ACT Heritage Library Manuscript Collections

HMSS 0467 Commonwealth Avenue Bridge Construction Photographs

Construction History

Commonwealth Avenue Bridge was designed and built for the National Capital Development Commission by G Maunsell and Partners, consultant architect William Holford and Partners, constructed by M R Hornibrook (NSW) Pty Ltd (on behalf of Hornibrook-Kaiser Joint Venture), supervising authority Commonwealth Department of Works.

Tenderers had a choice of three designs for at least some elements of the bridge (tender documents are held in the National Archives of Australia, NAA A1655:46). The contract with Hornibrook was signed on 9 February 1961 with an expected practical completion date of 30 June 1963; work commenced in March 1961. The eastern roadway and bridge opened on 10 September 1963, and the western on 2 November 1963. The Certificate of Practical Completion was issued on 15 January 1964 with a 52 week maintenance period thereafter.

The project consisted of two parallel bridges across Lake Burley Griffin and two prestressed concrete approach bridges at the southern end. Construction included embankments, roads, services and a sewage pumping station at the north end of the main bridge.

Each main bridge is a hollow precast box girder construction, fully continuous over the five spans and post-tensioned in a single operation with external cables over the full 1030 foot (314 metre) length of the superstructure – the first time such a method was used for a major bridge in Australia. The five spans are 185, 210, 240, 210 and 185 feet (56, 64, 73, 64, 56 metres) long, each roadway is 37 feet (11 metres) wide with one 6 foot (2 metre) footpath on the outer edge and one 2 foot (0.6 metre) footpath on the inner edge. The footways are cantilevered and were cast in situ after completion of stressing.

The abutments at each end of the two bridges are connected by a central terrace area. The limits of the main bridges are defined by four pylons. The superstructure is supported on roller bearings at the abutments and piers; those at the south end were fixed at the completion of construction so that expansion movement is taken up at the north end.

Each pier sits on a massive base of reinforced concrete that distributes the load. Piers are numbered from the south end. The foundations for Pier 2 are driven, raked steel H-piles of extremely heavy section. All other piers and the abutments are on foundations of solid 6 foot (2 metre) diameter reinforced concrete cylinders seated on rock.

The underpass bridges on the southern approach are each four-span structures of 160 feet (49 metres) total length. The reinforced concrete decks were poured in situ on top of precast girders supported on trestles. These bridges span the cloverleaf roadway.

The northern approach embankment required creating a high promontory projecting 500 feet (152 metres) into the lake from the original shoreline, which both shortens the bridge and emphasises the division into the Central and West Basins. It also blocked the original river channel, requiring a diversion channel to be created. The southern abutment was also placed so as to provide a symmetrical shoreline for the Central Basin. Visual continuity between the Central and West Basins was ensured by the bridge’s low profile and lights concealed under the handrails.

An underground sewage pumping station was constructed on the east side of the promontory to pump the sewage from North Canberra across the bridge to the treatment works (then at Weston Creek). A vent for the sewer main is incorporated in the southeast pylon.

A works yard and a pre-casting yard were established adjacent to the south bank, and all rock, sand and aggregate were sourced locally. For each bridge 102 reinforced concrete box segments three metres long and weighing 45 tons were cast on site, left to cure, then placed by gantry on the timber falsework (trestles). The three-inch gaps were filled with concrete to produce a smooth, continuous roadway.

During construction the two existing bridges across the Molonglo River and its secondary channel (the Billabong) and their separating embankment were removed, a diversion channel for the river was cut and maintained, and a temporary low level diversion road constructed. Excavated soil was used to create the northern promontory and to provide fill behind the concrete retaining wall on the southern embankment. Until the permanent 24 inch (0.6 metre) water main was installed on the bridge itself, temporary water mains were laid across the lake bed. Finally, an in-ground lawn watering system was installed in both approach embankments.

