Buried Metal Bridge Benefits

• Steel is the world’s most recycled material*
• Less energy is used in the production and shipping of Buried Steel Bridges than concrete bridges
• Buried Steel Bridges can be built in significantly less time, reducing disruption time and detours and expediting construction schedules
• Buried Steel Bridges require less maintenance than concrete beam bridges
• Zinc used in galvanizing is a naturally occurring material and is 100% recyclable**

*Reference: www.aisc.org
**Reference: https://galvanizeit.org/hot-dip-galvanizing/is-galvanizing-sustainable/hdg-environmental-advantages

• Eliminates recurring life cycle costs to maintain and repair bridge decks, expansion joints, bearings, girder fatigue, de-icing agent corrosion issues, concrete durability, fracture issues, approach slabs and freeze/thaw or wet/dry cycles
• No differential settlement “bridge bump” to maintain between decks and approach slabs
• Wider spans eliminate need for bridge piers that restrict hydraulic flow and trap debris
• Open-bottom shapes can offer longer design service life
• Design service life can exceed 75 years with protective coatings
• Structure length can be extended to accommodate future road widening; increased functional service life

• Allows roadway construction to extend subgrade materials directly over buried bridge elements
• Road section provides uniform driving lane and shoulder widths over buried bridges
• Pavement structure is continuous and seamless
• No bridge deck freezing issues
• No freeze/thaw differential with roadway approaches
• No need to narrow roadway at crossing

• Unmatched performance, especially in less-than-ideal foundation conditions
• Settlement tolerance is much higher than concrete structures or girder style bridges
• Little differential movement, settlement or frost heave between buried bridge and adjacent approach fills
• Headwalls and wingwalls offer more resiliency in flood events
• Geotextile Reinforced Soil (GRS) backfill technology also increases resiliency

• Usually no invert, resulting in a longer service life
• Minimal impact on streambeds and habitat
• Wide-span, open-bottom designs allow for natural streambeds with excellent open-flow hydraulic and fish passage properties
• Buried Metal Bridges will not leach harmful chemicals or compounds into the water or ground, which is often a concern with concrete structures

• Lightweight, nestable components are easy to ship anywhere
• Lower structure, foundation and installation costs compared to concrete structures and girder style bridges
• Can be constructed with local crews and equipment
• Owners with in-house resources can complete some or all of the construction
• Lighter-weight components eliminate need for larger capacity (or multiple) lifting devices
• Many applications can be built within accelerated construction timelines

• Approval drawings can be provided quickly
• Some structures can be delivered within days or weeks of order
• Many structures can be assembled in just a few days
• Staged construction can avoid full road closure

• Thicker steel and larger corrugation profiles with much higher design strength
• Product of choice for extreme loads, construction loads or repetitive overloads
• Also shielded from dynamic load effects (wind and vehicular)
• Wider spans, more applicable for bridge applications
• Handles larger hydraulic flows
• 50% thicker galvanizing, adding to service life

• The bridge structure and the backfill materials act together to support the loads
• Ideal backfill materials are often available on or near the site at a low cost
• If not, less-than-ideal backfill materials (including on-site materials) can often be considered
• Use of local backfill materials yields significant cost savings and smaller carbon footprint due to reduced trucking

With many thousands of installations worldwide over the last 50 years, Buried Metal Bridge design and analysis continues to evolve, as their behaviour is better understood. Collaborative efforts by many academics at prominent research facilities lead the way through advanced finite element modeling initiatives, which are validated by rigorous field and laboratory testing programs.

Since AIL first introduced our deep-corrugated structural plate solutions over 30 years ago, there has been growing global acceptance of this technology. Numerous countries have adapted their national bridge code standards and specifications to recognize and support large span Buried Metal Bridge design.

Canada
CSA S6:19, Canadian Highway Bridge Design Code, Section 7, Buried Structures CSA G-401, Corrugated Steel Pipe Products

USA
AASHTO LRFD Bridge Design Specifications, Ninth Edition, 2020 ASTM A761/A761M, A796/A796M

Australia and New Zealand
AS/NZS 2041.1, 2041.2, 2041.6

Sweden
TRITA-BKN Report 112, Design of Soil Steel Composite Bridges

This includes various structural plate product options, shapes, sizes and bevelled or skewed ends.

The more distance there is between the bottom of a structure and the road elevation above, the more cost-effective a buried bridge can be.

As an example, in the top illustration a 3 m (10′) wide stream with sloped embankments passing 6 m (20′) below the proposed road elevation might require a girder style bridge with a span of 30 m (100′) or more.

Alternatively, in the bottom illustration a 14 m (46′) span Buried Metal Bridge could achieve the site and hydraulic objectives with significant time and cost savings.