Chapter 5: Ratings and Load PostingAnchor: #CACDBHBI
Section 1: Condition RatingsAnchor: #i1005218
Definition of Condition Ratings
Condition ratings based on field inspections are snapshots in time and cannot be used to predict future conditions or behavior of the structure. However, condition ratings based on inspections along with written comments by a field inspector act as the major source of information on the status of a bridge. Condition ratings also help planning for necessary repairs or modifications. In addition, the condition ratings are used as flags when performing over-weight permit evaluations.
Condition ratings are one-digit numbers given by the field inspector to the various components of a bridge. They are objective and not opinions.
Condition ratings reflect deterioration or damage and do measure design deficiency. For instance, an old bridge designed to a low load capacity but with little or no deterioration may have excellent condition ratings while a newer bridge designed to modern loads but with deterioration will have lower condition ratings.
Channel, waterway, riprap, and other channel protection components under and directly upstream and downstream of the bridge are often related in assignment of a condition rating for the channel.Anchor: #i1005254
Recording Condition Ratings
Condition ratings are entered on the Bridge Inspection Record. Six component items are covered on the form, and each lists four to 11 elements. The Item Numbers relate to the entry of the data in the electronic Bridge Inventory Files, the detailed instructions for which are contained in the Coding Instructions of the Coding Guide:
- Deck (Item 58)
- Superstructure (Item 59)
- Substructure (Item 60)
- Channel (Item 61)
- Culverts (Item 62)
- Approaches (Item 65)
- Miscellaneous (used for information, but not entered in the Bridge Inventory File. Still important as part of the Bridge Folder).
The rating must equal or exceed the minimum values for each element of a component (shown to the left of the element description on the form). Each element is rated based on independent consideration. For instance, poor or deficient secondary members (bracing, diaphragms, etc.) in a superstructure may cause the Superstructure (Item 59) component to have a poor rating even though the main members show no significant deterioration. The summary Component Rating must be the least of the element ratings comprising that component.
However, Deck (Item 58) component is independent of its associated element ratings such as joints, railings, wearing surface, etc.
Do not base condition ratings on the known presence of chlorides in the deck, superstructure, or substructure concrete or low compressive strengths from core samples. Determine the condition rating solely on the observed, materials-related, physical condition of the component at the time of the inspection.
The Bridge Inspection Form has space for fully supportive written comments for each of the above features. These comments are required for any condition rating of 7 or less. The form includes a brief summary of the description of each level of rating. More detail on the condition rating for each item number is given in the instructions of the Coding Guide.Anchor: #i1005321
Assigning Condition Ratings
Evaluate each element separately based on general considerations for assignment of the ten levels of condition ratings. However, other deficiencies may affect the condition if they are directly related. For instance, instability of an approach embankment may reduce the abutment condition rating but not reduce the Superstructure condition rating.
Consider only permanently installed repairs when assigning condition ratings. Permanent implies that the repair has returned the damaged or deteriorated element to a condition as good as or better than the remainder of the bridge. For instance, a steel beam damaged by an over-height load that reduced the load capacity of the beam is considered permanently repaired when a section is replaced or a bent section is straightened by proper techniques and no residual cracks can be found. The strength of the repaired member is the primary concern. Modifications and repairs that simply improve the appearance of a damaged member are not considered to improve the condition rating.
Do not consider as temporary any repair which remains in place without further project activity for a significant period of time. Consider the repair permanent and evaluate the structure accordingly. Four years from the repair date is a reasonable amount of time for a District to move a project forward. If the District requires more time, then submit a written justification for continuing to classify a repair as temporary.
Do not consider for condition rating any components with temporary repairs, even though functioning. For instance, a support or brace to a partially undermined column could be susceptible to damage from another flood; therefore, make the condition rating on the basis that the support is not present. Do not consider temporary repairs in determining condition ratings because they directly affect the calculations of the sufficiency ratings described in Chapter 7.
Condition ratings are still a matter of judgment, which should be made based on experience, knowledge, and consistency with other structures with the same deterioration.