In 1995 Hyougoken Nanbu Earthquake, the soft-first-story buildings suffered significant damage because the buildings had to consume most of energy by the soft-first-story columns. For the preventative measure of this type of failure, it is well-known that making the soft first story stronger (i.e., increasing the column size) is efficient. But, in this case, the strength of super structure becomes large and the inertial force from the superstructure significantly influences the design of the foundations, especially in soft soil sites. In the traditional design, it is thought that the foundation should be stronger than the superstructure, i.e., the foundation should not suffer damages during great earthquakes. In this research, an alternative is proposed that reduces the reinforcement of foundation members and forces yielding in the foundation. To consider the effect of the yielding foundation on the seismic response of the superstructure, soft-first-story buildings supported by pile foundations were analyzed. The yielding of grade beam and the yielding of pile were defined as the yielding of foundation, and the strengths of grade beam and pile were changed as the parameters. For the model of the analysis, a 2-D frame structure model was connected with a free ground column by nonlinear soil (p-y) springs. The results from the dynamic analyses showed that the yielding of grade beam and the yielding of pile can reduce the seismic response of the soft first story during the great earthquake. And also it was indicated that the energy consumption of the soil in the vicinity of pile decreases the total energy consumption of the structure, and the yielding of foundation derive not just the energy consumption of the foundation members but also the extra energy consumption of the soil in the vicinity of the pile.
展开▼
