Modelling Tools

 

 

Overview

 

For regular structures, a Data Generation wizard will allow the user to specify the structure in terms of few key parameters and automatically generate the model data. For more complex structures structural geometry and loading data may be input through either the graphical data generator ("Sculpt") or a more traditional spreadsheet format

 

Sculpt enables all structural geometry to be rapidly generated and edited on the screen using a cursor controlled by a mouse. Dynamic viewing makes it possible to adjust the model as required

 

When the structure is complete, all loading may be similarly generated and displayed diagrammatically. Structures of complexity varying from simple to large skeletal frame models can be generated and complex 2D element meshes can be generated using the automatic mesh generation facilities

 

The alternative spreadsheet method incorporates many useful features for the generation and copying of numerical data. Text input is normally specified by selection from a list of available items rather than by entering numeric codes

 

The two data generation methods are linked so that they can be used side by side

 

Data input - general

 

• data generation wizard enables standard structures to be generated rapidly by template

• data modules are accessed from the gateway

• data modules are represented in tables

• ... and each data object is represented by its definition wizard

• spreadsheet interaction and COM interface facilities offer convenient generation of data by spreadsheet

• data import options enable CAD and other 3rd party data to be the basis of a GSA model

• automatic mesh generation eases the creation of 2D element meshes

•  

Data input - graphical ('Sculpt ')

 

• sculpt tools allow entities to be added, modified and deleted

• sculpt commands operate on selected entities

• sculpt commands include:

create axes, grid planes, grid lines

modify, move, copy, extrude

add, straighten, flex, transform nodes and round coordinates

collapse nodes and round coordinates

add, split, connect 1D elements

split, refine, spin 2D elements

(similar for geometric entities: lines, areas, regions)

create joints, rigid constraints

create, delete loading

• the sculpt command toolbar gives easy access to the most recently used commands

 

2D mesh generation

 

The mesh domain may be described as follows:

 

• internal and bounding edges may be straight or circular arcs

• internal areas, multiply nested, may be assigned different properties

• holes may be defined

• internal points may be defined

• internal lines may be defined; - the support conditions assigned to lines are automatically assigned to the nodes generated along the lines

• mesh density and mesh concentrations may be specified

 

Modelling

 

Unrestricted capacity

 

Axes:

 

• standard axes: global Cartesian, global cylindrical

• user defined Cartesian, cylindrical and spherical

• definition of local axes for nodes, 2D elements, springs and masses

• axis definition for all load types

 

Element types:

 

• Beams, bars, ties, struts

• Springs, ground springs, non-linear springs

• Masses

• 2D elements

Quad8, Quad4, Tri6, Tri3

Plane stress, Fabric, Flat plate, Shell, Curved shell, Load panel wall

• Props

• Spacers

 

Materials

 

• Elastic Isotropic

• Elastic Orthotropic

• Elastic-plastic Isotropic

• Fabric

 

 

Beam sections may be selected from a steel section database, which includes British, European, US and Australian sections. Other options are to specify the dimensions of a general section (rectangular, circular, I-section, etc) or to specify the properties required for analysis explicitly

 

• steel section database includes the following catalogues:

British

European

US

Australian

Chinese

Indian

Russian

Korean

South African

• standard sections (for which dimensions are specified) include:

rectangular, rectangular hollow

circular, circular hollow

I section, general I section, taper I section

T section, taper T section

channel

angle, taper angle

taper

ellipse

recto-circular, recto-ellipse

secant pile

oval

• geometric section definitions include:

perimeter, for which 2D coordinates are defined for vertices around the section

line segment, for which lines of specified thickness are defined to make up the section

• analysis properties may be defined explicitly

• modification factors may be applied to properties regardless of derivation

• defined via the section wizard

 

Constraints:

 

• Sets of nodes may be constrained to act either identically in specified directions, or to act as a rigid body in specified planes

• Restraints and constraints may act in non-global, user defined directions

generalised restraints

joints

rigid constraints

constraint equations

 

Assemblies

 

Loading

 

Loads may be applied on nodes, on elements or at locations in space. In addition to forces and moment applied to the structure, load types include gravity, pre-stress, thermal and distortion loads. Loads may be applied to a list of appropriate objects or to objects of particular properties.

 

Node loading:

• forces and moments

• applied displacements

• settlements

 

Element loading:

 

• forces and moments: point, uniform, linear, patch, tri-linear

• prestress loads

• thermal loads

• distortion loads

• self-weight

 

Grid loading:

 

• grid point loads

• grid line loads

• grid area loads

• automatically distributed to elements

• Offshore wave loading generator

• Pattern load generator

 

Units

 

GSA allows the user to work in any units. Several standard sets of units are provided to cover most situations; these may be customised if required. Different units can be used in different views on the data and output is annotated accordingly

 

• standard user sets, metric and imperial

• custom unit sets, factored w.r.t SI

• model units assume preferred units, but can be changed

• view units assume model units, but can be changed