×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Gas station Canopy Footing
2

Gas station Canopy Footing

Gas station Canopy Footing

(OP)
Hi,
The gas station canopy is 102'x30' and supported by 4 HSS columns. I am designing only the footing and making sure it is sized for a moment as well as axial load provided by canopy manufacturer. Below the canopy is a slab on grade. The bottom of each of the four footings will be 4'-0" below the finished grade. There is also a slab on grade for cars and trucks to drive up to fill up. Do I need to take into consideration any impact for loads from these vehicles onto my column footings?

RE: Gas station Canopy Footing

Yes.

RE: Gas station Canopy Footing

No.

RE: Gas station Canopy Footing

Definitely no.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Gas station Canopy Footing

If the bottom of the footing was only at 2 feet down, I would say yes, but not at 4 feet.  Any impact force will be too dissipated at that depth to worry about.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Gas station Canopy Footing

(OP)
frv - Can you please elaborate?   

RE: Gas station Canopy Footing

question is a little unclear - do you really mean "impact loads" as in dynamic loading, or do you mean "impact from"  static or slow moving vehicle live loads?

 

RE: Gas station Canopy Footing

The latter cvg.  Moving vehicle impact loading - at 10 mph or less.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Gas station Canopy Footing

(OP)
The latter is the correct answer.  When cars/trucks pull up to fill up its usually slow speed.  Or worst case when the oil tanker drives by to fill up the underground tank.  Do I need to include the load of these vehicle on the footings for these columns that support the canopy?

RE: Gas station Canopy Footing

I would use a vehicle surcharge of 50 psf for passenger cars and trucks.   

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Gas station Canopy Footing

For vertical loading on the column footing, you should consider a surcharge load.  
Any impact load from a vehicle actually running into the column is usually not a problem as curved bollards are usually installed around the gas pumps and columns.  

RE: Gas station Canopy Footing

Also, be careful to include the surcharge in proper combinations as it can both help/hurt your overturning calc's.
Sorry if I am stating the obvious.  

RE: Gas station Canopy Footing

Not sure if it would be relevant in this case but if you were to check the foundations presumably with the slab cast around them you may be able to distribute any lateral load over several foundations.

RE: Gas station Canopy Footing

ToadJones is correct about curved bollards protecting gas pumps.  I know--my 18 year old daughter drove her older sister's car into one a few weeks ago.

I have spent the last couple of weekends doing auto body repair work curse

DaveAtkins

RE: Gas station Canopy Footing

Dave-
Better than hitting the gas pump!!!

RE: Gas station Canopy Footing

Funny picture!

Not funny for the owner of the SUV, of course.

DaveAtkins

RE: Gas station Canopy Footing

No.  Provide separate bollards for pump/column protection.

RE: Gas station Canopy Footing

Why wouldn't you design it for the impact of a vehicle?

It really isn't that stringent. I don't have the IBC in front of me, but it's something like 2 or 3 kips at 2'-3' above finished grade.

This loading is intended to account for a vehicle accidentally backing into it. And this is certainly a possibility.

Now, if you have the bollards as others have suggested, then you wouldn't need to design for the impact, as the bollards would absorb this.

RE: Gas station Canopy Footing

I think the issue is being confused here....I do believe the OP was worried about surcharge on the footing, NOT inmpact on the column. This might be semantics.  

RE: Gas station Canopy Footing

TJ...you might be right...I didn't read it that way, but makes sense.  In any case, the traffic loading is likely not going to be directly over the footings and most would be dissipated by the slab and the distance between them.  In short, I would not consider a traffic load on the footing, either.

RE: Gas station Canopy Footing

(OP)
Thanks guys!  I am only designing the 4 footings. The columns and superstructure are designed by the canopy manufacturer who didn't take into account an impact load but the columns are HSS 15x6 or something big like that.  My area of expertise is buildings not these small structures and my experience says those columns are good.  As for spread foundation, I think I will take into account an addition 50 psf.  My footing is already large due to moment so I don't think I will need to resize it by much more.  I really appreciate your input.  This is my first time posting here.  And I am impressed.  I don't usually get this much feedback even at work.   

RE: Gas station Canopy Footing

Although you didn't ask about it, remember to check against wind uplift.

LonnieP

RE: Gas station Canopy Footing

as I alluded to before, and Lonnie has pointed out, do not include surcharge in all cases, such as uplift.
Again, I am probably just stating the obvious.  

RE: Gas station Canopy Footing

(OP)
wind uplift - check
traffic surcharge to check for downward pressure - check
Thanks so much for all your input.  
love this forum.
nadia

 

RE: Gas station Canopy Footing

Regardless of whether the columns are protected by bollards, I would design the footing only for gravity loads from the roof and wind uplift loading.  Traffic surcharge and impact would be incidental and would have little effect on a footing founded 4' below the surface.  If the footing were at a higher level, I might consider the impact as a momentary overturning moment.  But if something hit a column hard enough to displace the footing, the whole thing would have to be rebuilt anyway.

RE: Gas station Canopy Footing

Oh, and of course there is lateral load from the wind also, the moment from which would doubtless exceed the impact moment.

RE: Gas station Canopy Footing

hokie66...exactly

RE: Gas station Canopy Footing

That's a good point, hokie..  

I guess it's just a check I've been accustomed to do whenever I have anything exposed to vehicular impact..  but I think you're right..  In this particular case, it's quite obvious by observation that wind loading would control both overturning moment and probably shear on the footing..

So on second thought, I change my answer to "No."

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources