Construction Vehicle Axle Weights 1

[VAStrEngr]

Does anyone know the maximum gross axle weights for the following scenarios:

Fully Loaded Concrete Mix Truck
Unloaded Concrete Mix Truck
Flat Bed Trailer (hauling construction material)
Flat Bed Pickup

I am trying to determine the adequacy of an existing timber bridge to handle occasional construction vehicles so as to specify to the contractor what vehicles they may or may not use. The bridge will not need to carry traffic, only support construction activities beyond it for a short time period. Anyone with knowledge of these items is appreciated.

 

[Ron]

Check with several manufacturers and get curb weights and gross weights from them.

For concrete transit mixers, check with McNeilus, Oshkosh, and Terex.

For flat bed trailers, check with Great Dane, Fontaine, Strick or Wabash.

Consider maximum axle loadings such as H20, H22 configurations and check against manufacturer's info.

If you can only find curb weight on the transit mixer, add 40,000 lbs spread on the rear tandem to get total weight (10cy at 4000 lb/cy)

 

[cap4000]

Here are some typical cases.

Vehicle Load Table
NOTE: Maximum axle load or load class of vehicles are design limits.
Vehicle type Maximum weight axle, LB AASHTO Load Class
ATV (Trail Vehicle Only) 1,200 NA

Passenger Vehicle 3,000 H 10
Light Truck 3,000 H 10
Pickup 4,000 H 10
80 Hp Tractor 5,700 H 10
Service Vehicle 7,000 H 10
100 Hp Tractor 11,000 H 10
Van Delivery Truck 16,000 H 10

Rural Fire Truck 22,000 H 15
Large Delivery Truck 24,000 H 15
Semi Delivery Truck 24,000 H 15

Garbage Truck (single axle) 26,000 H 20/HS 20
Loaded Dump Truck 30,000 H 20/HS 20
Heavy Delivery Truck 32,000 H 20/HS 20
Heavy Semi Truck 32,000 H 20/HS 20

Standard Log Truck 33,600 H 25/HS 25
Concrete Transit Truck 38,000 H 25/HS 25
Garbage Truck 42,000 H 25/HS 25
Dump Truck 43,000 H 25/HS 25
Off Hwy. Log Truck 43,000 H 25/HS 25
Note:
Federal and state axle weight limits: single axle 20,000 lb; tandem axle 34,000 lb
Washington axle permitted overweight: single axle 21,500 lb; tandem axle 43,000 lb
H 10 is the smallest loading grade considered by the AASHTO classification.

 

[JStephen]

Watch dump trucks also, which can run considerably overloaded depending on the circumstances. I think the readymix trucks are more likely to be properly loaded. But I've seen 10-wheel bobtail dump trucks at 60,000 lbs.

 

[lsmfse]

Maybe this should be posted in the bridge forum? Cap4000, this is a nice summary. What about HL-93 loading?
VAStrEng, what type of timber bridge is this?

 

[VAStrEngr]

I considered putting it in the bridge forum but decided that the topic of the post was "axle weights" and not necessarily how to analyze the bridge itself...therefore decided the general section was most applicable.

The bridge is a small 12' span comprised of doubled 6x6 stringers supporting a deck of 6x6 timbers placed against one another. This was most likely designed and constructed by goverment maintenance personnel (no drawings and/or calculations could be found!).

All the information really helped...thanks everyone.

 

[lsmfse]

What is the spacing of the double 6x6 stringers? With only a 12' span, your worst case might be a tandem axle of a concrete truck. Shear is always a problem with timber bridges of this size.

 

[VAStrEngr]

lsmfse...thanks for the tip. I agree that the tandem axle load might be the worst case.

Using AASHTO double 25k @ 4'0 spacing exceeds the limits of the bridge. However, I am analyzing the structure to determine what we can allow accross...ie, if the contractor can't take a fully loaded concrete truck, what can he take?

I think in the end, I am going to specific a "Maximum allowable axle load (GAWR)" and have the contract submit a plan with what he anticipates needing to cross over the bridge. There isn't that much concrete on the job so his maximum load might be a small crawler crane or other vehicle.

All of this depends on what the owner is willing/not willing to do to beef up the structure. I am considering an option of a total replacement or using slightly elevated steel stringers to span above the bridge...or as a cheaper but less effective alternative adding stitch plates to the sides of the double 6x6 members to increase their capacity.