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Basic Of Civil Engineering

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Working Stress Design Method And Its assumptions with Limitations

 

Working Stress Design Method Definition:

Working Stress Design Method is a method used for the reinforced concrete design where concrete is assumed as elastic, steel and concrete act together elastically where the relation ship between loads and stresses is linear .

 

Assumptions of Working Stress Design Method

  1. Plane Section before bending will remain plane after bending
  2. Bond between steel and concrete is perfect with in elastic limit of steel
  3. The steel and concrete behaves as linear elastic material
  4. All tensile stresses are taken by reinforcement and none by concrete
  5. The stresses in steel and concrete are related by a factor known as “modular ratio
  6. The Stress-strain relationship of steel and concrete is a Straight line under working load

Limitations of working stress method :

  1. The assumptions of linear elastic behaviour and control of stresses within specially defined permissible stresses are unrealistic due to several reasons viz., creep, shrinkage and other long term effects, stress concentration and other secondary effects
  2. Different types of load acting simultaneously have different degrees of uncertainties. This cannot be taken into account in the working stress method
  3. The actual factor of safety is not known in this method of design. The partial safety factors in the limit state method is more realistic than the concept of permissible stresses in the working stress method to have factor of safety in the design.

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Stress Strain Diagram For mild Steel and Concrete and copper

Welcome to howtocivil .Today ,I discuss about two diagrams,

1. The Stress Strain Diagram For mild Steel and

2.Stress Strain Diagram For Concrete !

I explain  those diagrams in another Article . Ok ! let’s see the Stress Strain Diagram For mild Steel .

 

The Stress Strain Diagram For mild Steel

1.

 

2.

 

The Stress Strain Diagram For Concrete

1.

2.

 

stress strain diagram for Copper

 

If You have any Question Please comments below ! please share stress strain curve for mild steel and concrete and  copper

Reference : Quora ,Unsolved-Engineering,

 

Ultimate Stress Design Method And Its assumptions with Limitations

 

Ultimate Stress Design Method :

Ultimate Strength Design method is used extensively and almost exclusively in many countries for structural design practice .The Working Stress Design (WSD) method designs RC sections assuming them to be within their elastic limits, where stresses are proportional to strains. Large margins or factors of safety are assumed on material strengths to ensure such behavior. It is equally, if not more important to predict the ultimate strength of RC sections so that they can be designed to resist the largest loads anticipated during their design lives. The materials are not expected to remain within their elastic limits at such high stresses. More realistic methods of analysis, based on actual inelastic behavior rather than assumed elastic behavior of materials and on results of extremely extensive experimental research, have been performed to predict the ultimate strengths .The Ultimate Strength Design (USD) method, derived from such works .

 

Assumptions of Ultimate Stress Design Method :

 

  1. Stress in reinforcement varies linearly with strain up to the specified yield strength. The stress remains constant beyond this point as strains continue increasing. This implies that the strain hardening of steel is ignored.
  2. Concrete sections are considered to have reached their flexural capacities when they develop 0.003 strain in the extreme compression fiber.
  3. Strains in reinforcement and concrete are directly proportional to the distance from neutral axis. This implies that the variation of strains across the section is linear, and unknown values can be computed from the known values of strain through a linear relationship.
  4.  Tensile strength of concrete is neglected.
  5.  Compressive stress distribution of concrete can be represented by the corresponding stress-strain relationship of concrete.

 

Limitations of Ultimate Strength Design Method :

 

Collapse of  FLEXURE,COMPRESSION,SHEAR,TORSION 

 

 

Reference : UAP BD ,Design for Flexure By Murat Saatcioglu,Quora

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Basic Difference between WSD and USD Method of Reinforced Concrete

Hello Everyone,Thank for your interest to read my article .Today I will share some Basic Differences of WSD(Working Stress Design )  Method and USD (Ultimate Stress Design)  Method of reinforced Concrete.

At First we need to know What is Exactly WSD and USD Method in reinforced Concrete  ?

You got the Basic Definition of Working Stress Design and Ultimate Stress Design and their Assumptions in my another articles .

WSD(Working Stress Design ) Definition and Assumption   and USD (Ultimate Stress Design)Defination and Assumption

 

The Difference between Working Stress Design and Ultimate Stress Design  method of Reinforced Concrete Are ,,

USD(Ultimate Stress Design)  MethodWSD(Working Stress Design) Method
Its primarily based on strength concept of ConcreteIts based on the linear theory or elastic theory .
Its Consider to Design  Critical Combination of load Its Consider to Design  carrying load
Its Designing to elastic behavior of materials . Its Designing to plastic behavior of materials
Materials strength to be used for member Design . Modular Ratio used for member Design
Stability of Structure is more then WSDStability of Structure is less then USD
Low Cost Design MethodHigh Cost Design Method

 

If you have any Question please comments below ! If you like The  Comparison of Working Stress Design and Ultimate Stress Design method then please share it .Thanks

The basic Differences between pipe flow and open channel Flow  are given below

Pipe Flow :

pipe-vs-open-channel

Open Channel Flow :

No.OPEN CHANNEL  FLOWPIPE FLOW
1Flow occurs due to gravity .Flow occurs due to different in pressure .
2The maximum velocity occurs at a little distance below the water surface.The maximum velocity occur at the center of the pipe .
3.Cross section of open channel can be trapezoidal, triangular,rectangular ,circular etc.Cross section of pipe generally round .
4.HGL(Hydralic Gradient Line ) coincide with water surface line.HGL(Hydralic Gradient Line ) do not coincide top surface of the water

I just add four basic difference between pipe flow and open channel flow here . If you want to add some please ,post your comment below .

Thanks !

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