Short Note on Numerical rating system (NRS)

Numerical rating system (NRS)

a) The “Numerical Rating System” for bridge inspection assigns a “Unique Rating Number” (URN) to represent the physical condition of a bridge. Lower the URN more serious is the deteriorated condition of a bridge. The system thus helps in identifying progressive deterioration in the condition of a bridge. URN can be stored in a computer for quick retrieval and fixing priorities for repairs or rehabilitation. 

b) The URN of a bridge is arrived at based on the condition of components and a “condition rating number” (CRN) assigned to each of them. The various components of a bridge in sequence, are : i. Foundations and flooring, if any, ii. Masonry / concrete in substructure, iii. Training and protective works, if any, iv. Bed blocks, v. Bearings and expansion arrangements, vi. Superstructure – Girders / Arch / Pipe / Slab etc. vii. Track structure.

c) The CRN is allotted to each of the above components based on their condition at the time of inspection, using the following scale

d) when any component in a bridge is more than one in number CRN is assigned to each of them and the lowest value used. For example, if a bridge has five piers and two abutments, and these are given the CRN of 5,4,3,2,5,5,4 then the CRN for the substructure component of the bridge would be minimum of the above i,e. 2.

e) If in any bridge one or more components do not exist, the CRN for such components shall be shown as 6

f) From the CRNs for different components of a bridge, an overall Rating Number (ORN) for the bridge as a whole is then given. The ORN is th lowest of the seven CRNs of a bridge, except 0.

g) For a major bridge, the URN would comprise of eight digits, the first digit indication the ORN and the following seven digits the CRNs of each of its above seven components in sequence.

h) URN of minor bridge shall be represented by its ORN only, i,e. by a single digit to indicate its overall condition.

j) The physical condition of a road over bridge is to be represented as for rail bridge.

k) The CRN of different components of a bridge as evaluated above shall be entered in the “Box” to be provided in the register at appropriate places.