Design situations and limit states

Ultimate Limit States Picture

9 of Eurocode 7 Part 1 includes a series of illustrations showing limit modes for gravity walls, including overall stability, foundation failure, and structural failure. Figure 11.2 gives examples of ultimate limit states that can affect mass gravity walls. From left to right, these include toppling, sliding, and bearing failure. Figure 11.2. Examples of ultimate limit states for mass gravity walls Figure 11.2. Examples of ultimate limit states for mass gravity walls fi.e. weaker strata are...

Effects of actions

In structural engineering, effects of actions are a function of the actions applied to a structure and that structure's dimensions, but not of material strength, i.e. where the notation E denotes that the design effect Ed depends solely on design actions Fdi and design dimensions adj. This holds true for linear elastic analysis of structures, but not for plastic analysis. An example may help to illustrate the ideas behind this equation. Figure 2.13 shows a simply-supported concrete beam subject...

Info

'Effects of actions' (or 'action effects') is a general term denoting internal forces, moments, stresses, and strains in structural members plus the deflection and rotation of the whole structure. en 1990 1.5.3.2 For most structural designs, verification of limit state STR involves action effects that are independent of the strength of the structural materials (see Chapter 2). However, in many geotechnical designs, verification of the STR and GEO limit states involves effects of actions that...

International Standardization Organization ISO

The International Organization for Standardization (known as ISO, after the Greek word 'isos' meaning 'equal') was founded in 1947 to 'facilitate the international coordination and unification of industrial standards'.13 ISO is a network of national standards bodies from 158 countries (comprising 103 member bodies, 46 correspondent members, and 9 subscriber members). Figure 1.5 illustrates the current membership of ISO. Based in Geneva, ISO has almost 200 technical committees (TCs) which are...

Summary of key points

'structural design is an iterative process of applying engineering mechanics and past experience to create a functional, economic, and, most importantly, safe structure for the public to enjoy'10 The Eurocodes - and in particular, EN 1990 - provide a comprehensive and cohesive framework for ensuring the safety of structures. The engineering concepts that are embodied in them have been used in engineering practice for decades and will be familiar to most structural engineers. The impact of the...

Verification of strength

'It is not possible to fight beyond your strength, even if you strive' - Homer (800-700 BC)1 Verification of strength to Eurocode 7 involves checking that design effects of actions do not exceed their corresponding design resistances. Verification of strength is expressed in Eurocode 7 by the inequality Ed < Rd EN 1990 exp (6.8) & EN 1997-1 exp (2.5) in which Ed the design effects of actions and Rd the corresponding design resistance. This requirement applies to ultimate limit state GEO,...

Emirates Stadium Pile Tests

13.14.3 Static load tests for the Emirates Stadium in London Example 13.3 looks at the design of bored piles for the Emirates Stadium in London, the new home of Arsenal Football Club.18 Seven preliminary pile tests were carried out on piles of the same diameter, but with slightly different depths of penetration. Six of the piles (P1-3 and P5-7) were of similar length, between 23.5m and 26.3m, and one pile (P4) was significantly shorter, at 16.9m. All the piles were of bored construction. Ground...

Stability of a finite slope based on method of slices

Bromhead5 defines the factor of safety used in limit equilibrium methods as the ratio of the mobilized shear strength to the actual shear strength available. This is akin to applying a partial factor to material strength and hence those Design Approaches that apply partial factors to material properties are highly suited to the solution of slope stability problems. Methods for the limit equilibrium analysis of slopes range from simple translational sliding along a flat plane (as discussed in...

Earth pressure coefficients

EN 1997-1 Annex C provides a numerical procedure for determining active and passive earth pressure coefficients for use in retaining wall design, which is discussed in Chapter 12. The charts that follow show the variation in KaY and KpY (denoted Ka and Kp on these charts) with angle of shearing resistance 9, for different values of interface friction 5 (0 , 5 , 10 , 15 , 20 , 25 , and 30 ), for vertical walls (0 0 ). Each figure gives curves for different slope gradients tan p (flat, 1 10, 1 5,...

Design for serviceability

Design values of earth pressures for the verification of serviceability limit states must be derived using characteristic soil parameters, taking account of the initial stress, stiffness, and strength of the ground the stiffness of structural elements and the allowable deformation of the structure. These earth pressures may not reach limiting (i.e. fully active or passive) values. EN 1997-1 9.8.1(2)P, (4), and (5) Limiting values for the allowable wall and ground displacements must take into...

Verification by the partial factor method Partial factors on actions

Weak And Partial Structural Models

Representative actions (Frep) are converted into design values (Fd) by multiplying by an appropriate partial factor (yf) where yf takes account of uncertainties in the magnitude of the action, model uncertainties, and dimensional variations. For unfavourable actions, yf 1, whereas for favourable actions yf 1 and the previous equation is qualified as follows (see Figure 2.18) Values of yf and YF,fav for persistent and transient design situations are given in EN 1990 and vary between 0.9 and 1.5,...

