Rehabilitation of Haulbowline Bridges, Cork Harbour

This paper describes the complex rehabilitation of two large post-tensioned concrete bridges in Cork Harbour using non-linear finite element modelling to optimise the remediation works. The works were designed and delivered... [ view full abstract ]

This paper describes the complex rehabilitation of two large post-tensioned concrete bridges in Cork Harbour using non-linear finite element modelling to optimise the remediation works. The works were designed and delivered within budget in a short time period to allow the environmental rehabilitation of Haulbowline Island to proceed. The bridges have a combined length of 353m over 17 spans. The superstructure is a mixture of post-tensioned concrete elements and conventional reinforced concrete elements. A key feature of the bridges is that 7 of the spans are suspended from half joints which are post-tensioned transversely. A full scale assessment of the structures which included a Post-tensioning Special Inspection (PTSI) was conducted. Early stage load assessment models indicated that strengthening works would be required and that such works would be complex and long in duration. Subsequent non-linear finite element models of the bridge half-joints indicated that a reconfiguration of the bearing arrangement on the half-joints would improve the force distribution at these critical elements. This analysis allowed a strengthening scheme to be developed which could be implemented in a reasonably short timescale while keeping the bridges open to traffic. The strengthening scheme included the lifting of 7 suspended bridge spans, each weighing 200 tonnes, for bearing replacement. The scheme also included significant reinforced concrete repair works, the replacement of bridge joints, deck waterproofing, the reorganisation and renewal of several significant services on the bridge, the addition of a new deck edge beams with a modern bridge parapet system and the provision of enhanced public lighting.