Truss Design: Difference between revisions
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*For a 32' long truss with 1/2" web, the limiting factor for span is not the web - it's the chords. In fact, there could be a break in the OSB in the middle, and it would not affect the truss bearing capacity much - but a break near the support points would be catastrophic. [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f] | *For a 32' long truss with 1/2" web, the limiting factor for span is not the web - it's the chords. In fact, there could be a break in the OSB in the middle, and it would not affect the truss bearing capacity much - but a break near the support points would be catastrophic. [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f] | ||
*32' truss with 24" on center - 1/2" web by 16" tall - has 3200 lb on it at 50 psf, and 1600 shear at ends. Shear capacity of the OSB is 2400 lb, so we are fine on shear. [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f]. We are not fine on tension at bottom chord [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f] | *32' truss with 24" on center - 1/2" web by 16" tall - has 3200 lb on it at 50 psf, and 1600 shear at ends. Shear capacity of the OSB is 2400 lb, so we are fine on shear. [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f]. We are not fine on tension at bottom chord [https://chatgpt.com/share/68731799-c884-8010-b1d4-405eacd6938f] | ||
*{{check))'''Solution : use half inch rebar, 20' long, stapled to the bottom of the bottom 2x4 chord of the truss. 100+ staples with the rebar holds a total of 12000 lb of tension - exceeding the tension requirement of a 32' joist bottom chord - for rated design of 50 psf total roof load.''' | |||
=Links= | =Links= | ||
*[[I-Joists]] | *[[I-Joists]] | ||
Revision as of 03:42, 13 July 2025
- For a 32' long truss with 1/2" web, the limiting factor for span is not the web - it's the chords. In fact, there could be a break in the OSB in the middle, and it would not affect the truss bearing capacity much - but a break near the support points would be catastrophic. [1]
- 32' truss with 24" on center - 1/2" web by 16" tall - has 3200 lb on it at 50 psf, and 1600 shear at ends. Shear capacity of the OSB is 2400 lb, so we are fine on shear. [2]. We are not fine on tension at bottom chord [3]
- {{check))Solution : use half inch rebar, 20' long, stapled to the bottom of the bottom 2x4 chord of the truss. 100+ staples with the rebar holds a total of 12000 lb of tension - exceeding the tension requirement of a 32' joist bottom chord - for rated design of 50 psf total roof load.