حيدر حسين حريب كمونة

This paper considers the practical application of nonlinear models in the analysis of Steel Fiber Reinforced Concrete Deep Beams. the results of some analyses performed using the reinforced concrete model of the general purpose finite element code ANSYS are presented and discussed. Steel fiber was represented using two approaches. In the first approach its effect in enhancement the mechanical properties of concrete is introduced. This was done by increasing the initial modulus of elasticity, compressive strength, tensile strength, ductility etc. through empirical formulas found in literatures. While the second approach was done by assuming steel fiber as smeared reinforced layers embedded in Solid65 element. Good agreement with the experimental test was obtained by ANSYS solution. Numerical analysis showed that closed solutions were obtained with different representation of steel fiber in different orientations and number of layers. This is because that the smeared layers were assumed in each element of the structure which gave a uniform distribution for the steel fiber in deep beam. It was found that the second approach gave better agreement with the experimental test than the first one. Assuming of steel fiber oriented in two directions with equal ratio may consider the closer one for representation of steel fiber in two dimensional structural members.

This experimental study attempts to investigate the flexural behavior of continuous reinforced concrete (RC) beams strengthened by near-surface-mounted steel bars. The tests were conducted on 11 specimens of 3,000-mm length and cross-sectional dimensions of 150
225 mm. The longitudinal reinforcement of all beams consisted of two f 10 steel bars in the negative and positive moment regions. To ensure that the beams would fail under flexure rather than shear, f 10 stirrups were spaced at 100mm c/c over the entire beam length. The first beam was not strengthened and was considered a control beam. The other specimens were strengthened by near-surface-mounted bars with different development lengths, diameters, and material types, with end-anchors of carbon-fiber-reinforced polymer (CFRP) fabrics. The test was conducted under two-point loads, applied at the center (1,400mm) of the span. The main investigated characteristics were cracking and ultimate loads, crack width, displacement, and failure modes. From the experiments, all the strengthened beams achieved a significant enhancement in ultimate flexural strength by approximately 108% relative to the control beam. In addition, CFRP end-anchorage can eliminate the separation of the concrete cover and demonstrates a significant improvement in ductility.

Local scour downstream of hydraulic structures, such as low head and high head structures, spillways, and culverts is an important research field due to its significant practical value. In this study laboratory experiments were conducted to compute the local scour downstream apron of an ogee spillway under different slopes of apron to study its effect on the characteristics of the scour. Developed physical models for spillway and aprons are installed into the water in the channel where conducted under subcritical flow and clear-water condition by using uniform cohesionless (soil) as bed material with a medium grain size (d50 = 0.65 mm). Four angles of an apron were used (0˚, 2.73˚, 5.19˚, and 7.43˚) to show the effect of the slope for apron on local scour. It is found that the slope of an apron is one of the important parameter to reduce the local scour depth and the extent of scour hole. The influence of slope for aprons angle showed a reduction of about (53, 46, and 35) % in the maximum scour depth and about (33, 49, and 33) % in the maximum scour length compared with horizontal apron for angles (2.73˚, 5.19˚, and 7.43˚), respectively.

A nonlinear finite element study has been conducted to evaluate the efficiency of the technique of strengthening reinforced concrete beams under static loads. No time-dependent effects (creep and shrinkage... etc.) are considered in this work. This concept is based on prestressing of CFRP sheets. In this research program, four reinforced concrete beams were tested to investigate the feasibility of such concept for flexural strengthening. One of the beams was retrofitted with non-prestressed CFRP sheet which was used as the control beam. The rest were retrofitted with prestressed CFRP sheet with three levels of prestressing. The static load was applied at the instant of full prestress load application. Prestress losses were ignored here. CFRP sheets have been simulated using two types of element (SHELL41 and LINK8). Prestressing effects have been represented using two models; the application as axial load and initial axial strain. The results showed that there is a good enhancement in performance of the beams strengthened using the prestressing technique in terms of the cracking loads and deflection occurs at such level of loading. The application of prestressing forces of 9 kN, 16 kN and 22 kN, was found to increase the cracking load by 57%, 106% and 170%, respectively.

The present study deals with numerical analysis of reinforced (RC) simply supported beam strengthened by carbon fiber reinforced polymer (CFRP) element. The two commonly used techniques near surface mounted (NSM) and externally bonded reinforcement (EBR) are considered. For the NSM technique, the two configurations of strengthening by CFRP, rod and sheet, have been used, while Sheet type at bottom surface of beam is used for EBR technique. ANSYS V15 has been employed to achieve the present work. Also study is focused on investigation of some parameters that may affect the performance of strengthened RC beam. Parameter studied here are; effect of NSM CFRP ratio, configuration of CFRP type of reinforcement (rod or sheet), distribution of NSM CFRP rod area through beam width and the effect of simulation of epoxy grove. The results revealed that using higher ratios of CFRP results in considerable improvement in ultimate load capacity, an increment up to 180% in ultimate load capacity can be achieved with increasing the NSM rod ratio from 0.047% to 0.377%. Slight effect of using CFRP sheet instead of CFRP rod has been obtained, the range of influence was 94% - 123%. Also use different diameters of NSM CFRP rod for the same ratio of area decreases the post- cracking stiffness response with significant decrease in ultimate load capacity. The analysis yields that use various model of epoxy-groove between CFRP and concrete have little effect on the behaviour of strengthened beam.

The present study deals with the nonlinear finite element analysis of continuous reinforced concrete (RC) beam strengthened by carbon fiber reinforced polymer (CFRP) sheet against shear. Normal and high strength concrete are investigated. ANSYS V15 program has been used to achieve the present work. Nine beams have been studied. For some beams, longitudinal CFRP sheets have been suggested to be added to study the effect of prestressing on the beam response. Different levels of prestressing have been applied. Also the position and length of such sheets have been considered to determine the best configuration. It is found that increasing prestressing force ratio up to 50% results in an increment in cracking and ultimate loads to about 86% and 36%, respectively. It is also obtained that changing the length of prestressing CFRP sheets in the bottom face of beam (in the positive moment region) has more effect than those in the top face (in the negative moment region). Finally, it is concluded that the prestressing CFRP sheets do not prefer to be extended beyond the inflection points to achieve an improvement in cracking and ultimate loads.