Goh_EC7_Pile_CPG_July2013.pdf

CPG In-House Course onPile design (EC7 and SS EN 1997-1:2010

Singapore National Annex to Eurocode 7)- July 2013

A/P Anthony GohNanyang Technological University

E il t h@ t dEmail: [email protected]

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References

Bauduin, C.M. (2001). Design procedure according to Eurocode 7 andanalysis of the test results. Proc. Symposium on Screw Piles Installationand design in stiff clay, Brussels, Balkema, pp.275-303.

Bond, A. and Harris, A. (2008). Decoding Eurocode 7. Taylor & Francis.f C G ( ) Dept of Communities and Local Government, UK (2006). A designers

simple guide to BS EN 1997.

Driscoll R., Scott, P. and Powell J. (2008). EC7 implications for UK Driscoll R., Scott, P. and Powell J. (2008). EC7 implications for UKpractice. Eurocode 7 Geotechnical design. CIRIA C641.

Frank, R., Bauduin C., Driscoll, R., Kawadas, M., Krebs Ovesen, N., Orr, T.d S h B (2004) D i G id t EN 1997 1 E d 7and Schuppener, B. (2004). Designers Guide to EN 1997-1 Eurocode 7:

Geotechnical design General rules. Thomas Telford.

Simpson B. and Driscoll, R. (1998) Eurocode 7 a commentary. BRE.p , ( ) y Tomlinson M. and Woodward, J. (2008). Pile design and constructionpractice. 5th edition. Taylor & Francis.

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SINGAPORENATIONALANNEX

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NAtoSSEN19971:2010

SINGAPORENATIONALANNEXS G O ONAtoSSEN19971:2010SingaporeNationalAnnextoEurocode7:GeotechnicaldesignP t 1 G l l

NA 2 Nationally Determined Parameters

Part1:Generalrules

NA.2 Nationally Determined ParametersAs indicated in Table NA.1, only Design Approach 1 is to b d i Sibe used in Singapore.

The values given in the Tables in Annex A of this National Annex replace the recommended values in Annex A of SS EN 1997-1 : 2010.

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For example, Table A.NA.7 replaces Table A.7

Resistance Symbol Set

Table A.NA.7 Partial resistance factors (R) for bored piles for the STR and GEO limit states

Resistance Symbol SetR1 R4 without explicit

verification of SLSA)R4 with explicit

verification of SLSA)

Base b 1.0 2.0 1.7Shaft (compression)

s 1.0 1.6 1.4T t l/C bi d 1 0 2 0 1 7Total/Combined (compression)

t 1.0 2.0 1.7Shaft in tension s;t 1.0 2.0 1.7A) The lower values in R4 may be adopted (a) if serviceability is verified by load tests (preliminary and/or working)

carried out on more than 1% of the constructed piles to loads not less than 1.5 times the representative load forwhich they are designed, or (b) if settlement is explicitly predicted by a means no less reliable than in (a), or (c)if settlement at the serviceability limit state is of no concern.

SS NA permits the use of different R4 values dependingon the verification of SLS

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on the verification of SLS

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For example, Table A.NA.7 replaces Table A.7

Table A.7 Partial resistance factors (R) for bored piles

Resistance Symbol SetR1 R4R1 R4

Base b 1.25 1.6Shaft (compression)

s 1.0 1.3 Total/Combined (compression)

t 1.15 1.5(compression)Shaft in tension s;t 1.25 1.6

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DefinitionsActions on the foundations (Clause 2.4.2(4)) Earth and groundwater pressuresg p Weight of soil, rock and water Dead and imposed loading from structure Dead and imposed loading from structure Imposed loading from ground movements (eg. swelling,

shrinkage, down-drag)g , g)

Ground properties (Clause 2.4.3) from field or laboratory tests (directly or by correlation from field or laboratory tests (directly or by correlation,

theory or empiricism) Takes into account effects of time, stress level and Takes into account effects of time, stress level and

deformation etc

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Definitions

Geometrical data (Clause 2.4.4(1)P) Include slope of the ground surface, groundwaterp g , g

levels and structural dimensions

Characteristic values of Geotechnical parameters(Clause 2.4.5.2) Selected from the a ailable information (eg SI report) Selected from the available information (eg. SI report) Based on a cautious estimate of the data made within

the zone influenced by stresses transmitted to thethe zone influenced by stresses transmitted to the ground

Less than most probable values (most situations) Higher than most probable where higher values have an

unfavourable effect on the foundation behaviour (eg. down drag)

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Definitions

Ultimate Limit States (Clause 2.4.7.1) for foundations STR: internal failure or excessive deformation of the STR: internal failure or excessive deformation of the

structure

GEO f il i d f ti f th d GEO: failure or excessive deformation of the ground

Model Factors (Clause 2.4.7.1(6))

M d l f t b li d t th d i l fModel factors may be applied to the design value of aresistance or the effect of an action to ensure that theresults of the design calculation model are either accurateresults of the design calculation model are either accurateor err on the safe side.

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Design Approach 1 (Clause 2.4.7.3.4.2(1)P)STR limit state failure or excessive deformation of the

structureGEO limit state failure or excessive ground deformation

Ensure that:

Design effects of actions Ed design resistance Rd

Design Approach 1

C bi ti 1 A1 + M1 + R1Combination 1: A1 + M1 + R1Combination 2: A2 + M2 + R1

A = action; M = material properties; R = ground resistance

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Design Approach 1 (Clause 2.4.7.3.4.2(1)P)

Combination 1: A1 + M1 + R1


Clause 2.4.7.3.4.2(2)P Note 2 If it is obvious thatone combination governs the design, it is notnecessary to perform full calculations for the othercombination.

Often Combination 2 will govern the geotechnicalOften Combination 2 will govern the geotechnicalsizing and Combination 1 will govern the structuraldesign


design.

GEO and STR ULS calculations (Design Approach 1) Clause 2.4.7.3.2 and 2.4.7.3.3Clause 2.4.7.3.2 and 2.4.7.3.3

Ed RdE = design value of the effects of all the actionsEd = design value of the effects of all the actions{ }dMkrepFd aXFEE ;/; =R = design al e of the corresponding gro nd and/or str ct re{ }dMkrepFd aXFRR ;/; =Rd = design value of the corresponding ground and/or structure

{ } RdkrepFd aXFRR = /;;For piles and anchorages Frep Representativevalueofanactionrep pF PartialfactorforanactionXk Characteristicvalueofamaterial (ground)propertyM Partialfactorforthematerialpropertyad DesignvalueofageometricalpropertyR Partialfactorforthe resistanceoftheground

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R a t a acto o t e es sta ce o t e g ou d

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Serviceability Limit State (Clause 2.4.8) y ( ) Partial factors normally taken as 1.0 (Clause2.4.8(2))( ))

Verification for serviceability limit states shallyrequire that

Ed Cd

where Cd = the limiting design value of the relevant

d d

d g gserviceability criterion (Clause 2.4.8(1)P)

or be done through the method given in 2.4.8(4).

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2 4 8(4) It may be verified that a sufficiently low2.4.8(4). It may be verified that a sufficiently lowfraction of the ground strength is mobilised to keepdeformations within the required serviceability limitsdeformations within the required serviceability limits,provided this simplified approach is restricted todesign situations where:design situations where: a value of the deformation is not required to checkth i bilit li it t tthe serviceability limit state; established comparable experience exists withsimilar ground, structures and application method.

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Limiting values of movements of foundations (Clause 2.4.9(4)P Note)(Clause 2.4.9(4)P Note) In the absence of specified limiting values, Annex H

(informative) may be used.

Annex H For normal structures with isolated foundations,total settlements of up to 50 mm are often acceptable.p pAlso provides guidelines for Maximum relative rotation.

Annex F Sample methods for settlement evaluation (basedAnnex F Sample methods for settlement evaluation (based on elasticity theory)

7.6.4. Vertical displacements of pile foundations (serviceability of supported structures) 7 6 4 1 NOTE For piles bearing in medium to dense soils and for7.6.4.1 NOTE For piles bearing in medium-to-dense soils and fortension piles, the safety requirements for the ultimate limit statedesign are normally sufficient to prevent a serviceability limit state

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in the supported structure.

Pile Foundation Design (Design Approach 1)

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7.2 Limit states

(1)P The following limit states shall be considered ..... :

loss of overall stability; bearing resistance failure of the pile foundation; uplift or insufficient tensile resistance of the pile foundation; failure in the ground due to transverse loading of the pile foundation; structural failure of the pile in compression, tension, bending, buckling

or shear;or shear; combined failure in the ground and in the pile foundation; combined failure in the ground and in the structure; excessive settlement; excessive settlement; excessive heave; excessive lateral movement;

unacceptable vibrations unacceptable vibrations.

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7.3.1 Actions and design situations Axial loading Transverse (horizontal) loading( ) g

7.3.2 Actions due to ground displacement lid ti ( ti ki f i ti ) consolidation (negative skin friction) swelling or heave (tension pile) lateral loading from adjacent surcharge or embankment lateral loading from adjacent surcharge or embankment

Analysis of Geotechnical action (Clause 7.3.2.1(3)P):y ( ( ) ) pile-soil interaction analysis (t-z or p-y analysis); or upper-bound force exerted on the pile by the ground

t i l l t d d t t d timovement is calculated and treated as an action

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Clause 2.4.7.3.4.2(2)P


Combination 2: A2 + (M1 or M2) + R4

In combination 2, set M1 is used for calculating resistancesof piles (or anchors) and set M2 for calculating

nfa o rable actions on piles eg o ing to negati e skinunfavourable actions on piles eg. owing to negative skinfriction

Clause 2.4.7.3.4.2 (2) Note 2 If it is obvious that onecombination governs the design, it is not necessary to

f f ll l l ti f th th bi ti

A = action; M = material properties; R = ground resistance

perform full calculations for the other combination.

