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1D Elements

MIDAS PYTHON

Creation Methods

There are three methods available to create 1D elements:

  • Single Element (Main Class) : eg. Truss , Beam
    Creates one element connecting two nodes by their IDs:i and j.
    Use this when we know the specific node IDs to connect.

  • Start and End location (SEmethod) : eg. Truss.SE , Beam.SE
    Creates multiple equally spaced elements between a given start and end location.

  • Start, Direction and Length (SDL method) : eg. Truss.SDL , Beam.SDL
    It creates equally divided elements at Start location along the the direction with given total length.

SS

TRUSS

A nested class within Element used to create truss elements.

Object Attributes

ID: Element ID
TYPE: Element type = 'TRUSS'
MATL: Material ID of the truss element
SECT: Section ID of the truss element
NODE: Nodes of element in list. eg: [1,2]
ANGLE: Beta angle of the truss element
LENGTH : Length of the truss element

To create truss element we have total 3 methods :

1. Truss

Element.Truss(i:int, j:int, mat = 1, sect = 1, angle = 0, group = '' , id = 0)
Creates a truss between nodes i and j.

Parameters

  • i: Node ID of i-th end
  • j: Node ID of j-th end
  • mat (default=1: Material ID of the truss element
  • sect (default=1): Section ID of the truss element
  • angle (default=0): Beta angle of the truss element
  • group (default=''): Structure group of the element and its nodes (can be str or list eg. 'SG' or ['SG1','SG2'])
  • id (default=0): Manually assign an ID. If 0, ID will be auto-assigned.

Examples

Node(0,0,0)    # Create Node at 0,0,0 with ID = 1(default)
Node(1,1,1)    # Create Node at 1,1,1 with ID = 2(default)

beam1 = Element.Truss(1,2)  # Create Truss connecting Node 1 and Node 2 (default ID = 1)

Node.create()
Element.create()

2. Truss.SE

Element.Truss.SE(s_loc: list, e_loc: list, n: int = 1, mat, sect, angle, group, id)
Creates n truss elements between start and end location.

Parameters

  • s_loc: Start location. [x,y,z]
  • e_loc: End location. [x,y,z]
  • n (default=1): Number of elements
  • mat,sect,angle,group,id : Same as Element.Truss() method

Examples

Element.Truss.SE([0,0,0],[10,0,0],10) # Create 10 truss between (0,0,0) and (10,0,0) 

Node.create()
Element.create()

3. Truss.SDL

Element.Truss.SDL(s_loc: list, dir: list, l: float, n: int = 1, mat, sect, angle, group, id)
Creates n truss elements along a straight line defined by direction dir and length l starting at s_loc.

Parameters

  • s_loc: Starting location [x, y, z]
  • dir: Direction vector [dx, dy, dz]
  • l: Total length of element
  • n (default=1): Number of elements
  • mat,sect,angle,group,id : Same as Element.Truss() method

Examples

Element.Truss.SDL([0,0,0],[0,0,1],10) # Create a vertical truss of length 10 at (0,0,0)

Node.create()
Element.create()

BEAM

A nested class within Element used to create Beam elements.

Object Attributes

ID: Element ID
TYPE: Element type = 'BEAM'
MATL: Material ID of the beam element
SECT: Section ID of the beam element
NODE: Nodes of element in list. eg: [1,2]
ANGLE: Beta angle of the beam element
LENGTH : Length of the beam element

To create Beam element we have total 3 methods :

1. Beam

Element.Beam(i:int, j:int, mat = 1, sect = 1, angle = 0, group = '' , id = 0 , bLocalAxis=False)
Creates a Beam between nodes i and j.

