though the slides continue to evolve -...

For the past several days we have explored the impact of new materials: reinforced concrete and prestressed concrete through the lens of some of its chief practitioners Maillart in RC and Freyssinet and Finsterwalder in PC. Today we explore a particular bridge form: the cable-stayed bridge. This form has come to dominate the landscape for new bridges in the late 20th and early 21st century, let’s learn why and a bit more about its origins. Let us also examine the role of national styles on cable-stayed bridges and the various potential for play in the form in terms of aesthetics and appearance.

The story of cable-stayed bridges is typically told as that of one of German efficiency in the rebuilding after WWII, while that is an honest and important part of the history – the bridge form enjoys a richer past and a more complicated future as well.

To do

-Check against and mine the new Billington lecture on Cable stayed bridges

Notes

-The bulk of material used for this lecture was from an IABSE symposium,

though the slides continue to evolve

-2008, went 5 minutes long still! surprising. The american – japan – other stuff at the end does not work well, japan is too long, menn is unmotivated now that I have moved this lecture up (sunniberg comes to early!) bringing in some Schlaich is nice, Calatrava got some discussion from the MICA students... (unintended but good)

-2009, did what I could to improve it, the beginning is now pretty strong – the 2nd

half is weak. Need to add MASTAN images.

-2011, more cleanup it is getting better - still needs 1 or 2 days work to make it really nice - more compelling stories...

Cable-stayed bridges currently remain as a model of modernity. Here we see the Millau Viaduct

But they have a rich history

www.structurae.de

Saale River Bridge, Nienburg.

Source: Walther, René Ponts haubanées

Cable-stayed bridges are simple to construct and where a form being used in the early 19th century – but e.g. in Britain collapse of cable-stayed bridges over the Tweed and Salle rives in the early 19th century lead bridges builders away from cable-stayed forms. Combined forms generally with the suspension system dominant were found to be more stable.

Above we see the Salle River Bri. prior to collapse in a mild windstorm

Below, we see the Dryburgh Abbey Br. which replaced the collapse of the cable-stayed bridge with this hybrid form.

IABSE – Gimsing

Navier, 1823, Memoir on Suspension Bridges was based on his calculation and observation in Britain.

Ruled out Cable-stayed bridges and argued for suspension systems because

science: stayed bridges had collapse in England and the designs of Telford had not (in 1823)

socially: no economic advantage of the stayed system over the suspender system

symbolically: Cable-stayed forms in england led to Poyet an architect –as opposed to Telford’s (an engineer) Menai – which he preferred

His analysis shows the two major types of cable-stayed forms fan, and harp.

He was primarily concerned with the problems with embedding the cables in soil – a technique used little in modern cable-stayed bridges.

Haughs of Drimmie Bridge, c. 1830 Scotland105 ft spanDesigner = J. JusticeStill in service to this day, carries auto traffic for residential drivewayseveral similar bridges by Justice and family in this area.

Steve with owner William McCosh March 2000

IABSE – Gimsing, www.structurae.de Nicolas Janberg

Combinations of Cable-stayed and suspension forms continued throughout the 19th century.

Above: As witnessed by the 1873 Albert Bridge across the Thames in London

Below: or more notably by Roebling’s solutions such as the Brooklyn Bridge.

This form would be abandoned in the 20th century as suspension bridges would become a more pure form without the extra diagonals. (Yes they became more pure, but then had vibration problems which lead back to deep trusses or aerodynamics – maybe Roebling’s cable stiffening was and still is a smarter soluiton – worth thinking about)

Troitsky 1988 Ed.

As we begin to explore cable stayed bridges (and compare them to suspension bridges) keep in mind this key functional difference. The deck props the cables and thus is in compression as opposed to simply hanging in a suspension span.

Above: diagram of deck axial forces in a fan type cable-stayed bridge.

Emergence of cable stayed bridges in the 1950s depended on several technologies that had been developed as a result of prestressing...1. High strength steel cables (9-39 Sclayn Bridge prestressing tendons construction_150dpi)2. Hydraulic Jacking (9-41 Sclayn Bridge tendons testing_150dpi)3. Cantilever construction (9-58 Cantilever Bridge over Rhine_150dpi)

(maybe some more modern pictures would be better?)

Troitsky 1988 Ed.

