ABSTRACT
This chapter obtains mathematical relations between small excitations and corresponding response quantities in a discrete parameter structure. Application times and magnitudes of the excitations are such that during the loading episode the structure remains time invariant, and its excitation-response relations are linear. The chapter describes that the excitations are applied statically, i.e., no material particle gains discernible accelerations due to the application of the excitations. The internal and the external forces acting on a node must be in static equilibrium. This must hold for every node in the equilibrium state. The description of the force-type nodal loads, in the global reference frame, of node i is denoted by pi which is an e-tuple if the node is not restrained. In the equilibrium state, the external and the internal forces acting on any of the nodes or elements must have a zero force resultant and a zero moment resultant.