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7.4.1 Design methods g

(1)P The design shall be based on one of the following approaches:

the results of static load tests, which have been demonstrated, bymeans of calculations or otherwise, to be consistent with other relevantexperience;experience;

empirical or analytical calculation methods whose validity has beendemonstrated by static load tests in comparable situations;demonstrated by static load tests in comparable situations;

the results of dynamic load tests whose validity has beendemonstrated by static load tests in comparable situations;demonstrated by static load tests in comparable situations;

the observed performance of a comparable pile foundation, providedh hi h i d b h l f i i i i dthat this approach is supported by the results of site investigation and

ground testing.


Design methods for pile foundations (Clause 7.4.1(P))

Method Comments

Staticloadtests# Validity mustbedemonstratedbycalculations orothermeanstobeconsistentwithotherrelevantexperiences.

Empiricaloranalyticalcalculations

Validity mustbedemonstratedbystaticloadtestsincomparable situationscalculations comparablesituations.

Dynamic impact tests# Validitymustbedemonstratedbystaticloadtestsincomparablesituations.p

Piledrivingformulaeorwaveequationanalysis#

Validity mustbedemonstratedbystaticloadtestsincomparablesituations, andgroundstratificationhasbeendetermineddetermined.

Observation Observedperformanceofcomparablepilefoundation;mustbesupportedbyresultsofSI andgroundtesting.

# Usually applies to trial (preliminary) piles and theresults of tests on these piles are used to design the

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results of tests on these piles are used to design theworking piles.

7 4 1(3) Static load tests may be carried out on trial piles installed for7.4.1(3) Static load tests may be carried out on trial piles, installed for test purposes only, before the design is finalised, or on working piles, which form part of the foundation.

Trial piles (installed for test purposes only, before thedesign is finalised); preliminary piledesign is finalised); preliminary pile.

Working piles (which form part of the permanentfoundation works); Test load must be at least equal); qto the design load (Clause 7.5.2.3(2)P).

UK experience Most contracts tests on trial piles are impractical asthere is insufficient lead time between the main piling works and the testprogrammes. Preliminary tests are seldom carried out on piles withp g y psimilar widths and lengths, which makes it difficult to derive a sensiblemean test result. In many tests, the ultimate load is obtained fromextrapolation of the load-displacement curve, adding further to the


extrapolation of the load displacement curve, adding further to theuncertainty in any calculated mean (Bond and Harris, 2008).

7.5 Pile load tests

7.5.1(1)P Pile load tests shall be carried out in the following situations:

when using a type of pile or installation method for which there is no when using a type of pile or installation method for which there is nocomparable experience;

when the piles have not been tested under comparable soil andwhen the piles have not been tested under comparable soil andloading conditions;

when the piles will be subject to loading for which theory andexperience do not provide sufficient confidence in the design. The piletesting procedure shall then provide loading similar to the anticipatedloading;g;

when observations during the process of installation indicate pilebehaviour that deviates strongly and unfavourably from the behaviour

i i d h b i f h i i i i i d hanticipated on the basis of the site investigation or experience, and whenadditional ground investigations do not clarify the reasons for thisdeviation.


(2) Pile load tests may be used to:

assess the suitability of the construction method; assess the suitability of the construction method;

determine the response of a representative pile and thesurrounding ground to load both in terms of settlement and limit load;surrounding ground to load, both in terms of settlement and limit load;

to allow judgement of the overall pile foundation.

Clause 7.5.1(4)P and (5)P) If one pile load test is carried out located where the

most ad erse gro nd conditions are belie ed tomost adverse ground conditions are believed to occur. If this is not possible, an allowance shall bemade when deriving the characteristic value of themade when deriving the characteristic value of the compressive resistance.

If more than one pile load test is carried out locations must be representative of the site of the pilefoundation and one of the test piles shall be locatedwhere the most adverse ground conditions are


where the most adverse ground conditions arebelieved to occur.

7.5.2 Static load tests

7.5.2.1 Loading procedure (1)P Measurements during static load tests must allow (1)P Measurements during static load tests must allow

conclusions about deformation, creep and rebound ofthe piled foundation. ...the piled foundation. ... Trial piles measurements must be able to draw conclusions# about the ultimate failure load.

(4)Tensile pile test should be carried out to failure (as brittle failure can occur).

# However, it should be understood that it is not alwaysnecessary to bring trial piles to failure: the common practicenecessary to bring trial piles to failure: the common practiceof deriving the ultimate failure load by extrapolating theload-displacement curve can be used. (Frank et al. 2004)

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load displacement curve can be used. (Frank et al. 2004)

7.5.2.2 Trial piles(1)P The number of trial piles required to verify the design shall depend on thefollowing: the ground conditions and their variability across the site; the Geotechnical Category of the structure, if appropriate; previous documented evidence of the performance of the same type of pile insimilar ground conditions; the total number and types of pile in the foundation design.

(2)P The ground conditions at the test site shall be investigated thoroughly. Thed th f b i fi ld t t h ll b ffi i t t t i th t f th ddepth of borings or field tests shall be sufficient to ascertain the nature of the groundboth around and beneath the pile tip. All strata likely to contribute significantly to pilebehaviour shall be investigated.

(3)P The method used for the installation of the trial piles shall be fully documentedin accordance with 7.9.


7.5.2.3 Working Pile(2)P Test load must be at least equal to the design load for the foundation(2)P Test load must be at least equal to the design load for the foundation.

7.5.3 Dynamic load tests

(1)Dynamic load tests may be used to estimate the compressive(1)Dynamic load tests may be used to estimate the compressiveresistance provided an adequate site investigation has been carried outand the method has been calibrated against static load tests on the samet f il f i il l th d ti d i bl iltype of pile, of similar length and cross-section, and in comparable soilconditions, (see 7.6.2.4 to 7.6.2.6).

(2)P If more than one type of dynamic test is used, the results of differenttypes of dynamic test shall always be considered in relation to each other.

(3) Dynamic load tests may also be used as an indicator of theconsistency of the piles and to detect weak piles.


7.5.4 Load test report

(1)P It shall be specified that a factual report shall be written for all loadtests. Where appropriate, this report shall include:

a description of the site; a description of the site; the ground conditions with reference to ground investigations; the pile type;

d i ti f th il i t ll ti d f bl t d description of the pile installation and of any problems encounteredduring the works;

a description of the loading and measuring apparatus and the reactionsystem;

calibration documents for the load cells, the jacks and the gauges; the installation records of the test piles;p ; photographic records of the pile and the test site; test results in numerical form; time-displacement plots for each applied load when a step loadingtime displacement plots for each applied load when a step loading

procedure is used; the measured load-displacement behaviour;

reasons for any departures from the above requirements


reasons for any departures from the above requirements .

Limit states (axially loaded piles) Clause 7.6.1.1(1)P( y p ) ( ) ULS of compressive or tensile failure of a single pile ULS of compressive or tensile failure of the pile ULS of compressive or tensile failure of the pile

foundation as a whole

ULS of collapse or severe damage to a supportedstructure caused by excessive displacement orstructure caused by excessive displacement or

differential displacements of the pile foundation

SLS in the supported structure caused by displacementof the pilesp

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Ultimate compression limit state (Clause 7.6.1.1(3)) It is often difficult to define an ultimate limit state from a load settlement plot. Settlement of the pile head = 10% of pile base diameter is used as the failure criterionpile base diameter is used as the failure criterion.

Serviceability Limit State (Clause 2.4.8(2)) Partial factors normally taken as 1.0

Serviceability of supported structure Clause 7 6 4 1 (2) Note- Clause 7.6.4.1 (2) Note

For piles bearing in medium-to-dense soils and for tensionpiles, the safety requirements for the ultimate limit statepiles, the safety requirements for the ultimate limit statedesign are normally sufficient to prevent a serviceability limitstate in the supported structure.

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7.6.2 Compressive ground resistance

7.6.2.1 General(1)P To demonstrate that the pile foundation will support the design load

i h d f i i f il h f ll i i liwith adequate safety against compressive failure, the following inequality shall be satisfied for all ultimate limit state load cases and load combinations:

Fc;d Rc;d

Fc;d = design axial compression load on a pileor a group of piles

Rc;d = compressive resistance


(3)P For piles in groups, two failure mechanisms shall be(3)P For piles in groups, two failure mechanisms shall betaken into account: compressive resistance failure of the piles individually; compressive resistance failure of the piles and the soilcontained between them acting as a block.

The design resistance shall be taken as the lower valuecaused by these two mechanisms.caused by these two mechanisms.

(4) The compressive resistance of the pile group acting asa block may be calculated by treating the block as a singlepile of large diameter.


(5)P The stiffness and strength of the structure connectingthe piles in the group shall be considered when deriving thethe piles in the group shall be considered when deriving thedesign resistance of the foundation.

