- Publication no: ABC2017-089-17
- Published: 21 April 2017
Aberdeen Bridge was configured so that substructure support locations matched those of existing bridges at this crossing of Highway No 9 over the Hunter River in New South Wales. The bridge comprises a main central span of 55.5 m and adjacent continuous spans of 42.8 m on each side of the main span.
The 9.4 m trafficable width superstructure is made up of three steel trough girders that support transversely orientated precast concrete planks onto which a cast-in-situ reinforced concrete deck slab was constructed. The steel girders are tapered in elevation to form a deeper section over the pier supports required for increased structural strength. Given the constraints on road grade and clearance over flood levels the degree of girder tapering was restricted requiring an innovative solution of incorporating a composite reinforced concrete infill to the bottom compression flange of the girders.
Girder erection was undertaken in multiple stages with segments connected by site welding. Pre-camber of girders to account for construction staging was a primary consideration in design development as well as monitoring during construction. An unusual feature of the construction sequence required the central portion of the main span to be erected last, once the outside adjacent spans with partial cantilevers extending into the main span were secured. The contactor developed a simple method of increasing the gap into which the final mid-span girder sections were launched and then pulled toward each other to form full contact between adjacent faces for effectively connecting using site welded splices.
This paper presents the construction staging adopted by the contractor to comply with the staging accounted for in the development of the design as well the variations incorporated by the contractor to achieve an outcome with excellent compliance to the required final roadway alignment.