اثر وابستگی سختی دینامیکی خاک به فرکانس زلزله و تأثیر پارامترهای اندرکنشی بر پاسخ ارتجاعی و غیرارتجاعی سیستم‌های خاک - سازه

نوع مقاله : علمی - پژوهشی

نویسندگان

دانشکده مهندسی عمران، دانشگاه مازندران، بابلسر، ایران

چکیده

در تحلیل و طراحی لرزه‌ای سازه ها عموماً فرض می‌شود که خاک زیر شالوده صلب است و از انعطاف پذیری آن صرف نظر می‌گردد. با در نظر گرفتن انعطاف پذیری خاک زیر پی، انتظار می‌رود که پاسخ سازه تحت تأثیر متقابل اندرکنش دینامیکی سیستم خاک و سازه قرار گیرد. به طور کلی مقادیر مختلف پارامترهای موثر خاک و سازه بر پاسخهای لرزه ای تأثیرات متفاوتی خواهند گذاشت. در این مطالعه با استفاده از یک تحلیل پارمتریک، اثرات پارامترهای موثر خاک و سازه مانند جرم و اینرسی دورانی سازه و پی، نسبت سختی سازه به خاک، نسبت ارتفاع به بُعد سازه ، نسبت جرم سازه به جرم خاک و همچنین اثر وابستگی سختی دینامیکی خاک به فرکانس تحریک زمین بر پاسخ‌های ارتجاعی و غیرارتجاعی سازه مورد بررسی قرار گرفته است. در این پژوهش خاک زیر پی به روش مخروطی مدل شده است، و برای تحلیل سیستم خاک-سازه از روش زیرسازه استفاده شده است. نتایج بدست آمده حاکی از آن است که، وابستگی سختی دینامیکی خاک به فرکانس تحریک زمین، تأثیرقابل ملاحظه‌ای بر پاسخ غیرارتجاعی و ارتجاعی سازه‌های یک درجه آزاد نخواهد داشت. بنابراین می‌توان برای سازه‌های با شالوده‌های سطحی، با دقت قابل قبولی سختی دینامیکی خاک را به صورت مستقل از فرکانس مدل کرد. هرچند که پارمترهای موثر خاک-سازه نظیر نسبت جرم سازه به خاک، فرکانس بی‌بعد و نسبت لاغری تأثیر قابل توجهی بر پاسخ سیستمهای خاک-سازه با پی سطحی خواهند گذاشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Influence of frequency-dependent dynamic soil stiffness and interacting parameters on elastic and inelastic response of soil-structure systems

نویسندگان [English]

  • Behnoud Ganjavi
  • S. Reza Mousavi
Department of Civil Engineering, University of Mazandaran, Babolsar, Iran
چکیده [English]

In seismic analysis and design of structures, it is generally assumed that the soil beneath the foundation is rigid and, thus, its flexibility is not taken into account. Soil flexibility can affect the response of structures through complex phenomenon of dynamics soil-structure interaction effect. It is believed that effective soil and structural parameters could in some case significantly influence seismic response of structures in different manners and conditions. In this study, through an intensive parametric study, the effect of key parameters of soil-structures for both constant-strength and constant-ductility conditions are examined. In this regard, the effect of foundation mass, structure and foundation mass moment of inertia, structure-to-soil stiffness ratio, structural aspect ratio, the ratio of structural mass to soil mass, and, more importantly, the effect of frequency-dependent soil dynamic stiffness on the elastic and inelastic response of superstructures are investigated. The results of this study indicate that excitation frequency dependence, foundation mass and mass moment of inertia have insignificant effects on the base shear coefficient, displacement amplification factor of soil-shallow foundation systems. Nevertheless, other parameters such as soil foundation-to-structure mass ratio and dimensionless frequency and aspect ratio could have considerable effects on the response of the soil-shallow foundation SDOF systems.

