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Bridging the gap
REVISION OF BSS 8002, 8004, AND 8081
Dr Andrew Bond (Geocentrix)
Dr Caesar Merrifield (Coffey)
Dr Devon Mothersille (Geoserve Global)
REV
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Outline of talk
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
2
Revival of withdrawn/obsolete geotechnical standards Several important geotechnical ‘codes of practice’ were withdrawn in March 2010 on the introduction of the Structural Eurocodes, including:
• BS 8004:1986, Code of practice for foundations
• BS 8002:1994, Code of practice for earth retaining structures
The following standard remained but was largely incompatible with Eurocode 7:
• BS 8081:1989, Code of practice for ground anchorages (renamed ‘grouted anchors’)
The ‘revival’ of these standards was sponsored by HS2 because they want to put them out with contracts for enabling work starting in June 2015.
Additional (related) work sponsored by HS2 includes:
• Revision of CIRIA C580 (2003), Embedded retaining walls – guidance for economic design
• Creation of PAS 8812, Guide to the application of European Standards in temporary works design (co-sponsored by the Temporary Works Forum, TWf)
Other relevant (related) work includes:
• Revision of BS 5930:1999+A2:2010, Code of practice for site investigations (renamed ‘ground investigations’)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
MO
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Relationship between British Standards and Eurocode 7
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
3
BS 8
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S Presentational conventions for the ‘new’ geotechnical BSs
“The provisions of this standard are presented in roman (i.e. upright) type. Its recommendations are expressed in sentences in which the principal auxiliary verb is
“should”. Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.”
Foreword to BSs 8002, 8004, and 8081
• “should” expresses recommendations of these standard
• “may” expresses permissibility (e.g. as an alternative to the primary recommendation)
• “can” expresses possibility (e.g. a consequence of an action or an event)
Notes and commentaries are provided throughout the text of this standard. Notes give references and additional information that are important but do not form part of the recommendations. Commentaries give background information.
Note that the word “shall” is NOT used in BSs 8002, 8004, or 8081
“shall” is used in Eurocode 7 (BS EN 1997-1 and -2)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Eurocode 7 timeline 2010-2020
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
4
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Proposed structure of EN 1997-1: 202x and EN 1997-2: 202x
EN 1997: 202x
1. General rules
2. Ground investigation
3. Geotechnical constructions
Part 1 – General rules
1. General
2. Basis of geotechnical design
3. Materials
4. Durability
5. Geotechnical analysis
6. Ultimate limit states
7. Serviceability limit states
8. Execution
9. Testing
10. Reporting
Part 2 – Ground investigation
1. General
2. Principles of ground investigation
3. Planning of ground investigations
4. Sampling and groundwater measurements
5. Field tests
6. Laboratory tests
7. Reporting
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
NEW
EU
RO
CO
DE 7
PA
RT 3
Proposed EN 1997-3:202x – Geotechnical constructions
EN 1997: 202x
1. General rules
2. Ground investigation
3. Geotechnical constructions
Part 3 – Geotechnical constructions
1. General
2. Slopes, cuttings, and embankments
3. Spread foundations
4. Pile foundations
5. Retaining structures
6. Anchors
7. Ground improvement
8. Reinforced soil structures
Annexes (calculation models for each type of construction)
Part 3’s common sub-sections
1. General
2. Actions and design situations
3. Design considerations
4. Design methods/calculation models
5. Ultimate limit state design
6. Serviceability limit state design
7. Structural design
8. Execution (supervision, monitoring, and maintenance)
9. Testing
10. Reporting
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
5
BS 8
