Analytical modeling of nonlinear hysteretic systems

The response analysis of structures subjected to strong earthquake motions requires a realistic conceptual model that recognizes the continually varying stiffness and strength degradation of the structure. Nonlinear behavior of wood structures typically results from a large number of nonlinear, nonconservative connections. Such connections are important considerations in earthquake-resistant structures, where the energy is dissipated in hysteretic joints. In developing methodologies for safety analysis and the design of structures under earthquakes, an analytical model of the connection behavior plays an important role.;In this research, a mathematical model describing nonconservative, nonlinear, load-history-dependent behavior of connection has been developed and verified by comparing it with experiments on nailed and welded steel connections subjected to cyclic loads. A system identification program to extract the parameters of the model from cyclic load experiments has been developed and tested using several sets of simulated and experimental data. A finite element based on the mathematical model has been developed and verified. The element has one degree of freedom and has been attached to a commercially available finite-element software package, thus allowing the use of the existing library of elements, preprocessing, solving, and postprocessing power of the program. The functionality of the model is demonstrated by examples of analyses of individual connections and a multidegree-of-freedom system represented by an analytical model of a shear wall. The special finite element can be used in analyses of subsystems and systems with hysteretic, load-history-dependent behavior.