cen/tc 250/sc 2/wg 2 n 0154

CEN/TC 250 Date: 2004-02

CEN/TS XXXXX-2:2004/prA09:2004.09/P2

CEN/TC 250

Secretariat: DIN

Design of Fastenings for Use in Concrete — Draft 9 — Part 2: Headed fasteners

Einführendes Element — Haupt-Element — Teil 2: Teil-Titel

Élément introductif — Élément central — Partie 2 : Titre de la partie

ICS:

Descriptors:

Document type: Technical Specification Document subtype: Amendment Document stage: Working Document Document language: E F:\CEN\CEN250\Draft Code\CEN TS A09_(E)_2.doc STD Version 2.1c

DIN

CEN/TC 250/SC 2/WG 2 N 0154

CEN/TS XXXXX-2:2004/prA09:2004.09/P2 (E)

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Contents Page

Foreword..............................................................................................................................................................3 1 Scope ......................................................................................................................................................3 1.1 General....................................................................................................................................................3 1.2 Fastener dimensions and materials.....................................................................................................4 1.3 Fastener loading ....................................................................................................................................4 2 Normative references ............................................................................................................................5 3 Definitions and symbols .......................................................................................................................6 3.1 Definitions ..............................................................................................................................................6 3.2 Notations ................................................................................................................................................7 3.2.1 Indices.....................................................................................................................................................7 3.2.2 Actions and Resistances ......................................................................................................................8 3.2.3 Concrete and steel.................................................................................................................................9 3.2.4 Units ..................................................................................................................................................... 13 4 Basis of design ................................................................................................................................... 13 5 Determination of action effects ......................................................................................................... 13 5.1 General................................................................................................................................................. 13 5.2 Tension loads...................................................................................................................................... 13 5.3 Shear loads.......................................................................................................................................... 16 5.3.1 Distribution of shear loads ................................................................................................................ 16 5.3.2 Eccentricity of shear loads ................................................................................................................ 21 5.3.3 Shear loads without lever arm........................................................................................................... 21 5.3.4 Shear loads with lever arm ................................................................................................................ 22 5.4 Tension forces of a special supplementary reinforcement............................................................ 23 5.4.1 Tension loads...................................................................................................................................... 23 5.4.2 Shear loads.......................................................................................................................................... 23 6 Verification of ultimate limit state by elastic analysis .................................................................... 23 6.1 General................................................................................................................................................. 23 6.2 Tension loads...................................................................................................................................... 24 6.2.1 Required proofs .................................................................................................................................. 24 6.2.2 Steel failure.......................................................................................................................................... 24 6.2.3 Pull-out failure..................................................................................................................................... 24 6.2.4 Concrete cone failure ......................................................................................................................... 24 6.2.5 Splitting failure due to loading.......................................................................................................... 28 6.2.6 Blow-out failure................................................................................................................................... 29 6.2.7 Detailing of supplementary reinforcement ...................................................................................... 31 6.3 Shear load............................................................................................................................................ 33 6.3.1 Required proofs .................................................................................................................................. 33 6.3.2 Steel failure.......................................................................................................................................... 33 6.3.3 Concrete pry-out failure ..................................................................................................................... 34 6.3.4 Concrete edge failure ......................................................................................................................... 34 6.3.5 Detailing of supplementary reinforcement ...................................................................................... 38 6.4 Combined tension and shear load.................................................................................................... 41 6.4.1 Fastenings without supplementary reinforcement ......................................................................... 41 7 Fatigue ................................................................................................................................................. 42 7.1 General................................................................................................................................................. 42 8 Seismic ................................................................................................................................................ 42 8.1 General................................................................................................................................................. 42


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Foreword

This document CEN/TS XXXXX-2:2004/prA09:2004.09/P2 has been prepared by Technical Committee CEN/TC 250 “/SC 2/WG 2”, the secretariat of which is held by DIN.

This document is a working document.

TS XXXX-Y-Z –Part 2 –Headed fasteners describes the principles and requirements for safety, serviceability and durability of headed fasteners for use in concrete, together with specific provisions for structures serving as base material of the fasteners. It is based on the limit state concept used in conjunction with a partial factor method.

Numerical values for partial safety factors and other reliability parameters are recommended as basic values that provide an acceptable level of reliability. They have been selected assuming that an appropriate level of workmanship and of quality management applies. Partial factors, where national choices may have to be made are given with notes.

TS XXXX-Y-Z 'Design of fasteners for use in concrete' is subdivided into the following parts:

Part 1: General

Part 2: Headed fasteners

Part 3: Anchor channels

Part 4: Post-installed fasteners –mechanical systems

Part 5: Post-installed fasteners – chemical systems

1 Scope

1.1 General

1.1.1 This Part 2 of the Technical Specification 'Design of fastenings for use in concrete' provides design requirements to transmit actions from headed fasteners to the concrete.

1.1.2 This Technical Specification is intended for application to the design of fastenings for use in structural and non-structural applications.

1.1.3 This Technical Specification applies only to headed fasteners covered by an European Technical Approval (ETA) and relies on characteristic resistances and distances which are stated in the ETA.

This Technical Specification may also be used for headed fasteners covered by a CEN-Product Standard if the data required by this Technical Specification are provided and reference to this Technical Specification is given in the CEN-Product Standard.

1.1.4 The Technical Specification applies to single fasteners and groups of fasteners. In a fastening group the loads are applied to the individual fasteners of the group by means of a common fixture.

CEN/TS XXXXX-2:2004/prA09:2004.09/P2 (E) rA09:2004.09/P2 (E)

Two types of applications have to be distinguished: Two types of applications have to be distinguished:

a) In case of a hole clearance between fastener and fixture the fastener arrangements shown in Figures 1.1 and 1.2 are covered by the design methods presented in this Technical Specification.

a) In case of a hole clearance between fastener and fixture the fastener arrangements shown in Figures 1.1 and 1.2 are covered by the design methods presented in this Technical Specification.

b) If the bolts are welded to the fixture or if there is no hole clearance or if the gap between fastener and fixtures is filled up with mortar of sufficient compressive strength or other suitable means, independent of the edge distance the arrangement of fasteners covered by this Technical Specification covers fastenings consisting of up to 9 headed fasteners with a maximum of 3 fasteners in a row.

b) If the bolts are welded to the fixture or if there is no hole clearance or if the gap between fastener and fixtures is filled up with mortar of sufficient compressive strength or other suitable means, independent of the edge distance the arrangement of fasteners covered by this Technical Specification covers fastenings consisting of up to 9 headed fasteners with a maximum of 3 fasteners in a row.

In this Technical Specification it is presumed that in a fastening group only post-installed fasteners of identical size and characteristics are used. In this Technical Specification it is presumed that in a fastening group only post-installed fasteners of identical size and characteristics are used.

Figure 1.1 — Fastenings with hole clearance situated far from edges (c >Figure 1.1 — Fastenings with hole clearance situated far from edges (c > 10 h ) covered by the design methods

ef

Figure 1.2 — Fastenings with hole clearance situated near to an edge (c < 10 hef) covered by the design methods

1.2 Fastener dimensions and materials

1.2.1 This Technical Specification applies to fasteners with a minimum thread size of 6 mm (M6) or a corresponding cross section. In general, the minimum embedment depth should be hef = 40 mm.

1.2.2 This Technical Specification covers metal fasteners made of either carbon steel, stainless steel or malleable cast iron. The maximum steel tensile strength considered is fuk = 1000 MPa.

1.3 Fastener loading

This Standard applies to fastenings with headed fasteners subjected to static, fatigue and seismic loading.

The fixture may be subjected to normal-, shear- or combined normal and shear loads as well as bending and torsion moments.

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2 Normative references

This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies.

The following references to Eurocodes are references to European Standards and European Prestandards. These are the only European documents available at the time of publication of this Standard. National documents take precedence until Eurocodes are published as European Standards.

EN 1990: 2002, Basis of design for structural Eurocodes

ENV 1991-1-2: Eurocode 1 : Actions on structures - Part 1-2 : General structures - Actions on structures exposed to fire.

EN 1992-1-1: 2003, Eurocode 2 : Design of concrete structures - Part 1-1 : General common rules and rules for building and civil engineering structures.

ENV 1992-1-6:1994, Eurocode 2 : Design of concrete structures - Part 1-6 : General rules - Plain concrete structures.

EN 1993-1-1: 2003, Eurocode 3 : Design of steel structures, Part 1-1: General rules.

EN 1998: 200X, Eurocode 8 : Design of structures for earthquake resistance

EN 10002-1: Metallic materials - Tensile testing - Part 1: Method of test at ambient temperature.