The types of cables used is changing.

strand

rope

locked cable

Helical wound rope is wonderful but under high tensile strains may want to unwind causing a loss of some stiffness. locked wire strands designed to overcome this.


(plus indeterminate structural analysis (but maybe that is not a technology?)


IABSE - Gimsing

Between 1945 and 1954 nearly 200 mi (323km) of highway bridges were reconstructed in Germany.

IABSE - Gimsing

Strömsund Bridge (Sweden), which is generally regarded as the first modern cable-stayed bridge was designed by Dischinger. The bridge was of the three-span type, a system commonly used for suspension bridges, and it had a main span of 182.6 m flanked by two side spans of 74.7 m (Fig.4). The stays were arranged according to the pure fan system with two pairs of stays radiating from each pylon top. The steel pylons were of the portal type supporting the two vertical cable systems arranged on either side of the bridge deck. The deck girder contained two plate girders positioned outside the cable planes to allow an "invisible" anchoring of the stays inside the plate girders.

Advances in Structural Analysis played an enormous role in the development of this bridge form – as for the first time the proper cable forces could be determined for indeterminate structures. As well as a favorable distribution of dead load moments in the deck.

IABSE – Gimsing –

1957 – Fritz Leonhardt

After the Strömsund Bridge the next true cable-stayed bridge to be erected was the Theodor Heuss Bridge across the Rhine at Düsseldorf - opened to traffic in 1957 (Fig. 5). First in Germany.. With a main span of 260 m and side spans of 108 m it was considerably larger than the Strömsund Bridge. Also, the Theodor Heuss Bridge was more innovative by introducing the harp shaped cable system with parallel stays and a pylon composed of two free-standing posts fixed to the bridge deck structure.

AKA North Bridge (Billington): Actually not the most economical solution –arch proposals were 22% cheaper, but Germans wanted a new forward looking form (social!)

Visual disconnect below the pylons.

IABSE - Gimsing

The second cable-stayed bridge to be erected in Germany was the Severins Bridge in Köln (Fig.6). This bridge featured the first application of an A-shaped pylon combined with transversally inclined cable planes, and it was the first to be constructed as an asymmetrical two span bridge with a single pylon positioned at only one of the river banks. The cable system of the Severins Bridge was of the efficient fan shaped type, which is in good harmony with the A-shaped pylon. The cross section of the deck girder was essentially the same as used in the Theodor Heuss Bridge with two box girders connected by the orthotropic steel deck. Because of the substantial compression in the girder due to the one-sided arrangement of the pylon, the application of a steel deck was particularly advantageous in the Severins Bridge, as axial compression could be distributed over a large crosssectional area {Ben: this comment does not make sense to me you want steel for a large compression force, wouldn’t you want concrete?? Agreed this thought likely pulled from Gimsing and needs rethinking}. At both ends of the cable-stayed portion, the deck girder was made continuous into the adjacent box girder spans. Although one of the very first cable-stayed bridges, the Severins Bridge still stands as a most successful bridge. The

design of the pylon with its pronounced dimensions and the way the deck girder "floats" through the pylon constitute fine solutions to the design problems faced.

IABSE – Gimsing -- Homberg, 1962, Norderelbe Br. (picture from Troitsky)

The third German cable-stayed bridge, the Norderelbe Bridge at Hamburg, introduced the central cable plane with pylons and stay cables positioned in the central reserve of the motorway - a system that in the following years became the preferred system for the majority of cable-stayed bridges to be constructed in Germany - as well as in several other countries.

In some of its other design features the Norderelbe Bridge was more unusual, e.g. with pylons twice as high as required for structural reasons and with a cable system looking as if the main task was to support the pylon and not the deck girder (Fig.7). In the mid 1980s the Norderelbe Bridge had to go through a major rehabilitation program and as part of this the cable system was modified to a more sensible configuration. So today the Norderelbe Bridge is less peculiar in its appearance.

IABSE - Gimsing

1969 Kniebrucke, F. Leonhardt

In 1969 a notable cable-stayed bridge, the Knie Bridge, was opened to traffic in Düsseldorf (Fig.9). In this bridge the cable system was of the harp configuration with relatively few parallel stays, but in contrast to earlier bridges with the harp system, intermediate supports were added under every cable anchor point in the side span. This increased the efficiency of the harp system to such an extent that it was possible to use a very slender deck girder with an open cross section, i.e. with insignificant torsional stiffness. In the Knie Bridge an asymmetrical layout similar to that of the Severins Bridge was used with the pylon placed on one of the river banks only. Despite the considerable height of the pylon (114 m) it was possible to compose it of two free-standing posts without any struts or bracing to stabilize laterally.

