A various type of seismic passive control system has been developed on many countries with frequent earthquakes. And also, these are categorized from the viewpoint of structural system, resistant mechanism, material, etc. as shown Tables 1, 2. Herein, a new passive control system called Scaling Frame (abbreviated SF) has been suggested as shown in Fig. 1. In our previous studies of SF structures, the fundamental resistant characteristics are investigated experimentally as shown in Fig. 2, and the analytical method of SF structures which is adopted on steel frames has been proposed.
In this study, the ultimate seismic response behavior and response mitigation effects of SF on wooden structures are investigated by shaking table tests on one-story wooden framed test specimen. Herein, four test specimens of various structural types are prepared with SF and structural plywood installed as shown in Fig. 3 (a), (b). And the input wave are assumed as follows; 1) foreshocks to investigate the standard seismic performance, 2) main shocks to estimate the ultimate seismic response behavior, 3) aftershocks to analyze the fail-safe mechanism of SF structures, and 4) mega earthquake input to study the ultimate limit state of test frame specimens.
From the test results (Figs. 9, 10, 11, 12), the following behaviors are observed;
In case of test specimen which consists of plywood only, the slip behavior and deterioration of restoring force are generated (see Figs. 9, 10). And also, the response story drift becomes large after main shocks input because the plywood does not resist.
On the other hands, in case of test specimen with SFD installed, the stable hysteresis loop is observed (see Figs. 9, 10). And the residual restoring force is obtained after main shocks input. Furthermore, it is observed that good plastic energy absorption of SFD is presented during ultimate seismic response (see Figs. 9, 10).
From these observations, SFD has good seismic resistant performance from the point of seismic mitigation effects and plastic energy absorption. Furthermore, SFD becomes fail-safe element after the plywood is experienced under severe damage.
The equivalent viscous damping factor is calculated from the test results, and it is clarified that the SF structure has high damping factor during ultimate state (see Fig. 13).
Next, the analytical studies are performed to investigate the ultimate seismic response behavior and the accuracy of dynamic response analytical method. The skeleton curves of each member (frame, plywood and SFD) are extracted from the envelop curves of test results (see Fig. 14). And from the observation of test results, each restoring force characteristics model can be summed from the summation rule. The response analysis is performed, and the results are compared with test results, the accuracy of analysis method is concerned (see Figs. 9, 15). And also, the fail-safe mechanism during seismic response is presented analytically (see Fig. 16).
Finally, the analytical results of equivalent viscous damping factor are calculated by use of above analytical method. From the comparison analytical results and test results (see Figs. 13, 17), it shows good agreement with each other.
So then, the main conclusions of this paper are as follows: The specimen by use of only plywood shows the slip on hysteresis loop and the larger response displacement because of damage of plywood. However, the specimens with SF device installed don't show the above results after even plywood damage. Therefore, installing SF device shows equable hysteretic behavior, and mitigation effects of SF structure after plywood does not function as seismic resistant element during ultimate state. And also, the accuracy of response analysis method can be presented.
