| The National Cooperative Highway Research Program (NCHRP) has shown concerns regarding the design, fabrication, and erection of horizontally curved steel girder bridges due to unpredicted girder displacements, fit-up, and locked-in stresses. Nationally, up to one-quarter of steel girder bridges are being designed with horizontal curvature, an alarming figure when considering the unknown behaviors of this type of bridge. The primary objective of this work was to monitor and evaluate the behavior of four in-service, horizontally curved, steel-girder bridges with integral and semi-integral abutments. Additionally, the influence and behavior of fixed and expansion piers were considered. A number of steps were performed in order to meet the project objectives. First, a national state department survey was conducted and a literature review was performed in order to understand the state-of-art regarding these types of structures. Second, a monitoring program was developed and installed on six bridges located at the I-35, I-235, and I-80 interchange northeast of Des Moines. Third, a monthly survey was conducted on each bridge with the purpose of tracking the bridge movements, and lastly, the data gathered during the monitoring period of the project was post-processed. The following general conclusions were made from the results of the study: There was no measureable difference between the horizontally curved bridges and straight bridges used in this work with regard to bridge behavior; internal strains were recorded in the composite girders as a result of thermally induced restrained expansion and contraction, and of the recorded strains, axial strain showed the largest ranges; the bridges expanded and contracted with seasons and showed more expansion and contraction near expansion piers than fixed piers. The equivalent cantilever method of steel pile analysis fell short of accurately predicting the relationship between weak axis bending strain in the piles and the pile head displacement; the measured internal stress in the abutment piles due to expansion and contraction of the bridge were generally below 50% of yield stress; and the soil pressures on the abutment backwalls were generally below approximate passive soil pressures. |
