Abstract
Succeeding to S. Ban's report regarding the rotation of plastic hinge at the loaded position of a beam, the rotation limit of plastic hinge at fixed end of beam is considered. A new analytical method for calculation of limitting rotation is derived. This method is to be applied regardless of the hinge position under the assumptions that the concrete at the compression side and the steel in the tension side reach to the plastic state symultaneously and that the status continue to deform with definite rate untill the concrete collapses. The length of plastic zone is assumed n (depth of neutral axis in plastic state) for concrete and 2 j for reinforcements where j denotes the arm of internal couple. Through these assumptions it is succeeded to present an explicit formula giving the rotation limit of plastic hinges, when the percentage of steel and the ratio yield point stress to the concrete strength are previously known. The calculated rotations were compared with the experimental measurements but close agreement was not found owing to either the remarkable deviations of measurements or the improper choice of plastic zone.
