I am a new RAM Structural user, but was a joist engineer for over 10 years, and I am trying to figure out the nonuniform load calculation method for joists in Ram Structural. I have a case of dead+base snow+snow drift that I am checking, and the joist design report shows the correct shear and moment for the uniform + trapezoidal loading, and it shows an equivalent uniform dead and live load that makes sense. The equivalent design total load, however, is not the sum of the dead and live loads, nor is it backsolved from the max moment or max shear, or derived from the total loading divided by length. It's saying I need a 20K4SP when I come up with a 16K4, but it also says the design total load is a good 60plf higher than I can come up with from any of the above methods. If anyone can tell me the basis for how the program arrives at the "total design load" shown halfway through the joist design report, I would greatly appreciate it.
As background, the situation is a roof bay with joists at 25'-10" length, 6' o.c. max, with 20 psf DL, 10 psf base snow, and a 15' long drift going from 68psf at left support to 10 psf at 15'.
Thanks.
Yes, I had already read through that section, and the 1.6" of reported total load deflection did match up with the equivalent total load, but that deflection is considerably higher than what I get hand-calcing it or checking it in Enercalc. So it seems to come back to a case of the equivalent total load being too high. I'll send it in. Thanks.
The program also backs out a design load for deflection. Section 4.2.3 in the RAM Steel Beam manual discusses nonuniform loads. If you continue to have questions, please submit a service ticket online and include the model. We would be happy to replicate the calculation for you.