Modelling of soil-structure interaction in OpenSees: A practical approach for performance-based engineering
- 1. Modelling of Soil-Structure Interaction in OpenSees: A Practical Approach for Performance-Based Engineering Smail Kechidi, Researcher, University of Porto Aires Colaço, Ph.D. Student, University of Porto Mário Marques, Post-Doctoral Researcher, University of Porto José Miguel Castro, Assistant Professor, University of Porto Pedro Alves Costa, Assistant Professor, University of Porto OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017
- 2. 1. Background and Motivation 2. Soil-Structure Interaction Modelling Tool • Formulation of the Problem • Model Implementation in OpenSees • Validation of the Proposed Model 3. Case Studies • Description of the Buildings • EC8-based Ground Motion Record Selection • Seismic Performance Assessment Approaches I and II (with and without Soil-Structure Interaction) Approach III (Soil-Structure Interaction and site effect) • Soil Factor 4. Conclusions 2/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Overview
- 3. Background and Motivation Layered Soil Input motion Bedrock motion Free surface motion ??? 3/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017
- 4. • Motivation for the research presented herein: • Building codes discourage designs that allow the mobilisation of the foundation capacity. • Development of a well-calibrated modelling tool, coupled with parameter selection protocols cast in a simplistic fashion. • Encourage the modelling of SSI within the community of practicing engineers • Is the prevailing belief, saying that ignoring soil-structure interaction leads to conservative results, always valid? 4/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Background and Motivation
- 5. • Formulation of the Problem Kbub + Cb ̇ub + Mb ̈ub = Fb us b = Δub + u ̇us b = Δ ̇ub + ̇u ̈us b = Δ ̈ub + ̈u �Fb = −Fs = −(KsΔu𝑏𝑏 + CsΔ ̇𝑢𝑢𝑏𝑏 + MsΔ ̈𝑢𝑢𝑏𝑏 𝐾𝐾 𝑎𝑎𝑎𝑎 𝐾𝐾 𝑎𝑎𝑎𝑎 𝐾𝐾 𝑏𝑏𝑏𝑏 𝐾𝐾 𝑏𝑏𝑏𝑏 + Ks 𝑢𝑢a 𝑢𝑢b + 𝐶𝐶 𝑎𝑎𝑎𝑎 𝐶𝐶 𝑎𝑎𝑎𝑎 𝐶𝐶 𝑏𝑏𝑏𝑏 𝐶𝐶 𝑏𝑏𝑏𝑏 + Cs ̇𝑢𝑢a ̇𝑢𝑢b + 𝑀𝑀𝑎𝑎𝑎𝑎 𝑀𝑀𝑎𝑎𝑎𝑎 𝑀𝑀𝑏𝑏𝑏𝑏 𝑀𝑀𝑏𝑏𝑏𝑏 + Ms ̈𝑢𝑢a ̈𝑢𝑢b = 0 Ksu + Cs ̇𝑢𝑢 + Ms ̈𝑢𝑢 5/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil-Structure Interaction Modelling Tool
- 6. Monkey-tail modelVertical vibrating surface footing resting on a homogeneous elastic half space 6/21 • Model Implementation in OpenSees OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil-Structure Interaction Modelling Tool
- 7. 7/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil-Structure Interaction Modelling Tool • Model Implementation in OpenSees
- 8. 8/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 • Validation of the Proposed Model Soil-Structure Interaction Modelling Tool
- 9. Vs30 = 800 m/s Vs30 = 360 m/s Vs30 = 180 m/s Vs30 = 100 m/s • Validation of the Proposed Model (SDOF) 9/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil-Structure Interaction Modelling Tool
- 10. Vs30 = 180 m/s Vs30 = 100 m/s • Validation of the Proposed Model (Oscillator) 10/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil-Structure Interaction Modelling Tool
- 11. Gravity designed frame “GB” Seismically design frame “SB3” (Lisbon, soil class C and q = 4) • Description of the Buildings 11/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Study
- 12. GB frame T1= 1.61 sec SB3 frame T1= 0.87 sec • EC8-Based Ground Motion Record Selection (SelEQ) 12/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Study
- 13. ug(t)ug(t) Fixed bases (Approaches I) SSI consideration using the Monkey-tail model (Approaches II) • Seismic Performance Assessment 13/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Studies
- 14. GB fame 2%/50 yrs. 10%/50 yrs. • Approaches I and II SB3 fame 14/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Studies
- 15. Layered Soil Rock Input motion 1- Deconvolution process 2- Convolution process Bedrock motion Free surface motion 15/21 • Approach III OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Studies
- 16. Vs30=360 m/s Vs30=180 m/s • Approach III 16/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Case Studies
- 17. 2%/50 yrs. 10%/50 yrs. • Approach III (SB3 frame) 17/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Vs30=360 m/s Vs30=180 m/s Case Studies
- 18. Vs30=360 m/s Vs30=180 m/s 18/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 • Approach III Case Studies
- 19. 2%/50 yrs.10%/50 yrs. 19/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Soil Factor
- 20. • Using lumped parameter models can be seen as a good option considering the compromise between accuracy of the solution and reduction of the computation effort. • Drifts considering the Soil-Structure Interaction are even larger in the lower stories than those of the fixed-base case. • Dependence of the amplification soil factor on the fundamental period of vibration, seismic intensity level and soil stiffness. 20/21OpenSees Days Europe 2017, First European Conference on OpenSees Porto, Portugal, 19–20 June 2017 Conclusions
- 21. Thank you for your attention! kechidi@fe.up.pt