A study on behaviour of long and short column under dynamic loading

Abstract

Most of the multi-story buildings are built on sloping land, because of the variable ground profile. As a result, to keep the roof at the same height, the length of columns must be varied, either in the basement or on the ground floor. It is vital to examine the behaviour of such long variable-length columns under different loading conditions. One of the most significant criteria to consider in the design of structures is dynamic loads. The behaviour of short and long columns under dynamic loading was investigated in this study using a structure. In SAP2000, a 3-dimensional single storey RC structure with dimensions of 4 m × 8 m × 4.5 m is modelled with six columns, two of which are small columns of 2.5 m and four long columns of 4.5 m. The structure's intrinsic frequency and weight were determined based on the analytical analysis (SAP). The prototype model is then scaled down 10 times and analysed with steel sections in SAP; the properties of the steel are obtained through a trial-and-error method, and the dimensions of the steel sections that satisfy the frequency and weight of the prototype model, which is scaled down to 10 times, are obtained as a long column of 450 mm in length, a short column of 250 mm in length, and both columns are 75x6mm in size, while the size of the slab is 400x800mm with a 6 mm thick steel sheet. For experimental purposes, a similar steel section model is fabricated and tested on a shaking table to determine the maximum displacement for a particular frequency of around 7 Hz to 15 Hz with a base displacement of 1 mm. The maximum displacement occurred around 13.50 Hz, which is nearly identical to the frequency of the SAP model. The research also looks at the evaluation of forces on the columns and acceleration values at various frequencies from the shake table test of a single degree of freedom system.