Asif Ali et al. Int. Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 6, Issue 10, ( Part -4) October 2016, pp.62-65 www.ijera.com 62 | Page Assessment of Methods for Development of Confinement Model of Low Strength Reinforced Concrete Columns: A Review Asif Ali*, Muhammad Javed** *(Department of Civil Engineering, University of Engineering and Technology, Peshawar, Pakistan ** (Professor, Department of Civil Engineering, University of Engineering and Technology, Peshawar, Pakistan ABSTRACT Reinforced Concrete is composed of concrete and steel, where compressive strength of concrete and tensile strength of steel are utilized to achieve the required member strength. The high tensile property of steel is thus used to confine and increase compressive strength and ductility of RC columns. Confined concrete is defined as concrete that is restrained laterally by any internal or external means i.e. reinforcement consisting of steel stirrups or spirals, Fiber Reinforced Polymer (FRP), Circular Concrete Filled Steel Tube, RC shell jacketing etc. An appropriate amount of confinement increases the strength, ductility and energy dissipation capacity of RC members. This paper focuses on finding out strength and ductility enhancement of low strength RC columns by reinforcement using existing confinement models. Confinement models are stress-strain curves developed for concrete compression member under uniaxial or dynamic loading, confined with transverse reinforcement. Different models along with their experimental validations are discussed in this paper to get state of the art knowledge of confinement studies possible for low strength concrete. The models recommended from this study are used to evaluate existing structures made with low strength concrete. Keywords - confined concrete, axial loads, ductility, low strength concrete, confining models I. INTRODUCTION Since designing of structures for response in elastic range to greatest likely earthquake is highly uneconomical. It is necessary to design structures which can dissipate energy in the inelastic region of deformation, which requires ductile design of certain members. Careful use of transverse reinforcement can induce ductile behavior (by confining the core area) in concrete sections. As reinforced concrete columns transfer load from slabs and beams to foundation of the structure, plastic hinge formation is discouraged in columns and is reflected in different building codes as “strong column-weak beam” concept. The flexural strength design of columns in a frame structure are thus factored for the flexural strength of beams joining at a beam-column joint. This awareness for prevention of plastic hinging in columns requires confinement of concrete through transverse reinforcement[1]. Surveys conducted after 2005 Kashmir earthquake has particularized that low strength than specified design strength of concrete has been found extensively and is one of the major cause of destruction. Different reports have made it evident that lower concrete strength than specified design, less reinforcement ratio than code provision, poor structural configuration, honey combing in concrete etc. [2][3] were the major cause of large scale destruction in the region[4]. Confining models are needed for evaluation of these structures for the provided transverse, longitudinal reinforcements and concrete strength. The existing models for evaluation of strength and ductility with varying confinement have been extensively used for normal to high strength concrete. For use in assessment of low strength concrete columns a critical review of existing confining models with their experimental validation is discussed. 1.1. Scope of literature review Models considering confinement in normal to low strength concrete and with low transverse reinforcement ratios are considered as it is general code of practice found in existing structures. Also it is noteworthy that some recent confining models need much computational efforts which in some cases imply undue accuracy. Also the data needed in such models cannot be easily obtained in case of existing structures. Therefore, such models are avoided in forth mentioning. II. REINFORCED CONCRETE CONFINEMENT MODELS Various confinement models for concrete columns under axial concentric compression are generated based on experimentation. The difference in results of different models can be attributed to the test sample particulars and the considered variables in development of model. Kent and Park (1971) [5] RESEARCH ARTICLE OPEN ACCESS