Bridge Construction

Objectives Given pictures of bridges, students will be able to identify the basic types of bridges. Without any aid, students will be able to describe the 7 steps of the engineering process with 100% accuracy.

Table of Contents Types of Bridges Engineering Process Quiz References Means Link back to this page here 

Types of Bridges Introduction A bridge is a structure that permits you to cross over an obstacle. Suppose you lay a plank across a brook. You have a bridge. If the plank is thin in relation to its length, it will sag. In fact, if it is too long, it will collapse. This shows that you must consider the weight of a bridge itself---the “dead load”. If you stand at the middle of the plank, it sags even more. So, you must provide for the weight of whatever your bridge is designed to carry---the “live load”. Also, when you walk across the plank, it bounces under you, illustrating the effect of a “moving live load”. Finally, there is a “wind load”. A strong wind pushes against the sides, lifts the deck, shakes the whole structure. Certainly the force of the wind is something to keep in mind. Bridges help us to connect to each other and the world. There are four main types of physical bridges. They are arch, beam, suspension and cable-stayed.

Types of Bridges Beam Bridge A beam or "girder" bridge is the simplest and most inexpensive kind of bridge. In its most basic form, a beam bridge consists of a horizontal beam that is supported at each end by piers-vertical structures at the end of a bridge which support the weight of the bridge. The weight of the beam pushes straight down on the piers. The beam itself must be strong so that it doesn't bend under its own weight and the added weight of crossing traffic. When a load pushes down on the beam, the beam's top edge is pushed together (compression) while the bottom edge is stretched (tension).

Types of Bridges Beam Bridge Basic Beam Bridge Actual Beam Bridge

Types of Bridges Arch Bridge Arch bridges are one of the oldest types of bridges and have great natural strength. Instead of pushing straight down, the weight of an arch bridge is carried outward along the curve of the arch to the supports at each end. These supports, called the abutments, carry the load and keep the ends of the bridge from spreading out.

Actual Arch Bridge Bixby Creek Bridge, Monterey, CA Types of Bridges Arch Bridge Basic Arch Bridge Actual Arch Bridge Bixby Creek Bridge, Monterey, CA

Types of Bridges Suspension Bridge Aesthetic, light, and strong, suspension bridges can span distances from 2,000 to 7,000 feet -- far longer than any other kind of bridge. They also tend to be the most expensive to build. True to its name, a suspension bridge suspends the roadway from huge main cables, which extend from one end of the bridge to the other. These cables rest on top of high towers and are secured at each end by anchorages.

Types of Bridges Suspension Bridge The towers enable the main cables to be draped over long distances. Most of the weight of the bridge is carried by the cables to the anchorages, which are imbedded in either solid rock or massive concrete blocks. Inside the anchorages, the cables are spread over a large area to evenly distribute the load and to prevent the cables from breaking free. What is the difference between an abutment and an anchorage?

Types of Bridges Suspension Bridge Basic Suspension Bridge Actual Suspension Bridge Golden Gate Bridge, San Francisco, CA

Types of Bridges Cable-stayed Bridge Cable-stayed bridges may look similar to suspensions bridges -- both have roadways that hang from cables and both have towers. The two bridges support the load of the roadway in very different ways. The difference lies in how the cables are connected to the towers. In suspension bridges, the cables ride freely across the towers, transmitting the load to the anchorages at either end. In cable-stayeded bridges, the cables are attached to the towers, which alone bear the load.

Types of Bridges Cable-stayed Bridge The cables can be attached to the roadway in a variety of ways. In a radial pattern, cables extend from several points on the road to a single point at the top of the tower. In a parallel pattern, cables are attached at different heights along the tower, running parallel to one other.

Actual Cable-stayed Bridge Types of Bridges Cable-stayed Bridge Basic Cable-stayed Bridge Actual Cable-stayed Bridge Clark Bridge, Alton, IL

Types of Bridges Review To review for the types of bridges, go to http://bridgepros.com/ Click on the Learning Center at the top of the screen. Click on the Build Bridge link. Complete the Bridge game at the bottom of this page.

Engineering Process Intro The engineering process is an extension of the scientific method. Teaching students to use this process when they begin to build their bridges will provide them with valuable skills to use when it comes to solving problems or creating a project. The engineering process includes basic procedures that engineers use to identify the problem and determine an adequate solution to the challenge they have undertaken. The engineering process can be broken down into the following eight simple steps.

Engineering Process Identify the Problem Before the engineer can begin work, the problem or task that is going to be undertaken must be known.

Determine Constraints Engineering Process Determine Constraints Constraints are the limitations that must be considered before you begin designing your bridge. Even though they are not limited to the materials, size, and money, you have to consider them the problem or task.

Engineering Process Analysis of Design During this step, the designs are studied based on their merit in relationship to strength, cost, market appeal, and manufacturability. Models, drawings and calculations can be presented at this stage. A decision should be made at this point on which design to use or rather to begin a new design.

Engineering Process Design Refinement This step begins after a design has been analyzed. Any problems or unresolved considerations with the design should have been made apparent by now. Each design team should attempt to rectify the problems by making improvements in the design. After the corrections have been made, then each team should go back and analyze the design once again.

Engineering Process Implementation Plan Once the final design has been approved, it must be translated from an idea on paper to the real thing. Before the plan can be implemented, plans need to be made outlining the construction process. The methods of construction together with the strategy for scheduling involved a list of the tools; machinery and materials needed to complete the project. A listing of the parts and the dimension of the project are drawn up. The order is which the bridge is to be built is also written down and the specifications are compiled.

Modify the Implementation Engineering Process Modify the Implementation Any obstacles that may arise during the building of the bridge must be analyzed in order to find out if it is a big enough problem to cause a change in the original plan.

Engineering Process Implementation The final step is to manufacture the individual parts as prescribed in the implementation plans. Even though the steps are listed in a specific order, in real life two or more of these steps maybe combined or done in a different order. In the field of engineering, sometimes one person may specialize in a certain step, but the method is always followed in one respect or the other.

The seven steps to the Engineering Process are: Review The seven steps to the Engineering Process are: Identify the Problem Determine Constraints Analysis of Design Design Refinement Implementation Plan Modify the Implementation Implementation

Quiz Question 1: What are the oldest type of Bridges? A. Beam B. Arch C. Cable-stayed D. Suspension Click after you get right answer 

Quiz Question 2: Which type of bridge is normally the longest type? A. Beam B. Arch C. Cable-stayed D. Suspension Click after you get right answer 

Quiz Question 3: Which type of bridge is the cheapest? A. Beam B. Arch C. Cable-stayed D. Suspension Click after you get right answer 

Quiz Question 4: What is the fourth step of the Engineering Process? A. Design Refinement B. Implementation C. Determine Constraints D. Implementation Plan Click after you get right answer 

Quiz Question 5: During this step, the designs are studied based on their merit in relationship to strength, cost, market appeal, and manufacturability. A. Identify Problems B. Modify the Implementation C. Determine Constraints D. Analysis of Design

Go back and move on to next question! Correct! Go back and move on to next question!

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Congratulations, you’ve completed the activity!

References http://bridgepros.com/ http://www.yale.edu/ynhti/curriculum/units/2001/5/01.05.04.x.html#b http://www.mediaworkshop.org/ashs/cole/types.htm