Timber Bridge
Load Capacities & Uses

What uses do timber bridges support?

Timber Bridge Uses & Load Capacities

Our timber bridges can be designed and built for any capacity and use.

Timber bridges are great for both vehicular and pedestrian use. The majority of the vehicular bridges we’ve built are designed to general highway standards for traffic including semi-trucks, which does tend to surprise people. In addition, all vehicular bridges can be designed specifically to meet the needs of heavier loads, the options are far and wide, just ask! As for the pedestrian bridges we’ve built everything from nature’s best boardwalks to luxury waterfront amenities to soaring free spans, each designed to the national standards for safety. Like our vehicular bridges, our pedestrian bridges can also be designed to accommodate greater crowds, enhanced loading for occasional use by vehicles, or the most common request is to allow for golf cart use. So, if you have a use in mind, we’ve got a capacity to match. These are some definitions, diagrams, and even charts to help you define the right bridge for your needs.

webinar

"I didn't know a wooden bridge could do that!"

Most people don’t know about road ratings or loading capacities - we get that. Lots of people underestimate timber bridges - we know that. So to save you a challenging web search, time, and maybe even some money, we made this webinar for you! This session will outline both vehicular and pedestrian uses that timber bridges are great for AND give you access to guideline resources on how you can determine what capacity might be necessary for your next project. From accommodating highway standards to some supersized requests for powerline companies, mining facilities, and construction equipment, we’ve got projects that’ll make you say, “I didn’t know a timber bridge could do THAT.”

Vehicular Use

Standard Vehicular Loading Diagrams

This category is based on regular usage of the bridge by vehicles up to a semi-tractor-trailer. The most common loading capacity for Standard Vehicular Use is the HS20 Truck Loading. They are typically utilized for private and public roadways. Ultimately, a loading capacity is determined by largest vehicle for anticipated regular use, for example an HS20 supports a typical semi-tractor-trailer weighing 72,000 lbs. To see more about HS Truck Loadings for maximum weights and weight distribution see the associated loading diagrams and charts.

Load capacity

Axle Quantity

Axle Spread

Gross Vehicular Weight (GVW)

Per Axle Loading

HS20

3 Axles

Min 14' Axle Spread, 14' to 30' Variable Axle Spread

72k lbs / 36 Tons

8k lbs - 32k lbs - 32k lbs

HL93

3 Axles

Min 14' Axle Spread, 14' to 30' Variable Axle Spread

72k lbs / 36 Tons + 640 lbs per linear foot of uniform loading

8k lbs - 32k lbs - 32k lbs + 640 lbs per linear foot of uniform loading

HL93

HS20

Lightweight Vehicular Loading Diagrams

This category is based on regular usage of the bridge by vehicles up to a large pick-up truck or SUV. The most common loading capacities for Lightweight Vehicular Use bridges are the H5 & H10 Truck Loadings. They are typically utilized for driveways, trails, private access roads, maintenance paths, or similar. Ultimately, a loading capacity is determined by largest vehicle for anticipated regular use, for example an H10 would be used when Emergency Access for an Ambulance or similar is required. To see more about H Truck Loadings for maximum weights and weight distribution see the associated loading diagrams and charts.

Load capacity

Axle Quantity

Axle Spread

Gross Vehicular Weight (GVW)

Per Axle Loading

H5

2 Axles

Min 14' Axle Spread

10k lbs / 5 Tons

2 kips (2k.lbs) - 8 kips (8k.lbs)

H10

2 Axles

Min 14' Axle Spread

20k lbs / 10 Tons

4 kips (4k.lbs) -
16 kips (16k.lbs)

H10

H5

Section Views

Double Lane w/ 2 Walkways

Double lane vehicular timber bridge concept with pedestrian and and golf cart throughways

Double Lane w/ Walkway

Double Lane

Single Lane w/ Walkway

Single Lane

Heavy Weight Equipment & Large Specialty Vehicle Use

This category is based on regular usage of the bridge by a unique vehicle with special loading considerations, that is atypical of all commonly defined truck loading capacities. A custom truck loading capacity can be designated to support the maximum gross vehicular weight and weight distribution of most oversized or unique truck loads. Pictured below are examples of vehicles that we used to custom design timber bridges.

