maintained. See Paragraph (4) below for acceptable

sway bracing details.

(c) Flexible piping systems. Piping systems

that are not in accordance with the rigidity

4.

Flexible couplings and expansion

requirements of Paragraph 10-3e(4)(b) (i.e., period

joints. Flexible couplings will be provided at the

less than 0.05 second) will be considered to be

bottoms of risers for pipes larger than 3 inches

flexible (i.e., period greater than 0.05 second).

(89mm) in diameter.

Flexible couplings and

Flexible piping systems will be designed for seismic

expansion joints will be braced laterally unless such

forces with consideration given to both the dynamic

lateral bracing will interfere with the action of the

properties of the piping system and the building or

flexible coupling or expansion joint. When pipes

structure in which it is placed. In lieu of a more

enter buildings, flexible couplings will be provided

detailed analysis, the equivalent static lateral force is

given by Equation 10-1, with *a*P = 2.5. The forces

to allow for relative movement between soil and

building.

will be distributed in proportion to the weight of the

pipes, contents, and attachments. If the weight of

5. Spreaders. Spreaders will be provided

the attachments is greater than 10 percent of the

at appropriate intervals to separate adjacent pipe

weight of the pipe, the attachments will be separately

lines unless the pipe spans and the clear distance

braced, or substantiating calculations will be

between pipes are sufficient to prevent contact

required.

If temperature stresses are appreciable,

between the pipes during an earthquake.

substantiating calculations will be required.

(b) Rigid and rigidly attached pipes will be

1. Separation between pipes. Separation

designed in accordance with Equation 7-1, where *W*P

will be a minimum of four times the calculated

maximum displacement due to *F*P, but not less than

is the weight of the pipes, the contents of the pipes,

and the attachments. The forces will be distributed

4 inches (102mm) clear between parallel pipes,

in proportion to the weight of the pipes, contents,

unless spreaders are provided.

and attachments. A piping system is assumed rigid

if the maximum period of vibration is 0.05 second

2. Clearance. Clearance from walls or

(for pipes that are not rigid, see Paragraph (3)

rigid elements will be a minimum of three times the

calculated displacement due *to F*P, but not less than

below).

Figures 10-5, 10-6, and 10-7, which are

based on water-filled pipes with periods equal to

3 inches (76mm) clear from rigid elements.

0.05 second, are to be used to determine the

allowable span-diameter relationship for structures

3. Alternative method for flexible piping

conforming to Seismic Design Categories C, D, E,

systems. If the provisions in the above paragraphs

and F for standard (40S) pipe; extra strong (80S)

appear to be too severe for an economical design,

pipe; types K, L, and M copper tubing; and 85 red

alternative methods based on rational and substantial

brass or SPS copper pipe.

analysis may be applied to flexible piping systems.

10 20

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