Squibb Park Bridge Update
Squibb Park Bridge represents a collaborative effort of Brooklyn Bridge Park, NYC Parks, local elected officials and numerous community groups to improve pedestrian connectivity from the Park to Brooklyn Heights and beyond. In March 2013, Squibb Park Bridge opened. It was an immediate success and provided a vital circulation link for pedestrians, offering Park visitors a convenient and dramatic approach to the waterfront and easier access to public transportation.
In August 2014, after we observed structural misalignment, the Bridge was closed. Ove Arup & Partners (Arup), one of the world’s top engineering firms, performed a structural peer review of the Bridge design and repair detail. We also engaged Atlantic Engineering Laboratories at this time to perform repair inspections. In January 2016, BBP retained Arup as the new engineer of record to design and oversee implementation of a plan to retrofit and stabilize the bridge.
In July, we announced that Arup had finalized a structural retrofit to address stability issues with the Bridge’s design while retaining its distinct aesthetic and, most importantly, allow for it to be safely reopened.
Since July, we have selected construction manager Pavarini McGovern, refined the repair plan and have a cost estimate in place. On October 5, BBP’s Board of Directors authorized BBP to enter into a construction contract. Work is expected to begin in this month and we project reopening of the Bridge in spring 2017.
Overview of Structural Remediation
Arup has developed a solution that requires simple modifications to the existing bridge structure in order to resolve the performance issues of the original design. Three principal modifications are proposed to address stability of the bridge’s main spans:
- Enhance connections of select lower timber diagonal struts to increase their load carrying capacity. This will be achieved using steel collars bolted around the existing steel to timber connections.
- Install cable clamps to prevent sliding and lift-off of the cables and significantly reduce deflections of the bridge.
- Add steel pins through the connections to prevent the timber logs from pulling out of the steel cups.
In addition to these items, tuned mass dampers will be installed to reduce vibration of the bridge as pedestrians walk across it. The dampers work by absorbing energy as the bridges moves and will reduce but not eliminate the bounce which is characteristic of the bridge.
While the remediation measures proposed are simple, significant temporary works are required to support the bridge while it is modified. The following illustrates the expected sequence of work – which will be developed in detail once a contractor is selected.
- Scaffolding will be installed below the main spans, this will include adjustable supports so that the bridge can be supported and re-positioned (see below).
- Once the scaffolding is in position, the steel cups connecting the timber elements will be drilled and a pin added to each.
- At this point the cables will be released and the bridge will be jacked vertically and horizontally until it is straight.
- With the bridge geometry corrected, the cable clamps will be added to lock the bridge into the desired shape.
- The tuned mass dampers and steel collars will be installed.
- The bridge geometry will be checked before the scaffolding is removed.
- With the bridge once again carrying its own weight, the geometry will be re-checked and the tuned mass dampers adjusted to optimize their performance.
- Tuned mass dampers were successfully installed in late January. All planned retrofit improvements are now complete.
- Repairs to the hand rail lighting are expected to be completed by the end of February.
- The supporting scaffold and work platform will be removed in the next few weeks.
- The next step is to file for final agency signoffs.