Mechanical APDL Structural Analysis Guide

The following input example uses the CBMX command to define a (temperature-independent) paramet-
erized cross-section stiffness matrix for a circular solid cross section with unit radius:

Exx = 30e6

Nuxy = 0.3

Gxy = 0.5*Exx / (1+Nuxy)

Radius = 1

Pi = 3.14

Xarea = Pi * Radius**2

Izz = Pi/4 * Radius**4

Iyy = Pi/4 * Radius**4

J = Izz + Iyy

sectype,1,comb,matrix

cbmx,1, Exx*Xarea

cbmx,2, Exx*Iyy

cbmx,3, Exx*Izz

cbmx,4, Gxy*J

cbmx,5, Gxy*Xarea

cbmx,6, Gxy*Xarea

cbmx,7, 0

15.5.2. Considerations for Using Composite Beam Sections

You can define preintegrated composite beam sections when using element BEAM188 or BEAM189
elements. The following conditions apply:

• The section data defined by each command listed in Table 15.3: Commands for Specifying Preintegrated
  Composite Beam Section Data (p. 447) is associated with the section most recently defined (SECTYPE).


• Beam stresses are not available for output; however, the stress resultants are available as ETABLE quant-
  ities.


• Section offsetting (SECOFFSET) is not available.


• The preintegrated stiffness components must yield a positive definite section stiffness at analysis time.


• Only the temperature of the beam axis is relevant.

15.5.3. Example: Composite Beam Section Input.

The following input example compares the results of a preintegrated composite beam section to an
offset channel section:

/prep7

/com, Approximate material properties of steel in U.S. customary units

Exx = 30e6

nuxy = 0.3

gxy = 0.5*Exx / (1+nuxy)

/com, Parameterize length and number of elements to more easily study

/com, the effects of discretization and length-to-thickness ratio

leng = 25

nelem = 1

mp,ex,1,Exx

mp,prxy,1,nuxy

mp,gxy,1,gxy

et,1,188,1,,3! Include warping and use the cubic shape function

offy = -8

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Beam Analysis and Cross Sections