Roof floor truss manual 7 31 08 10 43 am page 11.
Steel roof truss span to depth ratio.
The load span tables shown below demonstrate only a tiny subset of the possible combinations available with trussteel cfs roof trusses.
The span to depth ratio of trusses ranges from 10 to 25 depending on the intensity of the applied load.
A brace should have a capacity in the order of 2 of the force in the main compression member or in the compression flange of a beam or girder.
The architectural design of the building determines its external geometry and governs the slope s given to the top chord of the truss.
05425 cold formed steel trusses roof truss spans every trussteel roof truss is a custom design based upon the unique load span bearing use and code criteria of a particular project.
25 t to 75 t crane 8 over 75 t crane 7.
General p roportions of steel structures.
Intermediate bearing simple span trusses header beam pocket floor truss supporting header beam.
For efficient structural performance the ratio of span to truss depth should be chosen in the range 10 to 15.
The lower the ratio the longer are the shear members in the truss and the larger is the volume occupied by the roof structure.
A radius equal to the span will give a ratio slightly larger than the suggested minimum.
Most economical when the difference in slope between the top and bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch.
The suggested effective depth to span ratio is between 1 6 and 1 8.
Design of roof purlins 6 for efficient structural performance it is recommended that the truss span to depth ratio be kept between 10 to 15.
7 in the layout of truss systems it is more preferable in terms of economy and efficiency to have the shorter members in compression and the longer members in tension.
Maximum span to depth ratio is 24 for parallel chord roof trusses for example a 24 deep parallel chord roof truss should not exceed a span of 48.
Or close to it in odd panel.
Valleys and piggyback trusses must have verticals 4 o c.
Plate girder web thickness about depth 160.
The typical span to maximum depth ratios of pitched roof trusses are in the range of 4 to 8 the larger ratio being economical in longer spans.
Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches.
