A continuous slab of clear span 5 m and effective depth is 150 mm and supported on 300 mm. What is the value of effective span?
5150 mm
Calculating Effective Span of a Continuous Slab
To find the effective span of a continuous slab, we consider the clear span, the effective depth of the slab, and the width of the supports. The effective span is determined based on specific rules provided in design codes like IS 456.
According to the relevant code provisions for continuous beams and slabs, the effective span is typically taken as the lesser of the following two values:
- Clear span plus the effective depth of the slab ($\text{L}_{clear} + \text{d}$)
- The distance between the centres of supports ($\text{L}_{center-to-center}$)
The distance between the centres of supports is equal to the clear span plus the width of the support ($\text{L}_{clear} + \text{w}$).
Given Data
- Clear span ($\text{L}_{clear}$) = 5 m = 5000 mm
- Effective depth of slab (d) = 150 mm
- Width of support (w) = 300 mm
Step-by-Step Calculation
We need to calculate the two possible values for the effective span:
Possibility 1: Clear span + effective depth
\(\text{Effective Span}_1 = \text{L}_{clear} + \text{d}\)
\(\text{Effective Span}_1 = 5000 \text{ mm} + 150 \text{ mm}\)
\(\text{Effective Span}_1 = 5150 \text{ mm}\)
Possibility 2: Distance between centres of supports
First, calculate the distance between centres of supports:
\(\text{L}_{center-to-center} = \text{L}_{clear} + \text{w}\)
\(\text{L}_{center-to-center} = 5000 \text{ mm} + 300 \text{ mm}\)
\(\text{L}_{center-to-center} = 5300 \text{ mm}\)
So, the second possibility for effective span is 5300 mm.
Determine the Effective Span
The effective span is the lesser of the two values calculated:
\(\text{Effective Span} = \text{Minimum}(\text{Effective Span}_1, \text{Effective Span}_2)\)
\(\text{Effective Span} = \text{Minimum}(5150 \text{ mm}, 5300 \text{ mm})\)
\(\text{Effective Span} = 5150 \text{ mm}\)
Conclusion
Based on the calculations, the effective span of the continuous slab is 5150 mm.
Important Questions from Beams and Slabs
A reinforced concrete slab is generally considered a one-way slab if the ratio of its longer span ($L_y$) to its shorter span ($L_x$) satisfies which of the following conditions?
Minimum area of tension reinforcement in a beam shall be greater than:-
To ensure the lateral stability in a simply supported beam, the clear distance between the lateral restraints should not exceed______.
An under reinforced section means
The resultant compression forces in concrete and compression steel respectively for a doubly reinforced rectangular beam is (width of the beam = b ', depth of neutral axis = x u, Area of compression steel = A SC' , Stress in compression steel = f sc )
