Seismic vulnerability through drift assessment for bridges with geometrical irregularities

Abstract

In this work, the analyses of common types of highway bridges under seismic loading are presented for several geometrical irregularity conditions on either the substructure or superstructure. In the first series of analyses, the influence of the substructure is studied by varying the central pier height, and the height of the pier next to the support, to compare the corresponding responses at deck displacement level. In the second series of analyses, the superstructure irregularity is examined trough variations on the extreme span length, as compared to the length of the central span, and for curved bridges; both conditions are studied for several degrees of irregularity. All the bridges are subjected to 53 accelerograms recorded on the highest seismic hazard zone in Mexico. From these analyses, an index defined by the normalized difference on the maximum displacements between the regular and the irregular systems is calculated. In addition, fragility curves with the normalized differences for each irregularity condition are developed. The information provided by the index is complemented with these curves and the index behavior and its dispersion are drawn in a global way. The proposed index does not follow a linear trend to describe the bridge seismic vulnerability, as considered in the current Mexican practice. The obtained results are used to propose fragility categories, and their associated relative ponderation weights, to assess the substructure and superstructure bridge irregularity and to identify potential aspects were the bridge inspector may focus on in order to make more detailed work to pursue maintenance decisions.

Keywords:

• Irregularity of bridges
• seismic behavior
• inspection procedures
• curved bridges
• cumulative probability distributions
• quartiles distributions

Acknowledgements

This work was partially supported by the Universidad Autónoma Metropolitana and by CONACYT (National Council of Science and Technology of México), through its postgraduate program.

Disclosure statement

No potential conflict of interest was reported by the authors.