Parameters

  • i: Node ID of i-th end
  • j: Node ID of j-th end
  • mat (default=1: Material ID of the Beam element
  • sect (default=1): Section ID of the Beam element
  • angle (default=0): Beta angle of the Beam element
  • group (default=''): Structure group of the element and its nodes(can be str or list eg. 'SG' or ['SG1','SG2'])
  • id (default=0): Manually assign an ID. If 0, ID will be auto-assigned.
  • bLocalAxis (default=False) : Assign the local axis data to nodes

Examples

Node(0,0,0)    # Create Node at 0,0,0 with ID = 1(default)
Node(1,1,1)    # Create Node at 1,1,1 with ID = 2(default)

beam1 = Element.Beam(1,2)  # Create Beam connecting Node 1 and Node 2 (default ID = 1)

Node.create()
Element.create()

2. Beam.SE

Element.Beam.SE(s_loc: list, e_loc: list, n: int = 1, mat, sect, angle, group, id, bLocalAxis)
Creates n Beam elements between start and end location.

Parameters

  • s_loc: Start location. [x,y,z]
  • e_loc: End location. [x,y,z]
  • n (default=1): Number of elements
  • mat,sect,angle,group,id,bLocalAxis : Same as Element.Beam() method

Examples

Element.Beam.SE([0,0,0],[10,0,0],10) # Create 10 Beam between (0,0,0) and (10,0,0) 

Node.create()
Element.create()

3. Beam.SDL

Element.Beam.SDL(s_loc: list, dir: list, l: float, n: int = 1, mat, sect, angle, group, id, bLocalAxis)
Creates n Beam elements along a straight line defined by direction dir and length l starting at s_loc.

Parameters

  • s_loc: Starting location [x, y, z]
  • dir: Direction vector [dx, dy, dz]
  • l: Total length of element
  • n (default=1): Number of elements
  • mat,sect,angle,group,id,bLocalAxis : Same as Element.Beam() method

Examples

Element.Beam.SDL([0,0,0],[0,0,1],10) # Create a vertical beam of length 10 at (0,0,0)

Node.create()
Element.create()

4. Beam.PLine

Element.Beam.PLine(points_loc: list, n_div:int=0,deg:int=1,includePoint:bool=True, mat, sect, angle, group, id, bLocalAxis=False,div_axis="L")
Creates equal n_div Beam elements passing through curve defined by points_loc.
It allows dividing a curve into equal-length segments while providing an option to include the original input points (even if they don’t coincide with the division points).

NODE GRID

Parameters

  • points_loc: List of control points defining the curve. [[x1, y1, z1],[x2, y2, z2],...]
  • n_div: No. of beam elements to be generated. If n_div = 0 , no interpolation will be considered.
  • deg: Degree of interpolation curve.
         1 : Linear   |   2 : Quadratic   |   3 : Cubic
  • includePoint: Whether to include original input points in the final curve.
         • True: Original points always appear in the mesh.   |   • False: Only equal subdivisions are used.
  • mat,sect,angle,group,id,bLocalAxis : Same as Element.Beam() method
  • div_axis: Method of division
         1 : "L" - Equal length   |   2 : "X" - Equal division along X   |   2 : "Y" - Equal division along Y   |   3 : "Z" - Equal division along Z

Examples

pts = [[0,0,0],[10,0,0],[20,5,0],[40,-10,0],[50,0,0],[60,0,0]]
Element.Beam.PLine(pts,100,1,True)

Node.create()
Element.create()

5. Beam.PLine2

Element.Beam.PLine(points_loc: list, n_div:int=0,deg:int=1,includePoint:bool=True, mat, sect, angle, group, id, bLocalAxis=False,div_axis="L",yEcc:list[float]=0,zEcc:list[float]=0,bAngleInEcc:bool=True)
Creates equal n_div Beam elements passing through curve defined by points_loc.
It allows dividing a curve into equal-length segments while providing an option to include the original input points (even if they don’t coincide with the division points).

Additional options are provided to offset the curve in local-y and local-z direction.

Angle , yEcc , zEcc can take float or list(float)
Eg. yEcc = [0,10,0] -> Offset at start = 0   |   Offset at mid = 10   |   Offset at end = 0
Inbetween values are interpolated based on MAKIMA 1D interpolation.

