Annexes

A Checklist for construction supervision and performance monitoring 93 B A sample analytical method for bearing resistance calculation 94 C A sample semi-empirical method for bearing resistance evaluation 95 D Sample methods for settlement evaluation 96 E A sample method for deriving presumed bearing resistance for spread foundations on rock 97 F A sample calculation model for the tensile resistance of individual or grouped piles 98 G Sample procedures to determine limit values of earth...

B Fully excavated

Figure E15.4 Earth pressure distributions from FREW Case C analysis Figure E15.5 Results from FREW SLS analysis E15.5 Comments It is of interest to compare the results of the FREW analyses with the simpler calculations represented by Column 1 ofTable E15.1, and represented by Figure E15.3. These give a maximum bending moment which is 26 higher than adopted in the design, with a prop force 20 lower. In general, it would be safe to design the sheet pile section using these simpler calculations,...

Bs

Derive bending moments and internal forces directly from the equilibrium calculations and use these as both ultimate arid serviceability values. In principle, check ultimate strength of the structure for earth pressures derived in the same way, but with the possibility of greater (factored) surcharges if these are required by other codes. Also check the possibility of larger earth pressures in the working state of the structure (due to compaction, pre-consolidation, etc), and, if relevant,...

C

British designers seldom take advantage, explicitly, of the difference between triaxial and plane strain effective strengths. This is common in Danish practice, however. See comment on 3.3.1. Analysis of observed behaviour is recommended here. C3.3.9 Quality and properties of rocks and rock masses C3.3.9.1 Uniaxial compressive strength and deformability of rock materials C3.3.10 Permeability and consolidation parameters Although this section comments on parameters rather than individual tests,...

Basis Of Geotechnical Design

A structure shall be designed in compliance with the general design principles given in ENV1991-1 Eurocode 1 'Basis of Design'. Section 2 sets out the approach to be taken in geotechnical design, including, but not restricted to, design based on calculation. It is based on the limit state approach and relies on Eurocode 1 for definitions of some basic terms. It cannot be used without Eurocode 1. Part B of this commentary discusses many of the concepts which underlie the drafting of Section 2....

Design and construction considerations

The cross reference to 2.1 is thought to be incorrect. It should probably be 2.4.1. C8.5 Determination of earth and water pressures C8.5.1 Design earth pressures Many of the subclauses in this clause refer to states of earth pressure which are not at limiting active or passive values. These are generally not used in sizing the geometry of retaining structures. However, they are relevant to assessment of ground movement, generally serviceability limit states, and to structural design for both...

Design methods CP

This paragraph makes it clear that all pile design calculations must be related, directly or indirectly, to the results of static load tests. Where the design is based directly on static load tests, it must also be shown by calculations that the results are consistent with general experience. Pile designs may also be based directly either on analytical calculations or on dynamic load tests however, in these cases, the calculation methods or interpretation of the dynamic load tests must have...

Fundamental requirements C Fill construction

This sub-section covers selection, placement, compaction and checking of fills. It provides a checklist of items which should all be covered in specifications for earthworks. As for natural ground, design calculations involving fill materials require the assessment of characteristic values of the material properties. At the time of design, the fill to be used may not have been identified, though its properties will be specified. The assessment of characteristic values should follow the...

General CP

Section 7 of the ENV was drafted before the text on Cases B and C was prepared in Subclause 2.4.2. There is therefore an incompatibility between these two sections. In principle, Section 7 is consistent with Case C, but note that 2.4.3(12)P states that the partial factors for soil strength parameters given in Section 2 are not to be used for piles. All three Cases A, B and C should be checked, though experience will quickly show that for most common situations Case C always governs the...

Kcd

The second grammatical paragraph in this 'paragraph' is rather out of place. A separate section on special situations, such as cyclic loading, would perhaps be desirable in a future version of EC7. C7.5.2.1 Loading procedure C7.5.2.1(1)P It is clear from this paragraph that many pile load tests may not be taken to failure. Only for trial piles is it required that 'conclusions can be drawn' about ultimate failure load. This is not really consistent with the design methods given later (eg...

Limit states

The list of limit states for spread foundations does not include failure by overturning. This is considered to be a form of bearing resistance failure, in the ultimate limit state, and to be covered by 'excessive settlements' in the serviceability limit state. The list includes both combined failure in ground and in structure and structuralfailure due tofoundation movement. The first of these is intended to refer to situations where a failure mechanism forms in the ground and the structure is...

Pile Foundations

See the general comments at the start of Section 6. This section of Eurocode 7 is quite long and designers of piles will usually only need to refer to parts of it. Its contents can be summarised as follows. 7.1 to 7.4 Introductory 7.9 Structural design of piles 7.10 Supervision of construction. Clauses 7.1 to 7.5 will not be particularly controversial to British designers. Thus, for design of compression piles, the only clause which introduces unfamiliar requirements is 7.6. As noted under...

Piles in compression

Paragraph (1)P reflects the more general Clause 7.2 but selects the specific limit states relevant to compression piles. It is noted that an ultimate limit state might occur in a supported structure due to displacement of the piled foundation, even if the piled foundation has not itself reached its ultimate capacity. Paragraph (2) states that this problem should be addressed, when necessary, by using a factored load-settlement curve. Figure C7.1 shows an example of how a measured...

