Innovative Deconstruction in Challenging Environments
Published: 12/10/2023 13:14
Located on the edge of the Hams Hall Distribution Park, this now redundant 1953 rail bridge was to be demolished to reduce ongoing maintenance liability. The 9m wide bridge consisted of two 14.6m spans over the River Tame consisting of 4No. Main Plate Girders, 2No. Parapet Edge Girders and concrete filled steel trough decking between. Passing over the bridge at just 10.6m clearance were a bank of 132KVA overhead HV cables with a 6m exclusion zone to prevent arcing thus creating an operational headroom restriction of just 4.6m on the bridge deck.
Access to the bridge was also restricted by single track footpaths and dense foliage. Add to that the environmental constraints of a salmonoid River Tame, badger sets, nesting birds, otters, and bats roosting on the underside of the bridge.
These complex restrictions lead us and our client, AR Demolition to an innovative solution, which involved a bespoke temporary gantry crane system directly over the bridge operating within the 4.6m headroom restriction. The concept was that the low headroom gantry crane would be used to lift large sections of the bridge, that were over 20 tonnes, and move them onto the north bank of the river outside of the HV exclusion zone where they could be demolished using more traditional methods.
The bridge was cleared of vegetation, ballast, infill concrete and the steel bridge deconstruction split into two phases: Phase 1; Inner girders and deck. Phase 2; Outer girders and deck. Access scaffold was designed and installed suspended from the existing bridge beams during phase 1 and from the gantry crane main beams during phase 2. After the bridge deck is removed the suspended scaffold was progressively stripped and the final phase was to retract the gantry crane rails from over the river using a reverse guided launch process.
Richter worked in close collaboration with AR Demolition and their specialist fabrication team throughout the whole process providing design, design check, TW checking and sign-off as well as providing an Appointed Person to control the lifting operations.
Sustainability was considered in the design, AR Demolition identified that the main girders and gantry crane wheels could be utilised for a bespoke demolition screen and so components were sized to ensure suitability for future re-use. Elsewhere proprietary hireable components were utilised.
Hear from one of our engineers about the project in the video below