Wow. I have a different view of what Ultimate wind loads are. It has nothing to do with safety. Using 1.2D + 1.0W + L combo for example, note the lack of load factors except 1.2 for dead load. When designing to this load combo, the structure is at the yield point. It is on the knife's edge of...
"Tack welding of rebar shall always be prohibited." -- Never mind that the rebar details in the footing are driven by temp and shrinkage, not ultimate or service loads, and whatever small strength that is lost at the rebar connections are insignificant and immaterial.
Even though this is not a telecomm tower I would use the TIA-222 standard. The equations, methods, etc. are all highly refined for just this application, a lattice tower made out of angle iron. Wind loading, and the resulting P-delta, are important for a 60-foot standalone tower. Don't forget...
Speaking of 7-16 wind speeds, I'm somewhat amazed at the drop in basic design speeds on the west coast. Using Fresno, Calif. as an example:
7-10: Cat II 110 mph 1.2D + 1.0W
7-16: Cat II 94 mph 1.2D + 1.0W
That's about a 27% drop in design q.
I really don't see how vortex shedding would be a problem here. Shedding won't occur around the tower as a whole because, like WARose said, the solidity is far too low. Shedding can develop as the air flows around each leg, however. But the entire length of the leg can't develop a harmonic...
zdas04: "Ten climate related disasters? in 2015" What where they?
You're right, I should have written "ten weather related disasters" not climate related disasters. The list of events is listed here: http://www.ncdc.noaa.gov/billions/events
While it is true that no weather event is directly...
Looking at the big picture, the O.P. is correct, the phrase "renewable energy" is a poorly defined and sloppy term. Technically there is no such thing as renewable energy because the arrow of entropy only points one way. Even solar power is not renewable -- once a pair of H nuclei fuse to form...
@bookowski wrote: "Run one model with a single element and another with divided elements. If it's linear you will get identical results, if it's performing p-d you won't."
Of course, thank you for the suggestion. Set up a simple model of a 20-foot tall HSS 2.50x0.125 A36 steel tube. 100 lbs...
@JoshPlum: It's a linear FEA program. And maybe this gets at the heart of my thinking: that linearity (Hooke's Law) holds for each segment. Now as the column is broken up into an increasing number of segments, the accumulated nodal deflections and strains act as a limit function and approach the...
Apologies if this seems like an elementary question, but I haven't been able to confirm the answer searching here or elsewhere. Given: a slender steel column with a downward vertical force P at the top and a sideways force P, also at the top. Assume the material is in the elastic region and...
Bah, tower software is for wimps. Real engineers model their towers with a generic FEA program from scratch. ;-) I have done this. The disadvantage is that it can get tedious to post-process the FEA output vs. factored material strengths. The advantage is you really get to know TIA-222-G and...
It appears to be a different mode of failure? Bearing strength failure is due to cracking, while anchor bolt pullout failure involves localized crushing around the bolt head (source: ACI D commentary).
@ Agent666: thanks, I understand the concept of effective stiffness. This document doesn't provide what I'm looking for, which is a general geometric equation for the moment of inertia of a chordal area and of a chordal portion of a hollow tube.
I'm working on a design that includes a concrete-filled steel tube. Might anyone have equations handy for the moments of inertia when the neutral axis does not go through the center (see attached diagram)?
Referring to the diagram, I'm looking for the MoI of the concrete in compression (area...
Thank all of you very much for your responses. Enhineyero your explanation was clear and helpful -- and you're right, using your suggested method keeps the footing size reasonable.
Older PE here. I admit I'm rusty and I'm doing my best to get up to current methods and standards.
Project is a self-supported lattice tower with a simple gravity mass footing. Tower mfr. shared some sample calcs with me. Calcs show LRFD basis for wind force and sizing the lattice members...
