Impact of the Implementation of Unbonded Seismic Isolators on the Design and Retrofitting of Bridges

Abstract

The existence of road infrastructure such as bridges that do not meet current design criteria, the deterioration of these due to use, environmental factors and extraordinary or unforeseen conditions, and the increase in seismic and gravitational design loads due to regulatory updates, generate the need for search of new design and retrofitting alternatives for this type of structure. Thus, the conditions of these structures need to be assessed and corresponding interventions need to be identified. It is important to implement alternatives that are both economically and functionally efficient. For example, base isolation can reduce direct construction costs by using devices designed and built in the country of origin, but the unfamiliarity and importation costs of these devices are the main obstacles to mass use. In this article, a comparative analysis is performed of a conventional design and an integrated design for base isolation using low-cost unbonded fiber-reinforced elastomeric isolators (U-FREIs) made in Colombia. A methodology is proposed for the analysis of new and existing isolated structures, in which the isolators are placed between the substructure and superstructure. This methodology is used to design and strengthen a typical prestressed concrete girder bridge, and the results are compared against those obtained using a conventional scheme. Finally, an existing bridge is analyzed using on-site measurements to determine the dynamic properties and modify the numerical model used for analysis, design, and retrofitting. The effectiveness of the proposed methodology as a tool for the design of new bridges and the retrofitting of existing structures was verified for all cases. Economic and structural benefits were evidenced by reductions in direct costs of up to 15% and the seismic force of up to 20%, respectively.

Keywords:

• prestressed concrete girder bridge
• unbonded isolators
• seismic design and retrofitting
• cost comparison
• benefits of seismic isolation

Acknowledgements

The second author would like to acknowledge a scholarship for Colombian Doctoral Formation No. 617/2013 provided by Colciencias. The third author would like to acknowledge a scholarship for Colombian Doctoral Formation No. 647/2015 provided by Colciencias.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Pontificia Universidad Javeriana Cali (Programa Institucional para el Pontificia Universidad Javeriana – Cali (Programa Institucional para el Desarrollo y Fortalecimiento de la Investigación 2019)); Ministerio de Ciencia, Tecnología e Innovación - Minciencias [grant number FP-80740-463-2020, code 1106-852-70483].