(6) If the piles support a stiff structure, advantage may betaken of the ability of the structure to redistribute loadbetween the piles. A limit state will occur only if a significantnumber of piles fail together; therefore a failure modeinvolving only one pile need not be consideredinvolving only one pile need not be considered.

(7) If the piles support a flexible structure, it should be(7) If the piles support a flexible structure, it should beassumed that the compressive resistance of the weakestpile governs the occurrence of a limit state.


(8) Special attention should be given to possible failure ofedge piles caused by inclined or eccentric loads from theedge piles caused by inclined or eccentric loads from thesupported structure.

(9)P If the layer in which the piles bear overlies a layer ofweak soil, the effect of the weak layer on the compressiveresistance of the foundation shall be considered.

(10)P The strength of a zone of ground above and below(10)P The strength of a zone of ground above and belowthe pile base shall be taken into account when calculatingthe pile base resistance.the pile base resistance.

NOTE This zone may extend several diameters above andbelow the pile base. Any weak ground in this zone has arelatively large influence on the base resistance.


(11) Punching failure should be considered if weak ground ispresent at a depth of less than 4 times the base diameterpresent at a depth of less than 4 times the base diameterbelow the base of the pile.

(12)P Where the pile base diameter exceeds the shaftdiameter, the possible adverse effect shall be considered.

(13) For open-ended driven tube or box-section piles withopenings of more than 500 mm in any direction and withoutopenings of more than 500 mm in any direction, and withoutspecial devices inside the pile to induce plugging, the baseresistance should be limited to the smaller of:resistance should be limited to the smaller of:

the shearing resistance between the soil plug and theinside face of the pile;

the base resistance derived using the cross-sectional areaof the base


of the base.

Compressive Ground Resistance (Clause 7.6.2)

Fc;d Rc;dFc;d = design axial compression load on a pile

or a group of pilesg p pRc;d = compressive resistance

Fc;d should include the weight of the pile.Weight of piles is considered as permanent action.Rc;d should include the overburden pressure of the soil at the foundation basefoundation base.However, these two items may be disregarded if theycancel approximately.

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pp y

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They may not cancel if: (a) downdrag is significant, (b) they y ( ) g g ( )soil is very light, or (c) the pile extends above the groundsurface. (Clause 7.6.2.1(2))

For structures having sufficient stiffness and strength totransfer loads from weak to strong piles a reductiontransfer loads from weak to strong piles, a reductionfactor of 1.1 may be introduced. Clauses 7.6.2.2(9) and7.6.2.3(7). See Tables A.NA.9 and A.NA.10.( )

Pile base resistance shall take into account the strength

See Clause 7 8 for Structural design of piles

above and below the pile base. Clauses 7.6.2.1(9) to (11).

See Clause 7.8 for Structural design of piles

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Rc;d = compressive resistance, shall be derived either from:

k;bk;sd;c

RRR += or t

k;bk;s

t

k;td;c

RRRR

+==P

bs tt Clause 7.6.2.2(14)

Partial factor on shaft resistanceRefer to Tables A.NA.6, 7 and 8

WRs

s Partialfactoronshaftresistanceb Partial factoronbaseresistance Partial factor on total characteristic

R

t PartialfactorontotalcharacteristicresistanceRt;k

Th l f i i ll d h d i iRb The left equation is normally used when designingby calculation. The right equation is used whenthe shaft and base components cannot be


determined separately.

Rc;d = compressive resistance

k;bk;sd;c

RRR += or t

k;bk;s

t

k;td;c

RRRR

+==P

bs tt

The differences of the partial factor valuesbetween driven, bored and CFA piles is mainly

WRs

, p yrelated to the increasing probability of unexpectedeffects during pile installation adversely affectingthe pile bearing capacity (Bauduin 2001)

R

the pile bearing capacity (Bauduin 2001).

SS NA permits the use of different R4l d di th ifi ti fRb values depending on the verification of

SLS (Tables A.NA.6 to 8)


Table A.NA.6 Partial resistance factors (R) for driven piles for the STR and GEO limit states

Resistance Symbol SetR1 R4 without

explicit ifi ti f

R4 with explicit verification of

SLS A)verification of SLS A)

SLS A)

Base b 1.0 1.7 1.5Shaft (compression) 1 0 1 5 1 3Shaft (compression) s 1.0 1.5 1.3Total/Combined (compression)

t 1.0 1.7 1.5Shaft in tension s;t 1.0 2.0 1.7A) The lower values in R4 may be adopted (a) if serviceability is verified by load tests (preliminary

and/or working) carried out on more than 1% of the constructed piles to loads not less than 1.5ti th t ti l d f hi h th d i d (b) if ttl t i li itltimes the representative load for which they are designed, or (b) if settlement is explicitlypredicted by a means no less reliable than in (a), or (c) if settlement at the serviceability limitstate is of no concern.

SS NA permits the use of different R4 values depending on the verification of SLS With no testing (relying solely on calculation), a higher level of reliability is needed in the calculations.

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s eeded t e ca cu at o s

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Table A NA 7 Partial resistance factors ( ) for bored piles for the STR

Resistance Symbol Set

Table A.NA.7 Partial resistance factors (R) for bored piles for the STR and GEO limit states

Resistance Symbol SetR1 R4 without explicit

verification of SLSA)R4 with explicit

verification of SLSA)

Base b 1.0 2.0 1.7Shaft (compression)

s 1.0 1.6 1.4Total/Combined (compression)

t 1.0 2.0 1.7Shaft in tension s;t 1.0 2.0 1.7A) The lower values in R4 may be adopted (a) if serviceability is verified by load tests (preliminary and/or working)

carried out on more than 1% of the constructed piles to loads not less than 1.5 times the representative load forwhich they are designed, or (b) if settlement is explicitly predicted by a means no less reliable than in (a), or (c)if settlement at the serviceability limit state is of no concern.y

SS NA permits the use of different R4 values depending on the verification of SLS

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Table A.NA.8 Partial resistance factors (R) for continuous flight auger CFA piles for the STR and GEO limit states

Resistance Symbol SetR1 R4 without explicit R4 with explicit

p

pverification of SLS A)

pverification of SLS A)

Base b 1.0 2.0 1.7Shaft 1 0 1 6 1 4Shaft (compression)

s 1.0 1.6 1.4Total/Combined (compression)

t 1.0 2.0 1.7Shaft in tension s,t 1.0 2.0 1.7A) The lower values in R4 may be adopted (a) if serviceability is verified by load tests

(preliminary and/or working) carried out on more than 1% of the constructed piles to loads not(preliminary and/or working) carried out on more than 1% of the constructed piles to loads notless than 1.5 times the representative load for which they are designed, or (b) if settlement isexplicitly predicted by a means no less reliable than in (a), or (c) if settlement at theserviceability limit state is of no concern.

SS NA permits the use of different R4 values depending on the verification

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SS NA permits the use of different R4 values depending on the verification of SLS

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Draft Malaysian Standard (2011)( )


Summary of partial factors (NA to SS EN 1997-1:2010)

Combination 1 Combination 2Without explicit

verification of SLS A)With explicit

verification of SLS A)

A1 M1 R1 A2 M1 R4 A2 M1 R4Action Permanent Unfav 1.35 1.00 1.00

Fav 1.00 1.00 1.00Variable Unfav 1.50 1.30 1.30

Soil Tan 1.00 1.00 1.00c 1.00 1.00 1.00cu 1.00 1.00 1.00Unit wt. 1.00 1.00 1.00

Driven Piles Base 1.00 1.70 1.50Shaft (comp) 1.00 1.50 1.30Total 1.00 1.70 1.50

Bored Piles & CFA

Base 1.00 2.00 1.70& CFA Shaft (comp) 1.00 1.60 1.40

Total (comp) 1.00 2.00 1.70A) The lower values in R4 may be adopted (a) if serviceability is verified by load tests (preliminary and/or working) carried out onmore than 1% of the constructed piles to loads not less than 1.5 times the representative load for which they are designed, or (b) if

44

settlement is explicitly predicted by a means no less reliable than in (a), or (c) if settlement at the serviceability limit state is of noconcern.

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Ultimate compressive resistance by calculationfrom Ground Test results

Clause 7.6.2.3.

Two calculation methods:

Clause 7.6.2.3.

Two calculation methods:

Model pile: procedure (Clause 7 6 2 3(5)P) Model pile : procedure (Clause 7.6.2.3(5)P) Alternative procedure (Clause 7.6.2.3(8))

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Ultimate compressive resistance by calculation from

Model Pile method assumes a fictitious pile of the

Ground Test results (Clause7.6.2.3(5)P)

Model Pile method assumes a fictitious pile of thesame cross-section and length as proposed for the projectis installed at the location of each borehole or in-situ test.The shaft resistance and the base resistance arecalculated for the mean and minimum soil parameters for

h b h l t t fil Th t t f theach borehole or test profile. The two components of theresistance are then divided by a correlation factor which depends on the number of ground test profiles onwhich depends on the number of ground test profiles onthe site.

correlation factor 3 and 4 from Table A.NA.10

46CPGEC7course(Goh)

Clause 7.6.2.3(5)

)R()R(RRModel pile method

==

+=+=4

mincal;c

3

meancal;ccal;c

cal;scal;bk;sk;bk;c

)R(;

)R(MinR

RR)RR(R (7.8)

correlation factor 3 and 4 from Table A.NA.10depending on number of profiles n

meancalsmeancalbmeancalscalbmeancalc RRRRR )()()()( ;;;;; +=+=min;;min; )()( calscalbcalc RRR += min;;min; )()( calscalbcalc RRR +

Table A.NA.10 Correlation factors () to derive characteristic values of the resistance of axially loaded piles from ground test results (n - number of profiles of tests)loaded piles from ground test results (n number of profiles of tests)

for n = 1 2 3 4 5 7 10 3 1.55 1.47 1.42 1.38 1.36 1.33 1.3034 1.55 1.39 1.33 1.29 1.26 1.20 1.15 NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values of 3 and 4 may be divided by 1.1, provided that 3 is never less than 1.0, see EN 1997-1 7.6.2.3(7).