NODE GRID

Parameters

  • points_loc: List of control points defining the curve. [[x1, y1, z1],[x2, y2, z2],...]
  • n_div: No. of beam elements to be generated. If n_div = 0 , no interpolation will be considered.
  • deg: Degree of interpolation curve.
         1 : Linear   |   2 : Quadratic   |   3 : Cubic
  • includePoint: Whether to include original input points in the final curve.
         • True: Original points always appear in the mesh.   |   • False: Only equal subdivisions are used.
  • mat,sect,angle,group,id,bLocalAxis,div_axis : Same as Element.Beam() method
  • yEcc : Offset along Local-Y direction
  • zEcc : Offset along Local-Z direction
  • bAngleInEcc (boolean): Whether to consider beta angle for the offset calculation

Examples

NODE GRID

ptA = [[0,0,0],[5,0,0],[10,0,0]]
ptB = [[0,5,0],[5,5,0],[10,5,0]]

Element.Beam.PLine2(ptA,100,2,False,angle=[0,90],yEcc=0,bAngleInEcc=False)
Element.Beam.PLine2(ptA,100,2,False,angle=[0,90],yEcc=2,bAngleInEcc=False)

Element.Beam.PLine2(ptB,100,2,False,angle=[0,90],yEcc=0,bAngleInEcc=True)
Element.Beam.PLine2(ptB,100,2,False,angle=[0,90],yEcc=2,bAngleInEcc=True)

Node.create()
Element.create()

TENSION

A nested class within Element used to create tension-only elements, hooks, and cables.

Object Attributes

ID: Element ID
TYPE: Element type = 'COMPTR'
MATL: Material ID of the tension element
SECT: Section ID of the tension element
NODE: Nodes of element in list. eg: [1,2]
ANGLE: Beta angle of the tension element
LENGTH : Length of the tension element
STYPE: Subtype of tension element (1=Tension-only, 2=Hook, 3=Cable)
TENS: Allowable compression or initial tension force
T_LIMIT: Tension limit value
T_bLMT: Tension limit flag (automatically set when T_LIMIT is provided)
NON_LEN: Non-linear length parameter (for Gap subtype)

Tension Element

Element.Tension(i:int, j:int, stype:int, mat = 1, sect = 1, angle = 0, group = '' , id = 0, non_len = None, cable_type = None, tens = None, t_limit = None)
Creates a tension element between nodes i and j.

Parameters

  • i: Node ID of i-th end
  • j: Node ID of j-th end
  • stype: Tension element subtype (1=Tension-only, 2=Hook, 3=Cable)
  • mat (default=1): Material ID of the tension element
  • sect (default=1): Section ID of the tension element
  • angle (default=0): Beta angle of the tension element
  • group (default=''): Structure group of the element and its nodes (can be str or list eg. 'SG' or ['SG1','SG2'])
  • id (default=0): Manually assign an ID. If 0, ID will be auto-assigned.
  • non_len (default=None): Non-linear length parameter for Hook/Cable
  • cable_type (default=None): Cable type for stype=3 (1=Pretension, 2=Horizontal, 3=Lu)
  • tens (default=None): Initial tension force or allowable compression
  • t_limit (default=None): Tension limit value

Examples

Node(0,0,0)    # Create Node at 0,0,0 with ID = 1(default)
Node(1,1,1)    # Create Node at 1,1,1 with ID = 2(default)

# Simple tension-only member
tension1 = Element.Tension(1,2,stype=1)

# Tension-only with allowable compression and tension limit
tension2 = Element.Tension(1,2,stype=1,tens=0.5,t_limit=-15)

# Hook element with slack length
hook1 = Element.Tension(3,4,stype=2,non_len=0.5)

# Cable with initial tension and catenary effects
cable1 = Element.Tension(5,6,stype=3,cable_type=3,tens=1000.0,non_len=0.1)

Node.create()
Element.create()

Subtypes

1. Tension-only (stype=1)

  • Transfers tension forces only
  • Can have allowable compression (tens parameter)
  • Can have tension limit (t_limit parameter)

2. Hook (stype=2)

  • Has slack length defined by non_len parameter
  • Only active when stretched beyond slack length

3. Cable (stype=3)

  • Supports catenary analysis
  • Requires cable_type parameter
  • Can have initial tension and slack length

COMPRESSION

A nested class within Element used to create compression-only elements and gaps.

