Seismic Performance of Concrete Structures with Stiffness Irregularities

Concrete buildings with vertically irregular configurations have been severely damaged or even collapsed due to the formation of a story mechanism during severe earthquakes. In such buildings, the irregularity was usually located at the first story in the form of discontinuous wall or increase in the height of this story due to the functional requirements. In this paper, the structural behaviour of concrete buildings with lateral irregular stiffness under some recent earthquakes is discussed. Several idealized models were made to represent different structural configurations including pure frame, frames with fully or partially infilled panels, and frames with a soft story at the bottom level, and comparisons were made on the fundamental periods, base shear, and strain energy absorbed by the bottom level between these structures. Results obtained in this study illustrate that seismic forces were increased when a soft story was present in the bottom of the buildings for structures with similar configurations. In addition, deformation of the structure tends to be concentrated in the same area, drawing a major amount of strain energy into the components, and may accelerate the failure of the structure.

کلیدواژه ها:

(Concrete buildings ، Story mechanism ، Irregular stiffness ، Soft story)