The foundation bolts of the tower are buried too shallowly
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The tower has a diameter of 1600 mm and a height of 16,000 mm. The originally designed foundation bolts were 12 pieces of M36 size, but 12 pieces of M30 size foundation bolts were installed on site. After verification, it was found that when M30 foundation bolts are used, there is only a margin of 0.5 mm in terms of root diameter; it is not clear whether this is safe. Are there any other solutions?
There’s no other choice; based on conventional calculations, it’s clear that the result is not safe, so a safety assessment must be conducted. If safety cannot indeed be guaranteed, then the foundation will have to be demolished and rebuilt from scratch!
I wonder if you took the horizontal thrust exerted by the pipes into account when doing the calculations. If that thrust is included, the calculations will definitely not yield a valid result
This post was last edited by dennyg on 2018-6-14 21:21. I’ve seen cases where an additional layer of chemical anchor bolts is used on the outside… It was part of a certain project; I saw a foundation diagram that seemed quite strange. Inside are the anchor bolts, and then an outer foundation is added to enclose the base; furthermore, a layer of chemical-reinforced rebar is included within this foundation. I asked why, and the structure said that the starting condition was reduced, only to find later that it wasn’t enough. That's what was done
If the corrosion allowance is removed from the bolts and factors such as pipe stress are taken into account, there is still a remaining margin of 0.5 mm; mathematically this is sufficient for use, after all, the stress conditions on foundation bolts are different from those on flange fasteners.
If the calculation shows a margin of 0.5mm, it is completely sufficient and safe as well. Since the tower standards use the Wöhmann method for calculating the foot bolts, only the area of the foot bolts on the side of the neutral axis is taken into account; in reality, the area provided by the foot bolts is greater. The algorithm itself has a large margin of flexibility. But the problem now is that the drawings specify M36, while you have installed M30. If the design office doesn’t redo the calculations and issue a change order for you, there’s nothing that can be done.
There’s no other choice; I’ll have to start over from the basics.
Demolishing a foundation is much more difficult than building one. When calculating the thread pitch for the anchor bolts in SW6 soil, a corrosion allowance is taken into account (the program automatically includes a 2mm corrosion allowance). I believe that M30 can be used safely; this is for reference only.
This is quite difficult to handle, as it involves too many aspects