RESEARCH ARTICLE


Seismic Retrofit of Pile Group Foundation with Thickened Caps



Edward Wang*
Hsin-Hsin Rd., Hsin-Fong,Hsin-Chu, TAIWAN/Minghsin University of Science and Technology, Taiwan.


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Creative Commons License
© 2015 Edward Wang;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Hsin-Hsin Rd., Hsin-Fong, Hsin-Chu, TAIWAN/Minghsin University of Science and Technology, Taiwan; Tel: 886-3-559-3142; Fax: 886-3-557-3718; E-mail: edwang313@gmail.com


Abstract

The case studied in the paper proves that thickening the pile cap is an effective seismic retrofit alternative to strengthen a pile group foundation. Unlike the typical seismic retrofitting of foundation, the proposed method eliminates the need to drive long piles into existing bridge substructures, substantially reducing cost, construction time and traffic interruption. The method thickens the pile cap of the bridge foundation to engage with a larger quantity of soil when under the influence of seismic excitations. The additional friction provided by the surface of the concrete encasement helps to resist the overturning moment of the earthquake forces, while the passive pressure provided by the soil helps to resist lateral forces during earthquakes. The method is recommended for implementation in the freeway bridge retrofit project in Taiwan due to construction constraints. A successful retrofit requires existing piles in at least moderate condition, detailed construction sequences and installation of the encasement.

Keywords: Bridge engineering, encasement method, pile group foundation, seismic retrofit, structural design.