p_beam

Contents Functions

p_beam

Purpose

Element property function for beams

Syntax

il = p_beam('default') 
il = p_beam('database','name') 
il = p_beam('dbval ProId','name');
il = p_beam('dbval -unit TM ProId name');
il = p_beam('dbval -punit TM ProId name');
il2= p_beam('ConvertTo1',il)

Description

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 r	beam with full circular section of radius r.
rectangle b h	beam 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(pro.il,'dbval 101 circle .05')
 p_beam('info')
 % ProId 103 tube external radius .05 internal .04
 il = p_beam(il,'dbval -unit SI 103 tube .05 .04')
 % Transform to subtype 1
 il2=p_beam('ConvertTo1',il)
 il(end+1,1:6)=[104 fe_mat('p_beam','SI',1) 0 0 0 1e-5];
 il = fe_mat('convert SITM',il);
% Generate a property in TM, providing data in SI
 il = p_beam(il,'dbval -unit TM 105 rectangle .05 .01')
% Generate a property in TM providing data in TM
  il = p_beam(il,'dbval -punit TM 105 rectangle 50 10')

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 4.5.1. 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]

ProID	element property identification number.
type	identifier obtained with fe_mat('p_beam','SI',1).
J	torsional stiffness parameter (often different from polar moment of inertia I1+I2).
I1	moment 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.
I2	moment of inertia for bending plane 2 (containing the beam and orthogonal to plane 1.
A	section 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. 1 for inclusion of inertia terms. 2 for simple half mass at node.
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. [37] 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 [45]. 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) ... ]

ProID	element property identification number.
type	identifier obtained with fe_mat('p_beam','SI',3).
Section	identifier 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.

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).

For NSM and Lump support ConverTo1 is used during definition to obtain the equivalent subtype 1 entry.