IABSE – Gimsing

Multi-span cable systems. Homberg and the Rees Br.

The first two multi-cable bridges (lots of cables..) to be built were the Friedrich Ebert Bridge and the Rees Bridge both designed by H. Homberg and built across the Rhine. .... In the Rees Bridge two cable planes each containing a harp-shaped multi-cable system with 210 stays were used (Fig.8). Multi-cable systems lead to a more continuous support of the deck girder, and at the same time the cable forces to be transmitted at each anchor point are reduced, so that a local strengthening of the girder at the anchorages can be avoided. During erection advantages are to be found due to the much shorter deck cantilevers required to reach from one anchor point to the next, and in the final structure the smaller stay units will ease a replacement. These advantages would subsequently result in a general acceptance of the multi-cable system in almost all cable-stayed bridges. However, in that process it should later be realized that the multi-cable system also presented some disadvantages such as a higher vulnerability to excitations and increased total wind load on the cable system.

IABSE - Gimsing

The cable-stayed Köhlbrand Bridge in the port of Hamburg exhibits the first application of the multi-cable system in a bridge with double cable planes supported by A-shaped pylons (Fig.11). The modified fan system was one of high efficiency which gave advantages not only in the design of the final structures but also during erection as no temporary supports or temporary stays were required.

IABSE - Gimsing

F. Leonhardt involved in this bridge.

From the same period is another remarkable German cable-stayed bridge: the Düsseldorf-Flehe Bridge across the Rhine. Despite a main span length of 367 m it was chosen to build a two-span cable stayed structure with only one pylon on one of the river banks. This necessitated a pylon with a height of 150 m above ground. In contrast to the general German practice the pylon was made of concrete, and its lambda ( ) configuration was chosen to give support to the central cable plane with a harp shaped cable system in the side span and a modified harp in the main span. In appearance the pylon of the Flehe Bridge is not very harmonic, especially when compared to other, more recent - shaped pylons. Fig.11 The Köhlbrand Bridge.

IABSE-Gimsing

During the late 1950s and the 1960s a relatively modest number of cable-stayed bridges were built outside Germany and most of these bridges were based entirely on the German design philosophy. In the 1970’s and 1980’s the proliferation would occur.

How do innovations arise?

Pressing social need (15,000 bridges destroyed in the war) and a system that ultimately proved economical for intermediate spans.

How are innovations related to the culture in which they arise?

Truss bridges also would have worked (cheaper too!). Germans rejected old forms on aesthetic grounds, instead had an expressed desire for elegance (technic?) which led to experiments in new forms. Also, German design competitions led to innovation in systems

How did new technology influence the development?

Structural analysis innovations allowed for new confidence, but new

technology came primarily from construction desires..

IABSE-Gimsing



Pressing social need (15,000 bridges destroyed in the war) and a system that ultimately proved economical for intermediate spans.


Truss bridges also would have worked (cheaper too!). Germans rejected old forms on aesthetic grounds, instead had an expressed desire for elegance (technic?) which led to experiments in new forms. Also, German design competitions led to innovation in systems


Structural analysis innovations allowed for new confidence, but new

technology came primarily from construction desires..

Load Paths during constructioneach deck section creates tension in cable and compression in decka very simple statics problem

as construction proceeds outwards, compression builds up at tower end click to see plot similar to bottom figure of slide 10

Load Paths during usemultiple load paths make behavior (and analysis) much more complex

click to see example

deck in bending deforms, multiple cables share load (based on relative stiffness)cables at opposite end may actually see reduced tension if deck moves up

all gets even more complex for multi-span CS bridges, see later slides.

IABSE-Schlaich

Troitsky 1988 Ed.

1. Fan: max horizontal inclination = smallest steel needed, minimize axial force in deck, tough detailing top of tower, visual clutter?

2. Harp: Bending moments in the tower! horizontal movement issues, good stiffness for span, more steel than fan so usually choose higher tower

Troitsky 1988 Ed.

