The current research aims to study the effect of impact loads on reinforced concrete beams strengthened by carbon fibers and/or steel wire rope. The use of steel wire rope is suggested as a new economic technique to strengthen and rehabilitate reinforced concrete beams, as well as to fix the fibers that are being used in strengthening. Reinforced concrete beams subjected to impact load using both carbon fibers and steel wire rope were tested, and the results were compared with the results obtained from reference beams, from beams strengthened with steel wire rope only, and from beams strengthened with carbon fibers only. The results of concrete beams strengthened using any of the three methods and subjected to impact loading showed a decrease in maximum deflection, residual deflection, damping time, and in the number of strikes to reach each phase of failure. The best results, however, were attained when strengthening using steel rope with and without the addition of carbon fibers, which improved the values of dynamic deflection, residual deflection, damping time, and the number of strikes to reach each phase of failure, when compared to beams strengthened by CFRP strips only.

The main objective of the research is to study the preparation of one way slabs of ordinary concrete, and then to prepare concrete slabs by replacing the main reinforcing steel with two kinds of steel fibers (ordinary steel fibers and recycled steel fibers) by fraction volumes of 0.125, 0.250, and 0.375%. Also, study the mechanical properties of the mixtures as a ompressive strength, indirect tensile strength, and flexural strength. Concrete slabs of these mixtures have been prepared with specific geometrical dimensions700 * 300 * 70 mm, exposed to line load, to study the bending moment and maximum failure load of these slabs. A concrete mixture was produced after proportionment based on the ACI and casting six cubes tested at the ages of 7 and 28 days where the strength requirements for design were achieved. The main mixtures of research were produced, three cubes for compressive strength testing, twenty one cylinders for indirect tensile strength testing, and twenty one prisms for modulus of rupture testing. Also sixteen concrete slabs were prepared, two of them were reference slabs without reinforcing steel, the other two with main reinforcing steel only, six of them replaced by the main reinforcing steel with ordinary steel fibers, and the last six replacing the main reinforcing steel with recycled steel fibers. The results showed that both the failure load and the resultant deflection in concrete slabs decreased by (20.09%, 51.91%) for maximum load and by (35.18%, 81.48%) compared to the reference slabs when replacing the main reinforcing steel with steel fiber, also by (25.72%, 38.29%) to failure load and (38.88%, 79.63%) for the deflection compared to the reference slabs when replacing the main reinforcing steel with recycled steel fibers. The best value for maximum load and deflection could be obtained from this study was at 0.125% replacement ratio of the main reinforcing steel with recycled steel fibers, the highest value of ductility was 3.77 at the replacement ratio of 0.250% of the main reinforcing steel with the ordinary steel fibers, also the highest hardness value was 11.67 kN / mm with the replacement ratio of 0.125% of the main reinforcing steel with recycled steel fibers and increased by 61.85% than the hardness of the reference slabs.

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The study involves strengthening timber beams by known jute fibers with various forms of strengthening and comparison the bending test results with the control beams and beams strengthened by steel plates. Twenty-two timber specimens with dimensions (70×100×1000) mm are divided into eight groups and loaded under a one-point load. The work is carried out to study the flexural and shear strengthening effects on behavior of the tested beams. Four specimens wrapped in U technique in single and double layers, along the whole length of the beam in full and strips wrapping technique, seven beams bonded in full and spiral configuration, seven timber specimens wrapped in flexural strengthening technique with single and multiple layers, and two samples strengthened by steel plates. The results show that jute fibers strengthening are improved the ultimate loads of timber beams by between (30%-101%) compared with the control beams for different types of strengthening and by about (80%, 85%) using steel plates strengthening. On the other hand, the mid-span deflection are decreased by between (28%-45%) at the same load. Furthermore, it is found that the highest ultimate load deflection is when the beam wrapped in full strengthening technique. The ductility, stiffness, toughness at yield load and toughness at ultimate load are increased by between (21%-51%), (10%- 73%), (45%-373%), and (57%-401%), respectively. The jute fibers strengthening have high elasticity performance and prove that the jute fibers materials have a large potential to act as a structural strengthening material.