Siddington House Jacked Installation Method - 29 August 2011

Sunday 30th April 2000

Macrete Ireland Ltd were commissioned by Gloucestershire County Council to provide a replacement bridge for Siddington House Bridge on South Cerney Road, south of Cirencester. The existing structure shown below was in a state of despair and was classified as a weak bridge.

The bridge details are as follows:

Span = 4.00m
Rise = 1.50m
Width = 7.00m

Contractor: ENVEX
Client: Gloucestershire Highways

Following the preliminary design stage a potential obstacle was identified. The existing service ducts running through the bridge would hinder the installation as they would prevent the crane from lowering the FlexiArch units into place. Due to the limited clearance over the proposed crown level (~10-15mm), a method of sliding the units into place was introduced

Grease was used on the face of the end block and springing unit to sufficiently reduce the friction between the 2 elements, so as to allow a smooth movement from placing the unit to its final position. A hydraulic bottle jack was used to push the feet of the arches.

In order to generate enough force to push the units, a means of propping the bottle jack had to be devised. The solution was to provide 30mm sleeves in the springing seat at key locations, which would allow 25mm dowel bars to be placed into the unit. The protruding bar would then provide an adequate reaction so as to push the unit.

The installation of Siddington House Bridge is documented in the following photographs:

1. Arrival of Flexi Arch Units
2. Placement of 1st unit on pre installed springing seat.
3. Minimal clearance provided over crown of arch.
4. Dowel bar fitted in sleeve
5. Bottle jack connected to hydraulic manual pump.
6. Timbers used to provide uniform load distribution without hard surface.
7. Continue to place units
8. Continue to place units
9. Spandrel Walls installed
10. Completed Bridge

Following the installation the retrofitting method proved successful. The units were able to slide gradually into place without damage to the concrete. The client and contractor were delighted with what was achieved.