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Changing contents of BS 8004 for foundations BS 8004:1986 (186 pp) Foreword (1 pp) 1. General (7 pp) 2. Design of foundations (27 pp) 3. Shallow foundations (5 pp) 4. Deep and subaqueous foundations (13
pp) 5. Cofferdams and caissons (17 pp) 6. Geotechnical processes: groundwater
lowering, grouting and other methods of changing the ground characteristics in situ (38 pp)
7. Pile foundations (32 pp) 8. Tide work, underwater concreting and
diving (6 pp) 9. Site preparation for foundation work
(6 pp) 10. Durability of timber, metal and
concrete structures (9 pp) 11. Safety precautions (10 pp) Appendices (10 pp)
DPC BS 8004:2015 (101 pp)
Foreword (1 pp)
1. Scope (1 pp)
2. Normative references (4 pp)
3. Terms and definitions (1 pp)
4. General rules (25 pp)
5. Spread foundations (11 pp)
6. Pile foundations (42 pp)
Annexes (*normative)
A. *Underpinning (4 pp)
B. *Helical pile foundations (4 pp)
C. Specific formations (2 pp)
Bibliography (5 pp)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS 8
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Changing contents of BS 8002 for earth retaining structures
BS 8002:1994 (134 pp)
Foreword (2 pp)
1. Introduction (6 pp)
2. Data for design (12 pp)
3. Design philosophy, design method and earth pressure (24 pp)
4. Design of specific earth retaining structures (71 pp)
Annexes (*normative)
A. *Graphs for Ka and Kp (8 pp)
B. Traditional design methods for embedded walls (3 pp)
C. Bibliography (4 pp)
DPC BS 8004:2015 (92 pp)
Foreword (1 pp)
1. Scope (1 pp)
2. Normative references (4 pp)
3. Terms and definitions (1 pp)
4. General rules (31 pp)
5. Gravity retaining walls (16 pp)
6. Semi-gravity retaining walls (7 pp)
7. Embedded retaining walls (14 pp)
8. Cofferdams, basements, and strutted excavations (4 pp)
Annexes (*normative)
A. *Deadman anchors (5 pp)
B. Specific formations (1 pp)
C. Archeological finds (1 pp)
Bibliography (3 pp)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
6
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Changing contents of BS 8081 for grouted anchors BS 8081:1989 (177 pp)
Foreword (1 pp)
Introduction (1 pp)
1. Scope (1 pp)
2. Definitions (6 pp)
3. Symbols (2 pp)
4. Responsibilities (1 pp)
5. Site investigation (5 pp)
6. Design (14 pp)
7. Material and components (10 pp)
8. Corrosion and corrosion protection (20 pp)
9. Stressing equipment (1 pp)
10. Construction (10 pp)
11. Testing (13 pp)
12. Maintenance (1 pp)
13. Legal aspects (2 pp)
Appendices (73 pp)
DPC BS 8081:2015 (135 pp)
Foreword (1 pp)
1. Scope (1 pp)
2. Normative references (2 pp)
3. Terms, definitions and symbols (9 pp)
4. General recommendations (5 pp)
5. Limit states (1 pp)
6. Design situations (1 pp)
7. Design considerations (3 pp)
8. Ultimate limit state design (1 pp)
9. Serviceability limit state design (1 pp)
10. Structural design (1 pp)
11. Anchor design (4 pp)
12. Materials (6 pp)
13. Durability (12 pp)
14. Execution (10 pp)
15. Considerations relating to testing (1 pp)
16. Maintenance (1 pp)
17. Reporting (1 pp)
Annexes A-I (informative) (69 pp)
Bibliography (4 pp)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
REV
ISION
OF B
S 80
02
, 80
04
, AN
D 80
81
Outline of talk
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
7
DP
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BS 8081:2015 Code of practice for grouted anchors
I will discuss the status of and main changes in BS 8081:2015 and then concentrate on the clauses associated with the design of the anchor.
Dr Devon Mothersille will then concentrate on durability, execution and the important area of anchor testing.
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Dr Caesar Merrifield (Coffey)
DP
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
8
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BS 8081:2015 Scope for the revision
BSI requirements as set out in 2014
1. ‘The recommendations included in the revised BS 8081 will not conflict in any way with either normative or informative clauses in the associated European standards which supersede BS 8081:1989.’
2. ‘…it is widely acknowledged amongst UK practitioners, that an extensive collection of recommendations and guidance, not covered in the Eurocodes/Euronorms, will be lost when BS8081:1989 is superseded.’