EN 10080-11): Steel for the reinforcement of concrete - Weldable reinforcing steel – Part 1: General requirements.

EN 10088-2: Stainless steels-Part 2: Technical delivery conditions for sheet/plate and strip of corrosion resisting sheets for general purposes.

EN 10088-3: Stainless steels-Part 3: Technical delivery conditions for semi-finished products, bars, rods, wire, sections and bright products of corrosion resisting sheets for general and construction purposes.

EN 13501-21): Fire classification of construction products and building elements - Part 2 : Classification using data from fire resistance tests (excluding ventilation services).

EN ISO 13918: Welding - Studs and ceramic ferrules for arc stud welding

ISO 898-01: Mechanical properties of fasteners made of carbon steel and alloy steel.- Part 1: Bolts, screws and studs

ISO 898-02: Mechanical properties of fasteners made of carbon steel and alloy steel.- Part 2: Nuts with specified proof load values, coarse thread

ISO 1803: 1997, Building construction – Tolerances - Expression of dimensional accuracy - Principles and terminology.

ISO 3506: 1998, Corrosion-resistant stainless steel fastenings; Specifications.

ISO 5922: Malleable cast iron (Revision of ISO 5922: 1981).


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3 Definitions and symbols

3.1 Definitions

3.1.1 Anchor loading: Axial - Load applied perpendicular to the surface of the base material and parallel to the fastener longitudinal axis.

3.1.2 Anchor loading: Bending - Bending effect induced by a shear load applied perpendicular to the longitudinal axis of the anchor and with an eccentricity with respect to the centroid of resistance.

3.1.3 Anchor loading: Combined - Axial and shear loading applied simultaneously (oblique loading).

3.1.4 Anchor loading: Shear – Shear induced by a load applied perpendicular to the longitudinal axis of the fastener. For anchor channels shear may be applied transversely or longitudinally with respect to the longitudinal axis of the channel.

3.1.5 Anchor spacing - Distance between the centre lines of the fasteners.

3.1.6 Attachment – see 'fixture'

3.1.7 Base material - Material in which fastening is installed, such as concrete

3.1.8 Blow-out failure – Failure mode in which the spalling of the concrete on the side face occurs around the embedded head with no major breakout at the top concrete surface. This is usually associated with anchors with small side cover and deep embedment.

3.1.9 Brittle steel element – An element with a tensile test elongation of rupture of less than 14 percent over 5 d, or reduction in area of less than 30 percent, or both.

3.1.10 Cast-in fastening – A headed bolt, headed stud, or hooked bolt installed before placing concrete.

3.1.11 Characteristic spacing – Spacing for ensuring the characteristic resistance of a single fastener.

3.1.12 Characteristic resistance – The 5 % fractile of the resistance (value with a 95 % probability of being exceeded, with a confidence level of 90 %).

3.1.13 Concrete breakout failure – Failure corresponding to a wedge of concrete surrounding the fastener or group of fasteners separating from the base.

3.1.14 Concrete member - The concrete member in which the fastener is installed and which resists forces from the fastener.

3.1.15 Concrete pryout failure – Failure which occurs under shear loading by the formation of a concrete spall behind a short, stiff fastening.

3.1.16 Displacement - Movement of fastener relative to the concrete member, to which the load is transmitted. In tension tests, displacement is measured parallel to the fastener axis; in shear tests, displacement is measured perpendicular to the fastener axis.

3.1.17 Ductile steel element – An element with a tensile test elongation of at least 14 percent over 5d and reduction in area of at least 30 percent.

3.1.18 Edge distance – The distance from the edge of the concrete surface to the centre of the nearest fastener.

3.1.19 Effective embedment depth – The depth through which the fastener transfers force to the surrounding concrete (see Figure 3.2). The effective embedment depth will normally be the depth of


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the concrete failure surface in tension applications. For cast-in headed anchor bolts and headed studs, the effective embedment depth is measured from the bearing contact surface of the head.

3.1.20 Fastening – Assembly of fixture and fasteners used to transmit loads to concrete.

3.1.21 Fixture – Structural assembly, external to the surface of the concrete, that transmits loads to the fastener. In this Standard 'attachment ' and 'fixture' are used synonymously.

3.1.22 Headed anchor – A steel fastener installed before placing concrete. It may be rigidly connected to a fixture by welding before casting (headed stud)

3.1.23 Installation safety factor– Partial safety factor to cover the sensitivity to performance of a fastener due to installation inaccuracies.

3.1.24 Mechanical interlock – Load transfer to a concrete member via interlocking surfaces.

3.1.25 Minimum edge distance – Minimum allowable edge distance of the fastener, at which concrete member will not be damaged when fastener is set.

3.1.26 Minimum spacing - Minimum fastener spacing, measured centreline to centreline, at which concrete member will not be damaged when multiple fasteners are set.

3.1.27 Multiple anchor use- the definition of multiple anchor use is given by the Member States.

3.1.28 Project specification – Instructions from the designer to the contractor

3.1.29 Projected area – The area on the free surface of the concrete member that is used to represent the larger base of the assumed rectilinear failure surface.

3.1.30 Pullout failure — A failure mode in which the fastener pulls out of the concrete without a steel failure and without a concrete cone failure at the installed embedment depth

3.1.31 Splitting failure – A concrete failure mode in which the concrete fractures along a plane passing through the axis of the fastener or fasteners.

3.1.32 Steel failure of fastener – Failure mode characterized by fracture of the steel fastener parts.

3.1.33 Supplementary reinforcement – Reinforcement tieing a potential concrete breakout body to the concrete member.

3.2 Notations

3.2.1 Indices

E Earthquake

M material

N normal force

R resistance

S action effects

V shear force

b bond


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c concrete

cb blow-out

cp concrete pryout

d design value

el elastic

fat fatigue

fix fixture

k characteristic value

min minimum

max maximum

nom nominal

p pull out

pl plastic

re reinforcement

s steel

sp splitting

u ultimate

y yield

0 basic value

3.2.2 Actions and Resistances

F force in general

N normal force (positive = tension force, negative = compression force)

V shear force

M moment

Ma bending moment on fastening

M1 bending moment on fixture around axis in direction 1

M2 bending moment on fixture around axis in direction 2

MT torsional moment on fixture


FSk (NSk; VSk; MSk; MSk,T) characteristic value of actions acting on a single fastening or the fixture of an fastening group respectively (normal load, shear load, bending moment, torsion moment)

FSd (NSd; VSd; MSd; MSd,T) design value of actions acting on a single fastening or the fixture of an fastening group respectively (normal load, shear load, bending moment, torsion moment)

hSd

hSd VN ; design value of tensile load (shear load) acting on the most stressed fastening

of an fastening group calculated according to Section 6.2.2

gSd

gSd VN ; design value of the sum of the tensile (shear) loads acting on the tensioned

(sheared) fastenings of a group calculated according to Section 6.2.2

);( SkSkRk VNF characteristic value of resistance of a single fastening or an fastening group respectively (normal force, shear force)

);( SdSdRd VNF design value of resistance of a single fastening or an fastening group respectively (normal force, shear force)

3.2.3 Concrete and steel

fck characteristic compressive strength of concrete (strength class) measured on cylinders 150 x 300 mm

fck,cube characteristic compressive strength of concrete (strength class) measured on cubes with a side length 150 mm

fyk characteristic steel yield strength or steel proof strength respectively (nominal value)

fuk characteristic steel ultimate tensile strength (nominal value)

As stressed cross section of steel

Wel elastic section modulus calculated from the stressed cross section of steel

3.2.3.1 Fasteners and fastenings

Notation and symbols frequently used in this Standard are given below and are illustrated in Figures 3.1, 3.2 and 5.11. Further particular notation and symbols are given in the text.

a1 (a2) spacing between outer fasteners in adjoining fastenings in direction 1 (direction 2) (see Figure 3.1)

a3 distance between concrete surface and point of assumed restraint of a fastener loaded by a shear force with lever arm (see Figure 5.11)

b width of concrete member

bfix width of fixture

c edge distance from the axis of a fastener (see Figure 3.1) or the axis of a channel bar

