How to Calculate Reinforce Concrete Foundation

1. Calculate load on footing.

2. Get allowable bearing pressure from soil report.

3. Determine footing area required.

4. Decide on shape. Simplest is square but not always possible.

5. Calculate shear and bending moment.

6. Determine depth to satisfy shear.

7. Determine reinforcement to resist bending moment.

And at number 8:

Send CR4 member ba/ael a cheque for engineer services!

Thanks, Doorman.

I was at a dinner party the other night at the yacht-club when a guy asked everyone at the table for structural engineering services to design or retrofit a column to support a beam where apparently a bearing wall had been or is scheduled to be removed.

As the only Registered PE (Civil) involved in the conversation, I quickly lost interest in bidding on these "services" as the client seemed to be more interested in a "quick and dirty solution" than a proper approach as you outline (to which I strongly endorse as necessary steps).

It seems other non-professionals were encouraging the prospective client to put the column on top of the existing slab (typically 4-inch non-reinforced concrete) rather than to remove a portion, excavate for, and place a proper footing.

When I tried to steer the conversation in that direction, the response seemed to be that such steps were not considered because they would require too much work (excavating a footing below an existing slab by hand, etc., would be troublesome).

Alternative plans to span the slab with plate steel to distribute the load (hoping not to punch through the slab) were then suggested by the arm-chair "Engineers".

After the Client (an unemployed airline pilot) received his "Broken Propeller Award" (this was an awards dinner) for the most spectacular grounding of the 2010 season, he again began discussing his problem of "where am I going to find a Registered Structural Engineer to stamp my drawings. But by this time, I had lost interest in the project and him as a prospective client.

Bruce, how do you deal with such issues?

The other question is whether in such cases, a Registered Civil Engineer could stamp the work involved here (or must he be Registered Structural Engineer). Had the client been willing to play by the rules (as you outlined), I might have considered the work.

Of course, I would want to get paid. No more free work for friends or acquaintances.

ps - I am not self-employed, but work for a large agency in the USA. I rarely stamp engineering drawings now in this position (although I maintain the licenses in several States).

"Bruce, how do you deal with such issues?"

I usually try to convince the arm-chair engineers of the proper way to deal with the situation. If that doesn't work, I try to change the subject. Sometimes you just can't win.

The question about who can stamp structural drawings varies from state to state. For an issue as simple as the one you describe, I would think that most states would permit a Civil Engineer to seal the documents, but I am no authority on engineering regulations in the USA.

In Alberta, Canada where I have practiced most of my life, any engineer can seal any drawing because our association (APEGGA) does not register by discipline. Needless to say, we are expected to perform only those services for which we are competent. Those who don't may find themselves facing a lawsuit, a disciplinary hearing or both.

Doing "freebies" for friends or relatives should be avoided unless you are prepared to accept full responsibility for the consequences. Even casual advice from you to the pilot over cocktails about the depth or size of his footing can get you in trouble if he acts on it without taking into account that the footing is sitting on five feet of uncompacted fill, a fact he omitted to mention to you.

By the same token, I avoid specific design requests on this or any other forum which ask for the required size of footings, columns, beams, joists or other members for a particular structure which the OP is building in an unknown location with unknown snow loads, wind loads and unknown seismic requirements. The OP is fishing for free engineering instead of retaining the professional help he needs.

Thanks Bruce, great advice.

As a R.P.E. Civil, I would have been comfortable certifying a very simple footer design, but not for my wife's friends or folks I meet over drinks!

I would never get involved in more complicated structural steel building design under any conditions as that would be out of my area of expertise (as you point out).

I did successfully change the subject for an hour or so, but this guy left that evening still convinced that he would find someone willing to play his game (up until about 10 years ago my state (MA) was very lax in this regard, but they have cracked down quite a bit recently looking particularly at work done out of discipline and also stamped without fully supervising the work of others not certified.

This Captain/Commercial Pilot/Contractor spent a lot of time blaming his mate for running into the rock while he attended to matters down below (in this 26 foot Sail/auxiliary vessel).

In presenting the "Broken Prop Award", he was asked why he did not keep watch on his crew knowing that this was his responsibility and one to be deferred to others.

