Building Bridges: Computer Aided Design As A Vehicle For Outreach To High School Students

Abstract

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Session 2525

Building Bridges: Computer-Aided Design as a Vehicle for Outreach to High School Students

Stephen J. Ressler, Kip P. Nygren, Christopher H. Conley United States Military Academy

This paper describes the use of a specially developed computer-aided design (CAD) software package as a vehicle for outreach to high school students. The CAD package was conceived and developed for future use in a nationwide engineering design contest, to be administered as part of the West Point bicentennial commemoration in the year 2002. In preparation for that event, the software has been used successfully in two different high school outreach activities. Student feedback from these activities has validated the concept of a CAD-based outreach project and provided useful suggestions for improvement as well.

Called theWEST POINT BRIDGE DESIGNER, the software guides the user through the design of a truss-type highway bridge, based on a specified design scenario. The program was developed with three principal objectives in mind: • To stimulate interest in engineering and design. • To provide the user with an opportunity to perform a legitimate structural design, based on a realistic set of design specifications and constraints. • To focus attention on West Point’s role as America’s first engineering school and on the contributions made by West Point graduates—past and present—to the design and construction of the nation’s infrastructure.

The design scenario used by the WEST POINT BRIDGE DESIGNER is both realistic and open- ended. The user is asked to design a modern replacement for the Dunlap’s Creek Bridge, the first iron bridge built in the United States1. The structure must be a simply supported truss. The only other constraints on the design are a specified span length, a maximum height restriction, and a minimum clearance over the high-water level of the creek. Within these bounds, the user has complete freedom to define the shape and configuration of the structure. Members of the truss may be individually defined, using any of three different materials (carbon steel, high-strength steel, and aluminum), two different cross-section types (solid bars and hollow tubes), and 40 different member sizes. The design must be capable of carrying its own weight and the weight of a standard AASHTO truck loading2. The design objective is to minimize cost.

The software is written in the Microsoft Visual Basic programming language. It runs on IBM- compatible personal computers with 486 processor or better, running Windows 3.1 or better. The program features a simple graphical user interface, which students are able to learn easily, even if they have little previous experience with computers.

The program’s main window (called the Drawing Board) is shown in Figure 1. To design a bridge, the user simply draws it on the screen with the mouse. Editing of the structure is similarly accomplished by pointing, clicking, and dragging the mouse. Member properties-- material, cross-section geometry, and member sizes—are selected from drop-down lists.

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