Provided by: felt_3.06-9_i386 bug

NAME

       felt - finite element problem description file format

DESCRIPTION

       The felt(4fe) file format is used by the programs of the finite element
       package, felt(1fe), velvet(1fe), and burlap(1fe) to describe  a  finite
       element  problem.   The  file  is  human  readable  and  consists  of a
       friendly, intuitive syntax rather than a table of  numbers.   Syntactic
       and  semantic errors are detected and reported assuring that only valid
       problem descriptions are used.  In general white space is  unimportant,
       arbitrary  numeric  expressions  may  be  used, and case of keywords is
       unimportant.  As per  standard  convention,  boldface  items  represent
       keywords,  italicized  items  represent  the syntax of the grammar, and
       items in brackets are optional.  The file syntax is shown below.

              [ problem-description ]
              [ analysis-parameters ]
              [ object-definitions ]
              [ appearance-description ]
              end

   Problem description
       The problem-description section specifies the  problem  title  and  the
       number  of  nodes  and elements in the problem.  If this section is not
       specified then the problem will be unnamed and is  assumed  to  contain
       zero  nodes  and zero elements.  This section may be absent for example
       in defaults files which define objects but do  not  specify  an  actual
       problem instance.  The format for a problem-description is given below.

              problem description
              [ title = string ]
              [ nodes = integer ]
              [ elements = integer ]
              [ analysis =  static  |  transient  |  modal  |  static-thermal|
              transient-thermal| spectral ]

       If  the  title  is  missing  then  the problem is unnamed.  If nodes or
       elements is missing then none of that type of object are expected.  The
       assignments  can  occur  in any order and can even be repeated with the
       last assignment being used.

   Analysis parameters
       The analysis-parameters section defines any parameters for  a  specific
       type of analysis.  Currently, this section is used only if the analysis
       mode is transient.  The format of the  analysis-parameters  section  is
       given below.

              analysis parameters
              [ alpha = expression ]
              [ beta = expression ]
              [ gamma = expression ]
              [ step = expression ]
              [ start = expression ]
              [ stop = expression ]
              [ Rm = expression ]
              [ Rk = expression ]
              [ nodes = [ node-list ] ]
              [ dofs = [ dof-list ] ]
              [ mass-mode = lumped | consistent ]

       The  alpha, beta, andgamma parameters are used in numerical integration
       schemes (transient and transient-thermal analysis).  start,  stop,  and
       step  define  the  range of time or frequency interest for transient or
       spectral analyses.  In transient analyses,  start  is  meaningless  and
       duration and dt can be used as aliases for stop and step, respectively.
       Rk  and  Rm  are  global  Rayleigh   (stiffness   and   mass)   damping
       proportionality  constants.   The  node-list  is a comma or white space
       separated list of node numbers that are of interest  in  the  analysis.
       Similarly,  the  dof-list  is a list of the degrees of freedom (Tx, Ty,
       Tz, Rx, Ry, and Rz) that are of interest.

       An object-definition section  defines  objects  of  a  specified  type.
       Objects  include  nodes,  elements, materials, constraints, forces, and
       distributed loads.  Each of these types of objects is discussed  below.
       Multiple  object-definition  sections  are allowed and the sections may
       occur in any order.

   Nodes
       Nodes are points in cartesian space to which elements are attached.   A
       node  must have a constraint and may have an optional force.  A node is
       identified by a natural number.  The syntax is as follows:

              nodes
              node-definitions

       where a node-definition takes the following form:

              node-number
              [ x = expression ]
              [ y = expression ]
              [ z = expression ]
              [ constraint = constraint-name ]
              [ force = force-name ]
              [ mass = expression ]

       The node-number starts the definition.  Each node must  have  a  unique
       number.   If a cartesian coordinate is not given then the coordinate of
       the previous node is used.  Similarly, if no constraint is  given  then
       the  constraint  applied  to  the previous node is used.  As above, the
       assignments can appear in any  order  and  any  number  of  times.   As
       indicated  above, some objects are identified by their name and some by
       their number.  Elements and nodes have numbers while materials, forces,
       loads, and constraints have names.

