Foundation Reactions
Foundation Reactions
(OP)
I have a job where I am not responsible for the design of the foundation system. I have all of my loads broken down into service dead, live, wind and seismic values. I prepare my reactions this way so that the foundation engineer can properly design his foundations.
The reactions have been submitted to the foundation engineer who is refusing to design the foundation until I give him worst case loading on his foundation system. Basically he is asking me to interpret the load combinations of the code for him. I avoid doing this because of the increased liability.
What do you guys do with providing reactions to another engineer to design foundations?
I understand with computer programs today, it is easy to export the reactions after they have been run through the load combinations.
The reactions have been submitted to the foundation engineer who is refusing to design the foundation until I give him worst case loading on his foundation system. Basically he is asking me to interpret the load combinations of the code for him. I avoid doing this because of the increased liability.
What do you guys do with providing reactions to another engineer to design foundations?
I understand with computer programs today, it is easy to export the reactions after they have been run through the load combinations.






RE: Foundation Reactions
We are Virginia Tech
Go HOKIES
RE: Foundation Reactions
I worked for a firm at one time where we did very little foundation work so we were issuing foundation reactions all the time.
Your foundation guy should be figuring out his own load combo's.
We usually factored the loads up quite a bit and issued them as "not to exceed" since they were often required early on in the job. We had to leave ourselves some wiggle room since we were essentially promising "not to exceed" them.
So we factored them up and I am sure the foundation guy threw some extra safety in there too....all said and done we probably had foundations that were 2 times bigger than they needed to be.
RE: Foundation Reactions
That would be like the building designer asking a code official or a equipment vendor what is the worst case load on the building.
RE: Foundation Reactions
RE: Foundation Reactions
I can see your point there, but it sounds like he has his reactions pretty solidly labeled.
RE: Foundation Reactions
I have designed metal building foundation systems many times and I hear your frustration with the way the reactions are presented. However, it is very easy to cut through the BS and figure out what loads are applied to the foundation system. To ask the metal building mfr. to make this interpretation for you is risky. How do you know they are even giving you the proper reactions for your foundation design? Do you back check them, or just say that it is not your responsibility and place a not on your drawings stating the reactions you designed your foundation for were provided by (fill in the blank)?
RE: Foundation Reactions
Dear Mr. Engineer:
My building reaction loads are as follows:
DL = xx lbs
RLL = xx lbs
RSL = xx lbs
RWL1 = xx lbs
(etc.)
The building code outlines several load combinations that are required. You, as the foundation engineer, can simply take the above load cases and combine them in accordance with the code using simple high school algebraic methods.
Should you require assistance with these basic procedures, we would be happy to assist you in developing a comprehensive plan and solution to your calculation needs.
Attached are our standard hourly rates that would be applicable should you choose to utilize our services.
As an estimate, we would expect the fees for these services to be between $3,000 and $4,000. Please advise us if you desire to pursue this and we will quickly get you a fee proposal contract form. A retainer fee in the amount of 50% of the above estimated fee will be required.
Sincerely,
xxxx
So my thoughts - shame them into doing their own work.
RE: Foundation Reactions
I was totally baffled....
RE: Foundation Reactions
By the way, it may not be conservative to have one 'worst' case to check. I did have combo reaction forces from my colleague who worked on superstructures. But I have to make my judgement to figure out the worst cases, e.g. a smaller vertical reaction is likely to a worse case when checking stabilities (overturning or sliding). Section 1605 of ASCE7-05 should be followed in your case.
RE: Foundation Reactions
I completely agree. How am I to know what is going to control the design of the foundation system. I have a general idea, but since I am not the designer it is not my responsibility.
RE: Foundation Reactions
RE: Foundation Reactions
We were doing an excavation bracing job about 40' deep requiring tiebacks. The phone company told us that their west coast trunkline was under the street behind the cut somewhere, but for security reasons they couldn't tell us where.....
RE: Foundation Reactions
RE: Foundation Reactions
What effect does this have on the overall question above?
RE: Foundation Reactions
I think their security "reasons" looked a lot like donuts and coffee
RE: Foundation Reactions
That may be true of the superstructure (and specifically internal stresses in the members), but the reactions are the reactions.. The foundation engineer can use the loads and decide whether he is to carry out a linear or non-linear analysis of the foundation system.
I'm with the majority on this one.. seems like the foundation engineer doesn't want to do his job.
RE: Foundation Reactions
RE: Foundation Reactions
Is he just going to use those loads only?
when doing my own buildings and foundations, I may have tons of load combos for the steel design.
When it comes to foundation time, I just use all my service level reactions and make up some new combinations...i have never just used the load envelop and designed the foundation for that!
RE: Foundation Reactions
And nobody realizes why I want no part of this (at least outside of this forum)! You need strength level loads to properly design the concrete in the foundation system. How are min and max loads going to help him with this.
RE: Foundation Reactions
RE: Foundation Reactions
I wish, actually, I wish I could dump the contract but I can't.
RE: Foundation Reactions
RE: Foundation Reactions
I have seen one engineer place a huge table on the design drawing in order to explain the load cases. I don't see how clarifying one's own design load cases increases one's risk. It would seem to me that clarity lowers risk.
Am I not understanding properly?
RE: Foundation Reactions
RE: Foundation Reactions
I can see where if it is a mat foundation or something similar the maximum and minimum reactions might not reflect the maximum and minimum forces on the foundation system.
RE: Foundation Reactions
I think it's the foundation engineer's job to combine the individual service loads as he/she sees fit.
RE: Foundation Reactions
If you were give him the solved equations for the 7 Strength Design and 8 Allowable strength combinations (referencing ASCE 7) essential giving him 15 loads max and min included, would he be happy then, or would he still require interpertation?
RE: Foundation Reactions
RE: Foundation Reactions
Personally, I like to see it presented both ways so that I can see what the metal building designer did, and manipulate the numbers to suit what I need to do. I just feel more confortable with that. Hard to get, but preferred.
No worries.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask