In recent years, attention to pulse type earthquakes that cause large displacement responses are concentrated. Some of them are predicted much higher than the level used in the current design, so it is promoted to set new seismic waves for design and to study about new design methods. To reduce damage of buildings against large earthquake, it has been considered to increase the elastic limit deformation using high strength steels in columns and girders. In this study, on the contrary, we propose the frames using hybrid H-section columns consist of flange with high strength steels and web with conventional strength steels, and conventional girders. In the case of using the high strength steel in columns, it is difficult to avoid the column bases of the first story being plasticized in the ultimate state. So, we consider the column base models showing stable behaviors against excessive earthquake ground motion.
In Chapter 2, we show the damage reduction effect of the frames using hybrid columns and conventional girders by using fish bone shaped models that are taken out of single-spans from multi-layer multi-span flat frames have uniform members. In addition, it was also evaluated from the cost effectiveness. In Chapter 3, we propose the column base models which show stable behaviors against excessive earthquake ground motion. After understanding the static behavior by finite element models and multi-spring models, we evaluated the performance during earthquake by defining the index called the limit magnification. With H-SA700 as a high strength steel and SN490 as a conventional strength steel, assuming inner columns of high-rise buildings, using column base sections of small width-thickness ratio, we obtained the following results.
(1) The frames using hybrid columns and conventional girders, compared to the frames using conventional columns and girders composed of thickened plate, have same degree of the proof stress and the cost, and also reduced more damage.
(2) By using the frame using hybrid columns and conventional girders, we can design a high earthquake resistance building without an increase in significant cost compared to a building designed with existing standards.
(3) To increase the limit magnification in the column bases of the first story against excessive input, it is effective to have a deformation capacity without plasticizing of high strength steels of hybrid columns.
(4) The model obtained by adding a high strength steel in the center of the H-section composed of conventional steel can show stable behavior against about 2 times the level which is the largest Uemachi fault zone seismic. In addition, the superstructure reaches the deformation limit before the column base reaches the limit state. As a result, the performance of the building as the total collapse mechanism can be sufficiently exhibited.
In the future, we are going to research the combination of steel species, effects of varying axial force, the case of using column base sections of large width-thickness ratio. On the other hand, Research on the application of the frames using hybrid columns and conventional girders is under way by experiments using the test piece of the column members and the cross structures. In addition, we are going to research the behavior of the column bases by experiments.
