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

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2-8 Earthquake Protection Page 8 FM Global Property Loss Prevention Data Sheets 9. Locate a lateral brace not more than 6 ft (1.8 m) from horizontal changes in direction. 10. After giving credit to any lateral sway bracing installed or allowed to be omitted per items 1 to 9 above, provide lateral sway bracing on straight runs of pipe spaced at a maximum of 40 ft (12.2 m). B. Provide longitudinal sway bracing on all branch lines and portions of branch lines (including portions adjacent to changes in direction) that are 2- 1 ⁄ 2 in (65 mm) and larger and greater than 40 ft (12.2 m) in length in accordance with the following guidelines. 1. A four-way brace on a vertical pipe (e.g., at the bottom of a drop) may be counted as the initial longitudinal brace for the attached horizontal branch line of the same or smaller diameter when the brace is located within 2 ft (0.6 m) of the horizontal pipe. Recognize that the design load for this four-way brace should include the tributary load from both the vertical and the horizontal pipe. 2. A lateral brace within 2 ft (0.6 m) of the end of a branch line connection to another branch line that is perpendicular and of the same or lesser diameter may be used to also act as a longitudinal brace for the perpendicular branch line. Recognize that the sway brace design load includes the tributary lateral and longitudinal loads for the braced branch lines. 3. Locate the first longitudinal sway bracing location closest to the crossmain between 20 ft and 80 ft (6.1 m and 24.4 m), including all vertical and horizontal branch line section lengths, from the branch line connection to the crossmain. 4. For dead-end branch lines, locate the last longitudinal brace not more than 40 ft (12.2 m) from the end. Consider seismic separation assemblies per Section 2.2.1.4.8 as the end of the piping on both sides of the assembly. 5. Locate a longitudinal brace not more than 40 ft (12.2 m) from horizontal changes in direction. 6. After giving credit to any longitudinal sway bracing installed per items 1 through 5 above, provide longitudinal sway bracing on straight runs of pipe spaced at a maximum of 80 ft (24.4 m). 2.2.1.2 Horizontal Seismic Loads for Sway Bracing Design 2.2.1.2.1 Determine the horizontal design load (H) for each sway bracing location by multiplying the weight of the water-filled piping located within the zone of influence (W p) for that sway bracing location times the horizontal acceleration (“G” factor) expected from an earthquake. For simplicity of calculations, the same W p may be used for the design of several braces as long as it is based on the weight of water-filled pipe in the controlling zone of influence. Table 1 shows weights for water-filled pipe to be used with the appropriate “G” factor to calculate design loads. 2.2.1.2.2 Use a minimum “G” factor of 0.75 in FM Global 50-year earthquake zones, 0.5 in FM Global 100-year earthquake zones, and 0.4 in FM Global 250- and 500-year earthquake zones. These “G” factors are based on the Allowable Stress Design analysis method. Use a higher “G” factor if required by local authorities per the building code for the location involved. ©2010 Factory Mutual Insurance Company. All rights reserved.
Earthquake Protection 2-8 FM Global Property Loss Prevention Data Sheets Page 9 Pipe Nominal Diameter in. (mm) Table 1. Weight of Water-Filled Pipe Weight, lb/ft (N/m) Schedule 40 1 (25) 2.1 (31) 1-1 ⁄ 4 (32) 2.9 (43) 1-1 ⁄ 2 (40) 3.6 (53) 2 (50) 5.1 (75) 2-1 ⁄ 2 (65) 7.9 (116) 3 (80) 10.8 (159) 3-1 ⁄ 2 (90) 13.5 (198) 4 (100) 16.4 (241) 5 (125) 23.5 (345) 6 (150) 31.7 (465) 8* (200) 47.7 (700) Schedule 10 and Lightwall 1 (25) 1.8 (26) 1-1 ⁄ 4 (32) 2.5 (37) 1-1 ⁄ 2 (40) 3.0 (44) 2 (50) 4.2 (62) 2-1 ⁄ 2 (65) 5.9 (87) 3 (80) 7.9 (116) 3-1 ⁄ 2 (90) 9.8 (144) 4 (100) 11.8 (173) 5 (125) 17.3 (254) 6 (150) 23.0 (338) 8 (200) 40.1 (589) * Schedule 30 2.2.1.2.3 Determine the weight (Wp) to be used for each sway brace design (or each controlling sway brace design) by including the water-filled weight of all piping within the zone of influence, defined below. A. Four-way sway bracing at risers, vertical feedmains and crossmains, and drops: 1. Where the four-way sway brace restrains only the vertical pipe (e.g., an intermediate riser brace where there is no attached feedmain or crossmain) the zone of influence includes the length of the vertical pipe above and below the sway brace that is tributary to that sway brace. Use the resulting weight of pipe to determine the load to be applied in each orthogonal horizontal direction. 2. Where the four-way sway brace for the vertical pipe also serves as a lateral and longitudinal sway brace for an attached horizontal pipe (e.g., feedmain or crossmain), the four-way sway brace zone of influence is determined as follows. a. In the lateral direction of the horizontal pipe, add the tributary length of vertical pipe above and below the sway brace, plus the tributary lengths of feedmain, crossmain, and branch line piping, as described in Section 2.2.1.2.3(B), located between the four-way sway brace and the first lateral sway brace on the horizontal pipe. b. In the longitudinal direction of the horizontal pipe, add the tributary length of vertical pipe above and below the sway brace, plus the tributary lengths of feedmain, crossmain, and branch line piping, as described in Section 2.2.1.2.3(C), located between the four-way sway brace and the first longitudinal sway brace on the horizontal pipe. 3. The weight of the water-filled pipe for manifolded bracing design includes the total load for the two risers being braced. B. Lateral two-way sway bracing: 1. For feedmains, the zone of influence includes the length of the feedmain to the left and right of the sway brace that is tributary to that brace. ©2010 Factory Mutual Insurance Company. All rights reserved.
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DS 2-8 Earthquake Protection for Water-Based Fire ... - FM Global

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