Type of Vehicular Loading on Parking Garagae Slab

[ali07]

Hi Guys,
We have designed 1-story concrete parking garage slab (Exposed condition)for live load of 250 psf (normal vehicular load) and 400 psf (fire route).

Appreciate if someone helps regarding type of vehicles to allow for 250psf and 400psf. As client need to know whether snowremoval machinery, what type of dump trucks can pass over, trailer etc.

If somebody can help differentiating the vehicles to allow based on types and axle loading to pass for 250 psf and 400 psf.

 

[hokie66]

It seems to me that if you have designed the floor for those heavy loads, you must have used some type of vehicles to determine the design loads. I think anything which would be allowed on a highway bridge would be allowed on the 400 psf section. The 250 psf section may not take a fully loaded water truck or dump truck, but that would depend on the truck configuration.

 

[NS4U]

It really depends on the wheels, loads, layout of the structural system, etc...

very generally speaking, 250 psf is approximately equivalent to the HS-20 truck on highway bridges. But, the psf load is highly dependent on the bridge span length.

Is the structure too complex that adding some point loads and at reasonable wheel and axle spacings in such a location as to produce maximum moment and shear is too difficult to analyze by hand using approximate methods? Or too time consuming to do via PC?

Unfortunately there is no easy answer to your question because of the variables.

 

[civilperson]

All types of vehicles can safely pass the loadings specified. Most bridge decks are less than 100 psf.

 

[hokie66]

I don't think so. I think NS4U is closer to correct.

 

[ali07]

It is a flat slab system with drop panels and column capitals with max. span upto 36ft.

How about if we allowed HS20 and restrict other heavier trucks/trailers on the same route of 250 psf is somewhat looks diffult to operate.

 

[msquared48]

The 1963 Bridge Design Manual, and I realize ythat I am dating myself here, specifies a "Lane Load" of 300 psf that controls the design of some bridge components in most situations (HS20 Truck). However, there are other axle configurations that can produce maximum negative and positive moments, such as a triple axle loading, or a vactor truck that can locally generate a 750 psf bearing condition over a 70 square foot area, both exceeding the results of the Lane Load.

I believe that under the currrent AASHTO code, that figure of 300 psf has been lowered though, possibly to 250 psf.

Mike McCann
MMC Engineering

 

[ali07]

So in general when you guys design for example for 250 psf, do you restrict with a barriers for trucks, fire trucks.

As we have isolated the fire route area in our drawings for 400psf. But 250psf outline need to be differentiated for lighter loads compared to 400psf.