A cantilever beam of rectangular cross-section having 20 m span is sub...
Given Data:
- Span of the cantilever beam (L) = 20 m
- Uniformly distributed load (w)
- Modification factor for tension reinforcement (m_t) = 0.95
- Modification factor for compression reinforcement (m_c) = 1.345
Minimum Effective Depth for Deflection Control:
The minimum effective depth required to control deflection in a cantilever beam can be determined using the following formula:
d_min = (k * L^4 * w) / (384 * E * m)
Where:
- d_min is the minimum effective depth
- k is a constant depending on the type of load and support conditions (For a uniformly distributed load on a simply supported beam, k = 5)
- L is the span of the beam
- w is the uniformly distributed load
- E is the modulus of elasticity of the material (assumed to be constant)
- m is the modification factor for reinforcement
Calculation:
Substituting the given values into the formula:
d_min = (5 * 20^4 * w) / (384 * E * m)
To determine the range of minimum effective depth, we need to assume a value for the uniformly distributed load (w) and the modulus of elasticity (E). Let's assume:
- w = 10 kN/m (uniformly distributed load)
- E = 200 GPa (modulus of elasticity)
Substituting these values into the formula:
d_min = (5 * 20^4 * 10) / (384 * 200 * m)
d_min = 4166.67 / m
Considering the Modification Factors:
To satisfy the deflection criteria as per IS 456: 2000, the minimum effective depth should be within the range of 4.4 to 4.6 meters. Since the modification factor for tension reinforcement (m_t) is less than 1, it reduces the effective depth requirement. On the other hand, the modification factor for compression reinforcement (m_c) is greater than 1, which increases the effective depth requirement.
Therefore, the correct answer is a range of 4.4-4.6 meters for the minimum effective depth required to prevent failure in deflection.