Annex B

(normative)

Design aspects in reference with EN 1992-1-1

B.1 General

B.1.1 Scope

This Annex B applies to the design of precast concrete foundation piles made of reinforced or prestressed concrete and is complementary to EN 1992-1-1.

The numbering of Clauses of this Annex is arranged in the same order as used for the numbering of Clauses of EN 1992-1-1.

The principles and application rules of EN 1992-1-1 shall be adhered to, unless explicitly adapted, amended or modified.

Additional provisions for the single bar foundation pile are given in Annex C.

B.2 Basis of design

B.2.1 Requirements

B.2.1.1 Basic Requirements

P(4) The precast foundation pile shall be designed in accordance with the principles and application rules of EN 1997-1:2004, 7.8.

P(5) The design for transient situations shall consider the intended methods of handling, transportation and installation, using the nominal dimensions and a time corresponding specified minimum strength.

B.2.3 Basic variables

B.2.3.1 Actions and environmental influences

B.2.3.1.1 General

P(2) The dynamic action during handling, transportation and driving shall be taken into account according to the actual operational methods.

NOTE In absence of more rigorous determination, in addition to partial load factors, the factor allowing for the dynamic effects on the self-weight of the pile may be taken on the basis of the following recommended values which are inclusive of the self-weight partial safety factor:

γG γkd, dyn = 1,35 for handling and for transportation of continuously supported piles;

γG γkd, dyn = 2,00 for transportation of locally supported piles.

B.2.4 Verification by the partial safety factor method

B.2.4.2 Design values

B.2.4.2.4 Partial safety factors for materials

(4) The partial safety factors for materials given in EN 1992-1-1 may be modified in accordance with 4.3.3.5 of EN 13369:2004.

B.3 Materials

B.4 Durability and cover to reinforcement

B.4.4 Methods of verification

B.4.4.1 Concrete cover

B.4.4.1.1 General

B.4.4.1.2 Concrete cover, cmin

(14) The concrete cover may be modified in accordance with EN13369:2004, 4.3.7.

(15) Where after installation the head of the precast foundation pile will be stripped, the concrete cover over the stripping length may be reduced to 10 mm.

B.5 Structural analysis

B.6 Ultimate limit states (ULS)

B.7 Serviceability limit states (SLS)

B.8 Detailing of reinforcement and prestressing tendons

B.8.4 Anchorage of longitudinal reinforcement

B.8.4.1 General

B.8.4.2 Ultimate bond stress

(3) For horizontally cast foundation piles the limiting value of the depth in the direction of concreting, defining areas with good bond conditions, may be taken as 350 mm, due to the application of an effective compacting technique.

B.8.7 Laps and mechanical couplers

B.8.7.4 Transverse reinforcement in the lap zone

B.8.7.4.2 Transverse reinforcement for bars permanently in compression

(2) Pile joint anchors and additional longitudinal bars in pile heads are not to be considered as bars in a lap slice.

B.9 Detailing of members and particular rules

B.9.5 Precast foundation piles

(1) For the single bar pile, see Annex C of this document.

B.9.5.2 Longitudinal reinforcement

P(1) For piles Class 1 the following requirements shall be met:

  • a) bars shall have a diameter not less than 8 mm;
  • b) welds or lap slices in bars shall be staggered. The distance between those shall not be less than two times the largest transversal dimension of the pile shaft;
  • c) for piles shafts with a non-circular cross-section, at least one bar shall be positioned at each corner;
  • d) for piles shafts with a circular cross-section, at least 6 bars shall be positioned around the periphery;
  • e) the spacing of bars shall comply with EN 1992-1-1:2004, 8.2.

B.9.5.3 Transverse reinforcement

P(2) For piles Class 1 the following requirements shall be met:

  • a) for precast concrete foundation piles with transverse dimensions 300 mm or larger, the diameter of the transverse reinforcement may be reduced to 5 mm;
  • b) for precast foundation piles with transverse dimensions smaller than 300 mm, the diameter of the transverse reinforcement may be reduced to 4 mm;
  • c) the links, either stirrups or spirals, shall have a nominal diameter not less than 4 mm;
  • d) the transverse reinforcement in the pile head shall be applied over a length of at least 500 mm. The number of links along this minimum length shall not be less than 9;
  • e) in case the pile toe is positioned in alluvial deposits, the transverse reinforcement shall be applied over a length of at least 200 mm. The number of links over this minimum length shall be not less than 5. In case a pile rests on hard rock or moraine layers, the transverse reinforcement shall be applied over a length of at least 500 mm. The number of links shall be adapted accordingly;
  • f) the transverse reinforcement of the pile shaft between the pile head and pile toe shall be evenly distributed, while the spacing of the links shall not exceed three times the shaft depth/width, whichever is the less;
  • g) the diameter of mandrels used for bending the transverse reinforcement shall not be less than 2,5 times the nominal diameter in case of cold bending and nor less than 1,5 times in case of hot bending;
  • h) in hollow core piles the cross sectional area of ties between the pile head and pile toe shall be at least 0,15 % of the concrete cross-section. The diameter of transverse spiral reinforcement shall be at least 2,4 mm or 1/4 of the diameter of the longitudinal bars, the spacing shall be less than 15 times the diameter of the longitudinal bars.

