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NFPA13의 내진 설계

작성자 : 운영자
작성일 : 16-10-05 07:55 조회수 : 3,155

NFPA13의 내진 설계
Seismic design of fire suppression piping systems
 
국내화재안전기준의 소방배관에 대한 내진 기준은 NFPA 13의  "9.3 Protection of Piping Against Damage Where Subject to Earthquakes. "의 내용을 근거로 작성된 것입니다. 
따라서, 본 내용을 보시면 소방내진에 대한 이해를 도와 줄 것으로 사료됩니다.

본 내용은 2015. 1. 23일 Joseph H. Talbert 소방기술사가 발표한 내용이니 참고바랍니다.
 
The subject of seismic design of fire suppression systems has been incorporated in NFPA Standard 13: Standard for the Installation of Sprinkler Systems since 1947. The design guidance contained in NFPA 13 for seismic bracing of sprinkler piping has also been adopted by NFPA 14: Standard for the Installation of Standpipe and Hose; NFPA 15: Standard for the Installation of Water Spray Fixed Fire Protection Systems; NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection; and NFPA 2001: Standard for the Installation of Clean Agent Fire Suppression Systems. 
 ☞ (국내화재안전 기준 제2조 적용범위 참조)
 
The design guidance has evolved since the earlier versions of the standard. The most notable updates were made based on lessons learned in the San Fernando, Calif., earthquake in 1971; the Loma Prieta, Calif., earthquake in 1989, and the Northridge, Calif., earthquake in 1994. A study performed by the Pacific Fire Rating Bureau (PFRB) of 973 sprinklered buildings involved in the San Fernando earthquake led the PFRB to conclude that “if a sprinklered building fared well, so did the sprinkler system.”
 
The knowledge gained from previous seismic events has led to continuous modifications to the NFPA 13 design guidance for sprinkler systems. These modifications have been aimed at avoiding significant damage to sprinkler systems and permitting sprinkler systems to remain functional following an earthquake. The seismic design provisions contained in the 2010 edition of NFPA 13 have been coordinated with the provisions of the National Earthquake Hazard Reduction Program (NEHRP) and SEI/ASCE 7, Minimum Design Loads for Buildings and Other Structures.
 
NFPA 13 Chapter 9.3, Protection of Piping Against Damage Where Subject to Earthquakes, sets out the requirements for seismic bracing and restraints of sprinkler systems. It is important to note that although this chapter gives guidance for how a system should be designed, it does not specify the geographic locations where seismic design must be incorporated into a sprinkler system design. This is done by other documents, typically local building codes.
 
In the past, only sprinkler systems located in areas that were perceived to be subject to high frequencies of damaging earthquakes (typically in California) were designed to resist damage due to seismic events. However, the International Building Code (IBC) has now published maps that give guidance regarding the maximum predicted peak ground acceleration due to earthquakes. In addition, the U.S. Geological Survey (USGS) publishes maps of the United States that show the areas with a 2% probability of exceedance of the peak ground acceleration in a 50-year period (see Figure 1). Such a map indicates that there are areas in the central and eastern United States in which the peak ground acceleration expected is similar to areas in California, which are considered to be high earthquake hazard areas.
 
Design guidance
 
NFPA 13-2013 edition sets forth design guidance. Section 9.3.1.2 allows the use of alternative methods of providing earthquake protection of sprinkler systems based on a seismic analysis certified by a registered professional engineer such that system performance will be at least equal to that of the building structure under expected seismic forces.
 
Appendix A Section A.9.3.1 states the goal of the design guidance in NFPA 13: “Sprinkler systems are protected against earthquake damage by means of the following: (1) Stresses that would develop in the piping due to differential building movement are minimized through the use of flexible joints or clearances. (2) Bracing is used to keep the piping fairly rigid when supported from a building component expected to move as a unit, such as a ceiling.”
 
To provide the necessary combination of flexibility and rigidity to protect the piping, NFPA 13 stipulates the following design guidance :
 
• Provideclearancewhere needed.
 
• Installlongitudinal and lateral sway bracingat prescribed intervals on the piping system to provide support against horizontal movement caused by ground movement.

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