Overview
Once a Standard SLC Bridge has been identified as appropriate for a given site (ie. satisfies the Standard SLC Bridge Requirements), the site specific design may proceed.
The following Standard SLC Bridge design drawings are available:
- Standard SLC Bridge design with 510 mm deep girders (superstructure and substructure): S-1771 to S-1781
- Standard SLC Bridge design with 700 mm deep girders (superstructure and substructure): S-1782 to S-1792
The framework for the Standard SLC Bridges has been designed to accommodate various site specific requirements by incorporating designated lettered variables in the standard drawing set.
The Consultant can use these variables to tailor suit the standard bridge framework to their site.
The Consultant shall clearly define all the variables in the standard bridge framework on the site specific P drawings.
The following is a summary of the Standard SLC Bridge verification requirements and the site specific design requirements.
Verification of design assumptions
The Standard SLC Bridge designs were developed based on various assumptions and limiting criteria. The Consultant shall verify that the site specific conditions are within these limitations and assumptions before the standard design is employed. The Consultant shall refer to the standard drawings and familiarize themselves of these criteria. (Commentary 1)
Structure related geometry
Much flexibility has been designed into the Standard SLC Bridge designs. Various independent and dependent variables have been incorporated and the Consultant can choose from various combinations while working within the standard bridge framework.
The Consultant shall select and identify these variables clearly on the site specific drawings. Variables include girder span lengths, number of spans, skew, and roadway width. (Commentary 2)
Foundations
Abutment piles
The standard design incorporates driven steel HP Pile sections with the weak axis orientated parallel to the abutment. See S-1779 or S-1790. The Consultant is responsible for determining the approximate pile tip elevations, based on site specific geotechnical information, and providing this information on the site specific drawings. (Commentary 3)
Pier piles
The standard design incorporates driven steel concrete filled closed ended pipe piles for SLC girder bridges with piers. See S-1780 and S-1791. The Consultant is responsible for determining the approximate pile tip elevations, based on site specific geotechnical information, and providing this information on the contract drawings. (Commentary 3)
Abutments
The Standard SLC Bridge designs incorporate a symmetrical cast-in-place concrete abutment with the following abutment features:
- 2% cross fall slope on either side of the roadway crown
- standard skews of 0, 15, 30, and 40 degrees
- various abutment widths are available and are based on the available standard superstructure widths and skews (refer to S-1778 to S-1881 or S-1789 to S1792)
The Consultant shall select the appropriate skew, clear roadway width and associated abutment geometry from the standard framework and clearly label on the site specific drawings. (Commentary 4)
Piers
Standard pier designs consist of symmetric cast-in-place concrete caps. The standard design supports skew values of 0, 15, 30, and 40 degrees. The Consultant shall provide the selected pier width and skew values on the site specific drawings. (Commentary 5)
Bearings
Standard SLC Bridge designs incorporate continuous 16 mm thick by 460 mm wide neoprene sheets as bearings. The superstructure is secured to the substructure using galvanized dowels. No bearing design is required from the Consultant when using the standard design framework.
Girders
Standard SLC girders are available in two depths: 510 mm and 700 mm. The 510 mm deep girder series come in 8, 10, 12, 14, and 16 m lengths while the 700 mm deep series accommodate 14, 16, 18, and 20 m spans. The span arrangement tables summarize the span configurations available in the Standard SLC Bridge designs (see S-1771 and S-1782). (Commentary 6)
Cast-in-place concrete deck and wearing surface
The standard design incorporates two deck thickness options depending on the wearing surface chosen: 125 mm minimum (150 mm nominal) decks for bridges incorporating standard deck waterproofing details, and 150 mm minimum (175 mm nominal) for concrete-to-grade decks.
All deck reinforcing shall be CRR (corrosion resistant reinforcing) as specified in Bridge Structures Design Criteria. The Consultant is responsible for providing a bar list for the deck reinforcing based on the selected bridge width and skew. (Commentary 7)
Bridgerail
The Standard SLC Bridge designs support the use of PL-2 bridgerail. Two standard bridgerail types have been incorporated: PL-2 Double Tube Bridgerail (S-1642) with associated approach rail transition (S-1643) and PL-2 Thriebeam Bridgerail (S-1648) with associated approach rail transition (S-1649). Bridges with centreline abutment to centreline abutment length less than or equal to 20 m shall use Thriebeam Bridgerail.
