A NEW APPROACH TO TEACHING AND LEARNING
STRUCTURAL ANALYSIS
S. Kitipornchai, H. F. Lam
Department of Building and Construction, City University of Hong Kong, Hong Kong SAR, China
T. Reichl
Mursoft OEG, Grafenbergstrasse 47c/13, A-8051 Graz, Austria
Keywords: Structural analysis, Computer software, Virtual experiment.
Abstract: After the 9/11 incident, many structural educators became aware of the importance of inculcating in their
students a clear understanding of local and global structural behaviour to develop basic knowledge about the
progressive collapse of structures. The authors of this paper have addressed the issue by training students
through ‘virtual’ experiments in a self-learning environment with the help of a newly developed software
application, iSA (Instant Structural Analysis). One of the outstanding features of this application is that it
allows students to instantly observe the changes in structural behaviour that are induced by changes in
loading conditions, structural geometry, support conditions and member properties. This paper not only
discusses the need to modify traditional teaching methods in the education of the new generation of
structural engineers, but also presents some of the features of iSA that serve as handy tools in the teaching
and learning of structural analysis.
1 INTRODUCTION
Since the catastrophic collapse of the World Trade
Centre (WTC) towers on September 11, 2001, it has
become more apparent that understanding the
progressive failure or collapse of structural systems
is of paramount importance. Many educators and
researchers have realised the importance of this,
developing different types of educational packages.
Al-Ansari & Senouci (1999) and Codeno-Rosete
(2007) decided to employ commercial software such
as Microsoft Excel, Mathcad and Scilab
(http://www.scilab.org) in developing education
packages to facilitate the teaching of structural
analysis and design. With the help of rapidly
developing information technology, many
researchers have developed applications related to
structural education that can be accessed through the
Internet. Yuan and Teng (2002), Jiang et al. (2002),
and Brretto et al. (2003) have applied client-side
technologies such as HTML, Java and Flash in
developing web-applications for students to carry
out simple structural analysis or structural
laboratories by using web-browsers without having
to install the application in their local computers.
One of the most outstanding advantages of this type
of client-side technology is that students can always
gain access to the latest version of the software from
the website. Elgamal et al. (2005) made use of both
client-side and server-side technologies in
developing the Webshaker system, which allows
students to remotely control a shaking table in the
laboratory through a web-browser. Common to the
abovementioned packages is their ability to enable
students to easily test structures under various
support conditions, material and cross-sectional
properties, and loading conditions.
A new approach to teaching structural analysis
and design is the use of instant structural analysis
software (Beer & Pilz, 1999) that is capable of
stimulating rapid experimental learning as well as
capable of being used as a creative design tool.
An easy-to-use instant structural analysis
software application with full graphical user
interface (GUI) has been developed for 2D
structures – iSA (Instant Structural Analysis). iSA
serves as a handy tool for teachers and engineers
alike to learn about structural analysis and design. It
379
Kitipornchai S., Lam H. and Reichl T. (2009).
A NEW APPROACH TO TEACHING AND LEARNING STRUCTURAL ANALYSIS.
In Proceedings of the First International Conference on Computer Supported Education, pages 379-383
DOI: 10.5220/0001865403790383
Copyright
c
 SciTePress

gives instant graphical results that accurately
simulate structural responses, thus promoting self-
learning and creativity. This paper introduces several
features of iSA and their importance in enhancing
student learning and the understanding of structural
analysis.
2 ISA (INSTANT STRUCTURAL
ANALYSIS) AND ITS BASIC
FEATURES
iSA (http://www.bc.cityu.edu.hk/isa) is a user-
friendly, yet powerful, 2D structural analysis
package that supports modelling with a ‘drawing’
GUI or the use of template wizards (so-called
‘structure generators’) to generate structurally
complicated models in minutes. Because its purpose
is to provide an environment for students to simulate
different structures under various loading conditions,
iSA is easy-to-learn and easy-to-operate. In general,
it takes only a few minutes for students to finish the
computer model of a structure in iSA. According to
the experience of the authors, it takes only two hours
for Year 2 undergraduate structural engineering
students (with knowledge of the matrix stiffness
method) to evolve from beginners to experts in the
use of this software.
iSA can be used for the analysis of trusses,
continuous beams and frames with different types of
pinned joints. Comprehensive databases of materials
and standard sections are available. This feature is
very important for students using iSA in learning
structural design, as they can easily ‘try’ different
sections on the structure and instantly obtain a new
set of analysis results to determine whether the
design is feasible. Apart from standard sections,
users can define their own material and cross-
sections. Analysis is automatically completed once
the structural system and the loading conditions are
defined, and the analysis results can be instantly
presented to the user. After changes to the structural
geometry, support condition, member properties,
etc., the new analysis results can again be instantly
presented. This ability to provide instant results
makes it very suitable for carrying out ‘virtual
testing’ (Kayvani, 2007). For example, students can
remove some members, apply several hinges or
change the boundary condition of the structural
system to simulate the situation of a terrorist attack,
and then observe the effects on the structure (e.g.,
what is the change in load distribution? What is the
change in deformation? Is the structure still stable
under the second-order analysis?). This kind of
‘virtual testing’ is very efficient in helping students
to develop their structural engineering sense and to
understand the concept of progressive collapse.