کلیدواژه‌ها [English]

  • Soil-structure interaction
  • Displacement amplification factor
  • Base shear
  • Cone model
  • Excitation Frequency
[1] FEMA, Prestandard And Commentary For the Seismic Rehabilitation Of Buildings., (2000)., Washington, D.C.: Report FEMA 356, Federal Emergency Management Agency, 519.
[2] FEMA, NEHRP Recommended Provisions For Seismic Regulations For New Buildings And Other Structures., (2003)., Washington, D.C.: Report FEMA 450, Federal Emergency Management Agency, 356.
[3] Ganjavi, B., And Hao, H. (2014). Strength Reduction Factor for MDOF Soil-Structure Systems. The structural Design of Tall and Special Buildings, 23 (3), 163-180.
[4] Ahmadi, E., And Khoshnoudian, F. (2015). Near-fault effects on strength reduction factors of soil-MDOF structure systems. Soils and Foundations, 55(4), 841-856.
[5] Muller FP, And Keintzel E. (1982) Ductility requirements for flexibly supported anti-seismic structures. Proceedings of the Seventh European Conference on Earthquake Engineering, , 3, 27–34.
[6] Ganjavi, B., And Hao, H. (2012). A parametric study on the evaluation of ductility demand distribution in multi-degree-of freedom systems considering soil–structure interaction effects. Engineering Structures, 43, 88–104.
[7] Khoshnoudian, F., Ahmadi, E., & Nik, F. A. (2013). Inelastic displacement ratios for soil-structure systems. Engineering Structures, 57, 453-464.
[8] Eser, M., Aydemir, C., And Ekiz, I. (2012). Inelastic displacement ratios for structures with foundation flexibility. KSCE Journal of Civil Engineering, 16(1), 155-162.
[9] Ahmadi, E. And Khoshnoudian, F. (2013). Evaluation of maximum displacement factor for soil-structure systems, CSCE 2013 General Conference. Montreal, Québec, Canada: 95, 1.
[10] Ganjavi, B. Hajirasouliha, I. And Bolourchi, A. (2016). Optimum lateral load distribution for seismic design of nonlinear shear-buildings considering soil-structure interaction. Soil Dynamics and Earthquake Engineering, 88, 356-368.
[11] Cruz, C. And Miranda, E. (2017). Evaluation of soil-structure interaction effects on the damping ratios of buildings subjected to earthquakes. Soil Dynamics and Earthquake Engineering, 100, 183-195.
[1] FEMA, Prestandard And Commentary For the Seismic Rehabilitation Of Buildings., (2000)., Washington, D.C.: Report FEMA 356, Federal Emergency Management Agency, 519.
[2] FEMA, NEHRP Recommended Provisions For Seismic Regulations For New Buildings And Other Structures., (2003)., Washington, D.C.: Report FEMA 450, Federal Emergency Management Agency, 356.
[3] Ganjavi, B., And Hao, H. (2014). Strength Reduction Factor for MDOF Soil-Structure Systems. The structural Design of Tall and Special Buildings, 23 (3), 163-180.
[4] Ahmadi, E., And Khoshnoudian, F. (2015). Near-fault effects on strength reduction factors of soil-MDOF structure systems. Soils and Foundations, 55(4), 841-856.
[5] Muller FP, And Keintzel E. (1982) Ductility requirements for flexibly supported anti-seismic structures. Proceedings of the Seventh European Conference on Earthquake Engineering, , 3, 27–34.
[6] Ganjavi, B., And Hao, H. (2012). A parametric study on the evaluation of ductility demand distribution in multi-degree-of freedom systems considering soil–structure interaction effects. Engineering Structures, 43, 88–104.
[7] Khoshnoudian, F., Ahmadi, E., & Nik, F. A. (2013). Inelastic displacement ratios for soil-structure systems. Engineering Structures, 57, 453-464.
[8] Eser, M., Aydemir, C., And Ekiz, I. (2012). Inelastic displacement ratios for structures with foundation flexibility. KSCE Journal of Civil Engineering, 16(1), 155-162.
[9] Ahmadi, E. And Khoshnoudian, F. (2013). Evaluation of maximum displacement factor for soil-structure systems, CSCE 2013 General Conference. Montreal, Québec, Canada: 95, 1.
[10] Ganjavi, B. Hajirasouliha, I. And Bolourchi, A. (2016). Optimum lateral load distribution for seismic design of nonlinear shear-buildings considering soil-structure interaction. Soil Dynamics and Earthquake Engineering, 88, 356-368.
[11] Cruz, C. And Miranda, E. (2017). Evaluation of soil-structure interaction effects on the damping ratios of buildings subjected to earthquakes. Soil Dynamics and Earthquake Engineering, 100, 183-195.