47

CPGEC7course(Goh)

Ultimate compressive resistance from Ground Test results

Alternative method Ground test results (shear strength,cone resistance etc) for all test locations are first combinedcone resistance etc) for all test locations are first combined(assessed) to derive the characteristic values of the baseresistance and shaft resistance in the various strata based ona cautious assessment of the test results and withoutapplying the factors . (Clause 7.6.2.3(8))A model factor is introduced to account for uncertainty of thecalculation results

Model factor = R;dcalculation results.

The value of the model factor should be 1.4, except that it maybe reduced to 1.2 if the resistance is verified by a maintainedload test taken to the calculated unfactored ultimate

48

load test taken to the calculated, unfactored ultimateresistance.

CPGEC7course(Goh)

Clause 7 6 2 3(8)

Alternative method

The characteristic values may be obtained by calculating:

Clause 7.6.2.3(8)

Rb;k = Ab qb;k and Rs;k = As;i qs;i;k (7.9)where qb;k and qs;i;k are characteristic values of base resistance and shaftfriction in the various strata i, obtained from values of ground parameters.

NOTE If this alternative procedure is applied, the values of the partialfactors b and s recommended in Annex A may need to be corrected by amodel factor larger than 1 0 The value of the model factor may be set bymodel factor larger than 1.0. The value of the model factor may be set bythe National annex.

This is the most common method for pile design in UK.

49CPGEC7course(Goh)

NA to SS EN 1997-1:2010A.3.3.2 Partial resistance factors for pile foundations

For verifications of the structural (STR) and geotechnical (GEO) limit states of pile foundations, thevalues of the partial factors on resistance (R) should be those given in Table A.NA.6, Table A.NA.7 andTable A.NA.8. These values are used to convert characteristic resistances to design values for ultimateli it t t l l ti Th l i ti f th b hi h th h t i ti i tlimit state calculations. They apply irrespective of the process by which the characteristic resistancesare derived.

Characteristic resistances may be derived from static load tests using EN 1997-1y g7.6.2.2 (7.6.3.2 for tensile loading), or from ground test results using EN 1997-1Equations 7.8 or 7.9 (7.17 or 7.18 for tensile loading). When the approach ofEquations 7.9 or 7.18 is used to derive the characteristic resistances, a modelfactor should be applied to the shaft and base resistance calculated usingcharacteristic values of soil properties by a method complying with EN 1997 -1,2.4.1(6). The value of the model factor should be 1.4, except that it may bereduced to 1.2 if the resistance is verified by a maintained load test taken to thecalculated, unfactored ultimate resistance.

Model factor = Model factor = R;dRb;k = Ab qb;k and Rs;k = As;i qs;i;k (7.9)

50CPGEC7course(Goh)

More than one profile of ground p gtest data?

Number of profiles = n Calculate characteristic pile

Yes No

Number of profiles n

l ti f t d

Calculate characteristic pile resistance from this single

profile of ground properties. Apply model factor R dcorrelation factor 3 and 4

from Table A.NA.10 depending on n

Apply model factor R;d. Apply partial factors b and s to determine design

resistance Rc d.resistance Rc,d.

Calculate characteristic pile A Aresistance for the different

profiles; Determine minimum to be

;qA

Rd;R

k;bbk;b = d;R

i;k;si;sk;s

qAR

=characteristic resistance

Rc;cal. Apply partial factors b and

t d t i d i

k;sk;bd;c

RRR +=

51

s to determine design resistance Rc;d.

CPGEC7course(Goh)

sb

Ultimate compressive resistance from static

load tests (Clause 7.6.2.2(8)P)

= 2

min;

1

;;

)(;

)( mcmeanmckc

RRMinR

Table A.NA.9 Correlation factors () to derive characteristic values of the resistance of axially loaded piles from static pile load tests (n - number of tested piles)

for n = 1 2 3 4 5 1 1.55 1.47 1.42 1.38 1.35 2 1.55 1.35 1.23 1.15 1.08 NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values 1 and 2 may be divided by 1.1, provided that 1 is never less than 1.0, see EN 1997-1 7.6.2.2(9).

Usually applies to trial (preliminary) piles and the resultsof tests on these piles are used to design the workingpiles

52CPGEC7course(Goh)

piles.

7.6.2.2 Compressive ground resistance from static load teststests

(2)P Trial piles to be tested in advance shall be installed in(2)P Trial piles to be tested in advance shall be installed inthe same manner as the piles that will form the foundationand shall be founded in the same stratum.

(3) If the diameter of the trial pile differs from that of theki il th ibl diff i f f ilworking piles, the possible difference in performance of piles

of different diameters should be considered in assessing thecompressive resistance to be adoptedcompressive resistance to be adopted.


(4) In the case of a very large diameter pile, it is oftenimpractical to carry out a load test on a full size trial pile.Load tests on smaller diameter trial piles may be consideredprovided that:provided that: the ratio of the trial pile diameter/working pile diameter is

not less than 0.5;; the smaller diameter trial pile is fabricated and installed in

the same way as the piles used for the foundation; the trial pile is instrumented in such a manner that the

base and shaft resistance can be derived separatelyf hfrom the measurements.

This approach should be used with caution for open-ended driven pilesThis approach should be used with caution for open ended driven pilesbecause of the influence of the diameter on the mobilisation of thecompressive resistance of a soil plug in the pile.


(5)P In the case of a pile foundation subjected to downdrag,the pile resistance at failure or at a displacement that equalsthe pile resistance at failure, or at a displacement that equalsthe criterion for the verification of the ultimate limit statedetermined from the load test results, shall be corrected. Thedetermined from the load test results, shall be corrected. Thecorrection shall be achieved by subtracting the measured, orthe most unfavourable, positive shaft resistance in thecompressible stratum and in the strata above, wherenegative skin friction develops, from the loads measured atthe pile headthe pile head.

(6) During the load test of a pile subject to downdrag, positive(6) During the load test of a pile subject to downdrag, positiveshaft friction will develop along the total length of the pile andshould be considered in accordance with 7.3.2.2(6). Themaximum test load applied to the working pile should be inexcess of the sum of the design external load plus twice thedowndrag force


downdrag force.

(10)P The systematic and random components of thevariations in the ground shall be recognised in thevariations in the ground shall be recognised in theinterpretation of pile load tests.

(11)P Th d f th i t ll ti f th t t il ( ) h ll(11)P The records of the installation of the test pile(s) shallbe checked and any deviation from the normal executionconditions shall be accounted forconditions shall be accounted for.


An important requirement stated in Eurocode 7 isthat the interpretation of the results of the pile loadtests must take into account the variability of theground over the site and the variability due todeviation from the normal method of pile installation.In other words, there must be a careful examinationof the results of the ground investigation and of thepile load tests results. The results of the pile loadtests might lead, for example, to differenthomogeneous parts of the site being identified,each with its own particular characteristic pilecompressive resistance. (Frank et al. 2004)


Ultimate compressive resistance from dynamic impact tests/pile driving formulae/wave equation analysis (Clause 7.6.2.4 to 7.6.2.6)

Table A.NA.11 Correlation factors ( ) to derive characteristic values of the

= 6

min;

5

;;

)(;

)( mcmeanmckc

RRMinR

for n = 2 5 10 15 20

( )resistance of axially loaded piles from dynamic impact tests (n - number of tested piles)

5 1.94 1.85 1.83 1.82 1.81 6 1.90 1.76 1.70 1.67 1.66 NOTE 1 The - values may be multiplied with a model factor of 0.85 when using dynamic impact tests with i l t hisignal matching.

NOTE 2 The - values should be multiplied with a model factor of 1.10 when using a pile driving formula with measurement of the quasi-elastic pile head displacement during the impact. NOTE 3 The - values should be multiplied with a model factor of 1.20 when using a pile driving formula without measurement of the quasi-elastic pile head displacement during the impact. NOTE 4 If different piles exist in the foundation groups of similar piles should be considered separately whenNOTE 4 If different piles exist in the foundation, groups of similar piles should be considered separately when selecting the number n of test piles. The blow counts used in pile driving should be obtained from driving

58CPGEC7course(Goh)

The blow counts used in pile driving should be obtained from driving records of at least five piles (Clause 7.6.2.5(4)).

Pile Load test methodPileLoadtestmethodstaticloadtests Rc;m andn

fil Applyb,s ort

RTableA.NA.9andT bl A NA 6profiles1,2 Rc;d TableA.NA.6

dynamic impacttests,piledriving

Rc;m andnprofiles5,6

Applyb,s ort Rc;dTableA.NA.11andTableA.NA.6, p g

formulae, waveequation

p 5, 6 c;d

G d t t th dGroundtestmethodalternativemethod (single

Applymodelfactor R d to

Applyb,s R dTableA.NA.6

method(singleprofile)

factor R;d,toobtainRc;k

Rc;dmodelpile Rc;cal andn Applyb,s TableA.NA.10method(nprofiles)

profiles3,4 Rc;d andTableA.NA.6


No.of staticloadtests groundtests dynamictestsSummary of correlation factors (NA to SS EN 1997-1:2010)

tests

mean min. mean min No.oftests

mean min.

