axis of structural components remains plane after bending. It will not reach a limit state The philosophy of the limit state method of design represents a definite advancement over the traditional design philosophies. WSM was based on calculations on service load conditions only, ULM was based on calculations on ultimate load conditions only and now LSM provides comprehensive and rational solutions to the design problems by considering safety at ultimate loads and serviceability at working loads. Sections designed by using the Ultimate load method are too thin that they can easily fail under excessive deformations and cracking. LSM is Strain based method of RCC design. Limit state method of design The object of the design based on the limit state concept is to achieve an acceptable probability, that a structure will not become unsuitable in it’s lifetime for the use for which it is intended,i.e. The maximum strain in concrete at the outermost compression fiber is taken as 0.0035 in bending. RCC Structural Elements are designed by two methods or two Design Philosophies, Working Stress Method (WSM) Limit State Method (LSM) Working Stress method is the old way of designing, in present era structures are generally designed using Limit State Method. ULM got accepted as an alternative to WSM in ACI code in 1956 and in British code in 1957. The tensile strength of concrete is ignored. limit state, working stress, ultimate load, What is Ordinary Portland Cement?- Chemical Composition, Properties, Uses, Types, Flow Diagram & Working of Sewage Treatment Plant- Classification, Process & Diagram, Detailed ASTM Classification of Cement | C150, C595, C1157, What is Road Gradient? Bar, For Top Reinf. The plane section before bending remains plane after bending at any cross-section. In 1900 theory by Coignet and Tedesco was accepted and codified as Working Stress Method. Know the Effects, Types, Representation, and Grade Compensation, [PDF] IS Codes for Civil Engineering- Download PDF. Modular Ratio (m = 280/(3*Sigma_cbc) )  is generally taken into consideration to calculate allowable stresses. Stress Strain behavior for concrete is non linear and time dependent thus modular ratio is not constant, and WSM does not considers consequences of this non-linearity of material. WSM also included in IS 456 : 2000 but regulated from main content of code to Annex B i.e. In RCC Design by LSM Tensile Stresses are not considered. This method was developed in the 1950s with overcoming shortcomings of WSM and introduced in the USA in 1956, the UK in 1957, and also in 1964 revision of IS 456. Limit State of Serviceability: Deflection. In WSM concrete is considered as elastic whereas in LSM concrete is generally assumed as plastic. RCC Structural Elements are designed by two methods or two Design Philosophies. Bar. In the limit state method of design, the structure should be designed to withstand safely all the loads acting on it throughout its life. In the ultimate load method, the nonlinear stress-strain curves of steel and concrete also the stress conditions just before the collapse are considered so as to avoid the problems arisen due to the imaginary concept of modular ratio (m). Using modular ratio (m) a imaginary factor ultimately results in large amount of compression steel and large member sizes than designs done by ultimate load or limit state method. Unlike WSM which based calculations on service load conditions alone, and unlike ULM, which based calculations on ultimate load conditions alone, LSM aims for a comprehensive and rational solution to the design problem, by considering safety at ultimate loads and serviceabilityat working loads. The Working Stress Method was in use for several years until the revision of IS 456 in 2000. Stress in reinforcement varies linearly with strain up to specified yield strength. Also, the structure should satisfy the serviceability requirements, like limitations of deflection and cracking. The basic concept of working stress method is adequate safety can be achieved by restricting the stresses in the material due to working loads on the structures, if we assume that structural materials in a linear elastic manner. Also this method is very simple in understanding and in application. Performance under normal service load is not considered, that is why it was realized that the design approach that combines the very best features of the working stress method and the ultimate load method will result in better structural stability and performance. Various design philosophies have been invented in the different parts of the world to design RCC structures. ULM was based on the ultimate load carrying capacity of reinforced concrete on collapse. Working Stress Method assumes that concrete and steel reinforcement in a structure acts together and are perfectly elastic and that’s why modular ratio can be used to determine the stresses in concrete and steel. Limit State Method identifies the basic instability of loads and allocates a much greater factor of safety to live loads (it may be raised by 1.5-1.6), while it identifies that dead loads are much neaer to what has been computed (dead loads are multiplied by 1.2). WSM is Stress based method of RCC design. The assumption that the stresses under working loads can be kept within permissible stresses is unrealistic or not practical. most critical limit state., and checked for other limit states. A section which is plane before bending remains plane after bending. In WSM , the material follows Hooke’s law as stress is not allowed to cross the yield limit. So the Design phase is one of the important phases in the execution of the project, which drives the execution of the project, and to the final project delivery. Now standing in 21st Century we have three design philosophies of RCC structure those are Limit State Method, Working Stress Method, Ultimate Load Method which are described in detail below. The Ultimate Stresses are considered as allowable permissible stresses. IS 456 : 2000 gives more importance to Limit State Method as it designs more economical structures. In LSM , Partial Safety Factor is considered. In this article, I’ll try to explain the procedure of the Design of an RCC beam in sequential steps, according to the limit State method of Design, as this is the most common, easy to understand, and accurate method of Design, adopted … In LSM , stress is allowed to cross the yield limit. 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