【正文】 ion of Sprinkler Systems, National Fire Protection Association, 1951. 3. Fleming, R.., “Bracing for Earthquakes”, Sprinkler Quarterly, National Fire Sprinkler Association, Spring 1984. 4. Fleming, R.., “Lessons from the Loma Prieta Earthquake”, Sprinkler Quarterly, National Fire Sprinkler Association, Summer 1990. 5. Fleming, R.., “Sprinkler System Performance in the Northridge Earthquake,” Sprinkler Quarterly, National Fire Sprinkler Association, Spring 1994. 6. Fleming, R., Analysis of Fire Sprinkler Systems Performance in the Northridge Earthquake, NIST GCR 98736, January 1998. 2020 Structures Congress: New Horizons and Better Practices 169。 Clarification added that the structural ponents must be capable of carrying the added applied loads。 see 1996 Connections to wood to be made using through bolts with washers on each end。in and larger piping。 Where pipe, angles, flats or rods used as braces, exception to require listing of brace fittings and connections only。 For branch lines, restraint required within 2 ft of hangers at maximum 30ft intervals where upward or lateral movement of sprinklers would result in impact against building structure, equipment or finish materials 2020 Clarification of intent to prevent damage to sprinklers, not to prevent impact 17. Sway Bracing Brace Components 1983 Sway bracing to be designed to withstand a force in tension or pression 1985 For individual braces, the slenderness ratio l/r limited to 200 2020 Structures Congress: New Horizons and Better Practices 169。 Exception requires restraint of end sprinkler on line against excessive movement by wraparound Uhook or other approved means 1989 Second exception added to require lateral bracing for branch lines 2189。 Allowance for maximum spacing over 40 ft eliminated。 see Brace for feed and cross mains。 Maximum vertical distance between 4way braces limited to 25 ft 2020 Braces and restraints identified as possible obstructions to sprinkler discharge 10. Sway Bracing Loads 1983 Sway bracing to withstand a force in tension or pression equivalent to not less than half the weight of waterfilled piping 1989 Assigned load table added. Alternative permitted for zone of influence method: For lateral braces all branch lines and mains within zone For longitudinal braces all mains within zone 1994 Multipliers permitted for horizontal force factor Fp = Wp where use of other force factors required or permitted by AHJ 1996 “When the horizontal force factor used exceeds Wp and the brace angle is less than 45o from vertical or when the horizontal force factor used exceeds Wp and the brace angle is less than 60o from vertical, the braces shall be arranged to resist the vertical reaction produced by the horizontal load” 1999 Assigned load table deleted 2020 Factor of Wp to be used to account for the added weight of fittings, valves and other devices 2020 – Table included of “Seismic Coefficients” to allow determination of horizontal seismic loads based on mapped values of short period response parameter SS。 see – Table for maximum brace loads moved to body of standard 1994 System piping to be supported to resist both lateral and longitudinal horizontal loads 1996 System piping to be supported to resist both lateral and longitudinal horizontal loads and vertical loads。 Clearance not required for horizontal piping passing perpendicularly through successive studs or joists that form a wall/ceiling assembly。in pipe, 2 in. all sides 4inch and larger。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 Swing joints with flexible fittings on drops to racks (regardless of size) 1989 Flexible coupling at the top of drops to hose lines, rack sprinklers and mezzanines (regardless of size)。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 see conclusion was that systems installed in accordance with NFPA 13 withstood the earthquake, while those not so designed failed. Over the past two decades there have been a numerous refinements in the language of NFPA 13 that reflect the lessons learned in earthquakes as well as the influence of the NEHRP provisions. These can be evaluated by looking at how the various sections of NFPA 13 have evolved in twenty key areas: 1. Applicability of NFPA 13 Earthquake Protection Provisions 1983 Where subject to earthquakes 1996 When sprinkler systems…are to be protected against damage from earthquakes 1999 Where sprinkler systems or aboveground fire service mains are required to be protected against damage from earthquakes 2020 Where waterbased fire protection systems are required to be protected against damage from earthquakes 2. General Intent of Earthquake Protection Provisions 1983 Minimize or prevent pipe breakage 1991 Prevent pipe breakage 19