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.