Concept:
Control of Deflection:
The deflection of a structure or part thereof shall not adversely affect the appearance or efficiency of the structure or finishes or partitions. The deflection shall generally be limited to the following:
a) The final deflection due to all loads including the effects of temperature, creep, and shrinkage and measured from the as-cast level of the supports of floors, roofs, and all other horizontal members, should not normally exceed span/250.
b) The deflection including the effects of temperature, creep and shrinkage occurring after the erection of partitions and the application of finishes should not normally exceed span/350 or 20 mm whichever is less.
The vertical deflection limits may generally be assumed to be satisfied provided that the span to depth ratios are not greater than the values obtained as below:
Basic values of span to effective depth ratios for spans up to 10 m:
Type of beam |
Span/depth ratio |
Cantilever beam |
7 |
Simply supported beam |
20 |
Continuous beam |
26 |
For spans above 10 m, the values in (a) may be multiplied by 10/span in meters, except for cantilever in which case deflection calculations should be made.
Explanation:
For the simply supported beam having span less than 10 m the value of span/depth ratio is 20