New Design – Standard SL and SLW bridge requirements

Site requirements

• bridge skew is 40 degrees or less
• clear roadway width is between 8720 and 14820 mm (Commentary 1)

Superstructure requirements

• limited to Performance Level 2 (PL-2) bridgerail (Commentary 2)
• bridge span lengths are 8, 10, 12, 14, 16, 18 or 20 m (Commentary 3)
• overall bridge length is less than or equal to 60 m (centreline to centreline of abutments) (Commentary 4)

Substructure requirements

• abutment height is less than 600 mm (Commentary 5)
• pier height is than 6000 mm (Commentary 6)
• test hole, hydrotechnical, and other site specific information must satisfy the requirements of the standard design (Commentary 7)

Other considerations that should be taken into account when using Standard SL and SLW Bridges include the following:

• standard SL and SLW girders are designed for the CL800 vehicle loading
• use of Standard SL Bridge requires accessibility to concrete batching plant for cast-in-place concrete components
• concrete-to-grade decks may be used in situations where de-icing salts will not be applied

Commentaries

1 – Standard SL/SLW Bridge Requirements – Clear Roadway

Section 5.4.1 of the AT Roadside Design Guide requires a minimum bridge width of 9.0 m on new structures based on a minimum shy line offset of 1.0 m on each side. The closest clear roadway width for bridges incorporating SL or SLW girders is 8.72 m for 8 girder lines. With 3.5 m lanes this leaves a shy offset of 0.86 m and is therefore not considered equivalent to the 9.0 m minimum clear roadway criteria. However, eliminating this option would result in an effective minimum bridge width of almost 10.0 m for this type of structure. Therefore, for Standard SL/SLW Bridges, it is recommended that the 8.72 m clear roadway be considered applicable under the following circumstances:

For more detailed information refer to Alberta Transportation Best Practice Guideline 10.

2 – Standard SL/SLW Bridge Requirements – Barrier Performance Level

Section 5.4.1 of the AT Roadside Design Guide requires a minimum bridge width of 9.0 m on new structures based on a minimum shy line offset of 1.0 m on each side. The closest clear roadway width for bridges incorporating SL or SLW girders is 8.72 m for 8 girder lines. With 3.5 m lanes this leaves a shy offset of 0.86 m and is therefore not considered equivalent to the 9.0 m minimum clear roadway criteria. However, eliminating this option would result in an effective minimum bridge width of almost 10.0 m for this type of structure. Therefore, for Standard SLC Bridges, it is recommended that the 8.72 m clear roadway be considered applicable under the following circumstances:

For more detailed information refer to Alberta Transportation Best Practice Guideline 10.

3 – Standard SL/SLW Bridge Requirements – Girder Spans

Alberta Transportation’s Standard SL and SLW Bridge designs are available in various span configurations. Single and 3 span arrangements are provided. Two span arrangements are not carried forward from the older standard SCC bridge designs due to lack of utilization.

Span arrangements for bridges with 510 mm deep girders are listed on standard drawing S-1771.

Span arrangements for bridges with 700 mm deep girders are listed on standard drawing S-1782.

4 – SLC Bridge Requirements – Overall Bridge Length

Alberta Transportation’s Standard SL and SLW Bridges are available in various span configurations. These combinations allow for various bridge lengths from 8.0 m to 60 m typically in 2 metre increments. Single and 3 span arrangements are provided. Two span arrangements are not carried forward from the older standard SCC girder bridges due to lack of utilization.

A span arrangement table for bridges with 510 mm deep girders is listed on standard drawing S-1771.

A span arrangement table for bridges with 700 mm deep girders is listed on standard drawing S-1782.

5 – Standard SLC Bridge Requirements – Abutments

Alberta Transportation’s Standard SL and SLW Bridge incorporates a cast-in-place concrete abutment. Refer to the following drawings for details:

• for bridges with 510 mm deep SL girders: S-1778 to S-1781
• for bridges with 700 mm deep SL girders: S-1789 to S-1792

The Standard SLC Bridge abutment has the following design parameters:

• the abutment seat is 1000 mm high at the edges and thickens toward the crown for bridges with standard crossfalls
• the abutment seat width is 650 mm, measured on square to the seat
• to maintain sufficient soil cover at the front face of the abutment, the maximum height measured from the fill line to the underside of girder is 600 mm
• the top of the abutment seat shall be sloped so that it is parallel with the bridge longitudinal gradeline

6 – Standard SL/SLW Bridge Requirements – Pier Height

The maximum pier height for Standard SL and SLW Bridges, as measured from top of stream bed to underside of pier cap, is 6000 mm. Lateral bracing shall be installed at the heights indicated on the standard drawings for stability and to resist lateral forces. The top surface of the pier cap shall be sloped to match the longitudinal gradeline.

For bridges with 510 mm deep girders, refer to drawings S-1778 to S-1781.

For bridges with 700 mm deep girders, refer to drawings S-1789 to S-1792.

7 – Standard SL/SLW Bridge Requirements – Design Assumptions

The design assumptions and requirements specific to the Standard SL and SLW Bridge designs shall be satisfied at any particular site where a standard design is being considered. Typically these assumptions and requirements are listed in the General Notes on the standard drawings.

The following are examples of design parameters that shall be verified by the Consultant to be in conformance with those used in the Standard SL and SLW Bridge designs:

• pile loads and other geotechnical considerations
• hydrotechnical considerations
• vehicle loading
• ice loading and ice pressures