鉄筋コンクリート造腰壁付柱に設けたスリットの効果に関する研究

Abstract

Spandrel-walls frequently adopted for reinforced concrete buildings such a school and hospital sometimes cause shear failure of columns, which accidentally bring brittle failure of whole structure. Typical earthquake damages of building in which the existence of spandrelwalls was considered as one of majar reason of their damages were seen in the 1968 Tokachi-oki Earthquake and the 1983 Nihonkai-Chubu Earthquake. Recently structural design method where columns are intentionally separated from spandrel walls by slit have been adopted so that such brittle failure of columns with spandrel wall might not occur and that total structure might resist earthquakes by ductility capacity. This paper describes experimental results of column and spandrel wall assemblies with or without slits subjected to reversing static lateral loads, focusing on the effect of slit on the crack and failure patterns, yielding sequences of reinforcing bars and deformation capability. The test results of the strength of slit were compared to the analytical results based on strain distribution along the height of slit and stress vs. strain relations of concrete. Through the tests results and comparisons between test and analytical results, the following conclusions were drawn ; i) specimen without slit and specimens with thick slit faild in shear while specimens without spandrel wall and specimens with thin slit faild in flexure, ii) the strength of slit was expressed by the thickness of the concrete of a slit, the height of a slit and the compressive strength of concrete, and iii) the dimension of the concrete of a slit should be designed by based on the comparison between the strength of a slit and those of columns and beams.