BS 80811989 Code Of Practice For Ground Anchoragespdf
Rosette Allaband
Ground anchors have been playing an important role in reinforcing dykes, underground, stabilizing structures of earth retaining walls, subway stations, and anchoring abutments of bridge or in sea port, etc. In Vietnam, the design of ground anchors is generally based on the international design guidelines, in particular the Eurocode. As there is a diversity of current design practices in different countries, it is necessary to carefully verify and validate an international design of ground anchor before adopting it to Vietnam. This paper aims at presenting a series of full-scale pullout tests of ground anchors recently performed in several projects in Hanoi and Ha Long city, Vietnam. The testing results in terms of the ultimate load-holding capacity, the pullout performance and the skin friction are discussed and compared with the French design practice TA95 in order to evaluate as well as to improve its applicability in Vietnam.
This paper presents full-scale pullout ground anchor tests conducted in some types of alluvial soil formations in Egypt, including silty sand, sandstone, and clay soils. The tests were carried out up to failure loads in order to estimate the ultimate load of friction bearing capacity for each soil stratum. Moreover, an elaborated site investigation program was performed to predict the in-situ soil properties. This research campaign is a part of construction of residential and commercial complex which comprises six underground basements, and the site is located in a vital and highly traffic zone of Heliopolis, Cairo, Egypt. Field test setup and installation method of the full-scale ground anchors were explained. The results of the field tests were compared against the design values of unit skin friction resistance given by the well-known codes of practice (AASHTO; BS 8081; and Canadian Foundation Engineering Manual) and the literature for design of ground anchorage. The comparison showed that the values of skin friction resistance for anchorsoil/rock interface given in AASHTO (2004) and BS 8081 (1989) can be employed for determination of pullout capacities of ground anchors installed in Egyptian soils with a good reliability.
2 Revival of withdrawn/obsolete geotechnical standards Several important geotechnical codes of practice were withdrawn in March 2010 on the introduction of the Structural Eurocodes, including: BS 8004:1986, Code of practice for foundations BS 8002:1994, Code of practice for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 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 ) Relationship between British Standards and Eurocode 7 MODIFIED AFTER BOND AND HARRIS (2008) 2
3 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 and -2) BS 8002, 8004, AND 8081 FOREWORDS Eurocode 7 timeline
17 BS 8081:2015 Code of practice for grouted anchors 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 BS 8081:2015 Code of practice for grouted anchors Extract from clause 3.2 DPC BS8081:2015 NOTE Regarding the relationship between the Working load of anchorage T w (BS 8081:1989, Clause 3) and the characteristic value of the maximum anchor force, F Serv;k, the design and testing of grouted anchors in the UK was traditionally based on a specified working load termed T w. BS 8081:1989 Clause defines the working load as the safe load (T w ) 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%T w. 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%T w, and no greater load is reasonably expected during the service life of the anchor, then T w can be taken as equivalent to F Serv;k /1.1, since, by definition, F Serv;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%T w might be more appropriate. In the context of this code of practice, it is therefore adopted that T w approximates to the maximum characteristic anchor force F Serv;k. In the context of this code of practice, it is therefore adopted that T w approximates to the maximum characteristic anchor force F serv;k 17
21 BS 8081:2015 Code of practice for grouted anchors 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 noncontradictory complimentary information The revised document is compatible with EC7 and associated Euronorms In the absence of EN ISO , 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 Outline of talk 10 mins Andrew Purpose/structure of the revised British standards BS 8004 Foundations and BS 8002 Earth retaining structures Caesar BS 8081 Grouted anchors Devon BS 8081 Grouted anchors REVISION OF BS 8002, 8004, AND mins Summary of key points 21
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 (F ULS,d, F Serv,d, F Serv,k ) Ground investigation Ground investigations should conform to BS EN 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): 2 3 for A 300m n 2 2 A 100m for A 300m 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 :2011 DPC BS 8004: Depth of investigation (z a ) High-rise buildings/industrial structures, conform to B.3 of Eurocode 7 Part 2, i.e.: z greater of 3 b or 6 m a F Low-rise buildings, should satisfy (b F = smaller side length of foundation on plan): z greater of 2 b or 3 m a F 23
Brussels, 18-20 February 2008 Dissemination of information workshop 1 Workshop Eurocodes: background and applications Brussels, 18-20 Februray 2008 Design of pile foundations following Eurocode 7-Section
The specification of design should conform to BS EN 1997-1:2004+A1:2013, 8. Inaddition, the following should be considered:a) the disposition and classification of the various zones of soil and rock, both vertically and horizontally, and the elements of construction that could be involved in a limit state event;b) effects due to the environment within which the design is set, such as: 1) scouring, erosion and excavation, leading to changes in the geometry of the ground surface; 2) weathering; 3) the presence of gases emerging from the ground; 4) other effects of time and environment on the strength and other properties of materials;c) cavities due to mining or other causes;d) possible changes in the groundwater levels due to temporary or permanent modification;e) for anchors installed in or near rock, the consideration of: 1) interbedded hard and soft strata; 2) faults, joints and fissures; 3) solution cavities such as swallow holes or fissures, filled with soft material, and continuing solution processes.NOTE To assist users of this code of practice, flow charts (see 7, Figure 2 and Figure 3)are included, covering the preliminaries to design, detailed design and construction, andmaintenance. Where it is appropriate, key steps are cross-referenced to sections or clausesin the code of practice so that the user may consult the detailed recommendations.
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