Soil-Structure Interaction for Piled-Raft Foundation

Transcription

1 MIDAS Geotechnical Know-how Sharing Series Session 1. Soil-Structure Interaction for Piled-Raft Foundation JaeSeok Yang Principal Geotechnical Engineer, MIDAS IT Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

2 01 Introduction 02 SSI by Substructure Method 03 SSI by Direct Method 04 Case Study Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

3 Soil Structure Interaction Schematic Diagram of Ground Response Analysis 3

4 Soil Structure Interaction for a Bridge Substructure Method Direct Method 4

5 01 Introduction 02 SSI by Substructure Method 03 SSI by Direct Method 04 Case Study Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

6 Soil Modeling for Structural Design 6

7 Determination of Soil Springs 7

8 Foundation Response 8

9 Foundation Response - Rigid Raft 9

10 Foundation Response - Flexible Raft 10

11 Foundation Response 11

12 Determination of Modulus of Subgrade Reaction 12

13 Determination of Modulus of Subgrade Reaction 13

14 Substructure (Indirect) Method The soil-structure interaction is reflected with soil spring data. The soil spring data may be applied to the substructure-only model with the superstructure load applied. The soil spring data may be applied to the entire structure model with both the super and substructure. 14

15 01 Introduction 02 SSI by Substructure Method 03 SSI by Direct Method 04 Case Study Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

16 Bearing Behavior of a Piled Raft 16

17 Requirements of a Numerical Model for Piled Raft 17

18 Work Flow of Pile Modeling 18

19 Iterative Process General Steps 19

20 Pile Modeling in 20

21 Solid Element Model 21

22 Solid Element Model 22

23 Beam-Solid Connectivity Model 23

24 Beam-Solid Connectivity Model 24

25 Line-to-Solid Interface Model 25

26 Line-to-Solid Interface Model 26

27 Point-to-Solid Interface Model 27

28 Pile Modeling in 28

29 Pile Modeling in 29

30 Line-to-Solid Interface Elements 30

31 Pile Element Parameters 31

32 Pile Element Parameters 32

33 Verification 33

34 Verification 34

35 Interaction between MIDAS Programs 35

36 Interaction between MIDAS Programs 36

37 Interaction between MIDAS Programs 37

38 Interaction between MIDAS Programs 38

39 Interaction between MIDAS Programs 39

40 Interaction between MIDAS Programs 40

41 Interaction between MIDAS Programs 41

42 Interaction between MIDAS Programs 42

43 01 Introduction 02 SSI by Substructure Method 03 SSI by Direct Method 04 Case Study Integrated Solver Optimized for the next generation 64-bit platform Finite Element Solutions for Geotechnical Engineering

44 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 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. 44

45 Building Details 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 168 m Total of 18 columns A total dead load of 300,000 kn 45

46 Building Details Piled raft foundation 106 piles CFA Continuous Flight Auger - Piles 100 cm diameter (piles) 30 m long (piles) 680 m² (raft) 168 m 46

47 Depth (m) Soil Characterization Site Investigation 5 SPT 50 meters deep 4 CPTu 43 meters deep SPT N (Blows/30 cm) CPT qt (MPa) U 0, U 2 (kpa) Fz 1 Silty Sand Clay Sand Silty Clay Sand Silty Clay Sedimentary deposit Excess of porewater pressure Low capacity profile Layered soil alternating sand and clay Clayey Silt

48 Settlement (mm) Pile Load Testing Program 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 model Load Test LOAD (kn) Theoretical prediction 30 m 100 cm 48

49 Pile Load Testing Program Reaction Piles Reaction Beam Hydraulic Jack Load Cell 49

50 Structural Model Autodesk Revit 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. 50

51 Structural Model midas Gen 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. 51

52 50m Geotechnical Model midas Soil layers Failure Criteria / Constitutive models Mohr-Coulomb for sands Modified Cam-clay for clays 100m 100m Piled Raft model Concrete elastic properties 3.5 m thick raft as a solid element 106 piles as beam elements 52

53 Geotechnical Model midas Pile Model Type Line-to-Solid Interface Model Model = Soil (solid) + Pile (line) + Interface (line-to-solid) 53

54 Settlement (mm) Geotechnical Model midas 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 LOAD (kn) PCE Décourt hyperbolic FEM Model 54

55 Geotechnical Model midas 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 55

56 Results Settlements Total settlement; Differential settlement Analysis; Angular distortion Analysis. 56

57 Results Pile Loads Distribution of load along the pile. Pile Springs 57

58 Results Pile bending moments Distribution of bending moments along the pile. 58

59 Conclusions Successful interaction between platforms Revit + Midas GEN + Midas Key results (): 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. 59

60 Q & A 60