Wednesday, November 3, 2021

Ralph Modjeski and some of his bridges

These notes are some of the factoids in PBS's Point of View show: "Bridging Urban America: The Story of Ralph Modjeski." I recorded it on Aug 9, 2017.

If I understand the video correctly, his first bridge was the Rock Island Railroad Bridge across the Mississippi River known as the Government Bridge because it serves the Rock Island Arsenal.

 07:45  There is a photo of a steel mill. I recognized that the mill was probably the Joliet Iron Works. Fortunately, those notes begin with the photo from which the TV image was cropped. I'm glad I already have the photo because it is neat.

Earlier in the show, it talks about Abraham Lincoln helping the railroads fight the steamship industry for the right to build a bridge across the Mississippi River. And it showed a plaque that indicates the first bridge was built in 1856. The commander of the Rock Island Arsenal fights Washington for a stronger bridge across the Mississippi. During construction, the swing span was destroyed by an ice flow after the temperature rose to 40 degrees just a few weeks before water commerce on the river was expected to begin. At 9:50 is an video of the temporary lift bridge that Modjeski built from an existing span. I've never seen this bridge before. He finished with a day to spare, and it operated well during its 3-month lifetime. The completed bridge used a 56 horsepower motor. Recall that electricity was bleeding edge technology at this time. The record breaking swing span was designed in just three months and erected in fifteen months. It is the world's only swing span with unlimited rotation.

12:14  1900 CHCAGO, ILLINOIS
He opened his office in the prestigious 17-story Monadnock Building. It was "the tallest commercial iron-frame building ever constructed." He was one of the consulting engineers that reviewed the city's design for bascule bridges. (The Courtland Bridge is an example of the first generation design.) These bridges have become known as the Chicago Style Bridge. At this time Joseph Strauss was his senior draftsman. He was married to a cousin that was also from Poland. Actually, he was married to his job, and his wife took their three children on many trips to Europe. Eventually, his family stayed there.

16:31  1902-1905 THEBES, ILLINOIS
Pin-construction was revolutionary and speeded up construction.


This segment described the bridge designed by Theodore Cooper that collapsed. Cooper was interested in designing the longest cantilever bridge in the world. He made the span longer without redoing his calculations and he insisted that nobody check his design. He did not want to be subservient to anybody. Of the errors that were made, the main one is that he underestimated the weight of the bridge,

23:57  1908-1917 Reconstruction of  QUEBEC BRIDGE   QUEBEC, CANADA
Modjeski helped design the replacement bridge that used twice as much steel and much of it was nickel steel. The center span fell as it was being lifted when it was just 2' from its final location, and it is still at the bottom of the river. This bridge completed Canada's transcontinental railroad. To this day, it is still the longest cantilever bridge.

It would be the largest bascule bridge of its time. The patent holders Rall and Strauss fought for the design win. Rall won.

He opened an office in NYC and was the consulting engineer for the Manhattan Bridge. Frank Masters was in charge of the NYC office.
The chief engineer of the bridge, Moisseiff, introduced a new design analysis technique: deflection theory. I noticed that Moisseiff worked with Modjeski on later bridge designs.

I have skipped the intro that explained that his mother was an opera singer and that at one time he played the piano four hours each day because he was considering a career as a professional piano player.

41:16   1920's in AMERICA
Modjeski made the transition from railroad to vehicular bridges and constructed 19 bridges in this decade.

42:26   1921-1926 BENJAMIN FRANKLIN BRIDGE Formerly the Delaware River Bridge 
The most difficult part was the foundation for the cable anchorage piers. The rock was 65' to 110' below the surface of the ground. Silicon steel was used in this bridge. And one third of the steel was nickel steel. It was the longest suspension bridge in the world, and it significantly pushed the size of the cables. Information from a diagram at 46:08:
Delaware River1866630"

50:17   1923-1930 FDR MID-HUDSON BRIDGE In Partnership with Moran
(Moran was the foundation engineer.) This was the first suspension span that had a full length cable rehabilitation. But I did not catch the year of the rehabilitation.

55:43   1927-1929  AMBASSADOR BRIDGE
Replacing the traditional cold-drawn acid steel wire with an innovative heat-treated cable wire proved to be a problem. After some broken wires were found before this bridge was opened, Modjeski and MIT did some research and determined that 11,000 miles of wires would have to be replaced. The crossing still opened nine months ahead of schedule. Today, the bridge handles 25% of the traffic between US and Canada.

59:41   1926-1935 THE HUEY P. LONG BRIDGE   In Partnership with Masters and Chase
They used the technique of building sand-filled artificial islands through which the caissons were sunk almost 200' into the existing soil. This technique had been used once previously, but not in such an intense river flow.


1:09:11   1931-1936 SAN FRANCISCO - OAKLAND BAY BRIDGE Formerly Transbay Bridge
At 1:11:17 is a map of the various proposals offered by high-profile engineers seeking the commission of the bridge. The 8-mile bridge would be the biggest in the world. The center anchor pier for the tandem suspension bridge for the west bay crossing will hold the remaining bridge if one of them somehow "disappears." The island tunnel that connects the east and west spans has a 75' diameter bore. It remains the largest bored tunnel ever built. Its $77m cost made it the most expensive public works of its time. It was built under budget, ahead of schedule and without major catastrophes. It also had the longest single span. The 1989 earthquake damaged the east side where the piers rested on 100' timber piles. The piers for the suspension bridges and the cantilever span are concrete down to the bedrock and they survived the earthquake. But the suspension bridges have had "seismic retrofitting" and the east bridge has been replaced since we now know much more about building structures to resist earthquake forces. The replacement bridge is a "self-anchored suspension span" and cost $6.4b.

He built over 40 bridges.

The show ends with the text: "Since the beginning of time, the infrastructure of a nation was considered the most important factor in the progress of a civilization." It is a shame that we don't value the maintenance of that infrastructure.  A DVD is available from

More bridges that were designed by Modjeski and Masters:

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