Serviceability limit state

The intention of this subclause is to require careful consideration of likely displacements without demanding unnecessary calculation or encouraging dubious attempts at calculation which might be misleading. Figure C8.4 shows a flow chart for the decisions required. The draft of Eurocode 3 Part 5 (prENV 1993-5 1997) contains Figure C8.4 Flow chartfor serviceability limit state displacements (Subclause 8.7.2) additional information on assessment of ground movements, particularly for sheet pile...

Serviceability limit state design

The relationship of ground movement to ultimate and serviceability limit states is discussed in B2.1. This clause, under the heading of serviceability limit state, is equally applicable to ultimate limit states caused by ground movement remote from shear failure. The only exception to this is 6.6(2)P, since for ultimate limit states ULS design loads must be used. In Paragraph 8.4(2), for retaining walls, it is stated that the design methods and factors of safety required by this code for...

Spread Foundations

This is the first of four sections which deal with the geotechnical design of the different elements of construction. The layout of these sections is the same in each case, consisting of a A general statement of scope. b A list of limit states to be considered. The code encourages an orderly approach to calculations, first listing the cases to be considered and the loads to be applied. C Actions and design situations to be considered, d Design and construction considerations. These are mainly...

Structural design of piles

Clause 2.4 requires calculations for all 3 cases A, B and C, as discussed earlier under C7.3.1(1)P. An example is given in E12. The calculation method presented in Annex F shows how the design tensile force in the pile might vary over the length, reducing towards the base of the pile. This is based on design soil strength, but makes no allowance for soil stiffness. In extreme cases, where the pile extends over most of its length through highly deformable ground but reaches very stiff ground, it...

Structural design of spread foundations

As for the geotechnical calculations, structural calculations should in principle be carried out for all three cases A, B and C. However, in most situations it will be obvious that the loading of Case B governs the structural design of spread foundations. The geometry of the foundation may well be determined by Case C, however. It is important that the structural design is then carried out for the piece of structure which will actually be built. This implies that Case B loading must be applied...

Supervision Of Construction Monitoring And Maintenance

A Supervision of construction, monitoring and maintenance shall be undertaken as appropriate. The term 'as appropriate' is repeated many times. In many respects, the whole section is simply a check list reminding engineers of many of the items which might be appropriate in various circumstances, b Designers must specify what is appropriate and must communicate this in specifications and record it in the geotechnical design report. C Supervision of construction, monitoring and maintenance must...

Ufr

This paragraph is out of place Annex F refers primarily to structural design of piles. An example of the use of Annex F is given in Ell. C7.7.3 Vertical displacement C7.7.3(2) In cases where very long tension piles are used, the elastic stretching of the piles themselves may exceed serviceability limits. It is sometimes necessary to increase reinforcement to prevent this. In some designs mild steel reinforcement, working at relatively low stresses, is adopted...

Uoc

EC7 has not been well developed for situations in which ground displacement is the action. In particular, no values are given for partial factors for situations where ground strength acts in a manner detrimental to the condition of the structure. An analysis generally consistent with 2.4.2 can be carried out for Case B by calculating the unfactored tension in the pile and multiplying this by 1.35 for ultimate limit state design. Lower bound values should be taken for any variable compressive...

Ch

This paragraph breaks the CEN rules in that a reference is made to a document which is not a CEN or ISO publication. The text will probably therefore be changed in the final version of Eurocode 7. The paragraph refers to the paper in the 'ASTM Geotechnical Testing Journal', (ASTM (1985)), 'Axial pile loading test, suggested method' (sic, actually 'Axial pile loading test - Part 1 static loading'). This was written before the 'Specification for piling and embedded retaining walls' (ICE (1996)),...

Ck

The need for high characteristic values in problems involving downdrag is noted under 7.3.2.1(1)P. When an interaction analysis is used to determine load distribution in a large group of piles, the effect of both hard spots and soft spots should be considered, represented by upper and lower characteristic values of strength and stiffness parameters. It can often be argued that the geotechnical design should not be changed to account for these, but there may be need to consider them in...

Comment

For simple design to BS 8110, the BS 8002 requirement will mean that further factors of about 1.4 must be applied to the moments and shears. This is more severe than traditional design or EC7. Note that compaction, pre-consolidation pressures etc are not included in the equilibrium calculations, but only in the structural strength calculations. It is assumed that if these high stresses push the wall towards instability they will be relieved with relatively little movement. Both BS 8002 and EC7...

Contents

D1 THE USE OF EUROCODE 7 OUTSIDE THE UK 109 D1.2 Other European NADs 109 D 1.3 Other overseas usage of Eurocode 7 111 D2 FUTURE DEVELOPMENT OF EUROCODE 7 113 D2.1 The Eurocode system 113 D2.2 Eurocode 7 Part 1 113 D2.3 Eurocode 7 Parts 2 and 3 113 D2.4 National variation of Eurocode 7 114 D3 RESEARCH AND DEVELOPMENT NEEDS 115 D3.1 Application of partial factors 115 D3.2 Serviceability and deformations 115 D3.3 Statistics and probability methods 115 D3.4 Economy of design 116

Cp

The third item in the check list relates to depth of penetration of frost. This is dealt with in BS 8004 (3.2.9.1) by the requirement that all foundations shall be placed at depths not less than 0.45 m. The checklist requires that future excavations for services close to the foundation should be considered. It does not specifically say that future excavations for other purposes should be considered, though this would be equally relevant. However, it does not demand that spread foundations be...