   Elements
       Elements  are  linear,  planar,  or solid objects which are attached to
       nodes.  Each element must have a material and may have optional  loads.
       Furthermore,  each  element  has  a  type,  or definition.  Like nodes,
       elements are identified  by  a  unique  natural  number.   Elements  of
       specific type are defined with the following syntax:

              element-type elements
              element-definition

       where an element-type is one of the following:

              spring
              truss
              beam
              beam3d
              CSTPlaneStrain
              CSTPlaneStress
              iso2d_PlaneStrain
              iso2d_PlaneStress
              quad_PlaneStrain
              quad_PlaneStress
              timoshenko
              htk
              brick
              ctg
              rod

       and an element-definition has the following form:

              element-number
              nodes = [ node-list ]
              [ material = material-name ]
              [ load = load-name-list ]

       The  element-number  starts  the  definition.  Each element must have a
       unique number.  If no material is given then the  material  applied  to
       the  previous  element  is used.  The load-name-list is a list of up to
       three loads to apply to the element.  The node-list is a comma or white
       space  separated list of node numbers.  Each type of element requires a
       certain of nodes and in some cases  a  special  "null  node"  which  is
       numbered zero may be used to indicate a gap or filler in the list.

   Materials
       Elements  are made of a type of material.  Each material has a name and
       certain physical properties not all of which may be  used  by  any  one
       element.  The syntax for defining materials is as follows:

              material properties
              material-definitions

       where material-definition has the following form:

              material-name
              [ color = string ]       # color for velvet
              [ E = expression ]       # Young’s modulus
              [ Ix = expression ]      # moment of inertia about x-x axis
              [ Iy = expression ]      # moment of inertia about y-y axis
              [ Iz = expression ]      # moment of inertia about z-z axis
              [ A = expression ]       # cross-sectional area
              [ J = expression ]       # polar moment of inertia
              [ G = expression ]       # bulk (shear) modulus
              [ t = expression ]       # thickness
              [ rho = expression ]     # density
              [ nu = expression ]      # Poisson’s ratio
              [ kappa = expression ]   # shear force correction
              [ Rk = expression ]      # Rayleigh damping coefficient (K)
              [ Rm = expression ]      # Rayleigh damping coefficient (M)
              [ Kx = expression ]      # thermal conductivity in the x-direction
              [ Ky = expression ]      # thermal conductivity in the y-direction
              [ Ky = expression ]      # thermal conductivity in the z-direction
              [ c = expression ]       # heat capacitance

       The material-name starts the definition.  If an attribute of a material
       is not specified then that attribute  is  zero.   The  assignments  may
       occur  in  any  order.  The color specifies the color to use in drawing
       the material within velvet, and is ignored by other applications.

   Constraints
       Constraints are applied to nodes to indicate about which  axes  a  node
       can move.  The syntax for defining a constraint is as follows:

              constraints
              constraint-definitions

       where constraint-definition has the following form:

              constraint-name
              [ color = string ]              # color for velvet
              [ tx = c | u | expression ]     # boundary translation along x axis
              [ ty = c | u | expression ]     # boundary translation along y axis
              [ tz = c | u | expression ]     # boundary translation along z axis
              [ rx = c | u | expression | h ] # boundary rotation about x axis
              [ ry = c | u | expression | h ] # boundary rotation about y axis
              [ rz = c | u | expression | h ] # boundary rotation about z axis
              [ itx = expression ]            # initial displacement along x axis
              [ ity = expression ]            # initial displacement along y axis
              [ itz = expression ]            # initial displacement along z axis
              [ irx = expression ]            # initial rotation about x axis
              [ iry = expression ]            # initial rotation about y axis
              [ irz = expression ]            # initial rotation about z axis
              [ vx = expression ]             # initial velocity along x axis
              [ vy = expression ]             # initial velocity along y axis
              [ vz = expression ]             # initial velocity along z axis
              [ ax = expression ]             # initial accel. along x axis
              [ ay = expression ]             # initial accel. along y axis
              [ az = expression ]             # initial accel. along z axis

