Introducing Middle School Students to Engineering Principles Using by wuxiangyu


									Introducing Middle School Students to
Engineering Principles Using Educational
Bridge Design Software

MICHAEL D. SYMANS                                                               II. DESCRIPTION OF OUTREACH PROGRAM
Department of Civil and Environmental Engineering
Washington State University                                                  The outreach program was presented by the author and three
                                                                         assistants (two graduate students and one undergraduate student)
                                                                         to the entire eighth grade earth science class of the local public
                           ABSTRACT                                      school system. Each class consisted of approximately 30 students
                                                                         with a total of six classes. Thus, the program reached about 180
In an effort to motivate middle school students to consider future       eighth grade students. The program was presented to all six classes
careers in engineering, an educational outreach program was de-          during one day, each class being 45 minutes in duration. A web site
veloped and implemented during National Engineers Week. The              containing photographs of the program is located at the following
outreach program concentrated on bridge engineering and was              URL:
presented within one day to the entire eighth grade student popu-            The outreach program actually began the day before our visit to
lation of the local public school system. The program began with a       the middle school. In an effort to generate interest among the
presentation on careers in engineering with a particular emphasis        eighth graders in our pending classroom visit, a videotape was pro-
placed on bridge engineering. Fundamental engineering concepts           vided to the eighth grade earth science teacher to show to each of
used in bridge design were then explained. The students used these       her classes the day before our visit. The videotape was obtained
concepts to design a single-span truss bridge using an educational       from Newton’s Apple2 and provided an introduction to engineering
bridge design software program. Finally, a bridge design competi-        and explained how engineers are involved in the design of a wide
tion was held in which the students attempted to optimize the de-        variety of products. The day of our visit began with a presentation
sign of their bridge.                                                    on careers in engineering. The presentation was delivered in a top-
                                                                         down hierarchy starting with the different fields of engineering
                                                                         (e.g., chemical, electrical, mechanical and civil), focusing on the
                       I. INTRODUCTION                                   branches of civil engineering (e.g., environmental, hydraulic, trans-
                                                                         portation, geotechnical and structural), and then concentrating on
    National Engineers Week is held each year in February to pro-        structural engineering with particular emphasis given to bridge en-
mote the field of engineering. One method for promoting engi-            gineering. The intent of the top-down hierarchy was to provide a
neering is to introduce K-12 students to engineering through sim-        context within which to discuss bridge engineering. We wanted
ple hands-on engineering activities. Although many practicing            students to recognize that bridge engineering was but one example
engineers and academicians are interested in promoting engineer-         of the kind of engineering that they could one day be practicing.
ing through such activities, it may require considerable effort to de-       Once we completed our introduction to bridge engineering, we
velop a meaningful outreach program (for example, see the                asked students questions about the videotape they watched prior to
outreach program described in Reference 1). Furthermore, imple-          our visit. Examples of questions that are suitable for the Newton’s
mentation of an outreach program can be time-consuming. As an            Apple2 videotape are: Can a bridge carry more load than it weighs?,
aid to those who are interested in developing K-12 engineering           Can wind damage a bridge?, What types of bridges are there?, Why
outreach programs, this paper describes an outreach program that         would an engineer choose one bridge design over another?. These
was developed to introduce middle school students to general engi-       questions quite naturally led to our discussion on different bridge
neering principles with an emphasis on bridge engineering. The           configurations that engineers use. We explained the primary fea-
outreach program can be implemented within the confines of a typ-        tures of the following types of bridges: beam and girder, truss, arch,
ical one-hour class and thus may be used to reach many students in       suspension, cable-stayed, and floating. We then discussed the dif-
a relatively short period of time.                                       ferent types of loads that act on bridges (e.g., traffic, wind, and
    The primary purposes for implementing the outreach program           earthquake). Next, in preparation for using the bridge design soft-
were: 1) to enhance student interest in science and mathematics by       ware, we discussed some fundamental engineering design princi-
demonstrating a real-world application of these subjects, 2) to pro-     ples for truss bridges. For example, we explained that all truss mem-
vide students with an understanding of the kind of work that struc-      bers are subjected either to tension forces (i.e., forces that pull apart)
tural engineers do, and 3) to plant the “seeds” that cause students to   and compression forces (i.e., forces that push together). Further, we
consider future careers in engineering.                                  explained that if compression members are subjected to too much

