【正文】 Distance between last brace and end of pipe limited to 20 ft. (25 ft where braces up to 50 ft. .)。 see Brace for feed and cross mains。 Loads in allowable brace load table reduced by factor of to bring into line with allowable stress approach 11. Sway Bracing Longitudinal Braces 2020 Structures Congress: New Horizons and Better Practices 169。 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。 Exception for runs less than 12 ft. in length supported by braces on adjacent runs。 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。 Tops of risers secured against drifting in any direction using 4way brace 1987 – Zone of influence method added to appendix with maximum load tables for pipe, angles, rods and flats based on three ranges of angle from vertical and maximum slenderness ratio of 200 2020 Structures Congress: New Horizons and Better Practices 169。 Clearance not required for horizontal piping passing perpendicularly through successive studs or joists that form a wall/ceiling assembly。in. pipe (4 in. larger for 4 inch and larger pipe)。in pipe, 2 in. all sides 4inch and larger。 Figure added to appendix 1989 Added “regardless of size” 1991 Designated as “seismic separation assemblies with flexible fittings”。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 Flexible coupling within 24 in. of the ceiling at top of drops exceeding 15 ft. to portions of systems supplying more than one sprinkler (regardless of size) 1994 Deleted “of the ceiling” 1996 Added “at top and bottom” of drops supplying hose lines, rack sprinklers and mezzanines 2020 – Additional flexible couplings for drops required within n 24 in. above the uppermost drop support or, where no drop support is provided, within 24 in. above the bottom of the drop 6. Flexible Couplings for Expansion Joints 1983 On one side of building expansion joints 1987 At or near building expansion joints。 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)。 Additional coupling required on vertical portion of tiein piping where tiein is below the upper flexible coupling on the riser 2020 Additional flexible coupling can be provided either on the vertical portion of tiein piping or within 24 in. on horizontal tiein piping 5. Drops to Hose Lines, Sprinklers in Racks, and Portions of Systems 1983 Fittings with flexible joints at the top of drops to hose lines (regardless of size)。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 in. or larger。 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 protect