       The constraint-name starts the definition.  A value of c for a boundary
       condition indicates  that  the  axis  is  constrained;  a  value  of  u
       indicates  that  the  axis is unconstrained.  An expression indicates a
       displacement (non-zero)  boundary  condition  and  may  contain  the  t
       variable  for  time  varying  boundary conditions in transient analysis
       problems.   The  initial   dislacement,   velocity   and   acceleration
       specifications are only used in transient problems.  A value of h for a
       rotational boundary condition indicates a hinge.  By default, all  axes
       are unconstrained.  The color specifies the color to use in drawing the
       constraint within velvet, and is ignored by other applications.

   Forces
       Forces, or point loads, may be applied to  nodes.   The  syntax  for  a
       force definition is as follows:

              forces
              force-definitions

       where a force-definition has the following form:

              force-name
              [ color = string ]       # color for velvet
              [ Fx = expression ]      # force along x axis
              [ Fy = expression ]      # force along y axis
              [ Fz = expression ]      # force along z axis
              [ Mx = expression ]      # moment about x axis
              [ My = expression ]      # moment about y axis
              [ Mz = expression ]      # moment about z axis
              [ Sfx = expression ]     #  frequency-domain  spectra  of  force
                                       along x axis
              [ Sfy = expression ]     #  frequency-domain  spectra  of  force
                                       along y axis
              [ Sfz = expression ]     #  frequency-domain  spectra  of  force
                                       along z axis
              [ Smx = expression ]     # frequency-domain  spectra  of  moment
                                       about x axis
              [ Smy = expression ]     #  frequency-domain  spectra  of moment
                                       about y axis
              [ Smz = expression ]     # frequency-domain  spectra  of  moment
                                       about z axis

       The  force-name  starts  the definition.  If the force or moment is not
       specified then it is assumed to be zero.  The  expressions  for  forces
       may  be  time-varying.   Time-varying  expressions  include  the single
       variable t to represent the current time in the solution of  a  dynamic
       problem  or  consist  of  a  list  of  discrete  (time,  value)  pairs.
       Frequency varying expressions for spectra can also use w  to  represent
       the  independent  variable (radial frequency).  The color specifies the
       color to use in drawing the force within  velvet,  and  is  ignored  by
       other applications.

   Loads
       Distributed  loads,  or  loads for short, are applied to elements.  The
       syntax for a defining a distributed load is as follows:

              distributed loads
              load-definitions

       where a load-definition has the following form:

              load-name
              [ color = string ]       # color for velvet
              [ direction = dir ]      # direction
              [ values = pair-list ]   # local nodes and magnitudes

       The load-name starts the definition.  The dir is one of LocalX, LocalY,
       LocalZ  (local  coordinate  system),  GlobalX, GlobalY, GlobalZ (global
       coordinate system), parallel, or perpendicular.   The  pair-list  is  a
       sequence  of pairs.  A pair is a node number and an expression enclosed
       in parentheses.  The node number refers  to  the  position  within  the
       element  rather  than referring to an actual node.  The color specifies
       the color to use in drawing the load within velvet, and is  ignored  by
       other applications.

   Appearance Description
       The  appearance-description  section  is used by velvet to describe the
       appearance of a problem.  This section is currently not used  by  felt.
       The  appearance  includes  the  state  of the drawing area and any tool
       figures.   This  section  consists  of  two  subsections,  the  canvas-
       configuration   section  and  the  figure-list  section.   The  canvas-
       configuration section has the following syntax.

              canvas configuration
              canvas-parameters

       where a canvas-parameter has the following form:

