Weekly Post (week 4)

1. What you did in the prior week
In the future weeks, we are expected to build a real bridge using Knex. The shape of the real bridge would depend on our design on WPBD. It is important to have a nice design on the WPBD, because it would also partly decide the result of competition 2.

I design another bridge on WPBD, which decrease the budget of the bridge to $242215.7. But it is still not low enough, according to reliable news, the lowest budget in our section is around $219000.
The New Design:

2. What you and your teammates have agreed you'll do in the coming week
We are going to continue improving our design. We own several different designs right now. More communication is necessary in the future to combine the advantages of different designs. We will keep finding the construction that cost the less while meeting the constraints. Designing the bridge in class is a nice experience to work with my team mates.

3. Major accomplishments of the week for the team
The bridge that we designed in the class is one of the most important accomplishments for our team in a week.

Some important information is found on Internet:
TIPS FOR WEST POINT BRIDGE DESIGN
Tip #1
According to the contest rules, your design submission will be rejected if it is identical to one already submitted by someone else. So it is in your best interest to submit a design as soon as possible after the contest starts. There's no limit on the number of entries you may submit, so you can keep trying to improve your design -- even after you have submitted it for judging.
Tip #2
To learn how to reduce the cost of your design, start up WPBD 2007 and click the Help menu, then select "How to Design a Bridge…." On the diagram, click the blocks labeled "Optimize the Member Properties," "Optimize the Shape of the Truss," and "Find the Optimum Truss Configuration." Read each of these articles carefully.
Tip #3
It is usually (but not always) most economical to use hollow tubes for compression members and solid bars for tension members. To determine which members are in tension and which are in compression, run the load test. Compression members turn red during the load test animation, and tension members turn blue.
Tip #4
If a member fails the load test, there are three ways to make it stronger:
(1) Increase the member size.
(2) Use a stronger type of steel.
(3) If the member is in compression, make it shorter. (Note: The strength of a tension member is not affected by its length.) You can shorten a compression member by moving joints or by splitting a single member into two.
Tip 5: To minimize the cost of your design, you need to understand how the West Point Bridge Designer calculates the cost of your bridge. The cost consists of four components:
1. Material Cost.
2. Connection Cost.
3. Product Cost.
4. Site Cost.
The Material Cost is simply the cost per kilogram of steel. The stronger the steel, the more it costs per kilogram. Hollow tubes cost more per kilogram than solid bars. The Connection Cost is a fixed cost of $150 for each joint in your structural model. The Product Cost is a $600 charge for each “product” used in your design. A “product” is defined as any unique combination of material, section, and size. For example, the following would be counted as four different products: 120mm x 120mm carbon steel bars, 100mm x 100mm carbon steel bars, 120mm x 120mm carbon steel tubes, and 120mm x 120mm quenched & tempered steel bars. A design that included various numbers of these four products would have a total Product Cost of 4 x $600 = $2400.
To see the cost calculations for your design, click the Report Cost Calculations button on the main toolbar.
Tip #6
To greatly speed up the process of optimizing your design, you can switch off the Load Test Animation. To do this, click the Test menu, then select Load Test Options and uncheck the "Display the Animation" box.
Tip #7
To greatly speed up the process of optimizing your design, use the sorting and "block selection" features of the Member List. To learn more about these features, read the "Member List" topic in the West Point Bridge Designer Help file.
Tip #8
Use the "high-resolution grid" setting to fine-tune the positions of the joints in your structural model. In the high-resolution mode, you can place joints at 0.25 meter intervals, in order to achieve an optimal truss configuration.

HINT: You can sort the Member List by clicking any one of the column headings. For example, clicking the Size heading will sort the list from the largest member size to the smallest. Clicking the same heading a second time will sort the list from smallest to largest.

HINT: hollow tubes are considerably more efficient than solid bars for carrying compression.



4. Issues that the team or you as an individual faces


We are going to accept the challenge that turns the design on paper into real one. Through our design on “paper” is not the optimal design in the sections. The optimal design on paper will also face the problem that it is difficult to turn it into real one.

Individually, I am expecting to turn the design into the real one, at the same time, I am afraid that it would not work.

You've now used the West Point Bridge Designer for several weeks. Address the question of how realistic you think it is (or is not) in terms of what's necessary to design a real bridge. Hint: the program help file has some very good material.

WPBD provides a good tool for engineering entering, but as the same time, it does not simulate many factors that should be considered in realistic.

Figure 2: the main structure of a truss bridge (WPBD 2012 HELP )


1. WPBD does not consider the influence coming from some detail factors such as the abutment, the roadway and the deck and the piers. And many environmental factors should also be considered in the design such as the vapor from the river, ice.
2. The fatigue of the material has not been considered in WPBD.
3. The load has been calculated in WPBD are simple. Multiple loads from different sources, such as self-weight, wind and collision of vehicles, are important in real design.
4. The design of the bridge does not consider some emergency conditions such as earthquake.
5. In the WPBD load test, load is stationary shifting from left to the right. In reality, the traffic appears on both sides of the bridge at the same time. The load should be considered in two directions.
6. The aesthetics of the bridge is not an important criterion in WPBD design. In reality, it is very important and in some way, directly decides if it would be adopted by investor.