Theory and Application of Experimental Model Analysis in Earthquake Engineering

This report summarizes part of a four year study on the feasibility and limitations of small-scale model studies in earthquake engineering research and practice. The emphasis is placed on dynamic modeling theory, a study of the mechanical properties of model materials, the development of suitable model construction techniques and an evaluation of the accuracy of prototype response prediction through model case studies on components and simple structures. Steel and reinforced concrete structures are considered in this study.

The basics of similitude theory and its application to the modeling of dynamically excited structures are reviewed and similitude laws for various types of models are developed. These models include true replica models in which all physical quantities are properly simulated, and various kinds of adequate models in which the violation of specific similitude laws does not affect appreciably the response prediction.

Adequate simulation of material properties was found to be the most important aspect of model research, particularly under dynamic excitations. Materials for modeling of steel structures (structural steel and copper alloy 510) and reinforced concrete structures (wire-reinforced microconcrete) are investigated under low and high strain rates and with due regard to cyclic load effects. A comprehensive set of material data is assembled for direct use in model studies, and systematic material testing procedures are developed for the investigation of alternative model materials.

Problems encountered in the construction of models are identified and recommendations are made for the fabrication and joining of model elements for steel structures as well as for microconcrete mix design practices, fabrication of model reinforcement and fabrication and curing of reinforced microconcrete elements. The adequacy of the simulation of prototype response is evaluated on
hand of a series of tests on models for which prototype test data are available. The correlation between model and prototype response is judged as good to excellent, depending on the type of structure. Whenever discrepancies in the response are observed, the causes are identified and evaluated to assess the limitations of model research in earthquake engineering. The test specimens used for this purpose are cantilever beams made of steel, phosphor bronze and microconcrete, and simple single degree of freedom structures made of steel and phosphor bronze which are tested on a shake table.

The research has demonstrated that model analysis can be used in many cases to obtain quantitiative information on the seismic behavior of complex structures which cannot be analyzed confidently by conventional techniques. Methodologies for model testing and response evaluation are developed in the project and applications of model analysis in seismic response studies on various types of civil engineering structures (buildings, bridges, dams, etc.) are evaluated.