3. ‘The revised document will be compatible with the Eurocodes and effectively fill the gaps in guidance and reference material that currently exist with the new Eurocodes.’
i.e. Complying with the concept of being NCCI
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS 8
08
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ND 2
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5
Changing contents of BS 8081 for grouted anchors BS 8081:1989 (177 pp)
Foreword (1 pp)
Introduction (1 pp)
1. Scope (1 pp)
2. Definitions (6 pp)
3. Symbols (2 pp)
4. Responsibilities (1 pp)
5. Site investigation (5 pp)
6. Design (14 pp)
7. Material and components (10 pp)
8. Corrosion and corrosion protection (20 pp)
9. Stressing equipment (1 pp)
10. Construction (10 pp)
11. Testing (13 pp)
12. Maintenance (1 pp)
13. Legal aspects (2 pp)
Appendices (73 pp)
DPC BS 8081:2015 (135 pp)
Foreword (1 pp)
1. Scope (1 pp)
2. Normative references (2 pp)
3. Terms, definitions and symbols (9 pp)
4. General recommendations (5 pp)
5. Limit states (1 pp)
6. Design situations (1 pp)
7. Design considerations (3 pp)
8. Ultimate limit state design (1 pp)
9. Serviceability limit state design (1 pp)
10. Structural design (1 pp)
11. Anchor design (4 pp)
12. Materials (6 pp)
13. Durability (12 pp)
14. Execution (10 pp)
15. Considerations relating to testing (1 pp)
16. Maintenance (1 pp)
17. Reporting (1 pp)
Annexes A-I (informative) (69 pp)
Bibliography (4 pp) Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
9
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Annexes - BS 8081:2015 Code of practice for grouted anchors
DPC BS 8081:2015(135pp) - ANNEXES (* proposed normative)
A. Indicative Record sheets (5pp)
B. Design of anchors (29pp)
C. Water testing and pre-grouting (1pp)
D. Tendon Young’s Modulus values (1pp)
E. Corrosion (5pp)
F. Corrosion protection (2pp)
G. *Testing (22pp)
H. General considerations on monitoring (4pp)
I. Health and safety (1pp)
Bibliography (5pp)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
DP
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BS 8081:2015 - Main changes
• BS 8081:2015 is now a Code of Practice and not a Standard – i.e. provision of recommendations, possibilities and information only.
• Language in accordance with BSI Rules for the structure and drafting of UK standards; 2012.
• Appropriate EC and EN compliant e.g. with EC7 (in particular DESIGN), BS EN 1537 and (yet to be published) EN ISO 22477-5 - (more from Devon Mothersille on this)
• Terminology introduced to address new concepts of design and processes of testing.
• BS8081:2015 addresses only the design, execution and testing of anchors and not general design application of anchors. (i.e. BS 8081:1989 Appendix D; Overall stability has not been included).
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
10
DP
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BS 8081:2015 – Focus of this section
Design of the anchor (Clause 11 and Annex B)
• Compatibility with limit state design principles
• Definition of EULS;d and Fserv;k
• Relationship between Fserv;k (EC7) and TW (BS8081:1989)
• Implementation of the efficiency factor feff.
• Process of anchor sizing (design of fixed anchor length)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
DP
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BS 8081:2015 - New Terminology – Grout/ground interface
EC7 requires the design of the anchor to consider all limit states.
New terminology;-
EULS;d = Ultimate limit state force to be resisted by the anchor (kN)
Fserv;k = Characteristic value of the maximum anchor force, including effect of lock off load, and sufficient to prevent a serviceability limit state in the supported structure (kN) ≈ TW (BS 8081:1989)
RGG;k = Characteristic ultimate ground/grout interface resistance (kN) ≈ Tf (BS8081:1989)
γGG = partial resistance factor for ultimate ground/grout interface resistance (= 3.0 - Table 2)
ξGG = ground/grout interface correlation factor ( = 1.1 – Cl 11.3.2.5) Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
11
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BS 8081:2015 – Relationship TW and Fserv;k
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS 8081:1989 TW found from overall stability
analysis (L.E.M.) with FoS up to
1.5
i.e TW = 1.5 x T(unfactored SLS condition)
T = the derived axial force that the
anchor provides to maintain
equilibrium (unfactored)
BS 8002:2015 FD = Fserv;k = SD x F x PSLS
≈ 1.5 x PSLS
From L.E.M. analysis
Where;-
PSLS = design axial force
that the anchor provides to
prevent a SLS (i.e.
