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Unformatted text preview: Statically-Determinate Truss Structure A truss structure resists two vertical loads F C and F E as shown in the figure. This cantilevered truss is constrained in the X and Y directions at point A and constrained in the X direction only at point B . L A B C E D h F C E F L Y X The following equation may be used to calculate the number of degrees-of-freedom (DOF) associated with this truss: J N DOF 2 1 3 , where N is the number of struts, including ground, and J is the number of joints connecting the struts. There are N = 7 struts, including ground and there are J = 9 joints (1 sliding joint at B plus 8 rotary joints; there are 3 independent rotary joints at C and 2 independent rotary joints at D ); therefore 9 2 1 7 3 DOF . Zero DOF means this is a statically-determinate truss; if this number were negative, the truss would be statically indeterminate and the following methods would not be sufficient. If DOF is greater than zero, the device has motion and is not a truss structure. The truss height is fixed to h = 1 m , and the angle may be varied by the user. From geometry, the horizontal truss strut length L is: tan...
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- Spring '11