2.5.12. Axisymmetric Loads and Reactions
For constraints, surface loads, body loads, and Y-direction accelerations, you define loads exactly as
they would be for any nonaxisymmetric model. However, for concentrated forces the procedure is a
little different. For these quantities, input load values of force, moment, etc. are on a "360° basis." That
is, the load value is entered in terms of total load around the circumference. For example, if an axisym-
metric axial load of 1500 pounds per inch of circumference were applied to a 10” diameter pipe (Fig-
ure 2.17: Concentrated Axisymmetric Loads (p. 49)), the total load of 47,124 lb. (15002 π5 = 47,124)
would be applied to node N as follows:
F,N,FY,-47124Axisymmetric results are interpreted in the same fashion as their corresponding input loads. That is,
reaction forces, moments, etc. are reported on a total load (360°) basis.
Axisymmetric harmonic elements require that their loads be supplied in a form that the program can
interpret as a Fourier series. The MODE command (Main Menu> Preprocessor> Loads> Load Step
Opts> Other> For Harmonic Ele or Main Menu> Solution> Load Step Opts> Other> For Harmonic
Ele), together with other load commands (D,F,SF, etc.), is required for these elements. See the Command
Reference for details.
Figure 2.17: Concentrated Axisymmetric Loads
Defined on a 360° basis2.5.12.1. Hints and Restrictions
Specify a sufficient number of constraints to prevent unwanted rigid-body motions, discontinuities, or
singularities. For example, for an axisymmetric model of a solid structure such as a solid bar, a lack of
UX constraint along the axis of symmetry can potentially allow spurious "voids" to form in a structural
analysis. (See Figure 2.18: Central Constraint for Solid Axisymmetric Structure (p. 50).)
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationApplying Loads