1 2 3 4 5 61 1.55 1.55 1.55 1.55 --- --- ---2 1 47 1 35 1 47 1 39 2-4 1 94 1 902 1.47 1.35 1.47 1.39 2 4 1.94 1.903 1.42 1.23 1.42 1.334 1.38 1.15 1.38 1.295 1.35 1.08 1.36 1.26 5-9 1.85 1.76

7 1 33 1 207 1.33 1.20

10 1.30 1.15 10-14 1.83 1.7015-19 1.82 1.67

60

20 1.81 1.66CPGEC7course(Goh)

The SS NA (and BS NA) provide larger correlation factors toThe SS NA (and BS NA) provide larger correlation factors to those given in Annex A of SS EN 1997-1 : 2010.

According to Bauduin (2001), the correlation factors arebased on a reference value of about 10% for the COV of thebased on a reference value of about 10% for the COV of thepile compressive resistance. For the COV less than 10%,the mean of the resistance should govern the design,whereas for COV greater than 10%, the lowest resistanceshould govern. See Example 2.

61CPGEC7course(Goh)

Example 1A (Axially loaded pile in clay single profile of ground test data) Pground test data)

Piletype Boredpile

P

Pilelength(m) 30Pilewidth(m) 0.6

( )

Rs

cu;k (kPa)characteristicvalue 100Skinfriction 0.5Soil unit weight (kN/m3) 20

RbSoil unitweight(kN/m ) 20Permanentverticalload(kN) 1000Variableverticalload(kN) 200

Alternative method

Note: For simplicity, Self Weight of pile is omitted in the calculationscalculations

62CPGEC7course(Goh)

Pil t B d il P

Combination 1: A1 + M1 + R1 Example 1A

Piletype Boredpile

Pilelength(m) 30Pilewidth(m) 0.6c (kPa) characteristic value 100

P

cu;k (kPa)characteristicvalue 100Skinfriction 0.5Soil unitweight(kN/m3) 20

Permanent vertical load (kN) 1000

Rs

Permanentverticalload(kN) 1000

Variableverticalload(kN) 200

RbDesign Action (A1)A1 M1

G;dst 1.35G;stb 1.0

Design Action (A1)

Design vertical action G;stbQ;dst 1.5cu 1.0

gFc;d = 1000 x 1.35 + 200 x 1.5 = 1650 kN

63CPGEC7course(Goh)

Pil t B d il P

Material Factors (M1) cu = 1.0, cu = cu;k Example 1A Piletype Boredpile

Pilelength(m) 30Pilewidth(m) 0.6c (kPa) characteristic value 100

PA1 M1

G;dst 1.35G 1.0cu;k (kPa)characteristicvalue 100

Skinfriction 0.5Soil unitweight(kN/m3) 20


RsG;stb 1.0Q;dst 1.5cu 1.0



RbDesign Resistance (R1)Pile base resistance = 9cuPile shaft friction = cu = 0.5cu

Design Resistance (R1)

From Table A.NA.7 (Bored piles)

Base resistance Rb = 9cuAb = 9(100)( x 0.62/4)= 254 kNShaft resistanc Rs = 0.5cuAs = 0.5(100)(0.6 x 30)

R1

Base b 1.0Shaft 1 0Shaft resistanc Rs 0.5cuAs 0.5(100)(0.6 x 30)

= 2827 kNCompressive Resistance Rc;d = Rb;d + Rs;d

Shaft (compression)

s 1.0Total/Combined (compression)

t 1.0

64CPGEC7course(Goh)

Base resistance Rb = 9cuAb = 9(100)( x 0.62/4) = 254 kNShaft resistanc R = 0 5c A = 0 5(100)(0 6 x 30) = 2827 kN

Example 1A

Shaft resistanc Rs = 0.5cuAs = 0.5(100)(0.6 x 30) = 2827 kN

(A.3.3.2) For pile design from ground parameters, partial factors have to be corrected by a Model Factor = 1 4be corrected by a Model Factor R;d = 1.4Compressive Resistance Rc;d = Rb;d + Rs;d= (254/1 4 x 1 0) + (2827/1 4 x 1 0) = 2201 kN= (254/1.4 x 1.0) + (2827/1.4 x 1.0) = 2201 kN

Over-design factor = R d / F d = 2201 / 1650 = 1.33 > 1Over design factor Rc;d / Fc;d 2201 / 1650 1.33 > 1 OKFrom Table A.NA.7 (Bored piles)

R1

Base b 1.0


;qA

RdR

k;bbk;b = dR

i;k;si;sk;s

qAR

=Base b 1.0Shaft (compression)

s 1.0Total/Combined ( i )

t 1.0

d;R d;Rk;sk;b

dcRR

R +=65

(compression)

CPGEC7course(Goh)sb

d;cR +

Pil t B d il P

Combination 2: A2 + M1 + R4 Example 1A

Piletype Boredpile

Pilelength(m) 30Pilewidth(m) 0.6c (kPa) 100

P

cu;k (kPa) 100



Rs




G;dst 1.0G;stb 1.0

Design Action (A2)


gFc;d = 1000 x 1.0 + 200 x 1.3 = 1260 kN

66CPGEC7course(Goh)

Pil t B d il

Material Factors (M1) cu = 1.0, cu = cu;k A2 M1G;dst 1.0Piletype Boredpile


G;stb 1.0Q;dst 1.3cu 1.0

cu;k (kPa) 100



R4 with explicit verification of SLS A)





verification of SLS

Base b 1.7Shaft (compression)

s 1.4

Pile base resistance = 9cuPile shaft friction = cu = 0.5cu

Design Resistance (R4) ( p )Total/Combined (compression)

t 1.7

A) The lower values in R4 may be adopted (a) if serviceabilityis verified by load tests (preliminary and/or working) carriedout on more than 1% of the constructed piles to loads not lessthan 1.5 times the representative load for which they aredesigned, or (b) if settlement is explicitly predicted by a meansno less reliable than in (a) or (c) if settlement at the

67

no less reliable than in (a), or (c) if settlement at theserviceability limit state is of no concern.

CPGEC7course(Goh)Example 1A

Base resistance Rb = 9cuAb = 9(100)( x 0.62/4) = 254 kNShaft resistanc Rs = 0.5cuAs = 0.5(100)(0.6 x 20) = 2827 kN

Example 1A

(A.3.3.2) For pile design from ground parameters, partial factors have to be corrected by a Model Factor R;d = 1.4

Compressive Resistance R d = Rb d + R d

Compressive Resistance with SLS verification

Compressive Resistance Rc;d Rb;d + Rs;d= 254/(1.7 x 1.4) + 2827/( 1.4 x 1.4) = 254/(2.38) + 2827/(1.96) = 1549 kN

Over-design factor = Rc;d / Fc;d = 1549 / 1260 = 1.23 > 1 OK OKR4 with explicit


Base 1 7;qA

R k;bbk;b = i;k;si;sk;sqA

R= Base b 1.7

Shaft (compression)


t 1.7

;d;R

k;b d;Rk;s k;sk;b RR

68

(compression)

CPGEC7course(Goh)s

k;s

b

k;bd;c

RRR +=

Base resistance Rb = 9cuAb = 9(100)( x 0.62/4) = 254 kNShaft resistanc R = 0 5c A = 0 5(100)(0 6 x 20) = 2827 kN

Example 1A

Shaft resistanc Rs = 0.5cuAs = 0.5(100)(0.6 x 20) = 2827 kN(A.3.3.2) For pile design from ground parameters, partial factors have to be corrected by a Model Factor R;d = 1.4

Compressive Resistance R = R + RCompressive Resistance without SLS verification

y R;d

Compressive Resistance Rc;d = Rb;d + Rs;d= 254/(2.0 x 1.4) + 2827/( 1.6 x 1.4) = 254/(2.8) + 2827/(2.24) = 1353 kN 254/(2.8) 2827/(2.24) 1353 kN

Over-design factor = Rc;d / Fc;d = 1353 / 1260 = 1.07 > 1 OK OKR4 without explicit


B 2 0Base b 2.0Shaft (compression)


t 2.0

69

(compression)

CPGEC7course(Goh)

Comparison with conventional FSExample 1A


Applied vertical load = 1000 + 200 = 1200 kN

57.21200

2827254FS =+=

1200196951

28273

254Qallowable >=+= kN5.13120014982827254Q kN12001498

0.23Qallowable >=+= kNor


Comparison with conventional FS (Bored piles)

0251Q

3QQ sballowable += 0.2~5.13

Combination 2: A2 + M1 + R4 (with model factor = 1.4)


Rc;d = Qb/(1.7 x 1.4) + Qs/(1.4 x 1.4) = Qb/(2.38) + Qs/(1.96)

Compressive Resistance without SLS verification

Rc;d = Qb/(2.0.x 1.4) + Qs/(1.6 x 1.4) = Qb/(2.8) + Qs/(2.24)


Example 1B (Axially loaded pile in clay single profile of ground test data) Pof ground test data)

