Spring analogy to predict the 3-D live load response of slab-on-girder bridges

In current bridge design methodology, beam line analysis and girder distribution factors are often used to compute the maximum live load demands on the girders. However, this method may not effectively predict the response of all girders under live load. Furthermore, it has been found to be conservative compared to 3-D analysis results and load tests of bridges. With the spring analogy, it is possible to closely approximate the 3-D live load response of bridges with accuracy comparable to that from a detailed finite element analysis. For a given truck position, the bending moment resisted by each girder and individual girder deflections can be computed easily. The live load demand imposed on the secondary members, such as diaphragms or cross-frames, can also be predicted using the results of the spring analogy. This analysis method can be used for any transverse truck location on the bridge, and should be useful for both the design and rating of bridges.