For more than a decade, externally bonded carbon fiber reinforced polymer (CFRP) composites successfully utilized in retrofitting reinforced concrete structural elements. The function of CFRP reinforcement in increasing the ductility of reinforced concrete (RC) beam is essential in such members. Flexural and shear behaviors, ductility, and confinement were the main studied properties that used the CFRP as a strengthening material. However, limited attention has been paid to investigate the energy absorption of torsion strengthening of concrete members, especially two-span concrete beams. Hence, the target of this work is to investigate the effectiveness of CFRP-strengthening technique with regard to energy absorption of two-span RC beams subjected to pure torsion. The experimental program comprises the investigation of two groups; the first group comprises eight un-strengthened beam specimens, while the second group consists of eight strengthened beam specimens tested under torsional forces. The energy absorption capacity measured from the area under the curve of torque-angle of twist for tested beams. Two parameters were studied, the influence of concrete compressive strength and the angle of a twist. Experimental results indicated that all beams wrapped with CFRP sheet display superior torsional energy absorption capacity compared to the control specimens. The energy absorption may consider as a safety index for the torsional capacity of two-span RC beams under service loadings. Therefore, it is possible to avoid structural as well as material damages by understanding the concept of energy absorption that is one of the important experimental findings presented in this study.
Six I-section steel beams had been fabricated and tested to understand the influence of prestressing strand on the load deflection behavior of steel beam. All tested beams are simply supported having the same gross sectional area with clear span (2850) mm, five beams strengthened by two low relaxation seven wire strands, while sixth beam is the reference one. The strengthening beams were subjected jacking stress equal to (1120MPa) and subdivided according to prestressing strand positions (eccentricity). From the experimental tests, it can be noted that, the load deflection curves for strengthened beams are stiffer as compared with reference beam and the percentage of ductility for strengthened beams were decreased when the eccentricity positions change form (0 to 96)mm respectively, on the other hand, the percentage of increasing in maximum applied load for strengthened beams were increased with increasing of strands eccentricity and the maximum applied load reaches to 61.74% as compared with reference, also, the percentage increasing in maximum deflection at middle span for strengthened beams decreases with increasing of strands eccentricity and the minimum percentage of decreasing at middle span of strengthened specimens reaches to 36.31% as compared with the reference beam.
This paper presents experimental study of structural behavior of thin Reactive Powder Concrete (RPC) wall panels subjected to axial eccentric uniformly distributed loading with varying steel reinforcement ratio (ρ) and aspect ratio (AR= H/L). The experimental program included testing of six two-way thin RPC wall panels, fixed at all sides and applying the load axially with eccentricity equal to (t/6). The results indicates that the ultimate strength of the RPC wall panel decreases with increase in AR from (1.25 to 2.00) for panels with H/t = 18.75. The decreasing in ultimate load for RPC wall panels is about 16% and 38.7%, for an increase in AR from 1.25 to 2.0 for panels with ρ = 0.012566, and about 6.38% and 36.2%, for an increase in AR from 1.25 to 2.0 for panels with ρ = 0.007854.The ultimate strength of RPC wall panel increases with an increase of percentage of steel reinforcement ratio (ρ). For an increase in reinforcement ratio from ρ = 0.007854 to ρ = 0.012566 the increase is about (6.4, 4.76 and 2.22) % for walls with AR (1.25, 1.50 and 2.00) respectively. The lateral deflection decrease with the increase of percentage of steel reinforcement ratio from (0.007854 to 0.012566) under two-way in plane loading, When AR= 1.25 the reduction about (1.22 times) and When AR= 2.00 the reduction about (1.11 times). The lateral deflection of RPC wall panels decrease with the increase in aspect ratio.
The purpose of this paper was concerned of the behavior of six samples of deep beams under the influence of pure torsion. Such samples were self-compacting concrete (SCC) and two ratios of Steel Fibers (SF (were also added (0.75 % and 1.5 %). This study examined the behavior of the samples when pure torsion was applied and reacted to angles of torsion, longitudinal strains and concrete strains. It was obvious from the results of the test that the addition of steel fiber to the SCC mixture increased the strength of the compression and tensile strength, which increased the hardness of the samples, thereby decreasing the response of the samples to the angle of twisting, longitudinal strains of concrete and concrete strains.
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