Use the following article and diagrams to answer the questions below.

Original Design Concepts:

Before we could begin to meet the given design criteria, we had to conceptualize how the bridges could be tested. Through group brainstorming sessions we came up with the following possible methods:

• Hydraulic Rams
• Pneumatic Rams
• Hydraulic Car Jack
• Mechanical Car Jack
• Mechanical Linkage

Following this brainstorming session, we discussed the advantages and disadvantages of each method., and tried to implement each method into a workable design concept. During this process, we decided to discard the Mechanical Linkage method, because we could not come up with a single feasible way to implement a completely mechanical system to satisfy the given design criteria. All of the concepts we came up with were plagued with complexity and unsure results. We concluded the concept of a purely mechanical system was self defeating, and should be discarded.


Figure 1
Figure I: Implementation of Car Jack
The implementation of the Car Jack, shown in Figure 1 , was felt to be the simplest and cheapest method, but it lacked the versatility of loading needed in the machine. Another problem with this concept was that the jack could provide too much load too quickly, and therefore cause the bridge to fail catastrophically before an accurate measure of the applied load could be made. Also, we felt the Car Jack concept lacked the professionalism the machine needed to project.



Figure 2
Figure 2: Implementation of Pneumatic Rams
The proposed implementation of the Pneumatic Ram method is shown in Figure 2. This design concept had the advantages of being adjustable, clean, and simple. Its main disadvantages would be excessive noise, and potential danger if a failure were to occur in the pneumatic system. Pneumatic equipment is typically noisy, and air compressors are generally loud and vibration prone. In addition, pneumatic devices, such as piston driven rams, tend to hiss and pop off air, again adding noise. Air systems are also known for being dangerous in the event of a rupture in the system.

Figure 3
Figure 3: Implementation of Hydraulic Rams
The design concept for using hydraulic ram, shown in Figure 3, is almost identical to the pneumatic ram concept just discussed. The hydraulic rams would have all of the advantages of the pneumatic rams, but would lack the noise problems, and be safer in the event of a rupture. Also, a smaller size ram could be used with hydraulics then with pneumatics. The disadvantages of this system were the added complexity, cost, and messiness which comes with using oil rather than air.

We submitted these three design concepts on February 12, 1990. On February 14, 1990 we met with Dr. Brinkerhoff to personally discuss the advantages and disadvantages of each design. This meeting resulted in us being asked us to develop a complete design based on the hydraulic ram concept.

After reviewing the material above, please answer the following questions. This assignment will be worth 50 points, and graded on the basis of the 4 Cs.

1. How important to the article are the graphic aids?

2. How well does the writer integrate the graphic aids into the text?

3. What would be the effect if the graphic aids were removed?

4. Could the graphic aids be turned into prose and used in the text without harming the article's quality? Defend your answer.

5. Should the author improve the graphic aids? Which ones? And how?

For grading purposes, please provide the following information:

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E-mail Greg Larkin at Gregory.Larkin@nau.edu
or call (520) 523-4911

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