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A B Malla General Sponsor
Joined: 26 Mar 2017 Posts: 13
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Posted: Thu Feb 13, 2020 8:36 am Post subject: Tower Base Plate |
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Dear all,
PFA, figure of base plate in one of the tower leg.
1)To my understanding, if we see it as base plate connected to one leg it behaves as fixed support. but, if we see it in over all tower, one leg may carry either axial tension or axial compression so, it behaves as pinned support.
so, it should be assigned as pinned support in STAAD, and should be designed for bending stress due to axial loads in leg. how far my understanding is correct?
2)In Leg splicing how much gap is feasible from fabrication point of view.
3)In splicing, if two leg members (say 8mm thk & 6mm thk) are getting connected, there is a gap of 2mm, can we provide 2mm packing plate or there is any other option.
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es_jayakumar General Sponsor
Joined: 24 Nov 2011 Posts: 1408 Location: Cochin
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Posted: Thu Feb 13, 2020 3:24 pm Post subject: |
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Er. Malla,
As the tower base-plate is tightly secured to the foundation by a number of foundation bolts, the real behaviour of the supports will be fixed (even if the bolt holes are slotted). However, there will be little error in analysing it, taking supports as hinged. As the external loads are assumed to act at the joints (nodes), the members will not develop significant BM in either case. In brief, you can analyse the support as either hinged or fixed or partially fixed, without much difference in the values of axial forces in members. The attached STAAD file is that of a tower design. You can check yourself, whether the axial forces in members change significantly when the support condition is switched between hinged and fixed.
You can provide packing plates in the case mentioned by you.
E S Jayakumar
Warning: Make sure you scan the downloaded attachment with updated antivirus tools before opening them. They may contain viruses. Use online scanners here and here to upload downloaded attachment to check for safety.
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A B Malla General Sponsor
Joined: 26 Mar 2017 Posts: 13
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Posted: Fri Feb 14, 2020 4:24 am Post subject: |
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Dear sir,
Thank you for your valuable response.
Yes there is no significant change in axial forces by switching support conditions. i presume that is because of global forces rather than local forces. Also, if we consider support condition as fixed, should we design leg member connecting to base plate for Moments?
Regards
A B Malla
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mallesh_ng General Sponsor
Joined: 27 Dec 2013 Posts: 45 Location: BENGALURU
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A B Malla General Sponsor
Joined: 26 Mar 2017 Posts: 13
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Posted: Fri Feb 14, 2020 9:23 am Post subject: |
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Thank you Er. Mallesh.
i was also thinking the same. your pictorial representation made it clear.
Regards ,
A B Malla
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