double-power 指数算法徐变模型.pdfVIP

CEMENT and CONCRETE RESEARCH. Vol. 14, pp. 793-806, 1984. Printed in the USA. 0008-8846/84 $3.00+00. Copyright (c) 1984 Pergamon Press, Ltd. DOUBLE-POWER LOGARITHMIC LAW FOR CONCRETE CREEP Zden~k P. Ba~ant I and Jenn-Chuan Chern 2 Center for Concrete and Geomaterials The Technological Institute, Northwestern University Evanston, Illinois 60201, U.S.A. (Communicated by F.H. Wittmann) (Received Feb. 17, 1984) ABSTRACT An improvement of the double-power law for creep at constant temperature and moisture content is proposed. Comparisons with available test data indicate that the final slopes of long-term creep curves, as indicated by the double-power law, are pre- dominantly on the high side. This is remedied by introducing a transition to a straight line in the logarithmic scale of load duration. The strain at the transition as well as the slope of the straight line are the same for all ages at loading. The strain and the slope at the transition point are continuous, while the curvature is discontinuous. ~e new law is also found to significantly limit the occurrence of divergence of the creep curves and of negative values at the ends of the relaxation curves calculated by the superposition principle. Extensive statistical comparisons with test data from the literature justify the proposed law. Introduction Although the double-power law [2,3] provides a relatively good descrip- tion of the existing test data an