Australian Bridges: 7. Lloyd's Bridge, Yungaburra

The last three bridges are all located in Australia's largest city, Sydney. The next two are from further north, in Queensland.

Head inland from the north Queensland coast to find the delightful historic town of Yungaburra. One of the attractions here is the walking track along Peterson's Creek, from where it's possible to see platypus and tree-kangaroos (although not when the Happy Pontist visited).

In 2008, local man Lloyd Abell provided funding for a new bridge to connect the walking trail across the Creek, a structure now and hopefully forever known as Lloyd's Bridge. There's a commemorative plaque on one of the bridge masts, and an explanatory sign nearby.

The suspension footbridge spans 30m over the creek. A sign makes clear that the maximum load is 10 persons - this is not a bridge suitable for the absurd 5 kPa of normal footbridge design, nor should it be.

The bridge comprises a deck of longitudinal planks supported on timber cross-bearers. These are suspended via 8mm hangers from the 16mm main cables. A cable in a rough plastic sheath is clamped to the hangers to form the handrail and to hold up mesh infill balustrades.

The main cables are anchored into turpentine poles forming the bridge towers, and then into concrete anchorage blocks.

Some people may wonder why I'm covering such a seemingly minor structure and non-notable structure here. Well, firstly, I just have a soft spot for small-span pedestrian suspension bridges. Secondly, I think they illustrate how much variety is possible even with a seemingly small niche. If you look at the minor details on this and similar bridges (how the main cables attach to the tower, or how the hangers attach to the main cables), you'll find every one is different, and I think there's endless fascination in seeing how others have solved the same problems in such a variety of different ways.

The bridge lacks stiffness and moves considerably under load, but the mesh balustrades effectively damp vibration. The bridge creaks very noticeably when used, the level of noise being proportional to the success of the damping, and therefore reassuring, to a structural engineer at least.

It's a pragmatic structure, blessed with a minimum of design, and well done.

  

  

Further information:

• Google maps
• Weekend Notes

Australian Bridges: 6. Parsley Bay Bridge, Sydney

This charming suspension footbridge is tucked away in a quiet eastern Sydney suburb, little known to most of the city's residents let alone anyone else.

According to a history published online by the local municipal council, plans for a bridge across the beautiful Parsley Bay were first discussed in 1906, with the structure in place by 1910.

The bridge was designed by local town clerk and engineer Edwin Sautelle, and cost the tidy sum of £500 to build. Reportedly, it was built to improve access to ferries via the nearby Point Seymour.

The bridge is predominantly a timber structure, with the towers, deck and parapet rails all timber. The other parapet elements are in metalwork.

The towers are A-frame in form, which provides good stability in the longitudinal direction, but the bridge is evidently less stable laterally. Tie-back cables have been installed on all four corners, presumably to reduce lateral sway.

The bridge appears to have changed very little over its lifetime, judging from old photographs, although an image in Pictorial History Eastern Suburbs indicates that lamps or ornaments once sat above the bridge pylons. The same image doesn't appear to show the tie-back cables, although these can be seen in a postcard from circa 1930.

The other main change over time appears to have been the steady growth of surrounding vegetation.

The bridge was repainted and repaired in September 2003, and a further refurbishment was completed by GPM Constructions within the last couple of years.

The bridge's main asset is its beautiful setting. The Parsley Bay reserve features a fine sandy beach with water protected by shark netting, as well as a small patch of rainforest towards its rear. Views from the beach and from the bridge are both very attractive.

It seems to be a popular spot for bridge-jumping, although signs on the bridge make clear this is prohibited.

Further information:

• Google maps
• Structurae
• Bridgemeister
• Weekend Notes
• History of Parsley Bay Reserve
• Australia for Everyone

Australian Bridges: 5. Napoleon Bridge, Sydney

There is plenty of development going on in Sydney, with a prominent site being the Barangaroo area, which sits along the harbour-side north-west of the central business development, and north-east of Darling Harbour.

