Benton Street Bridge

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Benton Street Bridge in Iowa City : The first fully welded steel bridge in Iowa and one of the first in the United States

The Benton Street Bridge crossed the Iowa River in Iowa City . It was constructed in 1949 as the first fully welded steel bridge in Iowa and one of the first in the United States. It was designed by Ned Ashton as a continuous, five-span, two-lane steel girder bridge with a concrete deck . The bridge was demolished in 1989 and replaced by a wider bridge in 1990.

Design and construction

General plan and elevations of the new bridge (above) and the old bridge (below)

Designed in 1947 and constructed in 1949, the Benton Street Bridge pioneered the welding of steel bridges in the state of Iowa and was recognized nationwide as one of the most notable examples of new construction. The overall dimensions were as follows:

  • Total length: 180 m (592.0 ft)
  • Deck width: 10 m (33.0 ft)

Prefabrication and erection

Manual arc welding and automated submerged arc welding were used to prefabricate the parts . The parts were transported directly to the construction site by train, for which a short piece of track had to be laid for the construction period.

Construction site welding and concreting

Welder at work on the north and south beams. The old bridge in the background, around May 10, 1949 The precast concrete was pumped onto the wooden deck with a concrete pump
Welder at work on the north and south beams. The old bridge in the background, around May 10, 1949
The precast concrete was pumped onto the wooden deck with a concrete pump

The Teleweld Corporation of Chicago used four Lincoln power sources from April 19 to May 16, 1949, a total of 528 welding man-hours for on-site MMA welding (that is, manual arc welding with flux-coated electrodes).

The bridge's designer, Edward (Ned) L. Ashton, a pioneer of welding in bridge construction, had previously designed several important Mississippi bridges, and presumably the partially welded and partially bolted Cottonville Bridge. He later directed the construction of the world's first welded aluminum road bridge, which was completed in Des Moines, Iowa in 1958. Ashton has been called "the greatest bridge engineer in Iowa history".  P. 1

The concrete for the deck was pumped onto temporary wooden formwork made from recycled planks from the old bridge.

sidewalk

Cantilever arm and S-brackets and the southern handrail, field No. 1, near the southeastern abutment Pillar no. 2 with fixed supports for the south beam (fields no. 3 and 2), cantilever brackets and handrail
Cantilever arm and S-brackets and the southern handrail, field No. 1, near the southeastern abutment
Pillar no. 2 with fixed supports for the south beam (fields no. 3 and 2), cantilever brackets and handrail

The roadway was placed on the main girders with supports, while the sidewalk was cantilevered on elaborately shaped S-brackets that were attached to the outside of the girders.

Historical panels

Dedication plaque on the northwestern bridgehead Dedication plaque on the northeast bridgehead
Dedication plaque on the northwestern bridgehead
Dedication plaque on the northeast bridgehead

At the north-east and north-west abutments of the bridgehead , two historical panels were embedded in the concrete structure that supports the street lamps. The first of the two bronze tablets contains the following information:

The Iowa River was first crossed near this point in 1839-40 by the Ralston Greek Ferry. It was then bridged upriver in 1853 to better serve Old Capitol and Iowa Avenue. Later the railway bridge at Ryerson's Mill was added a little further upstream. This location was bridged in 1902/03 with light steel truss bridges and wooden driveways in order to better serve the mill. The first bridge was known as the Ryerson Bridge until the old mill burned down . It was later named "Benton Street Bridge" after its location. The current bridge replaced the original one in 1949 and cost $ 276,000 (which is roughly $ 2,953,000 today).

The second board reads, “This bridge was built in 1948 and 1949 by the City of Iowa City under the direction of

  • Preston J. Koser, Mayor
  • George J. Dohrer, clerk
  • William H. Bartley, City Attorney
  • Edward W. Lucas, City Attorney

Councilors

  • Frank Fryauf, Jr., District General
  • Clark F. Mighell, General District
  • James M. Callahn, First District
  • James W. Jones, Second Borough
  • Charles T. Smith, Third Ward
  • Max S. Hawkins, Fourth Ward
  • William H. Grandrath, Fifth Ward

Designed by Ned L. Ashton, Consulting Engineer.
Supervised by Fred Gartzke, Urban Engineer.
Erected by Jensen Construction Co., Des Moines

The cost of this bridge was covered by a general Iowa bond issue of $ 276,000.00. "

Decay and fatigue

Crumbled concrete at the top of Pillar # 1 on the movable bearing below the main south girder A T-stiffener welded to the inside of the main beam shows the welded attachment with a pendulum support, field 1, south beam
Crumbled concrete at the top of Pillar # 1 on the movable bearing below the main south girder
A T-stiffener welded to the inside of the main beam shows the welded attachment with a pendulum support, field 1, south beam

In 1985 a structural study was carried out to examine the possibility of widening the two-lane bridge to four lanes. The consultants found that the bridge had certain design features that through material fatigue can lead to catastrophic failure, was known about the in its construction in 1948, little.

Intermediate strips welded to the flange of the plate carrier caught their attention. This particular detail no longer exists in welded plate girder bridges since it was found that it causes fatigue problems in the girders in rather low stress areas. At Benton Street Bridge, this technique could have caused fatigue failure with serious consequences.

A closer examination confirmed the likelihood that the bridge was a structure susceptible to fatigue cracking with no realistic potential for renovation and maintenance. The bridge was therefore demolished in 1989 due to the risk of fatigue cracking and replaced by a wider bridge in 1990.

Web links

Commons : Benton Street Bridge  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ a b c d Jeffrey A. Hess and Robert Hybben: Benton Street Bridge, carrying Benton Street across the Iowa River, Iowa City, Johnson County, Iowa. HAER No. IA-30 / HAER IOWA, 52-IOWCI, 4-xx, October 1989.
  2. ↑ a b Stephan Kallee: Benton Street Bridge, Iowa. The first fully welded steel bridge in Iowa and one of the first in the United States. Retrieved June 27, 2020 ( CC BY-SA 3.0 ).
  3. ^ Ned L. Ashton: Studies in Structural Arc Welding: A Modern Steel Deck Girder Highway Bridge. Published by The Lincoln Electric Company, Cleveland, Ohio. Bulletin 838 7S0O 2 52, pp. 1-32. Copy in HAER No IA-30, pp. 38-70.
  4. ↑ Ned L. Ashton: Welded Deck Girder Highway Bridge. The Welding Journal, September 1949.
  5. ^ Library of Congress: Benton Street Bridge, Spanning Iowa River at Benton Street, Iowa City, Johnson County, IA. Photos of the HAER IA-30 investigation.
  6. ↑ a b J.R. Manning and Luke Harden: Benton Street Bridge (Old), on www.bridgehunter.com. Retrieved June 27, 2020.
  7. ↑ Stephan Kallee: Cotton Ville Bridge. One of the first welded arch steel bridges in Iowa. Retrieved June 27, 2020.
  8. ↑ Stephan Kallee: 86th Street flyover in Urbandale, Iowa. The world's first welded aluminum bridge. Retrieved June 27, 2020.
  9. ↑ Video of the Iowa Department of Transportation: Hank Zalatel interviewed Robert "Sam" L. Carstens to the photos and diaries of Benton Street Bridge.
  10. ↑ This figure was based on the template: Inflation Determined, rounded to the nearest thousand and relates to January 2020.

Coordinates: 41 ° 39 ′ 3.1 ″  N , 91 ° 32 ′ 17 ″  W.