CP and

Usually, the load on a pile under test is only measured at the top of the pile. However, it is often possible to make a reasonable assessment of the separate components of base and shaft resistance. Paragraph (9) suggests that the ratio of the base and shaft components might be derived by calculation, though their sum is based on the measured results. The effect of an error in this estimate is shown in Figure C7.2. The error in the design resistance Rd is plotted against the true ratio of shaft...

CP Error

The cross-reference to 2.4.5 should be 2.4.6. limit states This is an important subclause, particularly if the comments in C8.6.6 are applied. However, EC7 gives little detail. The user is required to find characteristic values of stiffnesses both for the ground and for structural elements. For structural elements, EC1,5(2) specifies that the characteristic values of stiffness parameters should be mean values. This is accepted for structural stiffnesses but is over-ridden in EC7 for ground...

Pto

The standard formulae for bearing capacity do not easily take account of soil layering or discontinuities. These paragraphs encourage caution for such cases, and (5) offer a simple calculation which may be very conservative in some cases. Semi-empirical methods are those which rely on an established correlation between a test result and the ultimate bearing capacity. It is important not to extrapolate correlations beyond 'comparable experience' as defined in 1.4.2(1)P. Annex C provides an...

Application of partial factors

It was noted in D2.2 that an acceptable scheme of applying partial factors is still not agreed. Although this debate might temporarily be curtailed by the production of the Euronorm, it will doubtless recur until broad agreement is found. Engineers with practical knowledge of geotechnical design, together with a broad understanding of the purposes of factors of safety and the options for their implementation should be involved in this debate. The continuing study of both successful geotechnical...

Eurocode Part

During 1997 and 1998, a Working Group set up by CEN TC250 SC7 has been meeting to try to resolve some of the known problems with the ENV, and to review comments received. In early 1998, a mandate is about to be issued to CEN by the European Community which will require the formation of a Project Team, contracted to prepare EC7-1 for EN status. Their work on the text is to be completed by mid-2000, and the EN is to be published as soon as possible thereafter, subject to time required for...

National variation of Eurocode

As this commentary is drafted (early 1998), there is considerable pressure on drafters of Eurocodes to eliminate national variations. It appears likely that boxed values, as such, will not be allowed in the Euronorms. However, it is likely that for EC7 some form of national appendices will be retained, at least giving national values for safety factors. In July 1997, CEN TC250 SC7 passed a resolution requiring that the partial factors remain boxed in Basis of Design. It is foreseen that...

Serviceability and deformations

The limit state approach requires more explicit consideration of serviceability limit states than has been the case previously. In part, this implies that the geotechnical profession must improve its ability to calculate deformations. EC7 therefore provides strong encouragement for continuing research into the deformation properties of soils, and the numerical methods needed to use these. It should not be inferred, however, that EC7 encourages heavy numerical analysis where it is not needed....

Statistics and probability methods

Across Europe, there is considerable interest in the application of statistical methods to geotechnical analysis. The training of British engineers is probably inferior to that of their European counterparts in this respect. It is considered likely that statistical methods, well applied, could add to the geotechnical profession's understanding of uncertainty and safety in design. At worst, it is important that geotechnical engineers ensure that their work is not damaged by spurious, but...

Calculations

The required size of footing was calculated for both cases B and C. For Case B, it is necessary to consider the permanent vertical actions both as favourable and unfavourable. In this example, Case B with the permanent vertical actions favourable was found to be the critical case with a required footing dimension of 5.6 m square. The required dimension for Case C was 5.4 m square. Hence, Case B was marginally critical for sizing of the pad footing (ie critical for geotechnical stability). This...

Case B settlement taken as action

Vertical load, V yG 1.35 (Table 2.1). Any partial factor applied to settlement would have no effect in this case. Partial factors for resistances Shaft resistance, R ys 1.0 (Table 7.2). Partial factor for unfavourable soil strength transmitting effect of settlement to pile 1.0. Hence design downdrag force 94.2 kN. Total design vertical load Fd Vd + Dd VkxyG + 94.2 300x1.35 + 94.2 499.2 kN. Design shaft resistance Rd Rk ys Hence 47.1 x LR 1.0 > 499.2 kN.

Comparative calculations

In CIRIA Report 104, the calculated wall length for simplified hand calculations was 14.6 m, and this was increased to 16.6 m to allow for the simplifications made. Table E14.1, Column 1 shows the results of a calculation based on the same principles, but carried out using the Oasys program STAWAL, so avoiding the need for simplifications in the equilibrium assumptions. The resulting wall length is 15.2 m, lying between the two values of CIRIA 104. The bending moment derived from this...

Data

A structure is to be supported on bored piles. Each pile supports a single column with vertical characteristic loading of Gk 1000 kN (permanent) and Qk 300 kN (variable). Based on this load information and the soil properties shown in Figure E6.1 it is necessary to calculate the required toe level of a 0.6 m diameter bored pile. The following mean relationships for pile resistance will be used, using the subscript ' x' to denote mean, or most probable, ground properties and resistances. The...

Data and load factors

This example considers the bearing capacity of a tall lightweight structure which is subjected to significant horizontal loading (eg a windmill or chimney). The characteristic actions and partial factors are shown in Figure E4.1 and Table E4.1. A moment results from the horizontal load which is applied to the structure at 10 m above the top of the pad footing. The pad footing is 2 m deep and is situated on a dry medium dense sand and gravel layer with < )' 35 and c' 0 kPa. Figure E4.1 Loading...