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c1 edge distance in direction 1. In the case of fasteners close to an edge loaded in shear, c1 is the edge distance in direction of the shear load (see Figure 3.1b)

c2 edge distance in direction 2. Direction 2 is perpendicular to direction 1

ccr edge distance for ensuring the transmission of the characteristic resistance of a single fastener

ccr,b edge distance for ensuring the transmission of the characteristic tension resistance of a single fastening without spacing, edge and member thickness effects in case of concrete blow-out failure

ccr,N edge distance for ensuring the transmission of the characteristic tension resistance of a single fastening without spacing and edge effects in case of concrete cone failure

ccr,sp edge distance for ensuring the transmission of the characteristic tension resistance for concrete cone failure of a single fastening without spacing and edge effects in case of splitting failure

ccr,V edge distance perpendicular to the direction of the shear load for ensuring the transmission of the characteristic shear resistance of a single fastener without spacing, corner and member thickness effects in case of concrete failure

cmin minimum allowable edge distance to avoid splitting of the concrete during installation and loading of the fastener and to achieve sound concreting in case of cast-in fasteners

d diameter of fastener bolt or thread diameter

dcut cutting diameter of drill bit

df diameter of clearance hole in the fixture

dh diameter of anchor head (headed anchor)

dnom outside diameter of a fastener

ds diameter of reinforcing bar

d0 nominal diameter of drilled hole

d1 diameter of undercutting hole

d2 diameter of expanded undercut anchor

e1 distance between shear load and concrete surface (see Figure 5.13)

eN,e (eV,e) eccentricity of the external tension (shear) force in respect to the centre of gravity of a fastening (external eccentricity)

eccentricity of the resultant tension (shear) force of the tensioned (sheared) fastenings in respect to the centre of gravity of the tensioned (sheared) fasteners of a fastening (internal eccentricity)

h thickness of concrete member in which the fastener is installed (see Figure 3.1)


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hef effective embedment depth (see Figure 3.2)

hmin minimum thickness of concrete member

l lever arm of the shear force acting on a fastener

n number of fasteners in a group

s centre to centre spacing of fasteners in a group (see Figure 3.1) or spacing of reinforcing bars

s1 (s2) spacing of fasteners in a group in direction 1 (direction 2) (see Figure 3.1)

scr spacing for ensuring the transmission of the characteristic resistance of a single fastener

scr,b spacing for ensuring the transmission of the characteristic tension resistance of a single fastener without spacing, edge and member thickness effects in case of concrete blow-out failure

scr,N spacing for ensuring the transmission of the characteristic tension resistance of a single fastener without spacing and edge effects in case of concrete cone failure

scr,sp spacing for ensuring the transmission of the characteristic tension resistance for concrete cone failure of a single fastening without spacing and edge effects in case of splitting failure

scr,V spacing for ensuring the transmission of the characteristic shear resistance of a single fastener without spacing, corner and member thickness effects in case of concrete failure

smin minimum allowable spacing to avoid splitting of the concrete during installation and loading of the fastener and to achieve sound concreting in case of cast-in fasteners

t thickness of washer or plate

tfix thickness of fixture


Figure 3.1 — Definitions related to concrete member dimensions, fastener spacing and edge distance (a) fastenings subjected to tension load

(b) fastenings subjected to shear load in the case of fastening near an edge, indices 1 and 2 depend on the direction of the shear load

1: in direction of shear load 2: perpendicular to direction of shear load

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≤ 0,5 hef

hef

a) b) c)

Figure 3.2 — Definition of effective embedment depth hef a) without anchor plate

b) with a large anchor plate c) with a small anchor plate

3.2.4 Units

In this Standard SI-units are used. Unless stated otherwise in the equations the following units are used: Dimensions are given in mm, cross sections in mm2, section modulus in mm3, forces and loads in N and stresses in N/mm².

ard SI-units are used. Unless stated otherwise in the equations the following units are used: Dimensions are given in mm, cross sections in mm2, section modulus in mm3, forces and loads in N and stresses in N/mm².

4 Basis of design 4 Basis of design

The required verifications, the design format and the partial safety factors given in Section 4 of the TS ''Design of fastenings for use in concrete', Part 1, 'General' shall apply. The required verifications, the design format and the partial safety factors given in Section 4 of the TS ''Design of fastenings for use in concrete', Part 1, 'General' shall apply.

5 Determination of action effects 5 Determination of action effects

5.1 General 5.1 General

5.1.1 The general basis on the determination and analysis of action effects is given in Section 5 of the Technical Specification 'Design of fastenings for use in concrete', Part 1, 'General'. 5.1.1 The general basis on the determination and analysis of action effects is given in Section 5 of the Technical Specification 'Design of fastenings for use in concrete', Part 1, 'General'.

5.1.2 The condition of the concrete – cracked or non-cracked - serving as base material for the fastener shall be decided by the designer on the basis of national regulations. 5.1.2 The condition of the concrete – cracked or non-cracked - serving as base material for the fastener shall be decided by the designer on the basis of national regulations.

5.1.3 In general, the action effects on a fastening at the concrete surface may be calculated according to an elastic analysis from the action effects on the fixture. In special cases a plastic analysis is allowed, if the conditions of Annex B, Technical Specification 'Design of fastenings for use in concrete', Part 1, 'General' are fulfilled.

5.1.3 In general, the action effects on a fastening at the concrete surface may be calculated according to an elastic analysis from the action effects on the fixture. In special cases a plastic analysis is allowed, if the conditions of Annex B, Technical Specification 'Design of fastenings for use in concrete', Part 1, 'General' are fulfilled.

5.2 Tension loads 5.2 Tension loads

5.2.1 The tension loads acting on each fastener due to loads and bending moments acting on the fixture may be calculated assuming a linear distribution of strains across the fixture and a linear relationship between strains and stresses i.e. this implies that the fixture is sufficiently stiff and does not deform under the actions. If the fixture bears on the concrete with or without a grout layer the compression forces are transmitted to the concrete by the fixture. The load distribution to the fasteners may be calculated analogous to the elastic analysis of reinforced concrete (see Figure 5.1):

5.2.1 The tension loads acting on each fastener due to loads and bending moments acting on the fixture may be calculated assuming a linear distribution of strains across the fixture and a linear relationship between strains and stresses i.e. this implies that the fixture is sufficiently stiff and does not deform under the actions. If the fixture bears on the concrete with or without a grout layer the compression forces are transmitted to the concrete by the fixture. The load distribution to the fasteners may be calculated analogous to the elastic analysis of reinforced concrete (see Figure 5.1):


a) The axial stiffness ESAS of all fasteners is equal. In general AS may be based on the nominal diameter of the fastener and ES = 210,000 N/mm². For threaded fasteners the stressed cross section according to ISO 898 shall be taken.

b) The modulus of elasticity of the concrete may be taken from EN 1992-1. As a simplification, the modulus of elasticity of concrete may be assumed as Ec = 30,000 N/mm².

c) In the zone of compression under the fixture, the fasteners do not take forces.

In case of a stand-off installation the forces on the fasteners shall be calculated according to the theory of elasticity.

Figure 5.1 — Fastening with a rigid fixture bearing on the concrete loaded by a bending moment and a normal force

5.2.2 For fastener groups with different levels of tension forces N acting on the individual fasteners of a

group the eccentricity esi

N of the tension force N of the group may be calculated (see Figure 5.2). If the tensioned fasteners do not form a rectangular pattern (see Fig. 5.2c) for reasons of simplicity the group of fasteners may be resolved into a group rectangular in shape to calculate the eccentricity i.e. the centre of gravity may be assumed in Fig.5.2c, point 'A'. This simplification will lead to a larger eccentricity.

gs

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AA

Figure 5.2 — Examples of fastenings subjected to an eccentric tensile force Ns Figure 5.2 — Examples of fastenings subjected to an eccentric tensile force Ns (a) eccentricity in one direction, (a) eccentricity in one direction,

all fastenings are loaded by a tension force all fastenings are loaded by a tension force (b) eccentricity in one direction, (b) eccentricity in one direction,

only a part of the fastenings of the group are loaded by a tension force only a part of the fastenings of the group are loaded by a tension force (c) eccentricity in two directions, (c) eccentricity in two directions,

only a part of the fastenings of the group are loaded by a tension force only a part of the fastenings of the group are loaded by a tension force

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Msyksd ff5.2.3 The assumption of a linear distribution of strains is valid only if the fixture is rigid. The fixture may be assumed as rigid, if the steel stress in the fixture under the design actions is less than 5.2.3 The assumption of a linear distribution of strains is valid only if the fixture is rigid. The fixture may be assumed as rigid, if the steel stress in the fixture under the design actions is less than Msyksd ff γ/≤ with

. When calculating the stresses in the fixture by an elastic analysis the stresses averaged over 2-times the fixture thickness shall be taken as decisive, see Fig. 5.3.

1.1=Msγ


Figure 5.3 — Calculation of the mean bending moment in the fixture

5.3 Shear loads

5.3.1 Distribution of shear loads

The distribution of shear loads between the fasteners shall be calculated taking into account

- the geometrical layout of the fasteners in relation to the line of action of the applied shear; and

- the effectiveness of the fasteners controlled by the hole clearance in the fixture and by the edge distance of the fastener

- torsional moments.

