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Raft and Soil-Structure Interaction Pdisp and GSA Raft

Raft and Soil-Structure Interaction Pdisp and GSA Raft. Today’s Team. Peter Debney Senior Consultant. GoToWebinar Attendee Interface. 1. Viewer Window. 2. Control Panel. If you cannot hear, please check this setting. Raft and Soil-Structure Interaction. Agenda. Product demonstration

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Raft and Soil-Structure Interaction Pdisp and GSA Raft

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  1. Raft and Soil-Structure InteractionPdisp and GSA Raft

  2. Today’s Team Peter Debney Senior Consultant

  3. GoToWebinar Attendee Interface 1. Viewer Window 2. Control Panel If you cannot hear, please check this setting Raft and Soil-Structure Interaction

  4. Agenda • Product demonstration • Pdisp • GSA Raft • Questions and Answers NB: this webinar is designed as an introduction to Pdisp and GSA Raft and to provide an overview of functionality. If more is required then it can be done at a later date on an individual basis.

  5. Who is Oasys? • Wholly owned by Arup • Formed in 1976 to develop software for in-house and external use • Most developers are engineers who have moved to programming • In recent years have added marketing and sales staff • Since 2003 have expanded the development team worldwide

  6. Oasys Customers

  7. Structural Geotechnical Document Management Crowd simulation CAD Sustainability

  8. Soil Settlement and Soil-Structure Interaction Pdisp & GSA Raft

  9. Soil settlement and Soil-Structure interaction – is it a problem?

  10. Soil settlement and Soil-Structure interaction – is it a problem?

  11. What structures are affected? Ground stiffer than structure – No

  12. What structures are affected? Structure stiffer than ground – No

  13. What structures are affected? Ground & structure similar stiffness– Yes Structure sensitive to movement– Yes

  14. How does Pdisp and GSA Raft work?

  15. What is Pdisp? • Calculates soil displacements under load • Uses • Boussinesq (gives stresses and displacements in soil) • Mindlin (gives displacements only)

  16. What is GSA? • Structural finite element analysis • Linear and non-linear static • Vibration • Buckling • Bridge loading • Form finding • Element design • Soil-structure interaction

  17. What is GSA Raft? • Combination of GSA and Pdisp • Soil-structure interaction: • Vertical for rafts • Vertical & Horizontal for piles • Choice of methods • Boussinesq (rafts) • Mindlin (rafts and piles) • Iterative process

  18. GSA – Pdisp Iteration Solution • GSA assumes a spring stiffness • GSA analyses to get soil pressures & displacements Soil pressure: p = f / A If p < pmin then p = pmin If p > pmax then p = pmax • Pdisp analyses spring forces to get soil settlements • GSA calculates new spring stiffnesses from forces & settlements • Repeat from 2 until GSA and Pdisp movements converged

  19. Etop Top level m Layer 1 Ebot Etop Top level m Layer 2 Ebot Etop Top level m Layer 3 Ebot rigid level – deformation below is ignored Soil Data • Define soil properties in the vertical direction

  20. Zone 2 (profile j) Zone 3 (profile k) Zone 1 (profile i) Soil Data • Define Soil Zones in plan

  21. Schematic view of piled-raft model raft Non-linear Springs piles Soil Soil See next slide

  22. sy.t tz sx tz H sy sy.b By Bx A pile section:represented by a single node on pile

  23. Non-linear soil springs • Every nodes on the piles are connected by 3 non-linear springs to represent the soil non-linear behaviour immediately around the piles in x, y & z directions. The non-linear springs are then attached to the ground (soil). The soil is still considered as elastic media that the settlements are calculated using Mindlin method Non-linear springs with interaction forces Fx, Fy & Fz Representing soil: they all coincide with the node on pile A node on pile

  24. Interaction Forces • The interaction forces in the non-linear springs will be the interaction forces between pile and soil • The interaction forces equal the pile-soil contact stress times the interaction area, i.e.

  25. Pile-Soil Contact Stresses • The pile-soil contact stresses equal pile-soil interaction coefficient C times the soil strength, i.e.

  26. Pile-Soil Interaction Coefficient • The pile-soil interaction coefficient C shown below, is a function of: • The relative displacements between piles and soil at the relevant pile point • The dimensions of the piles c 1.0 dx/By etc -1.0

  27. Pdisp and GSA Raft in action

  28. GSA Raft Case study

  29. Aspire Tower, Doha, Qatar http://www.oasys-software.com/casestudies?id=14/

  30. Aspire Tower, Doha, Qatar http://www.oasys-software.com/casestudies?id=14/

  31. Any Questions?

  32. Contact us: oasys@arup.com /products/engineering/gsa-raft.html

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