Furthermore, iSA supports not only first-order
but also second-order static analysis, dynamic modal
analysis, stability analysis and moving load analysis.
It is not only a versatile tool for the teaching and
learning of the subject, but is also a handy tool for
practising engineers in structural analysis and
design.
2.1 Material and Cross-sectional
Properties
iSA provides a GUI that allows users to modify the
material and cross-sectional properties easily (see
Figure 1).
Figure 1: GUI for modifying the material and cross-
sectional properties of members.
A series of commonly used materials, such as
steel, concrete and aluminium are available in the
system’s material database (see Figure 2). A
comprehensive database of cross-sections is also
available for different standards, such as universal
beams and columns. iSA supports both prismatic
and non-prismatic members. By clicking the ‘<>’
button (see Figure 1), users can define a different
section as the ‘end cross section’. iSA assumes that
the inverse of the second moment of area varies
linearly along the member.
CSEDU 2009 - International Conference on Computer Supported Education
380

Figure 2: GUI for selecting a material from the database.
2.2 Support Conditions
iSA’s GUI allows users to modify the support
conditions easily. In the ‘Constrained DOFs’ area
shown in Figure 3, users can define the support as a
pin, a roller or a built-in support at any angle from
the horizontal. They are also allowed to use springs
to model the semi-rigid behaviour of the support.
Figure 3: GUI for defining the support condition.
3 ADVANCED FEATURES
In addition to basic first-order static analysis, other
types of analyses are available in iSA, such as
second-order analysis, dynamic modal analysis,
stability analysis and moving load analysis. Owing
to the limited space, only some of these are
introduced in the following sections.
3.1 Dynamic Modal Analysis
Once the structure is defined in iSA, the system
stiffness and mass matrices are automatically
generated. When users press the dynamic modal
analysis button (at the toolbar), iSA solves the
eigenvalue problem of the system stiffness and mass
matrices and calculates the natural frequencies and
mode shapes of the structure.
Figure 4: GUI showing the third mode of vibration of a
simple frame structure.
The first mode natural frequency and mode
shape is then instantly displayed in the drawing area
on top of the original structure. Users can easily
display the shapes of other modes through the GUI.
Figure 4 shows a GUI that displays the third
vibration mode of a steel frame. An animation of the
mode shape is also available for students to gain a
physical sense of the modes of a structural system.
Figure 5: The bending moment diagram for one of the
automatically generated moving load case.
3.2 Moving Load Analysis
Moving load analysis provides a fast and convenient
feature for users to easily study the effect of a
moving load on the structural system. After defining
the movable load and the member on which the load
is moving, a series of load cases are automatically
generated under a pre-defined load case group.
Figure 5 shows the bending moment diagram of the
structure. In addition to the bending moment
diagram, the shear force and axial force diagrams,
together with their envelopes, are also available.
When the structural geometry, the member
A NEW APPROACH TO TEACHING AND LEARNING STRUCTURAL ANALYSIS
381

properties or the support conditions are changed, all
of the analysis results are updated automatically, and
the results are instantly presented through the GUI.
3.3 Teaching Progressive Collapse
The concept of progressive collapse can be
introduced to students by using iSA with suitable
guidance. A simple steel portal frame, as shown in
Figure 6, is employed to illustrate this idea.
Figure 6: A portal frame to demonstrate the idea of
progressive collapse.
Under the action of both the vertical and the
horizontal distributed loads (as shown in Figure 6), it
is clear from the results that the maximum bending
moment is 81.88 kNm at the top right corner of the
frame (see Figure 7).
Figure 7: The maximum bending moment at the top right
corner of the frame.
For demonstration purposes, 81.88 kNm is
assumed to be the maximum plastic moment. Thus,
a plastic hinge is formed at the top right corner of
the frame. This plastic hinge can be easily modelled
in iSA by first adding a full hinge at the joint and
then applying appropriate moments at the ends of
the members that connect the hinge. In this example,
a full hinge is added to the joint at the top right
corner of the frame. Then, member end moments of
magnitude of 81.88 kNm and -81.88 kNm are
applied at the ends of the two members that connect
the full hinge, as shown in Figure 8. Note that the
bending moment diagrams in Figure 7 and Figure 8
are the same, but there is a plastic hinge on the
structure in Figure 8.