Data and load factors for E

The pad footing shown in Figure E2.1 is to be designed for a structure with large live load. The foundation stratum is medium dense sand and gravel with characteristic shear strength parameters of < (> ' 35 and c' 0 kPa. The characteristic loading conditions are shown in Table E2.1. Concrete y 24.5kN m3 Sand, < f *(< 35 , Figure E2.1 Spread footing loads and geometry Characteristic actions and partial factors

Data and method

Figure E14.1 shows Example B2 taken from CIRIA Report 104. It requires the design of a cantilever sheet pile wall in a single soil, with differential water pressure across the wall and no surcharge behind the wall. It is considered that the 'moderately conservative' values of CIRIA 104 are equivalent to characteristic values for the soil parameters. Only the permanent works design will be considered here. EC7 does not provide specific requirements for temporary works this point is considered in...

E Design Of Slope In Drained Ground El Introduction

EC7, 9.5 considers the design of slopes and embankments by adopting partial factors for permanent and variable actions and specific ground properties. It states that these factors shall generally be used for verification of ultimate limit states of conventional types of structures and foundations in persistent and transient situations. In C9 it is noted that when considering the Ultimate Limit State for a slope it is only necessary to consider Case C in Table 2.1. It is noted in Paragraph...

Discussion

Provided there is sufficient confidence in the characteristic values of the parameters (cautious values' - see B4 and EC7,2.4.3), only Calculation 1 is needed to satisfy EC7. It demonstrates that the slope is stable when the partial material factors are applied to the soil strength. The results of Calculations 1 and 2 show that the effective cohesion, c', plays a very significant role in the stability of the slope. In Calculation 1 the slope is seen to be stable with a global factor of safety...

Input To Structural Design

OF A PILE IN HEAVING GROUND 144 ElO PILE SUBJECT TO DOWNDRAG 147 E10.3 Characteristic values of forces 147 E10.4 Case CI - downdrag force (D) taken as action 147 E10.5 Case C2 - settlement taken as action 148 E10.6 Case Bl-downdrag force taken as action 149 ElO.7 Case B2 - settlement taken as action 149 E10.8 Conclusion and discussion 149 Ell USE OF ANNEX F IN STRUCTURAL DESIGN E12 PILES IN TENSION DUE TO BUOYANCY EFFECTS E13 DESIGN OF A CONCRETE STEM WALL 154 E13.2 Ultimate limit states 154...

Introduction and data

The ULS design pile load capacity is obtained from a single pile load test using three methods of interpreting the pile load tests to failure. Method A considers the maximum pile shaft capacity by inspection Method B uses Chin (1972) to derive both ultimate shaft and base capacities and Method C uses the results of instrumentation which distinguishes between components of shaft and base resistance. The pile has a 1.02 m diameter shaft and a 2.06 m diameter base. The total length of the pile is...

Method

In this upper limit calculation of the ultimate pile tensile force the pile skin friction is assumed to be fully mobilised along the pile shaft. This is conservative, as mobilised skin friction is known to be related to the shear displacement between pile and surrounding ground. The level at which the cumulative skin friction, starting from the pile base, equals the cumulative skin friction, starting at the pile head, is called the balance point and this is the point of maximum tensile stress...

Method A calculations

Figure E8.1a shows the load-settlement points measured in the pile test, for which the ultimate resistance was 14.2 MN at a settlement shaft diameter ratio of 8 D 10 . The pile shortening line is also shown on Figure E8.1a. This line is the elastic compression of the pile assuming that the total imposed load results in compression of the whole length of the pile shaft. The intersection of this pile shortening line with the pile load-deflection curve is at approximately 6.2 MN (5 5 mm) and it is...

Method comparisons

The results for the three Methods are summarised in Table E8.1. In the table, the displacement that is appropriate to the total resistance in each Method is stated. It is clear that the displacements for Methods A and C are the same (the measured resistance) while Method B is for a larger displacement. In order to calculate the design pile resistance, the shaft and base resistance is expressed as a fraction of the total resistance. This breakdown between shaft and base resistance is then used...

Method Dl

Isotropic elasticity is assumed to apply to this situation. The settlement of the loaded area may be calculated by hand or by using proprietary software. Fadum (1948) presents relationships for the change in vertical stress beneath an uniformly distributed load in the form where q is the uniformly distributed load Ic is the influence factor depending of geometry of loaded area and position of soil element relative to loaded area. Stress changes are calculated for a set of loaded areas all of...

Other design checks

Overall equilibrium must be checked in accordance with EC7,8.6.2, and vertical equilibrium of the wall, with the anchor load, in accordance with EC7, 8.6.5. The length of the anchor must be sufficient to comply with the assumptions made in the design of the retaining wall. In E15, for example, no attention was given to the anchor, so it is necessary that the fixed anchor length is sufficiently remote to have no influence on the earth pressures on the wall. EC7, 8.8.2(7) requires a minimum free...

Required bending resistance

Design methods cannot be compared, however, simply on the basis of the bending moments derived. The design of a sheet pile wall is not complete until the steel section has been chosen, and for this purpose, it is necessary to consider the structural codes with which EC7, CIRIA 104, etc are to be used. EC7 is to be used as part of the Eurocode system with Eurocode 3 (ENV 1993). EC3 Part 5 considers the design of steel sheet piles and is based on concepts of plastic design. For robust sections,...

