Eurocode 6 - Introduction

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Guidance on Eurocode 6The purpose of this series of guides is to introduce designers to the basic

approach adopted in Eurocode 6. This is the first guide in the series of three

and provides:

A brief outline of the scope of Eurocode 6.

An introduction to design, including fire resistance and movement.

Assessment of actions and combination of actions using Eurocode*.

How to specify mortar and masonry units. Glossary of Eurocode 6 terms.

The second guide in the series, Vertical resistance1, explains how to design

for vertical actions, whilst the third guide, Lateral resistance2, covers the

design of laterally loaded masonry panels. Further information on Eurocode 6

can be found at www.eurocode6.org.

Eurocode 6Eurocode 6 comprises the following parts:

Part 11, General rules for reinforced and unreinforced masonry structures3.

Part 12, Structural fire design4. Part 2, Design considerations, selection of materials and execution of masonry5.

Part 3, Simplified calculation methods for unreinforced masonry structures6.

Each part also has a National Annex (NA) which provides the Nationally

Determined Parameters (NDPs) to be used in the application of Eurocode 6 in

the UK. The UK NDPs have been used throughout this guide. In addition

PD 6697 contains useful guidance complementary to Eurocode 67.

This series concentrates on Eurocode 6, Part 11 but includes material from

Part 2 to explain the exposure and durability requirements. The scope and

content of Part 12 and Part 3 are also briefly explained.

Eurocode 6 is intended to be used with Eurocode*: Basis of structural design8,Eurocode 1:Actions on structures9and, where appropriate, the other Eurocodes

and relevant European Standards. The guide Introduction to Eurocodes10

provides more information on the Eurocode family.

Eurocode 6 has been developed to enable the designer to use the following

types of masonry unit: clay, calcium silicate, aggregate concrete, autoclaved

aerated concrete (aircrete), manufactured stone and natural stone. European

standards for these materials have been published by BSI and form part of an

array of standards relating to masonry produced under the auspices of the

European Committee for Standardisation (CEN), committee TC/125 (Masonry).

*BS EN 1990 is entitled Eurocode, but is often referred to as Eurocode 0.

How to design masonry structures using Eurocode 6

1. Introduction to Eurocode 6Eur Ing, Prof.J J Roberts BSc(Eng), PhD, CEng, FIStructE, FICE, FIMS, FCMI, MICT O Brooker BEng, CEng, MICE, MIStructE

IntroductionThis publication is part of a series of three

guides entitled How to design masonry structures

using Eurocode 6. The aim is to make the use of

Eurocode 6, Design of masonry structuresas easy

as possible by drawing together in one place key

information and commentary required for the

design of typical masonry elements.

The Concrete Centre (and, originally, The Modern

Masonry Alliance) recognised that effective

guidance was required to ensure that the UK

design profession was able to use Eurocode 6

quickly, effectively, efficiently and with confidence.

Therefore a steering group, with members from

across the masonry industry (see back cover for a

list of members), was established to oversee the

development and publication of the original guides.

This second revision addresses the publication of

PD6697 in 2010 and revised National Annex to

BS EN 1996-1-1 in 2013. It was overseen by a

reconstituted steering group from industry (see

back cover).

Revision 2


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Basis of designMasonry structures are required to be designed in accordance with the

general rules given in Eurocode, which requires that:

Ed Rd

where

Ed = design value of the effect of actions

Rd = design value of the resistance

The basic requirements of Section 2 of Eurocode are deemed to be

satisfied for masonry structures when the following are applied:

Limit state design in conjunction with the partial factor method

described in Eurocode.

Actions as given in Eurocode 1. (See Assessment of actions below.)

Combination rules as given in Eurocode.

The principles and application rules given in Eurocode 6.

Thus using the partial factor method, the design value for a material

property is obtained by dividing its characteristic value by the relevant

partial factor for materials as follows:

RkRd= gM

where

Rd= design value of resistance

Rk= characteristic value of the resistance

gM= partial factor for a material property

Partial factors for materialsThe partial factors for use with masonry are given in Table NA.1 of

the National Annex to Eurocode 6, Part 11 and shown here as Table

1. Two levels of attestation of conformity are recognized, Category I

and Category II and this will be declared by the manufacturer of the

masonry units. There are also two classes of execution control that are

recognized: 1 and 2.

