Influence of secondary components on the serviceability of steel girder highway bridges.

摘要

In bridge design practice, little attention has been paid to bridge secondary components and their effect on overall system behavior. However, bridge secondary components affect bridge serviceability and in some cases can lead to component or complete system failures. Steel girder bridges have suffered from the unaccounted behavior of the secondary components, exhibiting, among other problems, the locking of pin-hangers, out-of-plane fatigue cracks of diaphragm-to-girder connections, and altered bridge superstructure and substructure behavior due to unintended fixity of pin-hangers and unintended movement restraint. In this work, an analytical investigation was carried out to assess the stress demands of pin-hangers in their service and fatigue limit state, develop predictive models for assessing out-of-plane fatigue stresses of diaphragm-to-girder connections, and evaluate effects and behavior of bridge bearing supports. The overall bridge system behavior was also investigated considering the effect of the individual secondary component.; An existing steel girder bridge for which measurements for pin-hanger details were available was modeled. Global and local models for the bridge and pin-hanger components were studied to assess the stress demands of the pin-hanger details under service and fatigue loads. Predictive models for determining the magnitude of the maximum out-of-plane stress on the web gap of diaphragm-to-girder connections were developed and validated through three-dimensional finite element models. The effect of bearing pads on bridge system behavior was studied through three-dimensional finite element models for a set of simple span bridges. Different shear modulus values of the bearing pads were considered and the performance of the bridge system was evaluated under different loading conditions.; The findings from the analytical investigation for the selected bridge secondary components revealed that the axial load demands on hangers are not equally shared by both hangers on each side of a girder web in skew bridges. Frozen pin-hanger details could lead to stress states exceeding the strength of the material that may cause the hanger to fracture. Fatigue category E was found to be adequate for pin-hanger details as per the AASHTO specifications. The maximum out-of-plane stresses for staggered and non-staggered diaphragm-to-girder connections can be predicted with reasonable accuracy by using two proposed simple expressions that consider the geometry of the detail, the material properties, and the differential displacement between adjacent girders. (Abstract shortened by UMI.)