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The determination of the anchorage length of the holding down bolts is based on Ref. [6].
The required anchorage length lb,net is calculated from:
with
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the diameter of the holding down bolt. |
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fyd |
the design yield strength of the holding down bolt. This is determined as follows :
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fu |
the ultimate tensile strength of the anchor |
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γMb |
the partial safety factor for a bolted connection. (= 1.25) |
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fbd |
the design value for the ultimate bond stress. fbd is dependent on the bond condition, which normally is good for a column base and also dependent of the type of holding down bolts. (plain or high bond bars)The bond condition and the type of bars can be set in the concrete data dialog box. |
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lb |
the basic anchorage length.
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αa is dependent on the anchorage method.
=1 for straight bars.
=0.7 for curved bars.
As,req is the required tensile stress area of the anchor
with
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Ft,bolt |
the maximum tensile force in the anchors. (due to NRd,t or MRd) |
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γMb |
the partial safety factor for a bolted connection. (= 1.25) |
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fu |
the ultimate tensile strength of the anchor |
As,prov is the provided tensile stress area of the anchor
lb,min is the minimum anchorage length
lb,min is the maximum of 0.3 lb , 10
The tensile force in the anchor can be calculated using the actual internal forces. This calculation is based on the regulations given in ref.[24], chapter 6.4.1.
This setting may be changed in the Connection Setup.
Consider the following configuration :
Moment equilibrium gives :
Ft is the tensile force for each anchor row in the tension zone, M and N are the actual internal forces.
When Ft<0, all anchors are in compression. The minimum anchor length is calculated.
When Ft>0.0, the value for Ft,bolt is calculated.
The anchor rows in the tensile zone, are those anchor rows where hi > h/2 is valid.
The design of a circular plate is based on Ref. [7]
The allowable tensile force Nj in 1 anchorage is given by:
with
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v |
the smallest of l and d1. See figure. |
By means of this formula r, the radius of the circular plate is determined.
The iterative process is started using 2,5 times the anchor diameter as an initial value for r.
The thickness t is given by
with
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E |
Modulus of elasticity for anchorage. |
