Small-Scale Model Experimentation on Steel Assemblies, U.S.-Japan Research Program

The study summarized in this report is concerned with small-scale model testing of components and subassemblies of a steel braced frame structure. Correlation with a full-size prototype structure was made possible by replicating portions of tests performed on a full-size building and components at other institutions.

The objectives of this model study are 1) to investigate the feasibility and limitations of small-scale model testing in earthquake engineering, (2) to study the simulation accuracy of specific failure modes in small-scale models, (3) to correlate results of tests at different scales to assess prototype response prediction from experimental studies, and (4) to study the behavior of braced frame structures.

In order to fulfill these objectives, all model test specimens were made to be "exact" replicas of prototype buildings or full-scale components tested by others as part of a U.S.-Japan cooperative research program. The specimens tested included 1:12.5 scale models of one interior and two exterior beam-column assemblies and a 6 story braced frame unit.

The small-scale models were found to reproduce the global elastic and inelastic response characteristics of their prototype counterparts very well. Localized failure modes were simulated less accurately, with the model specimens exhibiting usually slower deterioration in strength and stiffness than the prototype.

The test results give a clear picture of the strengths and weaknesses of a dual system with steel K-bracing. Brace buckling causes severe deterioration in story shear resistance but the presence of a ductile moment frame surrounding the bracing system provides ductility and vertical load carrying capacity after brace buckling.