Rating:
7 votes

I-35W Mississippi River Bridge

Photos 

Work on the north end of the bridge

It appeared that at the time of this photo, workers were finishing up demolishing the abutments of the 1967 bridge. Unfortunately because the area was closed off, there was no way to get an even closer shot.

Photo taken by Jason Smith in December 2007

Enlarge

BH Photo #112997

Map 

Street View 

I-35W Bridge Collapse: Some Explanations and Thoughts 

Written by Nathan Holth. Copyright 2011. All Rights Reserved.

The media, and even occasionally highway agencies, have done a poor job of reporting exactly why the I-35W Bridge collapsed. This has led to additional misunderstanding about whether other truss bridges, whether or not similar to the I-35W Bridge, pose a collapse risk. Some explanations and thoughts about the I-35W Bridge collapse follow.

The I-35W Bridge collapsed because the gusset plates that formed the connections for the truss bridge members were not thick enough and as a result lacked the proper strength to bear the load the bridge was designed to bear. This problem was not detected when the bridge was first designed because the engineers failed to perform the calculations needed to check whether the gusset plates were the correct size.

The overall design of the I-35W Bridge was safe, reliable, and effective. Had the gusset plates been the correct thickness, the I-35W Bridge collapse would not have occurred. The gusset plates were the only problem with the bridge.

Sverdrup and Parcel, the designers of the I-35W Bridge, were experienced engineers who knew how to properly design a bridge and check the design calculations. While they failed to check the design calculations of the I-35W Bridge, they built many other truss bridges without making this mistake, and those bridges have proven to be safe and reliable bridges.

There is nothing about a "deck cantilever truss" type of bridge that is less safe or less reliable than other types of cantilever truss bridges.

Most truss bridges are considered "fracture critical" meaning that if one part of the bridge fails the entire bridge might collapse. While that sounds scary, the reality is that fracture critical bridges are safe and reliable as long as they are inspected routinely as required by law. A proper bridge inspection will detect problems with truss members long before they even come close to complete failure.

Bridge inspectors and highway agencies are now required to check truss bridges for the type of design errors that were present on the I-35W Bridge. As a result, truss bridges standing today and still open to traffic have been checked to make sure a similar problem does not exist.

The fact that a truss bridge is fracture critical should not be used to justify demolishing and replacing a truss bridge. If a truss bridge is to be replaced, additional reasoning should be present (deterioration, width of roadway, etc) to justify a replacement.

The fact that a bridge "looks like" the I-35W Bridge should not justify a demolition and replacement project. Unless the similar-looking bridge was found to have gusset plates that are too thin, such a bridge would not be at risk for an I-35W type of failure and subsequent collapse.

Additional Resources:

Official NTSB I-35W Bridge Report: http://www.historicbridges.org/info/bridgehunterfiles/i35wre...

NTSB Presentation Discussing The Cause of the Collapse: http://www.historicbridges.org/info/bridgehunterfiles/i35pre...

Facts 

Overview
Collapsed deck truss bridge over the Mississippi River on I-35W in Minneapolis
Location
Minneapolis, Hennepin County, Minnesota
Status
Collapsed
History
Built 1967; collapsed Aug. 1, 2007; new bridge built in 2008
Builders
- Industrial Construction Co. of Minneapolis, Minnesota
- Sverdrup & Parcel of St. Louis, Missouri (Designer)
Design
Warren deck truss
New bridge consists of a concrete deck cantilever design with hourglass-like piers
Dimensions
Length of largest span: 456.1 ft.
Total length: 1,907.2 ft.
Deck width: 104.0 ft.
Approximate latitude, longitude
+44.97910, -93.24473   (decimal degrees)
44°58'45" N, 93°14'41" W   (degrees°minutes'seconds")
Approximate UTM coordinates
15/480704/4980658 (zone/easting/northing)
Quadrangle map:
Saint Paul West
Inventory numbers
MN 9340 (Minnesota bridge number)
BH 20424 (Bridgehunter.com ID)