July 2000                                                                                             Journal of Engineering Education 273
force, they are likely to buckle while tension members are likely to        ty to real-world engineering design software, the West Point
yield. The concept of buckling was illustrated quite simply by plac-        Bridge Designer is very easy to learn to use and thus is suitable for
ing the end of a yardstick on the floor and applying a compressive          K-12 engineering outreach programs. The grade level of the out-
force to the other end of the yardstick.                                    reach program will govern the amount of assistance that the stu-
    Having illustrated the fundamental engineering concepts that            dents will need for running the program. Our experience with
form the basis for the design of a truss bridge, we introduced the          eighth grade students was that they readily learned to use the pro-
students to an educational bridge design software program entitled          gram and within about 10 minutes of explanation were capable of
West Point Bridge Designer.3 The program is discussed in detail in          independently running an analysis.
the next section along with two example bridge designs that were                The simulated load test involves a realistic, three-dimensional
used to illustrate how the program works. Once we explained how             animation in which a standard highway truck traverses the bridge.
the students could use the program to design their own bridge, we           As the truck traverses the bridge, members that are in compression
held a contest to see which group of students could design the most         turn red while those in tension turn blue. If the bridge can carry the
cost-effective bridge. Within each class, we formed three groups of         load, the truck traverses the bridge safely. Conversely, if the bridge
approximately ten students each. By recording the lowest bridge             is not adequate to carry the load, a simulated bridge collapse occurs.
cost for each student group throughout the day, we were able to             The bridge will not carry the load if the yield strength or buckling
have each student group compete with all other students in the              strength of any of the members is reached. Once a bridge design is
eighth grade. Note that the size of the groups (about 10 students)          completed that can carry the load, the program automatically calcu-
precluded all students from serving as the computer operator.               lates the cost of the bridge. The cost is estimated based on material
However, all students actively participated by cooperating with             cost, connection cost, and product cost. Material costs are based on
each other to make decisions on how to optimize the bridge design.          the cost of the steel members, connection costs are based on the
    After the contest was completed, career guidance brochures4             cost of fabricating connections, and product costs are based on the
were made available to the students. The brochures described ca-            number of different types of members used in the bridge design.
reers in engineering and the courses students should take in high
school to prepare for careers in engineering.
                                                                                           IV. BRIDGE DESIGN EXAMPLES

      III. DESCRIPTION OF EDUCATIONAL BRIDGE                                    As an aid to explaining how the West Point Bridge Designer
                  DESIGN SOFTWARE                                           program works, we prepared two simple example bridge designs.
                                                                            The two example bridge designs began with the same basic bridge
    The bridge design software program used in our engineering              configuration (i.e., a Pratt Through Truss). The examples were cre-
outreach program is entitled West Point Bridge Designer 3 and was           ated by first developing a structural model of the bridge by drawing
downloaded as freeware from the Internet at the following URL:              joints and members within the drawing board mode of the West                    Point Bridge Designer (see figure 1). Next, the material, cross-sec-
Since the program is freeware, it may be copied and distributed             tion shape, and size of each member of the bridge were selected. A
without restriction. The minimum hardware and software require-             three-dimensional view of the bridge can then be displayed as
ments for running the program include a PC with a 486 processor,            shown in figure 2.
8 MB of RAM, 2 MB of hard disk space, and a Microsoft Win-                      The first bridge design example was one in which the bridge is
dowsTM operating system.                                                    under-designed to the extent that the bridge can not even carry its
    As indicated on the West Point Bridge Designer Internet web             own weight. Thus, when the load test is performed, the truck does
page, some of the purposes of the program are as follows: 1) To             not make it onto the bridge before the bridge collapses (see figure 3).
stimulate interest in engineering and design; 2) To provide a legiti-       When we showed this example to the class, we asked for explana-
mate, hands-on engineering design experience based on realistic             tions as to why the bridge collapsed before the truck load was ap-
specifications, constraints, and performance criteria; 3) To demon-         plied. Our goal was to get the students to recognize that, in addi-
strate how computers aid the engineering design process and; 4) To          tion to carrying traffic and environmental loads, a bridge must carry
provide a tool for visualizing structural behavior. Furthermore, the        its own weight.
West Point Bridge Designer Internet web page outlines the follow-               The second example was also an under-designed bridge. How-
ing steps for designing a bridge: 1) Develop a structural model of          ever, in this case the truss was designed to carry its self-weight but
the bridge by drawing joints and members on the computer draw-              not to carry the truck loading (see figure 4). The purpose of this ex-
ing board; 2) Select the material (carbon steel, high-strength steel,       ample was to demonstrate that even though the bridge can be de-
or aluminum), the cross-section shape (solid bar or hollow tube),           signed to support itself, it must, in addition, be designed to carry
and the size (the dimensions of the cross-section) of each member           any applied external loading. This example was used as the initial
of the bridge; 3) Run a simulated load test on the bridge; 4) Repair        design for the student bridge design competition.
any member failures that occur during the load test and; 5) Opti-
mize the bridge design by minimizing its cost.
    It may be noted that the process described above is quite similar                   V. BRIDGE DESIGN COMPETITION
to the process by which a practicing engineer designs a bridge struc-
ture. In fact, the West Point Bridge Designer may be regarded as a             As described above, the second bridge design example in
simplified version of the computer-aided design (CAD) software              which the Pratt Through Truss could not carry the applied truck
that practicing engineers use on a daily basis. In spite of its similari-   loading was used as the initial design for the student bridge design

274    Journal of Engineering Education                                                                                                 July 2000
    Figure 1. Drawing board mode of west point bridge designer.