Assessment of actionsThe Eurocodes use the term action to refer to a set of forces,

deformations or accelerations acting on the structure; this includes

horizontal and vertical loads. The guide How to design concrete

structures using Eurocode 2: Introduction to Eurocodes9gives guidance

on determining the design value of actions and should ideally be

consulted. However, a brief explanation on how to determine the

partial factors for masonry design to Eurocode 6 is given below.

There are a number of combinations of actions that are described

in Eurocode, but for masonry design (excluding retaining structures)

the ultimate limit state, STR (STR represents an internal failure or

excessive deformation of the structure or structural member) will

normally be used. For plain masonry, Eurocode 6 indicates that,

Scope of Part 11 of Eurocode 6Part 11 describes the principles and requirements for safety,

serviceability and durability of masonry structures. It is based on the

limit state concept used in conjunction with a partial factor method.

For the design of new structures, BS EN 199611 is intended to be

used together with the other relevant Eurocodes.

Scope of Part 12 of Eurocode 6This part deals with the design of masonry structures for the

accidental situation of fire exposure and identifies differences from,

or supplements to, normal temperature design. Only passive methods

of fire protection are considered and active methods are not covered.

It addresses the need to avoid premature collapse of the structure

and to limit the spread of fire.

Scope of Part 2 of Eurocode 6This part gives the basic rules for the selection and executionof masonry to enable it to comply with the design assumptions

of the other parts of Eurocode 6. It includes guidance on factors

affecting performance and durability, storage and use of materials,

site erection and protection, and the assessment of the appearance

of masonry.

Scope of Part 3 of Eurocode 6This part provides simplified calculation methods to facilitate the

design of a range of common wall types under certain conditions of

use. The methods are consistent with Part 11 but result in more

conservative designs, and other methods are available in the UK; see'Simplified calculation methods' on page 7. The simplified methods

are not applicable to design for accidental situations, which should be

designed for in accordance with CI 5.2 of Part 11.

Scope of PD 6697This Published Document contains non-contradictory complementary

information and additional guidance for use in the UK with Part 1-1

and Part 2 of Eurocode 6.

Supporting standardsThere are European Standards that support Eurocode 6, and

whilst they were developed within a common framework, it has

not proved possible to standardise all the test methods used for

the different materials. Words like brick and block have disappeared

from the European vocabulary and they are all referred to as masonry

units. Products should be specified by their performance requirements.

The Standards that support the use of masonry in Eurocode 6 are

published by BSI. Two key factors that changed from previous UK

practice are:

The six masonry unit standards introduced methods fordetermining the compressive strength of masonry units11.

The method of determining characteristic compressive and shear

strengths of masonry changed.



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Table 1Values of gMfor ultimate limit state

Material Class of executioncontrol gM

1a 2a

Masonry

When in a state of direct or flexural compression

Unreinforced masonry made with:

Units of category I 2.3

b 2.7

b

Units of category II 2.6

b 3.0

b

Reinforced masonry made with mortar M6 or M12:

Units of category I 2.0

b c

Units of category II 2.3b c

When in a state of flexural tension

Units of category I and II but inlaterally loaded wall panels whenremoval of the panel would not affectthe overall stability of the building

2.3

b

2.0

b

2.7

b

2.4

b

When in a state of shear

Unreinforced masonry made with:

Units of category I and II 2.5

b 2.5

b

Reinforced masonry made with mortar M6 or M12:

Units of category I and II 2.0

b c

Steel and other components

Anchorage of reinforcing steel 1.5

d c

Reinforcing steel and prestressing steel 1.15

d c

Ancillary components wall ties 3.0

b 3.0

b

Ancillary components straps 1.5e 1.5e

Lintels in accordance with EN 845-212 See NA toBS EN 8452f

See NA toBS EN 8452f

Key

a Class 1 of execution control should be assumed whenever the work is carried outfollowing the recommendations for workmanship in BS EN 19962, includingappropriate supervision and inspection, and in addition:

i the specification, supervision and control ensure that the construction iscompatible with the use of the appropriate partial safety factors given inBS EN 199611;

