Assessment of Soil-Structure Interaction in Reinforced Concrete Buildings Based on Structure to Soil Stiffness Ratio

Abstract

Soil-structure interaction (SSI) results in higher structural damping ratio and elongated fundamental natural period of the building. Generally, these modifications on dynamic properties of the building are regarded to be favorable for dynamic response and SSI is neglected in most of the design codes. However, extensive research points out that neglecting the role of SSI can be a misconception that lead an unsafe design by underestimating the rotational ductility demand and top displacement of the building. Therefore, it is essential to determine if SSI is expected to be significant for safe design of the buildings. In this study, the significance of SSI in design is assessed with the help of the structure to soil stiffness ratio that is considered as the most important parameter controlling the period elongation. Stiffness ratio is determined for buildings with moment-resisting frames and varying number of storeys resting on different soil conditions and a threshold of 0.1 is assumed as the critical value that yields a period elongation of 5%. It is shown that, SSI should be taken into account for buildings founded on site classes ZE, ZD and ZC and can be neglected for site classes ZB and ZA.

Keywords

• Soil-structure interaction
• Period elongation
• Stiffness ratio

Betonarme Binalarda Zemin-Yapı Etkileşiminin Yapının Zemine Rijitlik Oranı Yardımıyla Değerlendirilmesi

Abstract

Zemin-yapı etkileşimi (ZYE) binanın periyodunu uzatırken yapısal sönüm oranını artırır. Binanın dinamik özelliklerindeki söz konusu değişim genellikle dinamik davranış açısından elverişli kabul edildiğinden ZYE tasarım yönetmeliklerinin birçoğunda ihmal edilmektedir. Fakat çok sayıda araştırma ZYE’nin ihmal edilmesinin binanın dönme sünekliği talebinin ve tepe deplasmanının olduğundan az hesaplanması yoluyla güvensiz tasarıma neden olduğunu işaret etmektedir. Bu sebeple ZYE’nin öneminin belirlenmesi güvenli tasarım için gereklidir. Bu çalışmada ZYE’nin tasarımdaki önemi periyot uzamasını kontrol eden en önemli parametre olan yapının zemine rijitlik oranı yardımıyla değerlendirilmiştir. Rijitlik oranı, faklı kat adedine sahip çerçeve taşıyıcı sisteme sahip binalarda farklı zeminler için hesaplanmış ve %5 periyot uzamasına sebep olan 0.1 değeri eşik kabul edilmiştir. ZYE'nin ZE, ZD ve ZC zeminlerde göz önüne alınması gerektiği, ZB ve ZA zeminlerde ihmal edilebileceği gösterilmiştir.

Keywords

• Zemin-yapı etkileşimi
• Periyot uzaması
• Rijitlik oranı

References

1. ASCE, 2010. Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-10, American Society of Civil Engineers, Virginia-USA, Erişim adresi: https://www.waterboards.ca.gov/waterrights/water_issues/programs/bay_delta/california_waterfix/exhibits/docs/dd_jardins/DDJ-148%20ASCE%207-10.pdf
2. Aydemir M.E., 2013. Soil structure interaction effects on structural parameters for stiffness degrading systems built on soft soil sites, Structural Engineering and Mechanics 45(5), 655-676.
3. Bazaios K., Gerolymos N., Bouckovalas G., Chaloulos Y., 2022. SSI effects on seismic settlements of shallow foundations on sand, Soil Dynamics and Earthquake Engineering 155, 107025.
4. Behnamfar F., Banizadeh M., 2016. Effects of soil–structure interaction on distribution of seismic vulnerability in RC structures, Soil Dynamics and Earthquake Engineering 80, 73-86.
5. Bielak J., 1976. Modal analysis for building-soil interaction, Journal of Engineering Mechanics 102, 771-786.
6. Bozdogan K.B., Ozturk D., Nuhoglu A., 2005. A practical method for dynamic analysis of multistorey buildings according to continuum approximation model, Journal of Engineering and Natural Sciences 4, 65-77.
7. Ciampoli M., Pinto P.E., 1995. Effects of soil-structure interaction on inelastic seismic response of bridge piers, Journal of Structural Engineering 121(5), 806-814.
8. CSI, 2022. SAP2000 Integrated Software for Structural Analysis and Design, Computers and Structures Inc., Berkeley, California-USA.

9. De Carlo G., Dolce M., Liberatore D., 2000. Influence of soil-structure interaction on the seismic response of bridge piers, 12th World Conference on Earthquake Engineering, Upper Hut, New Zealand, Erişim adresi: https://www.iitk.ac.in/nicee/wcee/article/0438.pdf
10. Elnashai A.S., McClure D.C., 1996. Effect of modelling assumptions and input motion characteristics on seismic design parameters of RC bridge piers, Earthquake Engineering and Structural Dynamics 25(5), 435-463.
11. FEMA, 2020. A Practical Guide to Soil-Structure Interaction, FEMA P-2091, Federal Emergency Management Agency, Washington, D.C.-USA, Erişim adresi: https://www.fema.gov/sites/default/files/documents/fema-p-2091-soil-structure-interaction.pdf
12. Forcellini D., 2021. A Novel Framework to Assess Soil Structure Interaction (SSI) Effects with Equivalent Fixed-Based Models, Applied Sciences 11(21), 10472.
13. Kara D., Bozdoğan K.B., Keskin E., 2020. Çerçeve sistemlerin yapı zemin etkileşimli serbest titreşim analizi, Politeknik Dergisi 23(4), 1347-1355.
14. Miranda E., Bertero V., 1994. Evaluation of strength reduction factors of earthquake-resistant design, Earthquake Spectra 10(2), 357-379.
15. Miranda E., Reyes C.J., 2002. Approximate lateral drift demands in multistory buildings with nonuniform stiffness, Journal of Structural Engineering 128(7), 840-849.
16. Mylonakis G., Gazetas G., 2000. Seismic soil-structure interaction: beneficial or detrimental?, Journal of Earthquake Engineering 4(3), 277-301.
17. Newmark N.M., Hall W.J., 1969. Seismic design criteria for nuclear reactor facilities, 4th World Conference on Earthquake Engineering, Santiago de Chile, Erişim adresi: https://www.iitk.ac.in/nicee/wcee/article/4_vol2_B4-37.pdf
18. NIST, 2012. Soil-Structure Interaction for Building Structures, NISTGCR - 12-917-21, National Institute of Standards and Technology, Maryland-USA, Erişim adresi: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915495
19. Ozgur M., Bozdogan K.B., 2022. Betonarme Binalarda Zemin-Yapı Etkileşiminin Sismik Tasarım Parametrelerine Etkileri, El Cezeri 9(2), 507-521.
20. Steward J.P., Seed R.B., Fenves G.L., 1999. Seismic soil-structure interaction in buildings. II: Empirical Findings, Journal of Geotechnical and Geoenvironmental Engineering 125(1), 38-48.
21. TBDY, 2018. Türkiye Bina Deprem Yönetmeliği, Afet ve Acil Durum Yönetimi Başkanlığı, Erişim adresi: https://www.afad.gov.tr/kurumlar/afad.gov.tr/2309/files/TBDY_2018.pdf
22. Veletsos A.S., Nair V.V., 1975. Seismic interaction of structures on hysteretic foundations, Journal of Structural Engineering 101, 109-129.
23. Xiong W., Jiang L.Z., Li Y.Z., 2016. Influence of soil–structure interaction (structure-to-soil relative stiffness and mass ratio) on the fundamental period of buildings: experimental observation and analytical verification, Bulletin of Earthquake Engineering 14(1), 139-160.