Update Log 

  • August 2, 2018: Photo imported by Roger Deschner
  • January 20, 2015: New photo from Roger Deschner
  • July 3, 2014: New Street View added by Ralph Demars
  • March 4, 2013: Updated by John Marvig: corrected to more common name
  • December 7, 2011: Essay added by Nathan Holth
  • September 16, 2009: Updated by Jason Smith: Bridge has been replaced- see changes above
  • August 1, 2009: New photo from J.R. Manning
  • March 18, 2008: New photos from Jason Smith

Related Bridges 

Sources 

  • Wikipedia
  • Jason Smith - flensburg [dot] bridgehunter [dot] av [at] googlemail [dot] com
  • J.R. Manning - thekitchenguy [at] sbcglobal [dot] net
  • Nathan Holth
  • John Marvig - marvigj27 [at] gmail [dot] com
  • Roger Deschner - rogerdeschner [at] gmail [dot] com

Comments 

Mississippi River I-35W Bridge
Posted September 18, 2008, by Ian Anderson (iang2 [at] comcast [dot] net)

The new bridge, the Saint Anthony Falls Bridge, opened today. It's an arch-shaped concrete segmental box girder, and although it is rather boring compared to the adjacent concrete arch, it is a nice bridge judging by the pictures.

Mississippi River I-35W Bridge
Posted March 18, 2008, by J.R. Manning (thekitchenguy [at] sbcglobal [dot] net)

Jason, your photos really bring home the severity of the collapse. The high tension distribution towers, in the background, appear to be bowing in honor of those who lost their lives in the crash.

Mississippi River I-35W Bridge
Posted February 5, 2008, by Jolene (joakabridgefreak [at] yahoo [dot] com)

I have been across that bridge many times due to seeing my DR at the U.The day it collapsed I happened to have a very late appointment and just got across before I saw the sign fall!! I happen to live near a bridge like it that is now under investigation!!! Not near as big,being a 400ft span But someday that one will go too!! Already cracks in the gussette plates have been found.Being a bridgefreak I don't get scared too much,even when the thing is bouncing(flex)!! It don't seem to move anymore however.MN DOT does not seem overly concerned with the kettle river bridge here in sandstone,but alot of people refuse to drive over it!!My mom now floors it to get across quickly!! Too much paranoia here I think!I walk this bridge daily as it is a pretty route!( kettle river bridge is posted under pine county and I have posted it's pics for those interested!!)

Mississippi River I-35W Bridge
Posted August 5, 2007, by Carolyn Susor (carolyn_susor [at] jhancock [dot] com)

I live in Minneapolis & was always nervous about crossing this bridge. I avoided taking it if I could. I always thought it looked rickety. Also, when you were crossing it going south-bound, there was a big curve just as you were getting on the bridge. There were several entrance & exit ramps at that curve & you constantly had to watch for cross-traffic. I was afraid I'd drive off the thing. I'm so sorry that it collapsed taking people with it, but maybe now a better bridge will replace it.

Mississippi River I-35W Bridge
Posted August 5, 2007, by Carolyn Susor (carolyn_susor [at] jhancock [dot] com)

I live in Minneapolis & was always nervous about crossing this bridge. I avoided taking it if I could. I always thought it looked rickety. Also, when you were crossing it going south-bound, there was a big curve just as you were getting on the bridge. There were several entrance & exit ramps at that curve & you constantly had to watch for cross-traffic. I was afraid I'd drive off the thing. I'm so sorry that it collapsed taking people with it, but maybe now a better bridge will replace it.

Mississippi River I-35W Bridge
Posted August 4, 2007, by Leon Cote (leoncote [at] verizon [dot] net)

What bridges in Massachusetts are of the same contruction as Mississippi River I-35W Bridge?

Thanks,

Leon Cote