SEISMIC ANALYSIS OF HIGH-RISE BUILDINGS WITH FLOATING COLUMNS

Abstract

For modern building construction, floating columns are usually, the first three to five floors mainly to be compatible to the architecture design usage. Above these floors residential units take place where there is no need for very large spaces. To consider the last conditions with high rise construction, economic design is a very important aim which must be considered, therefore floating columns are used to minimize the spans in the residential floors to reduce slab thicknesses and beams dimensions and their reinforcement can be minimized. Therefore, the total weight of the structure will be reduced and the foundation dimensions, reinforcement will be minimized. Storeys under the floating columns can be classified as soft storeys because of the sudden drop in storey stiffness from the levels with floating columns to the levels below. In this study, the seismic performance of structures with floating columns is investigated to some parameters. Such as effect of increasing height of structure, transfer beam dimensions, reinforcement and dimensions of columns. The results are presented in terms of displacement, drifts, base shear, overturning moment and quantity take-off for used material by response spectrum method. Results and analysis are carried out using Etabs 2016 software. Modeling, assigning loads and obtaining results of the structural analysis were carried out according to the provisions of the Eurocode, 2004 [5]. The results indicated that factors such as height of structure or stiffness of the storey have a noticeable effect on the structure response and quantities of material used per storey area. In addition, placing the soft floor in a level in the middle height of the building is considered the worst case compared to its position at first or roof floors. The results also demonstrated some variations in structure response along its height, mainly in inter storey drift, therefore the response of the structure with floating columns was divided into three zones, each has its own response.