Timber Bridge Spanning Solutions

How to design with timber & glulaminated beams?


Timber Bridge Spanning Solutions

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Repetitive Span

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Short Span

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Free Span

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Multiple Span

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Multiple Long Span

Creative Scoping, Design, & Development

When evaluating a crossing environment, it’s important to know that, there are a wide variety of spanning solutions available that can pair precisely with the unique conditions of each crossing. When working with Timber Bridges there are five categories of spanning solutions including: Repetitive Span, Short Span, Free Span, Multiple Span, and Multiple Long Span, we’ll explain these in greater detail later. The selection of the right spanning solution is based on the crossing conditions, which due to the vast amount of potential conditions that could call for a timber bridge, is harder to categorize; however, we never shy away from a challenge. The most common conditions of a crossing that influence spanning solutions include environmental buffers, topographic site characteristics, limits of work or impacts, jurisdictional allowances, property easements, flood event conditions, and waterway/waterbody extents. So, first and foremost, the most helpful piece of information in assessing a crossing environment is something that illustrates the conditions calling for a bridge. What does that even mean? It means we’ve worked from pictures, surveys, grading plans, GIS maps, hand sketches, and more. In short, the more information you can give the better but, if you only have a picture and a dream, well we can work with that. So now you’re versed in the basics, let’s get to the defining details.

Repetitive Span


A series of bridge spans built on equally spaced pile bent foundations. Typically measuring +/- 10’ for Pedestrian Bridges and +/- 15’ for Vehicular Bridges, however, the span dimensions will ultimately be determined by the design & engineering requirements for the proposed bridge live load (i.e. who and what will be using it). In addition, you’ll find that repetitive span bridges are designed with standard dimensional lumber or rough sawn timbers.

Span Type
Benefits
Ideal Uses
CAD Files
Project Links

Repetitive Span

  • Cost Effective
  • Fluid for Curving and Rolling Bridges
  • Low Impact Construction
  • Culvert Alternatives
  • Limited Access Sites
  • Over Water Applications
  • Environmentally Sensitive Areas
Repetitive Span Vehicular Bridge

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Repetitive Span Vehicular Canal / Inlet Crossing

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Repetitive Span Pedestrian Bridge

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Repetitive Span Pedestrian Wetlands Crossing

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Short Span


A single bridge span built with rough sawn timber between two abutment foundations. The term ‘short’ is in reference to the timber stringer structure which limits lengths to 26’ or less.

Span Type
Benefits
Ideal Uses
CAD Files
Project Links

Short Span

  • Cost Effective
  • Low Impact Construction
  • Culvert Alternatives
  • Limited Access Sites
  • Environmentally Sensitive Areas
Short Span Vehicular Bridge

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Short Span Vehicular Wetlands Crossing

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Short Span Pedestrian Bridge

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Short Span Pedestrian River / Stream Crossing

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Free Span


A single bridge span built with Glue Laminated Timber between two abutment foundations. Due to the use of Glue Laminated Timber for the structural bridge stringers, single spans are able to stretch up to 100 linear feet with greater lengths reviewed on a case by case basis. The most economical length would be around 80 linear feet. The term “Free” is in reference to the large clearance that can be achieved between abutment foundations. Typically, a Free Span is selected for lengths greater than 26’ that require or are best without any impacts within the crossing environment. Although Free Spans have been used for shorter spans that would benefit from the aesthetic or strength that Glued Laminated Timbers inherently provide.

Span Type
Benefits
Ideal Uses
CAD Files
Project Links

Short Span

  • Cost Competitive
  • Fluid for Rolling Profiles
  • Customized Material
  • Low Impact Construction
  • Concrete Span Alternatives
  • Culvert Alternatives
  • Deep Crossing Environments
  • Environmentally Sensitive Areas
Free Span Vehicular Bridge

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Free Span Vehicular River / Stream Crossing

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Free Span Pedestrian Bridge

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Free Span Pedestrian Canal Crossing

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Multiple Span


The standard multiple span uses one longer free span section, usually over the main water channel, with shorter, repetitive span approaches. A single bridge can include many variations like repetitive span, short span, and free span sections to achieve the best-case scenario for the client, use, and environment. A Multiple Span bridge can utilize dimensional lumber, dimensional heavy timber, and Glued Laminated Timber, as it pertains to the designed spans. One of the most common uses for a Multiple Span bridge is to reduce the overall length of a Free Span to facilitate the required clear and utilize Repetitive Span approaches for the remainder of the length, providing feasibility in construction techniques and client budget.

Span Type
Benefits
Ideal Uses
CAD Files
Project Links

Multiple Span

  • Cost Competitive
  • Fluid for Rolling Profiles
  • Customized Material
  • Low Impact Construction
  • Concrete Span Alternatives
  • Culvert Alternatives
  • Deep Crossing Environments
  • Environmentally Sensitive Areas
  • Limited Access Sites
  • Over Water Applications
Multiple Span Vehicular Bridge

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Multiple Span Vehicular Designed Environment Crossing

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Multiple Span Pedestrian Bridge

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Multiple Span Pedestrian Sensitive Environment Crossing

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Multiple Long Span


A series of bridge spans built with Glue Laminated Timber on varying or evenly spaced pile bent foundations between abutments, to include a combination of spans commonly defined as free spans that are customized to the crossing environment. Typically, a Multiple Long Span is selected for a crossing requiring more than one span with lengths greater than 26’ without need or accommodation for short spans or repetitive spans approaches. Most commonly, Multiple Long Spans have been used for crossing environments with increased heights and/or lengths, to reduce piling bent foundations and maintain a cohesive profile without the demands of a long free span or the rigor of a multiple span.

Span Type
Benefits
Ideal Uses
CAD Files
Project Links

Multiple Span

  • Cost Competitive
  • Fluid for Rolling Profiles
  • Customized Material
  • Low Impact Construction
  • Concrete Span Alternatives
  • Culvert Alternatives
  • Deep Crossing Environments
  • Environmentally Sensitive Areas
Multiple Long Span Vehicular Bridge

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Multiple Long Span Vehicular Sensitive Environment Crossing

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Multiple Long Span Pedestrian Bridge

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Multiple Long Span Pedestrian Designed Environment Crossing

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Capablities & Design-Build Process

Bridge
Applications

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Crossing
Environments

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Spanning
Solutions

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Bridge Uses &
Capacities

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Decero™ Design
Process

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Timber Bridge
Materials

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On-Site
Construction

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Protection &
Maintenance

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