Golden Gate. "The weight of the roadway is hung from 250 pairs of vertical suspender ropes, which are attached to two main cables. The main cables pass over the two main towers and are fixed in concrete at each end. Each cable is made of 27,572 strands of wire. The total length of galvanized steel wire used to fabricate both main cables is estimated to be 80,000 mile. Each of the bridge's two towers has approximately 600,000 rivets." Here is a view from the top of one tower looking across to the top of the other, showing the lower end of the 'bow" of wires wound into bundles, which will be bound into bigger bundles, finally reaching each cable's finished diameter of 37 inches, each cable weighing about 12,000 tons! The completed bridge opened in 1937; the construction view above circa 1931. Panorama of the Golden Gate Bridge at night, with San Francisco in the background An original rivet replaced during the seismic retrofit after the 1989 Loma Prieta earthquake. A total of 1.2 million steel rivets hold the bridge's two towers together. Now look at these guy's bridge, opened 4 years after the Golden Gate, smaller, but still enormous by most standards, with cables only 17 inches in diameter! "The 1940 Tacoma Narrows Bridge, the first Tacoma Narrows Bridge, was a suspension bridge in the U.S. state of Washington that spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed into Puget Sound on November 7 the same year. This is probably the biggest and most famous non-fatal engineering disaster in U.S. history." The bridge bridge lasted only 4 months, during which time it earned the nickname "galloping Gertie". The original Tacoma Narrows Bridge roadway twisted and vibrated violently under 40-mile-per-hour winds on the day of the collapse. This video, if it comes up (won't embed), is rather unbelievable. You may need to play it manually by clicking the link. These builders' rivets were of dubious value! https://upload.wikimedia.org/wikipedia/en/d/d1/The_collapse_of_the_Tacoma_Bridge.ogv Edit: 40 mph winds doomed Tacoma Narrows Bridge; Golden Gate is designed to withstand 150 mph winds. The bridge has demonstrated the very best in Engineering ability.
Thanks for the post, @Frank Sanoica. . I can see the video. .. Holy mackerel ! Coincidentally, I was reading about the Silver Bridge collapse over the Ohio River, just a few weeks ago. That suspension bridge used I-bars, instead of cables. "On Dec. 15, 1967, the Silver Bridge in Point Pleasant, W.Va., collapsed during rush hour traffic, killing 46 people. NIST investigators found that the collapse was caused by a microscopic pit in the surface of a single I-bar that connected the deck to the suspension chain. Over time, the pit had grown into two small cracks about 4 mm in length, which led to the catastrophic collapse." There is a LONG VIDEO explaining how they determined the cause. But to make a long story short ... only two parallel I-bars were used at each connection. One I-bar fractured, and it started a chain reaction. Redundancy. That type bridge now has 4 pairs of parallel I-bar connectors. If one fails there are 3 others to take up the load.
@Nancy Hart Thank you for that! I never heard of such a construction method. It appears much faster, and cheaper, to put together than traditional I-beams and hot rivets. In fact, rivets were pretty much abandoned in favor of high-strength bolts (threaded fasteners). The hot rivetting had the unusual good point that after peining them in place they shrank as they cooled, making them hold pieces together even tighter, but without uniformity. I saw this in some movie as a kid; the guy heating the rivet threw it through the air, and the hammer-man caught it in a big metal funnel! Your image is devastating in appearance! Frank
The most impressive component of all suspension bridges is that which the public never sees: the CABLE ANCHORAGES! There is more material excavated for the anchorages than for the tower footings, and the mechanism for terminating the cables into their staybolts and anchor plates is something to see! Hal
In the case of the Tacoma bridge, it was thought that the culprit was a continued harmonic resonance which caused the collapse. Recently though, the science was actually proven incorrect and it is now believed that along with some bad calculations and cheaper building materials, that the aerodynamics of the bridge were the fault. It acted similar to an airplane wing and in essence (and very simplified) parts of the bridge wanted to “take flight”. Since the newer discovery of the real reason for the failure of the bridge to withstand sustained winds, bridge aerodynamics and bridge aeroelasticity are two new fields of study which are coming up with better ways to build bridges of any type.
The Verrazanno Narrows suspension bridge in New York, completed in 1964, has a span just 60 feet longer than the Golden Gate. There are 9 bridges with spans longer than these two bridges, 5 of them in China. That's all... Hal
The Tacoma Narrows suspension bridge failure was due to the design of the roadway support. Instead of see-through trusses, steel plates were used, furnishing a "sail" for the wind to push against, which led to the oscillations of the roadbed which tore the bridge apart. See the video of this disaster on YouTube, called "Galloping Gertie". Harold
Now this little bridge is one that took a some engineering and I dare say a little mountaineering........
Okay, I said it my way and you said it yours.....but.....here’s what Forbes has to write..... https://www.forbes.com/sites/starts...ever-about-why-bridges-collapse/#1a1075a01f4c
I wouldn't let a pet Hamster cross that thing! Those angled horizontal stays provide too much vertical loading on the walkway. Hal
Back to the Golden Gate Bridge; did ya know that it takes a crew of men about 4 years to paint the thing and then when it’s finished, they start all over. Talk about job security!