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# What is the difference between working stress method and limit state design approaches?

swathi

Answered On : Feb 22nd, 2012

The simple way to differentiate is in Limit state method we consider the factor of safety were as in working stress no fs is considered

P.K.Shanmugasundaram

Answered On : Mar 11th, 2012

Design of RCC Structures

The design of the components of the RCC structure can be done in the following two ways:

1. Working Stress Method
2. Limit State Method

Methods of RCC Design

Here are some of the design procedures of the components of the RCC structures:

Design of RCC beams
Design of RCC columns
Design of RCC staircase
Design of Foundations
Design of Simply Supported Slabs
In this article, we are going to discuss the major difference between the two important methods of RCC design. This will help us understand the mechanics of the Structural Design and which method is to be adopted for better efficiency.

Working Stress Method

The Stresses in an element is obtained from the working loads and compared with permissible stresses.
The method follows linear stress-strain behaviour of both the materials.
Modular ratio can be used to determine allowable stresses.
Material capabilities are under estimated to large extent. Factor of safety are used in working stress method.
The member is considered as working stress.
Ultimate load carrying capacity cannot be predicted accurately.
The main drawback of this method is that it results in an uneconomical section.
Limit State Method
The stresses are obtained from design loads and compared with design strength.
In this method, it follows linear strain relationship but not linear stress relationship (one of the major difference between the two methods of design).
The ultimate stresses of materials itself are used as allowable stresses.
The material capabilities are not under estimated as much as they are in working stress method. Partial safety factors are used in limit state method.

DEEPA N V N

Answered On : Apr 17th, 2012

Working stress is elastic method and limit state is plastic method

s.kaleeswari

Answered On : Jul 26th, 2012

limit state method is used for designing structure more safe but not economical.but working stress method involves design a economical one because there is no fos consideration.

sabeena.k

Answered On : Sep 30th, 2012

Answered On : Jan 5th, 2013

In working stress method design the loads are taken as the same working loads but strength increases by concrete & steel by we considering the m20 (20n/mm2 ) into 20/7=2.85 n/mm2 like that (i.e we are consider the actual strength into low strength . so for limit state the loads are increased by 50% so thats why we are multiplied by 1.5 when we are doing design but concrete strength & steel strength taken as actual.

Vanessa

Answered On : Jan 8th, 2013

In working stress method, the designs are based on the loads which are intended to be applied on the structure and limit state design method involves designing the structure based on the load limits for the code of practice in the country which involves multiplying the loads by safety factors specified by the code.