Session 1. Soil-Structure Interaction for Piled-Raft...
Transcript of Session 1. Soil-Structure Interaction for Piled-Raft...
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
Session 1.
Soil-Structure Interaction for Piled-Raft Foundation
MIDAS Geotechnical Know-how Sharing Series
JaeSeok Yang Principal Geotechnical Engineer, MIDAS IT
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
01 Introduction
02 SSI by Substructure Method
03 SSI by Direct Method
04 Case Study
GTS NX
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Soil Structure Interaction
Schematic Diagram of Ground Response Analysis
GTS NX
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Substructure Method Direct Method
Soil Structure Interaction for a Bridge
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
01 Introduction
02 SSI by Substructure Method
03 SSI by Direct Method
04 Case Study
GTS NX
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Soil Modeling for Structural Design
GTS NX
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Determination of Soil Springs
GTS NX
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Foundation Response
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Foundation Response - Rigid Raft
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Foundation Response - Flexible Raft
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Foundation Response
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Determination of Modulus of Subgrade Reaction
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Determination of Modulus of Subgrade Reaction
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The soil-structure interaction is reflected with soil spring data.
• The soil spring data may be applied to the substructure-only model with the super-
structure load applied.
• The soil spring data may be applied to the entire structure model with both the super
and substructure.
Substructure (Indirect) Method
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
01 Introduction
02 SSI by Substructure Method
03 SSI by Direct Method
04 Case Study
GTS NX
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Bearing Behavior of a Piled Raft
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Requirements of a Numerical Model for Piled Raft
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Work Flow of Pile Modeling
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Iterative Process General Steps
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Pile Modeling in GTS NX
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Solid Element Model
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Solid Element Model
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Beam-Solid Connectivity Model
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Beam-Solid Connectivity Model
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Line-to-Solid Interface Model
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Line-to-Solid Interface Model
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Point-to-Solid Interface Model
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Pile Modeling in GTS NX
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Pile Modeling in GTS NX
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Line-to-Solid Interface Elements
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Pile Element Parameters
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Pile Element Parameters
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Verification
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Verification
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
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Interaction between MIDAS Programs
Integrated Solver Optimized for the next generation 64-bit platform
Finite Element Solutions for Geotechnical Engineering
01 Introduction
02 SSI by Substructure Method
03 SSI by Direct Method
04 Case Study
GTS NX
44
1
2
3
1 Geometry created by the structural team is replicated in Autodesk Revit
2 Converted to a structural model in Midas GEN
3 Imported and analyzed with the ground in Midas GTX NX.
Introduction
The focus of the case study will be a soil structure interaction analysis of a 55 story (168 m) building, in a layered soil down to 50 meters.
Due to the geotechnical condition and the size of the building, a SSI was necessary, providing prevision of settlements, and how those influence the behavior of the structure.
The presentation is mainly focused in the attempt of unifying different platforms and briefly describing the used process.
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The building comprises 55 story, resulting in 168 m high, being inside the top 25 tallest buildings in Brazil. Designed in full reinforced concrete structure Area of each story: 440 m² Total of 18 columns A total dead load of 300,000 kN
168 m
Building Details
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• Piled raft foundation • 106 piles • CFA – Continuous Flight Auger - Piles • 100 cm diameter (piles) • 30 m long (piles) • 680 m² (raft)
168 m
Building Details
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0 5 10 15 0 1 1
Clay
Silty Sand
Fz
Sand
Silty Clay
Silty Clay
Clayey Silt
Sand
0 1000 2000
0
5
10
15
20
25
30
35
40
45
50
0 20 40
Dep
th (
m)
• Sedimentary deposit
• Excess of porewater pressure
• Low capacity profile
• Layered soil alternating sand and clay
SPT N (Blows/30 cm)
CPT qt (MPa)
U0, U2
(kPa)
5 SPT – 50 meters deep
4 CPTu – 43 meters deep Site Investigation
Soil Characterization
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• Static load tests • Prior to the foundation construction • 3 CFA Piles (diameter of 80, 100 and 120 cm) • Maximum load of 9 MN • Results used to calibrate GTS NX model Load Test
30 m
100 cm
LOAD (kN)
Sett
lem
ent
(mm
)
Theoretical prediction
Pile Load Testing Program
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Hydraulic Jack
Reaction Piles
Reaction Beam Load Cell
Pile Load Testing Program
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• Geometry created by the structural team is replicated in Autodesk Revit, including:
• Materials; • Sections; • Properties; • Analytical model; • Loads.
• Using the Revit-Midas/GEN link, the model can be updated between the platforms.
Structural Model – Autodesk Revit
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• Revit’s model was imported in Midas GEN:
• Imported data: • Materials; • Sections; • Properties; • Loads.
• Input in GEN: • Story information; • Initial boundary condition; • Wind loads;
• Using the export option, a Midas MXT file was created to make the link with Midas GTS NX.
Structural Model – midas Gen
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• Soil layers • Failure Criteria / Constitutive models
• Mohr-Coulomb for sands • Modified Cam-clay for clays
• Piled Raft model • Concrete elastic properties • 3.5 m thick raft – as a solid element • 106 piles – as beam elements
50
m
100m 100m
Geotechnical Model – midas GTS NX
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• Pile Model Type – Line-to-Solid Interface Model
Model = Soil (solid) + Pile (line)
+ Interface (line-to-solid)
Geotechnical Model – midas GTS NX
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• Pile load test calibration • Reproduce the geometry of the pile load test; • Define different load steps to read the settlements; • Class C prediction • Compare to the pile load test Load x Settlement
curve
0
20
40
60
80
100
120
0 2500 5000 7500 10000
PCE
Décourt hyperbolic
FEM Model
LOAD (kN)
Sett
lem
ent
(mm
)
Geotechnical Model – midas GTS NX
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+ +
• Full Model • Soil + Piled-Raft + Structure
• Advantages: • More accurate values of differential settlements, due to
the rigidity/stiffness of the superstructure; • Evaluation of wind load cases directly;
GEN
Geotechnical Model – midas GTS NX
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• Settlements • Total settlement; • Differential settlement Analysis; • Angular distortion Analysis.
Results
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• Pile Loads • Distribution of load along the pile.
• Pile Springs
Results
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• Pile bending moments • Distribution of bending moments along the pile.
Results
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• Successful interaction between platforms
Revit + Midas GEN + Midas GTS NX
• Key results (GTS NX):
• Settlements from the piled raft foundation;
• Distribution of bending moment in piles;
• Springs can be exported, being different for each pile;
• Area springs can be exported, simulating the contact of the raft with the soil.
• Working in the same platform reduces the number of iterations between the structural and geotechnical teams.
• Midas offers two powerful platforms – for structural and geotechnical engineering – that are evolving to work together, in a full model, taking SSI to another level.
Conclusions
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Q & A