Shake Table Tests to Examine the Seismic Performance of Prefabricated Steel Unit Houses

Shake table tests were conducted to examine the seismic performance of prefabricated steel unit houses, which are modular steel frames comprising four corner columns and light-gauge steel beams that can be assembled vertically and horizontally as needed. The product of interest has the shorter beam shop welded to the column, and the longer beam connected to the column using a slip-critical bolted connection. Three specimens were constructed, each comprising 4 unit-house units connected vertically and horizontally, furbished with external wall panels. The JMA Kobe record, whose intensity is twofold greater than Japanese code requirements, produced a maximum story drift of 0.029 to 0.045 rad. After experiencing this motion twice, structural damage was observed in the short-side frame: weld fracture in the lower beam, local buckling of the upper beam, and bending of column base plates. In the long-side frame, much of the inelastic energy was dissipated by repeated slipping of the bolted connections. At story drifts larger than 0.01 rad, the wall panels supplied as much lateral stiffness and strength as the structural system. Overall, the tests demonstrated excellent performance of the unit house beyond the current Japanese code requirements for ordinary, non-temporary buildings.