The influence of confining the compression zone in the design of structural concrete beams

Abstract

The programme of research described in this thesis has investigated the effect of confinement of the compression regions on the behaviour of structural concrete beams up to failure under the action of static loadings. A flexure-shear interaction design model and a corresponding approach to detailing to prevent diagonal failures in beams have been developed based on the actual physical behaviour of beams. This has been achieved by confining only the compression regions in the beam structure with closed stirrups. The increase in concrete strength resulting from the presence of the confining stirrups was aimed at offsetting the reduction in the flexural capacity of beams due to the presence of shear forces. A method for the evaluation of the flexural capacity of beams in which confinement is present has also been proposed. The approach was extended to the design of over-reinforced beams to enable them to behave in a ductile manner. A test programme comprising a total of fifty three simply supported beams was used for the development (twelve beams) and for the verification (forty one beams) of the proposed design models. The results obtained confirmed both the applicability and the effectiveness of all of the design concepts and detailing approaches which have been put forward in this research programme. It is believed that the concepts which have been put forward could form a basis for the development of a rational unified approach to the design of structural concrete members.