Moment Capacity of pinned vs fixed beams 2

[jay156]

Hi, I'm doing some calculations for girders on that open-air storage building from my other thread. The girders are going to be rigidly attached to the columns, so in my computer model I modeled them as fixed. I looked at the report it gave me and it said the beam was failing. So I tried modeling it as pinned just for the heck of it.

In the report it shows the moment capacity for the girder, a W21x44, is 357.75 k-ft when pinned, and 134.34 k-ft when fixed.

Does that make any sense? Is there a part in the code that says a beam can support more moment when pinned at both ends than when it's fixed at both ends? I don't remember anything about that. Might my software be screwed up?

 

[BAretired]

jay156,

Just one more point. Ten spaces at 3.42 means your beams are spanning 34.2' and in your previous thread you indicated the columns were spaced at 30'-9" which would also be the joist length.

In my experience, the best economy in a rectangular bay is to allow joists to span the longer distance and beams to span the shorter distance. Joists would usually be spaced at about 6' centers.

BA