Steel Plates in Collapsed Bridge Inadequate from Design Error, NTSB Says

A design error that caused inadequate steel plates to be used may have caused the collapse of the I-35W bridge into the Mississippi River last year in Minneapolis, NTSB investigators announced Jan. 15. About 1,000 feet of the deck truss fell into the river, leaving 13 people dead and 145 others injured.

"Although the board's investigation is still ongoing and no determination of probable cause has been reached, interim findings in the investigation have revealed a safety issue that warrants attention," said National Transportation Safety Board Chairman Mark Rosenker. "During the wreckage recovery, investigators discovered that gusset plates at eight different joint locations in the main center span were fractured. The board, with assistance from the [Federal Highway Administration], conducted a thorough review of the design of the bridge, with an emphasis on the design of the gusset plates. This review discovered that the original design process of the I-35W bridge led to a serious error in sizing some of the gusset plates in the main truss."

Undersized gusset plates were found at eight of the 112 nodes (joints) on the main trusses of the bridge. These 16 plates, two at each node, were about half the thickness required -- too thin to provide the margin of safety expected in a properly designed bridge, according to NSTB, which announced the findings at a news conference.

The board issued a safety recommendation to FHWA that said "for all non-load-path- redundant steel truss bridges within the National Bridge Inventory, require that bridge owners conduct load capacity calculations to verify that the stress levels on all structural elements, including gusset plates, remain within applicable design requirements, whenever planned modifications or operational changes may significantly increase stresses."

NTSB officials said there is no evidence to suggest the deficiencies in the various design review procedures associated with this bridge are widespread or go beyond this particular bridge, which they said is the sole bridge failure of this type of which the safety board is aware. "The safety board has issued this recommendation, at this time, to ensure that the original design calculations for other bridges of this type have been made correctly, before any planned modification or operational changes are accomplished affecting such bridges and before any additional stresses are placed on them," Rosenker said.

Download Center

  • Safety Metrics Guide

    Is your company leveraging its safety data and analytics to maintain a safe workplace? With so much data available, where do you start? This downloadable guide will give you insight on helpful key performance indicators (KPIs) you should track for your safety program.

  • Job Hazard Analysis Guide

    This guide includes details on how to conduct a thorough Job Hazard Analysis, and it's based directly on an OSHA publication for conducting JHAs. Learn how to identify potential hazards associated with each task of a job and set controls to mitigate hazard risks.

  • A Guide to Practicing “New Safety”

    Learn from safety professionals from around the world as they share their perspectives on various “new views” of safety, including Safety Differently, Safety-II, No Safety, Human and Organizational Performance (HOP), Resilience Engineering, and more in this helpful guide.

  • Lone Worker Safety Guide

    As organizations digitalize and remote operations become more commonplace, the number of lone workers is on the rise. These employees are at increased risk for unaddressed workplace accidents or emergencies. This guide was created to help employers better understand common lone worker risks and solutions for lone worker risk mitigation and incident prevention.

  • EHS Software Buyer's Guide

    Learn the keys to staying organized, staying sharp, and staying one step ahead on all things safety. This buyer’s guide is designed for you to use in your search for the safety management solution that best suits your company’s needs.

  • Vector Solutions

Featured Whitepaper

OH&S Digital Edition

  • OHS Magazine Digital Edition - May 2022

    May 2022

    Featuring:

    • WEARABLE TECHNOLOGY
      How Wearable Technology is Transforming Safety and the Industrial Workplace
    • TRAINING: CONFINED SPACES
      Five Tips to Improve Safety in Confined Spaces
    • INDUSTRIAL HYGIENE
      Monitor for Asbestos to Help Save Lives
    • PPE: FALL PROTECTION
      Fall Protection Can Be Surprising
    View This Issue