Strut-and-Tie Capacity of Partially-Grouted CMU Shear Walls

Current design provisions for CMU shear walls are largely derived by empirically fitting equations to experimental data. The disadvantage of this approach is that, generally, existing experimental data is biased towards relatively small, fully-grouted, walls without openings. CMU walls used in practice, however, are frequently partially grouted and contain openings. Thus, there is a need for a theoretical approach to determine the capacity of CMU shear walls. Strut-and-tie modeling could potentially address this need. The purpose of this paper is to assess a strut-and-tie modeling approach for the design of squat partially-grouted CMU shear walls. To accomplish this goal, the author compile a database of 25 fully-grouted and 11 partially-grouted experimentally-tested CMU walls. Strength predictions for these walls are determined in accordance with the current masonry design code (MSJC 2013) and a strut-and-tie approach similar to what is in the concrete design code (ACI 318); and a comparison is made between predicted and experimental capacities. Based on the results of this analysis and considering the limited number of experimental results, the author found that the strut-and-tie modeling approach performed statistically similar to the MSJC provisions for fully-grouted walls and significantly better than the MSJC provisions for partially-grouted walls. The implication of these results are that, in general a STM procedure could potentially be used to adequately predict the capacity of a squat CMU shear wall.