raft and soil-structure interaction pdisp and gsa raft
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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Raft and Soil-Structure InteractionPdisp and GSA Raft
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Peter Debney
Senior Consultant
Today’s Team
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1. Viewer Window 2. Control Panel
Raft and Soil-Structure Interaction
If you cannot hear, please
check this setting
GoToWebinar Attendee Interface
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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.
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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
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Oasys Customers
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Structural
Geotechnical
CAD
Document Management
Sustainability
Crowd simulation
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Soil Settlement and Soil-Structure Interaction Pdisp & GSA Raft
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Soil settlement and Soil-Structure interaction – is it a problem?
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Soil settlement and Soil-Structure interaction – is it a problem?
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What structures are affected?
Ground stiffer than structure – No
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What structures are affected?
Structure stiffer than ground – No
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What structures are affected?
Ground & structure similar stiffness– Yes
Structure sensitive to movement– Yes
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How does Pdisp and GSA Raft work?
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What is Pdisp?
• Calculates soil displacements under load
• Uses• Boussinesq (gives
stresses and displacements in soil)
• Mindlin (gives displacements only)
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What is GSA?
• Structural finite element analysis
• Linear and non-linear static
• Vibration• Buckling• Bridge loading• Form finding• Element design• Soil-structure interaction
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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
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GSA – Pdisp Iteration Solution
1. GSA assumes a spring stiffness
2. GSA analyses to get soil pressures & displacements
Soil pressure: p = f / AIf p < pmin then p = pmin
If p > pmax then p = pmax
3. Pdisp analyses spring forces to get soil settlements
4. GSA calculates new spring stiffnesses from forces & settlements
5. Repeat from 2 until GSA and Pdisp movements converged
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Soil Data
• Define soil properties in the vertical direction
Top levelEtop mEbot
rigid level – deformation below is ignored
Etop
mTop level
Ebot
Etop
m
Top level
Ebot
Layer 1
Layer 2
Layer 3
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Soil Data
• Define Soil Zones in plan
Zone 1 (profile i)
Zone 2 (profile j)
Zone 3 (profile k)
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Schematic view of piled-raft model
raft
piles
Non
-line
ar S
prin
gs
Soil
Soil
See next slide
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sy.b
Bx
By
Hsx
sy
tz
tz
sy.t
A pile section:represented by a single node on pile
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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
A node on pile
Representing soil: they all coincide with the node on pile
Non-linear springs with interaction
forces Fx, Fy & Fz
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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.
zzz
yyy
xxx
AF
AF
AF
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Pile-Soil Contact Stresses
• The pile-soil contact stresses equal pile-soil
interaction coefficient C times the soil strength, i.e.
zzz
yyy
xxx
fc
fc
fc
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Pile-Soil Interaction Coefficient
• The pile-soil interaction coefficient C shown below, is a function of:1. The relative displacements between piles and soil at
the relevant pile point2. The dimensions of the piles
1.0
-1.0
dx/By etc
c
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Pdisp and GSA Raft in action
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GSA Raft Case study
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Aspire Tower, Doha, Qatar
http://www.oasys-software.com/casestudies?id=14/
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Aspire Tower, Doha, Qatar
http://www.oasys-software.com/casestudies?id=14/
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Any Questions?