Load-bearing index to grade structural capacities of road bridges

For decades, bridge structural conditions have been evaluated on the basis of structural health grades determined during a bridge examination. However, recalculations conducted for bridge structures show that structural deficiencies, such as low or insufficient load-bearing capacities, are not or not sufficiently reflected by these conditions if no corresponding damage or unusual behavior can be detected. There are known cases of deficient bridges that had to be replaced even though the structural health grade suggested a good condition or vice versa. To better measure and assess the structural conditions of a bridge, i.e., the criteria of the superstructure that are relevant for the load-bearing capacity, a new parameter was developed. The load-bearing index allows for a different perspective as it identifies presumed deficiencies on the basis of various criteria that are independent of the physical condition. In a next step, these deficiencies have to be further examined. Both parameters - the structural health grade and the load-bearing index - describe the condition and the usability of a structure. But they do so from a different point of view, and, therefore, complete the overall picture of the structure.