Piletype Boredpile

P

Pilelength(m) 30Pilewidth(m) 0.6cu;k (kPa)characteristicvalue 100

Rs

;

Skinfriction 0.5Soil unitweight(kN/m3) 20Permanent vertical load (kN) 800

RbPermanentverticalload(kN) 800Variableverticalload(kN) 400

Note: Self Weight of pile is omitted in the calculations

Effects of Load Combinations (Only CombinationEffects of Load Combinations (Only Combination 2 is considered in this example)

72CPGEC7course(Goh)

Pil t B d il P

Combination 2: A2 + M1 + R4 Example 1B

Piletype Boredpile


P

cu;k (kPa) 100



Rs




G;dst 1.0G;stb 1.0

Design Action (A2)


gFc;d = 800 x 1.0 + 400 x 1.3 = 1320 kN

73CPGEC7course(Goh)

Pil t B d il

Material Factors (M1) cu = 1.0, cu = cu;k A2 M1G;dst 1.0Piletype Boredpile


G;stb 1.0Q;dst 1.3cu 1.0

cu;k (kPa) 100








verification of SLS


s 1.4


Design Resistance (R4) ( p )Total/Combined (compression)

t 1.7

A) The lower values in R4 may be adopted (a) if serviceability is verifiedby load tests (preliminary and/or working) carried out on more than 1%of the constructed piles to loads not less than 1 5 times theof the constructed piles to loads not less than 1.5 times therepresentative load for which they are designed, or (b) if settlement isexplicitly predicted by a means no less reliable than in (a), or (c) ifsettlement at the serviceability limit state is of no concern.

74CPGEC7course(Goh)Example 1B


Example 1B


Compressive Resistance R d = Rb d + R d


Compressive Resistance Rc;d Rb;d + Rs;d= 254/(1.7 x 1.4) + 2827/( 1.4 x 1.4) = 254/(2.38) + 2827/(1.96) = 1549 kN

Over-design factor = Rc;d / Fc;d = 1549 / 1320 = 1.17 > 1 OK OKR4 with explicit


Base 1 7;qA


R= Base b 1.7

Shaft (compression)


t 1.7

;d;R

k;b d;Rk;s k;sk;b

d;cRR

R +=75

(compression)

CPGEC7course(Goh)sb

d;cR +

Comparison of Example 1A and 1B (Combination 2)

Effects of Load Combinations (Only Combination 2 is considered in this example)

Example 1A Example 1B

Permanent vertical load (kN)

1000 800

Variable vertical load 200 400Variable vertical load (kN)

200 400

Over-design factor 1.23 1.17Over design factor 1.23 1.17Design Length (m) for 23.98 25.23 =1.0


Example 1C (Axially loaded pile in sand single profile of ground test data) Pof ground test data)

Piletype Boredpile

P

1 mPilelength(m) 18Pilewidth(m) 0.6k characteristicvalue 35o

Rs18 m

kBearingcapacityfactorNq 49

Pileinterfacefriction 35oSoil unit weight (kN/m3) 20

Note: Self Weight of pile is omitted in the

RbSoil unitweight(kN/m ) 20Permanentverticalload(kN) 1000Variableverticalload(kN) 200

omitted in the calculations

A1 M1Combination 1: A1 + M1 + R1

Design Action (A1)

Design vertical action

G;dst 1.35G;stb 1.0Q d t 1.5

77CPGEC7course(Goh)

gFc;d = 1000 x 1.35 + 200 x 1.5 = 1650 kN

Q;dst 1.5cu 1.0

PPiletype BoredpilePilelength(m) 18

Example 1C K0 = (1 sin)

Rs

1 m

18

Pilewidth(m) 0.6k characteristicvalueBearingcapacityfactorNq

35o

49

il i f f i i 35

D i R i t (R1)

Rs18 mPileinterfacefriction 35oSoil unitweight(kN/m3) 20

Pile base resistance = qb = Nqvb(Ab)Pile shaft friction = q = tan(A )



Rb

Pile shaft friction = qs = h,averagetan(As)R1

Base b 1.0Shaft 1 0

( p )

= 20x1 + 17(20 ) = 190 kPa Shaft (compression)


t 1.0 vb = 20x1 + 17(20 w) = 190 kPah,average= 0.5vb(1 sin)

Base resistance Rb = 49(vb)( x 0.62/4) Shaft resistance R = 0 5 b(1 sin)tan(0 6 x 18)

78

Shaft resistance Rs 0.5 vb(1 sin )tan(0.6 x 18) CPGEC7course(Goh)

Base resistance Rb = 49(vb)( x 0.62/4) = 2632 kN Shaft resistanc Rs = 0.5vb(1 sin)tan(0.6 x 18) = 962 kN

Example 1C

s vb( ) ( )(A.3.3.2) For pile design from ground parameters, partial factors have to be corrected by a Model Factor R d = 1.4Compressive Resistance Rc;d = Rb;d + Rs;d= (2632/1 4 x 1 0) + (962/1 4 x 1 0) = 2567 kN

be corrected by a Model Factor R;d 1.4

= (2632/1.4 x 1.0) + (962/1.4 x 1.0) = 2567 kN

Over-design factor = R d / F d = 2567 / 1650 = 1.56 > 1Over design factor Rc;d / Fc;d 2567 / 1650 1.56 > 1 OKFrom Table A.NA.7 (Bored piles)

R1

Base b 1.0


;qA

R k;bbk;b =i;k;si;s

k;sqA

R =



t 1.0

d;R d;Rk;sk;b

d;cRR

R +=79

(compression)

CPGEC7course(Goh)

sbd;c

Pil t B d il

Combination 2: A2 + M1 + R4 Example 1C

Piletype Boredpile



A2 M1

G;dst 1.0G;stb 1.0Q;dst 1.3cu 1.0

Design Action (A2)

Design vertical actionDesign vertical action Fc;d = 1000 x 1.0 + 200 x 1.3 = 1260 kN

80CPGEC7course(Goh)


Example 1C


Compressive Resistance Rc;d = Rb;d + Rs;d


p c;d b;d s;d= 2632/(1.7 x 1.4) + 962/( 1.4 x 1.4) = 2632/(2.38) + 962/(1.96) = 1597 kN

Over-design factor = Rc;d / Fc;d = 1597 / 1260 = 1.27 > 1 OKR4 with explicit


Base 1 7;qA


R= Base b 1.7

Shaft (compression)


t 1.7

;d;R

k;b d;Rk;s k;sk;b RR

81

(compression)

CPGEC7course(Goh)s

k;s

b

k;bd;c

RRR +=


Example 1C


Compressive Resistance R = R + R

Compressive Resistance without SLS verification

Compressive Resistance Rc;d = Rb;d + Rs;d= 2632/(2.0 x 1.4) + 962/( 1.6 x 1.4) = 2632/(2.8) + 962/(2.24) = 1369 kN 2632/(2.8) 962/(2.24) 1369 kN

Over-design factor = Rc;d / Fc;d = 1369 / 1260 = 1.09 > 1 OK OKR4 without explicit




t 2.0

82

(compression)

CPGEC7course(Goh)

Comparison with conventional FSExample 1C


Applied vertical load = 1000 + 200 = 1200 kN

00.31200

9622632 =+=FS

1200151951

9623

2632 >=+=allowableQ kN5.13

120013589622632Q kN120013580.23

>=+=allowableQ kNor


Example 2 (Axially loaded pile in clay data from 3 boreholes) Pboreholes)

Piletype Boredpile

P

Pilelength(m) 30Pilewidth(m) 0.6c (kPa) BH1 100

Rs

cu (kPa)BH1 100cu (kPa)BH2 110c (kPa) BH3 130

Rbcu (kPa)BH3 130Skinfriction 0.5Soil unitweight 20 Note: Self Weight of pile is omitted in the calculationsg(kN/m3)

Permanentverticall d (kN)

1000

omitted in the calculations

M d l il th dload(kN)Variableverticalload(kN)

200Model pile method

84

( )

CPGEC7course(Goh)

PCombination 1: A1 + M1 + R1 Example 2 P

Design Action (A1)Rs


Rb

gFc;d = 1000 x 1.35 + 200 x 1.5= 1650 kN

A1 M1

G;dst 1.35G;stb 1.0G;stbQ;dst 1.5cu 1.0Material Factors (M1) cu = 1.0, cu = cu;k

85CPGEC7course(Goh)

Clause 7.6.2.3(5) Model pile method Example 2

==

+=+=4

min;

3

;;

;;;;;

)(;

)()( calcmeancalccalc

calscalbkskbkc

RRMinR

RRRRR (7.8)

correlation factor 3 and 4 from Table A.NA.10 depending on number of profiles n

RRRRR )()()()( meancalsmeancalbmeancalscalbmeancalc RRRRR )()()()( ;;;;; +=+=min;;min; )()( calscalbcalc RRR +=

Table A.NA.10 Correlation factors () to derive characteristic values of the resistance of axially loaded piles from ground test results(n - number of profiles of tests)loaded piles from ground test results(n number of profiles of tests)

for n = 1 2 3 4 5 7 10 3 1.55 1.47 1.42 1.38 1.36 1.33 1.3034 1.55 1.39 1.33 1.29 1.26 1.20 1.15 NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values of 3 and 4 may be divided by 1.1, provided that 3 is never less than 1.0, see EN 1997-1 7.6.2.3(7).

