Sharif Digital Repository

Steel box girders have two webs and two flanges on top that are usually connected with shear connectors to the concrete deck and are also known as tub girders. The end diaphragms of such bridges comprise of a stiffened steel plate welded to the inside of the girder at each end. The diaphragms play a major role in transferring vertical and lateral loads to the bearings and substructure. A review of literature shows that the cyclic behavior of diaphragms under earthquake loading has not been studied previously. This paper uses a nonlinear finite element model to study the behavior of the end diaphragms under gravity and seismic loads. Different bearing device and stiffener configurations have... 

Most slab-on-girder steel bridges have been designed and constructed without seismic resistance consideration; as a result, their members, connections, and more commonly their substructure are not sized and detailed to provide the required ductile response needed during major earthquakes. A ductile seismic retrofit solution proposed in this investigation consist of converting of existing end diaphragms into ductile end diaphragms and replacing the end cross-frames and the lower lateral-braced panels adjacent to the supports by special ductile diaphragms. Consequently, this creates ductile fuses to protect the rest of the super- and substructure. This paper illustrates the typical seismic... 

The paper presents the experimental and analytical model analysis of a steel-girder arch bridge. The field test is carried out by ambient vibration testing under traffic excitations. Both the peak picking method in the frequency domain and the stochastic subspace identification method in the time domain are used for the output-only model identification. A good agreement in identified frequencies has been found between the two methods. It is further demonstrated that the stochastic subspace method provides better mode shapes. The three-dimensional finite element models are constructed and an analytical model analysis is then performed to generate natural frequencies and mode shapes in the...