The collection documents most of these phases of construction. From February 1963 lists were created to identify content in the various sets of photographs, but there are also sets and individual photographs without identification. Moreover, photographs used to illustrate the Construction Report were sometimes recaptioned; this finding aid includes both captions. (Commonwealth Avenue Bridge construction report H 625.709947 COMM)

It also includes a construction chronology based on a series of reports of progress in the Canberra Times, usually in the weekly feature ‘Sidewalk Supervisor’. They began on 4 August 1961 and continued until 25 October 1963, and were designed to explain the construction process to the public.

Measurements at the time were Imperial.  We have added the approximate metric equivalent in parentheses.

Construction Chronology

4 August 1961

Work has begun on the south bank of the river, to the east of the bridge site. Site offices, storage sheds, compressor room, fitter shops, carpenters shops, workshops and a materials security area have been established near King Edward Terrace.

In front of these buildings a concrete-mixing plant is under construction. A jetty-like structure will lead from here towards the river, and will carry a monorail system of hoppers containing mixed concrete to the casting beds at the end of the jetty.

The twin row of heavy timber piles leading from the river will carry the temporary timber framework to support the 102 concrete segments for construction of the eastern bridge. An average of 15 piles a day is being driven.

On the island between the two existing bridges a percussion drill is being used to determine the quality of founding strata for the piles. The southern bridge is known as the Billabong Bridge, and the truss bridge across the Molonglo River is the Commonwealth Avenue Bridge.

25 August 1961

At the south abutment part of the foundations are being poured. These are 6 foot diameter reinforced concrete cylinders poured to a depth of 35 feet (11 metres). Steel casings inserted in each shaft to prevent collapse will be withdrawn as the concrete is poured into the shaft. Completed cylinders are recognisable by the circular mesh of reinforcing steel projecting from the top.

A stiff-leg crane, or derrick, has been erected near the offices and sheds to handle timber for the trestles.

15 September 1961

All the timber piles have been driven. Fabrication of the trestles to be mounted on top of the piles has started.

Two foundation cylinders have been poured for pier 1 for the eastern bridge. Drilling the hole for pier 4, at the northern end, has begun.

The monorail is nearing completion.

13 October 1961

Construction of the temporary framework (trestles) to support the pre-cast segments of the eastern bridge is under way.

In the casting yard the eight concrete foundations have been poured. These will support the formwork for the precast concrete segments that will form the carriageway. The 25 ton stilt-leg crane will be used in assembling the timber formwork within the concrete foundations.

The concrete plant is ready for use and the monorail is almost finished.

Rails have been laid for the gantry which will convey completed segments from the casting area to the bridge's temporary supports.

The temporary, low-level road under construction west of the Billabong Bridge is being made ready for sealing. Commonwealth Avenue will be diverted along this road when the Billabong Bridge is dismantled.

A temporary bridge of steel girders carried on timber piles is being built across the existing river channel. This bridge is to provide access for earthmoving equipment working on the construction of the northern abutment.

3 November 1961

The low-level deviation road on the western side of the bridge will be bitumen sealed in the next few days, followed by erection of safety fences and signs.

About 200 yards upstream of the existing truss bridge work is beginning on the temporary low-level bridge that will carry earth-moving plant working on removal of the central embankment (or island) between the existing bridges. The bridge will be built using the steel girders recovered from the dismantled Billabong Bridge.

Spoil from the embankment will be used in the formation of the peninsula which will surround the northern approach embankment. Foundations and rockfill for the south abutment are complete and pouring of concrete for the main abutment is now proceeding.

Sinking of concrete cylinder foundations for the eastern bridge is about half complete.

The large stack of concrete blocks on the southern approach to Billabong Bridge, on the opposite side of the bridge to the diversion road, is a test load which has been placed on the reinforced concrete piles for the Parkway Underpass Bridge (the small bridge over the clover-leaf road). The piles are being tested up to 100 tons.

