each increased 50% of the confining stress. Eccentricity of prestressing force wasn’t affecting the elastic Behavior of the joints, but its role was appeared obviously at the plastic stage. By increasing concrete compressive strength up to 70 MPa, the joint Shear capacity can be increased significantly. The experimental results of the current study and results of other researchers were compared with design provisions. It was seen that the relationships tended to underestimate the Shear strength of keyed epoxied specimens by an average value of 11.3%.
P Waldron - One of the best experts on this subject based on the ideXlab platform.
-
punching Shear Behavior of fiber reinforced polymers reinforced concrete flat slabs experimental study
Journal of Composites for Construction, 2003Co-Authors: Abdel Wahab Elghandour, Kypros Pilakoutas, P WaldronAbstract:This paper presents the results of a two-phase experimental program investigating the punching Shear Behavior of fiber reinforced polymer reinforced concrete (FRP RC) flat slabs with and without carbon fiber reinforced polymer (CFRP) Shear reinforcement. In the first phase, problems of bond slip and crack localization were identified. Decreasing the flexural bar spacing in the second phase successfully eliminated those problems and resulted in punching Shear failure of the slabs. However, CFRP Shear reinforcement was found to be inefficient in enhancing significantly the slab capacity due to its brittleness. A model, which accurately predicts the punching Shear capacity of FRP RC slabs without Shear reinforcement, is proposed and verified. For slabs with FRP Shear reinforcement, it is proposed that the concrete Shear resistance is reduced, but a strain limit of 0.0045 is recommended as maximum strain for the reinforcement. Comparisons of the slab capacities with ACI 318-95, ACI 440-98, and BS 8110 punching Shear code equations, modified to incorporate FRP reinforcement, show either overestimated or conservative results.
Ghafur H Ahmed - One of the best experts on this subject based on the ideXlab platform.
-
Shear Behavior of dry and epoxied joints in precast concrete segmental box girder bridges under direct Shear loading
Engineering Structures, 2019Co-Authors: Ghafur H Ahmed, Omar Qarani AzizAbstract:Abstract Precast segmental concrete bridge construction involves multiple concrete elements joint together by post-tensioning. The joints that represent locations of discontinuity are the prominent factors affecting the overall Behavior of segmental bridges. In this study, a series of single cell, box shaped specimens, with a geometry closely resembling the keyed joint of actual segments, were subjected to direct Shear test. The joints are flat and keyed, dry and epoxied, having web and flange keys. Tests were carried out to assess the Shear capacity, Shear Behavior, crack propagation and deformations of different kinds of joints. It was found that epoxy can minimize joint imperfections and letting Shear stresses to be distributed uniformly. Perfect joint closure and Shear transfer was observed for epoxied joint when fully posttensioned immediately. Shear capacity of epoxied joints had consistently higher than dry joints by 25–28%; while, the failure of the epoxied joints was found to be sudden and brittle. The average Shear transfer of a single key is higher for specimens with less number of keys. Four flange Shear keys are capable to increase Shear capacity by 14% and the elastic stiffness of the joints by 73%. It was determined that, the AASHTO design criterion can conservatively predict Shear capacity of all kinds of epoxied joints and flat dry joints; however, it is greatly overestimating the Shear capacity of multi-key dry joints.
-
influence of intensity eccentricity of posttensioning force and concrete strength on Shear Behavior of epoxied joints in segmental box girder bridges
Construction and Building Materials, 2019Co-Authors: Ghafur H Ahmed, Omar Qarani AzizAbstract:Abstract Precast concrete segmental bridges have the advantages of rapid construction speed, excellent quality control and low cost. The structural Behavior of segmental bridges largely depends on the Behavior of the joints between segments. In this study, a series of specimens with epoxied joints, were tested to assess Shear Behavior of box girder segmental bridges, under direct Shear loading. The study parameters were: confining stress level, prestressing eccentricity, and the concrete compressive strength. Shear Behavior, Shear capacity, and crack patterns of the joints were investigated as well. Mechanisms of sequential Shear failure and a detailed analysis of failure events are also presented. It was found that the Shear capacity of the joints increased approximately 40% for each increased 50% of the confining stress. Eccentricity of prestressing force wasn’t affecting the elastic Behavior of the joints, but its role was appeared obviously at the plastic stage. By increasing concrete compressive strength up to 70 MPa, the joint Shear capacity can be increased significantly. The experimental results of the current study and results of other researchers were compared with design provisions. It was seen that the relationships tended to underestimate the Shear strength of keyed epoxied specimens by an average value of 11.3%.
Abdel Wahab Elghandour - One of the best experts on this subject based on the ideXlab platform.
-
punching Shear Behavior of fiber reinforced polymers reinforced concrete flat slabs experimental study
Journal of Composites for Construction, 2003Co-Authors: Abdel Wahab Elghandour, Kypros Pilakoutas, P WaldronAbstract:This paper presents the results of a two-phase experimental program investigating the punching Shear Behavior of fiber reinforced polymer reinforced concrete (FRP RC) flat slabs with and without carbon fiber reinforced polymer (CFRP) Shear reinforcement. In the first phase, problems of bond slip and crack localization were identified. Decreasing the flexural bar spacing in the second phase successfully eliminated those problems and resulted in punching Shear failure of the slabs. However, CFRP Shear reinforcement was found to be inefficient in enhancing significantly the slab capacity due to its brittleness. A model, which accurately predicts the punching Shear capacity of FRP RC slabs without Shear reinforcement, is proposed and verified. For slabs with FRP Shear reinforcement, it is proposed that the concrete Shear resistance is reduced, but a strain limit of 0.0045 is recommended as maximum strain for the reinforcement. Comparisons of the slab capacities with ACI 318-95, ACI 440-98, and BS 8110 punching Shear code equations, modified to incorporate FRP reinforcement, show either overestimated or conservative results.
Brahim Benmokrane - One of the best experts on this subject based on the ideXlab platform.
-
Shear Behavior of frp reinforced concrete deep beams without web reinforcement
Journal of Composites for Construction, 2013Co-Authors: Ahmed Sabry Farghaly, Brahim BenmokraneAbstract:AbstractThe Shear Behavior of four full-scale deep beams reinforced with carbon and glass fiber reinforced polymer (FRP) bars were investigated. The beams were supported over a 3,000-mm span with a projection of 1,000 mm on each side, with a cross section of 300 mm in width and 1,200 mm in depth, and tested to failure under four-point loading. The primary test variables included the longitudinal reinforcement ratio and the reinforcement type. The reinforcement ratio and concrete compressive strength had a clear effect on the ultimate capacity and deflection characteristics while reinforcement type no clear effect of the Behavior of the tested beams. The crack patterns, mode of failure, and strains in concrete and reinforcement were also reported. The formation of the tie action was confirmed by the nearly uniform strain distribution in the longitudinal reinforcement. The results are compared to the strut-and-tie model, demonstrating the necessity of including the effect of web reinforcement and the import...
