Suspension Bridge

Item details


Name of item:	Suspension Bridge
Other name/s:	RTA Bridge No. 172, Northbridge Suspension Bridge, Cammeray Bridge, Long Gully
Type of item:	Built
Group/Collection:	Transport - Land
Category:	Road Bridge
Location:	Lat: -33.816944444444445 Long: 151.21249999999998
Primary address:	Miller Street, Northbridge, NSW 2063
Parish:	Willoughby
County:	Cumberland
Local govt. area:	Willoughby

All addresses

Street Address	Suburb/town	LGA	Parish	County	Type
Miller Street	Northbridge	Willoughby	Willoughby	Cumberland	Primary Address

Owner/s

Organisation Name	Owner Category	Date Ownership Updated
Transport for NSW	State Government

Statement of significance:


	The Suspension Bridge in Northbridge is of State significance. It was built as a steel suspension bridge with sandstone turreted towers by a private syndicate to promote residential development and was opened to traffic in in 1892. It was transferred to the Department of Main Roads in 1935 and rebuilt as a reinforced concrete two rib arch bridge, with original towers intact, in 1939. The bridge is intimately associated with the residential development of the area to the north of the bridge, essential infrastructure which allowed the area's development to proceed in the late nineteenth century. The process of the design and construction of the arch is illustrative of an era in the history of bridge building in the Department of Main Roads (DMR) and of contemporary concern with aesthetic and historical landmarks and their preservation. The bridge is a distinctive structure, both graceful and impressive, and situated in a highly attractive setting. The design of the arch demonstrates creativity in its response to a highly individual technical problem and in its aesthetic sympathy with the original towers of the suspension bridge. The concrete arch makes an important historical, technical and aesthetic contribution to the suspension bridge, which is already highly valued by the community, and is of considerable interest in its own right.
	Date significance updated: 30 May 11
	Note: The State Heritage Inventory provides information about heritage items listed by local and State government agencies. The State Heritage Inventory is continually being updated by local and State agencies as new information becomes available. Read the Department of Premier and Cabinet copyright and disclaimer.

Description


Designer/Maker:	J E F Coyle with input from Prof W H Warren (Sydney University)
Builder/Maker:	Concrete arch by Hornibrook Bros & Clark Pty Ltd
Construction years:	1892-1939
Physical description:	The original suspension bridge had a 500 ft main span supported by steel cables and steel hanger rods. The deck was stiffened by an undertruss which was pin connected at the centre of the span. The steel cables were supported on ornate sandstone towers and anchored into bedrock at each end of the gorge. The wooden deck carried two lanes of traffic plus two tram tracks and footways. Deterioration of the bridge due to corrosion led to the replacement of the suspension design by an arch in the 1930s. With a main span of 344 feet, the arch consists of two concrete ribs, peaking some 167 feet above stream level. Supported on the arches are columns carrying the deck on 14 reinforced concrete beam slab spans. The deck has expansion joints at the large piers directly over the arch springings. These also transfer wind load from the arch and deck back to the foundations. Connecting these to the original towers are 50 foot concrete beam spans. The concrete detailing was done in Gothic and Norman styles to reflect the Gothic sandstone towers, the main piers being given Norman castle features. As part of the reconstruction the roadway openings through the towers were increased to thirty feet, and walkway openings cut through the towers. The bridge has light standards supported by the concrete railings.
Physical condition and/or Archaeological potential:	Original condition assessment: 'Both the original sandstone towers and the concrete arch structures are in good condition. The towers show minor blemishes from leaching and there is some vegetation growth in need of removal. Concrete is generally in very good condition although some of the pedestrian railing areas have some vertical cracking. Close inspection of the arch was not possible, but the concrete appears in very sound condition. The original suspension system has been removed, and no evidence of the original anchorages was noted, but these may exist. The arch was supported during construction by timber trestles supported in turn by timber piles. As the area under the bridge has now been developed as playing fields with the creek carried in a culvert system, it is likely that any original piles would be well buried' (Last updated: 22/10/2003.) 2007-08 condition update: 'Fair.' (Last updated: 17/4/09.)
	Date condition updated:17 Apr 09
Modifications and dates:	Suspension system (which was corroded) was replaced by a concrete arch in 1937-39. Floodlighting was installed by Sydney electricity on 1992 Safety fencing was installed on the bridge in 2010.


Current use:	Road bridge
Former use:	Road bridge

History

Historical notes:

