PASSIVE DAMPING OF LARGE SPACE STRUCTURES

The complex stiffness matrix and th, mass matrix of a uniaxial bar sub jected to constrained layer damping over its entire length are derived exactly by solving the differential equations of motion of the three- layered structure. The stiffness and mass matrices of a bar with segme nted damping treatments are obtained by assembling the corresponding m atrices for each segment and eliminating the internal nodes using a re duction procedure similar to static condensation. The natural frequenc ies, mode shapes, and loss factor of a pin-connected truss containing several damped members are computed by three different methods: truss finite element (TFE) method (exact), equivalent beam element (EBE) met hod, and scaled beam element (SBE) method, each method being more effi cient than the preceding one. A 10-bay plane truss is considered as an example to illustrate each method. The EBE method yields very good re sults, but the savings in computation is not significant. The SBE meth od reduces the computational effort drastically and gives reasonably a pproximate results.