A1:

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No. The West Point Bridge Designer is intended for educational use only. The loads, structural analysis methodology, and design algorithms used by this software have been simplified considerably from the procedures used to design actual bridges. Using the West Point Bridge Designer to design a real structure would be both dangerous and irresponsible. If you need to design an actual structure, you must obtain the services of a registered professional engineer.

No, not yet. A Java version of WPBD that will run on both Mac and Windows machines is currently in development. We will make this new version available for download as soon as it is completed and tested.

A6:

To understand the answer to this question, you need to understand how WPBD calculates the cost of your truss. Run WPBD and load any of the sample bridge designs. Now click the Report Cost Calculations button, located on the Status toolbar. WPBD will display a table showing exactly how the current cost of the truss has been calculated. You'll see that the total cost is composed of three components--material cost, connection cost, and product cost. When you reduce the size of a member, you reduce its material cost. However, for each new "product" you add to your design, you are charged an additional $500. A "product" is defined as any unique combination of material, cross-section, and size.

This cost algorithm is fairly realistic. If you optimize a structural design by making every member as small as it can possibly be, you'll end up with a very light but very impractical structure. It will be impractical because it will consist of many different member sizes. When a construction company actually has to build a structure like this, the project will incur a lot of additional cost. It's harder and more expensive to join two different sized members together than to connect two identically sized members. There is also a cost associated with having to order and manage many different member sizes on a job site. In short, there can be substantial cost saving associated with standardization--using as many of the same sized members as possible in a structure.

This is not to say that using the same member size for all of the members in a truss will produce an optimal design. It won't! There is a tradeoff between light weight and standardization. You need to do some trial and error to find the best balance between the two. Reducing the size of a single member might cause the total cost of a truss to rise; however, simultaneously reducing the cost of five members will almost certainly cause the total cost to drop, because you reduce the material cost for all five members but add only a single additional $500 product cost.

In the West Point Bridge Designer, your design is judged to be successful if it passes the load test--if the truck is able to drive completely across the span without causing a collapse. Thus, to be successful, your structure must have adequate strength. In evaluating your design, WPBD does not consider how much your bridge bends.

Actual bridge designers do, in fact, consider whether or not the displacements of the structure are too large; however, large displacements are not a safety concern. Displacements are considered in structural design only because excessive movement of a structure tends to make people feel uncomfortable--no matter how strong the structure actually it is.

In any case, your design probably does not bend too much. It only looks that way! In the WPBD Load Test Animation, the displacements are exaggerated by a factor of 10. The purpose of this exaggeration is to illustrate how tension and compression in individual structural members cause the entire structure to bend. If you would like to see how much your bridge would actually bend if it were built, click the View menu in WPBD. Then select "Load Test Display Options..." and uncheck "Show Exaggerated Displacements."

A10:

This problem occurs when your browser fails to download the entire setup file. Because a portion of teh setup file is missing, the installation program can't find all of the files it needs, so it prompts you for Disk 2--even though Disk 2 doesn't exist.

This problem probably occurred because your download was interrupted before it was complete. AOL users appear to be particularly susceptible to this problem. (Of 10-20 reported occurrences, all but one have been AOL users.) These interruptions may have a number of different causes:

• AOL and a number of other Internet service providers automatically configure your Internet connection to "time-out" if the connection is idle for more than a few minutes. If you are not interacting with your computer as the download is occurring (or if you are using a browser other than the one provided by AOL), your ISP may automatically disconnect you before the download is complete.
• If you have "call waiting" on the phone line you are using to access the Internet, an incoming call can cause a disconnection.
• A faulty phone connection (caused by answering machines, bad plugs, old phone lines, etc.) can also cause you to be "bumped" off line.

To fix the problem, all you can do is to continue attempting downloads until you get the complete setup file. A few suggestions:

• Be sure to delete the copy of the setup file you previously tried to download. Leaving it in your download folder could affect subsequent installation attempts.
• When you hit the download link, your web browser will probably ask you if you want to open the file or save it to disk. Be sure to choose the "save" option.
• Try downloading early in the morning or late at night, when your Internet connection is likely to be faster. If you can complete the download more quickly, the chances of a "time-out" or other interruption are less. While you are downloading the file, surf around on our website. Hit a link every 2-3 minutes, so your Internet service provider knows that you're still on line.
• If you are unsuccessful in downloading the setup file, try the three-disk setup. Download all three files to the same folder on your hard disk. Do not download the files directly to 3.5" diskettes. Downloading directly to a floppy disk greatly increases the chances of errors during transmission. You can do the installation by running teh setup file from your hard disk. If you want to have the setup on 3.5" disks, download the files to your hard disk first, then copy them onto three new, freshly formatted disks.

According to the Microsoft Knowledge Base, this problem occurs because some other program on your computer is using the file Msflxgrd.ocx while you are running the WPBD Setup program; or because an anti-virus program is preventing the file from being modified.

To resolve this problem, you need to ensure that no other programs are running on your computer when you run the WPBD setup. Here's how:

1. If your computer uses an anti-virus program, you must disable it before you run the WPBD Setup program. Consult your anti-virus documentation for more information about how to do this.

2. If that does not work, you must restart your computer without starting the program that uses the Msflxgrd.ocx file. To do this, use either of the following methods:

• Hold down SHIFT and restart your computer. This prevents any programs in the StartUp group from starting when you start Windows.
  
  NOTE: If you are prompted to log on to a network, enter your user name and password, click OK, and then hold down SHIFT until you see the Windows desktop. If you do not have to log on to a network, hold down SHIFT when the graphical user interface and the hour glass pointer appear while the computer is restarting.

• If you are using Windows 95/98, start Windows using the Safe Mode as follows:
  (1) Restart the computer. (2) when you see the "Starting Windows" message, hold down F8 (or hold down CTRL if you are using Windows 98). Windows displays a menu. (3) Type the number for the Safe Mode option or use the DOWN ARROW key to select it, and then press ENTER. (4) Rerun the WPBD Setup program.

3. If that does not work, do the following:

• Download the file msflxgrd.ocx (239 KB), and save it in your Windows system folder. (For Windows 95 and 98, this is normally C:\Windows\System. For Windows NT and 2000, it is C:\Winnt\System32. For Windows XP, it is C:\Windows\System32.) If there is already a file named msflxgrd.ocx present in the system folder, first rename it msflxgrdbak.ocx as a backup, then save the downloaded version of the file into the system folder.
  
  
• Click the Windows Start button and select Run. Click the Browse button and navigate to the Windows system folder (where you just saved msflxgrd.ocx). In the dialog box, type the following: regsvr32 msflxgrd.ocx This command will register the system file.