Ec

Derive bending moments and internal forces directly from the equilibrium calculations and use these as ultimate limit state values. Serviceability is to be checked using unfactored characteristic values of soil properties and loads. (In a formal sense, a factor of 1.0 is applied.) Overdig is not included in this calculation. Also check the possibility of larger earth pressures in the working state of the structure (due to compaction, pre-consolidation etc), and, if relevant, treat these as...

El Introduction

Part E of the commentary consists of worked examples, to which reference is made in the other parts. The examples have been developed to illustrate specific points about the application of EC7, and this also governs the amount of detail presented. All examples follow the rules of EC7 and are presented in a step by step approach demonstrating the checks that are required in carrying out a conforming design. Some include more detailed explanation than would normally be found in design...

Foreword

This Commentary consists of guidance and recommendations related to draft Eurocode 7 Part 1 - DD ENV 1997-1 1995. Its contents are necessarily ofa general nature, and responsibility for the application of the commentary, in particular engineering projects, remains with the user. Brian Simpson, Arup Geotechnics Richard Driscoll, BRE S Desai, Department of the Environment, Transport and the Regions DI Bush, The Highways Agency P R J Morrison, Arup Geotechnics C A Raison, Keller Ground Engineering...

Info

Each column in the table represents a continuous calculation. Partial factors are applied to the soil strength (tanc))' in this case) and to the surcharge load p. Values of the coefficients of earth pressure, K, and of the bearing capacity factors, N, are then derived directly from EC7 Annexes G and B, using the design values of ( )'. The base width B is required to provide equilibrium between the lateral earth pressures and available bearing resistance. This may be achieved by hand calculation...

Isid Isik Ys

The required pile length for the two load cases can then be calculated using the following equations, with the appropriate design resistances design base resistance Rbd < lbd Ab (Ab base area nr2) design shaft resistance Rsd I qsik. Asi (Asj shaft area for length 'i' of shaft kD.L,). The calculations in Table E6.2 show that Case C is critical in this case for the sizing of the pile.

M

Curve M shows the measured load-settlement plot for a test on a single pile. By inspection, it is assessed that the shaft resistance of the pile is 2.6MN and the ultimate base resistance is 1.6MN. Curve K is the characteristic load-settlement plot, obtained by dividing the force on Curve lyi by 1.5 (from Table 7.1). This is used without further factors for ULS Case B and for SLS design. Curve C is derived from Curve K for ULS design to Case C. The shaft resistance is divided by 1.3 and the base...

N

Figure C6.2 Footing in ground subjected to seepage Figure C6.2 shows a situation of steady seepage in which water pressures are fixed (and therefore are actions) but are not hydrostatic. In this situation, application of the factors yG 1.35 in Case B will lead to an increase in hydraulic gradient. However, the 'single source' principle would also require that 1.35 be applied to the weight of the soil, so it is likely that the more critical case is yG 1.0, with the soil water system acting...

R

Arrows show hydrostatic water pressures (vertical components only). Those acting on the footing are included in Vd, whilst those alongside the footing augment Rd. In this (undrained) case, Rd is a total force acting on the base, which includes both the hydrostatic pore pressures and excess pore pressures due to undrained shearing. Arrows show hydrostatic water pressures (vertical components only). Those acting on the footing are included in Vd, whilst those alongside the footing augment Rd. In...

SoLr m

Design force for concrete shaft Fd 499.2 kN. E10.8 Conclusion and discussion The results of the calculations are summarised in Table E10.1. It is necessary to satisfy both cases B and C, but the choice of force or displacement as the action is open to the designer. A pile with a penetration into the bearing stratum of LR 10.88 m and structural capacity of Fd 499.2 kN would therefore comply with the code. This combination of LR and Fd is derived from calculations CI and B2, which are not...

Z

Stiff clay fk 24 c' 0 E 30 MPa Figure E15.1 Propped embedded wall characteristic conditions A brief account of a suitable set of calculations for this design will first be presented. Following this, a more detailed description of comparative calculations carried out for a slight variant on this problem will be given. Attention has been concentrated on Frodingham (Z) sections in order to avoid the long-standing dispute about shear transfer in the clutches of Larssen (U) sections. This is noted...

E Applications Of Annex D Sls Settlement Check E Data

Considering the load case for the pad footing in E2, it is necessary to calculate the settlement of the footing for SLS conditions. The ground conditions at the footing are medium-dense sand and gravel to a depth of 7 m with an average SPT value of 20. This sand and gravel layer overlies a 13 m depth of overconsolidated clay. The characteristic Young's moduli of these two layers are E' 50 MPa for the sand and gravel and E' 15 MPa increasing to 32 MPa at 13 m below the clay surface for the clay....

Method C calculations

During the loading cycle, the test pile was instrumented at locations along the shaft and base. The load cells showed a shaft resistance of 6.7 MN and a base resistance of 7.5 MN at 8 D 10 . The results for the shaft and base resistances are shown in Figure E8.1c. In order to calculate the design resistance of the pile from the measured resistance in a pile load test, Paragraphs 7.6.3.2(6)P and 7.6.3.2(10)P must be used. Paragraph 7.6.3.2(6)P considers the characteristic resistance of the pile...

