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cdous (Civil/Environmental) (OP)
28 Sep 11 5:49
Would appreciate if someone indicated the minimum precentage of reinforcement for piles demanded by eurocodes
asixth (Structural)
28 Sep 11 6:20
0.5% and 1.0% for the extension of pile above ground.
cdous (Civil/Environmental) (OP)
28 Sep 11 6:30
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.
 
kieran1 (Structural)
28 Sep 11 6:54
Do concrete piles need to be reinforced throughout the depth of embedment?

Kieran
 

cdous (Civil/Environmental) (OP)
28 Sep 11 7:15
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
hokie66 (Structural)
28 Sep 11 7:29
What kind of piles?  Precast driven or cast in place?
kieran1 (Structural)
28 Sep 11 7:34
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.

Kieran
 

cdous (Civil/Environmental) (OP)
28 Sep 11 7:50
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.
 
kieran1 (Structural)
28 Sep 11 7:54
Thanks cdous.

The piling is not in an earthquake region. But why bore a 10m pile and only reinforce the top 5m. Just doesn't look right.

Kieran
 

cdous (Civil/Environmental) (OP)
28 Sep 11 8:26
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
hokie66 (Structural)
28 Sep 11 16:26
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.
cdous (Civil/Environmental) (OP)
29 Sep 11 3:51
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%
Helpful Member!(2)  ishvaaag (Structural)
29 Sep 11 6:14
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.
hokie66 (Structural)
29 Sep 11 7:03
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.
ishvaaag (Structural)
29 Sep 11 9:27
What follows refers to Spain,

The only case where I know precise detail was given about pile details and design in Spain were the non-mandatory NTE

NTE CPE (1978) Encepados (Pile Caps)
NTE CPI (1978) In Situ Piles
NTE CPP (1978) Prefabricated Piles

Other than that the UNE codes related to special geotechnical works

UNE-EN 1536:2000: Ejecución de trabajos especiales de geotecnia. Pilotes perforados.
UNE-EN 12063:2000: Ejecución de trabajos geotécnicos especiales. Tablestacas.
UNE-EN 12699:2001: Realización de trabajos geotécnicos especiales. Pilotes de desplazamiento.

These must have close ISO correspondent codes. Since not referenced in basic codes, they are neither mandatory.

A new one is mandatory, since referenced in EHE 2008
UNE-EN 12794:2006. Productos prefabricados de hormigón. Pilotes de cimentación

The last I don't have. The others seem not to make allusion to minimum reinforcement.

There maybe other codes for offshore structures.

 
ishvaaag (Structural)
29 Sep 11 15:23
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"

 
ishvaaag (Structural)
29 Sep 11 15:27
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.
cdous (Civil/Environmental) (OP)
30 Sep 11 3:17
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
hokie66 (Structural)
30 Sep 11 3:21
Why don't you look yourself?  I googled Eurocode 8, and it looks like it is a free download.
cdous (Civil/Environmental) (OP)
30 Sep 11 3:38
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  
hokie66 (Structural)
30 Sep 11 7:04
I downloaded it, but maybe the site is illegal, so I won't go further.
dtoli (Structural)
11 Oct 11 11:52
Buildings: [5.8.4 EN 1998-1]
Bridges  : [6.4.2. EN 1998-2]
To these paragraphs in certain areas  (i. below pilecup and at soil strata changes with stiffness module ratio more than 6) you should design as  potential plastic hinge regions. That means  that in buildings you should apply (DCM) the paragraph [5.4.3.2.2 EN 1998-1] that requires minimum longitudinal reinforcement 1% and maximum 4%. Also design for critical regions (i.e. stirrups distances, volumetric ratio etc).
 

URL: www.diolkos-eng.gr

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