Limiting equilibrium methods

Point Fixity

Limiting equilibrium methods are commonly used to assess the required penetration of embedded retaining walls, associated shear forces and bending moments in their cross-sections, and the forces in any props or anchors used to support them. Limiting equilibrium methods assume that the full strength of the ground is mobilized uniformly around the wall, so that the wall is at the point of collapse or 'limiting equilibrium' . Cantilever walls and walls propped near their top are statically...

Slope Stability Da3 Eurocode

TChoice made in Eurocode 7 Designers' Guide3 It is unclear whether this should be Yes or No tChoice made in Eurocode 7 Designers' Guide3 It is unclear whether this should be Yes or No 6.3.4 Choice of design approach by different European countries Eurocode 7 Part 1 allows each country to specify in its National Annex which design approach must be used within its jurisdiction. The choices made by the countries within CEN4 are summarized in Figure 6.18 for slopes and Figure 6.19 for other...

The Structural Eurocode programme

Standards Architecture Class

The Structural Eurocodes are a suite of ten standards for the design of buildings and civil engineering works, as illustrated in Figure 1.1 and Plate 2 in the book's colour section . These standards are divided into fifty-eight parts and are accompanied by National Annexes issued by the various European countries that have introduced the Eurocodes into their design practice. Figure 1.1. Standards within the Structural Eurocodes programme. See Plate 2 for colour version. Figure 1.1. Standards...

Comparison with existing practice

Standard Penetration Test

The following sub-sections compare the Ground Investigation and Geotechnical Design Reports with traditional reports on these subjects. Current UK practice is specified in Section 7 of BS 5930,5 which defines the series of reports illustrated in Figure 16.7. Field reports cover all the information that needs to be obtained while working on site, e.g. the recording of in situ tests such as the standard penetration test, cone penetration test, pressuremeter, etc. and production of drillers' logs....

Active Earth Pressure

What Earth Pressure

Curve 1 on each graph shows the results obtained for a serviceability limit state calculation, with all partial factors set to 1.0 - i.e. with all parameters at their characteristic values. The depths of embedment needed to ensure stability for this situation are 9.63m and 7.00m respectively for the two walls. Curve 2 shows the results obtained when passive earth pressures are treated as an unfavourable action, as allowed by the Single-Source Principle discussed in Chapter 3. A single partial...

Reaction to the Eurocodes

The Eurocode Scream Jack Offord

Unfortunately, many engineers' initial reaction to Eurocode 7 is a cross between The Eurocode Scream see Figure 17.1 and the natural instinct of an ostrich, which , when frightened, buries its head in the sand. However, when the shock of the new is overcome, views change as the benefits of the Eurocodes become apparent. The views of many engineers are based on limited knowledge of the Eurocodes and even less experience of using them in practice. Figure 17.2 summarizes some of the opinions that...

Notes and references

Driscoll, R.M.C., Powell, J.J.M., and Scott, P.D. 2008 EC7 - implications for UK practice, CIRIA RP701. 2. BS EN 1997-2 2007, Eurocode 7 - Geotechnical design, Part 2 - Ground investigation and testing, British Standards Institution, London, 999pp. 3. BS EN ISO 17892, Geotechnical investigation and testing Laboratory testing of soil, British Standards Institution. Part 1 Determination of water content. Part 2 Determination of density of fine grained soil. Part 3 Determination of density of...

Soilstructure interaction analysis

Eurocode 7 notes that, for anchored or strutted flexible walls, the magnitude and distribution of earth pressures, internal structural forces, and bending moments depend to a great extent on the stiffness of the structure, the stiffness and strength of the ground, and the state of stress in the ground. If structural stiffness is significant, soil-structure interaction analysis should be performed to determine the distribution of actions. The stress-strain relationships used in such analyses...

QEk A A

Footings With Biaxial Moments

Where Vrep is a representative vertical action VGk, VQk, and WGk are as defined above A' is the footing's effective area defined in Section 10.4.2 and is the combination factor applicable to the ith variable action see Chapter 2 . If we assume that only one variable action is applied to the footing, this equation simplifies to since 1.0 for the leading variable action i 1 . The design bearing pressure qEd beneath the footing is then where yg and yq are partial factors on permanent and variable...

Eurocode 7 Worked Examples

Eccentrically Loaded Footings

The worked examples in this chapter consider the design of a pad footing on dry sand Example 10.1 the same footing but eccentrically loaded Example 10.2 a strip footing on clay Example 10.3 and, for the same footing, verification of the serviceability limit state Example 10.4 . Specific parts of the calculations are marked O, , , etc., where the numbers refer to the notes that accompany each example. Example 10.1 considers the design of a simple rectangular spread footing on dry sand, as shown...

