Flexural strength and deformation of reinforced concrete beams strengthened with steel plates were studied in this paper. For bonding the steel plate to the beam a technique of welding steel plate to the stirrups was followed. Fifteen beams were cast and tested; nine beams were strengthened by steel plates preloaded with a fraction of the ultimate load of the control beams (three beams) and then tested to failure. Another three beams were cast and tested to failure also, strengthened and then retested to failure. The test results indicated that the process of welding is successful and can furnish the state of composite action. After strengthening, the ultimate load was increased by 1 to 17 % and by 70 to 94 % for beams strengthened with 1 mm thick and 3 mm thick steel plates, respectively. The effect of cracking due to preloading on the flexural behavior of strengthened beams was found to be not significant.

Experimental investigations of the behavior of reinforced concrete three-span continuous beams with 1200 mm length for each span, with cross-section 120 mm width and 180 mm depth strengthened by CFRP in flexure case of beams have been presented. The experimental program consisted of nine RC beams, which were strengthened at some locations with CFRP laminates and carefully designed to fail in flexure. The results show that the use of external CFRP laminate connected to the beams could enhance the ultimate flexural load capacity up to 102.88%.

This paper investigates experimentally the complete uniaxial tensile stress-strain relationships of Ultra high performance concrete (UHPC) and equations for expressing such relationships are obtained. The effects of two variable parameters on the uniaxial tensile behavior were carefully studied which are the silica fume content SF (0%, 10%, 15%, 20%, 25%, and 30%) as a partial replacement by weight of cement, steel fibers volume fraction V f (0%, 1%, 2% and 3%). The experimental results showed that the two variables of the present investigation had no significant effect on the shape of the ascending part of the stress-strain curve, while the descending part of the curve was found to be considerably affected by the volume fraction V f of the steel fibers used. Increasing fibers volume fraction V f from 0% to 3% not only increase the area under the uniaxial tensile stress-strain curve, but also increase both the maximum uniaxial tensile strength by 238.5% and its corresponding strain by about 4044%. Two nonlinear equations are suggested in this research to model the ascending and descending part of the uniaxial tensile stress-strain relationship which are found suitable to represent the uniaxial tensile behavior of the UHPC mixes.

In this research, nine orthotropically reinforced concrete (RC) rectangular slabs having various boundary restraints at the edges are tested under uniformly distributed load. The main aim of these tests is to show that when some or all edges of a slab are restrained against rotation and horizontal translation the ultimate load carrying capacity of the slab will be enhanced greatly above that suggested by the simple Johansen , s yield line theory (1) . For this purpose, a specially designed rig is constructed and used for providing slabs with various boundary restraints along their edges.The results of tests, which are presented in the form of load-deflection curves plotted non-dimensionally, show that for restrained slabs the enhancement in load above Johansen , s load ranges between 50% and 100% depending on the number and positions of the slab restrained edges. These results are also used to examine the accuracy of a recently submitted elastic-plastic theoretical model (2) .

A new generation of Ultra High Performance Concrete (UHPC) named Reactive Powder Concrete (RPC) was developed in the last decades, which offers, superior strength, durability and ductility. One of the main differences between other concretes and RPC is that the latter requires mechanical models capable of taking tensile behavior into account for structural application to enable the material to be fully exploited. The complete stress-strain relationship under direct tensile test and uniaxial compression of different RPC mixes was experimentally investigated. Nonlinear equations are suggested to model the complete tensile and compressive stress-strain relationship for all the RPC mixes studied. In this research an analytical study is devoted to establish a simple equation for predicting the nominal bending moment capacity M n of plain and singly reinforced rectangular RPC beam sections. The equation derived showed good agreement with all the flexural test results performed in previous researches and some other investigations on reactive powder concrete beams.