ii the mortar conforms to BS EN 998-2, if it is factory made mortar. If themortar is site mixed, preliminary compressive strength tests, in accordancewith BS EN 1015-2 and 1015-11, are carried on the mixture of sand, lime (ifany) and cement that is intended to be used (the proportions given in TableNA.2 may be used initially for the tests) in order to confirm that the strengthrequirements of the specification can be met; the proportions may need tobe changed to achieve the required strengths and the new proportions arethen to be used for the work on site. Regular compressive strength testingis carried out on samples from the site mortar to check that the requiredstrengths are being achieved.

Class 2 of execution control should be assumed whenever the work is carried outfollowing the recommendations for workmanship in BS EN 19962, includingappropriate supervision.

b When considering the effects of misuse or accident these values may be halved.

c Class 2 of execution control is not considered appropriate for reinforced masonryand should not be used. However, masonry wall panels reinforced with bed jointreinforcement used:

i to enhance the lateral strength of the masonry panel,

ii to limit or control shrinkage or expansion of the masonry,

can be considered to be unreinforced masonry for the purpose of class of executioncontrol and the unreinforced masonry direct or flexural compression gMvalues areappropriate for use.

d When considering the effects of misuse or accident these values should be taken as 1.0.

e For horizontal restraint straps, unless otherwise specified, the declared ultimateload capacity depends on there being a design compressive stress in the masonryof at least 0.4 N/mm2. When a lower stress due to design loads may be acting,

for example when autoclaved aerated concrete or lightweight aggregate concretemasonry is used, the manufacturers advice should be sought and a partial safetyfactor of 3 should be used.

f Yet to be published.

provided the ultimate limit state is satisfied, no checks for the

serviceability limit states are required. This assumes compliance with

the limiting dimensions and ratios specified in Eurocode 6.

There are three combinations that can be used for the STR limit

state Expression (6.10), which is always conservative, or the mostonerous of Expressions (6.10a) or (6.10b) (see Table 2). For laterally

loaded masonry walls, where self-weight is usually beneficial, it will

be sufficient to use Expression (6.10) only. For vertically loaded

walls there will be some benefit in using Expression (6.10b), which,

for members supporting one variable action (except storage loads)

is the most economical of the three expressions, provided that the

permanent actions are not greater than 4.5 times the variable actions.

In Table 2 c0is a factor that reduces the design value of a variable action

when it acts in combination with another variable action (i.e. when it is

an accompanying action). The value of c0can be obtained from Table 3.

The UK NA to Eurocode values can be applied to Expression (6.10), andthis is shown in Table 4, which also shows the factors to be used when

wind loads act in combination with imposed loads. Note that wind

loads and imposed loads are both considered to be variable actions.

Table 2Design values of actions, ULS (Table A1.2 (B) of Eurocode)

CombinationExpressionreference

Permanent actions Leadingvariableaction

Accompanyingvariable action

Unfavourable Favourable

Exp. (6.10) gG,j,supGk,j,sup gG,j,infGk,j,inf gQ,1Qk,1 gQ,ic0,iQk,i

Exp. (6.10a) gG,j,supGk,j,sup gG,j,infGk,j,inf gQ,1c0,1Qk,1 gQ,ic0,iQk,i

Exp. (6.10b) jgG,j,supGk,j,sup gG,j,infGk,j,inf gQ,1Qk,1 gQ,ic0,iQk,i

Notes

Gk = characteristic value of a permanent loadQk = characteristic value of the variable actiongG,sup= partial factor for permanent action upper design valuegG,inf = partial factor for permanent action lower design valuegQ = partial factor for variable actionsc0 = factor for combination value of a variable actionj = reduction factor/distribution coefficientWhere a variable action is favourable Qkshould be taken as 0.

