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.
The main goal of this research paper is to investigate the response of the RC rectangular columns under loading simultaneously exposed to fire by using experimental study. The number of test columns were seventeenth columns. The dimension for these columns was 1600mm for length and 150mmx150mm for the cross-section. The columns were tested under axial load with two different types of eccentricity 60 mm 100mm, while the third type of loading is tested as a beam. The eccentric compression load was applied by using top and bottom cap with a column bracket. The eccentric load was applied simultaneously with fire. The test was performed under a high temperature of (400°C, 600°C, and 900°C) on the side of a compression face. At each temperature burning, cooling by two techniques of cooling, and normal cooling (by open air) and fast cooling (by direct water). The experimental results show decreasing in ultimate load capacity with increasing of temperature burning, ultimate load, load-deflection curve, strain profile, neutral axis, moment-curvature, and ductility.
Now, using of geogrids as strengthening material are extend used, especially to enhancement of concrete elements as inter layers concrete applications, eight beams were tested to explain the effect of geogrid on the behavior of reinforced concrete beams. Beams tested had equal cross-sectional dimension (100 mm x 200 mm), compressive strength (f’c = 30 MPa), with a simply span length equals 1150 mm, with shear reinforcement (Ф4 @100mm C/C) and subjected to two point load. The tested beams were divided into two groups according to the presence of geogrid layer, with and without geogrid. Each group consists of four specimens, which were sub-divided according to the flexural reinforcement ratio that ranges from (0 to 0.0263). During the tests, it was noted that, the load deflection curve for beams with geogrid layer were stiffer and the percentage of stiffening was increased with increase of the flexural reinforcement ratio. The maximum applied load for beams with geogrid layer were higher than conventional beams without geogrid layer under the same conditions, while, the deflection values for beams with geogrid layer was lower than conventional beams without geogrid layer. The first crack load of beams with geogrid was greater than conventional beams without geogrid layer. So, the geogrids layer offer great enhancements to concrete properties and performance from the first cracking load, load-deflection response, reduce the cracks width and number and ultimate strength of tested in comparison to the conventional beams.
Thirteen simply supported steel beams were tested to explain the effect of strengthening by external prestressing strands. All of these beams have the same steel section, clear span length and strengthening by two external prestressing strands. The tested beams are divided into two categories according to existing of external prestressing strands, the first category consists of one steel beam as a reference, while, the second group deals with steel beams strengthening by external prestressing strands are divided into two groups according to jacking stress. Each group consists of six steel beams divided according to the eccentricity location of prestressing strand ranging from (0 to 165) mm at jacking stress1120.061 MPa and 814.589 MPa respectively. During the teste, it was found that the load deflection curves behavior for the beams strengthening by external prestressing strand are stiffer than the reference beams and the percentage of stiffening is slightly increase with increasing the jacking stress at constant eccentricity. Also, the maximum applied load with increase slightly rising as eccentricity increased at mid span. On the other hand the increasing percentage in maximum deflection decreases when the jacking stress increase from (814.589 to 1120.061) MPa at constant eccentricity locations.
The results of eight reinforced concrete deep beams tested under four point loading condition are reported. The test beams were simply supported and were made with self compacting concrete (SCC). The variables were; web reinforcement and anchorage of tension reinforcement. The test beams were divided into four groups according to the web reinforcement. Each group consists of two beams, one with the anchorage of tension reinforcement and the other without. The nominal cross section was 100 x 300mm and the clear span length was 1100mm. Deflections of beams and cracking patterns were monitored during the tests at different stages of the monotonic loading until failure. The results showed the significance of the web reinforcement and anchorage of tension bars on the strength and failure behavior of SCC deep beams. The ultimate strength of beam without web reinforcement increased to 39% by adding anchorage to the longitudinal tension reinforcement. While the ultimate strength of the beam increased to 16% by adding anchorage to tension reinforcement for beams having web reinforcement that consists of stirrups with horizontal reinforcement.
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