9 November 1961

The diversion road replacing the Billabong Bridge opened at the weekend.

14 November 1961

Dismantling the Billabong Bridge began yesterday.

1 December 1961

Billabong Bridge has been dismantled; timber piles are still in position. Temporary low-level bridge has opened to earth-moving plant and much of the embankment has been removed to form the northern peninsula. A buried 24 inch (0.6 metres) steel water main was first removed and replaced by an 18 inch temporary main running alongside the deviation road.

Formwork has been erected for the first part of the southern abutment for the eastern bridge and concrete pouring has begun.

About midway along the embankment formwork has been erected ready for pouring Pier 4 East. To the east of Pier 4 is a large orange-coloured steel tower. When the rest of the embankment has been removed, an identical tower will be erected on the western side of the western bridge. The towers will be on the railway lines laid in October, running parallel to the new bridge, and will support the steel launching truss brought from the Kings Avenue bridge site to form a mobile gantry. This gantry will be used for placing concrete bridge segments on the temporary timber framework which will sit on heavy wooden piles—already driven in position for the eastern bridge.

10 February 1962

Eleven 30 foot (9 metre) high timber trestles collapsed in a storm at Commonwealth Avenue Bridge yesterday. The trestles were about one third of the temporary framework erected so far. Only one or two of them were damaged, and the rest could be re-erected.

17 March 1962

Work has begun on a 2000 foot (610 metre) long diversion channel for the Molonglo River at the Commonwealth Avenue Bridge site. The channel will be 100 feet (30 metres) wide and 10 feet (3 metres) deep, and will rejoin the river about 100 yards (91 metres) from Lennox Crossing.

29 March 1962

The first three precast concrete deck section were put in position yesterday. Vertical and horizontal stressing has begun. After the segments have been put in position on the temporary supports they will be jointed together with fine concrete.

Timber scaffolding will extend for the full length of the bridge next week.

Foundation work is complete except for Pier 2. Piers for the underpass bridge at the southern end were almost complete, ready for the deck beams.

15 June 1962

Works are proceeding on both sides of the lake bed.

Promontory areas are being built to the right and left of the northern end of the Commonwealth Bridge to provide picnic grounds and a small park.

The work on the hill opposite the Presbytery building is the landscaping of the area adjacent to the future extension of Commonwealth Avenue.

A concrete wall is being built along the southern shore of the lake. This will be finished with a white coping 2 feet 6 inches (0.8 metres) above the lake level to give a formal water frontage to the new Parliament House site. Filling material for roadwork around the lake is excavated from the hill behind this wall. The removal of this hill has provided an economical source of fill and allowed final landscaping to proceed. A large area of the hill is down to final level for landscaping this winter. [This was the hill in front of Old Parliament House]

6 July 1962

All bridge piers are completed, and about half the precast segments have been placed in position on the timber trestles.

The end segments or anchor units are being formed up at the northern abutment. Stiffening diaphragms are being poured above the piers and at two intermediate points in each span.

Most of the precast beams of the underpass bridge at the southern end of the main bridge have been placed.

10 August 1962

The piers and abutments for both carriageways have been completed and 124 precast concrete bridge segments forming the northern three spans have been placed in position on the timber falsework.

The precast concrete beams for three of the four spans of the southern underpass bridge have been placed in position on the bridge columns and the pouring of the concrete decking is proceeding. The beams for the final span will be put in position in the next few days.

To the north of the bridge the earth and shale filling has been built up to final road level.

The diversion channel has been partly constructed. One large section can be seen on the downstream side of the bridge site towards Lennox Crossing. Some work also has been done on the upstream section of the channel.

31 August 1962

The underpass at the southern end of the bridge is almost complete. All the prestressed beams have been placed, most of the deck work concrete has been poured and form work for the footway can be seen on the southernmost span of the structure.

8 September 1962

The last box girder segment was cast this week.

19 October 1962

The last box girder segment was placed in position on the timber falsework.

