Title

Experimental and analytical evaluation of continuous concrete box girder bridges

Date of Completion

January 1999

Keywords

Engineering, Civil

Degree

Ph.D.

Abstract

Concrete box girder bridges have been widely used during the past four decades. However, the behavior of these bridges subject to cracking has been limited studied and documented. In this research, the behavior of two curved reinforced concrete box girder bridges was investigated. ^ One bridge has two continuous spans jointed to a simple span with a cantilever. The bridge superstructure is a cast-in-place three-cell concrete box girder with conventional reinforcement. Field inspections have noted that there is significant cracking in the webs at different locations. A field test and a linear-elastic finite element analysis were then performed to examine the response of the bridge under static loading. In the finite element analysis, a three-dimensional model was generated with shell and beam elements based on design. The model was initially used to gain insight into the causes of the cracking with the field test information employed to make changes to the stiffness of the model in specific areas. To fully understand the causes of the cracking, the influence of temperature was included in the study. ^ The other bridge has been monitored with various sensors including tiltmeters, thermocouples, accelerometers and strain gages. It is prestressed and curved with three continuous spans. The interior supports are provided by single pier columns at the middle of the bridge width. In the field inspection, substantial torsional cracks were found in the superstructure in the proximity of the interior columns. Significant torsional cracks were also found in the columns. In this study, a finite element model was developed to determine how the measured temperature variations influence the bridge behavior and determine how the bridge deforms to explain why the bridge has cracking. The analytical model was calibrated with the vibration and tilt data. ^