Deficient Bridges

Overview

Yamhill County has 133 bridges under its maintenance jurisdiction. Of these, 46 bridges have been appraised as being deficient by the Oregon Department of Transportation and in need of repair or replacement.

What is a Deficient Bridge?

The Oregon Department of Transportation inventories bridges in Yamhill County and assigns one of the following categories:
 

  • NON-DEFICIENT - Inspections show that the bridge can safely carry the load and traffic it was designed to handle.
  • STRUCTURALLY DEFICIENT - The bridge is closed because of structural inadequacy, restricted to light vehicles (load-posted) because it can no longer carry the weight it was designed to handle, or is in immediate need of rehabilitation to stay open.
  • FUNCTIONALLY OBSOLETE - The bridge is structurally sound but it is no longer adequate for the road it is on and for the traffic it serves. This category includes bridges that are load-posted because the original design no longer meets the criteria for the highway system for deck geometry, clearance, or roadway alignment.

The American Association of State Highway and Transportation Officials (AASHTO) Sufficiency Rating Formula defines the method for describing bridge condition. The sufficiency designation is important because a bridge must be declared deficient and should have a sufficiency rating of 80 or less to qualify for federal funding. This rating is one criteria used to establish priorities for bridge replacement or rehabilitation and as a guide to generally identify bridges that need improvements. The lower the rating, the higher the priority. Bridges rated from 100-80 are considered non-deficient; 80-50 generally require rehabilitation; below 50 need replaced or rehabilitated. Structurally deficient bridges are rated for deck, superstructure, substructure, culvert, retaining wall, structural condition and waterway adequacy. Functionally obsolete bridges are rated for deck geometry, underclearance, approach roadway alignment, structural condition and waterway adequacy. If a bridge is both structurally deficient and functionally obsolete, it is classified only as structurally deficient.

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