Ground investigation report

It is a requirement of the code that a Ground Investigation Report be produced. This will often be incorporated into the Geotechnical Design Report described in Clause 2.8. The Ground Investigation Report is to include both factual material and a geotechnical evaluation of the information, stating the assumptions made in the derivation of the geotechnical parameters. These parts may be combined into one report or divided into several reports. The code makes no comment on the various parties who...

Other European NADs

As noted in A1.5, the future status ofNADs is uncertain. The present situation, which relates to the 1995 edition of EC7, is described here. The purpose and use of National Application Documents (NADs) was introduced in A1.5 and A1.6, and the British NAD was discussed in A2.4. For the members of the EU, each State prepares its own National Application Document (NAD) for each Eurocode. These will generally be written in the national language and, together with the national translation of the...

Other checks required by EC

Overall equilibrium should be checked in accordance with 8.2(1)P. This depends on the form of the prop or anchor, and could involve slip surfaces passing behind anchorages, for example, or cutting through the fixed anchor length. Vertical equilibrium of the sheet pile should be checked in the ultimate limit state (EC7, 8.6.5). Small inequalities between the downward force from the retained soil and the upward force from the passive soil can be taken out at the base of the wall. If inclined...

Case C settlement taken as action

Vertical load, V yG 1.0 (Table 2.1) Settlement yG 1.0 (Table 2.1). Shaft resistance, R ys 1.3 (Table 7.2). When downdragforce was taken as an action, in Case CI, a factor of 1.0 was applied to it. However, when settlement is taken to be the action, its effect is transferred to the pile using the soil strength, which therefore acts in an unfavourable manner. EC7,2.4.2(11) says that a partial factor less than 1.0 must be applied in such cases, but a more precise value is not given. It could be...

CP to

Although the method is based on the designer's assessment of base and shaft resistance, usually by calculation, it is related very strongly to results of static load tests. It is assumed that calculation rules have been derived by studying the results of load tests and an allowance of 1.5 is made for the likely variability of the test. C7.6.3.4 Ultimate bearing resistancefrom pile drivingformulae Summary Pile driving formulae may be used as the basis of pile design, provided the formulae have...

Supervision of construction

The requirements of this clause are generally consistent with 'Specification for piling and embedded retaining walls' (ICE (1996)). The requirement that records be kept for at least 5 years is not included in the ICE Specification, but the CDM Regulations (Health and Safety Commission (1994)) implicitly require that as-built drawings are retained throughout the life of the structure. These will normally contain a summary of the data recorded during construction, including ground stratification.

Actions geometrical data and design situations

Besides listing relevant actions, 2.4.2 also requires the use of Cases A, B and C and the partial load factors to be applied. These are to be applied to retaining structures, with the special note in 2.4.2(17) about the application of Case B. The clauses of Section 8 refer directly to 'design values' rather than characteristic values. These design values should generally be derived from characteristic values in accordance with 2.4.2. C8.3.1.1 Weight of backfill material Unlike BS 8002, Eurocode...

Retaining Structures

This section considers the design of all types of earth retaining structures, and includes a clause on anchorages. It relies on Sections 6 and 7 for the foundations of the structures EC7,8.2 4 and on Section 9 for requirements of overall stability. The section has some similarities with BS 8002, but also some differences. Appendix 3 lists the main items required for retaining wall calculations, comparing BS 8002 and Eurocode 7. In particular, Eurocode 7 mentions unplanned overdig' 8.3.2.1 , but...

Basic set of calculations

For ULS design, the partial factors given in EC7, Table 2.1 will be used. If the sheet pile wall had only a temporary purpose, and if the consequences of failure would be less than for a typical design of permanent works, it is arguable that smaller partial factors could be used in accordance with 2.4.2 14 P see C2.4.2 14 P . CIRIA Report 104, Table 5, could be used to form a view on the proportion by which factors may be reduced for the temporary case. Figure E15.1 shows the characteristic...

Case B downdrag force taken as action

Vertical load, V yG 1.35 Table 2.1 Downdrag, D yG 1.35 Table 2.1 . Partial factors for resistances Shaft resistance, R ys 1.0 Table 7.2 . Total design vertical load Fd Vd Dd VkxyG DkxyG 300x1.35 94.2x1.35 532.2 kN. Design shaft resistance Rd Rk ys Hence 47.1 x LR 1.0 gt 532.2 kN. Design force for concrete shaft Fd 532.2 kN,

A sample analytical method for bearing resistance calculation

The calculation method for bearing capacity given in Annex B is recommended for general use. It is a development of the original work of Brinch Hansen 1970 , taking advantage of more recent work, particularly that of Smoltczyk and his co-workers in Stuttgart. This has led to a revision of the formula for N providing a less conservative value. A comparison of various formulae for Ny derived by different researchers over the past decades is presented in Appendix 1. Formulae for Nc and Nq are well...

Embankments And Slopes

This section covers two main topics site stability including slopes and embankments. It might have been better to place a section on site stability at an earlier point in the code, since reference is made to this section from Sections 6,7 and 8. In principle, embankments and slopes should be designed for Cases A, B and C, as with other items. However, Case B is rarely found to be critical, and 9.5.1 5 P states that Case A may generally be omitted. The section is therefore directed almost...

Calculation of the effect of moment loading

Moment loading could be incorporated in Method D.l by dividing the vertical load into strips that would result in the correct moment being applied about the centre of the footing. The result on moment loading would not significantly alter the settlement at the centre point of the footing. In Method D.2, equations similar to those for settlement calculation exist for moment loading Poulos and Davis 1974 as shown above for E4. From the data in E4, the design loadings for SLS conditions at the...

