3D Dynamic Analysis of machine vibrations on foundation ...

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3D Dynamic Analysis of machine vibrations on foundation and structure

By Angel Francisco Martinez



ContentsPart 1. Introduction

Part 2. Concepts of Dynamic Loads

Part 3. 3D Raft Foundation Model

Part 4. 3D Metallic Plant Model



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General Pre & Post Processor

for Finite Element Analysis

Integrated Design System

for Building and General Structures

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Edificios y Estructuras Generales

2D / 3D Geotechnical and Tunnel

analysis System

midas GTS NX

SoilWorks

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GTS NX

Dynamic loads are used to apply various changing load conditions for linear/nonlinear time history

analysis. The total load vector in time history analysis is defined as the following function of time, . t

Here, is the j th load scale and it is generally defined as a tabular data form for time, or by

inputting coefficients for a particular function

Dynamic load

GTS NX

The nonlinearity of the system often results from material nonlinearity or geometric nonlinearity. In addition, there are cases where nonlinear analysis is needed for systems with load nonlinearity. For example, when the load direction changes with the structural displacement or when the load size is dependent on the structural behavior. GTS NXL can reflect the effects of follower loads, where the load direction changes with the structural displacement when performing geometric nonlinear analysis.

Nonlinearity of Loads

When the nodal force direction is determined by the relative position of two different points, its size and

direction are as follows:

GTS NX

11

Geometry Import

Define Materials

Mesh generation

Boundary Conditions

Dynamic Load Conditions

Eigenvalue Analysis

STEP 01

STEP 02

STEP 03

STEP 04

STEP 05

STEP 06

TH Analysis CaseSTEP 07

STEP 08 Perform analysis and check result

Overview

GTS NX

12

00 Material for Soil

Name Weathered Soil Concrete

Material Isotropic Isotropic

Model Type Mohr-Coulomb Elastic

General

Elastic Modulus (E) (ton/m^2) 3,000 2200000

Poisson’s Ratio(v) 0.35 .3

Unit Weight(r) (ton/m^3) 1.9 2.5

K0 1 1

Porous

Unit Weight(Saturated) (ton/m^3) 2 2.5

Non-Linear

Friction Angle 30

Cohesion (ton/m^2) 1.8

GTS NX

13

00 Property for Soil

Name Weathered Soil Concrete

Property 3D 3D

Model Type Solid Solid

Material Weathered Soil Concrete



Modeling Procedure

GTS NX

Procedure

1-15

01 Create New Project

11

Main Menu > New

Analysis Setting > Model

Type > 3D

Set units to tonf / m / sec

2

2

GTS NX

Procedure

1-16

02

1

1

Main Menu > Import > CAD File

Select Vibration Load 3d geometry >

Open

Select OK

2

3

3

Geometry works (Create or Import from AutoCAD)

2

GTS NX

Procedure

1-17

03 Define Material / Property for Soil & Structures

1

Mesh > Prop. > Property >

Create > 3D

Define 3D n properties for

both materials

•Define Materials and Properties

Material > Create > Isotropic

Define the 2 materials based on

properties from table in previous

slide

1

2

2

2

1

GTS NX

Procedure

1-18

04 Generate Mesh (3D Element)

1 Mesh > Generate > 3D > Auto Solid

Select Edge(s) > Select 2 soilds

highlighted in figure.

Input element Size : 0.5

(0.5m between two nodes)

Select Property : foundation 3d

Input Mesh Set Name : foundation

Click APPLY

2

2

3

4

5 3

4

5

6

6

1

1

GTS NX

Procedure

1-19

04 Generate Mesh (3D Element)

1 Mesh > Generate > 3D > Auto - Solid

Select Edge(s) > Select 2 solids

highlighted in figure.

