Brace Fractures and Analysis of Phase I Structure

Bracing members in concentrically braced structures may be subjected to large cyclic deformations in post‐buckling range during a severe earthquake causing possible early fractures. This paper investigates the phenomenon and presents an empirical criterion to predict the fracture of rectangular tubular bracing members. The criterion includes two parts: normalizing axial deformation cycles into standard cycles, and predicting the fracture life of the bracing members in terms of the standard cycles. The criterion is incorporated into DRAIN‐2DM, a general purpose computer program for dynamic analysis of inelastic structures. The U.S.‐Japan Phase I test structure, a six‐story, two‐bay by two‐bay steel structure with concentric bracing, is analyzed using the criterion and analytical results are compared with the test results.