Thank you asixth
Could you specify the clause in Eurocode.
In Greece due to high seismicity we apply 1% for a depth nof 3 diameter piles below the pilecap or to a depth reuired by the calculations.. and at a depth of 3 times the pile diameter at the border of diffrent soil layers.
In all other lengths 0.5% is used.
Yes, actually eurocode specifies that the maximum reinforcement that most probably is located at the interface of thge pilecap and the pile must be placed at the interfcae of soil layers with markedly diifrent shaer deformability
I'm thinking cast in place piles. I have recently received a proposed design which only has reinforcement in the top half of the pile.
I have asked for the designers to justify this.
The project is in europe.
Dear Kieran,
Check which region in Europe, if it is Italy, Greece Romania e.t.c
which are bound to strong eartgquakes I would be very carefull.
Ask the designer for confinement reinforcement, regardless of the axiall load, the reinfocement is considerable.
The pile is tretad as a column by the designer i.e subjected to axial load, moments and shear forces in two directions.
Hence ask the designer why he is not supplying the minimum reinforcement for column.
I agree that it looks at least peculiar
Have you got any idea what design code is used?
I would appreciate you could inform me about the explanation the designer came up
The compressive force is taken by the concrete, not the 0.5% reinforcement. So if it is not required in the lower part, why do it? It just complicates placement of the concrete.
I believe it should be treated as a column, so whether needed or not, a minimum percentage of reinforcement as required by the relevant code,should be provided.
If the piles are not micro-piles that is if their diametar is 1.00/1.20m then the placement of reinforcement should not be a real problem.
In Greece due to earthquakes, concrete code requires that columns are reinforced with a minimum of 1% whether structurally required or not and a relevant minimum shear reinforcement.
Greek codes used to follow the German codes (DIN) altered ofcourse to take into account the seismic component.
The new German Standards Din Fachbericht 102~104 are relly close to the Eurocodes
However in piles that percentage in areas far from the formation of plastic hinges the percentage may be reduced to 0.5%
I have been looking at specs in EC 7 and EC 2 when referring to piles. EC 7 seems not to give any indication on minimum reinforcement.
EC 2, that I have checked in its EN 1992-1-1:2004 (E) release, addresses the minimum reinforcement in sections 7.3 when dealing with crack control (that can be dealt with in calculated or simplified ways) and as minimums to lay on specific kinds of structural members in 9.2, say, beams, slabs and columns. When not meeting the minimum for the type, the structural part is to be dealt with as per section 12, that deals with unreinforced concrete.
Then, for columns, (that we muse may be referred to when dealing with piles, since can have both flexure and compression/tension) the minimum and maximum reinforcement ratios are to be set per EC 2 in the national annexes to EC 2. In Spain that means that now the minimum geometrical ratios are to be checked by the code EHE 2008, that for columns, either in 400 or 500 MPa Fy reinforcing steels are set at 0.4%.
In short, there is a void in setting specific minimum reinforcement ratios in Eurocode for piles (since we are to refer to columns to find such); other thing is that the requirements of crack control need to be met, and really this could be the guide to decide if some steel is required as a minimum. By formula (7.1) of section 7.3.2 Minimum reinforcement areas in EC 2, since fct,eff is the mean value of the tensile strength of the concrete effective at the time when the cracks may first be expected to occur, and, by definition, this is a material property value, a short sighted or strict view on the matter is that by such formula some tensile reinforcement is always required to restrain crack formation, generically. This may not be the case if cracks are not "expected to occur" by the excess of significant strength respect characteristical solicitations per analysis. In my view this second option may be rationally argued, and so, the practice of not reinforcing some parts of piles may be countinued and still be compliant with Eurocodes.
Other thing is what the designer has as good practice, or what other codes may recommend. I can say that reinforcing only the 6 upper meters of piles has been common in Spain since the apparition of diverse sets of NTE codes (Normas Tecnológicas de la Edificación) dealing with different kinds of piles in the seventies; I can't say if such was the case before. Of course this practice should not be thought generally applicable to big size piles either in buildings or public infrastructures, or anywhere analysis demands reinforcement.
Do you have a piling code in Europe? The Australian Piling Code, AS2159, gives rules where reinforcement can be terminated or omitted altogether. This in simple terms is at a level where the bending and tension are found not to be significant.
I find myself in error when not finding in EC 2 a minimum reinforcement in piles; at least, for bored piles. Here in the attached jpg stands what said.
There is also it seems a pending errata that says:
In the clause 9.8.5.(3) replace:
“Bored piles with diameters not exceeding h1 should be provided with a minimum longitudinal reinforcement
area As bpmin.”
with the following:
“Bored piles with a diameter less than h1 should be provided with a minimum longitudinal reinforcement area As bpmin; this minimum applies also to reinforced bored piles with diameter larger than h1”
This of course precludes bored piles be compliant with only partial length reinforcement; and rare will be the non-bored piles that do not incorporate tensile strength (reinforcement if RC or PC) on the whole length. So the practice of partial length reinforcement is practically entirely dismissed by this clause.
Is there any indication in Eurocode 8 about the minimum percentage?
The Guidlines for the Earthquake Design of Bridges issued by the Greek Ministry of Infastructures stated the percentages of 0.5% and 1%.
Guess in the design I will make reference to the above code since the design is in Greece
Although I have the code I can not find a reference regarding the minimum percentage.
By the way I do not think the code can de downloaded for free. All standard authortities of Europe (BSI,Gerrman, Italian....) are selling them.
For the Actions, Reinforced Concrte and Earthquale Code with all parts (i.e Buildings,Bridges, Water Retaining Structure)the price I paid was 2000Euros.
The code can be printed only once and loaded as a pdf on one computer.
Any way Thanks