unfactored)(= T)
BS 8081:2015 Since compliant with BS 8002:2015 through
consideration of stability of supported structure
at serviceability limit state;-
TW ≈ Fserv;k
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BS 8081:2015 – Derivation of RGG;k
𝑅GG;k = 𝑚𝑖𝑛 𝑅GG;calcx feff ;𝑅GG;m
𝝃𝐆𝐆
Where;-
RGG;calc = calculated ultimate ground/grout interface
resistance
RGG;m = measured ultimate ground/grout interface
resistance
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS 8081:2015
12
BS 8081:2015 – Resistance efficiency factor applied to RGG;calc
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Anchor resistance
efficiency factor
implemented for
both sands and
clayey ground
RGG;k = RGG;calc x feff
For Clayey soils
feff = 1.6 x Lfixed-0.57
For sandy soils
feff = 0.91Ltan
Derived from:- BARLEY, A.D. Theory
and practice of the single bore multiple
anchor system.
Proc. International Symposium on
Anchors in Theory and Practice,
Salzburg, Austria.
1995 pp293-301
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BS 8081:2015 – Design of anchor fixed length - grout/ground
𝑅GG;k = 𝑚𝑖𝑛 𝑅GG;calcx feff ;𝑅GG;m
ξGG
𝐹Serv;k ≤𝑅GG;k
γGG
And;-
𝐹ULS;d ≤ 𝑅GG;k
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
𝑇𝑓 = 𝑚𝑖𝑛 𝑇f;calc; 𝑇f;measured
𝑇W ≤𝑇f3.0
This was not expressly
examined in BS 8081:1989
BS 8081:2015 BS 8081:1989
13
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BS 8081:2015 – Concluding remarks
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Objectives achieved in revision
• Reduction in size of document
• NCCI with respect to appropriate ENs and ECs
• Maintain current practice of sizing fixed anchor
lengths by single stress reduction factor (FoS?)
• Retained and updated valuable information from
BS8081:1989 in Annexes as much as possible
• Incorporated Testing Annex to provide guidance
pending the publication of EN ISO 22477-5
REV
ISION
OF B
S 80
02
, 80
04
, AN
D 80
81
Outline of talk
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
14
DP
C B
S 80
81
:20
15
BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution
Considerations relating to testing
Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
To create a document that is compatible
with EC7
The technical authors’ essential objectives in revising BS8081:1989:
Avoid alienating the UK ground anchor
industry
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
15
DP
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability Execution
Considerations relating to testing
Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
DP
C B
S 80
81
:20
15
BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS8081:1989
‘Section 7: Materials and components’
‘Section 8: Corrosion and corrosion protection’
DPC BS8081:2015 retains essential recommendations with 25% reduction in word count (cross-reference made to BS EN 1537:2013 throughout)
‘Section 12: Materials’
• grouts
• tendons
• encapsulations
• anchor head
‘Section 13: Durability’
• information and figures relating to Double Corrosion Protection retained
• information on nature of corrosion moved to Annex E (Corrosion) and Annex F (Corrosion protection)
16
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution Considerations relating to testing
Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
DP
C B
S 80
81
:20
15
BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS8081:1989
‘Section 10: Construction’
DPC BS8081:2015 retains the essential recommendations with 25% reduction in word count (cross-reference made to BS EN 1537:2013 throughout)
‘Section 14: Execution’
• drilling
• storage and handling of tendons
• installation
• grouting
• stressing – equipment (e.g. hydraulic jacks, load cells and gauges)
17
DP
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution
Considerations relating to testing Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
DP
C B
S 80
81
:20
15
BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Extract from clause 3.2 DPC BS8081:2015 NOTE Regarding the relationship between the ‘Working load of anchorage’ Tw (BS 8081:1989, Clause 3) and the characteristic value of the maximum anchor force , FServ;k, the design and testing of grouted anchors in the UK was traditionally based on a specified ‘working load’ termed Tw. BS 8081:1989 Clause 2.21.7 defines the working load as ‘the safe load (Tw) of the anchor’ , the magnitude of which is routinely derived from limit equilibrium stability analysis of the anchored structure. In order to allow for load losses (a large component of which was historically due to relaxation of prestressing steel), it has been routine practice that anchors have been locked off at 110%Tw. This took account of the fact that relaxation in prestressing steels could account for up to approximately 9% prestress loss. In situations where the lock -off load is set at 110%Tw, and no greater load is reasonably expected during the service life of the anchor, then Tw can be taken as equivalent to FServ;k /1.1, since, by definition, FServ;k includes the effect of the lock -off load. However, as it is currently acknowledged that modern prestressing steels account for prestress losses of less than 1.5%, a lock off load of about 102%Tw might be more appropriate. In the context of this code of practice, it is therefore adopted that Tw approximates to the maximum characteristic anchor force FServ;k.
