Chapter 25: Inspection and assessment

The different types of inspection are described for the maintenance or acceptance of bridges, the former category comprising safety, general, principal and special inspections and inspections for assessment. With reference to rail infrastructure, visual and detailed examinations are equivalent to general and principal inspections. Preparation, records, health and safety, access and good practice are touched on, and the requirements for each type of structure are summarised. Good practice for inspection is discussed under the headings of structural appreciation, structural identity, structural disguise, accuracy, weather and photography. Inspection of different types of structure is described for signs of distress in reinforced concrete structures, prestressed bridges, drainage systems, hollow members, culverts, steel structures, corrugated steel buried structures, masonry structures and retaining walls. Assessment is introduced, and the formulae for identifying whether a structure passes its assessment are provided. The levels of assessment are described, followed by descriptions of preferred methods of analysis for reinforced concrete slabs, reinforced concrete beams and slabs, steel beams and reinforced concrete slabs, inverted T-beam decks, shear key and filler beam decks, single-span brick arches, continuous brick arches, concrete post-tensioned beams or slabs, concrete post-tensioned box girders and steel box girders. Common structural problems are listed for reinforced concrete slabs, reinforced concrete beams and slab, beams, reinforced concrete beams, box culverts, prestressed concrete, halving joints, composite beams, filler beams, riveted beams, cast iron beams, steel beams, steel box girders, jack arches, brick arches and piers. Strength considerations of deteriorated reinforced concrete structures are summarised. A dozen techniques for obtaining additional strength from assessments are then each described in detail. These are realistic models, comprising global models and mathematical models. Global models are described under soil–structure interaction, surfacing, inclined neutral axis, bearing clamping, redundancy, composite action and bridge modelling following pier impact. Mathematical models are discussed under bridge decks and non-linear finite-element models.