Use a few cables or use many? Modern systems have preferred to use many. By spacing the cables unevenly the cable tensions can all be approximately equilibrated.

Closer cable spacing means the deck can be more slender (but not too slender! as compression exists here)

Troitsky 1988 Ed.

Towers

Troitsky 1988 Ed.

Cable positions

1. Two vertical planes: Most common system, cable to girder arrangement influences usability (cable connection exterior or interior to girder)

2. Two inclined planes: Good lateral stiffness, cable arrangement limits torsional oscillations (due primarily to wind)

3. Single plane: Aesthetic, convenient lane separation, needs stiff torsional box in order to work effectively

Troitsky 1988 Ed.

Towers

Q: The pylon is a dominant structural feature of the cable-stayed bridge

much like the suspension bridge, what features of the pylon/tower lend

themselves towards structural art? C/C cable-stayed with suspension towers

Troitsky 1988 Ed.

Whether steel, as in Germany and most of the early cable-stayed bridges, concrete, or composite (steel + concrete), the main girder is typically composed of box sections which provide superior torsional resistance to the deck. In addition, since the deck is under compressive load the boxes are efficient thin-walled sections for carrying such load.

IABSE-Gimsing



Pressing social need and a system that proved economical

15,000 bridges destroyed in the war


Truss bridges also would have worked – Germans rejected on aesthetic grounds

Desire for elegance led to experiments in new forms

German design competitions led to innovation in systems (design-build)

German education emphasized form


No new science, lots of small technological steps… actually new technology came from construction desires..

IABSE - Gimsing

A remarkable exception from the German cable-stayed bridge traditions (and based on a very different design philosophy) completed already in 1962: The Maracaibo Bridge in Venezuela, designed by Riccardo Morandi. Here both the pylons and the deck girder were made of concrete, thereby introducing a structural material that had not earlier been used in the main elements of cable supported bridge superstructures. Furthermore, it was the first multi-span cable-stayed bridge. Each of these spans comprises a double cantilever supported by only one pair of stays radiating from a triangular pylon structure designed to stabilize the system for asymmetrical loads. Between the ends of the cantilevers small suspended spans are arranged, so that the system regarded as a plane system is externally determinate. The application of only one set of stays necessitated a heavy box girder to span from the pylon to the cable supported point, and during construction a large truss was required to support the formwork. The Maracaibo Bridge was later followed by two other major cable-stayed bridges designed by Morandi, the Polcevara Viaduct in Genova and the Wadi Kuf Bridge in Libya. However, all of the designs of Morandi were of such a personal style that they did not to any large extent serve as models for

the cable-stayed bridges of concrete to come.

IABSE-Virlogeux

Multi span systems bring specific challenges

IABSE-Virlogeux (designer of Millau Viaduct provides illustrations)

German model of flexible pylons snf flexible cont. span leads to lots of pylon deformation in multiple spans. (in single spans with two pylons you have anchors to ground in the back stays, but here the “back stays” just go into the next span which is flexibile!)

IABSE - Gimsing

one solution is to make the piers much stronger in bending, and thus capable of resisting the moments.

wikimedia commons from the web, and wikipedia entry from the web

Millau Viaduct, France over the river Tarn completed recently (December 2004)

Virogleux Engineer in collaboration with Norman Foster and Partners Architects..

Here it appears that (a) the deck has been made stiff and (b) the towers have been widened at their base see the pic on the right to handle the multi span problem

IABSE-Virlogeux

Alternative solutions to the multi span stiffness problem

IABSE - Schliach

Ting Kau Bridge, Hong Kong, completed 1998

The Ting Kau Bridge in Hong Kong is one of the few multi-span cable-stayed bridges ever built and, with 1177 m of cable-supported deck, it is one of the longest cables stayed bridges in the world. The bridge is one of a multitude of infrastructure projects for the new Chep Lak Kok airport, located on Lantau Island some 30 km from Hong Kong island. The design of this bridge contains special features such as single leg towers, which are stabilised by transverse cables just like masts of a sailboat. The Ting Kau Bridge and approach viaducts link the western New Territories and the mainland to an expressway called Lantau Fixed Crossing, which connects the new Airport with Kowloon and Hong Kong. It meets the Lantau Fixed Crossing on Tsing Yi Island only 500 m from the Tsing Ma Bridge.

