We’ve now added automatic live load patterning to US beams! This is still in beta as there’s a few missing features we want to add, but you can now already use it to automatically determine your moment, shear, deflection with that in consideration.
Watch a video here where I go over the feature: Loom | Free Screen & Video Recording Software | Loom
This is a nice next-level feature that may come in real handy. I’m so used to making judgment calls with live load placements that it may take some time to get used to this.
In fact, I have been presented with a stupid house design concept where the client wants to cantilever the first floor joists 2ft while also supporting the 2nd floor and roof. It’ll be interesting to see how this can be used.
That’s great to hear, Jim! Very curious to see how it will go with the joists! The fun part is that the results from the load patterning will also transfer through linking, so you can be confident you’ve got the max loads in your walls as well.
I’m trying this live load patterning option on a 12ft floor joist with a 2ft cantilever at the one end. There is a large snow/roof load acting on the tip and live load along the full length of the joist. I see very slight (<5%) in the reactions and deflections, but it’s negligible compared to the difference I get when I change it manually.
Is the cantilevered beam option not included finished yet?
Thanks for trying this out! This had me quite confused but I think I understand what’s going on - currently we only do live load patterning with regular live load. Roof live loads aren’t getting patterned. This is mostly based on our interpretation of ASCE 7, that Roof Live Loads only need to be patterned if reduced to < 20 psf. Is that how you (and others here) also handle these loads?
I don’t know what ASCE 7 requires in this case and would not default to that in my analysis.
In this case, there is snow/2nd floor live/wall load all concentrated at the tip of a floor joist cantilever. I was expecting that live load patterning would help me find the worst-case uplift at the rear support while also finding the largest down-force at the support next to the cantilever. One has full live load along the main span and the other does not. Roof loads are not patterned.
For what it’s worth, I am also paying attention to the conservatism that comes with applying 100% live load to one floor and 0% to another floor while also considering 100% snow on a roof above.
I tried load patterning on a two-span + cantilever deck joist that also supports a hot tub. I have an 85psf live load for the tub+water and a 40psf live load across the full length of the joists for people.
Let me be the first to say that this worked awesome! And, it saved me the step of manually setting up different models to anticipate the load locations that would maximize the reactions and moments.
And if you ever add in patterning with live point loads (i.e., loads from a floor above) then I will be doubly impressed. Hint hint…
I’m also happy to see live load patterning available… is there a way to see the cases as you outlined them? Right now, I see somewhat opaque combinations L3 and L4 on a simple 2-span beam… perhaps you could label the cases so that it’d be more obvious what you’re doing from the labels?
For example, for your post above, perhaps label cases in the “unfactored analysis” reactions as:
LL = Live load applied on both spans,
L- = Live Load applied on left span and no live load on right span, and -L = No Live Load on Left Span and Live Load on Right Span
It’d also be handy to be able to use these combos on the graphs, and used for roof live cases where Lr < 20… basically just run a check to see if that’s the case, before running the analysis.
Hey @themathguy thanks for your comment!
It’s on our todo list to add better visualization for these load cases - as you mentioned we could certainly be more transparent right now. This will likely be coming in the next few months as part of a larger overhaul of our standard beam diagrams.
