1 Topic by ah

  • ah
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  • Registered: 2013-02-26
  • Posts: 5

Topic: Modelling a bolt using reinforcement bars

Hi.
I am trying to model a fully tensioned bolt using a reinforcement bar and I will appreciate if you could let me know if the procedure is correct.
I have modelled the bolt head and the nut using solid elements and the bolt shank is modelled using a reinforcing bar connecting the mid height of the nuts to each other, passing through two plates. The pre-tension is applied at the first load step before applying any other forces.
Since the bolt, is not touching the inner surface of the hole, I have used a user defined reinforcement bond material with zero stress for the bar.
Is this correct?
Also, do bars in ATENA have any flexural stiffness? In other words, can they be used for modelling bending behaviour of bolts as well?
I have checked the stresses at the reinforcement bars after the first load step and I have noticed that the load in the bolt is less than the pre-stressing load applied to the bar. Any ideas why this is happening?
Many thanks.

Quote Post 1

  • dpryl
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  • Registered: 2007-07-13
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Re: Modelling a bolt using reinforcement bars

Hello, if the bar is only connected at the endpoints, the best way is to model it as Cable (using a nonsense bond law with zero strength would introduce numerical problems).

If you apply the pretensioning using Initial Strain calculated based on the elastic modulus of the bar, you may wish to add a load step with additional strain applied as correction for the losses due to the deformation of the surrounding structure. If you apply as Initial Stress, it should stay constant (corresponding to frequent post-tensioning to compensate for losses).

The bars only have axial stiffness, i.e., no bending nor shear. There are tricks some tricks (see ATENA Troubleshooting, 2.1.16 How can I take the bending and/or shear contribution of reinforcement bars into account?), however, they only work for embedded bars (which would be a problem for your bar, but maybe not for the heads or nuts).

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Quote Post 2