With the land boom of the 1880s, land to the north of Long Bay, Middle Harbour, was sold and resold. The North Sydney Investment and Tramway Company or the North Shore and Middle Harbour Land Company made major investments in the area and planned to build a tramway and a bridge across Long Bay gully in order to open up the area for sales of residential land. A suspension bridge across the gully was opened to traffic in January 1892. It had taken two years and nine months to complete and cost 42,000 pounds. With a suspension span of 500ft centre to centre of towers, it was considered one of the engineering wonders of Sydney and became a great tourist attraction. A toll of threepence return for adults and one penny for children was charged. The disastrous crash of 1892 saw both the above companies go into liquidation. The Depression of the 1890s slowed land sales and Northbridge did not develop as had been hoped; the tramway was not built. In 1912 the bridge was handed over to the Government as a gift, on the condition that a tramway be extended to the north side and no toll charged. The tramway was extended over the bridge in 1913/4, with its terminus in Sailors Bay Road. (http://www.willoughby.nsw.gov.au/help/library/Northbridge.htm) Between its construction and its handing over to the Department of Public Works, the bridge was little used and poorly maintained for many years. Repairs and some strengthening works were carried out in conjunction with the construction of the tramway. (Main Roads Journal, August 1937, p 152) The DMR assumed control of the bridge in 1935 and inspections soon revealed serious corrosion in the steelwork and cables, partly attributable to defects in the design of the bridge. For example, water had been allowed to accumulate around the suspension rods as they passed through the cross girder ends in small, undrained reserves that had originally been filled with a bituminous mixture, which had not stood the test of time. The main suspension cables were also found to be weakened by corrosion. The bridge was carefully monitored and it rapidly became clear that replacement or substantial rebuilding would be necessary. From several options, it was decided that a large concrete arch span to support the deck of the old suspension bridge was the most satisfactory solution. The towers themselves were in very good condition and were recognised by the DMR as having local significance as a landmark and tourist attraction and as having considerable historical value. For these reasons they were retained and repeated in the design of the new work, with much attention to sympathetic design. The arch was designed and tested through the analysis of models within the DMR. (Main Roads Journal, August 1937, p 152-155) The construction contract was awarded to Hornibrook Bros. & Clark Pty. Ltd. The bridge was closed to tram and vehicular (but not pedestrian) traffic and work began at the beginning of June, 1937. While a 'Melan' system using a steel rib to serve as falsework and then reinforcement in the completed structure had been considered, the tenderers favoured the conventional system of timber falsework, and it was this system which was employed. An interesting innovation, however, was employed in the form of steel cylinders with base plate partly filled with a fine dune sand and fitted with a hardwood piston. The pistons bore the weight of the girders until it was time to strike the falsework when two small screw plugs on the cylinders could be opened to a carefully prepared schedule, with a large team of operators working to signals, and sand released so that the crown and then, gradually, the whole arch took up its own load. Worker safety was also an important factor in the design of construction methods for the bridge. The bridge was re-opened to traffic in late 1939. (Main Roads Journal, August 1939, p 113-116)

Historic themes

Australian theme (abbrev)	New South Wales theme	Local theme
3. Economy-Developing local, regional and national economies	Technology-Activities and processes associated with the knowledge or use of mechanical arts and applied sciences	(none)-
3. Economy-Developing local, regional and national economies	Transport-Activities associated with the moving of people and goods from one place to another, and systems for the provision of such movements	(none)-
4. Settlement-Building settlements, towns and cities	Utilities-Activities associated with the provision of services, especially on a communal basis	(none)-
5. Working-Working	Labour-Activities associated with work practises and organised and unorganised labour	(none)-
8. Culture-Developing cultural institutions and ways of life	Creative endeavour-Activities associated with the production and performance of literary, artistic, architectural and other imaginative, interpretive or inventive works; and/or associated with the production and expression of cultural phenomena; and/or environments that have inspired such creative activities.	(none)-

Assessment of significance


SHR Criteria a) [Historical significance]	The bridge is intimately associated with the residential development of the area to the north of the bridge, essential infrastructure which allowed its development to proceed in the late nineteenth century. The concrete arch which was built 1936-9 is a fascinating episode in the bridge's history. The process of the design and construction of the arch is illustrative of an era in the history of bridge building in the Department of Main Roads. It is linked with the local historical theme of engineering and building the road system. The use of the concrete arch solution to support the older bridge and to allow its landmark features to be retained was a creative and heritage-sensitive response to an infrastructure problem in an era long before heritage values and processes were enshrined in legislation.
SHR Criteria c) [Aesthetic significance]	The bridge is a distinctive structure, both graceful and impressive, and situated in a highly attractive setting. The design of the arch demonstrates creativity in its response to a highly individual technical problem and in its aesthetic sympathy with the original towers of the suspension bridge.
SHR Criteria e) [Research potential]	The technical aspects of the arch's construction are well documented and the fabric of the bridge, with the associated documentation are of enduring technical and research interest.
SHR Criteria f) [Rarity]	The bridge is unique in NSW in appearance, and as a solution to a unique problem.
Integrity/Intactness:	Intact
Assessment criteria:	Items are assessed against the State Heritage Register (SHR) Criteria to determine the level of significance. Refer to the Listings below for the level of statutory protection.

Listings

Heritage Listing	Listing Title	Listing Number	Gazette Date	Gazette Number	Gazette Page
Heritage Act - s.170 NSW State agency heritage register

Study details

Title	Year	Number	Author	Inspected by	Guidelines used
Pre-1948 RTA Controlled Concrete Slab and Concrete Arch Bridges in NSW	2004		Burns and Roe Worley and Heritage Assessment And History (HAAH)		Yes

References, internet links & images

Type	Author	Year	Title
Written	Department of Main Roads	1939	Main Roads
Written	Department of Main Roads	1937	Main Roads
Written	Willoughby Council website –		http://www.willoughby.nsw.gov.au/help/library/Northbridge.htm

Note: internet links may be to web pages, documents or images.

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Data source


The information for this entry comes from the following source:
Name:	State Government
Database number:	4309506

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