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Analysis of Partially Grouted Masonry Shear Walls.


pdf icon Analysis of Partially Grouted Masonry Shear Walls. (2534 K)
Shing, P. B.; Cao, L.

NIST GCR 97-710; 45 p. March 1997.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB97-153987

Keywords:

masonry; walls; mortar joints; reinforcing bars; sensitivity analysis

Abstract:

Six partially grouted reinforced masonry shear walls that were tested at NIST are analyzed in this study. The main aim of the study is to assess the capability of some state-of-the-art finite element models in predicting the behavior of these wall specimens under cyclic in-plane lateral loads. To this end, two types of elements are used to model the behavior of a partially grouted masonry wall to reflect the inhomogeneity and anisotropy introduced by mortar joints. The shear and tensile behavior of a mortar joint is modeled with plasticity-based interface elements, while the fracture behavior of masonry units is modeled with smeared crack elements. The analyses have been carried out in several stages. First, a pretest analysis was conducted on one of the wall specimens. This was followed by an extensive parametric study to identify the sensitivity of numerical results to the modeling parameters. Finally, the finite element models have been fined tuned with data obtained from relevant material tests that were conducted in conjunction with the tests of the wall specimens. The main variables in the wall specimens are the aspect ratio of the walls and the quantity of horizontal reinforcement. It has been shown that the behavior of a partially grouted reinforced masonry wall is very similar to that of a reinforced concrete infilled frame. The grouted masonry provides the frame action while the ungrouted masonry acts like infill panels. The numerical results show that the quantity of the horizontal steel in the bond beam has little influence on the behavior of the wall specimens. The walls with a low aspect ratio tend to exhibit a distinct sliding shear failure through the bed joints at mid-height, while those with a higher aspect ratio have more severe cracking in the vertical joints within the wall panels. The vertical cracks between the grouted and ungrouted cells are reasonably well captured in the analyses. However, except for one wall specimen, the lateral strengths obtained in the analyses are higher than those shown by the experiments. The discrepancies in the numerical and experimental load-displacement curves can be partly caused by the different load histories and partly by the discrepancy in the bond strength between the wall panels and the concrete head beams.