86

CPGEC7course(Goh)

Design Resistance (R1) cu (kPa)BH1 100cu (kPa)BH2 110

Example 2


u

cu (kPa)BH3 130Skinfriction 0.5

Base resistance Rb = 9cuAb = 9(cu)( x 0.62/4) Shaft resistanc Rs = 0.5cuAs = 0.5(cu)(0.6 x 30)

R1

Base b 1.0Shaft s 1.0Shaft (compression)


t 1.0Rc;cal = Rb;d + Rs;d

BH cu (kPa) Rb (kN) Rs (kN) Rc;cal (kN)

BH1 100 254 2827 3081BH1 100 254 2827 3081

BH2 110 280 3110 3390

BH3 130 331 3676 4007

87CPGEC7course(Goh)

Design Resistance (R1) Rc;cal = Rb;d + Rs;dExample 2


BH1 100 254 2827 3081

BH2 110 280 3110 3390BH2 110 280 3110 3390

BH3 130 331 3676 4007

(Rc;cal)mean = (3081+3390+4007)/3 = 3483 kN

(Rc;cal)min = 3081 kN

==+=+= min;;;; )(;)()( calcmeancalclcalscalbkkbk RRMinRRRRRR ===+= 43;;;;

;)( calckskbkc MinRRRR

88CPGEC7course(Goh)

Design Resistance (R1) Rc;cal = Rb;d + Rs;d Table A.NA.10 Example 2

(Rc;cal)mean = 3483 kN


==

+=+=4

min;

3

;;

;;;;;

)(;


calscalbkskbkc

RRMinR

RRRRR

= Min {(3483/1.42) ; (3081/1.33)} = Min {2436; 2317} = 2317 kN


BH1 100 254 2827 3081

BH2 110 280 3110 3390

BH1 gives minimumBH2 110 280 3110 3390

BH3 130 331 3676 4007

Rs;k = 2827/1.33 kN Rb;k = 254/1.33 kNR1

Base b 1.0Shaft s 1.0

89

Rc;d = Rb;k/b + Rs;k/s = 2317 kN (compression)Total/Combined (compression)

t 1.0CPGEC7course(Goh)

Note: The lowest value is the lowest of the total compressiveExample 2

presistance, and not a combination of the lowest basecompressive resistance and the lowest shaft frictiond d d f th t tdeduced from another test.

++ min;;;; )(;)()( calcmeancalccalscalb RRMinRRRRRR

R d = Rb k/b + R k/ = 2317 kN ===+= 4

;

3

;;

;;;;; ;)( calckskbkc MinRRRR


Rc;d Rb;k/b + Rs;k/s 2317 kN

Fc;d = 1000 x 1.35 + 200 x 1.5 = 1650 kN

Over-design factor = 2317 / 1650 = 1 40 > 1Over-design factor = 2317 / 1650 = 1.40 > 1 OK

90CPGEC7course(Goh)


Design Action (A2)

RsDesign vertical action F d = 1000 x 1.0 + 200 x 1.3

Rb

Fc;d 1000 x 1.0 + 200 x 1.3= 1260 kN

A2 M1

G;dst 1.0G;stb 1.0Material Factors (M1) cu = 1.0, cu = cu;k G;stbQ;dst 1.3cu 1.0

Material Factors (M1)

91CPGEC7course(Goh)

Pil t B d il

Material Factors (M1)A2 M1

Example 2

Piletype Boredpile


cu = 1.0, cu = cu;k G;dst 1.0G;stb 1.0Q;dst 1.3

cu;k (kPa) 100


Permanent vertical load (kN) 1000 R4 ith li it

From Table A.NA.7 (Bored piles)cu 1.0





Base b 1.7Shaft 1 4


Design Resistance (R4) Shaft (compression)


t 1.7

A) The lower values in R4 may be adopted (a) if serviceability is verifiedby load tests (preliminary and/or working) carried out on more than 1%of the constructed piles to loads not less than 1 5 times theof the constructed piles to loads not less than 1.5 times therepresentative load for which they are designed, or (b) if settlement isexplicitly predicted by a means no less reliable than in (a), or (c) ifsettlement at the serviceability limit state is of no concern.

92CPGEC7course(Goh)

Design Resistance (R4)Rc;cal = Rb + Rs

Example 2

BH cu(kPa)

Rb(kN)

Rs(kN)

Rc;cal (kN)

BH1 100 254 2827 3081BH1 100 254 2827 3081

BH2 110 280 3110 3390

BH3 130 331 3676 4007

(Rc;cal)mean = (3081+3390+4007)/3 = 3493 kN


+ )()( RRRR

==

+=+=4

min;

3

;;

;;;;;

)(;


calscalbkskbkc

RRMinR

RRRRR

93CPGEC7course(Goh)

Design Resistance (R4) Rc;cal = Rb;d + Rs;d Table A.NA.10 Example 2

(Rc;cal)mean = 3493 kN


Mi {(3493/1 42) (3081/1 33)} Mi {2443 2317} 2317 kN

(Rc;cal)min 3081 kN

==

+=+=4

min;

3

;;

;;;;;

)(;


calscalbkskbkc

RRMinR

RRRRR

= Min {(3493/1.42) ; (3081/1.33)} = Min {2443; 2317} = 2317 kN


BH1 100 254 2827 3081

BH2 110 280 3110 3390

BH3 130 331 3676 4007

BH1 gives minimum


BH3 130 331 3676 4007

Rs;k = 2827/1.33 kN Rb;k = 254/1.33 kNBase b 1.7Shaft (compression)

s 1.4Total/Combined 1 7

Rs;k 2827/1.33 kN Rb;k 254/1.33 kN

Rc;d = Rs;k/b + Rb;k/s= 2827/(1.33 x 1.4) + 254/(1.33 x 1.7)

94

Total/Combined (compression)

t 1.7 2827/(1.33 x 1.4) + 254/(1.33 x 1.7)= 1631 kN

CPGEC7course(Goh)

Compressive Resistance with SLS verificationExample 2


Rc;d = Rs;k/b + Rb;k/s = 2827/(1.33x1.4) + 254/(1.33x1.7) = 2827/(1.86) + 254/(2.26) = 1631 kN

Design vertical action F = 1000 x 1 0 + 200 x 1 3 = 1260 kN

Over-design factor = 1631 / 1260 = 1.29 > 1 Fc;d = 1000 x 1.0 + 200 x 1.3 = 1260 kN

OKR4 with explicit




95CPGEC7course(Goh)


t 1.7

Compressive Resistance without SLS verificationExample 2


Rc;d = Rs;k/b + Rb;k/s = 2827/(1.33x1.6) + 254/(1.33x2.0) = 2827/(2.13) + 254/(2.66) = 1423 kN

Design vertical action F = 1000 x 1 0 + 200 x 1 3 = 1260 kN

Over-design factor = 1423 / 1260 = 1.13 > 1 Fc;d = 1000 x 1.0 + 200 x 1.3 = 1260 kN

OKR4 without explicit



s 1.6Total/Combined t 1.7

96CPGEC7course(Goh)

(compression)t

According to Bauduin (2001), the correlation factors arebased on a reference value of about 10% for the COV of thepile compressive resistance. For the COV less than 10%,the mean of the resistance should govern the design,whereas for COV greater than 10% the lowest resistancewhereas for COV greater than 10%, the lowest resistanceshould govern.


Example 3 (Axially loaded pile in clay data from 4 static pile load Pclay data from 4 static pile load tests, tested to failure)

P

Piletype BoredpilePile length (m) 30

Rs

Pilelength(m) 30Pilewidth(m) 0.6PileTest #1Rm (kN) 4000 RbmPileTest #2Rm (kN) 4200PileTest #3Rm (kN) 4500 Note: Self Weight of pile is omitted in the calculationsPileTest #4Rm (kN) 5000Permanentverticall d (kN)

1000

the calculations

load(kN)Variableverticalload(kN)

200

98

( )

CPGEC7course(Goh)


Design Action (A1)

RsDesign vertical action Fc;d = 1000 x 1.35 + 200 x 1.5

1650 kN

Rb

= 1650 kN

A1 M1

G;dst 1.35G;stb 1.0Material Factors (M1) G;stbQ;dst 1.5cu 1.0

99CPGEC7course(Goh)

Ultimate compressive resistance from static load tests Example 3

)()( RR

(Clause 7.6.2.2)

= 2

min;

1

;;

)(;

)( mcmeanmckc

RRMinR

Table A.NA.9 Correlation factors () to derive characteristic values of the resistance of axially loaded piles from static pile load tests (n - number of tested piles)

for n = 1 2 3 4 5 1 1.55 1.47 1.42 1.38 1.35 2 1.55 1.35 1.23 1.15 1.08 NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values 1 and 2 may be divided by 1.1, provided that 1 is never less than 1.0, see EN 1997-1 7.6.2.2(9).

100CPGEC7course(Goh)

Design Resistance (R1) PileTest #1Rm (kN) 4000Pil T t #2 R (kN) 4200

Example 3

PileTest #2Rm (kN) 4200PileTest #3Rm (kN) 4500Pile Test #4 R (kN) 5000

(Rc;m)mean = (4000+4200+4500+5000)/4 = 4425 kN

PileTest #4Rm (kN) 5000

(Rc;m)min = 4000 kN

=

min;;;

)(;

)( mcmeanmckc

RRMinR

= Min {(4425/1 38) ; (4000/1 15)} = Min {3207; 3478}

21;

Table A.NA.9

= Min {(4425/1.38) ; (4000/1.15)} = Min {3207; 3478} = 3207 kN

for n = 1 2 3 4 5 1 1.55 1.47 1.42 1.38 1.35 2 1.55 1.35 1.23 1.15 1.08

101

NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values 1 and 2 may be divided by 1.1, provided that 1 is never less than 1.0, see EN 1997-1 7.6.2.2(9).

