Innovation Intelligence®
Physical Component Modeling
in Altair ScicosPro
Application to Vibratory Pile Extraction
Franck D...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Presentation Outline
• Physic...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
ScicosPro and Physical Compon...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
ScicosPro – Hybrid System Mod...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Causal modeling (explicit blo...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
To create a model with explic...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Constructing the model using ...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
• Have implicit ports (not a ...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
• Connected with special link...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
What is Modelica?
• Declarati...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Modelica Applications
• Model...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Physical Component modeling b...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
ScicosPro model, with Coselic...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Coselica Examples in ScicosPr...
Innovation Intelligence®
Physical Component Modeling in ScicosPro
Application to Vibratory Pile Extraction
Study made by D...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Application Goals
A 23m long ...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Vibratory Piles
Pile Properti...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling
Motivation
• W...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Pile Shaft Resistance
The sha...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Pile Shaft Resistance
Shaft R...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Pile Shaft Resistance
21
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling
We are applyin...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Rigid Pile
T...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Rigid Pile
D...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Rigid Pile
S...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Elastic Pile...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Elastic Pile...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Static Pulling – Elastic Pile...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling
We are replac...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling – Rigid Pile
...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling – Rigid Pile
...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling – Elastic Pil...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling – Elastic Pil...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Dynamic Pulling – Elastic Pil...
Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Conclusions
On the results
Vi...
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Modeling and Simulation of Vibratory Extraction of Piles

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In the realm of special deep foundation technology vibrators are used to drive, i.e. insert and extract, various piles (steel sheet piles, in-situ concrete driven piles,. . .) into the ground. Successful application of this method bears a major advantage, the static force needed for insertion or extraction (pulling) is relatively small. However, success depends strongly on soil properties and thus the right choice of a vibrator. In practise, a number of questions arise: “What is the smallest vibrator suitable for the job?”, “How long will it take to insert/extract a pile?”, and “Does the elasticity of the pile matter?”. We have developed a model in order to simulate the vibratory extraction process of a pile. The pile was modeled in two different ways, either by a simple rigid body or by a few coupled lumped masses. Soil parameters were derived from CPT (cone penetration test) results and taken into account. They are varying with respect to the piling depth. Simulations of both modeling variants (rigid and elastic pile) have been carried out. Based on the simulation results it was possible to give reasonable answers to the questions posed. This work is a first step towards dynamic simulation of the vibratory pile driving process in the daily routine of civil/geotechnical engineers. The model will be enhanced in the future to handle pile insertion as well. The models were implemented and simulated within Altair HyperWorks using the brand new ScicosPro tool. Which allowed us to use the state-of- the-art physical modeling technique and saved us a lot of time.

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Modeling and Simulation of Vibratory Extraction of Piles

  1. 1. Innovation Intelligence® Physical Component Modeling in Altair ScicosPro Application to Vibratory Pile Extraction Franck Delcroix European ATC - June 25th 2014, Munich
  2. 2. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Presentation Outline • Physical Component Modeling in ScicosPro • The Coselica Library • Application – Vibratory Pile Extraction 2
  3. 3. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. ScicosPro and Physical Component Modeling ScicosPro is made for system level modeling approaches (efficient handling of discrete time and events). Modelica is adapted to component level modeling approaches. But the basic formalisms are compatible, which allows for the use of Modelica components in a ScicosPro model. ScicosPro offers a Physical Component Modeling library based on Modelica blocks (Coselica library) 3
