رافد سعيد عطية الجنابي

High presentation concrete is chiefly cast-off in multistory constructions where it expressively lessening the measurements of columns, which styles it a more economical excellent for building than normal strength concrete. In seismic area, high enactment concrete posses more complications, since it has less ductility in comparison with normal concrete. The purpose of this research is to detect the combined consequence of fibers and ties on the conduct of reinforced columns and to advance their ductility. This study presents an investigational valuation of strength and ductility of ordinary and high presentation concrete short columns limited by tie with and without steel fibers and polypropylene fibers. Five square concrete columns (100 × 100 × 1000) mm were established. The variables considered were, concrete strength, volume percentage of longitudinal reinforcement (4.52%), volumetric ratio of lateral reinforcement (spacing between ties) (5.58%) volume fraction of fibers (0.5% and 0.75%), form of fibers (hooked steel fiber and polypropylene) and phase ratio of steel fibers (100) (length 50 mm and diameter 0.5 mm) and (60) (length 30 mm and diameter 0.5 mm). The column specimens were tested under axial load. The values presented that the adding of steel fibers (volume friction 0.75% and aspect ratio 100) for high presentation concrete improves the compressive strength, splitting tensile strength, flexural strength, and static modulus of elasticity. Commonly, the effects also exhibited that the adding of fibers to usual and high act concrete upsurges the strength and advances their performance.

A hollow reinforced concrete T-beams were investigated under the effect of pure tension experimentally, which are made of reactive powder concrete (RPC). This concrete was produced with adding steel fiber and silica fume in different dosages. The present work aims at studying the effect of the steel fiber volumetric ratio (Vf) and silica fume content (Sf) on the behavior of hollow T-beam under pure torsion and so, on its torsional capacity. For this purpose T-beams were simply supported with 1400 mm length, 100 mm web width, flange width 220 mm and 160 mm height were tested. It was found that the addition of 2% steel fibers to concrete mix increased the cracking and ultimate torque of the RPC hollow T-beam. An increase of 184% in cracking torque and 66% in ultimate torque for hollow section was achieved while the other properties kept constant.

A study of the performance of reinforced normal (ordinary) (NC) concrete and Reactive Powder Concrete (RPC) of Beam-Column Joints under reversed cyclic loading was carried out. For this purpose, specimens of full-scale 3 m in height reinforced beam-column joints made with NC and RPC were investigated. RPC joints were made by mixing 20% of the cement weight using silica fume with adding steel fibres in a dosage of 1.5% of the volume fraction of concrete. The studied properties of hardened concrete were compressive strength, splitting tensile strength and modulus of elasticity. The mechanical properties of joints of RPC type were reasonably improved rather than those of ordinary concrete (NC) joints. It was found that the applied load for RPC joint increased by 26.5 % than the NC joint. The results of the current investigation showed the ability of RPC structural joints to adequately resist vertical and lateral loads in comparison with those of NC joints, this is attributed to the improvement of the mechanical properties and general behaviour of RPC joints. Also, enhancement of the general behaviour of RPC Beam-Column Joints was shown by the crack pattern, load-deflection trend and amount of strains.

This study investigates the flexural behavior of four reinforced concrete beams. The beams were composed by adding steel plates which have different thickness (2, 3, and 5 mm) in the tension zone to invention out the consequence of the altered plate thicknesses on the flexural behavior on these beams, and the consequence of using typical concrete. The first beam is made of normal concrete (non composite beam) additionally, the other beams are prepared using usual concrete (composite beams by plates). The connection between the concrete and steel plate was by using shear connector, to gain the effective connection between the concrete and steel plate. The study consists of two parts: the first part is an experimental work through casting and testing beams, while in the second part, an analysis has been conducted to the tested specimens by using a three dimensional nonlinear finite element method by ANSYS program (Version 18.1). The increase of ultimate strength for plated beam compared with unplated beam (73%, 86% and 161%) with increase the thickness steel plate (2, 3 and 5) respectively. concrete strain, crack width and numbers of cracks decrease with increasing the thickness of steel plate.

Torsion is resisted well by locked system of reinforcement, due to the blood nature of the torsion induced-shear flow stresses in a beam. Therefore, it will be more effective to have strengthening schemes, which are wrapped in closed form around the cross section. But strengthening with U wrap (three sides) or strengthening in the web and flange unconnectedly is more useful because of the unreachability of the entire cross section due to addition of flange in uniform beam – slab construction (T section of interior beam). This work aims at studying the strengthening of T beams in torsion by using carbon fiber reinforced polymer (CFRP). The CFRP laminates will be used for strengthening previous to loading. The experimental work includes investigation of twelve reinforced concrete T beams tested under pure torsion. The first beam was the reference beam, without CFRP. The second beam was a simple concrete beam. The remaining ten beams. Variables considered in the test program include; effect of flange strengthening, effect of fiber orientation (90° or 45° CFRP strips with respect to the longitudinal axis), effect of using additional longitudinal CFRP strips with transverse CFRP strips, effect of bolt anchoring CFRP strips in the web and flange and effect of continuous CFRP strips between web and flange (isolated T section). Test results were discussed based on torque – twist behavior, beam elongations, CFRP strain, concrete strain and influence of CFRP on cracking torque, ultimate torque and failure modes.

The qualities confirmed in this study include silica fume content (0%, 10%, and 20%) by replacing equivalent weight of cement in concrete. By volume fraction of concrete, polypropylene fibers were included in the mix. (0 percent, 0.20 percent, and 0.40 percent). Three deep specimens of reinforced concrete beams were evaluated, it measures (100X300) mm in cross-section and 1000 mm in length. Three beams are preliminary based on the relationship between shear span (a) and depth (d). The ratio (a/d) was discarded (1), by varied holding polypropylene fibers with silica fume varying percentages of substitute for different polypropylene fibers and silica fume product from recycling, it is attained from the smoke expanding through the chimneys of the furnaces by the condensation progression, were added from volume fraction, the (a/d) ratio was employed. The experimental test results improved concrete properties and enhanced the general behavior for substantial crack in reinforced concrete beams pattern when, load-deflection, also strains were explored. The finite element model (ABAQUS –version19) employed is capable of imitating in this study the behavior of externally containing silica fume with polypropylene fibers beams failed in shear.