Structural Behavior and Load Distribution Factor of a T-Girder Bridge with Various Truss Diaphragms

A diaphragm is an essential component of a T-girder bridge. Evaluating the influence of various truss diaphragms (TDs) on the structural behavior and load distribution factor of T-girder bridges assists in bridge design and strengthening. In this study, a series of experiments and simulations were conducted to investigate the strengthening effect of two types of TDs (i.e., triangle-TDs and K-TDs) based on a small-scale T-girder bridge model. Formulas for the flexural rigidity of the two types of TDs were proposed and verified by using rigid-joint girder methods, experiments, and simulations. Then, taking the K-TD as an example, the calculation method for the stiffness of the truss was analyzed and derived based on rigid-joint girder and graphic multiplication methods. The results showed that K-TDs had a better strengthening effect than triangle-TDs. The deflection and strain of the K-TD-strengthened T-girder bridge were reduced by 21% and 16%, respectively, compared with those of the triangle-TD-strengthened bridge. The formulas for flexural rigidity were proposed and used to calculate the load distribution factor. The maximum error of the calculated load distribution factor was 16% compared with the simulation and experimental results. Moreover, the calculation method for the stiffness of the K-TDs was analyzed and obtained.Practical ApplicationsDeterioration of multigirder bridges is getting worse due to the increasing traffic load and insufficient maintenance. Adding diaphragms to the existing bridges can improve the load distribution of multigirder bridges and reduce the maximum load of the girders. This work evaluated the influence of two types of truss diaphragms (triangle truss diaphragm and K truss diaphragm) on the load distribution of a T-girder bridge, and the results showed that the two types of truss diaphragms can reduce the maximum deflection and strain in the T-girder bridge effectively. The flexural rigidity formulas for the two types of truss diaphragm were proposed and proved to be accurate by comparing with experiments and finite-element methods. Moreover, the truss stiffness of the K truss diaphragm was derived by a graphic multiplication method. These formulas can be used by bridge engineers for new bridge designing or existing bridge strengthening in practical engineering.