Load-Deformation Relationship of High-Strength Reinforced Concrete Beams

Synopsis: Force-deformation relationship of high-strength reinforced concrete beam members observed in the laboratory test was idealized by a trilinear relation for use in a nonlinear earthquake response analysis. Methods to evaluate the relationship were examined and the reliability of the methods were discussed with respect to the observed relations. Calculated initial stiffness is shown to significantly underestimate the observed value; a large coefficient of variation was attributed to accidental and shrinkage cracking in the specimen prior to the test. A similar large coefficient of variation was observed in the evaluation of cracking moment. Yield and ultimate moments could be favorably estimated by the theory. An empirical formula was proposed to evaluate yield deformation. An importance of controlling the elastic modulus of concrete in construction is emphasized if a structure is expected to behave as designed during an earthquake.