  4. 4. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. ScicosPro – Hybrid System Modeling Conventional ScicosPro blocks have clearly defined input and output ports, where an input can be regarded as cause and an output as effect. Models built solely with these blocks are causal models. In contrast, most Modelica blocks have neither identifiable input nor output ports. Instead, they have connector ports which propagate physical quantities (e.g. electrical voltage and current), and it is a priori undecided what quantity causes which effect. 4
  5. 5. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Causal modeling (explicit blocks)      DuCxy BuAxx an explicit block in ScicosPro • Input and output ports are explicitly defined • In the model there is an information flow • The input/output behavior is expressed in C • They are considered as black boxes by ScicosPro 5
  6. 6. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. To create a model with explicit blocks, you need • to obtain all the equations • to simplify the equations to obtain a differential equation (ODE/DAE)             C CR C C CRs VOutput RIV C I V VVV 0 RC V RC V V CS C  CV  Causal modeling (explicit blocks) model equations differential equation 6
  7. 7. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Constructing the model using explicit blocks based on the ODE can be time consuming, error prone, and show no resemblance to the original diagram. CV  Causal modeling (explicit blocks) 7
  8. 8. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. • Have implicit ports (not a priory inputs or outputs) • Each implicit block represents a physical component dt dV CI C C  an implicit block in ScicosPro Acausal modeling (implicit blocks) 8
  9. 9. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. • Connected with special links (no flow direction) • Modeling is just connecting the components • The model looks like the physical system • The behavior is expressed in the Modelica language Acausal modeling (implicit blocks) 9
  10. 10. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. What is Modelica? • Declarative instead of procedural • Object oriented modeling language (inheritance, aggregation) • Typed language • Allows heterogeneous models (multi-domain models) • Allows reuse of physical models • Allows non-causal modeling (modeling using components) • Equation based, i.e., using mathematical equations • Hybrid modeling, i.e., event-based and continuous-time models 10
  11. 11. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Modelica Applications • Modelica is a non proprietary language and exists since 1996. It is Standardized by Modelica Association. • The Modelica models, being independent of the tool, can be simulated on any Modelica simulator. • Available tools include: MapleSim, Dymola, SimulationX,… • Several free and commercial libraries are available. 11
  12. 12. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Physical Component modeling blocks in ScicosPro Coselica is library of ScicosPro blocks based on the Modelica Standard Library. It is essentially a library of physical components covering various physical domains, such as mechanics, electrics/electronics, and thermodynamics. These components are provided as ScicosPro blocks and they can be found in one hierarchical palette named Coselica. All blocks have special connector ports and connecting them is like assembling a physical network. 12
  13. 13. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. ScicosPro model, with Coselica blocks and standard blocks How does it work in ScicosPro? C Block 13
  14. 14. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Coselica Examples in ScicosPro Hatch Mechanism – Mechanical/Electrical modelingHeat Transfer and Convection – Thermal modelingCMOS – Electronic modeling 14
  15. 15. Innovation Intelligence® Physical Component Modeling in ScicosPro Application to Vibratory Pile Extraction Study made by Dr. Dirk Reusch (Kybernetics)
  16. 16. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Application Goals A 23m long pile has been inserted 20m into the ground and shall be extracted by means of a static force and a dynamic (harmonic oscillating) force. In order to achieve this, one has to overcome the shaft resistance force of the pile (depends on the relative movement of the shaft with respect to the soil, soil properties, and the pile geometry ). In comparison to purely static extraction the use of a vibrator is advantageous, because the static force needed here is usually significantly smaller. However, this implies the choice of an appropriate vibrator. 16
  17. 17. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Vibratory Piles Pile Properties • Pile Length 23m • Inserted Length 20m • Circumference 3.1m Pile Shaft Resistance (R) • Test data coming from literature Soil Properties • Literature data coming from Cone Penetration Tests 17
  18. 18. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling Motivation • We are first investigating pure static pulling of the pile in order to test our shaft resistance model. This will set the magnitude of the static force needed for extraction. • The pile inserted the ground would be extracted by means of a static force S that can overcome the shaft resistance force R of the pile. Hypothesis • Gravity is not taken into account • Target is moving a fully inserted pile (assumption: force to move a partially inserted pile would be lower) 18