In the context of this code of practice, it is
therefore adopted that Tw approximates to
the maximum characteristic anchor force
Fserv;k
18
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Annex G: Testing
Salient points
• Procedures for stressing and testing moved to Annex G
• Basic structure similar to that of BS8081:1989
• The basis of the revision centres on the relationship; ‘Tw’= Fserv;k
• Proof load defined in BS EN 1997-1:2004+A1:2013
• No distinction made between temporary and permanent anchors from a resistance standpoint
• Proving tests are now called investigation tests in accordance with EC7
• All acceptance criteria for investigation, suitability and acceptance tests are referenced to UK NA to EC7 (NA+A1:2014)
• Observation times have been reduced;
• Investigation tests; load-time data – 10 days reduced to 3 days
• Suitability tests; load-time data at Fserv;k – 10 days reduced to 1 day and in the event of non-conformance, 30 days observation reduced to 3 days
• Apparent tendon free length criterion – lower bound limit relaxed from 90% to 80%
DP
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution
Considerations relating to testing
Maintenance
Reporting Annexes A-I (informative)
Closing remarks
19
DP
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
DPC BS8081:2015, Section 16 Maintenance
Subject to minor revision to incorporate reference to published literature covering the grading of anchors heads subject to corrosive degradation
DPC BS8081:2015, Section 17 Reporting
Subject to minor revision to incorporate the concept of the Geotechnical Feedback Report (GFR) or close-out report as per DPC BS8002:2015 and DPC BS8004:2015.
This report should include;
• a record of anchor construction and any changes to the design
• results of monitoring and testing conducted during construction
DP
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:20
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BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution
Considerations relating to testing
Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
20
DP
C B
S 80
81
:20
15
BS 8081:2015 Code of practice for grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
DPC BS8081:2015 – Annexes
Annex A – Indicative record sheets
Annex B – Design of anchors
Annex C – Water testing and pre-grouting NOTE additional section on post-grouting of anchors to be added to Annex C
Annex D – Tendon Young’s modulus values
Annex E – Corrosion (reduced in size by 15% from original text)
Annex F – Corrosion protection (reduced in size by 41% from original text)
Annex G – Testing
Annex H – General considerations on monitoring
Annex I – Health and safety
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BS 8081:2015 Code of practice for grouted anchors
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This part of the presentation will cover:
Brief introduction
Sections within DPC BS8081:2015;
Materials
Durability
Execution
Considerations relating to testing
Maintenance
Reporting
Annexes A-I (informative)
Closing remarks
21
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BS 8081:2015 Code of practice for grouted anchors
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Closing remarks
• The drafting of DPC BS8081:2015 was carried out within strict guidelines and time constraints stipulated by BSI
• The overall objective was to retain the information, within the original document, considered essential to the future of ground anchor practice
• It was explicitly specified that the revised document should contain non-contradictory complimentary information
• The revised document is compatible with EC7 and associated Euronorms
• In the absence of EN ISO 22477-5, Annex G will provide the necessary guidance on testing of anchors
• The acceptance criteria for the testing of anchors are referenced in the UK NA to EC7
• The structure and layout is comparable with BS8004 and BS8002 and facilitates the structure to be adopted in the revision of EC7 in 2020
• The document is still evolving, an internal review by the technical authors has generated 99 comments/amendments
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Outline of talk
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
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22
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BS 8004:2015 and BS 8002:2015, Codes of practice for …
Foundations (101pp) Earth retaining structures (92pp)
Foreword (1pp)
1. Scope (1pp)