Spans 127+448+475+127m

IABSE – Bergman

Construction considerations for cable stayed bridges deomsntrated here for the King Tau bridge. Note extra stays – remind us of Roebling’s Niagra Br.

American bridges do not “lead the way” the merely show the translation of this technology to the United States and also gives us a close look at challenges with the technology in cable-stayed bridge vibrations.

OK - I meant the modern era..

Some early cable stayed bridges in Texas...almost certainly the oldest “surviving” CS bridge in US Barton Creek 1890, 100 ft span, hand twisted cables, wood trusstowers and cable survive to this day

IABSE – Gimsing – source of text --- picture from Wikipedia

Sunshine Skyway, Tampa Bay Fl, 1987, Multi-cable fan arrangement, Figg Eng.

construction of cable-stayed bridges had been very low in North America during the 1960s and the early 1970s, but from then on the situation changed dramatically. In Florida a ship collision accident had given a clear indication of the inadequacy of the navigation opening in the 250 m long main span of the Sunshine Skyway. It was, therefore, decided to replace the existing two parallel bridges by a single bridge having a 360 m long cable-stayed main span. Two designs were prepared for the bridge, one based on a composite deck and two cable planes along the edges of the bridge deck, and the other as a pure concrete box and a single central cable plane. Both designs were put out for tender and the result showed a very close race between the two options. The final choice was to construct the concrete bridge according to a design based on the principles initially introduced during design and construction of the Brotonne Bridge in France. With its main span of 366 m the Sunshine Skyway was at its completion in 1986 the longest cable-stayed bridge in the USA (Fig 22).

Dames Point Bridge - http://www.mikestrong.com/dames/index.html -HNTB

In the USA the general trend throughout the 1980s was to simplify the design of especially the girders in cablestayed bridges. Within concrete bridges a good example on this trend is the Dames Point Bridge at Jacksonville in Florida. With a main span of 396 m the bridge surpassed the Sunshine Skyway as the longest concrete cable-stayed bridge in North America. The cable system of the Dames Point bridge is a multicable harp system supported by concrete pylons with a considerable flexural stiffness in the longitudinal direction. This gave the cable system very good deformational characteristics so that the girder could be made with a depth of only 1.5 m corresponding to 1/260 of the main span length. In principle the structural system of the girder in the Dames Point Bridge corresponds to that of the Alex Fraser Bridge, i.e. with two longitudinal girders beneath the cable planes and numerous transverse girders. However, in the Dames Point Bridge the longitudinal girders are made as solid concrete ribs with a depth of 1.5 m and a width of 2.5 m allowing a most efficient anchoring of the stay cables. Seen in comparison with the Pasco-Kennewick Bridge – the first major concrete cable-stayed bridge in North

America – the Dames Point Bridge clearly shows the simplifications in girder design.

Fred Hartman Bridge - Houston Ship ChannelStudied by Joe Main and Nick Jones -- cable vibrations!Shown here after retrofit..

http://www.deuring.ch/christian-menn/english/projekte_e/zakim_e.htm

a most forgiving view of Menn’s Bunker Hill Br. in Boston, employing cables to the outside of the deck and along the centerline from the same span, we will look again in the context of Menn’s other bridges.

A small criticism - you can drive parallel to the Bunker Hill Bridge. Uhm. On a little plate girder bridge. So did we need a large cable-stayed bridge here? No, it is a signature bridge to Boston’s Big Dig project but structurally it is not justifiable for its demands.

Under construction shot shows the silliness of this too

Later we will learn more about Menn the designer of this bridge and see examples in Switzerland of a very unique low slung cable stayed bridge, but today we leave Menn’s work behind.

IABSE - Gimsing

1977 the Rokko Bridge, the very first double deck cable-stayed bridge, was completed in Japan (Fig.24). The deck is made as a truss with a depth of approx. 8 m to give ample headroom, daylight, and fresh air on the lower deck. The cable system is of the multi-cable type with each stay composed of two parallel-wire, mono-strand cables.

