Title

Development of a baseline for structural health monitoring and seismic evaluation on a post-tensioned curved concrete box-girder bridge

Date of Completion

January 2007

Keywords

Engineering, Civil

Degree

Ph.D.

Abstract

A joint effort between the Connecticut Department of Transportation and the University of Connecticut has been underway for more than 20 years to use different monitoring approaches in the assessment of the state's bridge infrastructure. This thesis is based on study of a three span curved post-tensioned concrete box-girder bridge with expansion bearings. It is part of a monitoring network and has been successfully monitored over a 6 year time period. Establishment of a baseline is essential for continuous monitoring of such a complicated bridge. Operationally, the baseline of structural health monitoring relates to the establishing of field testing database and finite element (FE) model which forms the basis for assessing the structural integrity. The establishment of the baseline field database to eliminate the effect of varying temperature conditions on the field testing data was first studied. This database used data collected from a full year cycle and was based on the undamaged status. Next, a new Mindlin plate element with an embedded through crack was developed for modeling cracking conditions on the bridge in FE analysis. The element behavior was investigated using numerical examples. Finally, the baseline FE model of the bridge was developed after updating to reflect the current condition. This involved the calibration of the material properties, utilization of spring bearing elements, and replacement of Mindlin plate elements (MP4) on box-girder with cracked Mindlin plate elements (MP4C) to represent the bridge operating conditions. A good agreement in modal results has been observed between the baseline FE model and the baseline field database. Following this, the baseline FE model was used with an earthquake simulation based on introducing a selected ground motion to the bridge. It is shown that the field database and FE model established in this study can be reliably used as a baseline of the bridge monitoring system. The results demonstrate that a baseline study is necessary in order to assess the structural integrity for the bridge over time.^