I can just see him throwing the Structural Engineer under the bus when this building collapses!

Another interesting aspect to the puzzle regards the Construction Supervision issue. Hypothetically, suppose a valid design is prepared, certified, and approved, but then substantial changes are made during construction which result in a system failure? The Contractor may try to point to you as negligent or in error while you may be forced to defend the design as an undocumented field change.

It would seem that in such a case, you would have to be present to witness the work prior to backfill or in the case of reinforced concrete construction prior to concrete placement.

May get to be a very slippery slope from a liability standpoint.

But I digress.

Very good comments. Hopefully others will take heed!

If a valid design is modified on site and the modification results in system failure, the Engineer must be able to defend his design. The Contractor cannot show him to be negligent or in error unless he is. This can be proven conclusively when the cause of the problem is discovered.

It is best that construction be inspected by the Engineer prior to covering it up. Soil should be examined prior to pouring footings. Reinforcement should be inspected before placing concrete. There are times when this is not done because of conflicting schedules, but in these cases, it is wise for the Engineer to protect himself by asking the Contractor to provide photos of the uninspected work. It may not be an ideal solution, but it is better than nothing.

In my experience, most contractors are prepared to co-operate with the Engineer of Record in attaining a good job which everyone can be proud of. Those who are not should be dismissed immediately (not always easy but necessary).

I Second the Motion to cut a large retirement-sized CERTIFIED CHECK for him! hehehehe I'm terrible aren't I????? *GRINZ*

As always, a great answer. Damn it man, you must have lightning-fast typing fingers, as you are always beating me to the punch with your super quick postings! I don't stand a chance! LOL You and that great engineering Guru from Egypt!

GA from me on your 1st posting!

Keep up the great works (and answers)!!!!

Thanks, CaptMoosie. Don't know about lightning-fast anything at my age, but I am really looking forward to that retirement-sized certified check. Beats a GA anyday.

Have you been keeping up with the snow shoveling in your area?

Thanks ba for asking. We got snow storm #7 last night, but it didn't amount to much of any consequence. About 3 inches. Now we have about 3 feet on the ground. I still have to remove the remainder of snow and ice off of the solar PV panels and roof yet....at least 4 inches of ice atop 4 or so inches of snow. On top of it all is 2 feet of fresh snow! Unfortunately my 21 foot long snow rake won't reach the upper portions of the panels and roof ridge! more ACCKKKK ACCKKK! We're praying for a very quick thaw here shorty.There's no sign of the thermometer rising over 32F within the next week. Damn!

I'm getting tired of digging out of this White Chit frankly...too damn cold and no room to put it all! hehehehe Thank goodness we have snow plow services to get rid of the stuff out of the long long driveway, otherwise they'd probably find me frozen the snowbank sometime during the Spring thaw, Moose hair withstanding!

How the weather up your way. I just imagine the Winter Wonderland you folks have to endure, eh?! Please keep warm my friend, keep VERY warm! Spring is just 2 months away, ohhhhh myyyyyy!

As they say, the check is in the mail....just don't hold your breath waiting for it okay? Yeah, I've been stiffed by clients, friends and family too! Deadbeats all!

Have a great day.....now off to the Dentist appointment. Not a happy camper! Can you spell open your mouth pleeeeazzzeeee? hahahaha

CaptMoosie,

We have had fairly cold temperatures here for the most part but today is the third day of a three day warming trend according to our weather man. More snow than usual, but not as bad as S. Dakota. Take a look at the poor guy in the photo clearing his roof in Lead, S. Dak. My roof has between two and three feet of snow on it at the moment. It's melting today, but I understand it will be freezing again tomorrow and another flurry is expected.

We have had several roof collapses in our area reported in the paper. Reporters say they collapsed due to excessive amounts of snow. Could be, or perhaps something wrong with their design or construction. Maybe it would be wise to bump our roof design loading by 10 psf and at least avoid the collapses.

Lots of folk are clearing snow from their roofs, at least around the edge to minimize ice damming. My grandkids have offered to come over this weekend and clear mine, but I'm a bit leary...don't want them falling off the roof onto the driveway.

All the best.