felt

FELT(4fe)                   Finite Element Package                   FELT(4fe)



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).




Version 3.00                        8/4/95                           FELT(4fe)