Custom capacity

Axle Quantity

Axle Spread

Gross Vehicular Weight (GVW)

Per Axle Loading

70 Ton GVW

3-4 Axles

N/A

140k lbs / 70 Tons

81,831 lbs (Steer Axle & Tandem Axle, lbs/wheel undefined) - 51,123 lbs (Tandem Axle 25,561.5 lbs/wheel)

Volvo A25F Articulated Load

2 Axles

16.44'

101,192.2 lbs

32,077.3 lbs - 69,115 lbs (Tandem Axle 34,557.5 lbs/wheel)

Low Boy Crane Transport

5 Axles

Min 14' Axle Spread; 14' to 26'7" Variable Axle Spread; 4.5' - 5' Variable Tridem Axle Spread

248,000 lbs

18k lbs - (4) 57.6k combined lbs per axle (Tridem Axles 19,200 lbs/wheel)

Crane Transport

3 Axles

Min 16' Axle Spread; 16' to 31'4" Variable Axle Spread; 4.5' - 5' Variable Tridem Axle Spread

15,500 lbs - (2) 63,750 combined lbs per axle (Tridem Axles 21,250 lbs/wheel)

18k lbs - (4) 57.6k combined lbs per axle (Tridem Axles 19,200 lbs/wheel)

Pedestrian Use

Light Vehicular / Pedestrian

This category is based on a bridge that requires regular usage by a 6-person golf cart or utility terrain vehicle up to a small pick-up truck.

Load capacity

Axle Quantity

Per Axle Loading

Axle Spread

5 Ton GVW

2 Axles

5 kips (5k lbs) - 5 kips (5k lbs)

Min 7' Axle Spread

2 Ton GVW

2 Axles

2 kips (2k lbs) - 2 kips (2k lbs)

Min 7' Axle Spread

5-Ton GVW

2-Ton GVW

Section View

Pedestrian

A pedestrian bridge is used to support the live load of one or more people. The 90 PSF loading capacity is based on regular usage of the bridge by pedestrians and cyclists. The 100 PSF loading capacity is based on regular usage of the bridge by pedestrians, cyclists, and event crowds. Sister loading can be utilized for occasional or emergency use. This could include occasional bridge use by golf carts, maintenance equipment, or vehicles. Ultimately, the additional or sister loading capacity is determined by largest vehicle for anticipated use as a secondary loading. The most common complementary loading capacity includes the 2-ton or 5-ton GVW and the vehicular H5 or H10 loading capacities.

100 PSF

90 PSF

Section View

Pedestrian timber bridge concept 100 PSF and 90 PSF

Heavy Weight Equipment & Large Specialty Vehicle Use

This category is based on regular usage of the bridge by a unique vehicle with special loading considerations, that is atypical of all commonly defined truck loading capacities. A custom truck loading capacity can be designated to support the maximum gross vehicular weight and weight distribution of most oversized or unique truck loads. Pictured below are examples of vehicles that we used to custom design timber bridges.

Custom capacity

Axle Quantity

Axle Spread

Gross Vehicular Weight (GVW)

Per Axle Loading

70 Ton GVW

3-4 Axles

N/A

140k lbs / 70 Tons

81,831 lbs (Steer Axle & Tandem Axle, lbs/wheel undefined) - 51,123 lbs (Tandem Axle 25,561.5 lbs/wheel)

Volvo A25F Articulated Load

2 Axles

16.44'

101,192.2 lbs

32,077.3 lbs - 69,115 lbs (Tandem Axle 34,557.5 lbs/wheel)

Low Boy Crane Transport

5 Axles

Min 14' Axle Spread; 14' to 26'7" Variable Axle Spread; 4.5' - 5' Variable Tridem Axle Spread

248,000 lbs

18k lbs - (4) 57.6k combined lbs per axle (Tridem Axles 19,200 lbs/wheel)

Crane Transport

3 Axles

Min 16' Axle Spread; 16' to 31'4" Variable Axle Spread; 4.5' - 5' Variable Tridem Axle Spread

15,500 lbs - (2) 63,750 combined lbs per axle (Tridem Axles 21,250 lbs/wheel)

18k lbs - (4) 57.6k combined lbs per axle (Tridem Axles 19,200 lbs/wheel)

General Terminology Definitions

Vehicular Bridge Use

Vehicular Bridge Loading Capacity

Vehicular Bridge Occasional Use Loading Capacity

Single Lane Vehicular Bridge

Double Lane Vehicular Bridge

A Vehicular Bridge designed for a double vehicular width, the most common inside clear is between 22 feet and 26 feet in width between curbs. In addition, a double lane vehicular bridge may require greater clear widths around 32 feet to accommodate common design elements like vehicular shoulders, merging lanes, horizontal curvature, bike lanes, stormwater management, or other site-specific demands.

Vehicular Bridge Section