Construction and detailing methods of horizontally curved steel I-girder bridges.

摘要

The present research extends the state-of-the-art in understanding the important physical phenomena that impact the constructability and behavior of horizontally curved steel I-girder bridges. The steel erection procedure of a horizontally curved and skewed steel I-girder bridge is examined through the use of a nonlinear finite element model. The behavior of the structure is studied for each stage of steel erection by observations of girder stresses, displacements and reactions.;The eccentric application of gravity load resulting from horizontal curvature results in torsional forces being applied to the girder sections of a horizontally curved bridge. Due to the relative torsional flexibility of the steel I-girders, these forces can result in a marked girder rotation quantified in this work as web out-of-plumbness. The present research quantifies the effect and importance of girder web out-of-plumbness on primary member stress response in steel I-girders, both individually and as part of an assembly. Girder flange stresses and vertical and lateral displacements are presented for single straight and curved beam models and a curved two-girder system model all subject to up to 5 degrees of out-of-plumbness. Through a parametric study the effects of changes to radius or horizontal curvature, girder spacing, cross frame spacing, and web depth on the behavior of the curved two-girder system having initially out-of-plumb webs are investigated.;The effects of "inconsistent detailing"---an approach to designing bridge cross frames to mitigate girder web out-of-plumbness---are presented. Specifically, the structural behavior in terms of resulting "locked-in" girder flange stresses and displacements are discussed. The research work reported herein is primarily analytical in nature, employing detailed non linear finite element models to investigate the steel erection and web-plumbness issues associated with horizontally curved steel I-girder bridges.;Based on the analytical studies conducted, it is proposed that the effects of web out-of-plumbness need to be specifically considered for the effects on flange stresses in design, as an alternative to the practice of inconsistent detailing. Consideration of these effects during design and conventionally detailing girders and cross frames for the web-plumb position at no-load, in lieu of specifying inconsistent detailing to control web out-of-plumbness, will reduce construction problems that typically result from the practice of inconsistent detailing.;However, if inconsistent detailing is employed to mitigate web out-of-plumbness, it must be recognized by bridge designers that this approach has complex effects on "locked-in" stresses and constructability of curved I-girder bridges. These "locked-in" stresses and constructability issues need to be considered by bridge designers and steel erectors, respectively.