17 replies to this topic

[Kelly]

Golden Gate

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[Kelly]

Suspension cable cross section has 61 strands with 452 wires (shiny dots in image) in each strand for a total of 27,572 wires. Weight per foot is 3400 lbs.
The strands are compressed and the cable is wrapped with a wire to keep its shape. Sign bracket is bolted to suspender rope support clamp.

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[floridaskier]

that is one fat cable.

Is that the same Roebling as the lift maker?

[Bill]

Yep.

[KZ]

Pretty cool bridge. In the first picture you see fort point, which guarded the bay before the bridge was built, and to the left of the bridge is Marin Headlands, a former military base to protect the bay area. Quite a cool place to go and spend a weekend afternoon.

[liftmech]

floridaskier, on Apr 1 2004, 01:08 PM, said:

Is that the same Roebling as the lift maker?

I believe Roebling built more bridges than lifts, it's just that he was prominent in the wire rope industry at the time and that's who was building the lifts. (American Steel and Wire ring a bell?)

[SkiBachelor]

Roebling only built 12 lifts in its time, while American Steel & Wire built I think 8. I think American Steel & Wire sold its patent for chairlifts and went into something else. Does anyone know that company because I can't find it in my SAM chairlift chart.

[liftmech]

American Steel and Wire became a highly respected and prolific lift company known as Heron. Bob Heron bought AS&W's lift division when they decided to get out of the business (he was already working on his own designs at the time, if I'm not mistaken).

[Kelly]

This link is to a PBS show on the Golden Gate.
Balancing Forces link shows simple engineering concepts that are also used on ski lifts.

http://www.pbs.org/wgbh/amex/goldengate/sf.../sf_forces.html

This is the people link. It tells the story of Charles Ellis the main engineer and Joseph Strauss the "Front Man" for the project who later fired Ellis.

http://www.pbs.org/wgbh/amex/goldengate/pe...ts/p_ellis.html

If you click on the forward arrow on the Charles Ellis page it will bring you to the Leon Moisseiff page, he was also famous for engineering the Tacoma Narrows Bridge.
Direct link to that page:

http://www.pbs.org/wgbh/amex/goldengate/pe..._moisseiff.html

Ryan B

[Bill]

Was that before the fall or after the fall? :) (The Tacoma Narrows Bridge)

[floridaskier]

Wow, I didn't know it collapsed only 4 months after they built it. That video was amazing, we watched it in school last year

[Bill]

Here are some Narrows Pics from my neighborhood:

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[Bill]

And another from mid-deck:

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[Bill]

Here is the Gig Harbor side of the Narrows, the crane to the left is the start of the anchorage of the Gig Harbor side of the Second Narrows Bridge.

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[Bill]

From a distance, you can see the barge where they are working on the caissons for the second Narrows Bridge.

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[Bill]

I decided to move this to Off-Topic even though it isn't, this topic is a grey area. :)

[KZ]

Cool. I will try and take some pictures of the cable car museum in san francisco tommaorw, i remember it being pretty interesting so we shall see. I will get some of the bridge as well.

[Kelly]

Moisseiff was "the" Chief Engineer of the first Narrows Bridge.
Other interesting items:
Original steel in the old bridge was salvaged and used in the war effort. That included "unwrapping" the suspension cables.
Implications of aerodynamic force on bridges were forgotten in the decade before bridge was built.
Vertical motion was seen on other bridges around the time the Narrows was built. This motion was termed to be acceptable as structures were built to take large vertical loads.
Wind forces (vertices) can actually lift a roadway, and this will and did transmit torsional motion to the bridge. Roebling addressed this issue 90 years earlier.
Large ground counterweights with tiebacks were added before the collapse to reduce torsional motion. These were damaged in a earlier smaller wind storm.
Golden Gate torsional motion was seen in the early 50s from 130 mph winds. Added strength to roadway truss has stopped this torsional motion.
The original bridge width-to-span ratio was 1:72. Golden Gate ratio is 1:47 and is still considered "skinny".
Outside consultants recommended design changes before the bridge was built but the bids had already been accepted on existing design specifications.

Attachment shows roadway truss cross sections of the 1940 and 1950 design. Note the 1950 design is not twice as large but more the six times as large in cross sectional area.

Ryan B

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