Rotational spring support: Incorrect moment?

Anonymous — Thu, 25 Jan 2018 09:39:58 GMT

I am modelling a simplified 2D cantilever beam with a spring support. The cantilever base support connection would have only partial fixity of 80% of the fully fixed moment (equates to 700 kNm capacity in ULS).

My aim is to determine what would be the resulting deflection. I am doing this by calibrating the support moment to match the reduced connection stiffness. I have been testing different Ry stiffness values in the Supports dialog so that the resulting base moment matches the 700 kNm reduced value.

However, the moment does not change, regardless of the different Ry values applied. I have noted that the deflection value does change, but I would not know if it correct if I do not know the corresponding base moment (I have calibrated the initial spring value to match approximately 1 degree rotation at the support). Could someone advise on how I could determine this?

I have uploaded the file in the attachment and added a screenshot of the model below.

Regards,

Davis

Re: Rotational spring support: Incorrect moment?

Artur.Kosakowski — Thu, 25 Jan 2018 09:53:35 GMT

Hi @Anonymous

If you have only one support to carry the applied load and you tell that it handles only 80% of the load what is supposed to happen with the 'missing' 20% bearing in mind the load is still the same?

This would work if you had two supports and then if you apply the reduction in rotational stiffness to one of them it will 'carry' less bending than for two fixed supports whereas the other more.

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Rotational spring support: Incorrect moment?

Re: Rotational spring support: Incorrect moment?