Some of the fasteners may have to be considered ineffective based on these criteria.

The distribution of shear loads to the individual fasteners of a group resulting from shear forces and torsional moments acting on the fixture depends on the effectiveness of the fasteners controlled by the hole clearance in the fixture and by the edge distance of the fastener. A distinction is made between fasteners welded or threaded with the fixture and fasteners with hole clearance. Furthermore fasteners close to an edge where concrete edge failure may occur (c ≤ 10 hef), and fasteners with large edge distances where no edge failure has to be considered (c > 10 hef) are distinguished (see Table 5.1). Permissible values for the hole clearance are compiled in Table 5.2.

If the diameter of the clearance hole in the fixture is larger than the values given in Table 5.2, line 2 it is assumed that all fasteners take up shear loads but the fasteners are loaded by a bending moment (shear load with lever arm). The maximum oversize of the clearance hole is given in Table 5.2, line 3. Larger values are not covered by the design methods given in this Standard.

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In cases where two fasteners in a group are loaded by a shear force acting perpendicular to the group axis and/or by a torsional moment and the clearance hole is larger than given in Table 5.2, line 2 and smaller than the value from Table 5.2, line 3 both fasteners can be assumed to carry shear loads (see Figure 5.6a) because after a displacement of the fixture, both fasteners will come into contact with the fixture. The bending moment can be neglected.

Table 5.1 ⎯ Conditions of application

Edge distance

Hole clearance Distribution of shear load

c ≤ 10 hef --- Steel failure: Fig. 5.5 proof without lever arm 1)

Edge failure: Fig. 5.8 Pryout failure: Fig. 5.5

Fasteners welded or threaded with the fixture

c > 10 hef --- Steel failure: Fig. 5.5 proof without lever arm 1)

Pryout failure: Fig. 5.5

df ≤ Table 5.2, line 2 Steel failure: Fig. 5.5 proof without lever arm 1)

Edge failure: Fig. 5.6 + 5.7 Pryout failure: Fig. 5.5

c ≤ 10 hef

df > Table 5.2, line 2 anddf ≤ Table 5.2, line 3

Steel failure: Fig. 5.5 proof with lever arm 2)

Edge failure: Fig. 5.6 + 5.7 Pryout failure: Fig. 5.5

df ≤ Table 5.2, line 2 Steel failure: Fig. 5.5 proof without lever arm 1)


Fasteners with hole clearance

c > 10 hef

df > Table 5.2, line 2 anddf ≤ Table 5.2, line 3

Steel failure: Fig. 5.5 proof with lever arm 2)


1) see section 5.3.3 2) see section 5.3.4

Table 5.2 — Hole clearance

1 external diameter d1) [mm] 6 8 10 12 14 16 18 20 22 24 27 30

2 diameter df of clearance hole in the fixture [mm] 7 9 12 14 16 18 20 22 24 26 30 33

3 maximum allowable diameter df of clearance hole in the fixture2) [mm] 8 10 14 16 18 20 22 24 26 28 33 36

4 1) if bolt bears against the fixture (Figure 5.5) 2) it is assumed that all fasteners of a group take up shear loads


df ≤ value acc. Table 5.2

Figure 5.4 — Examples of fastenings with a large edge distance with a clearance hole in the fixture where all fasteners will contribute to the transmission of shear forces

Figure 5.4 — Examples of fastenings with a large edge distance with a clearance hole in the fixture where all fasteners will contribute to the transmission of shear forces

Examples for the resulting load distributions are shown in Figure 5.5. Examples for the resulting load distributions are shown in Figure 5.5.

Figure 5.5 — Examples of load distribution, when all fasteners take up shear loads

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V

0.5VV 0.5VV

0.25VH

0.25VH

(c)

V

0.25VH

0.25VH

Edge

0.5VH

0.5VH

VV

(d)

Figure 5.6 — Examples of load distribution for fastenings close to an edge or corner of the concrete member

If the edge distance is small (c ≤ 10hef) so that concrete edge failure will occur and steel failure and concrete pry-out failure are precluded the cases given in Figure 5.6 shall be distinguished:

Figures 5.6 (a) and (b) show groups of fasteners with a hole clearance in the fixture. In this case only the fasteners closest to the edge are assumed to carry shear loads.

Note:

When there is a clearance hole in the fixture, in general a shear load will not be equally distributed to all fastenings of a group, because some fastenings may already be loaded almost to failure before other fastenings come into contact with the fixture. This is especially valid for fastenings close to an edge, because they may fail at rather small displacements. To account for this, it should be assumed that only the most unfavourable fastenings take up load. This assumption is on the safe side.

Figs 5.6c and 5.6d show a group of 4 and 2 fasteners respectively close to an edge loaded by a shear load not acting perpendicularly to the edge. In this case the anchor(s) closest to the edge bear the entire vertical shear load VV and 50 % of the horizontal shear load VH. The remaining horizontal shear load is for reasons of equilibrium carried by the anchor(s) furthest to the edge which are considered not being decisive for the proof of concrete edge failure.

19


V*H4

MT

V

1 2 VV2

3

4

VV1

VH2

VH3 VH4

VV3

3

4

V*H3

V*V4

V*V3

⇒VV4

VH1

Figure 5.7 — Examples of concrete

Figure 5.7 — Examples of concrete

If a group of anchors is loadfasteners may alter within theacting away from the edge mthis assumption the following

If a group of anchors is loadfasteners may alter within theacting away from the edge mthis assumption the following

Anchor 3: V*V3 = 0Anchor 3: V*V3 = 0

Anchor 4: V*V4 = VAnchor 4: V*V4 = V

If the fasteners are welded toto carry shear loads (see FiguIf the fasteners are welded toto carry shear loads (see Figu

Note: Note:

For fastenings welded, frictionoccur in the fastenings closesinitiated in the fastening(s) fassociated with the failure of t

For fastenings welded, frictionoccur in the fastenings closesinitiated in the fastening(s) fassociated with the failure of t

Figure 5.8 — Examples of Figure 5.8 — Examples of

20 20

(a)

load distribution, for fasteners with hole clearanc member loaded by a shear force and a torsion mload distribution, for fasteners with hole clearanc member loaded by a shear force and a torsion m

ed by a shear force and a torsion moment, the d group (Fig. 5.7a). For the proof of concrete edge faiay be altered and only 50 % of the load may be coloads act on the two anchors 3 and 4 close to the ed

ed by a shear force and a torsion moment, the d group (Fig. 5.7a). For the proof of concrete edge faiay be altered and only 50 % of the load may be coloads act on the two anchors 3 and 4 close to the ed

.5 ⋅ (VV1 + VV3) V*H3 = VH3.5 ⋅ (VV1 + VV3) V*H3 = VH3

V2 + VV4 V*H4 = VH4 V2 + VV4 V*H4 = VH4

or threaded into the fixture, only the fasteners furthere 5.8). or threaded into the fixture, only the fasteners furthere 5.8).

bolted, or otherwise securely attached to the fixturet to the free edge, and the peak load will be reachedurthest from the edge. If the fastening spacing he fastening(s) furthest from the edge may be small.

bolted, or otherwise securely attached to the fixturet to the free edge, and the peak load will be reachedurthest from the edge. If the fastening spacing he fastening(s) furthest from the edge may be small.

load distribution for fasteners with welded fastenthe concrete member

load distribution for fasteners with welded fastenthe concrete member

(b)

e close to an edoment e close to an edoment

irection of the lolure the direction nsidered (Fig. 5.

ge:

irection of the lolure the direction nsidered (Fig. 5.

ge:

st to the edge arst to the edge ar

, concrete failure when concrete

is small, the loa

, concrete failure when concrete

is small, the loa

ings close to anings close to an

Edge

ge of the ge of the

ad on the of the load 7b). Under

ad on the of the load 7b). Under

e assumed e assumed

will initially breakout is d increase

will initially breakout is d increase

edge of edge of


The positioning of slotted holes in the fixture parallel to the direction of the shear load can be used to prevent particular fasteners in the group from carrying load (Figure 5.9). This method can be used to relieve fasteners close to an edge which would otherwise cause a premature edge failure.

Figure 5.9 — Example of load distribution for an fastening with slotted holes

5.3.2 Eccentricity of shear loads

In the case of groups of fasteners with different levels of shear forces acting on the individual fasteners of

the group, the eccentricity of the shear force of the group may be calculated (see Figure 5.10). siV

ve gsV

Figure 5.10 — Example of a fastening subjected to an eccentric shear load

5.3.3 Shear loads without lever arm

Independent of the hole clearance shear loads acting on fastenings may be assumed to act without a lever arm if all of the following conditions are fulfilled:

1) The fixture must be made of metal and in the area of the fastening be fixed directly to the concrete without an intermediate layer or with a levelling layer of mortar with a thickness ≤ d/2

2) The diameter of the clearance hole is not greater than the values given in Table 5.2, line 2.

