【正文】 Better Practices 169。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 impact of sprinklers against rigid ceilings resulted in a several highprofile incidents in which a number of sprinklers opened and water damage resulted. In 1999 the NFPA sprinkler project was reanized. Responsibilities for the earthquake protection rules were given to a new NFPA Technical Committee on Hanging and Bracing of WaterBased Fire Protection Systems, one of four separate technical mittees coordinated through a Technical Correlating Committee responsible for NFPA 13. This allowed the direct input of more earthquake engineering expertise into the standard development process. Major changes in building code requirements for earthquake protection have taken place in the past twenty years, mainly due to the National Earthquake Hazards Reduction Program (NEHRP) provisions developed with funding from the Federal Emergency Management NEHRP provisions initially found their way into the codes through direct adoption, and more recently through reference to the American Society of Civil Engineer’s standard ASCE/SEI 7. As a result, the goal of the mittee that prepares NFPA 13 has evolved during the years. From the original goal of independently providing a means of protecting sprinkler systems against earthquake forces, the mittee in recent years has been trying to keep pace with a moving target as successive editions of ASCE/SEI 7 address protection of architectural and mechanical systems. There is a difficult transition period taking place right now involving the seismic provisions of NFPA 13 and the 2020 edition of the International Building Code174。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 in. or larger 1994 For piping 2189。 “Flexible listed pipe coupling” defined as “a listed coupling or fitting that allows axial displacement, rotation, and at least 1 degree of angular movement of the pipe without inducing harm on the pipe” (minimum degrees for 8in. and larger) 2020 Flexible couplings and clearance identified as addressing displacement due to story drift 4. Flexible Couplings for Risers in MultiStory Buildings 1983 At ceiling of each intermediate floor 1994 Within 12 in. above and below the floor in multistory buildings such that the flexible coupling below the floor is below the main supplying that floor 2020 Structures Congress: New Horizons and Better Practices 169。 see 1999 Within 12 in. above and within 24 in. below the floor in multistory buildings。 Swing joints assembled with flexible fittings on drops to racks over 3 in. 1987 Flexible couplings at the top of drops to hose lines (regardless of size)。 Flexible coupling at the top of drops exceeding 15 ft. to sprinklers or portions of systems (regardless of size) 1991 Flexible coupling within 24 in. of the ceiling at top of drops to hose lines, rack sprinklers and mezzanines (regardless of size)。 Seismic separation assembly needed for seismic separation joints 1999 – Within 24 in. of building expansion joints 7. Seismic Separation Assemblies 2020 Structures Congress: New Horizons and Better Practices 169。 see Swing joints assembled with flexible fittings required where piping crosses seismic joints。 Added applicability only “above ground level” 2020 – Expanded to “flexible fittings or flexible hose” and specified minimum capability of allowing movement to acmodate closing of the separation, opening of separation to twice normal size, and movement relative to the separation in the other two dimensions in an amount equal to the separation distance 8. Clearances 1983 Clearance through walls, floors, platforms and foundations 1 in. all sides through 3189。 Exception added to permit pipe sleeves of nominal diameter 2 in. larger through 3189。 Another exception added for pipe passing through gypsum board or equally frangible construction not required to have a fireresistance rating 1985 Flexible joints permitted to substitute for clearance for pipe entering a basement wall with ground water conditions 1987 Flexible couplings or swing joints within one foot of both sides permitted to substitute for clearance in any wall 1994 Flexible coupling within 1 ft. of each side accepted as alternative for walls, platforms and foundations 2020 Clearance dimensions to be considered nominal。 Clearance not required for nonmetallic pipe having flexibility equal to flexible couplings within 1 ft. of both sides. 9. Sway Bracing General 1983 Piping to be tied to the structure for minimum relative movement, but allowing for expansion, and differential movement within and between structures。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 Each run of pipe between a change in direction to be provided with both lateral and longitudinal brac