The Consultant shall clearly identify the chosen bridgerail type on the site specific drawings and provide post spacing within the limits of the standard bridgerail design and the girder spans chosen. Approach rail transitions shall be clearly shown on the general layout plan and elevation.
Approach slab
The Standard SLC Bridge designs include a 3000 mm long by 250 mm thick cast in place concrete approach slab. The reinforcing bar sizes and spacing have been included as part of the standard design. However, the Consultant is still required to provide a bar list for this reinforcing based on the selected bridge width and skew.
Reinforcing in the approach slab shall be corrosion resistant while the approach slab to abutment dowels and corbel reinforcing shall be stainless steel.
Contrary to major bridges, Standard SLC Bridge designs do not incorporate concrete collectors or drain troughs at the bridge ends due to the relatively short bridge length.
Commentaries
1 – SLC Girder Bridge Standard Design Verification
The standard SLC girder bridge designs are based on specific design criteria and assumptions. These are listed on drawings S-1771 and S-1778 for the 510 deep girder series. Similarly for the 700 deep girder series, this information is summarized on drawings S-1782 and S-1789.
The Consultant shall familiarize themselves with the limitations and requirements listed on these drawings to ensure the appropriate use of standard designs. Site specific criteria found to be in non–conformance with that listed in the standard design framework requires the Consultant to perform an engineering assessment to verify whether the standard design is in fact suitable for implementation at their site.
If it is found that the standard design cannot be used, the Consultant shall perform a site specific design in accordance with the requirements laid out for major bridges.
2 – SLC Girder Bridge Design Structure Related Geometry
The standard SLC girder bridge framework accommodates several geometric variables. The Consultant shall select the geometric variables within this framework that best suit the site specific requirements.
- Bridge width: Select a standard bridge width appropriate for the approach roadway geometry. Bridge widths shall be at least as wide as the approaching roadway (see the commentary on SLC girder bridge width). The standard drawings define the various geometric variables in tabular form based on the bridge width selected. (See S-1771 and S-1781 for information on the 510 deep girder series and S-1782 and S-1792 for information on the 700 deep girder series).
- Determine skew parameters: Standard designs include skews of 0, 15, 30, and 40 degrees. The Consultant shall choose the most appropriate skew value within the standard design framework and identify this on the site specific drawings.
- Bridge Length and span configurations: In general, SLC bridge designs accommodate bridge lengths from 8 to 60 m in 2 m increments. Single and 3 span configurations are included in the framework. Refer to the span arrangement tables listed on S-1771 and S-1782 for information.
- Roadway Cross section: The standard design assumes bridge symmetry about the centreline crown. A 2% cross fall from crown to gutter is provided for drainage purposes. Designs requiring alternative cross falls or nonsymmetric cross sections about the centreline of crown will require site specific design.
3 – SLC Girder Bridge Pile Design
The standard SLC girder bridge foundation design with 510 deep girders utilizes HP 310x79 and 610x9.5 concrete filled pipe piles for the abutment and pier respectively. Refer to standard drawings S-1779 and S-1780. Similarly, the standard SLC girder bridge foundation design with 700 deep girders utilizes HP 310x94 and 610x12.5 concrete filled pipe piles for the abutment and pier respectively. Refer to standard drawings S-1790 and S-1791.
The Consultant shall verify that the site specific loading conditions and required geotechnical resistances satisfy the requirements/limitations of the standard design. See S-1778 and S-1789. These include:
- Earth pressure: The standard SLC girder bridge design incorporate pinned integral abutments. In order not to overstress the abutment piles in a combination of bending and axial load, limiting assumptions are assumed in the standard design. When actual site conditions result in more severe load effects or less effective resistance, the standard design shall require engineering verification.
- Required bearing capacity: Pile load bearing requirements are outlined on the standard drawings. The approximate pile tip elevations shall be determined from these load bearing values and the site specific geotechnical information.
- Pier pile length above streambed where the pipe acts as a pier shaft. Maximum unbraced pipe lengths and associated lateral bracing requirements are provided on the standard drawings. The consultant shall ensure that the site specific bridge geometry is within the prescribed unbraced lengths and the maximum pier height (including the effects of scour) limits of the standard design.
