Learning Module: Buckling

Connection design can be difficult to teach, given the detailed nature of the topic and the fundamentally three-dimensional behavior of most connections. However, connections are critically important, and lessons learned in the study of connection design, including load path and identification and evaluation of failure modes, are general and applicable to structural design broadly. IDEA StatiCa uses a rigorous nonlinear analysis model and has an easy-to-use interface with a three-dimensional display of results (e.g., deformed shape, stress, plastic strain) and thus is well suited for the exploration of the behavior of structural steel connections. Building on these strengths, a suite of guided exercises that use IDEA StatiCa as a virtual laboratory to help students learn about concepts in structural steel connection behavior and design was developed. These learning modules were primarily targeted to advanced undergraduate and graduate students but were made suitable for practicing engineers as well. The learning modules were developed by Associate Professor Mark D. Denavit from the University of Tennessee, Knoxville.

Learning Objective

After performing this exercise, the learner should be able to describe how buckling affects the strength of connections and how buckling can be addressed in design using linear buckling analysis.

Background

Successful structural design requires consideration of many physical effects. AISC Specification Section C1 lists 5 major effects that must be considered, including steel yielding, residual stresses, geometric nonlinearity (such as P-δ effects), and initial geometric imperfections.

One way these effects are considered in design is with column curves that relate available compressive strength to effective length. A rudimentary column curve for flexural buckling can be established by considering steel yielding and Euler buckling only.

Basic column curve

The AISC column curve, defined by AISC Specification Equations E3-2 and E3-3, accounts for residual stresses and initial geometric imperfections, both of which reduce the strength in comparison to the basic column curve.