IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 13, Issue 1 Ver. II (Jan. – Feb. 2018), PP 11-18 www.iosrjournals.org DOI: 10.9790/1676-1301021118 www.iosrjournals.org 11 | Page Concrete Filled Steel Tubular (CFST) Columns in Composite Structures Beena Kumari 1 1 (Department of Civil Engineering, Thapar University, Patiala, India) Corresponding author: Beena Kumari Abstract: RCC and steel frames have been the most common frame systems for long times whereas composite frame system has also emerged as popular system for high rise buildings for few decades. Multi-storey composite frames are generally composed of structural steel members made composite with concrete. The use of concrete filled steel tubes (CFST) in building construction has seen renaissance in recent years due to their numerous advantages, apart from its superior structural performance making a typical composite frame structure. Their usage as columns in high-rise and multi-story buildings, as beams in low-rise industrial buildings and as arch bridges, has become extensive in many countries in last four decades with abundant examples. But, their usage in India is a new concept. Hence, this paper shall primarily emphasis to investigate the various aspects of CSFT members in the building industry; primarily considering the various aspects of these members which have turned its unique phase with the advancement of technology. Keywords - concrete filled steel tubes, CFST Columns, composite frames and confinement --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 09-01-2018 Date of acceptance: 26-01-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction A simple definition of structural system in context with building is, “a system of connected members to support the load that results from the usage of building or only presence of building to the ground”. There are several structural systems according to purpose, size, scale and loading to which the building is subjected to. Moment resisting frame is foremost one amongst all the structural systems. Various materials are used to make columns and beams which are vital components of any structural system. Concrete and steel are pioneer materials amongst these. The choice of material depends upon numerous factors like type and purpose of building, size of building, availability of materials, topography of land, climatology and budget. RCC and steel frames have been the most common frame systems for long times whereas composite frame system has also emerged as popular system for high rise buildings for few decades. Multi-storey composite frames are generally composed of structural steel members made composite with concrete. The use of concrete filled steel tubes (CFST) in building construction has seen renaissance in recent years due to their numerous advantages, apart from its superior structural performance making a typical composite frame structure. Their usage as columns in high-rise and multi-story buildings, as beams in low-rise industrial buildings and as arch bridges, has become widespread in countries like China and many other countries in last few decades with abundant examples. But, their usage in India is a new concept. Hence, this study shall primarily emphasis to investigate the various aspects of CSFT members as beams and columns and as part of frames in the building industry; primarily considering the various aspects of these members which have turned its unique phase with the advancement of technology. 1.1 Various Types of CFST Columns There are two types of composite columns generally used in buildings, steel section encased in concrete and steel section in-filled with concrete. A concrete filled steel tubular (CFST) structure consists of steel tube of square, rectangular or circular cross-section filled with plain or reinforced concrete. Various forms of latter type of CFST composite columns are represented in Fig. 1. Following are the various types of CFST columns: i Composite column systems ii Reinforced composite column systems iii Concrete-filled double skin tubes (CFDST) iv Reinforced Concrete-filled double skin tubes (CFDST) v Concrete-encased CFST columns vi Stiffened CFST columns