Numerical analyses on seismic behavior of helical concrete columns

Abstract

This paper presents the behavior of the helical reinforced concrete columns (HCC) subjected to horizontal 2D seismic motion excitation combined with the static axial load. Helical concrete columns are new types of elements which arose in the new twisted buildings, providing a special geometry by twisting the top section by an angle (ϕ), furthermore, offsetting the top section by a considerable distance respecting to the bottom section. In order to study seismic behavior of the HCC under a seismic load of the short period using finite element software, numerical simulation is carried out in this paper using ANSYS V 18.1 software. A brief comparison of the HCC behavior was made between different cases of conventional reinforcement in the longitudinal and transverse directions, as well as the different twisting angles (ϕ) of column sections. The comparison illustrated that all columns response with giving the same mode shapes of vibration in the modal analysis with different values of natural frequencies and relative amplitude deformations. However, the difference be very noticeable when changing the section size of the columns comparably with changing the twisting angles of the section, where increasing the section size of HCC from 250 mm to 400 mm cause increase the natural frequency by 55.4% for second mode shape, while it cause decreasing the relative amplitude response of HCC by 52.5% for sixth mode shape. The transient analysis of the six types of HCC excited by horizontal 2D seismic motion indicates the tendency of HCC to increase its responses, like twisting and buckling deformations. The deform shape-time history of 6 HCC demonstrated that with increasing (shear stress path section distance) S of HCC column which depends up on (ϕ value), the top section would have less stresses.