The southern end of the site has already seen a number of new buildings completed, while the northern end is home to Barangaroo Reserve, a public park with fine views. Between the two, work continues, and will include the Wilkinson Eyre-designed Crown Sydney Hotel.

Barangaroo is separated from the city centre by a number of streets and particularly the elevated Western Distributor Highway. Finding a way through can be like negotiating a concrete maze.

The new Napoleon Bridge, designed by Wilkinson Eyre and Arup, provides one point of connectivity. It's a covered footbridge spanning the busy Sussex Street. It opened in late 2015, and received an ASI Steel Excellence Award in 2016.

The bridge takes its name from adjacent Napoleon Street, which in turn owes its name to the former presence here of Frenchman Francois Girard, who was at various times soldier, teacher, convict, baker, miller, merchant and farmer.

Napoleon Bridge connects at two different levels: at road level to the west and at an elevated level to the east. The level difference is addressed through two escalators and a staircase at the west end.

The span of the bridge over the highway is a slightly odd structure, comprising two steel edge girders connected by chevron-shaped crossbeams, which support a ribbed floor. The edge girders are shaped to resist a maximum bending in the middle, rising visibly above the floor level on either side.

The roof and walls which shelter the walkway are supported on a series of steel portal frames, arranged so that they are perpendicular to the upper surface of the edge girders, rather than vertically. The outline of the portals is crisp and clear.

The ends of the deck girders are quite shallow, and noticeably shallower than the western approach span, which houses the staircase and escalators. There's an awkward piece added to the girder steelwork to visually address the difference in depth of the two edge elements - I don't think it works very well.

The walkway roof continues horizontally above the staircase area, creating a yawning open-ended atrium. I think this is visually effective, a funnel-like portal which announces arrival into the Barangaroo area.

I like the way that it leans out, giving it a visual presence from side alleyways and sense of dynamism. This is a bridge for city-dwellers briskly on the move, not a bridge for flaneurs or ponderers.

One oddity to the roof structure is that it is not fully enclosed, being partially open on the north edge. I'm not sure why this is, but it begs the question as to why this bridge is covered at all.

The answer, I think, can only lie in the Australian obsession with vandalism risks, as most other footbridges above their highways seem to be "adorned" with massive tall anti-vandalism fences. These are normally a hugely disfiguring feature, so it's good to see the issue dealt with in a much more integrated manner here.

Napoleon Bridge sits in a very difficult site, hemmed in by tall buildings and surrounded by street clutter. The temptation for a designer in this setting is to opt entirely for modesty, to avoid adding further to a visually overwhelming environment. I think it's to this bridge's credit that it combines an appropriate degree of restraint with just about the right amount of excess presence.

There are details that can be picked at, such as the awkward structural junction above the support piers, or the disappointingly small extent to which the edge girders are visible above the floor seen from inside the bridge.

Overall, however, it's an appropriate and well-considered design.

Further information:

• Google maps
• Speirs and Major
• City Walk Bridge, Barangaroo, Sydney

Australian Bridges: 4. Pyrmont Bridge, Sydney

My next few posts will cover a handful of bridges in Australia.

The best known bridge in Sydney is clearly the Harbour Bridge, but it's not the only historic engineering landmark in the city.

The Pyrmont Bridge is designated a National Engineering Landmark by the Institution of Engineers of Australia. It is a bridge rich in history and technical interest, and I can only scratch the surface here. I'd particularly recommend the original paper on the bridge in the ICE Proceedings (1907) and a series of articles in The Engineer (1917), the latter of which include excruciating detail in the form of description, drawings and photographs. There is an excellent history of the bridge in the document proposing the bridge as an engineering landmark, all links can be found at the end of this blog post.

A timber toll bridge crossed the Darling Harbour, dating from 1858, operating at a lower level than the present structure and incorporating a swing span. The replacement bridge was completed in 1902 to a design by Percy Allan, and was built at a higher level. Allan designed the bridge for the local public works department after a design competition had been held and all 41 entries had been rejected.

