Temporary Works
Weedon Street Bridge, Sheffield, UK
Project Brief
LSY Engineering Consultants Ltd was appointed by Cadent Gas Ltd, to provide structural engineering services for works associated with Weedon Street Bridge in Sheffield.
The project involved the removal of two 24-inch gas mains attached to the east and west elevations of the existing bridge structure. Each pipeline extended approximately 70 metres across the River Don and required careful planning and execution due to the age of the bridge, the scale of the pipework, and the operational constraints of the site.
Our appointment included:
- An initial structural condition survey and reporting.
- Structural assessment of the proposed temporary works and scaffold arrangements.
- A post-completion structural inspection to verify that the removal works had not adversely affected the bridge.
Challenges
The project presented a number of engineering and logistical challenges. Weedon Street Bridge is an ageing steel girder structure supported on masonry piers and spans the River Don adjacent to the busy Meadowhall Road and Weedon Street junction. The bridge carried live traffic throughout the duration of the works, requiring careful planning to ensure public safety and maintain traffic operations.
Working above a live watercourse introduced additional risks that required comprehensive assessment and mitigation before any temporary works could be installed.
During the initial survey, several existing defects were identified, including localised corrosion to steel elements and cracking within the masonry parapets. As a result, it was essential to establish a detailed condition record before works commenced to allow meaningful comparison during the post-completion inspection.
The removal of the gas mains also required the installation of significant temporary scaffold structures. Due to access constraints and the location of the pipework, the scaffold design incorporated cantilevered arrangements supported by kentledge, requiring detailed structural checks to confirm the bridge could safely accommodate the imposed loads.
Process
LSY Engineering Consultants Ltd was initially appointed to undertake a comprehensive non-intrusive visual inspection of Weedon Street Bridge. Following the site assessment, we produced a detailed structural report outlining the bridge’s condition, together with our observations, conclusions, and recommendations for the proposed works.
Following completion of the initial survey, we were commissioned to undertake structural design checks for the temporary scaffold required to facilitate the removal of the existing gas mains. The scaffold design comprised cantilevered aluminium beams, birdcage scaffolds, and staircase access arrangements. Our assessment verified that the proposed temporary works, including kentledge blocks weighing up to 1,300kg in worst-case loading scenarios, could be safely accommodated without adversely affecting the structural integrity of the existing bridge.
All assessments were undertaken in accordance with BS 5975: Code of Practice for Temporary Works Procedures and the Permissible Stress Design of Falsework.
Structural checks confirmed that load effects remained well within acceptable limits, with the additional temporary works loading resulting in an overall increase of less than 10% of the existing structural weight. This satisfied the relevant criteria for waiving the requirement for a full structural analysis of the bridge, providing confidence that the proposed works could proceed safely and efficiently.
Outcome
Following completion of the gas main removal works, LSY undertook a post-completion structural inspection.The inspection confirmed that the bridge remained in substantially the same condition as recorded during the initial survey.
No evidence of structural deterioration or damage attributable to the temporary works or pipe removal operations was identified. Movement readings recorded remained consistent with those measured during the pre-construction survey, confirming that no significant movement had occurred during the works.
The project was completed safely and successfully, enabling Cadent Gas Ltd to remove the redundant gas mains without disruption to the structural integrity of the bridge or the surrounding infrastructure.
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