Object Attributes

ID: Element ID
TYPE: Element type = 'COMPTR'
MATL: Material ID of the compression element
SECT: Section ID of the compression element
NODE: Nodes of element in list. eg: [1,2]
ANGLE: Beta angle of the compression element LENGTH : Length of the compression element
STYPE: Subtype of compression element (1=Compression-only, 2=Gap)
TENS: Allowable tension or initial compression force
T_LIMIT: Compression limit value
T_bLMT: Compression limit flag (automatically set when T_LIMIT is provided)
NON_LEN: Non-linear length parameter (for Gap subtype)

Compression Element

Element.Compression(i:int, j:int, stype:int, mat = 1, sect = 1, angle = 0, group = '' , id = 0, tens = None, t_limit = None, non_len = None)
Creates a compression element between nodes i and j.

Parameters

  • i: Node ID of i-th end
  • j: Node ID of j-th end
  • stype: Compression element subtype (1=Compression-only, 2=Gap)
  • mat (default=1): Material ID of the compression element
  • sect (default=1): Section ID of the compression element
  • angle (default=0): Beta angle of the compression element
  • group (default=''): Structure group of the element and its nodes (can be str or list eg. 'SG' or ['SG1','SG2'])
  • id (default=0): Manually assign an ID. If 0, ID will be auto-assigned.
  • tens (default=None): Allowable tension or initial compression force
  • t_limit (default=None): Compression limit value
  • non_len (default=None): Non-linear length parameter for gap

Examples

Node(0,0,0)    # Create Node at 0,0,0 with ID = 1(default)
Node(1,1,1)    # Create Node at 1,1,1 with ID = 2(default)

# Simple compression-only member
comp1 = Element.Compression(1,2,stype=1)

# Compression-only with tension limit and buckling limit
comp2 = Element.Compression(1,2,stype=1,tens=27,t_limit=-15)

# Gap element with initial gap
gap1 = Element.Compression(3,4,stype=2,non_len=0.25)

Node.create()
Element.create()

Subtypes

1. Compression-only (stype=1)

  • Transfers compression forces only
  • Can have allowable tension (tens parameter)
  • Can have compression limit (t_limit parameter)

2. Gap (stype=2)

  • Has initial gap defined by non_len parameter
  • Only active when compressed beyond gap length

Examples

1. Portal Frame

h = 3.5        # Height of each storey
w = 4.0       # Width of each Bay

n_storey = 10 # Total no. of storey
n_bay = 5      # Total no. of bay

for i in range(n_bay+1):
    for j in range(n_storey):
        if i!=n_bay:
            Element.Beam.SDL([i*w,0,j*h],[0,0,1],h,sect=1)  # Column -> Sect ID = 1
            Element.Beam.SDL([i*w,0,(j+1)*h],[1,0,0],w,sect=5) # Beam -> Sect ID = 5
        else:
            Element.Beam.SDL([i*w,0,j*h],[0,0,1],h,sect=1) # Column -> Sect ID = 1

Node.create()
Element.create()
NODE GRID

2. Warren Truss

span = 20.5  # Span of truss
n_div = 8    # No. of bottom divisions
h = 2.5      # Height of truss

dx = 0.5*span/n_div

Element.Truss.SDL([0,0,0],[1,0,0],span,n_div)

Element.Truss.SDL([dx,0,h],[1,0,0],span-2*dx,n_div-1)

for i in range(n_div):
    Element.Truss(i+1,i+2+n_div)
    Element.Truss(i+2,i+2+n_div)

Node.create()
Element.create()
NODE GRID