【正文】 cal 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)。 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。 Figure added to appendix 1989 Added “regardless of size” 1991 Designated as “seismic separation assemblies with flexible fittings”。in. pipe (4 in. larger for 4 inch and larger pipe)。 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。 Exception for runs less than 12 ft. in length supported by braces on adjacent runs。 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。 Appendix figures show lateral braces “about 40 ft.” 1985 Lateral bracing at maximum 40 ft. centers 1989 Maximum spacing to 50 ft. when building primary structural members exceed 40 ft. on center 1996 Distance between last brace and end of pipe limited to 20 ft. (25 ft where braces up to 50 ft. .)。 2020 ASCE Copyright ASCE 2020 Structures Congress 2020 Downloaded 06 Mar 2020 to . Redistribution subject to ASCE license or copyright。 Uhooks used to satisfy requirements for restraint required to have legs bent out 30o from vertical 2020 Except where branch lines are supported by rods less than 6 in. (150 mm) in length, restraint of all branch lines is required, with maximum distance between restraints ranging from 27 to 55 ft ( to m) depending on the size of the branch line and the force level。 see Maximum length load tables added to appendix based on three ranges of angle from vertical 1989 Maximum length and load tables moved from appendix to body of standard 1994 Allowable slenderness ratio increased to 300 1996 Sway brace assemblies required to be listed for a maximum allowable load。 Threaded pipe used as part of a sway brace assembly to be not less than Schedule 30。 Fastener load tables added to appendix based on six orientation/angle conditions 1989 Fastener load tables moved from appendix to body of standard and expanded to nine orientation/angle conditions 1994 Powderdriven fasteners not permitted to attach braces unless specifically listed for this service 2020 Structures Congress: New Horizons and Better Practices 169。 Exception to permit lag screws/lag bolts where through bolts not practical due to thickness or inaccessibility。 Ctype clamps prohibited from attaching braces 1996 Retaining straps used on Cclamps to be listed for use under seismic conditions or to be a steel strap not less than 16 gauge thickness and 1 in. wide, wrapped around beam flange not less than 1 inch。 see Drake, . and Bachman, ., “NEHRP Provisions for Nonstructural Components,” ASCE Journal of Architectural Engineering, March 1996. 8. Voss, D., “The Importance of Adequate Seismic Design of Sprinkler Systems Following the 1987 Bay of Plenty Earthquake, 1987 Conference of the Institute of Fire Engineers, September 1987. 9. NFPA 13 – Installation of Sprinkler Systems, National Fire Protection Association, 1983, 1985, 1987, 1989, 1991, 1994, 1996, 1999, 2020 and 2020 editions. 。 Exception added to permit powderdriven fasteners to attach braces where specially listed for use in earthquake areas 1999 Powderdriven fasteners prohibited from use with system hangers where horizontal force factor Fp exceeds Wp unless they are specially listed for such use NFPA 13 is generally updated on a threeyear cycle. As additional earthquake experience is obtained, more refinements will be made to the requirements of the standard to help ensure satisfactory performance in earthquakes. Although fire sprinkler systems are not expected to provide structural integrity to a building, they are expected to be able to carry out their function in any building that does maintain its structural integrity through an earthquake event. References 1. NBFU 13 – Installation of Sprinkler Systems, National Board of Fire Underwriters, 1947. 2. NFPA 13– Installat