IABSE - Gimsing

In a much larger scale the double deck concept was later used for the twin cable-stayed bridges, the Hitsuishijima and the Iwagurojima Bridges (Fig.25), that form a part of the Seto Ohashi between Honshu and Shikoku. Each of the two neighbor bridges has spans of 185 m - 420 m - 185 m. The traffic is running on a two level truss with a four-lane expressway on the upper deck and a double track railway (with provisions for a later addition of two more tracks) on the lower deck. The cable systems are of the modified fan configuration with two vertical cable planes positioned directly above the deck trusses. Thus, a high efficiency of the cable supporting for both vertical and torsional loading is achieved.

Billington has proposed that the towers reflect a cultural choice and pointed to samurai helmets as a motivation for the shape...

IABSE - Gimsing

The Japanese aesthetic is not as clunky as the double-deck bridges would lead one to believe.

An elegant cable-stayed bridge was completed in Japan in 1985 across the port of Nagoya, the Meiko Nishi Bridge (fig.26). Here the roadway is carried by a semi-streamlined box girder supported by two inclined cable planes radiating from the top of A-shaped pylons. With the chosen pylon shape and the fan shaped cable systems, the Meiko Nishi Bridge constitutes a fine example of a highly efficient cable-stayed bridge.

IABSE - Gimsing

The double deck configuration was again applied in the Yokohama Bay Bridge opened to traffic in 1989. With its main span of 460 m the bridge was only 5 m shorter than the Alex Fraser Bridge in Canada - at that time the recordholder amongst cable-stayed bridges. The truss of the Yokohama Bay Bridge has its top chord made as a 39 m wide and 3 m deep, streamlined box girder, whereas the bottom chord and the diagonals are of more conventional bluff box sections. The total depth of the truss is 12 m corresponding to 1/38 of the main span length. From the point of view of appearance the Yokohama Bay Bridge is quite successful as the truss is well-proportioned and the pylons have a clear and simple geometry (Fig.28). Eventually, the bridge will carry 12 lanes of vehicular traffic on two decks but initially only the upper deck has been opened to traffic.

IABSE-Schliach

Ting Kau Bridge, Hong Kong, completed 1998

Ting Kau Bridge

Location Hong Kong Type of structure Cable-stayed bridge; twin composite decks Owner/Client Hong Kong Highways Department

Completed 1998 Scope of our work Conceptual design, detailed design, site supervision Cooperation Binnie, Hong Kong

The Ting Kau Bridge in Hong Kong is one of the few multi-span cable-stayed bridges ever built and, with 1177 m of cable-supported deck, it is one of the longest cables stayed bridges in the world. The bridge is one of a multitude of infrastructure projects for the new Chep Lak Kok airport, located on Lantau Island some 30 km from Hong Kong

island. The design of this bridge contains special features such as single leg towers, which are stabilised by transverse cables just like masts of a sailboat. The Ting Kau Bridge and approach viaducts link the western New Territories and the mainland to an expressway called Lantau Fixed Crossing, which connects the new Airport with Kowloon and Hong Kong. It meets the Lantau Fixed Crossing on Tsing Yi Island only 500 m from the Tsing Ma Bridge.

Total Length 1177 m Main Tower Height 201,55 m Ting Kau Tower Height 173,30 m Tsing Yi Tower Height 164,30 m Deck surface 46000 m2 Deck cable steel 2800 t Structural steel deck 8900 t Reinforcement deck 90kg/m2 Reinforcement towers 200kg/m2 Spans 127+448+475+127m

IABSE-Schliach

IABSE – Schlaich

IABSE - Schlaich

Schlaich pedestrian bridges

Images of Alamillo, Chords (Jerusalem), and Margaret Hunt Hill (Dallas)

Much more to be said about these new incarnations of cable-stayed bridges.

IABSE - Gimsing

http://i39.tinypic.com/28u1d9f.jpg - Sutong BridgeJust NW of Shanghai

The construction of modern cable-stayed bridges in China initiated in 1972, relatively later compared with other developed countries. Up to now, more than 100 cable-stayed bridges have been built in China. It is still a high tide to build more cable-stayed bridges in the country, as in this period, a lot of bridges with a main span range of 300-900 m are needed. So, China will be ne of the hot places to build cable-stayed bridges in the next 2 decades. Based on the experience of cable-stayed bridges in China and other countries, we can expect that the main span of traditional cable-stayed bridges will go up to 1,200 m, reaching to its limitation. The hybrid system could be an optimal solution for bridges with a span length beyond 1,200 m. Cable-stayed bridges with composite decks and a span length less than 700 m is much cheaper than those with steel box decks. The aerodynamic stability can be greatly improved with additional aerodynamic countermeasures. Also serious wind/rain-induced cable vibration has occurred at several cable-stayed bridges in China, bridge engineers should pay more attention to this problem, especially for very long-span cable-stayed bridges.