    Figure 2. Pratt through truss used for bridge design example problems.

competition (see figure 4). The students were instructed to modi-        20 and 21 failed by buckling. Finally, the designer can display a
fy the initial design until the bridge could carry the truck loading.    table that shows a cost summary for the current design (see
As an aid to modifying the bridge design, the West Point Bridge          table 3).
Designer allows the user to display a list of all members in their          The students modified the initial bridge design by selecting dif-
bridge design along with various member properties (see table 1).        ferent members. Although the West Point Bridge Designer soft-
Furthermore, the user can display a table showing the results of         ware allows the user to select the material, cross-section shape and
the load test for the current design (see table 2). Note that the        size of each member, we decided that, due to the limited time avail-
load test results indicate the maximum applied compression and           able for the competition, we would only allow the students to
tension force under the truck loading. Furthermore, the compres-         change the size of the bridge members. Once the bridge could carry
sion and tension capacity of each member is listed. A comparison         the truck loading, the students were to note the total cost of their
of the applied force and member capacity determines whether the          design. Next, the students attempted to optimize their designs by
member fails or not. If the member fails, the status of the member       modifying their bridge until they achieved the lowest cost possible.
is listed as either yielded or buckled. Note in table 2 that members     To provide a meaningful competition, a number of members in the

July 2000                                                                                           Journal of Engineering Education 275
      Figure 3. Failure of bridge design example due to application of self-weight only.

      Figure 4. Failure of bridge design example due to application of truck loading.

initial design were intentionally oversized (see table 2). The lowest        providing a description of an outreach program that is easy to im-
cost bridge that could carry the applied truck loading was consid-           plement using readily available educational bridge design software.
ered to represent the final design.                                          The software is very user-friendly and thus the students are capable
    The cost of the final design for each student group was tabulat-         of learning to use the software within a very short period of time.
ed. The student group with the lowest cost bridge design among all           Thus, meaningful bridge designs can be evaluated very quickly.
of the eighth grade classes received a reward from the teacher. The          Furthermore, the software program offers a level of realism that is
lowest possible cost that the author and his student assistants were         helpful in developing student interest in engineering.
able to achieve with the standard Pratt Through Truss configura-
tion was $2,907.21. The interested reader can download the West
Point Bridge Designer software and try to reduce this cost.                                      ACKNOWLEDGMENTS

                                                                                The outreach program described in this paper was developed in
                           VI. SUMMARY                                       support of the educational component of a Faculty Early Career
                                                                             Development Award that was awarded to the author by the Na-
   It is important to reach out to K-12 students to introduce them           tional Science Foundation under Grant No. CMS-9624227. This
to engineering so that they might consider future careers in engi-           support is gratefully acknowledged. Any opinions, findings, and
neering. This can be achieved through engineering outreach pro-              conclusions or recommendations expressed in this material are
grams such as that described in this paper. Although many profes-            those of the author and do not necessarily reflect the views of the
sional engineers and academicians are interested in promoting                National Science Foundation. Special thanks are given to Mr. Brian
engineering at the K-12 level, there is often a time and effort com-         S. Twitchell (former graduate student), Mr. Glenn J. Madden (for-
mitment that prevents them from getting involved. The outreach               mer graduate student), and Ms. Caroline L. Kunkel (undergraduate
program discussed in this paper attempts to address this issue by            student) who made major contributions to the development of

276     Journal of Engineering Education                                                                                              July 2000
    Table 1. Member list for initial design used in student bridge design competition.

    Table 2. Load test results for initial design used in student bridge design competition.

July 2000                                                                                      Journal of Engineering Education 277
      Table 3. Cost summary for initial design used in student bridge design competition.

the outreach program. Ms. Lynda Oldow (Eighth Grade Earth
Science Teacher at Lincoln Middle School, Pullman, WA) was
kind enough to allow my assistants and me to come to her class-
room to present our engineering outreach program. Her interest
and cooperation is appreciated.


    1. Carroll, D. R., “Bridge Engineering for the Elementary Grades,”
Journal of Engineering Education, vol. 86, no. 3, 1997, pp. 221–226.
    2. Newton’s Apple, “Newton’s Apple Salutes Engineers,” Videotape
Produced by Twin Cities Public Television and 3M for National Engi-
neers Week, Newton’s Apple, St. Paul, MN.
    3. West Point Bridge Designer, Version 3.01, Developed by
Lieutenant Colonel Stephen J. Ressler, Department of Civil and Mechani-
cal Engineering, United States Military Academy, West Point, NY. This
program may be downloaded from the Internet at the following URL:
    4. JETS ( Junior Engineering Technology Society), Brochures entitled
“Engineering and You,” “Engineering is For YOU!” and “Civil Engineer-
ing,” These brochures may be ordered from JETS, Inc., 1420 King St,
Suite 405, Alexandria, VA.

278    Journal of Engineering Education                                                     July 2000

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