Calculation of axial stability for towers
Thread Content
This post was last edited by FMSD on 2017-7-5 at 10:03. Question 1: In the stability calculations specified for steel chimneys, local stability of the cylinder is taken into account; why isn’t this consideration included in the specifications for towers? Question 2: For the wind and seismic loads specified in tower codes, why are no partial safety factors taken into account? Is it because the allowable stress for pressure vessels already takes into account a safety factor, so there is no need to consider a partial factor for the loads? We know that when calculating seismic and wind loads in general building structure design, sub-coefficients are taken into account. Article 5.4 of the Seismic Design Code GB 50011-2010 stipulates that the sub-coefficient for wind loads is 1.4 ； Wind load combination coefficient: 0 for general structures; 0.2 when wind load plays a controlling role ； The seismic load partial factor is taken as specified in Table 5.4.1; when only horizontal seismic loads are considered, the value of 1.3 is used ； (The combination factor specified in the tower code is 0.25, which is not very different from 0.2 specified in GB 50011-2010.) Question 3: The calculations related to wind-induced vibration in NB/T 47041-2014 also differ from those in GB 50009-2012; the former does not take into account wind-induced vibration in the windward direction, while the latter does.
Third question: when calculating the windward vibration of a tower, the main factor affecting it is the bending moment
The last edit to this post was made by letitbe on 2017-7-5 at 11:20. The second question is that building codes take into account not only cantilever beams such as those in towers
I know; the key question is why the tower code does not take this windward wind vibration into account?
If axial stability is to be considered, the height-to-diameter ratio needs to exceed 70, and very few towers can achieve this.
What is the basis for the height-to-diameter ratio you mentioned?
SEI has published a training manual that discusses this issue. It is derived from Euler’s formula
But it includes such a structure
Do you mean that if the height-to-diameter ratio is less than 70, axial stability does not need to be considered? If the radius-thickness ratio is between 500 and 800, is such a structure also not considered?
Could you take a screenshot of the content in the book? And which book is it?