TY - GEN
T1 - Geotechnical seismic isolation using EPS geofoam around piles
AU - Karatzia, Xenia A.
AU - Mylonakis, George E.
PY - 2017
Y1 - 2017
N2 - The feasibility of a new geotechnical seismic isolation system for pile-supported structures, such as bridge piers on monopiles, is investigated. The isolation system utilizes a soft annular zone of viscoelastic material, such as EPS geofoam, around the upper part of the pile. The presence of the EPS elongates the fundamental natural period of the structure and also modifies its damping. For simplicity and as a proof of concept, the superstructure is considered a simple oscillator. Based on a dynamic Winkler model for pile-soil interaction, the problem is treated analytically leading to a simple design-oriented analysis method. Closed-form solutions are obtained for: (a) the lateral stiffness of the structure-foundation system, (b) the corresponding fundamental period, and (c) the overall damping. Numerical analyses in the frequency domain by means of the computer code SPIAB verify the above analytical predictions. Analyses in the time domain are also carried out to examine the effect of geofoam on the dynamic response. Results in terms of base shear, maximum pile bending moment, and displacement at deck level are presented in dimensionless form, allowing for quantification of the effect of geofoam on seismic performance. It is shown that the presence of geofoam around the pile can reduce the seismic demand, rendering the proposed method a promising, inexpensive alternative to structural protective systems.
AB - The feasibility of a new geotechnical seismic isolation system for pile-supported structures, such as bridge piers on monopiles, is investigated. The isolation system utilizes a soft annular zone of viscoelastic material, such as EPS geofoam, around the upper part of the pile. The presence of the EPS elongates the fundamental natural period of the structure and also modifies its damping. For simplicity and as a proof of concept, the superstructure is considered a simple oscillator. Based on a dynamic Winkler model for pile-soil interaction, the problem is treated analytically leading to a simple design-oriented analysis method. Closed-form solutions are obtained for: (a) the lateral stiffness of the structure-foundation system, (b) the corresponding fundamental period, and (c) the overall damping. Numerical analyses in the frequency domain by means of the computer code SPIAB verify the above analytical predictions. Analyses in the time domain are also carried out to examine the effect of geofoam on the dynamic response. Results in terms of base shear, maximum pile bending moment, and displacement at deck level are presented in dimensionless form, allowing for quantification of the effect of geofoam on seismic performance. It is shown that the presence of geofoam around the pile can reduce the seismic demand, rendering the proposed method a promising, inexpensive alternative to structural protective systems.
KW - Bridge Pier
KW - EPS Geofoam
KW - Geotechnical Isolation
KW - Period Elongation
KW - Pile Foundations
UR - http://www.scopus.com/inward/record.url?scp=85042484980&partnerID=8YFLogxK
U2 - 10.7712/120117.5475.17924
DO - 10.7712/120117.5475.17924
M3 - Conference contribution
AN - SCOPUS:85042484980
T3 - COMPDYN 2017 - Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering
SP - 1042
EP - 1057
BT - COMPDYN 2017 - Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering
A2 - Papadrakakis, M.
A2 - Fragiadakis, Michalis
PB - National Technical University of Athens
T2 - 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, COMPDYN 2017
Y2 - 15 June 2017 through 17 June 2017
ER -