Thanks for the responses! I slept on it over night, and I was able to get it to work. Basically, I grouped the three compression load legs of the tower crane into a single node at the centroid of the load, and it greatly simplified the model. Now all of my diagonal struts are compression...
So, I am just learning strut and tie and had a three dimension footing over (4) drilled pier footing that is supporting a tower crane. The worse case load case for the tower crane is on the diagonal, where I will get tension on one pier, a big compression on the opposite pier, and two smaller...
So a co-worker has a core wall at an elevator and stair on a six story P/T slab building going up in Seismic Design Category D. This is a crazy postage stamp sized building where the architect is trying really hard to make the floor plan work on a tight lot. On this building, on the first...
Commentary to Chapter 11 in the Seismic Design Manual (page 6.1-170) talks about OMF Knee-Brace Systems, so they are allowed as long as you are in a region where OMF's are allowed. But OMF's are pretty significantly hindered in SDC's D and above, where the overall seismic dead load of the roof...
On a recent project, there was a mix-up on some exterior architectural concrete elements where air entrainment inadvertantly got left out of the concrete. What would be the mitigation for this (short of removal and replacement) . . . the concrete supplier is suggesting a penetrating sealer to...
I have done a fair amount of reshoring. The reshores are to take the loads from construction operations of the structure above. So as long as you don't apply wet concrete loads from the next pour, and don't put a ton of weight on the curing slabs, you don't necessarily need reshoring to be put...
I was just looking for some general opinions on the Brittle Element factor in the 2006 IBC . . . Section 1908.1.16. Here they say that if you don't have a ductile steel failure in your anchorage, you have to multiply your design loads by 2.5. Between Omega Loads on drag connections, the 0.75...
I am retrofitting an existing braced frame connection by installing new epoxy anchors. Basically, I was running in to compounding load factors in using ACI Appendix D . . . Seismic anchorage forces are designed for Omega (Ordinary braced frame). For bond strength, you get a regular phi of 0.55...
I have a cantilevered concrete beam, and I want to know what the moment is at the face of the cantilever if I deflect the beam a certain number of inches. Or at the very least, I would like to know if the beam would fail at that amount of deflection.
This is actually an existing concrete...
Just a general question . . . I heard a contractor one time talk about doing the cladding on a 20+ story tower that had P/T Slab floors. He talked about how it was hard to get the cladding to line up from floor to floor as they went up the building, because the building would move back and...
Are there any horizontal snow pressures that build up from deep layers of mountain snow? In all of our research, we have not found any mention of horizontal snow pressures.
I understand that a heated space will melt the snow back from the face of the wall, leaving an air space and no...
I didn't think that was the purpose. A typically sized slab loaded with a single floor's amount of load wouldn't have much more than its self weight "balanced," so it should be relatively rare that you would have tension at the bottom of the slab (maybe at short bay conditions where somebody...
In plan review on a few projects, I have noticed that some two way P/T Slabs specify a group of bottom bars centered over the columns that is on par with the total amount of top steel added above the column. I am a little bit embarassed, but I am not sure what this bottom steel is for. On...
You would be amazed at how many contractors simply pour elevated slabs, with shoring posts bearing on slabs on grades, without even thinking about the capacity of the slab. 8,000 or 10,000 lb loads 6' on center each way, and they don't even bat an eye. They might put a wood shim down to get...
You also have the option of using an actual sheathing material to make a shearwall, as opposed to straps and gusset plates. Sureboard sheathing is one option for non-combustible applications, and would have a higher R value than tension only straps.
