Civil Engineering Reference
In-Depth Information
Therefore before an attempt is made to use current design concepts as the
basis for the description of the behaviour of RC deep beams, it is essential to
investigate the effect of the small transverse stresses on structural concrete
behaviour.
2.3
Effect of transverse stresses
2.3.1
Flexural capacity
Flexural capacity is assessed on the basis of the plane sections theory. The
theory describes analytically the relationship between flexural capacity and
geometric characteristics by considering the equilibrium conditions at
critical cross-sections. Compatibility of deformation is satisfied by the
'plane cross-section remain plane' assumption and the longitudinal concrete
and steel stresses are evaluated by the material stress-strain characteristics.
Transverse stresses are not considered to affect flexural capacity and are
therefore ignored.
It is well known, however, that concrete is weak in tension and strong in
compression. Therefore, its primary purpose in an RC structural member is
to sustain compressive forces, while steel reinforcement is used to sustain
tensile forces with concrete providing protection to it. As concrete is used to
sustain compressive forces, it is essential that its strength and deformational
response under such conditions are known.
The stress-strain characteristics of concrete in compression are considered to
be described adequately by the deformational response of concrete specimens
such as prisms or cylinders under uniaxial compression. Typical stress-strain
Figure 2.1
Typical stress-strain curves obtained from tests on concrete cylinders under uniaxial
compression.
