Assessment of Structural Performance Based on An Energy Balance Approach

Abstract eng:
An analytical method is developed to quantify the potential energy and other energy characteristics of the nonlinear response of framed structures subjected to earthquake ground motions. Since the potential energy relates to the stiffness of the structure, it consists of three components in a nonlinear system: (1) stored strain energy associated with the linear elastic portion of the structural response, which can be recovered after the earthquake; (2) higher-order energy associated with geometric nonlinear behavior of the structural response, which is derived from the nonlinear stiffness matrix and can also be recovered if the axial load is removed; and (3) plastic energy representing the energy dissipated by inelastic deformation of the structure, which cannot be recovered after the earthquake. The proposed analytical method uses a change in stiffness for handling the geometric nonlinearity and a change in displacement for handling material nonlinearity before solving the equations of motion, thereby separating the effects of geometric nonlinearity and material nonlinearity when computing stiffness forces. This leads directly to integral representations of each energy form. A four-story moment-resisting framed structure is used to demonstrate the feasibility of the proposed analytical method in evaluating the energy response and the transfer among different energy forms throughout the nonlinear response history analysis.

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