BEAM23 Element Description

BEAM23 is a uniaxial element with tension-compression and bending capabilities. The element has three degrees of freedom at each node: translations in the nodal x and y direction and rotation about the nodal z-axis. See BEAM23 in the Theory Reference for ANSYS and ANSYS Workbench for more details about this element.

The element has plastic, creep, and swelling capabilities. If these effects are not needed, BEAM3, the 2-D elastic beam, may be used. See BEAM54 for a 2-D tapered elastic beam.

BEAM23 Input Data

The geometry, node locations, and the coordinate system for this element are shown in Figure 23.1: "BEAM23 Geometry". Any one of four cross-sections may be selected with the appropriate value of KEYOPT(6). The element is defined by two nodes, the cross-sectional area, moment of inertia, the height for rectangular beams, the outer diameter (OD), and the wall thickness (TKWALL), for thin walled pipes, the outer diameter for solid circular bars, and the isotropic material properties.

The general cross-section option (KEYOPT(6) = 4) allows inputting a section height and a five-location area distribution. If the section is symmetric, only the first three of the five areas need be input since the fourth area defaults to the second and the fifth area defaults to the first. The areas input should be a weighted distribution at the -50% integration point A(-50), the -30% integration point A(-30), the 0% integration point A(0), the 30% integration point A(30), and the 50% integration point A(50). Each area A(i) is as shown in Figure 23.2: "BEAM23 Weighting Functions for General Section (KEYOPT(6) = 4)". The height is defined as the distance between the ± 50% integration points, and is not necessarily the distance between the outermost fibers of the section. Determination of the input areas is accomplished as follows. Estimate one of the input areas by the formula A(i) = L(i) x HEIGHT, where L(i) is the width of the section at integration point i (see Figure 23.2: "BEAM23 Weighting Functions for General Section (KEYOPT(6) = 4)". Substitute this area along with the section moment of inertia, I_zz, and total area, A, into the above equations and solve them simultaneously for the remaining two input areas. A(0) is usually the easiest to estimate; for instance, as a first guess A(0) for an I-beam would be the web thickness times the height. A trial and error procedure (by modifying the estimated input area) may be needed if the calculated input areas are inconsistent, such as a negative area. The input areas, A(i), are related to the true areas, A_t(i), corresponding to each integration point, by:

A_t (-50) = 0.0625 A(-50), A _t (50) = 0.0625 A(50),

A_t(-30) = 0.28935 A(-30), A_t (30) = 0.28935 A(30),

A _t (0) = 0.29630 A(0)

Shear deflection may be controlled with the KEYOPT(2) value. The shear deflection constant (SHEARZ) is input only for the general cross-section. See Shear Deflection for details. The shear modulus (GXY) is used only with shear deflection.

Element loads are described in Node and Element Loads. Pressures may be input as surface loads on the element faces as shown by the circled numbers on Figure 23.1: "BEAM23 Geometry". Positive normal pressures act into the element. Lateral pressures are input as a force per unit length. End "pressures" are input as a force. KEYOPT(10) allows tapered lateral pressures to be offset from the nodes. Temperatures and fluences may be input as element body loads at the four "corner" locations shown in Figure 23.1: "BEAM23 Geometry". The first corner temperature T1 defaults to TUNIF. If all other temperatures are unspecified, they default to T1. If only T1 and T2 are input, T3 defaults to T2 and T4 defaults to T1. For any other input pattern, unspecified temperatures default to TUNIF. Similar defaults occurs for fluence except that zero is used instead of TUNIF.

A summary of the element input is given in "BEAM23 Input Summary". Element Input gives a general description of element input.

BEAM23 Output Data

The solution output associated with the element is in two forms:

Several items are illustrated in Figure 23.2: "BEAM23 Weighting Functions for General Section (KEYOPT(6) = 4)".

The printout contains the stresses and strains at nine locations in the beam. The locations are at three points through the height of the element (bottom, middle, and top) at each of three axial stations (end I, midlength, and end J) (see Figure 23.3: "BEAM23 Printout Locations"). The post data items [ETABLE] contain the stresses and strains at the five weighted-area locations (regardless of the KEYOPT(6) setting) at each of the three axial stations. Solution Output gives a general description of solution output. See the Basic Analysis Guide for ways to view results.

The Element Output Definitions table uses the following notation:

A colon (:) in the Name column indicates the item can be accessed by the Component Name method [ETABLE, ESOL]. The O column indicates the availability of the items in the file Jobname.OUT. The R column indicates the availability of the items in the results file.

In either the O or R columns, Y indicates that the item is always available, a number refers to a table footnote that describes when the item is conditionally available, and a - indicates that the item is not available.

The following tables list output available through the ETABLE command using the Sequence Number method. See The General Postprocessor (POST1) of the Basic Analysis Guide and The Item and Sequence Number Table of this manual for more information. The following notation is used in Table 23.3: "BEAM23 Item and Sequence Numbers (Node I)" through Table 23.5: "BEAM23 Item and Sequence Numbers (Node J)":

BEAM23 Assumptions and Restrictions

BEAM23 Product Restrictions

There are no product-specific restrictions for this element.