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Title: Shear strength of reinforced concrete beams
Author: Placas, Alexandre
ISNI:       0000 0001 3492 3397
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1969
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available