Input element Size : 2

(1m between two nodes)

Select Property : weathered soil

Input Mesh Set Name : weathered soil

Click APPLY

2

2

3

4

5

3

4

5

6

6

1

1

GTS NX

Procedure

1-20

05 Define Dynamic Boundary Conditions

Mesh > Element > Other > Ground Surface

Springs

Select the 2 ground mesh sets

Press OK

1

2

3

3

1

2

1

2

GTS NX

Procedure

1-21

06 Analysis Case

1

Create EigenValue Analysis Cases

1. Analysis > Analysisi Case >

General > Eigenvalue

2. Activate All Sets

3. Analysis Control > 30 Modes

4. Press OK > OK

2

31

2

3

3

4

4

4

GTS NX

Procedure

1-22

07 Perform Analysis and Check Results

1 Analysis > Analysis > Perform

Select OK

1

2

2

GTS NX

Procedure

1-23

08 Post Processing (Results)

* After analysis, model view will be

converted to Post-Mode automatically,

can back to Pre-Mode to change model

information.

1 1

Results can be Viewed in table

format.

Find the 2 highest mass

participation modes in T3 (vertical direction)

and write down their corresponding periods.

MODE 3: 1.108514 sec

MODE 4: 1.294852 sec

3

2

GTS NX

Procedure

1-24

09 Define Dynamic Boundary Conditions

Mesh > Element > Other > Dampers

Select the ground mesh set

Select Damping Constant / Area option

Name set as : Dampers

Press OK

1

2

3

4

1

2

1

2

3

4

5

5

GTS NX

Procedure

1-25

10 Define Dynamic Load

• Create the cyclic load condition for

the time history analysis case.

Work Tree > Analysis > Time Forcing

Function > Add

1

Select Add Time Function

Open Excell file and copy the coulmns as

shown in the image.

Paste into the Time History Load Function

chart

Select Force under Time Function Type

Press OK > Close

3

2

3

2

1

4

4

6

6

5

5

6

GTS NX

Procedure

1-26

11 Apply Dynamic Load

• Apply the cyclic load to the

foundation surface.

Dynamic Analysis > Dynamic Load

1

Select the nodes on the top of the foundation

Assign Tz: -1

Select ‘LOAD’ for Time Function

Press OK

3

2

1

4

5

2

3

4

5

2

GTS NX

Procedure

1-27

12 Analysis Case (Linear Time History)

1

Create Linear Time History Analysis

Case

Analysis > General > Linear Time

History Direct

Activate all sets except Ground

Surface Springs

Define Time Step

Name: time

Time Duration: 0.5 sec

Time Increment:: 0.005 sec

Intermediate Output:: 1

Press Add > OK

Analysis Control > Dynamic >

Damping Method

-Select > Calculate from Modal

Damping > Period

-Type in the 2 periods from

Eigenvalue results

-Damping Ratio : 0.05

Press OK>OK

2

3

1

2

3

4

4

4

4

5

5

6

3

GTS NX

Procedure

1-28

13 Perform Analysis and Check Results

1 Analysis > Analysis > Perform

Select Linear Time History

Select OK

1

3

2

3

2

GTS NX

Procedure

1-29

1 Inspect results to dynamic load

Incr = 1 > Displacements > Total

Translation. Deactivate 1 ground and 1

foundation mesh set to see plane cut.

Switch units to mm

Navigate the results over time steps by

clicking on the bar under the model

and pressing the right button on key

board to go forward

2

14 Post Processing (Post mode)

1

2

GTS NX

31

3D Modeling

• Modeling in midas GTS NX

- Import Structure from Gen

- Create Solid Ground

- Assing Size Control to base to match nodes

GTS NX

Mesh Generation• Generate Mesh and Create Elements

- Ground material and structural properties

- Generate mesh for ground, and structure

- Generate Ground Surface Springs

GTS NX

Eigenvalue• Run Eigen Value analysis

- Find the modes with highest mass

participation in z direction (T3)

- Write down the 2 periods for mode numbers

GTS NX

34

Load & Dampers

• Load Conditions

- Dynamic Cycle Load

• Boundary Conditions

-Dampers

GTS NX

35

Non linear time history• Set parameters

-Time Steps

- Define periods for mass and stiffness proportional

damping

GTS NX

36

Post-Processing• Report Ready Results

- Extract Results for time steps

- Settlement Profile over time

- Graph Axial forces on column

- Stresses on soil



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3D Dynamic Analysis of machine vibrations on foundation ...

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