Peter Laursen

Structural testing of enhanced post-tensioned concrete masonry walls

The in-plane response of post-tensioned concrete masonry walls with unbonded tendons, incorporating strengthened masonry and enhanced energy dissipation, is examined by means of structural testing. An introduction to the testing programme is followed by a presentation of the results from structural testing of five fully grouted walls. Discussion of the results is concerned with wall structural response in terms of flexural strength, displacement capacity, tendon stress and masonry vertical strain, and makes comparison with testing of unconfined (ordinary) post-tensioned concrete masonry walls.

Assessing Creep and Shrinkage Losses in Post-Tensioned Concrete Masonry

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.

Analysis and Seismic Performance Evaluation of Flexure-Dominated Interlocking Compressed Earth Block Walls:

This paper presents development and validation of three analytical models for flexure-dominated Interlocking Compressed Earth Block (ICEB) walls, which are based on classic mechanics of materials, inelastic truss elements, and phenomenological hysteretic model, respectively. Based on the testing results from a prior experimental investigation, it is shown that the first two models provide reasonable estimates for the lateral load resistance of flexure-dominated ICEB walls and the third model captures the inelastic behavior of flexure-dominated ICEB walls under cyclic loading. Using the third model, incremental dynamic analyses were conducted and performances of two demonstration single-story buildings consisting of flexure-dominated ICEB walls were evaluated for three construction sites with different levels of seismicity. Computer simulation results show that both demonstration buildings are able to avoid earthquake-induced collapse. It is also found that the current design and construction of flexure-dominated ICEB walls may be overly conservative for a site with relatively low seismicity.