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Element property function for beams


il = p_beam('default') 
il = p_beam('database','name') 
il = p_beam('dbval ProId','name');
il = p_beam('dbval -unit TM ProId name');


This help starts by describing the main commands : p_beam Database and Dbval. Supported p_beam subtypes and their formats are then described.

[Database,Dbval] ...

p_beam contains a number of defaults obtained with p_beam('database') or
p_beam('dbval MatId'). You can select a particular entry of the database with using a name matching the database entries. You can also automatically compute the properties of standard beams

circle rbeam with full circular section of radius r.
rectangle b hbeam with full rectangular section of width b and height h. See beam1 for orientation.
Type r1 r2 ...other predefined sections of subtype 3 are listed using p_beam('info').

For example, you will obtain the section property row with ProId 100 associated with a circular cross section of 0.05 m or a rectangular 0.05 × 0.01 m cross section using

 % ProId 100, rectangle 0.05 m by 0.01 m
 pro = p_beam('database 100 rectangle .05 .01')
 % ProId 101 circle radius .05
 il = p_beam(,'dbval 101 circle .05')
 % ProId 103 tube external radius .05 internal .04
 il = p_beam(il,'dbval -unit SI 103 tube .05 .04')
 % Transform to subtype 1
 il(end+1,1:6)=[104 fe_mat('p_beam','SI',1) 0 0 0 1e-5];
 il = fe_mat('convert SITM',il);
 il = p_beam(il,'dbval -unit TM 105 rectangle .05 .01')

Beam format description and subtypes

Element properties are described by the row of an element property matrix or a data structure with an .il field containing this row (see section 7.4). Element property functions such as p_beam support graphical editing of properties and a database of standard properties.

For a tutorial on material/element property handling see section 4.2.1. For a programmers reference on formats used to describe element properties see section 7.4.

1 : standard

  [ProID   type   J I1 I2 A   k1 k2 Lump NSM]
ProIDelement property identification number.
typeidentifier obtained with fe_mat('p_beam','SI',1).
Jtorsional stiffness parameter (often different from polar moment of inertia I1+I2).
I1moment of inertia for bending plane 1 defined by a third node nr or the vector vx vy vz (defined in the beam1 element). For a case with a beam along x and plane 1 the xy plane I1 is equal to Iz = ∫S y2 ds.
I2moment of inertia for bending plane 2 (containing the beam and orthogonal to plane 1.
Asection area.
k1(optional) shear factor for motion in plane 1 (when not 0, a Timoshenko beam element is used). The effective area of shear is given by k1A.
k2(optional) shear factor for direction 2.
lump(optional) request for lumped mass model if set to 1.
NSM(optional) non structural mass (density per unit length).

bar1 elements only use the section area. All other parameters are ignored.

beam1 elements use all parameters. Without correction factors (k1 k2 not given or set to 0), the beam1 element is the standard Bernoulli-Euler 12 DOF element based on linear interpolations for traction and torsion and cubic interpolations for flexion (see Ref. [36] for example). When non zero shear factors are given, the bending properties are based on a Timoshenko beam element with selective reduced integration of the shear stiffness [44]. No correction for rotational inertia of sections is used.

3 : Cross section database

This subtype can be used to refer to standard cross sections defined in database. It is particularly used by nasread when importing NASTRAN PBEAML properties.

  [ProID   type   0  Section Dim(i) ... NSM]
ProIDelement property identification number.
typeidentifier obtained with fe_mat('p_beam','SI',3).
Sectionidentifier of the cross section obtained with comstr('SectionName',-32) where SectionName is a string defining the section (see below).
Dim1 ...dimensions of the cross section.
NSMnon structural mass can be added as a last parameter.

Cross section, if existing, is compatible with NASTRAN PBEAML definition. Equivalent moment of inertia and tensional stiffness are computed at the centroid of the section. Currently available sections are listed with p_beam('info'). In particular one has ROD (1 dim), TUBE (2 dims), T (4 dims), T2 (4 dims), I (6 dims), BAR (2 dims), CHAN1 (4 dims), CHAN2 (4 dims).

See also

Section 4.2.1, section 7.4, fe_mat

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