Sustained and Cyclic Loading of Concrete Beams

A general analytical procedure for predicting the behavior of reinforced concrete beams subjected to variable repeated loading which includes the effect of the strain-hardening of the steel and creep behavior of the concrete is verified with a test program consisting of eight simply supported beams and six two-span continuous beams. The instantaneous moment-curvature relationship is developed using the stress-strain relations obtained from standard axial tests for the steel and concrete to represent the stresses in each of the materials at any point in the cross section. The equations developed to represent the moment-curvature-time relationships are obtained from a flexural theory which represents the stress-strain-time relationship for the concrete by the actual experiment strain values for plain concrete cylinders at various stress and time coordinates. The intermediate stress strains are calculated by interpolating between the given points.