Fatigue analysis of stringer to floor beam connections in through plate girder and through truss railroad bridges

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 44-46).Issued also on microfiche from Lange Micrographics.The objective of this thesis is to determine fatigue stresses in the stringer to floor beam connections of through plate girder (TPG) and through truss (TT) bridges in order to predict failure. Field observations by the Association of American Railroads (AAR) indicate failure in the stringer to floor beam connections of both the TPG and TT bridges, although a higher frequency of failure appears in the TT bridges. Accordingly, this study includes 1) creating analytical models for the TPG and TT bridges, 2) determining member internal forces, 3) developing force envelopes, 4) determining maximum internal stresses, and 5) comparing these results to field observations. First, bridge models for the TPG and TT bridge were assembled using a finite element analysis program in order to evaluate member internal forces. The TPG bridge model was taken from the plans of an existing bridge designed in 1912 and located near TX Highway 21 between College Station and Caldwell, TX. The TT bridge model was taken from the plans of an existing bridge designed in 1902 in the Chicago Office of the American Bridge Company. Next, a finite element analysis was conducted to obtain member internal forces. The resulting forces were compiled to create axial load, shear force, and moment envelopes. These envelopes were constructed to provide the magnitudes and location of the maximum forces required for analysis. These forces were also used to develop maximum tensile stresses for the rivets in the floor beams. After examining the results, the following conclusions were drawn. Axial load was predicted to be a source of higher failure frequency within TT bridges versus TPG bridges. Lower chord deformation in the TT bridge caused elongation of the floor system that, in turn, produced axial loads in the bridge members. The TPG bridge members, however, carried no axial load. Shear force was not predicted to be a contributing factor for increased connection failure rates in the TT bridges as compared to the TPG bridges, but bending moment was. This result, however, was sensitive to the degree of fixity in the stringer to floor beam connection