CROSS Safety Report
Inadequate bridge bearing pad installation
During the final construction phase of a reinforced concrete bridge deck, the contractor installed the elastomeric bridge bearing pads using a non-approved and potentially dangerous methodology.
Key Learning Outcomes
For the design and construction team:
Consider engaging with specialist suppliers such as bridge bearing suppliers to seek advice on the proper installation of their products
Toolbox talks and workshops with the site crew on the correct installation of the products can help ensure construction is carried out in accordance with the design
It is good practice for design and construction to be integrated such that all parties are content with construction sequencing and methodology before execution of the works
If the sequencing of works is to be altered it should be be reviewed and agreed by all parties
For civil and structural design engineers:
Where specialist systems such as bridge bearings are used, it is beneficial to have a close working relationship with the supplier from the earliest opportunity to ensure design requirements are met and the installation sequence is shown on drawings
It is good practice to review the contractors proposed installation method to ensure there is sufficient level of detail addressing the installation of critical elements such as bridge bearings
On projects where there is a high level of uncertainty over the design approach and installation requirements, consider attending site to oversee the works
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
During the final construction phase of a reinforced concrete bridge deck, the contractor installed the elastomeric bridge bearing pads using a non-approved and potentially dangerous methodology. This involved screwing the pads to wooden batons so that they could be temporarily suspended over shuttering to facilitate bedding grout being poured beneath. These pads consist of rubber layers separated by steel plates with a rubber cover to encapsulate the bearing.
By puncturing the rubber cover, the contractor introduced a means of water ingress which could lead to corrosion of the steel plates. At best this invalidates the product warranty. At worst, this could lead to potentially dangerous structural issues unforeseen by the design team. These issues were compounded as the contractor changed their construction sequence without communicating their plans to the site verification team. This meant that the verification team, with responsibility for overseeing construction of the bridge deck and installation of the bridge bearings, were not in attendance during these works.
These issues were compounded as the contractor changed their construction sequence without communicating their plans to the site verification team.
The erroneous installation was only later discovered on review of photographs thankfully taken by other members of the site team (who had no actual responsibility for overseeing the bridge construction). This issue was immediately escalated with the design team and the contractor. The manufacturer was subsequently contacted and confirmed that the bearings had to be replaced. The design team requested that a methodology for replacement of the bearings be submitted and approved ahead of any further construction works.
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Expert Panel Comments
Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.
This event reinforces the need for an adequate specification of workmanship and materials for bearing systems, and an adequate inspection and test plan to ensure that the works are constructed in accordance with the specification. It appears fortuitous that someone took photos of the install whilst the site verification team were not in attendance. Had they not done so, would the issues arising have led to a latent defect to be dealt with as the structure fails in service? It is vital that there is adequate supervision of the works at all times.
As always it is imperative to comply with any agreed method statement for critical stages of work. It is of concern that this was only picked up as a result of a review of photos, which implies that either there was no agreed method and sequence for this operation, or there was a late change that didn't go through the approvals process.
It is good practice for design and construction to be integrated such that all parties are content with construction sequencing and methodology before execution of the works. Such issues might then have been picked up, avoiding all the unnecessary costs and time undergoing rework. Indeed for such a critical installation, and need to maintain the warranties and integrity of the bearings, it would be expected that the design team would have highlighted how these were to be installed.
CROSS are aware of another event whereby an edge beam rotated off its bearings during construction. Fortunately the edge beam which rotated off the bearings was still on the crane, which coped with the sudden change in load, otherwise things could have been much worse.