B.9.5.4 Detailing aspects

P(1) For piles Class1 the following requirements according detailing aspects shall be met:

  • a) the prestressing tendons shall be arranged in the cross-section and prestressed in such a way that the resultant of the tendon forces coincides with the centre of the cross section of the pile shaft;
  • b) the cross-sectional area of prestressing steel shall not be less than the percentage of the cross-sectional area of the pile shaft according Table B1;
  • c) the spacing of tendons shall comply with EN 1992-1-1:2004, 8.10, bundled tendons are not permitted;
  • d) for the transverse reinforcement the requirements of 4.2.3.1 apply, except paragraph d);
  • e) if in precast prestressed foundation piles in addition longitudinal reinforcement is applied, not more than 4 bars end in the same plane;
  • f) the distance between these planes is not less than 20 times the diameter of the applied bars.
Table B.1 — Minimum percentages of prestressing steel
Pile length L (m) Percentage of the concrete cross-section in mm2
Not exceeding 10 m 0,1
Between 10 m and 20 m 0,01 L
Exceeding 20 m 0,2

Annex C

(normative)

Provisions for the design and manufacture of piles reinforced with a single bar in reference with this document and EN 1992-1-1

General

This Annex aims to give the additional specific requirements for the piles reinforced with a single bar.

The reference of the chapters and sub-sections of this Annex are arranged in the same order as used in the main body of this document for Clauses C.4 to C.8 and in the same order as in Annex B for Clause C.9.

C.4 Requirements

C.4.1 Material requirements

4.1 of this document is applicable.

C.4.2 Production requirements

4.2 of this document is applicable, except 4.2.3.1.

B.4.4.1, concrete cover, is not applicable to single bar, short piles or pile segments. Minimum cover to reinforcement from any plane surface of the pile shall be 50 mm.

C 4.3 Finished product requirements

4.3 of this document is applicable to single bar piles and pile segments except where modified below:

C.4.3.1 Geometrical properties

C.4.3.1.1 Production tolerances

This sub-section of the document does not apply to single bar piles or pile segments with respect to deviations relating to the position of reinforcing steel. The single bar shall be placed centrally on the longitudinal axis of the pile within a tolerance of 15 mm.

It does apply with regard to the permitted deviations to the cross sectional dimensions of the overall finished product.

C.4.3.1.2 Maximum dimensions

The shape factor applicable to the manufacture of single bar piles and pile segments shall not exceed 20.

C.5 Test methods

Clause 5 of this document is applicable.

C.6 Evaluation of conformity

Clause 6 of this document is applicable.

C.7 Marking

Clause 7 of this document is applicable.

C.8 Technical documentation

Clause 8 of this document is applicable.

C.9 Detailing of members and particular rules

C.9.5 Precast foundation piles

C.9.5.2 Longitudinal reinforcement

P(1) Alternative provision by addition of paragraph (g).

f) Single length piles or pile segments whose shape factor is 20 or less shall be reinforced with a single bar situated at the centre of the cross section of the pile or pile segment. Paragraphs (b) to (e) of 9.5.2 of Annex B do not apply to single bar piles or pile segments.

C.9.5.3 Transverse reinforcement

P(1) Alternative provision by addition of paragraph (i).

i) Where piles or pile segments are reinforced with a single centrally located bar a crack ring shall be provided at the pile or pile segment head and toe. Paragraphs (a) to (h) of 9.5.3 of Annex B shall not apply to single bar piles or pile segments.

(informative)

Provisions for the design and installation of piles and pile segments reinforced with a single bar

D.1 General

D.1.1 Scope

The provisions of Annex B are applicable to single bar piles and pile segments unless specifically adapted, amended or modified by Annex C or for specific ground conditions as defined in this Annex.

D.2 Basic of design

D.2.1 Requirements

D.2.1.1 Basic Requirements

The following requirements should be taken into account by the designer and pile installer when using single bar, short segmental reinforced concrete piles with compression joints only:

  • a) where very large boulders or artificial hard obstructions e.g. concrete, of boulders size or larger, are present that may cause lateral displacement of the pile toe during driving they should either be removed prior to piling or alternative pile positions identified. Where this is not possible an alternative pile system should be considered;
  • b) where steeply sloping hard strata exists that may cause lateral displacement of the pile toe an alternative pile system should be used;
  • c) where considerable depths of loose granular soils (SPT 'N' < 4), or soft cohesive soils (Cu < 25 kN/m2) exist specific design calculations are to be produced to demonstrate that adequate lateral restraint against buckling of the pile is provided by the soil;
  • d) where the thickness of any layer of highly compressible layer of soil (mv > 0,8 m2.(MN)–1) exceeds the pile segment length such that more than 1 joint is located in the layer an alternative piling system should be used;
  • e) where significant tensile actions after installation need to be sustained by the pile, joints capable of transferring tension should be used over the length of pile required to transfer the actions to the ground.

Annex E

(normative)

Method to measure perpendicularity of the pile top, pile bottom or pile joint against pile axis

E.1 Principle

A square (longer arm at least 800 mm) rests against spacers so that longer arm is against one of the longitudinal moulded surface of the pile, see Figure E.1. The angular deviation of the pile top, pile bottom or pile joint against one of the longitudinal moulded surface is determined as shown in Figure E.1 for corner A. Distance reading of the measuring point shall be measured with an accuracy of 0,2 mm. Angular deviation is distance reading of the measuring point (thickness of the spacer subtracted) divided with a distance between corner A and measuring point.

Measurements of angular deviation shall be done in two directions (e.g. horizontal and vertical direction as shown in Figure E.2).

NOTE Measuring equipment which measures angular deviation in two directions same time can be used.

E.2 Test results

Results of angular deviation in both two directions are recorded. Test result is the greater value.

Measurement of angular deviation

Key

  • 1 Measuring point
  • 2 Spacer
  • 3 Square
  • 4 Corner A
Figure E.1 — Measurement of angular deviation

Key

  • 1 Upper surface
  • 2 Corner A
Figure E.2 — An example to measure angular deviation in two directions

EN 12794:2005 Precast concrete products – Foundation piles