Chapter 16: Shell Analysis and Cross Sections
Shell elements are used to create a mathematical 2-D idealization of a 3-D structure. They offer compu-
tationally efficient solutions for modelling shell structures when compared to solid elements.
The discussion in this chapter applies to 3-D finite-strain shell elements such as SHELL181 and SHELL281.
Compared to other shells, these shell elements provide more robust nonlinear analysis capabilities, and
significant improvements in cross-section data definition, analysis, and visualization.
The method for defining shell sections described here can also be used to define the cross-sectional
properties of the layered thermal shell elements SHELL131 and SHELL132. However, information
presented here concerning integration points (NUMPT on the SECDATA command) and section properties
(SECCONTROL command) does not apply to SHELL131 and SHELL132.
The following topics are available for shell analysis and cross sections:
16.1. Understanding Cross Sections
16.2. How to Create Cross Sections
16.3. Using Preintegrated General Shell Sections16.1. Understanding Cross Sections
A cross section defines the geometry of the shell in a plane parallel to the shell x-y plane. Through the
section family of commands, you can describe the z direction of the element by defining consecutive
layers. Each layer may vary in thickness, material type, orientation (from element x-axis), and number
of integration points.
Alternatively, you can define homogeneous shell section behavior directly via preintegrated shell sections,
a method commonly used in analyses involving laminated composite structures. With preintegrated
shell sections, you can directly specify the membrane, bending, and coupling properties. The preinteg-
rated method also allows analysis of complex geometry (with repeated patterns such as corrugated
sheets) using equivalent shell section properties. For more information, see Using Preintegrated General
Shell Sections (p. 465).
16.2. How to Create Cross Sections
The general procedure for creating cross sections consists of the following steps:
- Define the section and associate a section ID number with the section.
- Define the geometry data for the section.
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