Title: Assessing Creep and Shrinkage Losses in Post-Tensioned Concrete Masonry

Author(s): Peter Laursen, Gavin Wight, and Jason Ingham

Publication: Materials Journal

Volume: 103

Issue: 6

Appears on pages(s): 427-435

Keywords: concrete masonry; creep; post-tensioned; prestress; shrinkage

DOI: 10.14359/18220

Date: 11/1/2006

Abstract:
Prestress losses due to creep, shrinkage, and steel relaxation lead to a reduction in structural efficiency in post-tensioned concrete masonry walls. This paper investigates the magnitude of losses that can be expected from medium-weight concrete masonry units. The findings from two series of creep and shrinkage experiments are presented and compared with test data from other researchers and with values stipulated in international standards. A creep coefficient of 3.0 is found, a value that is in agreement with the Australian, British, and Canadian standards. Shrinkage strains of 1000 and 600 microstrain for grouted and ungrouted walls, respectively, were obtained under laboratory conditions. Prestress force losses due to creep and shrinkage are shown to be significant and consistent with the recommendations made in the U.S. code.