Kingsweston Footbridge

The Kingsweston Footbridge project in Bristol involved the removal and repair of a structurally damaged, Grade II listed footbridge that had been closed since 2015 after collisions with oversized trucks made it unstable. IDH was appointed by Griffiths to deliver a series of temporary works designs, including technical support for the crane lifting operation and Category 3 scaffold checking. The project required meticulous planning to ensure the structural integrity of the bridge during removal, as it was a significant landmark for the local community.

Challenges

1. Limited Space and Listed Structure Restrictions: Being a listed footbridge, the removal process had to be extremely delicate, with absolutely no damage. The bridge needed to be removed in two sections (which relied on each other for stability) posing significant risks during the lifting process. IDH’s design had to ensure that each half remained stable, using temporary propping to avoid collapse.

2. Potential for Uneven Lift: The bridge was installed into abutments that had likely become warped during the initial damage, which introduced the risk of an uneven lift. IDH needed to factor in the potential for the bridge to stick during the lift and account for the possibility of a sudden release once freed from its supports.

3. Tight Schedule with Road Closure: All works had to be completed under a temporary road closure, requiring precise coordination between teams to ensure the bridge was removed before the road was due to reopen. Any delays could result in extended road closures, leading to disruption.

Solution

To address the project’s challenges, IDH implemented a series of innovative and tailored solutions:

1. Propping Scheme for Structural Stability: IDH developed a detailed propping scheme to ensure stability throughout the removal process. The design allowed each half of the bridge to remain stable once the other half was removed, using temporary props at key points of the structure.
2. Innovative Lifting Frame Design: IDH designed a custom lifting frame to accommodate the bridge’s potential resistance during the lift. Dynamic safety factors were built into the frame’s design to account for the potential sudden release of the bridge if it became stuck. The frame evenly distributed the bridge’s weight, minimising the risk of damage during the lift.
   • The lifting frame was engineered using advanced dynamic load analysis techniques, allowing IDH to simulate various lifting scenarios and identify the optimal lifting angles and configurations to enhance stability and safety during the operation.
3. Efficient Frame Construction and Assembly: The original lifting frame design, which relied on heavy steel PFC units, was value-engineered by IDH into a Superslim Soldier construction. This change eliminated the need for on-site welding and simplified assembly, with smaller, bolted members that could be assembled more quickly. Proprietary lifting eyes further streamlined the installation process.

Outcome

By implementing these tailored solutions, IDH successfully:

• Achieved Client Objectives: The entire bridge was removed safely, with all works completed within the road closure period.
• Ensured Structural Integrity: The bridge was lifted in two pieces without damage, despite the tight constraints and risks involved.
• Enhanced Project Efficiency: The careful planning and streamlined design reduced on-site construction time, minimising disruption to the local community and ensuring timely project completion.
• Demonstrated Innovation: The Superslim Soldier lifting frame design proved both time- and cost-effective, while ensuring that all potential issues were addressed ahead of the lift.

“Working closely with IDH on the Kingsweston Footbridge restoration, we were impressed with their ability to design and implement temporary works and a crane lifting frame that prioritised both safety and the preservation of the listed structure. Their collaborative effort with Griffiths ensured the project ran smoothly and efficiently.” – Mike Clark, Site Agent, Griffiths.