Study On Seismic Reduced Function Of Sand Cushion

Earthquake is a natural phenomenon, its specific motion character and all behave already have very great random. But our country is a much earthquake country, seismic areas are more distributed, earthquake happen frequently. The areas of seismic fortification intensity over 7 degree occupy 1/3 of our country. The 60's and 70's, the great earthquake of XingTai, HaiCheng, TangShan etc. had given the most suffering for people; recently earthquake enter the active stage again, threaten the life and properties of our people seriously. The appointment of anti-seismic lessen disaster is more important.The traditional seismic design assured the seismic safety of structure by the way of raising the function of strength and strain of the structure and structural mumbers, it was uneconomic undoubtedly. Along with the deep development of scientific research and scientific test, all assumptions and way of seismic reduction and seismic isolation emerged as the times require.The dissertation established a new way of seismic reduction by sand cushion. The sand cushion seismic reduction is put some thickness, dense and water content sand cushion between the foundation and ground, when earthquake have acted sand cushion happened plastic shearing strain, reduced the input of high frequency volume, thus consumed the earthquake energy form the down soil, and during the transmission of the wave, sand cushion itself had low rigidity comparatively, that means added a comparatively soft spring below the foundation, stood between the earthquake energy transmitted to the structure, as a result reduced the seismic for the structure.By the way of theoretical analysis by compute and the shaking table sand box seismic imitative test, the dissertation initially probed into the seismic reduction function of sand cushion and some factors which maybe influenced it, thus will provide theoretical basis for applying this technology in engineering. Theoretical analysis and testing result indicated that the rigidity, thickness of sand cushion, the type, frequency spectrum and the acceleration peak value of the input waves will take effect it, and it will be different according to the combination of all factors.Form the dissertation studied can initially make sure the seismic reduction function of sand cushion for the middle and low building in theoretically, and draw material widely, construct simply, it is a way of anti-seismic for our wide areas of village and small towns.