Memorandum

City of Lawrence

Public Works

 

TO:

Chuck Soules, Dena Mezger

FROM:

Matt Bond

Date:

August 31, 2007

RE:

City Bridges

 

 

This memo provides a requested overview of bridge terminology as well as identifying the bridge structures that the City of Lawrence is responsible for maintaining and inspecting within the city limits. 

 

DEFINITION OF A BRIDGE

The American Association of State Highway and Transportation Officials (AASHTO) defines a bridge as any structure measuring greater than twenty feet in total span length.  By definition this includes reinforced concrete box (RCB) structures.  The City is responsible for 15 bridges and all but four of these are classified as RCB’s.  None of the structures the City is responsible for are similar to the recently collapsed I-35 bridge in Minnesota.  Any bridge located on a State or U.S. designated highway or interstate falls under the jurisdiction of KDOT for inspection and maintenance.  Examples in Douglas County would include the Kansas River bridges located on US-40/59, the Wakarusa River Bridges on K-10, and the US-40 (6th Street) bridge over K-10.  The Kansas Turnpike Authority (KTA) is responsible for the I-70 Bridges spanning the Kansas River.

 

KANSAS RIVER BRIDGES

According to the latest KDOT State Bridge Inventory listing the Kansas River bridges last had a routine inspection on April 17, 2006 and an underwater inspection was completed on August 24, 2005.  A Sufficiency Rating of 76.7 was listed for both bridges.  See the following web link for detailed description explaining sufficiency rating. http://www.ksdot.org/PDF_Files/SufficiencyRatingsExplained.pdf

 

STRUCTURALLY DEFICIENT vs. FUNCTIONALLY OBSOLETE

For an explanation detailing the difference between structurally deficient and functionally obsolete refer to the following web link.

http://www.ksdot.org/KsBridges/KsBridgesDefObs.asp

 

SUMMARY

None of the bridge sized structures that the City of Lawrence is responsible for maintenance and inspection is subject to sudden catastrophic failure.  Reinforced concrete box structures are designed to give early warning signs of fatigue and high stress by exhibiting significant cracking.  All of the structures located on State and U.S. designated highway routes are inspected on at least a biannual basis by KDOT. In February I will be attending a two week bridge inspection and evaluation training course.