bridge 3d soil structure interaction methods...

Integrated Solver Optimized for the next generation 64-bit platform

Finite Element Solutions for Geotechnical Engineering

Soil Structure Interaction using

midas Civil & midas GTS NX for

the Structural & Geotechnical Engineers

Bridge 3D Soil Structure Interaction

Methods Comparison



Contents

1. Introduction

2. Soil Structure Interaction Substructure Method

3. Ground Response Analysis for Calibration

4. Soil Structure Interaction Direct Method

5. Results Comparison Between SSI Methods

GTS NX

3

Soil Structure Interaction

SSI: The phenomenon in which the response of soil and movement of the structure influence each

other. When external forces, such as earthquakes, act on these systems, neither structural

displacements nor ground displacements are independent of each other. Unlike an above-ground

structure, the response of an underground structure subjected to an earthquake is mainly controlled

by the ground displacement. The ground displacement in turn is largely influenced by the dynamic

properties of the ground and its modeling method. The ground exhibits a complete nonlinear

behavior depending on the strains developed in the ground due to the dynamic load. It is therefore

important to closely examine the nonlinearity of the ground relative to strains.

GTS NX

4

Substructure Method Direct Method

Dynamic SSI




by Substructure Method

GTS NXSubstructure/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.

GTS NX

7

Initial Civil model dimensions

GTS NX

8

Add Soil Springs Supports

GTS NX

9

Time History Analysis Case

3

1

2

GTS NX

10

Results for TH in Civil using PY springs

Max Axial forces on structure (kN)

Max moments on structure (kN/m)

GTS NX

11

Results for TH in Civil using PY springs

Max displacements (cm)

Max Shear Forces (Kn)

GTS NXSubstructure/Indirect Method

The substructure-only approach:http://Northamerica.midasuser.com > Training > Review Courses

http://northamerica.midasuser.com/




by Direct Method

GTS NX

14

• Análisis Pushover de un marco tridimensional usado para diseño. Puede ser utilizado para concreto reforzado, acero

estructural y secciones compuestas de concreto-acero.

• Diseño basado en desempeño por FEMA, Eurocódigo 8 y Mampostería

Análisis Pushover para Mampostería

Definir materiales no lineales de rotulasEstado de Rótulas y Curva de Capacidad

Interaction with other software

GTS NXTools to check or verify mesh quality

GTS NX

To provide more reliable analysis results, GTS NX can automatically generate

hexahedral centered hybrid mesh. Hexahedral elements are the most stable for

stress and displacement results.

Hybrid Mesher

GTS NXExtensive Constitutive Model Data Base

GTS NX

18

GTS NX&

Civil

Linear Equivalent

Time History

Response Spectrum

Eigen Value

Dynamic Analysis

• Free Field

• Linear (Direct)

• Linear (Modal)

• Non linear (Direct)

• Non linear + SRM

• Liquefaction

• Moving Load

• 2D Linear Equivalent

GTS NX

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Linear Equivalent 1D and 2D

Weathered

soil

Landfill

Colluvial

Weathered

rock

Class I

RockBed

Rock

2D Linear EquivalentFree FieldDynamic Curve

GTS NX

20

Linear EQ (Free Field)

Short Time History Function (2 sec Analysis)

Max acceleration (12 m/sec^2)

GTS NX

21

Linear EQ

Add embankment to soil layer

Short Time History Function (2 sec Analysis)

Max acceleration (14.3 m/sec^2)



3D Time History Analysis

GTS NX

23

Use same dynamic curve and time

history function

Dynamic SSI

Free Field 1D

Linear Equivalent 2D

Time History 3D

GTS NX

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Define 3D LTH Material (Ground Only)

GTS NX

25

2

3D LTH Loads and Boundaries (ground only)

1 45

6

3

GTS NX

26

3D Linear Time History Results (ground only)

Results for Linear Time History is within 5%. Max of 11.8 m/sec^22 sec Analysis*

3

GTS NX

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3D Linear Time History Results

GTS NX

28

• Análisis Pushover de un marco tridimensional usado para diseño. Puede ser utilizado para concreto reforzado, acero

estructural y secciones compuestas de concreto-acero.

• Diseño basado en desempeño por FEMA, Eurocódigo 8 y Mampostería

Análisis Pushover para Mampostería

Definir materiales no lineales de rotulasEstado de Rótulas y Curva de Capacidad

Interaction with other software

GTS NX

29

3D SSI

GTS NX

30

Import model to GTS NX

1

3

2

GTS NX

31

Mesh CAD in 3D elements

GTS NX

32

3D SSI Results

Results for Time History is within 5%. Max of 14.2 m/sec^2

3

GTS NX

33

Dynamic results for imported bridge

Max Axial forces on structure

Max moments on structure

GTS NX

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Results Comparison

GTS NX

35

Bridge with updated substructure

Max Acceleration

GTS NX

36

Max Shear Forces

Max Displacements

Results for Bridge with updated substructure

GTS NX

37

Results for Bridge with updated substructure

Max Axial forces on structure

Max moments on structure

GTS NX

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Max Civil GTS NX Updated Base

Displacements (cm) 29 28 23

Axial Force (kN) 3,064 2,036 1,762

Moments Y (kN/m) 19,087 23,969 16,127

Shear Forces (kN) 2,032 5,838 2,404

• Midas Civil has internal PY curves in order to easily apply soil springs and run soil structure interaction through substructure method. For some soils, this is sufficient.

• Substructure Method cannot accurately capture the non linear behavior experienced by the foundation and surrounding ground during an earthquake.

• Midas GTS NX can import full structure from midas Civil to run SSI through Direct Method. However, since the ground is modeled in 3D, it must first be calibrated through comparison of ground response analysis like Free Field and Linear Equivalent.

Conclusion

GTS NX

39

Other SSI problems (Adjacent Structure consideration)

GTS NX

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Initial Stage Excavation stage 1

Excavation stage 2 Final Excavation stage

Adjacent Structure consideration during excavation

GTS NX

41

Moments on tunnel Axial forces on rock bolts

Axial forces on bridge Moments on bridge

Adjacent Structure consideration during excavation

GTS NX

42

Thank You

bridge 3d soil structure interaction methods...

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