- Ice forces on pier bents: The site specific ice forces shall be within the limits assumed and listed in the standard drawings.
If the conditions of the standard design are satisfied, the standard foundation can be employed.
The Consultant shall determine the approximate pile tip elevations and include them on the site specific drawings along with the standard number of piles and standard pile spacing designated for the bridge width and skew selected. Refer to drawings S-1781 or S-1791 for the 510 and 700 deep girder series respectively.
4 – SLC Girder Bridge Abutment Design
Our standard SLC girder bridge substructure is cast in place concrete. Refer to the following standard drawings for details:
- 510 deep SLC girder (S-1778 to S-1781)
- 700 deep SLC girder (S-1789 to S-1792)
The standard SLC girder bridge abutment seat is 1000 mm high at the edges. To maintain sufficient soil cover at the front face of the abutment a maximum abutment height, as measured from the top of fill line to the underside of girder, is 600 mm. Standard drawings allow for skew values of 0, 15, 30, and 40 degrees. Refer to S-1778 to S-1881 (510 girders) or S-1789 to S1792 (700 girders).
The Consultant is responsible for defining all of the variable abutment information, designated with single letters, as shown on the standard drawings. Refer to S-1779 or S-1790. The standard numerical values for this information are listed in tabular form on S-1781 or S-1792 and are sorted by clear roadway/structure width, and bridge skew.
The site specific drawings shall include an abutment layout similar to that shown on the standard drawings with the individual lettered dimensions replaced with the appropriate numbered values selected from the table.
5 – SLC Girder Bridge Pier Design
Our standard SLC girder bridge substructure is cast in place concrete. Refer to the following standard drawings for details:
- 510 deep SLC girder (S-1778 to S-1781)
- 700 deep SLC girder (S-1789 to S-1792)
The Consultant is responsible for defining all of the variable abutment information, designated with single letters, as shown on the standard drawings. Refer to S-1780 or S-1791. The standard numerical values for this information are listed in tabular form on S-1781 or S-1792 and are sorted by clear roadway/structure width, and bridge skew.
The site specific drawings shall include a pier layout similar to that shown on the standard drawings with the individual lettered dimensions replaced with the appropriate numbered values selected from the table.
The Consultant shall also select the appropriate standard pier pile bracing height from the tabulated values provided on S-1780 or S-1791 and include this in the site specific drawings.
6 – SLC Girder Bridge Girder Design
The Consultant shall identify the number of girders, span length(s), and the span combination chosen, from those included in the standard design, and identify this information on the site specific drawings.
The Consultant is also responsible for providing the bridgerail post spacing, within the limits of the standard bridgerail design, for use in placing the anchorage assemblies during fabrication of the exterior curb girders.
7 – SLC Girder Bridge Deck Design
The deck thickness requirements are dependant on the wearing surface to be employed. Standard designs for concrete to grade and ACP wearing surfaces are available. Concrete to grade wearing surfaces can be used on gravel roadways where no de-icing salts are applied. The nominal concrete deck thickness for the concrete to grade scenario is 175mm.
Conversely, bridges that are not paved during construction but are expected to be paved in the future, and are not exposed to de-icing chemicals in the interim, shall incorporate all the features required for future waterproofing and ACP installation. A concrete transition curb shall be used to protect the bridgerail curb ends during the unpaved condition. Refer to AT Best Practice Guideline 3 (BPG 3) for information regarding concrete bridge deck protection.
The nominal concrete deck thickness for the ACP waterproofing scenario is 150mm.
The Consultant shall ensure that the chosen wearing surface is clearly identified on the site specific drawings and the details shown reflect the appropriate deck thickness. The Consultant shall also prepare a site specific deck bar list for all bridges with more than a single span.
Bar size, number, and extension requirements beyond centreline of piers are provided on the standard drawings. The Consultant shall use this information, along with the span length and configuration specific to the site, to complete the deck bar list.
Refer to standard drawings S-1771 or S-1782 as applicable. Concrete deck reinforcing shall be corrosion resistant reinforcement. The type of corrosion resistant material to be used in the deck shall be determined in accordance with Bridge Design Criteria Appendix C “Protection Standards For Bridge Components”.