No Galloping Gerties Allowed!!!, June, 2002



Students are amazed at the idea that a bridge might actually fall down. They think that structures such as bridges are made of concrete and are indestructible. What they don't realize is that all structures must be designed to withstand different forces.

Structures usually have one or more uses: to support a load (an electrical or water tower), to span a gap (a bridge), or to enclose objects or people (buildings or cars). A structure's strength is more important than its appearance. If a structure cannot resist the forces that act on it, it will collapse and be worthless. Both external and internal forces (tension and/or compression, gravity, shear, and/or torsion) act upon a structure. To keep its form, the internal forces of the structure must match the external forces. When designing a strong bridge, engineers must take into consideration factors that may cause the bridge to collapse, such as decades of heavy traffic, environmental pollution, and extremes in climatic conditions.

In this unit the students explore bridges and the various forces that affect their stability. They investigate different kinds of bridges. Finally, they construct a cost-effective bridge under certain constraints.

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These pages were made through TeacherTECH, the teacher professional development component of GirlTECH, which is sponsored by the Center for Excellence and Equity in Education (CEEE) with support from the National Science Foundation through EOT-PACI, RGK Foundation, the Verizon Foundation, Rice University, and HiPerSoft.

Copyright June 2002 by Shirley Willingham