21


5.3.4 Shear loads with lever arm

If the conditions 1) and 2) of Section 5.3.2 are not fulfilled or if a proof of shear loads with lever arm is required (see Table 5.1), the lever arm is calculated according to Equation (5.2).

13 eal += (5.2)

with

1e distance between shear load and concrete surface

3a = 0,5 d, see Figure 5.11a = 0 if a washer and a nut are directly clamped to the concrete surface, see Figure 5.11b

or in the presence of a levelling grout layer of a thickness > d/2 d nominal diameter of the bolt or thread diameter, see Figure 5.11a

Figure 5.11 — Lever arm

The design moment acting on the fastening is calculated according to Equation (5.3)

MSdSd

lVMα⋅= (5.3)

The value depends on the degree of restraint of the fastening at the side of the fixture of the application in question and should be determined according to good engineering practice. No restraint ( ) should be assumed if the fixture can rotate freely (see Figure 5.12a). Full restraint ( ) may be assumed only if the fixture can not rotate (see Figure 5.12b) and the hole clearance in the fixture is smaller than the values given in Table 5.2, line 3 or the fixture is clamped to the fastening by nut and washer (see Figure 5.11b). If restraint of the fastening is assumed the fixture and/or the fastened element must be able to take up the restraint moment.

Mα0.1=Mα

0.2=Mα

Figure 5.12 — Examples of fasteners without and with full restraint of the fastener at the side of the fixture

22


5.4 Tension forces of a special supplementary reinforcement

5.4.1 Tension loads

The design action of the special supplementary (hanger) reinforcement shall be calculated for the design load of the fastener. If the hanger reinforcement is not arranged symmetrical to the fastener, the moment due to the tension forces should be taken up by additional reinforcement.

5.4.2 Shear loads

5.3.2.1 The design tension force Tsd in the supplementary reinforcement to take up the design shear force Vsd acting on a fixture is given by Equation 5.4.

)1( +=z

eVT s

sdsd (5.4)

with (see Figure 6.12):

se = distance between reinforcement and shear force acting on a fixture

z = internal lever arm of the concrete member

≈ 0,85h

with: ⎪⎩

⎪⎨⎧

≤12

2min

c

hh ef

5.3.2.2 If the supplementary reinforcement is not arranged in the direction of the shear force (see Figure 6.11 c) then this must be taken into account in the calculation of the design tension force of the reinforcement.

5.3.2.3 If the shear loads on the fasteners of a fastener group are different, Equation 5.4 should be solved for the shear load Vsd of the most loaded fastener.

6 Verification of ultimate limit state by elastic analysis

6.1 General

6.1.1 The loads on fastenings are calculated according to elastic analysis or in special cases plastic analysis. Section 6.2 is valid for elastic analysis, information on plastic analysis is given in Annex B of Part 1 'General' of this Technical Specification.

6.1.2 In this Section it is assumed that the forces on the fasteners of a group are calculated according to Section 5.

6.1.3 According to Section 4 it shall be shown that the design value Ed of the action is equal to or smaller than the design value of the resistance Rd.

6.1.4 The spacing between outer headed fasteners of adjoining groups or the distance to single fasteners shall be a > scr,N .

23


6.2 Tension loads

6.2.1 Required proofs

The required proofs for headed fasteners without supplementary reinforcement are given in Tables 6.1.

The most loaded fastener is verified for the failure modes 1 and 2 and the combined effect of all tensioned fasteners is verified for failure modes 3, 4 and 5.

Table 6.1 — Required proofs for headed fasteners without supplementary reinforcement

Fastener group2)

Single fastener

most loaded fastener fastener group

1 Steel failure NSd ≤ NRd,s = NRk,s / γMs NhSd ≤ NRd,s = NRk,s / γMs

2 Pull-out NSd ≤ NRd,p = NRk,p / γMp NhSd ≤ NRd,p = NRk,p / γMp

3 Concrete cone failure NSd ≤ NRd,c = NRk,c / γMc NgSd ≤ NRd,c = NRk,c / γMc

4 Splitting failure NSd ≤ NRd,sp = NRk,sp / γMc NgSd ≤ NRd,sp = NRk,sp / γMc

5 Blow-out failure1) NSd ≤ NRd,cb = NRk,cb / γMc NgSd ≤ NRd,cb = NRk,cb / γMc

1) Not required for fasteners with c > 0.5hef

2) Proof is performed only for the tensioned fasteners of a group

6.2.2 Steel failure

The characteristic resistance of a fastener in case of steel failure, NRk,s, is given in the relevant ETA or CEN Standard. The strength calculations are based on . ukf

6.2.3 Pull-out failure

The characteristic resistance in case of pull-out failure NRk,p is given in the relevant ETA or in a CEN Standard.

Comment:

Equation of ACI 318, App. D ????

6.2.4 Concrete cone failure

The characteristic resistance of a fastener, a group of fasteners and the tensioned fasteners of a group of fasteners in case of concrete cone failure may be obtained by Equation (6.1).

NucrNecNreNsoNc

NcocRkcRk

A

ANN ,,,,

,

,,, ψψψψ ⋅⋅⋅⋅⋅= [N] (6.1)

The different factors of Equation (6.1) are given below.

24


6.2.4.1 Characteristic resistance of a single fastener 6.2.4.1 Characteristic resistance of a single fastener

The characteristic resistance of a single fastener not influenced by adjacent fasteners or edges of the concrete member placed in cracked concrete is obtained by: The characteristic resistance of a single fastener not influenced by adjacent fasteners or edges of the concrete member placed in cracked concrete is obtained by:

5,1,1, efcubeck

ocRk hfkN ⋅⋅= [N] (6.1a)

with: k1 factor to take into account the influence of load transfer mechanisms. For headed fasteners according to current experience the value shall be 8,5. The actual value for a particular fastener may be taken from the relevant ETA or CEN Standard.

fck, [N/mm2] the minimum and maximum value of the concrete strength to be inserted in Equ. (6.1a) is given in the relevant ETA or CEN Standard.

hef [mm] see Figure 3.2.

Note:

If values of > 8.5 shall be used, it has to be demonstrated that the values c1k cr, scr, the ratio cracked to uncracked concrete and the minimum distances to avoid splitting failure correspond to the design method given in this Standard.

6.2.4.2 Geometric effect of axial spacings and edge distances

The geometric effect of axial spacings and edge distances on the characteristic resistance is taken into account by the value , where o

NcNc AA ,, /

oNcA , : see Figure 6.1

= scr,N ⋅ scr,N (6.1b)

NcA , actual area, limited by overlapping concrete cones of adjacent fasteners (s < scr,N) as well as by edges of the concrete member (c < ccr,N). Examples for the calculation of Ac,N are given in Figure 6.2.

scr,N, ccr,N given in the corresponding ETA or CEN Standard

NcrNcro

Nc ssA ,,, ⋅=

concrete cone

Figure 6.1 — Idealized concrete cone and area of concrete cone of an individual fastener oNcA ,

25 25


)

Figure 6.2

a) Inb) Gc) G

6.2.4.3 Effect o

The factor Ns,ψ taof the concrete memember or in a nar

07.0, +=Nsψ

26

a

)
b c)
— Examples of actual areas of the idealised concrete cones for different arrangements of fasteners in case of axial tension load

NcA ,

dividual fastener at the edge of a concrete member roup of two fasteners at the edge of a concrete member roup of four fasteners at a corner of a concrete member

f the disturbance of the distribution of stresses in the concrete due to edges

kes account of the disturbance of the distribution of stresses in the concrete due to edges mber. For fastenings with several edge distances (e.g. fastening in a corner of the concrete row member), the smallest edge distance, c, shall be inserted in Equation (6.1c).

13.,

≤⋅Ncrc

c [-] (6.1c)


6.2.4.4 Effect of shell spalling

The shell spalling factor Nre,ψ takes account of the effect of a dense reinforcement for embedment depths hef < 100 mm:

1200

50 ≤+= efre,N

h.ψ [-] (6.1d)

with: hef [mm]

If in the area of a fastener there is a reinforcement with a spacing > 150 mm (any diameter) or with a diameter < 10 mm and a spacing > 100 mm then a shell spalling factor of Nre,ψ = 1 may be applied independently of the fastening depth.

