The other Golden Gate bridges

In May 2013 I gave a 5-minute Ignite talk about the alternative designs and proposed (but never executed) updates to the Golden Gate Bridge:

Since the slides in the video are a bit blurry, I wanted to share some of the original images, and elaborate on where I found them (mostly, at San Francisco History Center on the 6th floor of the Public Library).

I also included bonus things at the bottom that are not in the talk!

The original proposal comes from a Strauss and O’Shaugnessy’s 1921 booklet Bridging “The Golden Gate”:

The second one was published in an article Definite steps taken toward construction of Golden Gate Bridge by Joseph Strauss, in 1930—nine years later:

This Allan Rush 1924 mock-up was in a book The Gate: The true story of the design and construction of the Golden Gate Bridge:

The next set of photos are my own contribution, done in Photoshop. I tried to find a set of distinctive, non-repetitive photos, and then “repaint” the bridge on each on of them. Additionally, for the Air Force and Navy variants, I wanted photos with planes and boats, respectively. (For one of the most photographed landmarks in the world, it was actually somewhat hard to find good, high-resolution shots!)

Most of the following was photographed from San Francisco Chronicle, Oct. 5, 1930:

And this monstrosity is a capture from a movie Bicentennial man. Kind of a low resolution, since only DVD edition was available:

The following four scans come from an amazing collection of historical scans by Eric Fischer. Eric was also kind enough to lend me some historical artifacts!

This slide with an update log is combined from many different sources, most notably The Golden Gate Bridge: Report of the Chief Engineer, Volume II from 2007:

And the last, evocative drawing, comes from a brochure The Golden Gate Bridge: History & Principal Characteristics, published in 1933 or 1934—I don’t remember which edition exactly:

More proposals

I needed to cut a few slides because of Ignite time constraints — the slide with various proposed tower designs had to go, and this cute stunt… with three towers!

I learned about a few things online after the talk:

The tunnel

Lastly, I more recently found out about this hand-written proposal, from 1921, for building a… tunnel under the Golden Gate. From the California Historical Society page:

When we think Golden Gate, the brilliant image of our internationally beloved bridge sweeps into view, emerging from and dominating the natural landscape. It’s hard to imagine the city detached from its man-made, fog-swept icon. Technical questions aside, Bugbee’s plan might suggest an alternate vision of urban planning for the Bay Area, one that is more modest, less triumphalist, and, perhaps, for better or for worse, more twenty-first century.

I took those photos during one of the CHS events, and transcribed the text for your reading pleasure.

A Tube Across the Golden Gate
M.G. Bugbee
June July August 1921
639 28th Avenue
S.F. California

Connecting San Francisco and Marin Counties by Tube.

The connection of San Francisco and Marin County by a double tube across the Golden Gate is the most logical solution of the present traffic needs of both counties.

The objections to the tube as it is now built are:

  • Its great cost.
  • Length of time in completion.
  • Danger to life and health of the workmen employed in
    its construction.

The writer proposes a new method of construction that will make the building of a tube across the Gate not only possible but feasible.

This method consists of building a reinforced concrete tube on land and moving it into position as built, using a continuous construction and movement.

By the application of the principles of suspension, to carry the tube in its proposed position to the other side.

We need figure no working load until proper foundations and piers are subsequently established.

This is made possible by the buoyancy of a hollow tube and the great tensile strength of steel cables used in reinforcing.

To carry out our method we erect a platform and set rollers on the exact proposed curve of the tube. We set our concrete mixer and begin construction at a point 200 feet from the water line.

When the first section of forms is completed and reinforced, pouring of concrete and movement of the construction begins and is continuous
until tube has reached the other side.

This movement, about two feet per hour, allows time for the removal
of forms for reuse and for the complete water proofing of the tube
before it is submerged.

We construct the tube so proportioned that its specific weight is exactly equal to the specific weight (per foot) of the two 2 inch steel cables used to guide tube into place.

The detail of the steel reinforcing necessitated by the water pressure need not be considered at this point.

This work has been proved possible in actual example.

In this article we will consider only new methods.

Details of water-proofing, lighting and ventilation may also be left for future consideration.

The size of the tube is regulated for the largest auto truck.

The increasing use of the auto in all its manifestations permits a tube for automobiles only to fill all traffic needs.

At ten miles per hour speed 1000 machines every hour would be passed each way.

A working load of about 100 lbs per linear foot.

