Keeping track factored and unfactored
Keeping track factored and unfactored
(OP)
Usually I feel that it is very hard to keep track load factored and unfactored load. You will need unfactored load for shear diaphragm for steel deck, soil bearing foundation, etc. Then you need factored load for your steel and concrete design. On the top of that, you have so many load combinations. Do you think one day we will use strength design on everything (i.e. soil) so we dont have to know the service load anymore? I am fairly green and I find this very overwhelming even with computer software like RAM where it will generate LRFD and ASD load combinations for you. Comments and thoughts?
Never, but never question engineer's judgement






RE: Keeping track factored and unfactored
RE: Keeping track factored and unfactored
Why? Probably something to do with keeping track of the 100 plus load cases and thousands of members being complicated enough.
RE: Keeping track factored and unfactored
Never, but never question engineer's judgement
RE: Keeping track factored and unfactored
The foundation module has different load combinations. It uses ASD combinations for soil bearing (sizing the footing) and uses LRFD combinations for the design of the footing for strength.
Also, in RAM Frame, you can show the service diaphragm shear at each story.
RE: Keeping track factored and unfactored
RE: Keeping track factored and unfactored
Never, but never question engineer's judgement
RE: Keeping track factored and unfactored
In anycase it's a huge bookkeeping problem. At the end of the day, load factors aside, WSD aside, we still run the actual load from the top to the foundation as ONE of our runs.
By the way in our latest code the load factors for serviceability limit states design, ie deflection/drift etc, re wind and snow are 0.75 and 0.9 respectively for 'normal' buildings ... we don't even use the actual loads, they are factored down!
Factor up, factor down. Predict failure.
It's a game of statistics and probability that doesn't make much sense to me. Twice in the last 10 years we have meet or exceeded the specified 30 year (now 50, as of 2006) design snow loads in our area.
Go figure.
Lets not talk seismic.
The Ontario Building Code is the largest regulation in this province of Canada.
We don't charge enough.
Its a wonder anything stands.
One to many beers.
Got to go.
RE: Keeping track factored and unfactored
I didn't have any issues with the soil pressures. I had a allowable of 3ksf, and it stays under that for footing plan sizing, but was routinely higher than that for the strength combinations.
Is there a chance you have a minimum footing size in there such that the strength combinations are giving bearing pressures below the allowable?
Print a report and look at the max unfactored pressure and the max factored pressure.
RE: Keeping track factored and unfactored
Never, but never question engineer's judgement
RE: Keeping track factored and unfactored
Look at some other footings and see if this is common or if it's an isolated case.
Also, try setting the allowable lower - make it higher than the max unfactored, but lower than the max factored and see if it bumps up your footing size. Be careful, though, because if it's a lateral column you might get a higher size due to overturning considerations.
RE: Keeping track factored and unfactored
I also hate the fact that there is no place to turn off punching shear. If I have grade beams over the column, there should not be punching shear. I usually do not model the wall, I am not sure if it will do it correctly if I model the wall also.
Never, but never question engineer's judgement
RE: Keeping track factored and unfactored