Geography Class, Day 2

Thanks to all of the children for a wonderful class today. They all came with some additional facts on the Oakland Bay Bridge as I asked them. They could have emailed them to me too. They can email me with questions or comments at anytime.

We didn’t get to do the fun project with craft sticks, but you’ll do it first thing when we meet again.

This week there’s not much homework. Just some reading of the two pages I gave you, and this post.

1. Read this information below about bridges and their components (it’s the same as the two pages I gave you for your binders last class). Let’s see if you all can remember and learn further about these concepts (they are the ones we’ll be illustrating with sticks and yarn):

STAYED CABLE BRIDGE
Suspension bridges appear to have the advantage over cable-stayed bridges for long spans. As the span length increases, the height of the tower increases in a cable-stayed bridge without multiple towers. Cable-stayed bridges allow the construction of the individual segments of the bridge at remote locations. The suspension bridge requires the building of suspension cables across the entire span before the deck installation begins.
The cable-stayed bridge has the advantage of not requiring massive anchorages at the ends of the cables. Suspension bridges require anchorages strong enough for the tension, or angular pulling, on the suspension cables. Solid rock or a large mass of stable concrete is the preferred geological base for an anchorage. These massive anchorages carry the entire weight of the bridge, and their weight must exceed the combined weight of the bridge and the vehicular load.
SUSPENSION CABLE BRIDGE

 

CANTILVER BRIDGE
Image result for cantilever bridge
This image, old as it is, illustrates the cantilever principle nicely.


2. Read this, please:

Miss Mary Remlinger asked about the wood at the foundation of the Oakland Bay Bridge. It was initially, as told in the graphic below, treated Douglas Fir Wood, but as you can see, it was a weakness in the bridge, and it was replaced in 2014 as part of that still ongoing full replacement project of the whole East Section of the bridge, the one going from Yerba Buena to Oakland.

TIP: CLICK ON IMAGES TO READ AND SEE THEM BETTER

 

Look at the old cantilever section of the bridge:

 

The suspended cantilever span was cut in the middle in the photo above.

The bridge was deconstructed in the reverse order of its construction.

Look at the new East section of the bridge with the old bridge in the background. Doesn’t it look nice and modern?

 

Look at the world’s biggest cantilever bridge, the Quebec’s Bridge. Can you recognize those cantilever sections with their trusses? Isn’t the suspended middle section amazing?, hanging by the work of the opposing forces from the protruding cantilever slabs.

 

Another cantilever bridge, Forth Bridge, in Edinburgh, Scotland. The color is striking, isn’t it?

 

This below is the biggest suspension bridge in the world, Akashi Kaikyō Bridge:

The Oakland Bay Bridge West section,

and the Golden Gate itself. (Aren’t you glad it’s not black and yellow?, or would you have rather seen it painted those two colors, like a wasp?)

 

In the photo above, you can see Fort Point.

 

Plans for the Golden Gate Bridge in the 1930s called for the fort’s removal, but Chief Engineer Joseph Strauss redesigned the bridge to save the fort. “While the old fort has no military value now,” Strauss said, “it remains nevertheless a fine example of the mason’s art…. It should be preserved and restored as a national monument.” The fort is situated directly below the southern approach to the bridge, underneath an arch that supports the roadway.

You can read more about the fort, and see photos here. There it’s mentioned how the Golden Gate and this fort have been the setting of many movies. The Golden Gate is the most photographed bridge in the world, and probably the most beautiful too.

This section of the bridge, once thought to have been able to withstand any magnitude of foreseeable earthquake, was actually vulnerable to complete structural failure (i.e., collapse) triggered by the failure of supports on the 320-foot (98 m) arch over Fort Point. A $392 million program was initiated to improve the structure’s ability to withstand such an event with only minimal (repairable) damage. One challenging undertaking is completing this program without disrupting traffic.

Remember the map I gave you the first day? This,

Image result for map of san francisco bridges
I’m adding this one too,

 

Can you see Alcatraz in this map? Yes. Alcatraz island and the former prison in it, are near the Golden Gate. I didn’t even have time to tell you about that.
I also forgot to tell you about the traffic at the Golden Gate bridge with its 6 lines. Initially, they placed plastic removable cones to separate the lines into 3 and 3 lines, 4 and 2, or 2 and 4.
Those caused frontal crush accidents, and now they have a zipper truck and a moveable median barrier like this video shows,
And, didn’t you want to see the light show at the Oakland Bay Bridge?
Not bad, for just $15 dollars a night!
This is some footage of the opening of the Golden Gate. Don’t be too critical about the quality, remember this was 1937.

I leave you with the poem and song dedicated to the Golden Gate (the forties, guys):

Written by Joseph P. Strauss, Chief Engineer, Golden Gate Bridge and Highway District

The Mighty Task is Done
Written upon completion of the building of the Bridge in May 1937

At last the mighty task is done;
Resplendent in the western sun
The Bridge looms mountain high;
Its titan piers grip ocean floor,
Its great steel arms link shore with shore,
Its towers pierce the sky.

On its broad decks in rightful pride,
The world in swift parade shall ride,
Throughout all time to be;
Beneath, fleet ships from every port,
Vast landlocked bay, historic fort,
And dwarfing all–the sea.

To north, the Redwood Empire’s gates;
‘To south, a happy playground waits,
in Rapturous appeal;
Here nature, free since time began,
Yields to the restless moods of man,
Accepts his bonds of steel.

Launched midst a thousand hopes and fears,
Damned by a thousand hostile sneers,
Yet ne’er its course was stayed,
But ask of those who met the foe
Who stood alone when faith was low,
Ask them the price they paid.

Ask of the steel, each strut and wire,
Ask of the searching, purging fire,
That marked their natal hour;
Ask of the mind, the hand, the heart,
Ask of each single, stalwart part,
What gave it force and power.

An Honored cause and nobly fought
And that which they so bravely wrought,
Now glorifies their deed,
No selfish urge shall stain its life,
Nor envy, greed, intrigue, nor strife,
Nor false, ignoble creed.

High overhead its lights shall gleam,
Far, far below life’s restless stream,
Unceasingly shall flow;
For this was spun its lithe fine form,
To fear not war, nor time, nor storm,
For Fate had meant it so.

(If you want to take a peak to next lesson’s place, click here).
See you in October!
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