Steel Roof Truss Span To Depth Ratio

The architectural design of the building determines its external geometry and governs the slope s given to the top chord of the truss.

Steel roof truss span to depth ratio. For pitched trusses an effective depth to span ratio between 1 5 and 1 6 is recommended and a minimum of not less than 1 7 unless special consideration is given to deflection. The load span tables shown below demonstrate only a tiny subset of the possible combinations available with trussteel cfs roof trusses. 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. 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. Plate girder web thickness about depth 160. Metal plate connected wood trusses hib 91 by permission of truss plate institute inc. 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.

Even though the overall bending effect is larger at mid span the chord member and web member stresses are smaller closer to the mid span and larger closer to the supports. The suggested effective depth to span ratio is between 1 6 and 1 8. 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. 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.

Intermediate bearing simple span trusses header beam pocket floor truss supporting header beam. Roof floor truss manual 7 31 08 10 43 am page 11. 25 t to 75 t crane 8 over 75 t crane 7. The lower the ratio the longer are the shear members in the truss and the larger is the volume occupied by the roof structure.

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. General p roportions of steel structures. Valleys and piggyback trusses must have verticals 4 o c. For efficient structural performance the ratio of span to truss depth should be chosen in the range 10 to 15.

The span to depth ratio of trusses ranges from 10 to 25 depending on the intensity of the applied load.