The animation is a graphical simulation of your bridge undergoing the load test. To initiate the animation, click the .
As the animation begins, your bridge is subjected to its own weight--the weight of the steel structural elements, the , and the . Once the self-weight is applied, the moves across the bridge from left to right. As the are applied, the bridge bends downward. The of the bridge are exaggerated by a factor of 10, to illustrate how truss shorten and elongate as they carry load. As the member increase, the members change color--red for and blue for . The more intense the color, the closer the member is to failure. If one or more members are found to be , the animation includes a depiction of these members failing and the resulting collapse of the bridge.
You can pause, rewind, and restart the animation at any time, using the
You can change the appearance of the load test animation or opt not to show it at all by changing the .
Whenever a member is found to be unsafe, the load test animation depicts the failure of that member, in either the or failure mode. This depiction is not entirely realistic. Engineers always build a substantial margin of into the design of structural members. This margin of safety is represented by the in code-specified load combinations and by the resistance factors in the equations for tensile strength and compressive strength. An unsafe member might fail, or it might continue to carry load with a reduced margin of safety.
In an actual bridge, it is possible for one or more members to fail without causing the total collapse of the structure. However, if any member is found to be unsafe, the West Point Bridge Designer 2010 considers the design to be unsuccessful.