2. Normative references (4pp)
3. Terms and definitions (1pp)
4. General rules (25/31pp)
5. Spread foundations (11pp) 5. Gravity retaining walls (16pp)
6. Pile foundations (42pp) 6. Semi-gravity retaining walls (7pp)
7. Embedded retaining walls (14pp)
8. Cofferdams, basements, and strutted excavations (4 pp)
Annexes (*normative)
A* Underpinning (4pp) A* Deadman anchors (5pp)
B* Helical pile foundations (4pp) B. Specific formations (1pp)
C. Specific formations (2pp) C. Archaeological finds (1pp)
Bibliography (5/3pp) Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
General rules – key topics for BS 8004
Ground investigation
Minimum number and depth of ‘exploration points’ for low-rise buildings
Ground parameters
Suggested values for weight density of coarse and fine soils and fill
Updated guidance on selecting cv for coarse and fine soils
Standardizing terminology for stiffness values (secant, tangent, small-strain, large strain)
‘Default’ expressions for Gsec and G0 (‘in the absence of reliable test values’)
Partial factors
Proposes ,cv = 1.0 (to overcome ambiguity in Eurocode 7)
Reporting
Confirms Eurocode 7’s requirements for GIR and GDR
Recommends production of ‘Geotechnical Feedback Report’ (aka ‘close-out report’)
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23
General rules – key topics for BS 8002
General rules nearly identical to BS 8004
Ground investigation
Spacing of ‘investigation points’ ≤ 20 m along wall ‘unless ground conditions are sufficiently uniform to justify a greater spacing’
For embedded walls, depth of investigation ≥ 2H for unsupported or ≥ H for supported structure
Actions
Simplified loading model for traffic next to bridges
Earth pressure model from compaction theory
Design of embedded walls
Clarifies application of partial factors from Design Approach 1, Combination 1 (i.e. apply 1.11 to variable actions and 1.35 to effects of actions)
Re-introduces model factor on prop/anchor loads, depending on method of analysis
Clearly maps design effects of actions from retaining wall design to design actions used for subsequent anchor design (FULS,d, FServ,d, FServ,k)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
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§4.2
.1.1
Ground investigation
Ground investigations should conform to BS EN 1997-2 and BS 5930
Number of investigation points (n)
• High-rise buildings/industrial structures, conform to B.3 of Eurocode 7 Part 2
• Low-rise buildings, should satisfy (A = plan area of foundation):
low-rise building/housing [is] a building of not more than three storeys above ground intended for domestic occupation and of traditional masonry construction (for
example: detached, semi-detached, and terraced housing or flats). Also includes certain single-storey, non-residential buildings
BS 8103-1:2011
Depth of investigation (za)
• High-rise buildings/industrial structures, conform to B.3 of Eurocode 7 Part 2, i.e.:
• Low-rise buildings, should satisfy (bF = smaller side length of foundation on plan):
2
2 2
3 for 300
100 for 300
A mn
A m A m
greater of 3 or 6a Fz b m
greater of 2 or 3a Fz b m
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24
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FIG
UR
E 2
Suggested values for weight density of coarse and fine soils
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
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TA
BLE 1
Values of ang, PSD, and dil to obtain φ'pk,k and φ'cv,k
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25
BO
LTON
(20
14
, PER
S. CO
MM
.) Origin of the 30 + A + B + C formulation for cv,k
“The 30 + A + B + C formulation was never properly documented; no reference was available. I think it may originally have been proposed by Sowers and Sowers, but I
cannot verify that. I believe it was drafted by an early CP2 revision committee member who later died! The committee adopted it in the final 1994 revision which
was BS 8002 … even though my 1986 paper was then in existence of course.
“Actually, the 30 + A + B formulation for critical state friction angle is quite useful; it is just a pity there is no clear science behind it!”
Bolton (2014, pers. comm.)
“I attach a paper by Santamarina, who is very reliable. His Fig 2 shows a black line
from Terzaghi et al 1996 which is the best expectation for pure clays without
inclusions, together with data of large of cv at large IP for some clays with a
profusion of faecal pellets, foraminifera, or other micro-lumpy inclusions.”
Bolton (2014, pers. comm.)