Identification and classification of soil

Columns Eurocodes

Identification and classification of soil is covered by International Standard EN ISO 14688, which is divided into three parts covering description Part 1 , classification Part 2 , and data transfer Part 3 .6 EN ISO 14688 is referenced extensively in EN 1997-2. Figure 4.6 illustrates the logic for identifying soils according to EN ISO 14688-1. The main soil types are divided into made ground, organic soil, volcanic soil, and very coarse, coarse, and fine soils. Very coarse soils are sub-divided...

UkM rw h d yw d j

Magnel Diagram

D,dst Yg,dstYw y dj Yg,dstYw 1 d and, since this is a permanent destabilizing action, its design value is The characteristic vertical total stress acting on the same plane is and, since this is a permanent stabilizing action, its design value is Substituting these expressions into ud dst lt od stb and simplifying produces -1 hnL _ I j 0.33 - hnL 1.5 I 3 I 3.0 1. For this situation, we conclude that the partial factors specified for limit state HYD are equivalent to a global factor of 3.0 on the...

Utilization Factor Structural Design

Sheet Pile Basal Heave

The design is unacceptable if the degree of utilization is gt 100 Traditional factor of safety against piping The soil's critical hydraulic gradient is i crit - 1 Factor of safety on hydraulic gradient is F - 3.38 w 0 The degree of utilization using expression 2.9 a is close to 100 , whereas using 2.9 b it is less than 50 . Eurocode 7 does not explicitly state where the partial factors should be applied, which leads to the discrepancy between these expressions, which was not anticipated by the...

Anchorage tests

Proof Load Yield

Eurocode 7 discusses three types of anchorage test investigation, suitability, and acceptance. An investigation test is a 'load test to establish the ultimate resistance of an anchor at the grout ground interface and to determine the characteristics of the anchorage in the working load range'. This definition is identical to the one given in EN 1537. EN 1997-1 8.1.2.5 Investigation tests are performed, before working anchorages are installed, to establish the anchorage's ultimate pull-out...

Material properties and resistance Resistance

Characteristic Material Strengths

The resistance of a structural member is defined as the capacity of a member or component, or cross-section of a member or component of a structure, to withstand actions without mechanical failure In structural engineering, resistance is a function of the structure's material strengths and its dimensions, but not of the magnitude of any actions applied to the structure, i.e. where the notation R denotes that the design resistance Rd depends solely on design material strengths Xdi and design...

Limit state EQU

Limit state EQU, dealing with static equilibrium, is defined as Loss of static equilibrium of the structure considered as a rigid body, where minor variations in the actions or their distribution are significant, and the strengths of materials are generally not governing. Limit state EQU does not occur when the destabilizing design effects of actions Ed,dst are less than or equal to the stabilizing design effects Ed,stb Ed, dst Ed,stb EN 1990 x 67 Ed, dst Ed,stb EN 1990 x 67 Figure 2.6....

Combinations of actions

Favourable Permanent Action

Representative actions Frep are obtained by assembling suitable combinations of characteristic values Fk , following the rules given in ENs 1990 and 1991. The representative value of a single generic action is given by where is a combination factor, less than or equal to 1.0. The combination factor is omitted for permanent actions, i.e. a representative permanent action G,j is equal to its characteristic value Gkj . The total design permanent action Gd is then obtained from the sum of the...

Deriving geotechnical parameters Overview

Eurocode Clay Shear Strength

The derived value of a geotechnical parameter is defined in Eurocode 7 as the value obtained by theory, correlation or empiricism from test results EN 1997-1 1.5.2.5 amp EN 1997-2 1.6 3 As the flow-chart of Figure 5.2 illustrates, test results may be converted into derived values X by use of correlations such as that between cone penetration resistance and angle of shearing resistance in sand , theoretical considerations such as conversion of triaxial compression into plane strain strengths for...

Worked examples

Ground Investigation

The worked examples in this chapter use the guidance given in Eurocode 7 Part 2 on the scope of ground investigations to illustrate where there are significant changes from current UK practice. Example 4.1 considers the specification of field work for a hotel site in North West England Example 4.2 looks at how changes in soil description will affect the borehole logs and Example 4.3 discusses the specification of laboratory tests. Specific parts of the calculations are marked O, , , etc., where...

Standards for geotechnical investigation and testing Eurocode Part

Geotechnical Investigation

Eurocode 7 - Geotechnical design, Part 2 - ground investigation and testing2 is divided into six sections and twenty-four annexes, as illustrated in Figure 4.1 and Plate 6 in the book's colour section . 2 Planning of ground 1 General Investigations 3 Soil and rock Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version. 2 Planning of ground 1 General Investigations 3 Soil and rock Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version. EN 1997-2 provides...

Supervision monitoring and maintenance

Eurocode 7 has specific requirements to ensure the quality and safety of a structure the construction processes and workmanship shall be supervised the performance of the structure shall be monitored during and after construction and the structure shall be adequately maintained. EN 1997-1 qualifies this requirement by saying these tasks should be undertaken 'as appropriate'. Thus, if construction does not need supervising, or the structure does not need monitoring or maintaining, then the...