The Earthquake Engineering Online Archive

Mechanical behavior of lightweight concrete confined by different types of lateral reinforcement

Manrique, Miguel A.; Bertero, Vitelmo V.; Popov, Egor P.

UCB/EERC-79/05, Earthquake Engineering Research Center, University of California, Berkeley, 1979-05, 129 pages (515/M225/1979)

Results are reported of an experimental study carried out at the Univ. of California at Berkeley as part of an ongoing research program to evaluate the behavior of lightweight concrete. The study focuses on the behavior of confined lightweight concrete when subjected to axial, monotonic loading. The effect on confined concrete of the following parameters was considered: (a) concrete cover, (b) longitudinal reinforcement, and (c) lateral reinforcement arrangement. Thirty confined and unconfined specimens were tested. The effect of the mentioned parameters were evaluated and the experimental results compared with the results of a similar investigation carried out on normal weight concrete. Current code-implied values for confinement effectiveness coefficients and the experimentally obtained values are compared and the consequences of the differences obtained are discussed. An analytical stress-strain relationship for longitudinally reinforced confined lightweight concrete is presented which considers the effect of increase in strength and strain at maximum stress resulting from confinement as well as the effect of the different types of lateral reinforcement and the effect of the longitudinal reinforcement on the descending branch of the stress-strain relationship. Practical design implications of the study are presented. Discussed are the effects that the avoidance of buckling of the longitudinal reinforcement by means of close spacing of the lateral reinforcement would have on the ductility of the concrete and on the axial load-moment interaction diagrams obtained from current ACI assumptions of the material properties of both concrete and steel.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-79-05.pdf (42 MB)