It was built as a highway bridge, being closed to highway traffic in 1981 following the construction of new highway viaducts nearby. The bridge was partially refurbished in the 1980s, reopening as a pedestrian boulevard in 1988. The bridge carried the Sydney Monorail from 1988 to 2013. The paper by Trueman linked below describes the refurbishment work.

The bridge is generous in proportion, originally accommodating a 40-foot wide carriageway and two 7-foot wide footways. The two central spans comprise cantilevering steel truss girders supported via an array of roller bearings on a central caisson pier. The steel was supplied from Belgium, with Australia lacking any significant steel industry at the time. However, all the approach spans are built as a variant on Howe trusses using Australian ironbark timber, primarily to save on construction cost, with the total price being roughly half what an all-steel bridge would have cost.

When built, the bridge was immediately recognised for its engineering significance. The opening spans were larger in area than the vast majority of moveable bridges built previously, and it was thought to be a pioneer in the use of electric power for its operation. The bridge is operated from a single control cabin at the centre of the opening section, with power supplied by cables running below the harbour bed. The cabin appears largely unaltered, although it was relocated to the edge of the bridge when the monorail was added.

The main perception at deck level is of generosity of space. It's unlikely a pedestrian promenade this wide would ever be built as new, it's purely a legacy of the bridge's historic use as a road bridge. Now there is space for banners, for people to admire the views of the harbour to either side, and for walkers, cyclists and roller-skaters to coexist reasonably happily.

Seen from below, the bridge appears in good condition, although I understand it is subject to an ongoing maintenance programme (BIM-empowered). When it was converted for pedestrian use, an extensive study into its defects and repair requirements was made. The engineers proposed the use of preservative treatment for the timber, but this was not immediately undertaken due to cost. The bridge was reassessed and only those repairs strictly necessary for safety reasons were completed: other damaged timber was left to continue to deteriorate. During a subsequent ten-year maintenance programme, timber preservatives were installed, both diffused into the timber core and applied as a barrier to the timber surface.

The timber trusses appear to have been overpainted at some stage, a largely cosmetic treatment for such a structure, I would think. The various connections are clearly visible. I believe some of these were altered during the 1980s restoration in order to locate connecting bolts in less damaged parts of the timber.

The west end of the bridge appears largely unaltered, with impressive stone approach structure. The east end has been more significantly altered, presumably because the bridge was cut short when the Western Distributor Highway was built. There are now escalators down to quayside level, and a cable-stayed footbridge provides a higher-level extension for those wishing to continue over the highway.

Overall, it's great to see that a bridge which was originally built as a cut-price alternative to other designs has survived so well, and I don't think engineers at the time of construction would have expected it to last so well. It has survived a variety of major changes in use, and its continued value as a key link in the Darling Harbour surrounds should hopefully ensure it survives for a long time to come.

Further information:

• Google maps
• Wikipedia
• Structurae
• NSW State Heritage Inventory
• Pyrmont Bridge, Darling Harbour
• Sydney Architecture (includes several historic and construction photos)
• The New Pyrmont Bridge (Sydney Morning Herald, 1902)
• The Pyrmont Bridge, Sydney, New South Wales, Proceedings of the Institution of Civil Engineers (Allan, 1907) (and Discussion)
• Pyrmont Electric Swing Bridge (The Engineer, 27 Jan 1917, 2 Feb 1917, 9 Feb 1917, 16 Feb 1917)
• Spanning Two Centuries: Historic Bridges of Australia (O'Connor, 1985)
• Pyrmont Bridge - Construction and Restoration (Trueman, National Conference on Engineering Heritage, 1988)
• Proposal to Landmark the Pyrmont Bridge, Darling Harbour, as a National Engineering Landmark (Institution of Engineers of Australia, 1991, this includes copies of several other key papers regarding the bridge)
• Management of an engineering landmark bridge: Pyrmont bridge, Darling Harbour, Sydney (Higgins, Bridge Management 2, 1993)
• The cabin man on Pyrmont Bridge (Sydney Morning Herald, 2014)
• Pyrmont Bridge (Kishan, ICE Australia, 2014, essay as part of the Bridge Ahoy! tour)

Shortlist announced for New Danube Bridge competition

The shortlisted entrants have been announced in a competition to design a new road bridge over the River Danube in Budapest, Hungary. The new bridge will provide a long-planned connection to the south of the Budapest city centre, and a bridge is being sought which is structurally efficient, architecturally high-quality, and innovative in design.

