Your bridge cannot be load tested because it is unstable. To make it stable, you should modify the configuration of your truss such that it is composed entirely of interconnected triangles. Usually this requires the addition of more members.
\nFor an explanation of instability and how to correct it, see the examples below.
\nClick the Close button to return to the Drawing Board.
\n explanationTextPane.contentType=text/html titleLabel.text=Your structural model is unstable. examplePanel.TabConstraints.tabTitle=Example 1 examplePanel.TabConstraints.tabTitleMore=Example %d #NOI18N cartoonLabel.icon=ex1pt1.gif nextButton.text=Next >> backButton.text=<< Back tipTextPane.text=\n | If you're having trouble creating a stable truss,\ntry using a template. On the main menu, click File, then Load Template. The template will show you where \nto place joints and members to ensure that your truss is stable. |
\ (1) This truss is unstable, because the highlighted panel is rectangular, rather than triangular.\
ex1pt2.text=\ (2) The rectangular panel is not rigid, so it cannot carry any load. There is nothing to prevent the entire truss from rotating about its supports, as shown here. It is unstable.\
ex1pt3.text=\ (3) To fix the problem, add a diagonal member to divide the rectangular panel into triangles. Now the truss is rigid and can carry load. It is stable.\
ex2pt1.text=\ (1) This truss is also unstable. When only two members are connected to a joint and those two members lie along a straight line...\
ex2pt2.text=\ (2) There is nothing to prevent the center joint from moving perpendicular to the two members, as shown here. The center joint can carry no load. It is unstable.\
ex2pt3.text=\ (3) To fix the problem, add a third member to the unstable joint, or...\
ex2pt4.text=\ (4) Delete the unstable joint and the two attached members...\
ex2pt5.text=\ (5) Then replace them with a single member. Now the truss is rigid and can carry load. It is stable.\
ex3pt1.text=\ (1) This truss is unstable, even though it is made up entirely of triangles.\
ex3pt2.text=\ (2) Because of its configuration, there is nothing to prevent the entire truss from rotating about its supports. It is unstable.\
ex3pt3.text=\ (3) To fix the problem, add a horizontal member connecting the two halves of the truss together. Now the truss is rigid and can carry load. It is stable.\
ex4pt1.text=\ (1) This truss is also unstable, because the center panel is four-sided. This example shows that any four-sided panel--not just a rectangular one--can make a truss unstable.\
ex4pt2.text=\ (2) The four-sided panel is not rigid, so it cannot carry any load. There is nothing to prevent the entire truss from rotating about its supports. It is unstable.\
ex4pt3.text=\ (3) To fix the problem, add a vertical member to divide the four-sided panel into two triangles. Now the truss is rigid and can carry load. It is stable.\
exampleTextPane.contentType=text/html Form.title=West Point Bridge Designer - Analysis