Shear to be resisted by composite steel beam (stud spacing)

[Carpetburn]

Hello,

I am looking at the longitudinal shear to be resisted by a composite steel/concrete beam.

I am following BS 5950-3 and referring to clause 5.6.2 it states that the total longitudinal shear force per unit length, v to be resisted at any point in the span of the beam = NQ/s

where N = number of shear connectors in a group, s is the distance between the centres of the groups of shear connectors (studs) and Q is the shear capacity of a single shear connector.

Going by this if I place the shear connectors further apart - i.e increase the spacing between them the amount of shear required to be resisted by them is actually reduced?

I dont have a great grasp of composite beams - but I would have assumed that if I increased the spacing the shear force to be resisted would increase?

Granted the (longitudinal) shear resistance of the beam is increased if I reduce the spacing - but if the shear force to be resisted also increases - this means that a beam could potentially fail if I reduce the spacing between the shear connectors? Is this right?

If anyone can give me any enlightenment on this subject it would be much appreciated.

- C.

 

[JKStruct]

I think you're comparing apples to oranges...

The longitudinal shear force, v (or q, or whatever you wanna call it), is equal to VQ/I, and that is the force to be transferred by your studs. You first need to calculate the demand, VQ/I (Q is first moment of area), then find the appropriate number of studs at a given spacing with NQ/s (capacity). Make sure demand<capacity. Done.

For whatever reason, this question comes up all the time here. It should be a FAQ.

 

[youngstructural]

Here here JK... Totally agree. I think I might actually expand on and make my post on the built-up timber beam from the other day into a FAQ.

Regards,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...