Hospital Pendants Structural Calculation

[mpw]

Hi,I m asked to calculate the allowable load for a designed hospital pendant which needs to be mounted on the ceiling.The company has given me a similar sample to take reference but I have a lot of steps which I don't understand, so sorry there may be a lot of questions I need to ask for...First, at page 3, Spreading area = (560+2x90)x(311+2x90) = 740x491mm^2 I don't know where are those numbers come from?And at page 4 about the Restoring moment about edge, I also don't understand the whole step, where 9.8 kN comes from and FS = 14>1.5. Does FS mean Factor of Safety?And last at page 6, starting from Check Restoring Moment: 3 nos. of M10 HSLIt will be grateful if anyone could explain whole calculation steps.Thank you for helping 

https://www.dropbox.com/s/gy6sl2ms1wmqwco/Door%20Detail%20WD04.2.pdf?dl=0

 

[Andy Lin]

First, at page 3, Spreading area = (560+2x90)x(311+2x90) = 740x491mm^2 I don't know where are those numbers come from?

I think that's a typo. Should be 540 and 302.

90 might be depth of concrete minus rebar cover.

And at page 4 about the Restoring moment about edge, I also don't understand the whole step, where 9.8 kN comes from and FS = 14>1.5. Does FS mean Factor of Safety?

9.8 seems like the capacity of the anchor but I can't figure out where he got that from either. He then uses that capacity to calculate the moment capacity so FS = Factor of Safety sounds right.

I've actually seen worse but this calc is either following some kind of standards in Hong Kong (unbeknownst to us) or it's just very poorly prepared...

 

[mpw]

90 might be depth of concrete minus rebar cover.

Thank you for your help, but I am little bit confused from what you said here.

I presume you are talking about the diagram at page 5 of the calculation sheet right?

What I understanding that Spreading area = (560+2x90)x(311+2x90) = 740x491mm^2 is going through in a Y-axis x X-axis direction

If you talking about 90 is derived from concrete slab minus rebar cover, then it is going into Z-axis direction, right?

That doesn't make sense how it will come out in squareminimeter???

 

[Andy Lin]

He is going 45 degree into the concrete to calculate the area. Kind of like calculating the perimeter of critical section when doing punching shear -- but instead of perimeter, it's area.

So a projected area if you will - in the plane of the rebars.