An Overview of the Bridge and its Approaches

From Engineering Heritage New South Wales

A ‘birds-eye’ view of the bridge and its approaches

    The drawing is clearly dated 30 September 1921 and is signed by JJC Bradfield but must have been reworked much later. The road across the bridge is named ‘Bradfield Highway’ but this name was not bestowed until 1932. In North Sydney the tramway is shown connecting to the bridge. This was a late design change in the 1930s. The bridge itself is an arch but this was not even allowed for until 1923, and the detail of the trusses as shown with 28 panels is not the design included in the modified tender documents. Those plans had a 33-panel truss with the odd centre panel counter-braced. There are five Warren truss approach spans on each side of the main span. The tender documents, even the 1923 arch proposal, had only four. Without the date at lower right the best guess of a date would be March 1932!

    Whenever drawn the image gives a good overview of the bridge and its connections. From extreme top right the existing North Shore line passes through Waverton station. The original 1893 line to the Milsons Point ferry terminus descends to the water’s edge in a wide loop around the end of a ridge. The original interchange wharf was virtually at the site of the northern abutment tower of the main arch span. The temporary station is shown, far enough back to allow the construction of the huge bridge workshops on its former location, shown as blank in the drawing.

    A new route is carved through North Sydney, tunnelling under the ridge with the new station in a deep excavation. From this point massive retaining walls and bridges, which would be individually remarkable except that they are adjacent to the overwhelmingly large steel arch, carry the now four lines increasingly above natural ground level, through a new Milsons Point station and onto the high bridge deck. Just north of North Sydney station, towards the right-hand edge of the page, two lines of the ‘Mosman, Manly, Narrabeen’ railway have made a junction with the North Shore line in the tunnels within the hill. At a very late stage when it was clear that this railway would not be built soon, its route across the bridge was given over to trams and the lines are shown entering the ‘railway’ alignment from Blue Street.

    Once across the bridge the four lines use four high-level platforms at Wynyard. Two lines continue off the page to the left towards Central Station at the other end of the city and two diverge east (down the page) to cross the city diagonally and eventually reach the southern suburbs These tunnels were not built beyond Wynyard. Below the high level ‘Shore’ platforms two low-level platforms serve the City Circle which has looped under the city and on a viaduct across Circular Quay from St James which is shown at the extreme left. Trains reached St James in 1926 but were not extended to Wynyard until 1956.

    Also at St James are shown two tracks between the City Circle platforms. These serve an inner loop with a station under O’Connell Street before reaching Town Hall which is beyond the drawing. South of St James, off the page to the left, the route would have entered the city from the eastern suburbs. All the necessary ‘flyover’ tunnels and the four platforms were built, and abandoned tunnels still exist as far as the point of divergence beneath the Botanic Gardens near where the inner loop is seen to pass under Macquarie Street.

    At the city end the roadway across the bridge ends in a roundabout serving Kent, Clarence and York Streets. In 1932 the bridge, and presumably the roundabout, had no lane marking!

    The work done between 1916 and 1918, as far as it is shown in this drawing, was limited to the City Circle tunnels immediately east of Circular Quay looping through the Botanic Gardens in front of Government House and around the Conservatorium of Music. Very minor works, little more than site clearing, were also undertaken near Harrington Street between Circular Quay and Wynyard. Although at this time the bridge was still years away from even the invitation for tenders, spoil from the tunnel works was tipped to form embankments on what would be its approaches.

Source: SARA NSW NRS 12685

    The cantilever bridge as it was envisaged on 14 November 1922, as signed and dated by Bradfield at lower right. Note the grand building built over the deck at the southern end as an entrance portal to the city. The straight back-spans of the cantilever made the approach spans shorter, but on the northern end made the curve towards North Sydney and the existing railway much tighter. The attraction of the cantilever was probably the straightforward and well-practised method by which it could be built out piece by piece over the harbour once the back-spans had been completed on falsework easily supported on the land below. Falsework across the harbour was obviously very difficult if not impossible. It was only after the concept of building half arches as cantilevers stayed back by massive cables into the bedrock of the approaches, (developed by G C Imbault in 1905 for the bridge over the Zambezi River at Victoria Falls), was considered that the arch design became possible. It was cheaper, as the heavier section of the bridge without the back-spans was much shorter. More approach spans were needed but they were relatively light and cheap.

20 November 1916
Source: SARA NSW NRS 16669-01001

    The general concept of the Sydney Harbour Bridge at its present location had been adopted by Bradfield long before the formal process of its construction began in 1921. To dispose of spoil from the tunnel work on the City Circle railway in 1916 a tip was established on what would be the bridge approaches. The street in the foreground is George Street North. The higher street is now called Cumberland Street, though then called York Street North. The retaining walls and stairs still exist, now with the bridge soaring above. The tip site is approximately the site of the offices of ‘BridgeClimb’ which conducts tourists to the top of the arch. The photo is precisely dated to 20 November 1916, and as was the method of the age, the spoil is being carried by small horse-drawn wagons.

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