Guidelines for Analyzing Curved and Skewed Bridge and Designing Them for Construction

摘要

Although the use of curved and skewed bridges continues to increase steadily throughout the United States, certain aspects of their behavior during construction and while in service still are not well understood. The effects of design, fabrication, and construction on the geometry and load distribution in a curved or skewed bridge system are areas in which further study and understanding are required. The project utilized remote acquisition capabilities for instruments on two structures in the interstate 99 corridor: a horizontally curved, steel I-girder bridge, and a skewed, pre-stressed, concrete bridge. Data obtained from these structures were examined and the numerical model accuracy for curved and skewed, steel, I-girder bridges and select appropriate model types and software was investigated. Parametric studies were undertaken on a group of representative curved and skewed steel bridge structures to numerically examine the influence of specific variables on behavior during construction. Results enabled the identification of preferred erection sequencing approaches. Among other results, girder vertical deflections were decreased when paired-girder erection methods were used and paired inner erection was preferred for structures with severe curvature. Erection methods examined herein did not show appreciable influence on skewed bridge behavior. Drop-in erection would be an acceptable approach for either curved or skewed bridges. The findings and the numerical modeling from the parametric studies formed the basis for suggesting possible modifications to relevant PennDOT publications. Web out-of-plumbness did not cause appreciable bridge deflection and stress increases when the out-of-plumbness was within the limit (1%) specified in the Structural Welding Code. Exceeding the 1% limit of the web out-of-plumbness can result in slightly higher deformations and stresses. The use of temporary construction shoring can significantly reduce girder deflections, leading to a more constructible condition. Inconsistent cross-frame detailing increased vertical and radial deflections in curved bridges and lateral deflections in skewed bridges. Replacing solid plate diaphragms in skewed bridges slightly increased deformations but did not severely affect cross-frame stresses. The applied temperature change did not have an appreciable impact on overall bridge deflections and stresses for all of the radii, skew angles and cross-frame spacings studied.