Approach

Checks are required for Cases B and C. This requires some interpretation of EC7 Section 7 which was written for Case C alone. The concepts embodied in Table 2.1 will be followed, applying Case B directly and replacing the factors on soil strength in Case C by factors from Table 7.2 EC7,2.4.3 12 P . EC7,7.3.2.1 allows the designer to adopt either the ground displacement or the downdrag forces on the pile as the action see C7.3.2.1 2 . The designer must show that the pile conforms to EC7 by one...

Appendices

1 Bearing capacity factor for shallow foundations 101 3 Design to BS 8002 and Eurocode 7 103 Eurocode 7, to be used in conjunction with Eurocode 1, applies to the geotechnical aspects of design of buildings and civil engineering structures for strength, stability, serviceability and durability. It provides rules for calculating design earth pressures, and, in this respect, acts as a loading code for use with other Eurocodes. It also gives some minimum standards for construction requirements. It...

Detailed comparative study

In this section, an extensive series of comparative calculations is presented. These would not be needed in a design process, but are included here to facilitate comparisons between results from EC7 and those from other documents and methods. The problem addressed is as shown in Figures E15.1, E15.2 and E15.3, with two aspects differing from the calculations in the previous section a water pressures are not equalised at the bottom of the wall, but are assumed hydrostatic on both sides, and b...

E SLS check

Table E15.2 also shows the results of a serviceability computation by FREW. For this, all partial factors are unity and there is no allowance for 'overdig'. The length of wall gives it fixity at the base, as can be seen in Figure E15.5, and the SLS bending moment is 119 kNm m, only 28 of the design ULS value. Calculations of this type, if done at all, would normally only be used to assess the maximum SLS deflection, which was calculated as 29 mm. This value should be used in assessing effects...

Ultimate limit state design

Besides checking the stability and serviceability of individual foundations, it is essential to check the stability of the site, or part of the site on which a structure is to be built. The reader is referred to Section 9 and to D2.2. The basic requirement is represented by the inequality Vd-Rd where Vd is the ultimate limit state design load normal to the foundation, and Rd is the design bearing resistance of the foundation against loads normal to the foundation. This may appear to be a...

K

All design values subscript d omitted for clarity Ac area of column cross-section total unit weight of soil above water table 72 total unit weight of soil below water table S action from superstructure U1 ,U2 forces due to water pressure F1 action effect of overburden Y, d, Y2 - Yw d2 Ywd2 Ab- Ac where F't effective action effect of overburden S W F', U, - U2 This must be matched by design resistance Rd, which in this case is an effective force. The code recommends that water pressures are...

Figure El Slip circle in drained ground

The bulk unit weight of the clay is 20kN m3. The slope is 8 m high and has an inclination of22 . Drainage provisions at the site provide a groundwater level which is hydrostatic from 1 m below the finished ground level. There is a permanent UDL of 10 kPa at the top of the slope. Three slope stability problems have been analysed using the Oasys program SLOPE. The three analyses are Calculation 1 Demonstration that the slope as designed with the design parameters satisfies the requirements of EC7...

Sample methods for settlement evaluation D Stressstrain method

The method described here is a standard approach to settlement calculation. Stresses are derived from elasticity theory such as the Boussinesq equations , and strains are then calculated for various layers in the ground according to the Young's modulus at each point. Vertical strains are integrated to find displacement. Computer programs such as VDISP in the CtojvGEO suite perform this calculation. The stress distribution used for this calculation is an approximation since it is derived taking...

E ULS calculations

In order to satisfy EC7, Cases B and C must both be satisfied. For Case B the required dimension of the 0.75 m deep footing was calculated to be 2.5 m square, while for Case C the required dimension was 3.0 m square. These dimensions were found by iteration. As Case C governed sizing of the footing in this instance, the calculations for the final iteration of this case will be presented below. Design vertical action at footing base Vertical action Vd yG Gvk WJ yQ Qvk Wvk Weight of pad 1.0 x...

More refined calculation

EC7 requires that the design must demonstrate that equilibrium can be achieved using the design actions and the design strengths, with compatibility of deformations 8.6.1 4 P and 2.1 9 . It does not specify, however, a particular distribution of earth pressures to be used for embedded walls. For the ULS calculations, there is no limit to the magnitude of displacements allowed, unless they would cause a ULS in an adjacent structure. For propped walls, the computed bending moments and prop forces...

Uls Check On A Simple Potentially Buoyant Structure

In this example, the values of partialfactors are taken directlyfrom EC7 Table 2.1. However, it is argued in B5.7 that the value assigned to yG when it reduces beneficial permanent loads is uncomfortably small. The partially buried structure shown in Figure E18.1 is circular, 10 m in diameter D, externally and extends z 6 m below ground level. The worst credible groundwater pressures are represented by a water table at the ground surface with hydrostatic pressures beneath y 10 kN m3 . The...

The German NAD

DIN 1996 have published the proceedings of a seminar in which applications of Eurocode 7 were demonstrated by extensive worked examples. This reflects the state of German thinking about EC7 in 1996. Features of this NAD are summarised in Table D3.2. As can be seen, there is extensive reference to DIN documents. Note the designation 'V' refers to pre-standards, for experimental application. These documents have been included as Appendices in the NAD and embrace the concept of partial safety...