It is evident that in placing tube in position we cannot use piers or supports of any kind after it leaves the rollers.

We must rely entirely on suspension.

It will be noticed in the section of the tube we show in the bottom four 2" cables.

By means of two of these cables, laid before work on tube is started, we propose to guide and steady tube until it is in place.

Power is applied thro [sic] these cables to move tube as built until it reaches the last roller on the starting side.

At this point the two cables are fastened to the exact depth curve required for tube and this power thereafter kept constant.

At this point the power rollers marked in sketch take the duty of supplying the additional power as needed (or retarding if necessary) and regulate the speed of movement.

When the tube has reached the other side we complete piers and filling and build wharves of concrete at each end. These wharves will be of practical use. We also solidly block the ends of all cable reinforcing in concrete.

The sketch we show (Page 2) is of course hypothetical. Until the exact course is decided we can only suggest probabilities.

The necessary power to move the tube can be electrical and can be approximately estimated.

The tube on land will weigh about 10 tons per lin foot and entering and emerging from water average half that weight.

The 200 feet in land gives u 2000 tons to move down an incline. We estimate 50 lbs per ton to move it.

Then 700 feet partly submerged we estimate moving as on level, as the grades balance on 2000 tons as 150 lbs per ton.

This gives us an extreme pull at the last of 700,000 lbs.

Owing to the slow movement of the tube (2 feet per hour) this power is easily obtained by gear.

As the start is gradual and movement continues there is no inertia to overcome.

The friction of the tube passing thro [sic] the water is comparatively nothing.

The tide of the Golden Gate is strong but at the great depth of the bulk of our span there is no wave motion and little if any tide.

It is only when the tube approaches the other side that the tide need be considered. There horizontal rollers on the cables as far from shore as possible takes care of the strain.

We have estimated the cost of tube as $200.00 a linear foot, or about one million dollars ($1,000,000.00).

While the actual laying of tube takes a little over a hundred days, we estimate that tube can be entirely completed, ready for use, in less than six months.

When the wharves and piers have been completed and our tube is ready for use, it has ceased to figure as suspended construction. It must be figured and considered as a beam of reinforced concrete.

Using our hypothetical sketch as a base we have four spans of 1000 feet each.

The tension we show consists of four 2" gal. steel cables with safe capacity of 250,000 lbs each.

These have an effective depth (ED) of 12½ feet.

Two 1¼ cables at 125000 each ED — 10 feet or a total at 12½ ED of 1,200,000 lbs.

In calculating the safe load on a reinforced concrete beam we use the formula

that is live + dead load per food by square of span, divided by 20, is equal to the tension multiplied by the depth in feet of efficiency of the tension

As it would be in practice rare that as much as 100 lbs per foot would be carried and practically impossible to exceed 150 lbs our span is certainly safe.

Using 250 lb per foot for our load our formula gives a quick method of figuring

or required tension would be the square of span in feet and conversely the square root of given tension gives the safe span in feet.

We have not included the extra tension provided by the reinforced steel. This would add to our margin of safety.

Figured as above our resistance to side (tidal) pressure is over 350 lb per linear foot.

Owing to the depth of the Golden Gate we will probably be compelled to use piers about 100 feet in depth.

The problem is a peculiar one as they are to be set so far below the surface that the use of divers will be difficult and also that their completion can only be made after the tube is in place. The writer suggests the following method as made easier by our conditions.

The actual weight carried by each pier even with extreme load is small. It ranges from 100,000 to 150,000 lbs.

The shaft of the pier to be a cylinder or tube about 8 feet in diameter. These to be built on the runway before the main tube is started, to be placed in position and partly filled with concrete. The cap to be moulded in separate piece, and placed over pier so as not to interfere with the course of the tube.

When the tube is in place this cap can be lifted to bottom of tube and the pier filled up with concrete.

This may be done with our divers.

There is no possible danger to life and health of the workmen in our method.

There is no possibility of any sudden collapse of the completed tube.

Should the tube be tested to the breaking point as an experiment the first sign of failure would show by small cracks in the cornet and consequent leakage.

This would be long before the danger point.

Our completed tube does not differ materially from some present examples.

It is stronger and safer from its continuous tension cables, and safer from leakage on account of its continuous construction.

It is the method of building an not the result that we claim as new.

We claim that by our method we ensure absolute safety and efficiency as well as economy of time and cost, that it solves the problem of crossing the
Golden Gate.

M.G. Bugbee

639 28th Avenue