What is Effective Span,And How to calculate it?

In RCC effective span plays a vital role in designing the beam, slab, and any other structural member related to RCC.

The effective span for the beam and slab (Generally one-way slab) is calculated in the same way.

• Why do we need to calculate effective span?
• ➡ As per IS 456 2000 ( Page No- 34 )
  1. Simply supported condition:
  2. continuous support condition:
  3. cantilever support condition:
  4. Frame structure:
  5. Bridge or Flyover:

Why do we need to calculate effective span?

Dear learner, In this Article, we will discuss the Effective span. So, before we delay, let’s start.

To calculate the bending moment diagram we need effective span to calculate effective span.

➡ As per IS 456 2000 ( Page No- 34 )

Effective span depends on support condition so effective span is different for different support conditions which is explained below.

Simply supported condition:

For simply supported conditions effective span is calculated as shown in the figure by a minimum of:

Where:

l_o=  clear span              l_eff   = Effective span      

d = effective debt of beam or slab   

w = width of support 

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continuous support condition:

Effective span for continuous support condition calculated in two cases:

Case 1:  If support width w is less than l_o/12  then in this case effective span is calculated as shown in the figure.

l_o=  clear span              l_eff   = Effective span      

d = effective debt of beam or slab 

  w = width of support 

Note 1: same as simply supported condition. 

Note 2: clear span for beam or slab is defined as the distance between one face of support to another face of support.

Case 2: If the support width is greater than l_o/12, or  600 mm in this case effective span is calculated as as shown in the figure.

l_o=  clear span              l_eff   = Effective span      

d = effective debt of beam or slab    w = width of support 

cantilever support condition:

Effective span for cantilever support condition calculated in two cases. 

Case 1:  When one end is fixed for the cantilever support condition.

 Case 2:  When one end is continuous for cantilever support condition. 

Frame structure:

Effective span for friend structure is calculated as center to center distance between the beam and column.

Bridge or Flyover:

The effective span for Bridge or flyover is calculated as center to center distance between bearing systems.

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