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The Inspection Source Blog

Attending the Bridge and Tunnel Inspectors Conference in Portland, OR, April 18-20, 2023?

Be sure not to miss Todd Niemann, Principal Engineer and Manager Twin Cities Area, and Ryan Sievers, Field Operations and Rope Access Program Manager presentations.  Meanwhile, get a sneak peek of their abstracts below.

T-1 Steel Address the Risks and Meet Federal Mandates
Todd Niemann, PE

The fractured tie girder discovered on the I-40 Hernando Desoto Bridge in 2021 brought a new term and issue for bridge owners to address. After evaluation of the Hernando Desoto fracture, FHWA issued a new inspection mandate for certain bridges. T-1 Steel is now a new term that many Bridge Engineers and Inspectors are just becoming aware of. This presentation is intended to explain what T-1 steel is and what the issues are in plain and simple terms. The presentation will discuss the FWHA mandate and summarize its requirements. Last but not least, the presentation will provide bridge owners with anticipated costs of this work from past projects for their planning and budgeting purposes.

Timber Bridge Inspections – Unlocking the Hidden Secrets of Timber Members
Using Partially Destructive Testing Methods
Ryan Sievers, PE

Timber bridges are used throughout our infrastructure system. While they seem straightforward to inspect, they tend to hide their defects deep within their members. Standard inspection practices of visually checking the exterior, hammer sounding the timber member for audible sounds of decay, and pick testing only uncovers the truth about the exterior shell of the timber member.  These traditional inspection methods may leave the condition of the untreated element core subject to interpretation and debate.

Fickett has been working extensively with the Montana Department of Transportation (MDT) to perform pattern drilling on timber, focusing on timber piles and caps. The pattern drilling uses a resistograph to obtain internal member information regarding timber core rot. The resistograph is a partially destructive inspection method that uses a small diameter drill bit to drill into the member and measures the resistance of the annual growth rings through the member.   A graphed readout is produced by the resistograph, and with minimal training, experience, and some critical interpretation of the readout, the extent and location of rot and voids can be documented based on where the resistance decreases or disappears.  This method of inspection is able to obtain data all the way into the center of the timber member where traditional inspection methods are unable to reach.  Once the data is obtained, MDT is able to prioritize repairs of timber piles and replacement of timber caps. Pile repair methodologies will be discussed detailing products and practices that have been successful. Lessons learned for both pattern drilling and repair methods will discussed.