how much can a timber bridge support?

Understanding the load capacities & uses of timber bridges

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Load capacities are one of the most important factors when it comes to building any type of bridge. However, we are here to dispel the myths that timber bridges aren't as strong as alternative building materials. Here are the crucial considerations when it comes to planning your next crossing.

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 use 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.”

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 the 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

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


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HS 20 Loading Diagram

Visual loading diagram for HS20

Download HS20 Loading Diagram
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HL 93 Loading Diagram

Visual loading diagram for HL93

Download HL93 Loading Diagram

custom Loading Timber Built Vehicular Bridges


  • Load capacities for vehicular bridges are determined based on the types of vehicles they are designed to support. This includes considerations for standard passenger vehicles, trucks, buses, and other specialized vehicles.

  • The load capacity is typically specified in terms of the maximum allowable weight that the bridge can safely support. This includes both static and dynamic loads.

  • Factors such as traffic volume, vehicle types, and the intended use of the bridge play a significant role in determining the appropriate load capacity.


contact us for custom load capacities

Light Vehicular & Pedestrian Loading Diagrams

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

axle spread

per axle loading


5 Ton GVW

2 axles

Min 7' Axle Spread

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

2 Ton GVW

2 axles

Min 7' Axle Spread

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


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5-Ton GVW Diagram

Visual loading diagram for HS20

Download 5-Ton GVW Diagram
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2-Ton GVW Diagram

Visual loading diagram for HL93

Download 2-Ton GVW Diagram
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Section View

Visual loading diagram for HL93

Download Section View

Timber Bridge Loading Factors


  • Load capacities for vehicular bridges are determined based on the types of vehicles they are designed to support. This includes considerations for standard passenger vehicles, trucks, buses, and other specialized vehicles.

  • The load capacity is typically specified in terms of the maximum allowable weight that the bridge can safely support. This includes both static and dynamic loads.

  • Factors such as traffic volume, vehicle types, and the intended use of the bridge play a significant role in determining the appropriate load capacity.


talk to an expert

Pedestrian & Boardwalk Loading Diagrams

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 the 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.
 
 
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100 PSF Pedestrian

Visual loading diagram for 100 PSF

Download 5-Ton GVW Diagram
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90 PSF Pedestrian

Visual loading diagram for 90 PSF

Download 2-Ton GVW Diagram
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Section View

Visual loading diagram for HL93

Download Section View

Safety & Regulation Factors


  • In both vehicular and timber bridges, safety factors are incorporated into the design to ensure that the bridge can handle loads well beyond the expected maximum. This provides an additional margin of safety to account for uncertainties and variations in actual usage.

  • Load capacities are subject to engineering standards, regulations, and building codes. Engineers must adhere to these guidelines to ensure that bridges meet safety and performance criteria.


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Section Views


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Double Lane + Two attached pedestrians

Visual loading diagram for a Double Lane Vehicular with two attached pedestrian sections

Download This Section View
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Double Lane + Walkway

Visual loading diagram for a Double Lane Vehicular with a single attached pedestrian section

Download This Section View
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Double Lane Vehicular

Visual loading diagram for Double Lane Vehicular timber bridge

Download This Section View
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Single Lane + attached pedestrian

Visual loading diagram for a Double Lane Vehicular with two attached pedestrian sections

Download This Section View
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Single Lane Vehicular Bridge

Visual loading diagram for a Double Lane Vehicular with a single attached pedestrian section

Download This Section View

Looking for a custom solution specific to Your Project needs?


As a Timber Bridge Builder with 40 years of experience, York Bridge Concepts has extensive knowledge of how to design and construct timber bridges with optimal load capacities, taking into account the specific requirements of each project.

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