              [ node-numbers = boolean ]         # node numbering
              [ element-numbers = boolean ]      # element numbering
              [ snap = boolean ]                 # snap grid status
              [ grid = boolean ]                 # visible grid status
              [ snap-size = expression ]         # snap grid size
              [ grid-size = expression ]         # visible grid size
              [ node-color = color-name ]        # node color
              [ element-color = color-name ]     # element color
              [ label-font = font-name ]         # labeling font
              [ tool-color = color-name ]        # tool figure color
              [ tool-font = font-name ]          # text figure font
              [ x-min = expression ]             # x-axis minimum
              [ x-max = expression ]             # x-axis maximum
              [ y-min = expression ]             # y-axis minimum
              [ y-max = expression ]             # y-axis maximum
              [ x-pos = expression ]             # x position of drawing area
              [ y-pos = expression ]             # y position of drawing area
              [ width = expression ]             # width of viewport window
              [ height = expression ]            # height of viewport window
              [ scale = expression ]             # scale of drawing area

       A boolean is either true or false.  A color-name is the name of a valid
       X11  color.   Similarly,  a  font-name is the name of a valid X11 font.
       The last five parameters are probably not very meaningful to the  user.
       The figure-list section has the following syntax.

              figure list
              figure-definitions

       where a figure-definition has the following form:

              figure-type
              [ x = expression ]            # x coordinate
              [ y = expression ]            # y coordinate
              [ width = expression ]        # width
              [ height = expression ]       # height
              [ start = expression ]        # starting angle
              [ length = expression ]       # arc length
              [ text = name ]               # text string
              [ color = name ]              # color
              [ font = name ]               # text font
              [ points = [ point-list ] ]   # line points

       The  figure-type  starts  the  definition  and  is  one  of  rectangle,
       polyline, text, or arc.  Note that not all properties have meaning  for
       all  figures.   Any  unneeded  property is ignored.  If a color or font
       property is not given then the previous property is used.   The  point-
       list is a list of (x-coordinate, y-coordinate) pairs.

   Expressions
       An  expression  can  be  either constant or time-varying.  As discussed
       above, time-varying expressions contain the variable t or consist of  a
       list  of discrete (time, value) pairs.  If a time-varying expression is
       given where a  constant  expression  is  expected,  the  expression  is
       evaluated  at time zero.  An expression has one of the following forms,
       where all operators have the precedences and associativities  given  to
       them in the C programming language.

              expression ? expression : expression # in-line conditional
              expression || expression             # logical or
              expression && expression             # logical and
              expression | expression              # integer inclusive or
              expression ^ expression              # integer exclusive or
              expression & expression              # integer and
              expression == expression             # equality
              expression != expression             # inequality
              expression < expression              # less than
              expression > expression              # greater than
              expression <= expression             # less than or equal
              expression >= expression             # greater than or equal
              expression << expression             # integer shift left
              expression >> expression             # integer shift right
              expression + expression              # addition
              expression - expression              # subtraction
              expression * expression              # multiplication
              expression / expression              # division
              expression % expression              # integer remainder
              - expression                         # arithmetic negation
              ! expression                         # logical negation
              ~ expression                         # integer bitwise negation
              ( expression )                       # enforce precedence
              sin ( expression )                   # sine
              cos ( expression )                   # cosine
              tan ( expression )                   # tangent
              pow ( expression , expression )      # power (exponentiation)
              exp ( expression )                   # exponential
              log ( expression )                   # natural logarithm
              log10 ( expression )                 # base-10 logarithm
              sqrt ( expression )                  # square root
              hypot ( expression , expression )    # Euclidean distance
              floor ( expression )                 # floor
              ceil ( expression )                  # ceiling
              fmod ( expression , expression )     # floating point remainder
              fabs ( expression )                  # absolute value
              number                               # literal value
              t                                    # current time

       Finally, a discretely valued expression has the following syntax, where
       the optional + indicates that the  list  represents  one  cycle  of  an
       infinite waveform.

              ( expression,expression ) ... [ + ]

AUTHOR

       The  felt  file format was developed by Jason I. Gobat (jgobat@mit.edu)
       and Darren C. Atkinson (atkinson@ucsd.edu).

SEE ALSO

       corduroy(1fe), felt(1fe), velvet(1fe), xfelt(1fe), corduroy(4fe).