At each end of each bridge anchor blocks are being cast on the abutment roller bearings to form the ends of the bridge and to provide anchorages for the longitudinal stressing cables.

In addition to the precast segments, eight concrete segments are to be cast on top of roller bearings sitting on each of the bridge piers. Four of the eight segments over piers have been cast and the anchor blocks at the northern abutments have been completed.

30 November 1962

Casting of the segments in their final position over the piers has been completed and gaps are being filled with concrete.

Longitudinal, vertical and transverse stressing by steel cables is continuing.

Piles being driven just downstream from the existing wooden bridge are for a temporary low level bridge to allow the diversion road to remain open after the wooden bridge is demolished to permit completion of the northern approaches.

Concrete deckwork and kerb and gutter for the twin carriageway underpass bridge at the southern approach have been finished. Fixing of handrails will begin soon.

1 February 1963

The eastern carriageway is self-supporting. The first timber trestle has been removed.

Foundations have been placed for the 65 foot (20 metre) high granite-faced pylons which will flank the northern and southern entries to the bridge.

Two new temporary low-level bridges being built on the hospital side of the existing traffic diversion road clearly mark the route of the new diversion road. The road will allow normal traffic flow from both sides of the city along Commonwealth Avenue while the present high level timber bridge is being demolished.

A new, temporary 24 inch (0.6 metre) diameter water main is being laid along the line of the new diversion road. The present main crosses the Molonglo River and is supported by the old high level timber bridge.

7 March 1963

The old truss bridge will be dismantled tomorrow and traffic will use the new diversion road to the west of the truss bridge.

8 March 1963

The new bridge is completely self-supporting. Trestles have been removed from the eastern bridge and from the span of the western bridge under which the river will be diverted.

12 March 1963

The last falsework is being removed.

29 March 1963

Excavation work has begun for the new underground sewerage pumping station on the Regatta Point side of the bridge.

Excavation for the river diversion channel is well under way. The new diversion road has been completed and traffic diverted from the old trestle bridge. The temporary 24 inch (0.6 metre)  diameter water main which follows the diversion road was tested successfully and will be cut into the old main.

The first section of the concrete cantilever footway has been placed on the eastern
carriageway of the bridge superstructure.

Dismantling of the gantry has begun.

7 May 1963

Old Commonwealth Avenue truss bridge has been demolished.

31 May 1963

The lake bed is being excavated to its final level. The piles that supported the falsework will be removed when the excavation reaches them.

Excavation work is in hand prior to construction of the retaining wall near the southern approaches. The old river bed in the area of the northern approaches has been cleaned out. Rock fill from the site of the future National Library is currently being placed in this area and is being compacted and consolidated with sheeps-foot rollers.

15 June 1963

Precast decorative panels of exposed aggregate are being applied to the sides of the bridge, and will cover the sewer and water mains.

5 July 1963

The bridge is in fitting-out stages. All structural concrete has been placed on the eastern bridge and the cantilever footways are approaching completion on the western bridge. Kerbing and guttering on the eastern bridge are well advanced and the erection of hand rails will start next week.

Sewer and water mains are being laid in the open sides of the bridge. Some of the decorative aggregate panels used to cover the open sides of the bridge are in place on the southern end.

The earth embankments required for roadways have been completed and road pavement construction is in progress.

Soil is being removed from beneath the bridge to improve the waterway and this material is being used to build a parkland-type promontory on the northern approach embankment.

The smaller underpass bridge is almost complete and the handrails for this bridge can be seen in place.

25 October 1963

Finishing of the western carriageway nearly complete. Sealing of the approach roads has begun and the last sections of the aluminium handrails and lighting facilities are being put into position.

Granite slab facings are fixed to the recently completed pylons and other slab work on the abutments and footways will soon be finished.

The rock wall for the northern promontory is almost complete, as also is the placing of heavy protective "rip rap" stonework on the northern and southern embankments.