Simplified Assessment Procedure to Determine the Seismic Vulnerability of Reinforced Concrete Bridges in Indiana

2019-08-15T12:38:55Z (GMT) by Farida Ikpemesi Mahmud

The possibility of earthquakes in Indiana due to the presence of the New Madrid Seismic Zone is well known. However, the identification of the Wabash Valley Seismic Zone has increased our understanding of the seismic hazard in the state of Indiana. Due to this awareness of the increased potential for earthquakes, specifically in the Vincennes District, the seismicvulnerability of Indiana’s bridge network must be assessed. As such, the objective of this thesis is to develop a simplified assessment procedure that can be used to conduct a state-wide seismic vulnerability assessment of reinforced concrete bridges in Indiana.

Across the state, variability in substructure type, seismic hazard level, and soil site class influences the vulnerability of bridges. To fully understand the impact of this variation, a detailed assessment is completed on a representative sample. Twenty-five reinforced concrete bridges are selected across the state, and analyzed using information from the bridge drawings and a finite element analysis procedure. These bridges are analyzed using synthetic ground motions representative of the hazard level in Indiana. The results of the detailed analysis are used to develop a simplified assessment procedure that uses information that is available in BIAS or can be added to BIAS. At this time, BIAS does not contain all the necessary information required for accurate estimates of dynamic properties, thus, certain assumptions are made. Several candidate models are developed by incrementally increasing the level of information proposed to be added into BIAS, which resulted in an increase in the level of accuracy of the results. The simplified assessment is then validated through a comparison with the detailed analysis.

Through the development of the simplified assessment procedure, the minimum data item which must be added to BIAS to complete the assessment is the substructure type, and bridges with reinforced concrete columns in the substructure require a detailed assessment. Lastly, by increasing the level of information available in BIAS, the agreement between the results of the simplified assessment and the detailed assessment is improved.