Bosphorus Bridge

[hokie66]

Does anyone know why the deck hanger cables on this bridge were inclined or zig-zagged? The second Bosphorus bridge has vertical hangers.

Just wondering, as I had the pleasure of seeing these bridges for the first time recently.

http://en.wikipedia.org/wiki/Bosphorus_Bridge

 

[IDS]

The triangulated hanger cables were used by Freeman Fox (now Hyder) on a number of long suspension bridges in the 70's and 80's, starting I think with the Severn Bridge and including the Humber Bridge, which was the World's longest span for many years. They were said to be a great innovation at the time, but I believe they have fatigue problems.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[bridgebuster]

Triangulated, inclined, diagonal, or zig-zag hangers aren't new. The Brooklyn Bridge has a dual system; other 19th C. bridges also used them. D.B. Steinman discuss these variations in his book (he didn't seem to be keen on them).

Their purpose is to control vertical deflection while minimizing the stiffening truss depth.

As IDS pointed out there are fatigue concerns with these types of arrangements.

 

[hokie66]

The Brooklyn Bridge is a hybrid...suspension bridge with secondary cable stays. The Bosphorus, Severn, and Humber bridges all use this curious (to me) herringbone scheme. The wiki article on the Severn bridge says it was an attempt to limit vibration. I wonder if it worked.

 

[bridgebuster]

On the Brooklyn Bridge, the stay cables are acting as primary members.

 

[concretemasonry]

Those are certainly magnificent structures in a historically active area(seismic and very heavy traffic).

With only two bridges separating Europe and Asia in a city of 12,000,000 with very, very heavy traffic daily in spite of staggered travel times and alternating lanes. They are planing another long span bridge north of the other two. It will be interesting to see what is selected for the new bridge.

From an engineering standpoint, the area has been seismically active during the past years and the bridges span a major fault in addition to connecting two continents at the cross-roads of the world in all directions that previously occupied the area.

They are also currently building a tunnel over the active fault and under the Bosporus that connects the Black Sea (oil and cargo shipping) with the opening to the Mediterranean Ocean and the rest of the world. It is currently behind construction because of the unanticipated finding of centuries of ancient civilizations. According to my friend that is involved, the engineering is under control so far, but the historic delays are frustration.

IOt is an engineering challenge in a very developed country.

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[hokie66]

bridgebuster,
Correction noted. That was sloppy useage on my part.

 

[bridgebuster]

no problem Hokie