【正文】 ion 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 1999 Protect against damage 3. Flexible Couplings General 1983 For piping 3189。 (IBC). Because of the reference to ASCE/SEI 7, the 2020 IBC does not contain the detailed seismic requirements that had been included in the 2020 edition of the IBC. Although general reference to the 1999 edition of NFPA 13 is contained in the 2020 IBC, a section of ASCE/SEI 7 that made special reference to the use of NFPA 13 for earthquake protection was omitted during the adoption process, leading some to believe that sprinkler piping must be protected the same as other mechanical piping. However, sprinkler system piping is not arranged like other mechanical piping systems, and some of the rules of NFPA 13 have been specifically developed to prevent system damage during earthquake movement. For example, while most mechanical piping supported by hanger rods less than 12 in. (400 mm) in length is exempt from bracing under current codes, parative experience of sprinkler systems with that exemption versus the NFPA exemption of only 6 in (150 m) was provided by the 1987 New Zealand earthquake. The 2020 Structures Congress: New Horizons and Better Practices 169。 see NFPA 13 Earthquake Protection Submittee was in place at the time of the Loma Prieta and Northridge earthquakes in 1989 and 1994, and held public hearings in cooperation with the National Fire Sprinkler Association and the Society of Fire Protection Engineers following those events in order to evaluate how fire sprinkler systems performed during the earthquakes ands to develop suggestions for improvements to the protection criteria within the standard. In general, the performance of fire sprinkler systems in those earthquakes was judged to be good, with a strong correlationbetween observed failures and departures from the rules of NFPA 13. One area acknowledged to be in need of improvement was the interaction of sprinklers and ceilings。The Evolution of Seismic Design of Fire Sprinkler Systems Russell P. Fleming, . Executive Vice President National Fire Sprinkler Association Patterson, NY Special fire sprinkler system installation guidance intended to guard against damage due to earthquakes first appeared in the North American sprinkler installation standard in 1947, and was largely based on experience in the Long Beach earthquake of 1930. At that time many building codes in use in the United States did not even address the subject of earthquakes. Insurance reports of the Long Beach earthquake had indicated 90 damaged sprinkler systems. The first guidance, contained only in the appendix, called for 1 to 2 inches clearance around pipes, flexible couplings in risers and “some form of lateral and longitudinal bracing” for feed and cross mains. In the 1951 edition requirements were placed in the body of the standard for placement of longitudinal and lateral braces with spacing indicated as “30 to 40 ft”, a maximum slenderness ratio of brace members of 200, and flexible couplings on risers where it was necessary to protect systems against earthquakes. The stated intent was to laterally brace for 50% of weight of waterfilled piping and attachments. In the decades since then deliberate efforts have been made to clarify the rules and improve protection within the text of NFPA 13 – Installation of Sprinkler Systems, but always with the intent of addressing “how” systems are to be protected against earthquakes, not “where” such protection is to be provided. It was recognized that building codes and other authorities made the basic decisions with regard to the location of earthquakeprone areas. Although the earliest guidance contained in NFPA 13 came from the insurance industry in the western states, the NFPA Committee on Automatic Sprinklers formed an Earthquake Protection Submittee in 1985. One of the goals of this submittee was to develop a means to address the bracing of sprinkler systems in the same manner that the application of system hydraulics had been acplished. Although a plex subject, it was believed that many of the design aspects could be preengineered into tables and then properly applied by the technicians who normally lay out and detail fire sprinkler systems. The 1983 standard contained no information on the sizing or fastening of bracing relative to loads. A method was proposed in 1984 whereby “zones of influence” could be evaluated to determine total loads for proposed brace locations. Tables were proposed for determining maximum brace loads and allowable fastener loads based on six different binations of brace and fastener orientation and angle from vertical. This concept and the acpanying tables were accepted into the appendix of the standard in the 1987 edition, and in the 1989 edition the tables were expanded to nine binations of orientation and angle and moved into the body of the standard. 2020 Structures Congress: New Horizons and