scope:

INTRODUCTION TO STANDARD DESIGNS AND DETAILS

The development of the Standard Designs and Details (SDD) has been undertaken by Network Rail to improve safety, asset reliability and increase efficiency. Their development is linked to Network Rail's overall business objectives, to improve reliability of the railways and reduce the funding requirements for on-going management and maintenance of the network. The basis of the SDD focuses on two main areas that derive from these issues:

• Ensuring that the design meets Network Rail's requirements

• The design is as successful as the designs of previous railway engineers, who built and maintained bridges that have given good service for approaching 150 years.

The use of the SDDs is promoted from the highest level within Network Rail.

The SDDs for the metallic underbridge repair and strengthening have been submitted and approved by Network Rail at Form A stage only of the Network Rail approvals process.

The purpose of the metallic underbridge repair and strengthening SDD was not to develop actual designs but to provide best practice guidance and details that can be used as reference when undertaking bridge specific strengthening designs.

The designer will need to produce a scheme specific Form A for the site under consideration. This Form A will detail the site specific parameters and the SDDs that will be used.

Following Form A approval the designer will need to undertake the detailed design and produce a full suite of scheme specific drawings, including general arrangement drawings, detailed design drawings and scheme specific details based around the SDD, where appropriate.

A Category II or III check of the site specific detailed design drawings is required.

Repair and Strengthening Suite Documents

A library of Standard Designs and Details for metallic underbridge repair and strengthening has been produced. This document contains guidance on the use of these standard details, including advice on the following:

• The repair and strengthening options contained within the suite of Standard Designs and Details

• Specific design restrictions and design assumptions

• Advice on circumstances when the Standard Designs and Details may not be appropriate

• Fabrication guidance

• Installation guidance

• Safety/CDM/environmental issues.

The library will be maintained and distributed by Network Rail to its stakeholders and key external suppliers for adoption across the network at a national level.

Form A Document

This document provides the following information on the details considered and the design basis of the proposed designs and details.

Technical User Manual

This document provides the following information:

• Details of the design process to be followed providing guidance on good practice.

• Details of the standard details and how there are to be incorporated into the Scheme Specific Design

Standard Details Drawings

Generic repair and strengthening details for the following:

• Main girder web plate strengthening

• Main girder web Strengthening adopting a 'Top Hat' arrangement

• Cross girder web plate strengthening

• Girder bottom flange plate strengthening

• Girder top flange plate strengthening

• Web stiffener plate strengthening

• Bearing stiffener plate strengthening

• U frame strengthening / New Cross girders

• Web Repairs

• Flange Repairs

• Trough Repairs