Geotechnical Data

This section lays down basic principles of geotechnical investigation and derivation of parameter values. It also requires that a geotechnical investigation report must be produced. The section deals with basic principles, not with details. It will be supplemented by Parts 2 and 3 of Eurocode 7 which contain main requirements of site investigation and test procedures, with discussion of derivation of parameter values from individual tests. Further information on Parts 2 and 3 is presented in...

Introduction

This commentary is intended to help the reader to understand Eurocode 7, in the form published in 1995, by providing a reviews of new concepts b clarification of the text C comparisons against existing British practice d worked examples. It does not attempt to replace text books on geotechnical engineering, but is limited to the task of explaining the intentions of Eurocode 7, especially where these differ from previous design approaches. The commentary does not debate alternatives to Eurocode...

Uls

A3.3 Requirements, recommendations and some administrative definitions The Eurocodes use the verbs 'shall' and 'should' in a carefully defined manner. As noted in C1.3, 'shall' is used in Principles and 'should' in Application Rules. In this commentary, the verb 'must' is used to mean that, in the opinion of the authors of the commentary, EC7-1 is imposing a mandatory requirement. The word 'recommended' is used to indicate the recommendations of the authors of this commentary. In Cl.5.2,...

E Design Of A Ground Anchor E Description of problem

In E15 it was assumed that the sheet pile wall was supported by a prop. Here, it will be assumed that ground anchors are to be provided, which will give the same horizontal force as that obtained in Table E15.2. The critical prop force for ULS design was 238 kN m from Case C. It will be assumed that the anchors are to be inclined at 30 to the horizontal and are to be permanent. At least three anchors will be subject to assessment tests. The design approach provided below is considered to be...

1537 1996 Anchors

Value of anchor force at indicated stage in the process a SLS force may exceed ULS force in some cases. Case A should be treated as Cases B and C, when relevant b For permanent anchors EC7,8.8.5 6 . Use 1.25 for temporary anchors c EC7 Table 8.1, assuming more than 2 assessment tests d Designer's or constructor's judgement, in order to achieve required mean result e See BS 8081,11.4.3. Use 1.25 for temporary anchors g Including bearing plates, walings and connections. prEN 1537 1996 contains...

Bearing capacity factor Ny for shallow foundations

The stability of shallow foundations, including both mudmats and bases of gravity structures, is conventionally checked using bearing capacity factors Nq, Nc and Nr The values of Nq and Nc are established by theory and there is no dispute about these. However, Ny is established empirically and its value has been'the subject of much debate over many years. It is particularly critical to the design of large shallow foundations subject to a component of horizontal loading. Brinch Hansen 1970...

Bearing capacity calculations

Using the formulae in Annex B.2 for undrained conditions, the length of side of the footing for Case B was 3.75 m while for Case C is was 4.0 m. Hence, as for E2, Case C is critical and B L 4.0 m. This may be checked as follows. For Case C, the design vertical action at footing base Vertical action Vd yG Gvk Wvii yQ Qvk Wvk weight of pad 1.0 x 1000 24.5 x 4.0 x 4.0 x 0.75 1.3 x 2000 1000 294 2600 3894 kN. The design horizontal and moment actions are as in E2,390 kN and 1073 kNm, respectively....

Other overseas usage of Eurocode

In 1995, the South African Institution of Civil Engineers decided to adopt EC7 as a standard for limit state design in geoteChnics it would be used in parallel with existing design methods for a trial period of three years. Thus far, there has been little use made of EC7. One reason for this is that the South African Bureau of Standards adopted for its structural codes a partial load factor for dead weight of 1.2 compared with the EC7 boxed value of 1.35. Another important reason is that many...

Serviceability limit states

Serviceability considerations apply to the displacement of the structure and surrounding ground, and to the performance of the concrete, especially with regard to cracking. EC7,8.7.2 notes that it is often possible to avoid detailed analysis of displacement by noting comparable examples. It would not normally be necessary to calculate the displacement of a wall of this type on a sand foundation. If it were, the methods of calculating settlements of footings, noted in E5, could be adopted. For...

References

Standard specifications for highway bridges. American Association of State Highway and Transportation Officials. AASHTO 1993 . Interim specifications - Bridges. American Association of State Highway and Transportation Officials. API 1993 . Recommended practice for planning, designing and constructing fixed offshore platforms - Working stress design. American Petroleum Institute Recommended Practice 2A-WSD RP 2A-WSD . ASTM 1985 . Axial pile loading test - Parti Static loading....

A sample semiempirical method for bearing resistance evaluation

Annex C presents the basic principles of evaluation of bearing resistance from Menard pressuremeter tests. Insufficient detail is given to make calculations possible, though more will be included in EC7 Part 3 ENV 1997-3 , when it is published. For more information, reference should be made to Menard 1975 , Baguelin et al 1978 and the brief discussion of Mair and Wood 1987, section 6.7 . The semi-empirical use of the pressuremeter, popular in France, is based on results from Menard...

Pile Negative Friction Eurocode

The designer is allowed to chose between two approaches, treating either forces or displacements as the basic action. The more economic approach may be chosen in each circumstance. An example of this is presented below under C7.3.2.2. C7.3.2.2 Downdrag negative skin friction Downdrag will usually be analysed by calculating the maximum force which could be generated by negative skin friction, following Paragraph 2 , and treating this as an action Paragraph 1 P . This implies that the force will...