Generally L/d is used to determine the slenderness of a concrete beam. Whith L/d ratios greater than 10 u can generally neglect shear deformability. By the way I do not fully understand your answer. Can u reword it?

the difference between short and long span beam is that in the first one we can't neglect the effect of shear in flexure behavior, but for long span beam we can neglect the effect of shear in flexure design. the ratioin to define the short span beam is when L/d

Thank you, noted. L/d >10 is long span beam, can neglect the shear deformability while L/d < 4 is consider as short span beam and must take into consideration about the effect of shear in flexure behaviour....^^

The attached plot refers to a cantilever beam with rectangular cross section. L/d is reported on the horizontal axis. The relative difference between the Euler-Bernoulli beam model (only flexural deformability) and the Timoshenko beam model (flexural and shear deformability) is reported on the vertical axis.

How do i get L/d ratio for a beam with rectangular(breadth*height) cross section , L is length of beam, and what does d means.?

If i consider a beam of length L with circular cross section (hallow), what is d in this case..?

L is the length of the beam, strictly speaking the clear span of the beam and d can be height of the beam, strictly speaking effective depth of the beam. 

For circular sections, for simplicity you can convert the circular section in an equivalent rectangular section for this case only. We cant always use this analogy for circular sections as many parameters for circular sections are different from rectangular.

Thong chia chia ...Good question… Please check references below.. hope it will be helpful for you…

Regards…

https://cdn.filepicker.io/api/file/QpUMVCYVTnODuI2MxVWD?