Form Determination - Tensile Fabric Structures: Design, Analysis, and Construction - page 85

 L A E

F i =

i i i

(5.5.3-7)

L

i

However, in form finding, the member forces are generally known with the
configuration being unknown. In this case the stiffness is established by the member
force and current configuration.

The time increment, mass and damping are fictitious. Their values are selected for
analytic convenience. Typically 1 is used as a time increment. The mass must be
small enough to capture the vibration cycle in the analysis. The viscous damping
coefficient needs to be selected to ensure convergence of the solution.

Selecting a time increment of 1, a mass of 0.1 and no damping, evaluate the vertical
displacement of Figure 5-15.

Figure 5-15
Dynamic Relaxation Example, Single Degree of Freedom
(Drawing by the author)

The positions of points A, B, & D are determined
The applied load P CY is given
A target prestress, F i , has been set
Assume C X is fixed at 2000, Solve for C Y (Single degree of freedom
example)