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Following situation: I need to mount a console holding a load to the edge of a 25cm concrete plate. I want you to check my reasoning. This is the situation: enter image description here

My thinking is: The load is 170kg, which amounts to 1.67 kN. The length of the cantilever is 600 mm. So the tension load on the upper two fasterners (of four, installed in square patterns) is a total of 1.67 kN * 600 mm / 150 mm = 6.69 kN.

Looking the specifications of a likely system, I see that 2 M10 fasteners at embedment depth 100mm offer me 2 * 8.7 kN tensile load, which contains decent margin of safety. The shear load per fastener is in the same range, there's 4 fasteners, so even considering 10 or 20 kg for the console (likely too much) this is ok.

I'm out of school too long. Is the above correct?

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You'd have to check for these factors.:

  • The fastener must penetrate into and fully develop its strength inside the steel cage tie bar or L shaped rebar inside the concrete which is a continuous part of its reinforcement. Concrete alone is susceptible to cracking under tension and is not reliable.

  • Dynamic load factor. A load of P, even if lowered gently onto a support has 2 to 3 times its weight impact factor. Because it needs to deforms the member to its deflected shape and beyond and back to equilibrium. So the load factor of 3 is advisable.

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  • $\begingroup$ regarding the first point: concrete coverage of rebar is 5.5cm (nominal), so should I "oversize" embedment length by that amount (Then I'd need 200 mm, according to the table)? Or just make sure the embedment is significantly longer than the coverage thickness? $\endgroup$ – mart Jun 18 at 15:45
  • $\begingroup$ @mart, yes you extend the anchor embedment by that amount, and your anchor should be strong enough to support the load as a cantilever beam, assuming the concrete cover is cracked. $\endgroup$ – kamran Jun 18 at 16:00

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