DS 2-8 Earthquake Protection for Water-Based Fire ... - FM Global

Earthquake Protection 2-8
FM Global Property Loss Prevention Data Sheets Page 53
Fig. 25. Layout and zones of influence for longitudinal and four-way riser sway bracing for System #1.
C.2.1 Gridded System (System No. 1)
Step 1. Layout and orientation of braces. Fig. 24 shows the layout of the two-way lateral braces, and a
four-way brace at the riser. Fig. 25 shows the layout of the two-way longitudinal braces. In both figures, the
dashed lines indicate the zone of influence for piping to be used to calculate horizontal seismic design load
for each bracing location. In this example, the location of lateral and longitudinal sway bracing on the actual
piping grid is fairly straightforward. However, because of the long feedmain, and the changes in direction,
lateral bracing is strategically located within 2 ft (0.6 m) of the changes of direction, and will be used both
as lateral bracing on the pipe to which it is attached, and as longitudinal bracing for the run of piping after the
change in direction. This will be illustrated in Step 2.
Step 2. Calculate design loads. In this example, a horizontal acceleration of 0.5 G will be used for calculation
purposes. Assume sprinkler piping is Schedule 10. Using weights per length of water-filled pipe from Table
1, horizontal seismic design loads for each sway bracing location can be determined as shown in Table 17.
Step 3. Select the proper brace type, size, and maximum length. Based on the configuration of the brace
connection to the structure, the angle of the brace from the vertical, and the calculated horizontal design
load, the brace type, size, and maximum length can be selected from Tables 2 to 7.
Step 4. Using the Step 2 design loads, and the brace angle from the vertical, select the appropriate type
and size of fastener for attachment to the building structure.
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