**Determination of effective length of simply supported beam**

● **introduction** :- hi guys in this article we know about determination of effective length of simply supported beam and what is effective length and what is simply supported beam and how we calculate effective length of simply supported beam.

As we know beam is load bearing structure member of building and their design should be made according to IS code because of calculation of effective length is quite helpful in their designing.

**What is simply supported beam**

Beam is load bearing structure if it has two support at their end then it is known as simply supported in other words those beams which are supported by tw support at their end and beam is flexural number of building structure consist of compression and tension bending moment.

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**What is effective length of simply supported beam**

Effective length of simply supported beam shall be taken as the smaller of the distance between the centre of bearing support or the clear span between two supports + effective depth of beam. Effective span of simply supported beam least of the following which one is smaller value:-

**1) clear span + effective depth of beam**

**2) Centre to Centre distance between two supports**

Now taking the short definition of following terms that’s help in understanding the effective length

1) **Clear span:**– Clear span is distance between inner edge of two supports for beam and it is represented by c.s.

2) **effective depth of beam** :- effective depth of the beam is the distance from the tension Steel to the edge of compression fibre. In other word it is also described as effective depth of beam is equal to overall depth minus the effective cover of reinforcement.

**effective depth = depth _ effective cover**

3) **effective cover** :- is the distance measured from the the outer face of concrete member to the centre of main reinforcement in tension zone or compression zone.

**effective cover = Clear cover + half dia of main reinforcement**

4) **Clear cover** :- and clear cover is defined as distance from the outer face of concrete member to the outermost face of reinforcement including shear or torsion stirrup or link.

**Clear cover = concrete cover+ dia of stirrup**

**How to calculate effective length of simply supported beam**

Given following diagram we have simply supported beam which is supported by two column at both end and their different values are following

**Clear span of beam = 4000 mm inner edge distance**

**Width of column** = 300 mm

**Depth of beam** = 300 mm

Dia of main reinforcement used in beam = **12mm**

**Clear cover = 25 mm**

**Calculation** :- value of effective length for simply supported beam is calculated by two factors, and which one have smaller value will be taken as effective length of simply supported beam

1) clear span + effective depth of beam

2) Centre to Centre distance between two supports

1) effective length = clear span + effective depth of beam

We have clear span = 4000 mm

depth of beam = 300 mm

effective depth = depth _ effective cover

efective cover = Clear cover + half dia of main reinforcement

effective cover = 25 mm + Dia/2

effective cover = 25 mm + 12/6 mm

Effective cover = 25+6 =31 mm putting this value

effective depth = 300 mm _31 = 271 mm

effective length of beam = 4000 + 271 mm

effective length of beam = 4271 mm

Now do another calculation

2) effective length of beam is equal to Centre to Centre distance between two supports

C–C distance = clear span + half of width of two column

Effective length = 4000 + w/2 +w/2

Width of column = 300 mm put this value

Effective length = 4000 +300/2 +300/2

Effective length = 4300 mm

1) in case first effective length of simply supported beam is coming 4271 mm

2) in case second effective length of simply supported beam is coming 4300 mm

You have to choose smaller values between two cases and smaller value is 4271 mm. So 4271 mm is effective length of simply supported beam.