6.2.4.5 Effect of the eccentricity of the load

The factor Nec,ψ takes account of a group effect when different tension loads are acting on the individual fasteners of a group.

1/21

1,

, ≤⋅+

=NcrN

Nec seψ [-] (6.1e)

with: eN: eccentricity of the resulting tensile load acting on the tensioned fasteners (see Section 5.2).

Where there is an eccentricity in two directions, Nec,ψ shall be determined separately for each direction and the product of both factors shall be inserted in Equation (6.1).

6.2.4.6 Effect of the position of the fastening

The factor Nucr,ψ takes account of the position of the fastening in cracked or non-cracked concrete.

Nucr,ψ = 1.0 for fasteners in cracked concrete (6.1f1)

= 1,4 for fasteners in non-cracked concrete

6.2.4.7 Characteristic axial and edge spacings

The values scr,N and ccr,N are given in the relevant ETA or in a CEN Standard.

Note:

For headed fasteners according to current experience scr,N = 2ccr,N = 3hef shall be taken.

6.2.4.8 Special cases

6.2.4.8.1 For the special case of fasteners in an application with three or more edges located with an edge distance less than efhc ⋅= 5,1max from the fasteners (see Figure 6.3) the calculation according to Equation (6.1) leads to results which are on the safe side.

6.2.4.8.2 For fasteners with headed fasteners, more precise results are obtained if the value hef is limited to

27


5,1max' c

hef = (6.1g1)

but not less than one-third of the maximum spacing between fasteners for groups of fasteners and is inserted in Equation (6.1a) and for the determination of and according to Figures 6.1 and 6.2 as well as in Equations (6.1b), (6.1c) and (6.1e) the values

oNcA , NcA ,

',

', 2 NcrNcr cs = (6.1g2)

max'

, cc Ncr = (6.1g3)

are inserted for scr,N or ccr,N, respectively.

Figure 6.3 — Examples for fastenings in concrete members where , and may be used 'efh '

,Ncrs ',Ncrc

a) (c1; c2,1; c2,2) ≤ ccr,N

b) (c1,1; c1,2; c2,1; c2,2) ≤ ccr,N

6.2.5 Splitting failure due to loading

Splitting failure due to loading shall be taken into account according the following rules. The characteristic values of edge distance and spacing in the case of splitting under load, and are given in the relevant ETA:

spcrc , spcrs ,

6.2.5.1 No proof of splitting failure is required if at least one of the following conditions a) or b) is fulfilled:

a) The edge distance in all directions is c > 1.0 ccr,sp for single fasteners and c > 1.5 ccr,sp for fastener groups and the member depth is h > 2 hef in both cases.

b) With fasteners in cracked concrete, the characteristic resistance for concrete cone failure and pull-out failure is calculated for cracked concrete and reinforcement limits the crack width to wk ≤ 0.3 mm.

6.2.5.2 If the conditions a) and b) are not fulfilled, then the characteristic resistance of a headed fastener, a group of fasteners in case of splitting failure should be calculated according to Equation (6.2).

sphNucrNecNreNsoNc

NcocRkspRk

A

ANN ,,,,,

,

,,, ψψψψψ ⋅⋅⋅⋅⋅⋅= (6.2)

with , ocRkN , Ns,ψ , Nre,ψ , Nec,ψ , Nucr,ψ according to chapter 6.2.2.4, however the values ccr,N and scr,N should

be replaced by ccr,sp and scr,sp . and are based on a member thickness . spcrc , spcrs , minh

28


29 29

sph,The factor The factor sph,ψ takes into account the influence of the actual member depth, h, on the splitting resistance for fasteners according to current experience.

5,12

3/2

, ≤⎟⎟⎠

⎞⎜⎜⎝

⎛

⋅=

efsph h

hψ (6.2a)

If the edge distance of an fastener is smaller than the value ccr,sp then a longitudinal reinforcement should be provided along the edge of the member.

6.2.6 Blow-out failure

Blow-out failure may occur with fasteners when the distance between the anchorage area and the side surface of the structural component is c < 0.5 ⋅ hef. The characteristic resistance in case of blow-out failure is:

NucrNbecNbgNbsoNbc

NbcocbRkcbRk

A

ANN ,,,,

,

,,, ψψψψ ⋅⋅⋅⋅⋅= [N] (6.3)

The different factors of Equation (6.3) for fasteners according to current experience are given below:

6.2.6.1 Characteristic resistance of a single anchor

The characteristic resistance of a single anchor, not influenced by adjacent fasteners or free structural component edges placed in cracked concrete is obtained by:

cubeckho

cbRk fAcN ,1, 8 ⋅⋅⋅= [N] (6.3a)

with: fck,cube [N/mm2] Ah [mm2] c1 [mm]

Ah is the load bearing area of the stud.

)(4

22 ddA hh −⋅=π (6.3b)

6.2.6.2 Geometric effect of axial spacings and edge distances

The geometric effect of axial spacings and edge distances on the characteristic resistance is taken into account by the value , where o

NbcNbc AA ,, /

oNbcA , : see Figure 6.4

= (4 c1)² (6.3c)

NbcA , : actual area, limited by overlapping concrete break-out bodies of adjacent fasteners (s < 4c1) as well as by edges of the concrete member (c < 2 ⋅ c1 ). Examples for the calculation of Ac,Nb are given in Figure 6.5.


2c1

4c1

4c1

30 30

oNbcA ,Figure 6.4 — Idealized concrete break-out body and area of an individual fastener

in case of blow-out failure Figure 6.4 — Idealized concrete break-out body and area of an individual fastener

in case of blow-out failure

oNbcA ,

Ac,Nb= 4c1(4c1+s) s ≤ 4c14c

1

2c1 2c1

Ac,Nb= 4c1(c1+s+2c1) c2 ≤ 2c1

s ≤ 4c1

4c1

2c1

ffAc,Nb= (2c1+f)1(4c1+s) f ≤ 2c1

s ≤ 4c1

2c1

2c1 2c1

Figure 6.5 — Examples of actual areas of the idealised concrete arrangements of fasteners in case of blow-o

NbcA ,

6.2.6.3 Effect of the disturbance of the distribution of stresses in the c

The factor Nbs,ψ takes account of the disturbance of the distribution of strcorner of the concrete member. For fastenings with several edge distances concrete member), the smallest edge distance, c2, shall be inserted in Equatio

break-out bodies for different ut

oncrete due to a corner

esses in the concrete due to a (e.g. fastening in a corner of the n (6.3d).


12

3.07.01

2, ≤⋅+=

cc

Nbsψ (6.3d)

6.2.6.4 Effect of the bearing area on the behaviour of groups

The factor Nbg,ψ takes account of the bearing areas of the individual fasteners of a group.

14

)1(1

1, ≥⋅−+=

cs

nnNbgψ , (6.3e) Nbcrss ,1 ≤

6.2.6.5 Effect of the eccentricity of the load

The factor of Nbec,ψ takes account of a group effect when different loads are acting on the individual fasteners of a group.

14/21

1

1, ≤

⋅+=

ceNNbecψ (6.3f)

with: eN: eccentricity of the resulting tensile load acting on the tensioned fasteners.

6.2.6.6 Effect of the position of the fastening

The factor of Nucr,ψ takes account of the position of the fastening in cracked or non-cracked concrete.

Nucr,ψ = 1.0 for fastenings in cracked concrete (6.3g1)

= 1.4 for fastenings in non-cracked concrete (6.3g2)

6.2.7 Detailing of supplementary reinforcement

6.2.7.1 General

Where the load in the fastener exceeds the resistance for concrete cone failure given by Equation (6.1), supplementary reinforcement shall be provided to take the total load. The reinforcement should be anchored adequately in both sides of the potential failure planes.

For fastenings with supplementary reinforcement to take up tension forces the minimum embedment depth is hef = 150 mm and the minimum edge distance in all directions c = 1.5 hef.

The supplementary reinforcement to take up tension loads should comply with the following requirements (see also Figure 6.6):

a) In general, for all fasteners of a group the same diameter of the reinforcement should be provided. It should consist of ribbed reinforcing bars (fyk ≤ 500 N/mm2) with a diameter not larger than 16 mm and should be detailed in form of stirrups or loops with a bending diameter according to EN 1992-1-1.

b) The supplementary reinforcement shall be located such that l1 of the reinforcement bars lies within the failure cone. The supplementary reinforcement shall be placed as close to the fasteners as practicable to minimize the effect of eccentricity associated with the angle of the failure cone. Preferably , the supplementary reinforcement should enclose the surface reinforcement. Only these reinforcement bars with a distance ≤ 0,75,0 hef, from the fastener should be assumed active.

c) The supplementary reinforcement shall be anchored outside the assumed failure cone with an anchorage length lbd according to EN 1992-1-1.

