Light Truck Loading 2

[azogr]

Hi All,

I am estimating beam sizes for a mezzanine that will carry at a maximum light truck loading. I am having no luck finding in any of my references what the appropriate design loads and spacings would be for this type of loading. I can find box truck loading and the like but that is going to be much heavier than what will be present in this case. Can anyone help?

Thanks!

 

[msquared48]

Get the gross weight of the vehicle class fully loaded and the axle/wheel loads, and apply that to your structure. Make sure in the Structural Notres of the drawings that you stipulate diagramatically the vehicle load condition used in the design.

Mike McCann
MMC Engineering

 

[azogr]

Thanks for the quick response Mike! Doing a little internet research it appears the gross vehice weight for a 1 ton pickup seems to be in the 11,200 to 11,400 lb range. I think I am going to assume 12,000 just to be safe. I didn't have any luck finding what the weight distribution between the front and rear axle would be. I am thinking about just assuming 5/8 of the gvw on the rear axle and 1/2 of the gvw on the front and make the notes on the drawings like you suggested.

 

[racookpe1978]

You got a lot of other variables you haven't added yet = truck load, people on deck, forklifts, dynamic loads (starting, stopping, tipping, vibration from movement of the truck and cargo and people, acceleration of the truck.

Could anybody EVER "dump" a load of anything into the "truck"? That would give 4 to 8 times as an impact load.

"Idiot proof" it - because if ANYTHING is EVER going to be overloaded or setup by or driven by nitwits its a light truck in the vicinity of males doing a job.

The ONLY worse case is males with a POTENTIAL "heavy" truck goofing off,

 

[BAretired]

The NBC specifies a concentrated live load to be applied over an area of 750mm x 750mm (30" x 30"). The minimum specified load is 18kN (4050#) for vehicles not exceeding 3600 kg (7920#) gross weight and 36kN (8100#) for vehicles exceeding 3600 kg but not exceeding 9000 kg (19800#) gross weight.

BA

 

[racookpe1978]

By the way - don't "assume" that the (potential) idiots driving and parking the truck will always park it in the same place:

You need to assume that those 30x30 load points could be anywhere from curb to curb, front edge to back edge.

 

[Ron]

azogr...unloaded distribution for light truck is about 40/60 front to back. Loaded distribution is about 30/70 to 20/80 front to back.

Check GVW from both manufacturers and from traffic data from your state DOT....trucks with single dual wheels are often required to stop at scales on major roadways.

Keep in mind also, that light trucks are often loaded way beyond the GVW and recommended loading from the manufacturer. For instance, I worked for a company in college that would routinely load a "1-ton" truck with single axle dual wheels on the rear with a load of 15 to 18 kips, bringing the GVW to 25k or so. The trucks can handle the loads so they get loaded that way, depending on the cargo.

 

[azogr]

Good points everyone. The mezzanine deck is going to be in one of these package oil change shops. There will be two lanes through the mezzanine and one will have a vehicle pit in the center of the lane. In addition to the wheel point loads I was going to design for a 70 PSF live load which exceeds the 40 PSF specified in Table 1607.1 in IBC 2006. Any recommendation as to what factors to use for starting and stopping of the vehicles etc? The vehicles cannot be loaded or unloaded (other than with people) in the shop so that should not be a problem.

 

[Ron]

Braking at such slow speeds mostly changes the weight distribution. If you design for the worst weight distribution, plus a relatively small dynamic factor (10 to 15 percent) you should be in the ballpark.

Be sure to design the perimeter guardrails for impact (See AASHTO requirements).

 

[msquared48]

After being rear ended by a 3/4 ton pickup doing 55 some 33 years ago now, I personally don't think that there is any such thing as a "light" truck. Darn lucky I'm still here.

Mike McCann
MMC Engineering

 

[racookpe1978]

Good to hear you're working on a simple oil change platform - rather than (as I incorrectly thought) an elevated floor or loading area.

You'll have people pulling in - as pointed out above - "way above" fully loaded. I'd use the "fully loaded" criteria from above: "The NBC specifies a concentrated live load to be applied over an area of 750mm x 750mm (30" x 30"). The minimum specified load is 18kN (4050#) for vehicles not exceeding 3600 kg (7920#) gross weight and 36kN (8100#) for vehicles exceeding 3600 kg but not exceeding 9000 kg (19800#) gross weight."

But - your load is going to driven all the down and out over a small "channel type" load path. So both the front and back axles are going to almost oint" loads down the whole channel: each tire (assume 6x6 square loaded area) will take part of that (potential) 19800 lb load. (Even if you put a sign saying "Maximun load not to exceed 8100 lbs" - how many people will exceed it? How many will not know what they've got loaded in the small truck?)

So assume, for example, that you will get a 19800 lb total load, divided by 2 sides = 10,000 per side.

Your mezzanine will be better than this because the load is constrained to only the two drive paths where the truck will be: that will help your design. Assume you were to build each side with a single 10" channel lying sideways, so the truck is being driven down the channel and is being "guided" by the two webs of the channel. (Same would happen with a W10 member laid on its side.)

The 10000 lb total load will be spread out over the web of the member by the two tires on each side, and be resisted by the two flanges of the channel. (You won't really have a "point load" since the tire does spread out the weight over some 16 - 20 square inches.) But that load will move down the channel from end to end, so the relative weight distribution between front and rear axles means you can't assume 5000 on each axle either.

So your problem is "reduced" to resisting the highest rear axle load at the point where you have the longest distance between supports for the mezzanine track.