Currently, much research is focused on the corrosion of reinforcement in concrete members. However, none addresses the problems associated with the residual strength of reinforced concrete beams exhibiting both main and shear reinforcement corrosion simultaneously. The aim of this research, therefore, was to determine the residual strength of corroded reinforced concrete beams where various degrees of reinforcement corrosion is present in both the main and shear reinforcement. This may provide a better understanding of the performance of deteriorated reinforced concrete beams in service. One of the main causes of concrete deterioration is corrosion of the steel reinforcement and thus a reduction of the residual service life. In general, corrosion of reinforcement is believed to affect the structural performance of concrete elements in two ways. Firstly, by reducing the rebar cross sectional area, and secondly, by loss of bond strength between the concrete and steel reinforcement and resulting growth of cracks due to the formation of corrosion products at concrete/reinforcement interface. The experimental programme was carried out to provide information on the loss of strength resulting from corrosion to the main and shear reinforcement. Corrosion was induced by means of external power supplies. The test programme was divided into three series. Series I was devised to determine the residual flexural strength of reinforced concrete beams where different diameters of main (high yield) reinforcement were subjected to varying degrees of accelerated corrosion (shear strength was provided by mild steel shear reinforcement which remained unaffected by corrosion). Series II was devised to determine the residual shear strength of reinforced concrete beams where the shear (mild steel) reinforcement was subjected to varying degrees of accelerated corrosion (flexural strength was provided by high yield steel which was protected from corrosion). Finally, Series III was devised to determine the residual strength of reinforced concrete beams where both the main (high yield) and shear (mild steel) reinforcement were simultaneously corroded and the effect of this on the performance of the beam was determined. In total, 116 beams were subjected to accelerated corrosion using an impressed current imposed on the reinforcement. Each beam was loaded to failure to determine the strength loss. Four degrees of corrosion were targeted, ranging from 0% (control) to 15%, in increments of 5%.The results of the laboratory tests determined the significance of both main and shear reinforcement corrosion on the performance of deteriorated reinforced concrete beams. In addition, simplified analytical equations were developed which may assist the engineer in assessing the residual strength of corroded reinforced concrete beams.

The investigation reported in this thesis is concerned with the general subject of the shear resistance of reinforced concrete beams and the findings are applicable to rectangular, T- and I-sections. To assist the theoretical analysis, tests of 75 normal sized beams, in which the parameters affecting shear varied systematically, were carried out. Concentrating on the types of members where lack of sufficient experimental data existed, all but 10 of the beams contained shear reinforcement and 45 had compression flanges. Virtually all the beams, having high strength longitudinal reinforcement with good bond quality, failed in shear in one of the following modes 1) Diagonal Tension 2) Shearing (Shearing of concrete above a shear crack) 3) Shear Compression 4) Web Crushing The theoretical analysis is to a large extent based on observations of the behaviour of these beams during the tests and at failure. As a result equations are presented representing each mode of failure. If the strengths corresponding to modes 2, 3, and 4 are greater than the diagonal tension load, the final solution is given by the mode of failure equation predicting the least strength; in other cases failure is by diagonal tension. In this manner not only is an adequate numerical prediction of the failure load obtained, but a comparison of the results pertaining to the various modes provides a good indication of the actual typo of failure that is likely to take place. Intrinsic to this approach is a rational solution of the problem of compression reinforcement and its influence or lack of influence on the ultimate shear strength of rectangular beams. The increased strength of T-beams over that of rectangles composed of their webs is also adequately reflected in the proposed theory. To establish the equation for the shearing mode of failure a new adaption of a Coulomb type "plastic shear" failure criterion for concrete is presented. Since collapse loads are not the only design criteria, in addition to the equations for the four modes of failure mentioned, formulae are also developed, substantiated by test results, to cover two other possible criteria 1) Shearing off of flanges in T-beams 2) Shear crack widths The various equations put forward in this thesis show adequate correlation with test results, giving on average a 10% safety margin at a coefficient of variation of loss than 0.10.

Rational decisions about cost-effecctive bridge designs, optimum inspection strategies and repair are hampered by the absence of comprehensive data on the mechanical performance of deteriorated concrete elements. One of the most important causes of concrete deterioration is corrosion of the steel reinforcement. In general corrosion of reinforcement is believed to affect the structural performance of concrete elements in two ways. First, by increasing the stress concentration on the rebar cross section, due to corrosion-induced reduction in the rebar cross-sectional area, which may lead to premature failure if the stresses in the rebar exceeds its yield strength. Second, by weakening the transmission of stresses in the composite resulting from the loss of bond strength between concrete and the steel reinforcement and the growth of cracks due to the formation of corrosion products at concrete/reinforcement interface. As part of a 'Brite Euram' Project, sponsored by the E.E.C., the author has developed procedures for assessing the influence of reinforcement corrosion on the structural performance of reinforced concrete flexural members. The experimental work was carried out on reinforced concrete beams which were subjected to accelerated reinforcement corrosion and then tested in flexure. Corrosion was induced in reinforcement by means of two external power supplies. The results obtained from the experiments show that reinforcement corrosion reduced the stiffness and the load carrying capacity of concrete beams significantly. Structural analysis and reliability analysis techniques were applied to the results of the study, and simple models for predicting the flexural load capacity of corroded beams were produced. The effect of reinforcement corrosion on the bond strength at the steel/concrete interface was also investigated. The results of the study provide evidence to indicate a trend of increased bond strength associated with small degrees of corrosion in reinforcement (≤0.4% reduction in rebar diameter).