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FIG
UR
E 3
Terminology for stiffness parameters
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26
BS 8
00
4:2
01
5 §4
.12
.3
Geotechnical Feedback Report
The Geotechnical Feedback Report is also known as a “close-out report”
On completion of the works, a Geotechnical Feedback Report (GFR) should be
prepared that covers the following broad classes of information:
• a record of construction and any changes to its design; and
• results of monitoring and testing conducted during construction.
The Geotechnical Feedback Report should be tailored to suit the size and
complexity of the works.
The record of construction should include, as appropriate: (list of items follows)
The results of monitoring and testing should include: (list of items follows)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Shallow foundations – key topics
Calculation models for shallow foundations
Bearing capacity formulation
Effective stress method based on Poulos, Carter, and Small (includes depth, ground inclination, and soil rigidity factors)
Total stress method based on Salgado et al.
Presumed bearing resistance values removed
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27
N values compared
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Pile foundations – key topics
Calculation models for pile foundations
Based on ground parameters
Coarse soils – effective stress model (Nq based on Fleming et al., depends on pile type, density index, and stress level)
Fine soils – total stress model ( linked to pile type, shear strength, and stress level)
Based on field tests
Cone penetration tests – factors for base and shaft (cb and cs)
Standard penetration tests – factors for base and shaft (nb and ns)
(where the factors depend on soil and pile type)
Guidance on downdrag
Treatment of downdrag as an additional force, not as negative resistance
Presence of downdrag in ULS and SLS verifications
Structural design of cast-in-place concrete piles without permanent casing
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28
BS 8
00
4:2
01
5 F
IGU
RE 5
Suggested values for Nq (based on Fleming et al. 2008)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
BS 8
00
4:2
01
5 T
AB
LE 12
Values of empirical coefficients cs and cb
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
29
BS 8
00
4:2
01
5 F
IGU
RE 6
Downdrag (aka ‘negative skin friction’)
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
Retaining walls – key topics
Simplified load model for vehicle traffic next to bridges
Replace patch loads with blanket surcharge
Guidance on compaction earth pressures
Based on Ingold model
Model factor on prop/strut/anchor loads
Depends on calculation model for retaining wall design
Explicitly stated where the factor goes – important to avoid confusion in acnhor design
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30
Imposed loads on vehicle traffic areas next to bridges
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Earth pressure from compaction theory
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31
Model factor for load-effects in props, struts, and anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
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Outline of talk
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
32
Summary of key points
The revised British Standards – 8004, 8002, and 8081 – are intended to:
• Complement (and not contradict) the current version of Eurocode 7 and its National Annexes
• Provide clarification of Eurocode 7’s requirements, where required
• Be future-proof against significant changes to Eurocode 7 expected in 2020 or thereabouts
• Update 20-30 year old technical information contained in the withdrawn or obsolete codes
• Work together as a coherent set of modern standards
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
TIM
ETAB
LE
What happens next?
24th March 2015
Review ends – comments are collated by BSI and sent to authors
14th April 2015
Steering Group meets to discuss comments on BS 8081
28th-29th April 2015
Steering Groups meet to discuss comments on BSs 8004 and 8002
End May 2015
All comments resolved – proceed to publication
End June 2015
Obtain approval of revised standards (B/526)
Publication of 2015 versions of BSs 8004, 8002, and 8081
Thanks to:
Brian Simpson (Chair of B/516)
Tony Suckling (Chair of Steering Group for BS 8004)
Paul Thurlwell (Chair of Steering Group for BS 8002)
Mick Gavins (Chair of Steering Group for BS 8081)
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33
HTTP://D
RA
FTS.BSIG
RO
UP.C
OM
DPC period is about to close …
Please visit BSI’s draft standards website to access the DPCs:
http://drafts.bsigroup.com
The deadline for comments on these drafts is:
Tuesday 24th March 2015
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
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Any questions?
10 mins
15 mins
15 mins
15 mins
5 mins
Andrew
Purpose/structure of the revised British
standards
BS 8004 – Foundations and BS 8002 – Earth retaining structures
Summary of key points
Caesar
BS 8081 – Grouted anchors
Devon
BS 8081 – Grouted anchors
Eurocode 7 Workshop on NCCI ©2015 Geocentrix Ltd, Coffey, and Geoserve Global. All rights reserved
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