31


d) A surface reinforcement should be present, which limits the width of cracks to a normal value (wk ≈ 0.3 mm), taking into account the splitting forces according to Section 6.2.2.6.2. d) A surface reinforcement should be present, which limits the width of cracks to a normal value (wk ≈ 0.3 mm), taking into account the splitting forces according to Section 6.2.2.6.2.

For fastenings parallel to the edge of a concrete member or in a narrow concrete member the plane of the supplementary reinforcement shall be placed perpendicular to the edge. For fastenings parallel to the edge of a concrete member or in a narrow concrete member the plane of the supplementary reinforcement shall be placed perpendicular to the edge.

Figure 6.6 — Example for a quadr

6.2.7.2 Required proofs

The following proofs are required (Ta

Table 6.2 — Verifica

Steel failure N

Pull-out N

Splitting N

Steel failure of supplementary reinforcement

N

Anchorage failure of supplementary reinforcement

1) Proof is performed only for the tensioned fa

a) Steel failure of fasteners: For stee

b) Pull-out failure of fasteners: For p

c) Splitting failure: For splitting failu

d) Steel failure of the supplementary

The characteristic resistance of thefailure is

32 32

≤ 0,75 hef

uple fastening with supplementary reinforcement to take up tension loads

ble 6.2):

tions for fasteners with supplementary reinforcement

Fastener groups1) Single fastener most loaded fastener fastener group

Sd ≤ NRd,s = NRk,s / γMs NhSd ≤ NRd,s = NRk,s / γMs

Sd ≤ NRd,p = NRk,p / γMp NhSd ≤ NRd,p = NRk,p / γMp

Sd ≤ NRd,sp = NRk,sp / γMc NgSd ≤ NRd,sp = NRk,sp / γMc

Sd ≤ NRd,s1 = NRk,s1 / γMs NhSd ≤ NRd,s1 = NRk,s1 / γMs

NSd ≤ NRd,a NhSd ≤ NRd,a

steners of a group

l failure of fasteners Section 6.2.2 applies.

ull-out failure Section 6.2.3 applies.

re Sections 6.2.5 applies.

reinforcement:

supplementary reinforcement, NRk,s1, for one fastener in case of steel


ykssRk fAnN ⋅⋅= 11, (6.4)

with: As = cross section of one bar of the supplementary reinforcement fyk = nominal yield strength of the supplementary reinforcement n1 = number of legs of the supplementary reinforcement of one anchor

e) Anchorage failure of the supplementary reinforcement in the concrete cone

The design resistance, NRd,a, of the supplementary reinforcement of one fastener in case of an anchorage failure in the concrete cone is given by

∑ ⋅⋅=1

/1,n

bdaRd fulN α (6.5)

with: l1 = length of the supplementary reinforcement in the assumed failure cone (see Figure 6.6) = hef – c – x ≥ lb,min , lb,min according to EN 1992-1-1 u = circumference of the bar = π ⋅ d

= design bond strength according to EN 1992-1-1, taking into account the concrete cover of the supplementary reinforcement

bdf

n1 = number of legs of the supplementary reinforcement of one fastener

α = factor, that takes into account the efficiency of the anchorage, according to EN 1992-1-1 = 0,7 for hooks and bends or transverse bars welded to the hanger reinforcement

6.3 Shear load

6.3.1 Required proofs

The proofs given in Table 6.3 are required.

Table 6.3 — Verification for headed anchors

Fastener groups1)

Single fastener most loaded fastener fastener group

Steel failure without lever arm

VSd ≤ VRd,s = VRk,s / γMs VhSd ≤ VRd,s = VRk,s / γMs

Steel failure with lever arm

VSd ≤ VRd,s = VRk,s / γMs VhSd ≤ VRd,s = VRk,s / γMs

Pryout failure VSd ≤ VRd,cp = VRk,cp / γMc VgSd ≤ VRd,cp = VRk,cp / γMc

Concrete edge failure VSd ≤ VRd,c = VRk,c / γMc VgSd ≤ VRd,c = VRk,c / γMc

1) Proof is performed only for the tensioned fasteners of a group

6.3.2 Steel failure

6.3.2.1 Shear load without lever arm

For headed fasteners welded or not welded to a steel fixture the characteristic resistance of a fastener in case of steel failure, VRk,s, is given in the relevant ETA or in a CEN Standard. In case of groups with fasteners made of non-ductile steel, this characteristic shear resistance shall be multiplied with the factor k3. The factor k3 is given in the relevant ETA or CEN Standard.

Note:

33


According to current experience the factor k3 for non-ductile steel is k3= 0,8.

6.3.2.2 Shear load with lever arm

The characteristic resistance of a headed fastener not welded to a steel plate in case of steel failure, VRk,s, may be obtained from Equation (6.6).

lM

V sRkMsRk

,,

⋅=α

[N] (6.6)

with: αM: see 5.3.4 l: lever arm according to Equation (5.2)

= (6.6a) sRkM , )/1( ,, sRdSdo

sRk NNM −⋅

NRd,s = MssRkN γ/,

The characteristic resistance under tension load in case of steel failure, NRk,s, the partial safety factor γMs and the characteristic bending resistance of a single headed fastener , are given in the relevant ETA or a CEN Standard.

osRkM ,

6.3.3 Concrete pry-out failure

Fastenings may fail due to a concrete pry-out failure at the side opposite to load direction. The corresponding characteristic resistance VRk,cp may be calculated from Equation (6.7).

cRkcpRk NkV ,4, ⋅= [N] (6.7)

with: k4: factor to be taken from the relevant ETA or a CEN Standard NRk,c: according to 6.2.4 determined for the fasteners loaded in shear.

6.3.4 Concrete edge failure

6.3.4.1 General

6.3.4.1.1 For fastenings with an edge distance in all directions c > 10 hef or c > 60 d (smaller value is decisive), a check of the characteristic concrete edge failure resistance may be omitted.

6.3.4.1.2 For fastenings with more than one edge, the resistances for all edges shall be calculated and the smallest value is decisive.

6.3.4.2 Characteristic resistance

The characteristic resistance for a fastener or a fastener group corresponds to:

VucrVecVVhVsoVc

VcocRkcRk

A

AVV ,,,,,

,

,,, ψψψψψ α ⋅⋅⋅⋅⋅⋅= [N] (6.8)

The different factors of Equation (6.8) for headed anchors according to current experience are given below.

6.3.4.2.1 Characteristic resistance of a single anchor

The initial value of the characteristic resistance of a headed fastener loaded perpendicular to the edge in cracked concrete corresponds to:

34


5.11,

2.0

, 45.0 cfd

ldV cubeck

nom

fnom

ocRk ⋅⋅⎟

⎟⎠

⎞⎜⎜⎝

⎛⋅⋅= [N] (6.8a)

with: dnom, lf, c1 [mm], dnom ≤ 30 mm, , lf / dnom ≤ 8 fck,cube [N/mm2]

The values dnom and lf are given in the relevant ETA or in a CEN Standard.

6.3.4.2.2 Geometric effect of axial spacings, edge distances and member thicknesses

The geometrical effect of spacing as well as of further edge distances and the effect of thickness of the concrete member on the characteristic load is taken into account by the ratio , where: o

VcVc AA ,, /

oVcA , : see Figure 6.7

= 4.5 c12 (6.8b)

VcA , : area of the idealized concrete break-out, limited by the overlapping concrete cones of adjacent fasteners (s < 3 c1) as well as by edges parallel to the assumed loading direction (c2 < 1.5 c1) and by member thickness (h < 1.5 c1). Examples for calculation of Ac,V are given in Figure 6.8.

Figure 6.7 — Idealized concrete break-out body and area for a single anchor oVcA ,

6.3.4.2.3 Effect of the disturbance of the distribution of stresses in the concrete due to further edges

The factor Vs,ψ takes account of the disturbance of the distribution of stresses in the concrete due to further edges of the concrete member on the shear resistance. For fastenings with two edges parallel to the assumed direction of loading (e.g. in a narrow concrete member) the smaller edge distance shall be inserted in Equation (6.8c).

15.1

3.07.01

2, ≤

⋅⋅+=

cc

Vsψ (6.8c)

35


Figure 6.8 — Examples of actual areas of the idealized concrete break-out bodies for different fastener arrangements under shear loading

6.3.4.2.4 Effect of the thickness of the structural component

The factor Vh,ψ takes account of the fact that the shear resistance does not decrease proportionally to the

member thickness as assumed by the ratio . oVcVc AA ,, /

15.1 3/11

, ≥⎟⎠

⎞⎜⎝

⎛ ⋅=

hc

Vhψ (6.8d)

6.3.4.2.5 Effect of load direction

The factor V,αψ takes account of the angle αV between the load applied, VSd, and the direction perpendicular to the free edge of the concrete member (see Figure 6.9).

