Large‐Displacement Effects on Dynamic Response of Eccentric Buildings

Abstract

The dynamic response of eccentric buildings under harmonic ground motion in a large‐displacement field is analyzed. In examining one‐story elastic systems, two effects of nonlinearity for the resisting elements are considered: (1) The effect of the deck rotation, modifying the compatibility relationships; and (2) the effect of the deck displacements, modifying the force‐displacement relationships. Both effects influence the stiffness matrix of the whole system, which is obtained here in explicit form as depending on the dimensionless structural parameters governing the problem. Once the mass matrix and the damping matrix are made explicit too, the latter assuming the system to be classically damped, numerical analysis is carried out by step‐by‐step integration of the equations of motion in order to point out the role of the structural parameters and of those characterizing the input. The numerical results show that the nonlinear response of certain classes of structures is considerably different from the linear response and they reveal the existence of an unstable region characterized by a response that has a prevalent component orthogonal to the input direction and that is no longer sinusoidal. In this region, the global forces acting on the deck and the dynamic magnification of eccentricity abruptly increase.