Comparison Of Structural Systems For Composite Construction In High Rise Building

Abstract

The evolution of structural systems and the technological developments are driving force behind the growth of tall buildings around the world. Frame tube system is one of structural system used in tall buildings which forms a tube by closely spaced wide columns and deep spandrels connecting them. This system can be adopted for RCC and steel construction but due to shear lag phenomenon, capacity of structural members is not fully utilized. Also due to closely spaced columns, exterior view gets blocked and size of windows reduces. In order to eliminate these drawbacks and to improve economy, a relatively new structural system i.e. Megaframe with supercol- umn with composite construction is developed. Composite construction has brought a new era for high rise buildings with advantages of better economy, high structural efficiency, light weight, better performance under gravity and lateral loading. In the present study, analysis and design of three structural systems i.e. RCC frame tube, steel frame tube and composite megaframe with supercolumn is pre- sented. For comparison of structural performance of these systems, 96 storey building with plan dimensions 60.96m 36.576m and height 380.16m is considered. In addi- tion to gravity loading, lateral loading due to earthquake and wind are considered. Wind forces are calculated using Gust factor method as per IS875-III and earthquake forces are estimated as per dynamic method of IS1893. ETABS software is used for modeling and design of structural elements. Analysis results in terms of natural time period, storey shear, overturning moment, lateral drift, storey displacement, forces in critical members are compared for all the three structural systems. For the design of composite structure, specifications of Euro Code 4 are followed. Based on the design of structural systems, consumption of basic materials like concrete and steel is com- pared for all the three structural systems. Cost of the building with three structural systems is also presented. Gravity load intensity per unit oor area is also calculated to understand variation in dead load. Based on study, the megaframe with supercolumn is proved more economical and efficient structural systems compared to RCC frame tube and steel frame tube for the building considered. Gravity load intensity of the steel frame tube is least but it is more expensive. RCC frame tube exhibits higher gravity load intensity which may increase cost of foundation.