0.1, =Vαψ for 0° < αV < 55° area 1 (6.8e1)

36


VV

V ααψα sin5.0cos

1, ⋅+

= for 55°< αV > 90° area 2 (6.8e2)

0.2, =Vαψ for 90°< αV < 180° area 3 (6.8e3)

Figure 6.9 — Definition of angle αV

6.3.4.2.6 Effect of the eccentricity of the load

The factor Vec,ψ takes account of a group effect when different shear loads are acting on the individual fasteners of a group.

1)3/(21

11

, ≤⋅⋅+

=ceV

Vecψ (6.8f)

with: eV: eccentricity of the resulting shear load acting on the fasteners

6.3.4.2.7 Effect of the position of the fastening

The factor Vucr,ψ takes account of the effect of the position of the fastening in cracked or non-cracked concrete or of the type of reinforcement.

Vucr,ψ = 1.0 fastening in cracked concrete without edge reinforcement or stirrups

Vucr,ψ = 1.2 fastening in cracked concrete with straight edge reinforcement (> Ø12 mm)

Vucr,ψ = 1.4 fastening in cracked concrete with edge reinforcement, closely spaced stirrups (a < 100 mm) and s/c ≤ 2,

fastening in non-cracked concrete (proof according to Section 5)

A factor Vucr,ψ > 1 shall only be applied, if the embedment depth hef of the fastener is hef ≥ 2,5times the concrete cover of the edge reinforcement.

6.3.4.2.8 Special cases

For fastenings in a narrow, thin member with c2,max < 1.5 c1 (c2,max = greatest of the two edge distances parallel to the direction of loading) and h < 1.5c1 (see Figure 6.10) the calculation according to Equation (6.8) leads to results which are on the safe side. More precise results are achieved if in Equations (6.8a) to (6.8f) as well as in the determination of the areas and according to Figures 6.7 and 6.8 the edge distance co

VcA , VcA , 1 is

37


38 38

'1

'1replaced by c . The value of c being the greatest of the two values c'

1'1 max/1.5 and h/1.5, respectively but not

less than one-third of the maximum spacing between fasteners for fastener groups. replaced by c . The value of c being the greatest of the two values cmax/1.5 and h/1.5, respectively but not less than one-third of the maximum spacing between fasteners for fastener groups.

Figure 6.10 — Examples for fastenings in thin, narrow members where the value may be used '1c

6.3.5 Detailing of supplementary reinforcement

6.3.5.1 General

The resistance of fastenings may be increased by supplementary reinforcement in the shape of stirrups or loops (Figure 6.11) or by a surface reinforcement (Figure 6.12).

The reinforcement to take up shear loads acting on the fixture shall be located such that the anchorage length l1 lies within the potential concrete breakout cone.

The supplementary reinforcement detailed according to Figure 6.11 should comply with the following requirements:

a) The supplementary reinforcement should consist of ribbed reinforcing bars (fyk ≤ 500 N/mm2) with a diameter not larger than 16 mm. It should be detailed according to Figure 6.11. The bending diameter, db, should comply with EN1992-1-1.

b) The supplementary reinforcement should enclose and contact the shaft of the fastener and should be positioned as closely as possible to the fixture (see Figure 6.11).

c) The supplementary reinforcement should be anchored outside the assumed failure cone with an anchorage length lb,net according to EN1992-1-1.

If the shear force is taken up by a surface reinforcement according to Figure 6.11, the following requirements shall be met:

d) In general, for all fasteners of a group the same diameter of reinforcement should be provided. It should consist of ribbed bars with fyk ≤ 500 N/mm².

e) The supplementary reinforcement shall be located such that the anchorage length l1 of the reinforcing bars lies within the concrete breakout cones. Only bars with a distance ≤ 0,75c1 shall be assumed as active.

f) The minimum anchorage length in the concrete breakout body is min l1 = 10 ds, straight bars with or without welded transverse bars = 4 ds bars with a hook, bend or transverse reinforcement g) The reinforcement shall be anchored outside the assumed failure cone with an anchorage length lb,net

according to EN1992-1-1.


h) The reinforcement along the edge of the member shall be present. It shall be designed for the forces according to an assumed strut and tie model (see Figure 6.12b). As a simplification an angle of the compression struts of 45° may be assumed.

sdV

sdV

sdV

sdV

sl

sdT

se

minc

Figure 6.11 — Detailing of the supplementary reinforcement in form of loops

6.3.5.2 Required proofs

The following proofs are required (Table 6.4). For fastener groups the same supplementary reinforcement should be provided to all fasteners.

Table 6.4: Verifications for fastenings with supplementary reinforcement

Fastener groups

Single fastener most loaded fastener fastener group

Steel failure of fastener VSd ≤ VRd,s = VRk,s / γMs VhSd ≤ VRd,s = VRk,s / γMs

Pryout failure VSd ≤ VRd,cp = VRk,cp / γMc VgSd ≤ VRd,cp = VRk,cp / γMc

Steel failure of supplementary reinforcement

TSd ≤ VRd,s1 = VRk,s1 / γMs1 VhSd ≤ VRd,s1 = VRk,s1 / γMs1

Anchorage failure of supplementary reinforcement

TSd ≤ VRd,,a ThSd ≤ VRd,a

39


es

Vsd

Tsd

Csd

zd

a)

Σ=TsdVsd

Tsd,p

b)

Figure 6.12 — Surface reinforcement to take up shear forces a) detailing of reinforcement

b) simplified strut and tie model to design edge reinforcement

6.3.5.3 Steel failure of the fastener

For steel failure of fastener Section 6.3.2.1 applies.

6.3.5.4 Concrete pry-out failure

Section 6.3.3 applies with the following modifications: The value NRk,c calculated according toshould be inserted in Equation (6.7). Furthermore, the factor k given in the ETA or a CEN Stanmultiplied with 0.75.

6.3.5.5 Steel failure of reinforcement

The characteristic resistance of one fastener in case of steel failure of the reinforcement maaccording to Equation (6.9).

ykssRk fAnkV ⋅⋅⋅= 271,

with: k7 = efficiency factor = 0.5 supplementary reinforcement according to Figure 6.11 = 1,0 surface reinforcement according to Figure 6.12 n2 = number of bars of the supplementary reinforcement of one anchor As = cross section of one bar of the supplementary reinforcement fyk = nominal yield strength of the supplementary reinforcement

40

Figure to be improved

Section 6.2.2.4 dard should be

y be calculated

(6.9)


6.3.5.6 Anchorage failure of hanger reinforcement in the concrete breakout body

For applications according to Figure 6.11 no proof of the anchorage capacity is necessary.

For applications according to Figure 6.12 the design resistance VRd,,a of the reinforcement of one fastener in case of an anchorage failure is given by Equation (6.5) replacing NRd,,a by VRd,,a .

6.4 Combined tension and shear load

6.4.1 Fastenings without supplementary reinforcement

6.4.1.1 Steel failure decisive for tension and shear load

For combined tension and shear loads the following equations shall be satisfied (see Figure 6.13):

1≤Nβ (6.10a)

1≤Vβ (6.10b)

122 ≤+ VN ββ (6.10c)

where and RdSdN NN /=β RdSdV VV /=β

6.4.1.2 Other modes of failure decisive

For combined tension and shear loads either of the following Equations (6.11a) to (6.11c), (see Fig. 6.15) or Equ. (6.11d) shall be satisfied:

1≤Nβ (6.11a)

1≤Vβ (6.11b)

2,1≤+ VN ββ (6.11c)

15,15,1 ≤+ VN ββ (6.11d)

In Equations (6.11a) to (6.11d) the largest value of βN and βV for the different failure modes shall be taken (see 6.2.2.1 and 6.2.3.1).

Figure 6.13 — Interaction diagram for combined tension and shear loads

41


6.4.1.3 Fastenings with supplementary reinforcement

For fastenings with a supplementary reinforcement for tension and shear loads Section 6.2.4.1 applies. For fastenings with a supplementary reinforcement to take up tension or shear loads only, Equation (6.12) shall be used.

13/23/2 ≤+ VN ββ (6.12)

7 Fatigue

7.1 General

Part 1 'General' of this Technical Specification shall apply.

8 Seismic

8.1 General

Part 1 'General' of this Technical Specification shall apply.

42

cen/tc 250/sc 2/wg 2 n 0154

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