2nd story car showroom design question 1

[southard2]

I have an upcoming project where the second floor will be used to store cars. It is not a parking garage in the sense that cars will be coming and going daily. It will be covered with a roof and enclosed with CMU walls. Think of it as a second story car showroom. I plan on asking what the heaviest vehicle to be stored up there will be but for now lets assume average passenger cars.

ASCE 7-02 states that the minimum live loads are 40 psf or a 3000lb point load over a 4.5 in x 4.5 in area. 40 psf seems light in comparison to other typical floor live loads. The commentary seeks to explain this by stating that load variation is very small in parking garages versus buildings. Still even with live load reductions most building areas would be designed for more load than this.

I plan on taking the heaviest car and dividing by its area to make sure the 40 psf load is adequate. I will also probably go ahead and design for a live load of 100 psf since the minimum corridor load is 100 psf. Doesn't make much sense to design corridors for more load than a floor holding up cars. I doubt the cars will be packed in close together since it will be used for private use. Also since this space may be used for something else in the future (many owners will assume it can take a lot since it was used for cars) I think 80 to 100 psf may be appropriate.

I'm thinking of using either composite steel beams or LH series steel joist with a heavy concrete poured form deck. I won't be using a composite deck since I'm worried about the effect the concentrated wheel loads might have on the interlocking action over time. I'm a bit concerned since most parking garages use concrete exclusively. My thought however is that if the concrete deck can handle the load concentration then steel beams and CMU walls should be fine. Of course the joist or beams must also be capable of handeling the concentrated loads as well.

Does anyone have anything else to add or am I pretty much on the right track here? Is there anything else I should consider in my design?

Any help from you parking garage engineers will be much appreciated.

Thanks,

John

 

[Teguci]

For vehicle loading, the 40 psf is almost always adequate. You'd have to pack a hummer side by side and end to end to exceed this load capacity.

However, I wouldn't consider your show room as a parking deck. Parking decks have almost no pedestrian loading per square foot. In this case, I think your looking at more of an upper floor retail store at 75 psf.

Exclusive concrete floor systems are best for parking decks in winter areas due to road salts and leaking causing corrosion to exposed steel. In a show room, this will be minimized and I think you can get away with steel joists.

A 4" thick concrete deck is more than adequate for your floor loading. The 3,000 lb point force is there to simulate someone jacking up a car to replace a tire (used to be 2,000 lbs). Fire rating may be another consideration though.

Another thing to consider is your barrier wall. Do you need to consider vehicle impact? If you do, you will need to resist a 6,000 lb force at 18" above the floor (vehicle wall height should be at least 24" to avoid jumping - still need pedestrian barrier, 42" total as well). This will impact your masonry wall design.

Not sure, but you will probably need to sprinkler the space too.

 

[Dinosaur]

I think you are wise to recognize the building may have another future use. If you have too much trouble, you could get in writing what the owner wants for the design loads after you explain the issue to him. If you have the load in writing and it meets the 40psf ASCE guideline, then you don't have to worry about future use.

 

[DTS419]

When in doubt, make it stout.

A colleague of mine used to be the city engineer of a leading Big 10 college town. A fraternity wanted to rent a parking garage from the city to have a ball one night, and they had to deny the application because the building that people drive their cars in couldn't handle a pedestrian floor load. How embarassing.

 

[csd72]

Teguci has touched on all the points that I would have made.

Use the 75psf.

 

[slickdeals]

In case you are interested in reading about SUV's and their weights on a parking garage, read the following article

 

[slickdeals]

sorry, here is the article

 

[civilperson]

Japan has a phenomena of double and triple stacking cars with small steel hydraulic frames. If the ceiling height allows, I would design for 120 psf live load.

 

[csd72]

civilperson,

They are called car stackers, and the designer would definately need to know about them first. I wouldnt design for these unless specifically mentioned by the client.

These are used in many carparks around New York City and probably in some buildings as well. I designed a couple of units (condominiums) in Australia that used triple stackers due to the limited basement area available.

The loads exerted by these are far from uniform (some cantilever from the back end).

 

[dinjin]

I plan on taking the heaviest car and dividing by its area to make sure the 40 psf load is adequate. I will also probably go ahead and design for a live load of 100 psf since the minimum corridor load is 100 psf. Doesn't make much sense to design corridors for more load than a floor holding up cars. I doubt the cars will be packed in close together since it will be used for private use. Also since this space may be used for something else in the future (many owners will assume it can take a lot since it was used for cars) I think 80 to 100 psf may be appropriate.

I think you would want to divide only by the 4 tire area
in contact with the floor.

 

[southard2]

Much thanks to everyone who responded to this post. I appreciate the ideas and interpretations very much. I feel more confident about the loading situation and requirements now.

thanks again,


John

 

[tngolfer]

As Dinosaur mentioned, you should get a letter from the owner prior to designing for 2x (or more) the load recommended in the building code. I think the 40 psf unreducible is a little on the low side even though it is in the building code. Also, I have heard the next IBC might be going to 50 psf unreducible. Not sure if this will happen or not but it might not hurt to look into this if you want some more "evidence" to present to the owner to design for a higher load.

I think it is crazy to design for a 100 psf or 125 psf uniform load. If the owner starts stacking cars, you need to get a cut sheet from the stacking manufacturer because the loads will not be uniform.

The 100 psf uniform load for corridors is an egress requirement. The likely hood of a corridor seeing it's full load is much higher than the room it is serving. I don't agree with designing the whole floor for 100 psf. You may want to check with the owner though to see if there is even a slight chance of the area being used for something other than parking.

 

[hokie66]

The excellent paper referenced above by slickdeals recommends using 50 psf uniform loading. I know it is not applicable to you, but the Australia / New Zealand code requires 2.5 kPa (about 50 psf) for light vehicles (not exceeding 2500 kg gross mass), and 5.0 kPa (about 100 psf) for medium vehicles (2500 to 10000 kg gross mass).

 

[Teguci]

I would recommend reading Mary and Tony's (RIP) article again. It is highly unlikely that a shownroom is going to have a pickup truck loaded to its gross vehicle weight on display. Even more unlikely is that all of the space will be jammed with the heaviest vehicle. If you design this space as a parking deck, stick to the code specified 40 psf.

As noted before, I do not think this should be considered a parking deck. This is a retail space with a couple of cars on display. To that end, I recommend using the 75 psf live load for the floor design.

If you want the best help available, call Mary Smith (author of the article) at Walker Parking.