1505 1130 1215 introduction plaxis

CG1 Chile May 15-18, 2006: Introduction to Plaxis 1

PLAXIS FINITE ELEMENT CODE FOR SOIL AND ROCK ANALYSES

Introduction to Plaxis

Dennis WatermanPlaxis BV


General modelling aspects

Defining a project:• Define geometry• Generate mesh• Define initial conditions• Define calculation phases• Calculate• Inspect results




The geometry is the representation of the physical problem

• Consists of points, lines and clusters• Definition of soil layers, structural elements

and loads



Points• Start and end of lines. • Positioning of anchors• Point forces, • Point fixities • Local refinements of the finite element mesh.




Lines• Define the physical boundaries of the

geometry• Define discontinuities in the geometry:

• Sheet pile walls, distributed loads• Separations of distinct soil layers or construction

stages.• A line can have several functions or

properties



Clusters• Automatically generated enclosed areas• Homogeneous soil properties.



(a) 6-noded triangle (b) 15-noded triangle

stress points

nodes


Mesh• 6-noded or 15-noded triangular elements• Displacements calculate in nodes• Stresses calculated in Gaussian integration

points


Input program



Input

• Composing a geometry model• Creating and assigning data sets• Generating a finite element mesh• Generating initial conditions


Composing a geometry model

• Graphical input of geometry contour, soil-layers, construction stages, plates, geogrids, interfaces, anchors

• Designer for circular or non-circular tunnels

• Input of loads and boundary conditions



• Geometry lines (between soil layers, etc.)

• Plates (Walls, Plates & Shells)

• Hinges (free rotation between beams)

• Geogrids

• Interface elements (soil-structure interaction)

• Anchors (node-to-node, fixed end)


Creating and assigning material data sets

• Enter model parameters as data sets in a material data base

• Assigning data sets to geometry components by means of ‘drag and drop’



Generating a finite element mesh

• Fully automatic mesh generation based on geometry model

• Global and local refinement options


Generating initial conditions

• Generating initial pore pressures by means of phreatic line or groundwater flow calculation

• Flip switch - gives: Initial stresses and geometry mode

• Setting initial geometry configuration• Generating initial stresses (K0 procedure)



Calculation program


Defining calculation phases

• Plastic calculation, Consolidation, Phi/c reduction and Dynamic analysis.

• Updated mesh.• Loading input: Multipliers or Staged

Construction.• Changing water conditions• Multiple calculation phases can be pre-defined

and executed at once.



Output program


View results

• Graphical and tabulated output of displacements, stresses and structural forces

• Output in cross sections• Multiple output windows can be opened

simultaneously (comparison of results)



First Exercise

Resume of input steps


Input geometry

Draw geometry



Input boundary conditions

Default fixities


Input loads

Point force A & B



Input material properties

General properties, model parameters


Mesh generation

Full automatic mesh generator



Initial conditions

Water pressures, Initial stresses


See course manual

1505 1130 1215 introduction plaxis

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