Masonry Magazine June 1999 Page. 19
The artificial limitation of an h/t of 25 meant that 8-inch CMU walls could only go up 16 feet 8 inches. Continually, it would be requested that walls for supermarkets and other stores go up 18 feet and we always had to work out some technique of getting in the additional 1 foot 4 inches. This was an artificial barrier and a limitation that was not realistic of the capabilities of the system.
A program was initiated to determine how tall masonry walls could go and still be safe subjected to lateral loads. It was made up of engineers from the Structural Engineers Association of Southern California, the American Concrete Institute, Southern California Chapter and the Masonry Institute of America. These engineers set forth an objective to test tall walls that were far thinner than permitted by code.
Table 1 shows the range of walls that were tested. As part of this program, they also tested tilt-up walls in order to confirm what had been used for tilt-up design. However, it was truly a breakthrough to challenge the h/t of 25 for masonry walls and to provide new parameters for masonry design and performance.
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Table 1, Slender Masonry Walls Tested
Wall Type Thickness For f and No. psi Verticle Lat. Load Deftl. at Max. Lat. at Max. Lat.Load Lin hit Ratio Load plf at fpsf Yield in. Defl., in. Defl., psf
1 9.63 2460 30 320 94 5.5 17.1 100+
2 9.63 2460 30 860 82 5.5 8.0 88
3 9.63 2460 30 860 73 6.3 19.0 100
4 7.63 2595 38 860 75 6.5 11.2 92
5 7.63 2595 38 860 75 7.5 10.3 82
6 7.63 2595 38 320 71 5.8 14.4 118
7 5.63 3185 51.2 320 46 9.0 17.7 62
8 5.63 3185 51.2 320 38 15.9 40
9 5.63 3185 51.2 320 46 9.8 11.0 50
10 9.6 3060 30.3 320 94 15.6 150
11 9.6 3060 30.3 320 89 9.3 16.8 162
12 9.6 3060 30.3 320 74 9.0 14.6 90
13 7.50 3440 38.4 320 40 12.0 19.6 60
14 7.50 3440 38.4 320 54 14.0 15.9 68
15 7.50 3440 38.4 320 66 10.5 14.8 79
16 5.50 6243 52.4 320 57 8.0 19.3 87
17 5.50 6243 52.4 320 48 8.2 18.2 86
18 5.50 6243 52.4 320 55 7.9 11.1 61
CMU31 7.63 2960 38 860 55 16.8" 17.5" 129
HBr.32 3.5" 6000 57 225 47 10.0" 17.0 56
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