SCI P154 Design of steel bridges for durability







1 INTRODUCTION

Over the past 20 years, engineers have become increasingly aware of the importance of ensuring the

durability of structures. Any structure, regardless of the material in which it is constructed, is likely

to require periodic inspection, maintenance and, occasionally, repair, to ensure that it continues to

function satisfactorily over its lifetime (commonly, for bridges, specified as 120 years). The

objective of design for durability is to ensure that such inspection and maintenance is kept to a

practical minimum and is as easy as possible to carry out when needed, so that the total ‘whole-life’

cost of the bridge is minimised. This can mean that the ‘first cost’ of the structure may have to be

increased in order to reduce the subsequent cost of inspection, maintenance and repair. To have a

basis for comparison, attention has to be given to methods of converting future costs into equivalent

capital costs at current prices. In the UK, guidance on how to carry out the cost-discounting

calculations is given in the Highways Agency (HA) Standard BD 36/92, together with the associated

Advice Note BA 28/92. The sum of the initial cost plus the ‘discounted’ future cost of inspection,

maintenance and repair gives the whole-life cost of the bridge.



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