7 of the 10 longest cable –stayed bridges are now in China... (weak ass source: http://en.wikipedia.org/wiki/List_of_largest_cable-stayed_bridges )

IABSE – Vejrum and Petersen

Spatial Cable System design proposal (architect model)

For the past several days we have explored the impact of new materials: reinforced concrete and prestressed concrete through the lens of some of its chief practitioners Maillart in RC and Freyssinet and Finsterwalder in PC. Today we explore a particular bridge form: the cable-stayed bridge. This form has come to dominate the landscape for new bridges in the late 20th and early 21st century, let’s learn why and a bit more about its origins. Let us also examine the role of national styles on cable-stayed bridges and the various potential for play in the form in terms of aesthetics and appearance.

The story of cable-stayed bridges is typically told as that of one of German efficiency in the rebuilding after WWII, while that is an honest and important part of the history – the bridge form enjoys a richer past and a more complicated future as well.

To do

-Check against and mine the new Billington lecture on Cable stayed bridges

Notes

-The bulk of material used for this lecture was from an IABSE symposium,

though the slides continue to evolve

-2008, went 5 minutes long still! surprising. The american – japan – other stuff at the end does not work well, japan is too long, menn is unmotivated now that I have moved this lecture up (sunniberg comes to early!) bringing in some Schlaich is nice, Calatrava got some discussion from the MICA students... (unintended but good)

-2009, did what I could to improve it, the beginning is now pretty strong – the 2nd

half is weak. Need to add MASTAN images.

-2011, more cleanup it is getting better - still needs 1 or 2 days work to make it really nice - more compelling stories...

This need to move somewhere closer to Menn...

http://is-beton.epfl.ch/Photos/Small/I/I34/I34-12.jpg

Chandoline over the Rhone 1989 – C. Menn

140m main span, slight horizontal curvature necisstitated the out-of-plane stays at the ends.

All concrete – including concrete trussing of deck

Tower/mast shape interesting but logical?

Sunniberg 1999

Ben: the towers are quite low, the cables quite vertical – what is the difference between low and high towers? A horizontal cable is pre-stressing – a cable going to a tower is cable-stayed... Where is the dividing line?

IABSE article

JSE Billington article

Pier, pylon, cables, and deck each designed to satisfy technical requirements and aesthetic requirements.

Pier(below road), pylon(above road): pier and pylon are integrated. Pier shape expresses the pier bending demands for live loading on one span.

Pylons are flared: (1) visually interesting, (2) allows cables to remain straight as deck curves (3) resists bending due to curvature for LL on 1 span

Cables: low slung = high tension, deck thickened near piers to resist compression there.

Deck: continuous thin line, no expansion joints, breathes laterally as needed

In the same valley as Salginatobel.

http://www.deuring.ch/christian-menn/english/projekte_e/zakim_e.htm: “The new Leonard P. Zakim Bunker Hill Bridge is the only one of its kind ever built. In addition to being the widest cable-stayed bridge in the world, the bridge will be the first "hybrid" cable-stayed bridge in the United States, using both steel and concrete in its frame. The main span consists of a steel box girder and steel floor beams, while the back spans contain post-tensioned concrete.”

lost in translation??

Bluff Dale Bridge 1890140 ft span, originally had a wooden truss, replaced with metal pipe truss in the 1899relocated several miles upstream, circa the 1960s

Engineering analysis has shown that these bridges have some very modern features and innovative ideas for the time1. Cables not anchored to deck--avoids putting horiz. tension in the truss2. Truss clearly designed to be supported by the cables--designers intended and achieved load sharing. 3. Cables continuous over the tower (the subject of a recent patent by Figg)

torroja on torroja

ahead of his time...

