Nonlinear dynamic behavior of saddle-form cable nets under uniform harmonic load

The dynamic response of saddle-form cable nets is investigated in this paper. Even though they consist of cables, which are well known for their geometric nonlinearity, such systems could be characterized as weakly nonlinear due to the high levels of pretensioning of their cables and to their hyperbolic paraboloid surface, having opposite curvatures at all points and thus increased stiffness. Nevertheless, resonance phenomena that are typical of highly nonlinear systems are detected here, for common geometries and levels of pretension, even for low levels of load amplitude. First, a single-degree-of-freedom (SDOF) cable net is studied analytically and numerically, and nonlinear resonances are confirmed. Then, the response of multi-degree-of-freedom (MDOF) cable nets, subjected to harmonic dynamic excitation, is investigated. Although the static response is proved to be almost linear, the dynamic nonlinearity is intense, as verified by jump phenomena, bending of the response curve, superharmonic resonances, and dependence on the initial conditions.