sprinkler loads on trusses - drj best practices · and applies to both roof and floor ... •the...
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Sprinkler Loads on Trusses
Design Guide
Revised 3/22/2017
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Introduction
• Building Designers must account for the dead and live loads of fire sprinkler systems in the building design.
• Truss Designers must incorporate these additional loads into the truss design.
• This presentation contains general guidance and industry best practices, and applies to both roof and floor trusses.
• Specific designs should be confirmed with the local building authorities.
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Step 1: Dead Loads
• Trusses must be designed to carry the additional weight of the sprinkler system
• Both the pipes and the water inside are considered a dead load
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Step 1: Dead Loads
• The fire sprinkler system can be supported from either the top chord or the bottom chord of the truss.
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Step 1: Dead Loads
• The Building Designer should provide the following information to the Truss Designer: – Uniform dead load to
account for the sprinkler system
– Any concentrated dead loads not included in the uniform load, if applicable
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Step 1: Dead Loads
• Where attachment locations are known, concentrated dead loads for the sprinkler system may be given instead of uniform loads
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Step 1: Dead Loads
• Typical values range from 1.5 to 6 PSF, depending on the nominal size of the pipe and the hanger spacing.
• Consult the Building Designer or sprinkler system Engineer to obtain exact values
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Step 2: Live Loads
• The trusses should also be designed for a 250-lb concentrated live load
• This is applied to any single support point, but not simultaneously to all support points.
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Step 2: Live Loads
• The intent of the 250-lb live load provision is to accommodate the weight of sprinkler installation personnel for a very short time during installation
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Step 2: Live Loads
• If multiple sprinkler lines are attached to the same truss, the 250-lb load should be applied at only one location at a time, representing only one worker per truss
• The 250-lb live load need not be considered simultaneously with other live loads (i.e., roof, snow, wind, etc.).
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Step 2: Live Loads
• Most truss design software can automatically apply a specified “sprinkler load”to each panel and mid-panel point in separate load cases
• This approach is conservative, but allows for variance in the installed location
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Step 3: Truss Layout and Webbing
• Truss construction is highly compatible with sprinkler systems.
• The truss designs and sprinkler system design need to be coordinated to eliminate conflicts
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Step 3: Truss Layout and Webbing
• Ideally, sprinkler system water lines run through open webbing, and attachment points coincide with panel points
• If coordinated in advance, panel lengths and webbing configurations can easily be modified to accommodate
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Step 3: Truss Layout and Webbing
• Truss construction along with advance planning can safeguard the builder against issues such as:
– Drilling through structural members for pipe runs
– Loss of headroom due to piping
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Step 4: Special Engineering
• Additional engineering design may be required if any of the following conditions are present:– Large diameter (>4”) pipe
lines
– Significant risers
– Pipe lines running parallel to trusses
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Step 4: Special Engineering
• A maximum of one sprinkler system support may be attached to each truss panel.
• If more than one support is needed in any panel, special engineering is required, and a Registered Design Professional should be contracted.
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Step 4: Special Engineering
• Lateral loads resulting from sprinkler systems, where required, should be evaluated separately by a Registered Design Professional.