Users can now continue to increase the applied
load on the frame. To demonstrate, only the vertical
distributed load is increased. Figure 9 shows a
situation in which the vertical load is increased to 6
kN/m. It is clear from the iSA result that the
maximum bending moment of the structural system
is on the top left member of the portal frame.
Figure 8: A plastic hinge is modelled at the top right
corner of the portal frame.
Figure 9: The applied load is further increased after the
formation of the plastic hinge.
Figure 10: Additional nodes are added to locate the
maximum bending moment on the top left member of the
frame.
CSEDU 2009 - International Conference on Computer Supported Education
382

Figure 11: The additional plastic hinge makes the structure
unstable, and it collapses.
To determine that location approximately,
additional nodes are added on the member, as shown
in Figure 10. It must be pointed out that there are
many ways to identify the location and magnitude of
the maximum bending moment (or axial force or
shear force) on a member, and the introduction of
additional nodes is only one of them. It is assumed
that a plastic hinge is formed at the location of the
maximum moment. When the user applies a full
hinge at that location, iSA immediately shows that
the structure is kinematically unstable, as shown in
Figure 11. By repeating this exercise with suitable
guidance from the teaching staff, students will be
able to build up a sense of progressive collapse of
structural systems.
4 CONCLUSIONS
The notion of having an adequate ‘safety factor’ in
itself is not enough. Indeed, it could even give us a
false sense of security. We need to emphasise to our
students the importance of understanding physical,
holistic structural behaviour such as the equilibrium
of whole structures, the effects of compatibility, the
effects of a lack of fit, etc. We need to equip our
students with the fundamental and essential skills
they need to be able to check and verify computer-
generated results manually. We need to adopt easy-
to-use structural analysis software that can provide
and stimulate rapid experimental learning through
the investigation of ‘what if?’ scenarios, that can be
used to check computer-generated results to reflect
on ‘whether it really makes physical sense’, and that
can also be used as a creative design tool. We need
to revise our curricula to phase out or reduce the use
of old-fashioned manual calculation techniques and,
instead, increase our emphasis on practical aspects
and on a physical/holistic understanding of structural
behaviour.
To prevent a catastrophic collapse, such as that
which occurred on 9/11, we need to understand how
a structure will behave and respond under all
possible loadings, including that from a terrorist
attack. Therefore, we should design every structure
so that:
1. It will not fail catastrophically if a part or parts
of the structure are damaged or destroyed;
2. It will be able to re-distribute the load when
parts of the structure have failed; and
3. It will have a high degree of redundancy and be
able to provide alternative load paths to avoid
sudden collapse.
iSA, a user-friendly 2D structural analysis
program with an easy-to-use GUI, has been
described here. This software is a handy tool for
instructor teaching and student learning in structural
analysis (e.g., the matrix stiffness method, second-
order analysis, dynamic modal analysis, plastic
analysis, stability analysis, moving load analysis,
etc.). As the analysis results are presented instantly,
this is an efficient and rapid self-learning tool with
which students can build up their confidence,
engineering sense and understanding of structural
behaviour.
REFERENCES
Al-Ansari, M.S. and Senouci, A.B., 1999. Use of Mathcad
as a Teaching and Learning Tool for Reinforced
Concrete Design of Footings. Computer Applications
in Engineering Education 7, 146-154.
Beer, G. and Pilz, G., 1999. Civil Engineering Technology
– Experiences with using the Techware Ruckzuck in a
Structural Analysis Course, Thomas Telford, UK.
Brretto, S.F.A., Piazzalunga, R. and Ribeiro, V.G., 2003.
A Web-Based 2D Structural Analysis Education
Software. Computer Applications in Engineering
Education 11, 83-92.
Cedeno-Rosete, R., 2007. Stiffness Matrix Structural
Analysis Educational Package by Mathcad. Computer
Applications in Engineering Education 15, 107-113.
Elgamal, A., Fraser, M. and Zonta, D., 2005. Webshaker:
Live Internet Shake-Table Experiment for Education
and Research. Computer Applications in Engineering
Education 13, 99-110.
Jiang, H., Kurama, Y.C. and Fanella, D.A., 2002. WWW-
Based Virtual Laboratories for Reinforced Concrete
Education. Computer Applications in Engineering
Education 10, 167-181.
Kayvani, K., 2007. Are We Winning the Battle of
Computerised Structural Modelling? Structural
Engineering International 1/2007, Editorial, 3.
Yuan, X.F. and Teng, J.G., 2002. Interactive Web-Based
Package for Computer-Aided Learning of Structural
Behaviour. Computer Applications in Engineering
Education 10, 121-136.
A NEW APPROACH TO TEACHING AND LEARNING STRUCTURAL ANALYSIS
383