Design Guide for Composite Highway Bridges

Design Guide for Composite Highway Bridges

Composite construction, using a reinforced concrete slab on top of steel girders, is an
economical and popular form of construction for highway bridges. It can be used over a wide
range of span sizes.
Design Guide for Composite Highway Bridges covers the design of continuous composite
bridges, with both compact and non-compact sections, and simply supported composite
bridges of the ‘slab-on-beam’ form of construction.
The guide assumes that the reader is familiar with the general principles of limit state
design and has some knowledge of structural steelwork. It provides advice on the general
considerations for design, advice on the initial design process and detailed advice on the
verification of structural adequacy in accordance with BS 5400. It concludes some advice on
structural detailing. The determination of design forces throughout the slab is described, key
features relating to slab design are identified, and detailed advice on slab design is given. The
selection of protective treatment and bearings is excluded, being well covered in other texts
This guide includes a set of twelve flow charts that summarise the design process following
the rules in BS 5400, taking into account the significant amendments recently made in the
latest issue of BS 5400–3 Code of Practice for the design of steel bridges.
Three worked examples describe the initial and detailed design aspects for a four-span
bridge, a three-span bridge and for the deck slab of a simply supported bridge. Each example
is presented as a series of calculation sheets, with accompanying commentary and advice
given on facing pages.
Where reference is made to a clause in one of the Parts of BS 5400, the reference is given
in the form ‘3/9.1.2’, which means clause 9.1.2 of BS 5400–3.
References are made in the text to further advice in ‘Guidance Notes’. These are a series of
notes, published by The Steel Construction Institute[4], that give concise advice from the
members of the Steel Bridge Group, a technical group of experienced designers, fabricators
and clients.

The Design Manual for Roads and Bridges (DMRB) comprises a collection of Standards and
Advice Notes issued by the ‘Overseeing Organisations’ [The Highways Agency (for England),
The Scottish Executive Development Department (for Scotland), The National Assembly for
Wales (for Wales) and The Department for Regional Development (for Northern Ireland)].
The collection includes some documents issued before 1992 by the Department of Transport
that are still valid.
In relation to bridges, the documents give guidance to the designer and provide
interpretation and application of BS 5400. They also correct typographical errors in the
Standard and amend it where considered appropriate. A list of the key documents relating to
the design of new bridges is given in Appendix B. Designers should check that they have upto-
date copies when carrying out design.

Specification for Highway Works
The four Overseeing Organisations also issue theManual of Contract Documents for
Highway Works (MCDHW), which comprises six separate Volumes. These documents
provide the basis for documentation for individual contracts, and are supplemented, for each
contract, by project-specific requirements. Of particular relevance to steel bridge construction
are the sections known as ‘Series 1800’ of Volume 1, Specification for Highway Works
(SHW), and Volume 2, Notes for Guidance on the Specification for Highway Works. The
SHW implements BS 5400–6, modifies some of its clauses and provides the framework for
additional project-specific requirements. For guidance on the latter, see SCI’sModel

Appendix 18/1 document.


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