Prestress loss due to creep in post-tensioned clay masonry

Numerical schemes using the finite element technique as well as method of superposition are utilized in this paper to compute total load strains (which include creep strains) in stack-bond and running-bond clay brick laboratory wall specimens, It is shown that the resulting values of strains compare favorably with those calculated using the two-phase composite model and measured experimentally. The magnitude of creep strains in walls after 300 days is 50% more than the instantaneous elastic strains. Accordingly, post-tensioned masonry walls necessitate application of additional prestress, especially during the first two months of their initial prestressing. Creep strains in a masonry pier specimen are calculated by utilizing the commercially available finite element package-ABAQUS. The results indicate that the creep strains in this case are approximately one-half of the instantaneous elastic strains. Nevertheless, they still represent a substantial loss of prestress in post-tensioned masonry piers and must be accounted for in their design.