Composite (CFT) marine pile design to Eurocode4
Composite (CFT) marine pile design to Eurocode4
(OP)
i am currently working on the design of "concrete-filled steel circular marine piles". as i see most of the CFT research is on building columns but there is no design recommendation or implementation on marine piles.
in case of closed-ended pile driving, one can ensure that required bond strength could be achieved as interior surface of pile shaft is free from dust, oil, paint, organic materials and etc. (this is a similar case for also bored piles with pre-drilling or pre-augering). however, i sometimes encounter marine piles with open-ended because of need of socketing into bedrock and/or relatively larger piles in diameter (say, d/t>=60 and d>=60cm). i am also fine with the provisions in Eurocode4 to make use of them in composite marine pile design but i am not sure if any bond strength can be achieved in case of open-ended pile driving.
any input is appreciated.
in case of closed-ended pile driving, one can ensure that required bond strength could be achieved as interior surface of pile shaft is free from dust, oil, paint, organic materials and etc. (this is a similar case for also bored piles with pre-drilling or pre-augering). however, i sometimes encounter marine piles with open-ended because of need of socketing into bedrock and/or relatively larger piles in diameter (say, d/t>=60 and d>=60cm). i am also fine with the provisions in Eurocode4 to make use of them in composite marine pile design but i am not sure if any bond strength can be achieved in case of open-ended pile driving.
any input is appreciated.






RE: Composite (CFT) marine pile design to Eurocode4
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Composite (CFT) marine pile design to Eurocode4
RE: Composite (CFT) marine pile design to Eurocode4
From a lateral load standpoint, the concrete infill adds little or no EI to the section - usually less than five percent - so the presence of the concrete has more to do with corrosion protection and load transfer between the pile and cap than anything else. Axial capacity is different: the concrete infill can increase the effective bearing area of the pile, significantly increasing the pile capacity. However, special measures may need to be taken to assure the bearing capacity is achieved. This can include requiring that the soil plug be partially or fully removed before filling the pile completely with concrete.
Each case is unique; if you are designing a dock, loading platform or breasting platform then you should have a geotechnical engineer as a part of the design team. What does s/he say?
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Composite (CFT) marine pile design to Eurocode4
"Tests by Bridge on rectangular CFTs bent both uniaxially and biaxially showed that the concrete core only provides about 7.5% of the capacity in member under pure bending. Lu&Kennedy reported strength increases of order of 10-30% over rectangular hollow tubes, and they exhibited ductile failure modes" (Hajjar, 2000).
as to combined axial load and bending, behaviour of the beam-column is influenced by the ratios d/t, N/No (axial load ratio), and L/d. as axial compressive load is added to a member in pure bending, the contribution of concrete starts to increase, hence composite action of the section becomes significant and resulting in enhanced combined capacity.
i solved a numerical example to Eurocode4 and witnessed that member capacity (combined axial load and bending) of a composite column gets significantly higher compared to steel hollow section and relatively higher compared to R/C section with the same diameter and concrete class. this is the structural point of view. we are working on a "pile supported loading platform". in regard to geotechnical, we are advised to remove soil plug and employ "drill-and-drive" method to achieve a rock socket at the pile tip. piles will be completely in-filled with normal strength concrete. however, the question remains the same: (how) can a natural bond strength be achieved for an open-ended driven pile?
thanks for your help.
RE: Composite (CFT) marine pile design to Eurocode4
If the pile is completely filled with concrete, why the interest in bond strength between the concrete and steel? I'm not sure that I fully understand your question -
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Composite (CFT) marine pile design to Eurocode4
here are the following papers below, as per your request:
1)Concrete-filled steel tube columns under earthquake loads
J F Hajjar, Prog. Struct. Engng Mater. 2000; 2: 72–81
2)Bridge RQ. Concrete filled steel tubular columns. Report No R283. Sydney, Australia: School of Civil Engineering, University of Sydney. 1976.
3)Lu YQ & Kennedy DJL. The flexural behaviour of concrete-filled hollow structural sections. Canadian Journal of Civil Engineering 1994: 21(1):
111–130.
RE: Composite (CFT) marine pile design to Eurocode4
My gut says that the issue isn't as major as you think it is. Have you modeled the problem assuming the interior concrete is decoupled from the steel pile? What happens?
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