The 17 shortlisted teams are:

• Arhitektura d.o.o. & Ponting d.o.o.
• CÉH Tervező, Beruházó és Fejlesztő Zrt
• Explorations Architecture & COWI UK Ltd
• FHECOR Ingenieros Consultores & DISSING+WEITLING architecture *
• Főmterv Mérnőki Tervező Zrt
• Knight Architects & Ove Arup and Partners *
• Lavigne et Chéron Architectes, Bureau d’Etude Greisch, Közkekedés Engineers, Geovil *
• Leonhardt Andrä und Partner, Beratende Ingenieure, Zaha Hadid Architects, WERNER Consult, Smoltzcyk and Partner *
• Marc Mimram Architecture & Associes
• Mott MacDonald with Brownlie, Ernst and Marks *
• NEY + Partners BXL S.A.
• Pont-terv Mérnöki Tervező és Tanácsadó Zrt
• setec tpi, Wilkinson Eyre & Terrasol *
• Speciálterv Építőmérnöki Kft
• Unitef-83 Műszaki Tervező és Fejlesztő Zrt
• Van Berkel en Bos U.N. Studio B.V. & Buro Happold Consulting Engineers P.C
• Uvaterv Út- Vasúttervező Zrt

The selection process was interesting: twelve teams were pre-selected by the competition organisers. All but one of these made it past the pre-qualification hurdle.

A further six entrants have survived a competitive selection process, being ranked the highest scoring out of an undeclared number of additional entrants - I've marked these with a * above. This part of the selection process appears to have been somewhat odd, entrants being ranked according to the quantity of professional certificates and prizes they can demonstrate across a range of relevant projects and team experts. It seems a process calculated to bring in big names rather than simply the most creative designers.

The 17 shortlisted teams have until 5th January to develop and submit their designs, and will each receive a 40,000 euro stipend to support their efforts. Results of the competition are due to be announced on 8th March 2018, and prize money is available for the three top entries plus three additional runners-up. The total budget set aside by the promoter for all of this is €910,000.

The generous funding is matched by the size of the 21-member competition jury, so the overwhelming message appears to be how seriously the organisers are taking the exercise.

I anticipate that the competition entries will be made public in due course, so I'll look forward to discussing them here in due course.

Structural Awards shortlist announced

The Institution of Structural Engineers has revealed the shortlist for the 2017 Structural Awards.

Of particular interest here are the Vehicle Bridges and Pedestrian Bridges categories. I've visited one of the three shortlisted vehicle bridges, but none of the others.

Elsewhere in the Awards, the very innovative ElevArch system is shortlisted under four separate categories: Structural Transformation, Construction Innovation, Outstanding Value and Sustainability.

Winners will be announced on 17th November.

Yorkshire Bridges: 17. Link Bridge, Eyre Lane, Sheffield

I'll finish off this set of posts regarding bridges in Sheffield with a little thing, a link bridge which spans across Eyre Lane.

This links two sections of Sheffield Hallam University, the Arundel Building and Charles Street Building.

I don't know who the structural engineer was, but the architect is Bond Bryan Associates, collaborating with Corin Mellor of David Mellor Design, who are much better known as a designer of cutlery than of bridges. The Mellors once had a workshop on the site.

The bridge combines three materials: glass for the side elevations, weathering steel for the roof and floor, and stainless steel for the decorative ribs.

There's not a great deal more to say: it's short, and it's sweet.

Further information:

• Google maps
• Public Sector Build Journal