CPGEC7course(Goh)

Design Resistance (R1)Example 3


Rc;d = 3207 kN

Design vertical action Fc;d = 1000 x 1.35 + 200 x 1.5 = 1650 kN

Over-design factor = 3207 / 1650 = 1.94 > 1 OK

R1



t 1.0

102

(compression)

CPGEC7course(Goh)


Design Action (A2)

RsDesign vertical action Fc;d = 1000 x 1.0 + 200 x 1.3

1260 kN

Rb

= 1260 kN

A2 M1

G;dst 1.0G;stb 1.0Material Factors (M1) G;stbQ;dst 1.3cu 1.0


Design Resistance (R4) PileTest #1Rm (kN) 4000Pil T t #2 R (kN) 4200

Example 3

PileTest #2Rm (kN) 4200PileTest #3Rm (kN) 4500Pile Test #4 R (kN) 5000PileTest #4Rm (kN) 5000

(Rc;m)mean = (4000+4200+4500+5000)/4 = 4425 kN

(Rc;m)min = 4000 kN

= Min {(4425/1.38) ; (4000/1.15)} = Min {3207; 3478}

Table A.NA.9

{( ) ( )} { }= 3207 kN

for n = 1 2 3 4 5 1 1.55 1.47 1.42 1.38 1.35 2 1.55 1.35 1.23 1.15 1.08

104

NOTE For structures having sufficient stiffness and strength to transfer loads from ''weak'' to "strong piles, values 1 and 2 may be divided by 1.1, provided that 1 is never less than 1.0, see EN 1997-1 7.6.2.2(9).

CPGEC7course(Goh)


Compressive Resistance with SLS verification Example 3


Rc;k = 3207 kN


Compressive Resistance Rc;d = 3207/(1.7) = 1886 kN

O d i f t 1886 / 1260 1 50 1






t 1.7

105

(compression)

CPGEC7course(Goh)


Compressive Resistance without SLS verification Example 3


Rc;k = 3207 kN


Compressive Resistance Rc;d = 3207/(2.0) = 1604 kN

O d i f t 1604 / 1260 1 27 1



R4 without explicit verification of SLS A)



t 2.0

106

(compression)

CPGEC7course(Goh)

Pile subjected to Downdrag (Negative skin friction)

Two approaches:

Clause 7.3.2.1(3)P

o app oac es

(a) the ground displacement is treated as an action. Aninteraction analysis (e.g., t-z method) is then carried out todetermine the forces, displacements and strains in the pile;

(b) an upper bound to the force, which the ground couldtransmit to the pile shall be introduced as the design action.p g

Downdrag is considered a permanent action


Example 4 (Pile subjected to Downdrag)P surcharge

Example 4

Piletype BoredpilePilewidth(m) 0.3

P

5 m soft clayFD

surcharge

downdrag skinfrictionqD;k(kPa)characteristicvalue 20

stiffclayskinfrictionqs;k(kPa) characteristic value

50 R

5 m soft clay

18 m stiff clay

FD

(kPa)characteristicvalue


Rs

Rb

y

A surcharge is placed at ground level after pile installation, causing settlement ofthe soft clay and downdrag FD (negative skin friction) on the pile. The baseresistance Rb is assumed to be negligible.

Note: For simplicity, Self Weight of pile is omitted in the calculations

Any variable action may usually be ignored (Clause 7.3.2.2(7))

E l M difi d f Si & D i ll (1998) E d 7 t

y y y g ( ( ))In most cases, downdrag is only relevant for SLS

108

Example Modified from Simpson & Driscoll (1998) Eurocode 7 a commentary

CPGEC7course(Goh)

il d il P surcharge

Example 4

Piletype BoredpilePilewidth(m) 0.3downdrag skinfrictionqD;k(kP ) h i i l

20

P

5 m soft clayFD

surcharge

(kPa)characteristicvaluestiffclayskinfrictionqs;k(kPa)characteristicvalue

50

R

5 m soft clay

18 m stiff clay

FD

Permanentverticalload(kN) 300Rs

Rb

y

The interaction between the pile shaft and the soft clay should take intoaccount the relative movement of the pile and the soil eg. using t-zmethod. This may result in negative skin friction that varies with depthand the location of the neutral point above the bottom of the layer.

This approach is more complicated that assuming a maximum (limiting)downdrag load along the entire length of the pile in the settling layer.In this example, for simplicity the maximum downdrag load is assumed.

109

In this example, for simplicity the maximum downdrag load is assumed.

CPGEC7course(Goh)

Piletype BoredpilePile width (m) 0 3 P surcharge

Example 4

Pilewidth(m) 0.3downdrag skinfrictionqD;k(kPa)characteristicvalue

20

stiff clay skin friction q k 50

P

5 m soft clayFD

surcharge

stiffclayskinfrictionq s;k(kPa)characteristicvalue

50

Permanentverticalload(kN) 300 R

5 m soft clay

18 m stiff clay

FD

Rs

Rb 0

y


A1 M1

G;dst 1.35G;stb 1.0

Design Action (A1)

Total downdrag load = FD;k = (0.3)(5)qD;k G;stbQ;dst 1.5cu 1.0

; ;= (0.3)(5)(20) = 94.2 kNDesign value of downdrag load FD;d = GFD;kDesign vertical action

g g D;d G D;k= 1.35 x 94.2

110

Fc;d = 300 x 1.35 + 94.2 x 1.35 = 532 kNCPGEC7course(Goh)

Piletype BoredpilePilewidth(m) 0.3 P surcharge

Example 4

( )

stiffclayskinfrictionqs;k(kPa)characteristicvalue

50

P

5 m soft clayFD

surcharge

R

5 m soft clay

18 m stiff clay

FD

Combination 1: A1 + M1 + R1Design Resistance (R1) Rs

Rb 0

yDesign Resistance (R1)

A.3.3.2 Model Factor R;d = 1.4C i R i t R R

R1


Compressive Resistance Rc;d = Rs;d= (0.3)(18)50/( 1.0 x 1.4) = 606 kN

R1

Base b 1.0Shaft ( i )

s 1.0Over-design factor = Rc;d / Fc;d= 606 / 532 = 1.13 > 1

D i ti l ti

(compression)Total/Combined (compression)

t 1.0 OK

111

Design vertical action Fc;d = 300 x 1.35 + 94.2 x 1.35 = 532 kN

CPGEC7course(Goh)

Piletype BoredpilePilewidth(m) 0.3 P surcharge

Example 4

( )

downdrag skinfrictionqD;k(kPa)characteristicvalue

20

stiffclayskinfrictionqs;k 50

P

5 m soft clayFD

surcharge

s;k(kPa)characteristicvalue

Permanentverticalload(kN) 300R

5 m soft clay

18 m stiff clay

FD

Rs

Rb 0

y

Design Action (A2) and M2


g ( )

Total downdrag load = FD;k = (0.3)(5)qD;k= (0.3)(5)(20) = 94.2 kNDesign value of downdrag load F = ( )F


A2 M2

G;dst 1.01 0

Design value of downdrag load FD;d = ()FD;k= 1.25 x 94.2 = 118 kN Design vertical action Fc;d = 300 x 1.0 + FD;d = 418 kN

G;stb 1.0Q;dst 1.3 1.25M2 = 1 25 is considered an action factor because downdrag is

112

M2 1.25 is considered an action factor because downdrag isusually calculated by effective stress analysis (eg. method)

CPGEC7course(Goh)

P surcharge

Compressive Resistance with SLS verification Example 4 P

5 m soft clayFD

surchargeCombination 2: A2 + M1 + R4

R

5 m soft clay

18 m stiff clay

FDDesign Resistance (R4)

A.3.3.2 Model Factor R;d = 1.4 Rs

Rb 0

yR;dCompressive Resistance Rc;d = Rs;d= (0 3)(18)50/( 1 4 x 1 4) = 433 kN

From Table A NA 7 (Bored piles)

= (0.3)(18)50/( 1.4 x 1.4) = 433 kN

Over-design factor = Rc;d / Fc;d From Table A.NA.7 (Bored piles)Over design factor Rc;d / Fc;d= 433 / 418 = 1.04 > 1 OK R4 with explicit verification of SLS A)



113


t 1.7

CPGEC7course(Goh)

P surcharge

Compressive Resistance without SLS verification Example 4 P

5 m soft clayFD

surchargeCombination 2: A2 + M1 + R4

R

5 m soft clay

18 m stiff clay

FDDesign Resistance (R4)

A.3.3.2 Model Factor R;d = 1.4 Rs

Rb 0

yR;dCompressive Resistance Rc;d = Rs;d= (0 3)(18)50/( 1 4 x 1 6) = 379 kN

From Table A NA 7 (Bored piles)

= (0.3)(18)50/( 1.4 x 1.6) = 379 kNOver-design factor = Rc;d / Fc;d

From Table A.NA.7 (Bored piles)= 379 / 418 = 0.91 < 1 Not OK R4 without explicit




114


t 2.0

CPGEC7course(Goh)

Thank You


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