The first serious and somewhat anomalous 20th century cable-stayed bridge came from our Spanish innovator Torroja. Completed in 1925 the Tempu Aqueduct by Torroja used twisted cables of high tensile steel to eliminate piers in the water and an innovative pre-stressing system to solve the creep problems that would typically relieve the stresses in his cables.

torroja on torroja

Here we see the Tempul Aqueduct and Torroja’s description of the most basic structural system for a cable-stayed form.

Note, the compression forces in the tower.

torroja on torroja

Torroja designed internal jacks so that he could jack up the towers and insure that his cables stayed properly stressed.

Here we see Torroja as the innovator – but as in many cases – he was so far ahead of the science others did not follow this path.

Cable-stayed bridges would have to wait 20+ years for wide application and steel would be the initial material of choice.

Troitsky 1988 Ed.

Here we get some guidance on the appropriate angle to choose for the cables in a three span system. Only very shallow or steep systems are inefficient for stiffness.

Troitsky 1988 Ed.

The types of cables used is changing.

strand

rope

locked cable

Helical wound rope is wonderful but under high tensile strains may want to unwind causing a loss of some stiffness. locked wire strands designed to overcome this.

Troitsky 1988 Ed.

A significant economic innovation in the early orthortropic steel decks was the use of stiffeners underneath the deck that were integrated into the main structure. Stiffeners that provided closed sections are again preferred over those (a) that do not.

IABSE-Virlogeux

Multi span systems bring specific challenges

IABSE-Virlogeux

IABSE - Gimsing

EUROPE IN THE 80’s...

During the 1980s the activity within the field of cable-stayed bridges was considerably reduced in Europe compared to the previous decades, and most of the bridges built did not deviate much in size or design features from those already constructed. There were, however, a few exceptions from this rule. In 1984 the completion of the Barrios de Luna Bridge in Spain gave a further indication of the competitiveness of concrete as structural material not only for the pylons but also in the girder of cable-stayed bridges (Fig.19). With a main span of 440 m the Barrios de Luna Bridge surpassed the span of the Saint Nazaire Bridge by a margin of almost 10% and became for a couple of years the record-holder amongst cable-stayed bridges.

IABSE - Gimsing

The Farø Bridge in Denmark was opened in 1985 and it comprised a 290 m long main span supported by a central cable plane. The girder had originally been designed by the owner as a concrete box but an alternative bid based on a steel box proved to be competitive and was chosen for construction. The concrete pylons form a further development of the diamond-shaped pylons originally introduced in the Köhlbrand Bridge. Thus, in the Farø Bridge the lower triangle is extended all the way down to the water surface (Fig.20) rather than being supported on high pier shafts. Furthermore, the Farø Bridge showed the first application of corrosion protection of the box girder interior by dehumidification of the air.

IABSE Sham and Monster Netherlands

Not Schlaich – troubling aesthetics

Design of the Zwolle cable-stayed bridge. A combined cable-stayed and drawbridge form! Very unusual.

IABSE - Gimsing

Prior to the WWII (1938) Dischinger proposed a system in which the central part of the span was carried by a suspension system whereas the outer parts were carried by stays radiating from the pylon top. This system was proposed for a cable supported bridge with a 750 m main span to be built across the Elbe River in Hamburg. In connection with the reconstruction of German bridges after the war, the Dischinger system was proposed at several occasions (Fig.3) but it was never used for actual construction. One of the reasons is undoubtedly the pronounced discontinuity of the system both with respect to the structural behavior and to the appearance. The discontinuity reflects Dischinger’s discontent at the original Roebling system with its much more continuous configuration achieved by overlapping the multi-cable stayed system and the suspension system. In the publication of his own system, Dischinger categorically stated that the stays of Roebling's bridges had proved to be completely inefficient!

IABSE - Gimsing

1986 Fraser River, British Columbia

The potentials of the composite girder concept was clearly demonstrated during the construction of the Alex Fraser Bridge. Thus, the cantilevering from one cable anchor point to the next was easily accomplished by the relatively light steel girders, allowing the stay cables to be added before the heavy concrete deck was erected using precast slabs. At the same time the concrete slab could be efficiently utilized to transfer the axial compression induced into the girder by the horizontal components of the stay cable forces. The advantages of applying composite girders in cablestayed bridges should in the years to follow the construction of the Alex Fraser Bridge lead to a situation where this system was gradually being preferred for the majority of cable- tayed bridges in North America.

though the slides continue to evolve -...

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