Critical Thinking in Engineering Process Bridges and Bridge Design.

Critical Thinking

in Engineering Process

Bridges and Bridge Design

beam bridgesuspension bridgearch bridge

• The major difference between the three types of bridges is the distance that they can cover in a single span. Span is the difference between two supports. Each of the different types of bridges holds weight in different ways.

• A beam bridge is basically a rigid horizontal structure that rest on two supports, one located at each end of the bridge as shown in Figure (a). A simple beam bridge is flat across and supported by two ends.

• When the load pushes down on the beam the top edge is pushed together or compressed, while the bottom of the beam is stretched or is under tension.

• The beam must be strong enough so that it doesn't bend under its own weight and the added weight of the traffic crossing it.

• An arch bridge is composed of a curved structure with abutments on each end.

• The weight of the load is carried outward along the curve of the arch to the abutments at each end of the arch. The abutments also keep the end of the bridge from spreading outward.

• The arch bridge is always under compression because the weight of the deck is pushed outward along the curve of the arch towards the abutments. The rise in the form of the curved arch causes the vertical load to have a horizontal thrust.

• The suspension bridge literally suspends the roadbed from huge cables, which extends from one end of the bridge to the other. The cables are attached to two tall towers and are secured at each end by anchorages.

• The cable carries the weight on a suspended bridge to the anchorages that are imbedded in solid rock or massive concrete blocks. The cables are spread over a large area in order to evenly distribute the load inside the anchorages to prevent the cables from breaking free.

• The anchorages help to stabilise the bridge. Therefore, the tower must be embedded to earth firmly. In such a way, the cables transfer the forces to the towers which carry the forces directly into the earth where they are firmly imbedded.

Explanation:•The students will research and design their own bridge using the Internet. After their research of bridges is complete they will come up with their own design and construction of a bridge. Students are to use the pre-cut pieces of wood, glue, and base. Overall dimensional constrains will be given at a later time. Duration for this project is 6 weeks.•Student Requirements•- Internet Research •- Select materials•- Create a design•- Determine size•- Create a full scale set of plans with dimensions•- Determine and learn required tools and machines to create your stool.•- Build your bridge •Total Points Possible•Complete custom stool    100 Pts.

Explanation:•Students will write a short term paper about their process in creating their bridge. This paper is dived into three areas. Section 1 is about student research and design, material selection, advantages and disadvantages of materials, and cost of materials. Section 2 is about the actual bridge building making process in the lab, tool, machines, and safety. The final part is a summary of the whole process and the completion of a shop stool. •Student Requirements•- Students research established stools an Internet•- Students research material selection•- Students explain why they selected their materials•- Students write first draft of term paper•- Students revise term paper•- Students hand in final draft of term paper (3 pages). •Total Points Possible •Shop Stool term paper        100 Pts.

Explanation:•Students will test their bridge for maximum strength, durability, and materials cost efficiency, which means that the most points will be awarded to the bridge that holds the most weight with the least structural damage and least materials.•Student Requirements •To have created a high quality bridge that will have the most weight.•Total Points Possible •Total   100 Pts.