  19. 19. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Pile Shaft Resistance The shaft resistance R of the pile can be split into two parts: a friction force M and a viscous damping force D. Dmax and Mmax are the only parameters 19
  20. 20. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Pile Shaft Resistance Shaft Resistance superblock Parameters Mmax and Dmax z translational mechanical flange Speed sensor to measure z’ Force R=M+D  20
  21. 21. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Pile Shaft Resistance 21
  22. 22. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling We are applying a slowly increasing (quasi-static) pulling force on the pile and measuring the pile movement. We expect that the pile should start moving when this force becomes > Mmax . Models and simulations are performed for both a fully rigid and an elastic pile. 22
  23. 23. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Rigid Pile The pile is modeled here as rigid body with mass mp (via a Mass block). There are two forces acting on the pile: the Pulling Force and the Shaft Resistance • The Pulling Force signal is generated by a ramp block and prescribed as force acting on a mechanical flange via a Force0 block. • The maximum friction force Mmax and the maximum damping force Dmax are provided by two constant blocks. • We are measuring the force f acting on the Pile and its position s. 23
  24. 24. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Rigid Pile Dmax and Mmax parameters Shaft Resistance model Imposed pulling force 4.2MN pile mass force sensor 24
  25. 25. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Rigid Pile Simulation results, i.e. pulling force versus pile movement (upwards direction is negative), are analyzed. As expected, a significant upwards movement of the pile happens when the Pulling Force becomes > Mmax. 25
  26. 26. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Elastic Pile The pile is modeled here as elastic body by using 3 pile elements (3 lumped masses) connected via springs. Element Length Mass Head L/4 mp/4 Center L/2 mp/2 Foot L/4 mp/4 • A different Shaft Resistance is acting on each element. • The right flange of the foot (very lower end of the pile) is connected to a Free block, because we are assuming there is no interaction between pile tip and soil. • The elasticity of the pile is modeled by the two springs in series, where each of them has a spring constant stiffness. The relative movement of each pile element (Head, Center, and Foot) is measured. 26
  27. 27. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Elastic Pile 27
  28. 28. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Static Pulling – Elastic Pile foot center head 28
  29. 29. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling We are replacing the quasi-static, really high, Pulling Force in the previous model by a rather small Static Force and a Dynamic Force, which is physically generated inside a Vibrator of mass md. The Vibrator is rigidly connected (in the real world using hydraulic clamps) to the pile head. The Dynamic Force in the models is prescribed using a Sine block with parameters amplitude=V and freqHz=f The modeling of the rigid and the elastic pile remains the very same as before. Properties of 5 possible vibrators 29
  30. 30. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling – Rigid Pile 30
  31. 31. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling – Rigid Pile Whatever Vibrator we use from the 5 available, with a rigid setup, there is no significant movement of the pile. 31
  32. 32. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling – Elastic Pile 32
  33. 33. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling – Elastic Pile Simulation results, i.e. the movements of the pile head, center, and foot versus time, for each available vibrator, are compared. 2310 VM 24 VM 50 VM Head Center Foot 33
  34. 34. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Dynamic Pulling – Elastic Pile The pile as a whole is not moving significantly using the vibrators 2310 VM and 2319 VM. With the bigger machines 24 VM, 28 VM, and 50 VM the pile as a whole is moving significantly upwards. Why ? A close look reveals, that the 2310 VM and 2319 VM are not powerful enough to make the pile foot oscillating, such that the averaged (over time) friction force becomes small, whereas the others make the pile foot clearly oscillating. All in all, a good (cost-efficient) choice for the pile extraction job seems to be the 24 VM. 34
  35. 35. Copyright © 2014 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Conclusions On the results Vibrator 24 VM seems to be a good choice for the described pile extraction job. If a vibrator is used for pile extraction, then pile elasticity does matter. This result is twofold: • If pile elasticity is present, then it should be taken into account • It is easier to pull an elastic pile than a rigid pile On the approach and tools used With the Coselica library, it was possible to develop geomechanical simulation models easily in ScicosPro, and then test various configurations by changing model parameters. 35

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