For continuous beams, the basic value of span to effective depth ratio for spans up to 10 m is:
26
Span to Effective Depth Ratio for Continuous Beams
The design of reinforced concrete beams involves ensuring both strength and serviceability. Deflection is a crucial serviceability criterion. Excessive deflection can cause damage to finishes and partitions and can be visually unappealing. To control deflection, building codes specify limits on the span to effective depth ratio for beams.
The basic span to effective depth ratio provides a guideline for the preliminary sizing of beams to satisfy deflection limits under normal loading conditions. This ratio varies depending on the type of support condition (simply supported, continuous, or cantilever) and the span length.
Basic Span to Effective Depth Ratios (Spans up to 10 m)
According to standard building codes for reinforced concrete structures (like IS 456 in India), the basic values for the span to effective depth ratio for rectangular or flanged beams for spans up to 10 meters are:
- For Cantilever beams: 7
- For Simply Supported beams: 20
- For Continuous beams: 26
For spans longer than 10 meters, these basic values are modified by multiplying them by a factor, which is usually $(10/\text{Span in meters})$.
The question specifically asks for the basic value of the span to effective depth ratio for continuous beams with spans up to 10 m. Based on the standard values, this ratio is 26.
Comparing this value with the given options:
- 34
- 20 (This is for simply supported beams)
- 7 (This is for cantilever beams)
- 26 (This matches the value for continuous beams)
Therefore, the basic value of the span to effective depth ratio for continuous beams with spans up to 10 m is 26.
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 )
