Automatic Fire Sprinkler System Performance
THE NORTHRIDGE EARTHQUAKE
Based on and excerpted from the Fire Sprinkler Advisory Board-Southern California Northridge Earthquake report, published April 1,1994.
Automatic fire sprinkler systems (AFSS), like other structural and building components, suffered various degrees of damage as a result of the Northridge Earthquake. Whether the damage to the AFSS was less than, equal to, or greater than damage sustained by other mechanical systems within the structures is a question that can be debated. In most cases documented in this report, however, the owners or owners’ representatives state almost without exception that their AFSS performed as well as or better than the other mechanical systems.
Other factors that must be considered are the age of the system and the installation criteria under which it was designed, installed, and inspected. The 1991 Uniform Building Code™ (California Building Code) was adopted as a mimimum standard by the state of California on August 17, 1992, and was in effect at the time of the Northridge Earthquake. In addition, the state of California also had adopted NFPA-13, Standard for the Installation of Sprinkler Systems, 1989 edition; NFPA-13R, Standard for the Installation of Sprinkler Systems in Residential Occupancies up to Four Stories in Height, 1989 edition; and NFPA-13D. Standard for the Installation of Sprinkler Systems for Oneand Two-Family Dwellings and Mobile Homes, 1989 edition. In addition, an estimated 14,000 fire sprinkler services have been identified, 3,300 of which are located within the San Fernando Valley.
SOURCE OF DATA
To assess the performance of automatic fire sprinkler systems installed in the areas affected by the Northridge Earthquake, the Fire Sprinkler Advisory Board-Southern California (FSABSC) distributed more than 2,000 survey forms to fire sprinkler contractors, fire protection engineers, local building and fire agencies, insurance companies, and other interested parties. Approximately 11 percent (225) were returned completed.
The survey form in many cases was filled out by the sprinkler titters who did the actual repairs to the systems. Some survey forms were completed by FSABSC Director Steve Hart, who toured the earthquake-affected area on several occasions or took down the information from telephone interviews with sprinkler titters or fire protection contractors.
From the data collected it appears that damage to the systems could be categorized as follows:
- Seismic bracing. Longitudinal and lateral screw fasteners affected. Issues; Inadequate spacing, predrilled vs. hammered lag screw fasteners, power-driven studs, expansion shields, welded studs.
- Hangers. Fasteners. C-clamps without retaining straps. Issues; Predrilled vs. hammered lag (coach) screws, coach screw rods, power-driven studs, expansion shields, welded studs.
- Grooved fittings. Gasket material, rolled or cut grooves. Issues; Age and durability factor. dimensionally compatible with fittings.
- Concealed sprinkler assemblies. Cover assembly housing, cover painted/glued to ceiling finish.
- Piping materials. Brittleness of cut
- thread area, use of threadable thin wall for seismic bracing.
- Repair of sprinkler system. Inspection, code requirements, permits.
Note: Many of the systems were damaged as a result of the effect of the earthquake on the structural integrity of the buildings themselves.
One factor that must be considered is the issue of “quality control,” both from the installation and inspection/testing points of view. On the one hand is the fire protection industry and on the other is the local authority having jurisdiction (AHJ).
Contractors and their personnel must be competent and current with regard to changing code/standard requirements. Their design and installation methods must be revised as new codes/standards are revised and adopted by local AHJs. With few exceptions, the codes and standards that dictate the design and installation of tire sprinkler systems change in some fashion every three years as new technologies and products are developed.
To inspect the installation of automatic fire sprinkler systems, local AHJs must be kept abreast of the changes in the various codes and standards. Keeping pace with these changes and the new technologies associated with a growing industry is an ongoing challenge.
Automatic fire sprinkler systems must be subjected to a thorough plan review/check by individuals knowledgeable in trade practices and code/standard requirements. The field inspector must be kept abreast of these changes as well.
While NFPA-13 outlines the installation requirements for “sway-bracing” (earthquake protection) in Section 3-5.3 (1989 edition) and Section 4-5.4.3 (1991 edition), few field inspectors truly understand what is required. The plan checker, therefore, must insist that these seismic restraints be noted on the installation drawings, just as the fire sprinklers, valves, and drains are. The true art of plan review is to ensure that “good installa- tion instructions” have been developed.
The Northridge Earthquake caused a significant amount of damage to structures and building components throughout the Los Angeles Basin (Los Angeles, Glendale, Santa Monica, Fillmore, Ventura, Santa Paula, etc.). The damage to automatic fire sprinkler systems was reflective of the overall structural damage suffered by the building structures.
Some of the factors associated with the damage include the following:
- relative distance from the epicenter of the Northridge Earthquake and its aftershocks;
- intensity of the vertical and horizontal ground motion acceleration;
- age and type of construction;
- year of design/installation and the edition of the code and standard under which the fire sprinkler system was installed/ inspected;
- design quality of the fire sprinkler system, using the proper methods to support and brace the system;
- quality of the workmanship and the installation with respect to recognized trade practices at the time of installation;
- proper use of materials installed and the relationship to the adjacent building components;
- quality of the plan review and field inspection; and
- proper maintenance of the fire sprinkler systems.
Building code regulations often can be researched back to a multiple-fatality incident that resulted in the eventual updating of the code requirements to address certain issues raised. The installation standards for automatic fire sprinkler systems are no exception to that basic reactive principle. The code/standard-writing process is built on the understanding and study of an event, such as the Northridge Earthquake, so that design and installation practices for fire sprinklers are revised when it is deemed appropriate.
To review, address, and mitigate identiI Tied issues at the codeand standard-body writing levels is not enough, however; the ! revisions to the codes and standards ultii mately must be enforced by the local AHJs.
As these revisions evolve through the i “code/standard-writing process,” it becomes | apparent that certain issues must be addressed on a retroactive basis, which i would thus impose new solutions to existing : situations so that an acceptable level of safety for and protection of the system, structure, and occupants can be established and maintained.