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Yaquina-Bay-Bridge Sufficiency Rating

Sufficiency Rating Definition

 

A Sufficiency Rating is an obsolete way of comparing the safety and condition of a bridge to other bridges in the state.  It is not meant to be used as a single indicator of bridge condition and safety. Even though the rating is no longer used for its original purpose of determining federal funding eligibility, it is still kept in the bridge report.  Consequently, its purpose is often misunderstood and its significance is misinterpreted.
 
As created in the 1970’s, the Sufficiency Rating considers:
·        What condition and how safe the structure is (Structural Adequacy and Safety)
·        How durable the bridge is and how well its serves the users (Serviceability and Functional Obsolescence)
·        How essential it is (Essentiality)
Each consideration is given a percentage of points that add up to 100.  One factor---design load---is a major part of the top two considerations
 
Why does the Yaquina Bay Bridge rate so low?
 
--Condition--
The overall condition of the bridge changes according to how much maintenance it receives 
 
The rating it received in 2011 did not account for a $3 million steel repair project that was completed in 2012.
 
The bridge will continue to receive the maintenance it needs to preserve its useful condition.
 
--Durability and Safety--
Due to its age and original design, the bridge will always be considered “Structurally Deficient,” but that does not mean the bridge is unsafe.
 
Because the bridge was designed and built in the 1930’s, its “design load” does not compare well with modern bridges.  
 
A bridge is designed to safely withstand the loads and forces it will encounter in its life.  That includes weight of bridge users as well as forces like wind and earthquake.
 
The standards that applied in 1934 are not today’s standards.  That holds true for construction, such as deck thickness and reinforcement bar spacing, as well as overall dimensions.  
 
The bridge’s narrow width, narrow travel lanes, and narrow shoulders were not designed for modern vehicles.  While the bridge adequately handles the traffic volumes of today, it is not as efficient and safe as a wider bridge.
 
--Its essential nature--
Because there is no convenient detour available should the operation of the bridge be interrupted, it can’t fulfill its essential need, therefore it scores low in that category.
 
 --Analogy--
None of the above description means the bridge is unsafe or won’t have a long life.  It’s not unlike a house.  An old house may have small rooms and a lack of modern conveniences but given proper maintenance, can offer generations of use.  It may never compare favorably to a new house but can provide all the service a family needs.