Category 3 checking

Following a number of serious bridge failures around the world in the early 70s, the UK’s then Ministry of Transport decided that almost all road-related structures would have to pass an independent technical approval (TA) certification process prior to construction. The nature of the approval depended in which ‘category’ the structure sat. The Ministry (now Department) used four categories of structure to cover almost everything: from simple roadside masts, to signal gantries, to very complex bridge structures. These complex assets have to meet the requirements of category 3 (Cat 3).

The purpose of a formal TA certificate is to give increased assurance for the planned construction or refurbishment of any highway structure. This is designed to ensure that the proposals are “safe to implement, that any new structures are serviceable in use, economic to build and maintain, comply with the objectives of sustainability, have due regard for the environment and that they satisfactorily perform their intended functions”. The TA procedures also endeavour to maximise safety and ensure that road users, the public and any others who may be affected are protected from adverse effects resulting from any structural work.

In practice the TA addresses not just today’s needs and objectives but considers the future provision for such things as heavier loads or upgrading.

At KGAL we have considerable experience as an independent Cat 3 checker. In accordance with the TA specification we verify detailed designs, not just for the structure’s aesthetics, engineering or durability, but for a whole range of impacting considerations: how easy will it be to build, inspect, maintain, and eventually demolish. The review extends beyond the structure to include any temporary works or compounds.

Our reports highlight any mandatory modifications but also give advice on options which might improve the project’s efficacy and / or cost (perhaps in the choice of materials or by reducing weight). And, by being an independent checker, but with a pedigree in engineering design for moving bridges and hydraulic steel structures, clients can be reassured that, from our analysis, calculations and verifications, the subsequent advice is sound, fair, objective and reliable.

Images: mechanical and electrical Cat 3 checking in England by KGAL for (l) Pell Frischmann in respect of the Dutch River swing bridge in Goole, Yorkshire; (r) The Babtie Group in respect of the Cathedral Green swing bridge in Derby.