Clarence Bridge, Regent’s Park, London, UK: the assessment and repair of a wrought iron lattice bridge

Clarence Bridge provides pedestrian and light vehicle access across the southern end of the boating lake in Regent’s Park, London, UK. It had been poorly maintained and was suffering from severe corrosion. With section losses in excess of 50% at lattice intersections and at deck level, its load-carrying capacity and future were limited. Royal Parks sought specialist conservation engineering advice on what were the best options for the bridge from Hurst Peirce + Malcolm, consulting engineers. A detailed inspection and analysis of the bridge in its weakened state led to options for repair ranging from complete replacement of all weakened sections in the lattices and webs to installing a mid-span support. It would be difficult to repair the lattices where they pass between the vertical stiffeners. Fortunately, the lattices have a high level of redundancy and with re-analysis of the structure, it was possible to justify that the bridge could function with many of the members repaired but with some members retained in their weakened state. The repairs took the form of cutting out weakened sections of the lattice and web plate and welding mild steel sections. This also required the replacement of some 286 rivets using the hot riveting technique.