Buckling of Struts-University of Mary Land-Department of Civil and Environmental Engineering

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LECTURE

Third Edition

COLUMNS: BUCKLING (PINNED
ENDS)
• A. J. Clark School of Engineering •Department of Civil and Environmental Engineering

26

by
Dr. Ibrahim A. Assakkaf
SPRING 2003
ENES 220 – Mechanics of Materials
Department of Civil and Environmental Engineering
University of Maryland, College Park

Chapter
10.1 – 10.3

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 1
ENES 220 ©Assakkaf

Introduction
– Buckling is a mode of failure generally
resulting from structural instability due to
compressive action on the structural
member or element involved.
– Examples





Overloaded metal building columns.
Compressive members in bridges.
Roof trusses.
Hull of submarine.

1

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 2
ENES 220 ©Assakkaf

Introduction
– Examples (cont’d)
• Metal skin on aircraft fuselages or wings with
excessive torsional and/or compressive
loading.
• Any thin-walled torque tube.
• The thin web of an I-beam with excessive
shear load
• A thin flange of an I-beam subjected to
excessive compressive bending effects.

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 3
ENES 220 ©Assakkaf

Introduction
– In view of the above-mentioned examples,
it is clear that buckling is a result of
compressive action.
– Overall torsion or shear, as was discussed
earlier, may cause a localized compressive
action that could lead to buckling.
– Examples of buckling for commonly seen
and used tools (components) are provided
in the next few viewgraphs.

2

Slide No. 4

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

ENES 220 ©Assakkaf

Buckling
Introduction
Figure 1

Slide No. 5

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

ENES 220 ©Assakkaf

Introduction
Figure 1 (cont’d)

3

Slide No. 6

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

ENES 220 ©Assakkaf

Introduction
Figure 1 (cont’d)

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 7
ENES 220 ©Assakkaf

Introduction
– In Fig. 1, (a) to (d) are examples of
temporary or elastic buckling.
– While (e) to (h) of the same figure are
examples of plastic buckling
– The distinctive feature of buckling is the
catastrophic and often spectacular nature
of failure.

4

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 8
ENES 220 ©Assakkaf

Introduction
Figure 2. Reinforced Concrete

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 9
ENES 220 ©Assakkaf

Introduction
Figure 3. Steel Beam Buckling

5

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 10
ENES 220 ©Assakkaf

Introduction
– The collapse of a column supporting
stands in a stadium or the roof of a building
usually draws large headlines and cries of
engineering negligence.
– On a lesser scale, the reader can witness
and get a better understanding of buckling
by trying to understand a few of the tests
shown in Fig. 1.

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 11
ENES 220 ©Assakkaf

The Nature of Buckling
– In the previous chapters, we related load to
stress and load to deformation.
– For these non-buckling cases of axial,
torsional, bending, and combined loading,
the stress or deformation was the
significant quantity in failure.
– Buckling of a member is uniquely different
in that the quantity significant in failure is

6

LECTURE 26. Columns: Buckling (pinned ends) (10.1 – 10.3)

Buckling

Slide No. 12
ENES 220 ©Assakkaf

The Nature of Buckling
the buckling load itself.
– The failure (buckling) load bears no unique
relationship to the stress and deformation
at failure.
– Our usual approach of deriving a loadstress and...
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