الفهرس 
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Abstract
The main objective of this research is to study the influence of steel fibers on the behavior of lightweight concrete (LWC) with low and normal concrete grade, and to know the main role of steel fibers on the concrete properties and shear capacity in general. Furthermore, to study the effect of some variable parameters on the behavior and to improve ductility, stiffness, crack width and ultimate capacity such as: (1) volume of fiber (Vf = 0%, 0.50%,
0.75%, and 1.0%); (2) fiber aspect ratio (Lf /f = 50, 62.5 and 75); (3) longitudinal reinforcement ratio (/max = 0.3,0.4 and 0.5). In addition to use a modified approach to
develop strut and tie model to account for steel fiber in LWC. Also, to enhance the ductility in
compression nodal zones and the effect of tension stiffening on flexural reinforcement and to discover the influence of the distribution of steel fiber as a randomly on the resisting against deformation and on the strength.
Experimental and numerical programs were used to study the behavior of LWC deep beams with steel fiber. For the experimental program, eight beams were divided into four groups each has two specimens. All specimens were tested and loaded in the lab with two concentrated loads with span to depth ratio (a/d) =1.0. The concrete used has an average
compressive strength of 28 MPa as a result from three different concrete mixes using standard
cubes (150 x 150 x150 mm). The beams were reinforced with flexural and web
reinforcement, (vertical and horizontal). The tested deep beams have constant dimensions (2200 mm x 800 mm x150 mm) representing one fourth of full scale. The first group consists
of two control specimens has / max = 0.3, fiber content = 0.0% and 0.50% for B1 and B2 respectively, fiber aspect ratio = 0 and 62.5 for B1 and B2 respectively, to study the effect of
steel fibers on the behavior. The second group of specimens has / max = 0.4 and 0.50, fiber content = 0.5 %, and fiber aspect ratio = 62.5 to study the effect of main steel. The third
group of specimens has / max = 0.3, fiber content = (0.75% and 1.0%), fiber aspect ratio = 50 to study the effect of fiber content on the behavior. The fourth group of specimens has /
max = 0.3, fiber content = 0.5%, fiber aspect ratio = 75 and 50 to study the effect of fiber aspect ratio on the behavior. Hooked end fiber type was used with length 40 to 60 mm and 0.8
mm diameter as a random shape for all the tested specimens. The concrete mixes contents (cement- sand-coarse aggregate-Sika fume-super plasticizer- foam-water) and the water/cement ratio was (0.4 to 0.5) with 21 kg/m3 foam. Sika Air used to add the trapped air to concrete and to get lightweight concrete. The numerical study was carried out using
ANSYS V.15 program to study the effect of some parameters not included in the
experimental program. Also a modified strut and tie model (STM) was used to analyze and design LWC deep beams according to the Egyptian and the ACI Codes. The average concrete cylindrical compressive strength of LWC is 33 MPa. The
accuracy is 0.3% from using Egyptian Code and ACI to calculate the load capacity of beams
Pu from (STM). from decreasing (a/d) ratio of course delay the appearance the first crack of shear and flexure. Comparing the results with control specimen, it observed that the cubic
compressive strength, split tensile strength and cylindrical compression strength are increased by (21.67%, 25.2%, and 25.1%) for specimen with content of steel fiber,in addition to the deformation characteristics and strength was improved than beam with no fiber content. The workability of concrete increased with using Sika Air. from the comparisons between
analytical study and experimental program the standard deviation shown that (PuFE /PuEXP) is 2.02% and (∆u(E/(∆uEXP) is 7.16%. In fact, the results are compared between FE analysis by ANSYS and the experimental results in addition to equations from codes, and the obtained results were acceptable.