Table 3Recommended combination values of variable actions (c0) buildings(from UK National Annex to Eurocode)

Action c0

Imposed loads in buildings (see BS EN 199111)

Category A: domestic, residential areas 0.7

Category B: office areas 0.7

Category C: congregation areas 0.7

Category D: shopping areas 0.7

Category E: storage areas 1.0

Category F: traffic area, vehicle weight < 30 kN 0.7

Category G: traffic area, 30 kN < vehicle weight < 160 kN 0.7

Category H: roofs a 0.7

Snow loads on buildings (see BS EN 19913)

For sites located at altitude H > 1000 m above sea level 0.7

For sites located at altitude H < 1000 m above sea level 0.5

Wind loads on buildings (see BS EN 199115) 0.6

Key

aSee also 199111: Cl 3.3.2

1. Introduction to Eurocode 6


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ImperfectionsEurocode 6 also recognizes that imperfections should be taken into

account in design and requires that, at the ultimate limit state, the

horizontal forces to be resisted at any level should be the sum of 1and 2 below.

1. The horizontal load due to the vertical load being applied to a

structure with the following notional inclination angle vto the

vertical:

1 v= radians 100 Rhtot

where

htot= the total height of the structure in metres.

Each vertical action therefore produces a horizontal action to

which the same load factor and combination factor as the vertical

load apply.2. The wind load derived from Eurocode 1, Parts 14 multiplied by

its partial factor and distributed across the elements resisting the

load in proportion to their stiffness.

MortarThe way in which mortar is specified is shown in Table 5. The primary

method of designation for mortar is the strength grade. Thus an M12

mortar should have a minimum compressive strength of 12 N/mm2

at 28 days. Eurocode 6 recognises three types of masonry mortar:

general purpose, thin layer and lightweight mortar, and they may all

be either designed or prescribed (see Glossary).

The use of mortars should be in accordance with the recommendations

given in Eurocode 6, Part 2. For site made mortars, the mixing of the

mortar should be in accordance with Part 2 (PD 66977provides more

detailed information). For factory made, semi-finished factory made

and pre-batched masonry mortars, BS EN 998213applies.

Table 4Design values of actions derived for UK design, ultimate limit state

Combinationexpressionreference

Permanent actions Leadingvariable action(unfavourable)

Accompanyingvariable actions(unfavourable)Unfavourable Favourable

Combination of permanent actions and one variable action

Exp. (6.10) 1.35 Gka 1.0 Gk

a 1.5 Qkb

Exp. (6.10a) 1.35 Gka 1.0 Gk

a 1.5 c0-1bQk

Exp. (6.10b) 0.925 x1.35Gka 1.0 Gk

a 1.5 Qk

Combination of permanent actions, wind load (Qk,W) and imposed load (Qk,I)

Exp. (6.10)Case 1

1.35 Gka 1.0 Gk

a 1.5 Qk,W 1.05cQk,I

Exp. (6.10)Case 2

1.35 Gka 1.0 Gk

a 1.5 Qk,I 0.75dQk,W

Key

a Where the variation in permanent action is not considered significant Gk,j,supand Gk,j,inf

may be taken as Gkb Where a variable action is favourable Qkshould be taken as 0

cThe value of c0has been taken as 0.7, for storage loads c0= 1.0 and a factor of 1.5must be used

d The value of c0has been taken as 0.5

For designed mortars, the compressive strength of the mortar provides

the control of the hardened mortar quality, whereas prescribed

mortars use set proportions. When samples are taken from a designed

mortar in accordance with BS EN 1015214, and tested in accordance

with BS EN 10151115, the compressive strength of the mortar

should not be less than the declared compressive strength.

Durability of materialsEurocode 6, Part 2 gives the basic rules for selection of mortar

and masonry units for durability. Exposure conditions are defined in

CI 2.1.2(3) of Part 2, with further guidance given in Annexes A, B

and C. The UK NA to Part 2 advises that Annexes B and C should not

be used because the information is not as extensive as that given in

PD 6697; this advice is included in Table 6.

Structural fire designEurocode 6, Part 12 provides information on the passive fire

resistance of masonry walls so that the designer can ensure that the

loadbearing performance is maintained for the necessary period of

time and that the fire is appropriately contained.

Designers will find that the tabulated data covers most situations but there

is also the provision for testing and calculations. (Calculation methods

are excluded by the UK NA to Part 12.) The tables cover loadbearing

and non-loadbearing walls, single leaf, cavity and separating walls.

Table 5Acceptable assumed equivalent mixes for prescribed masonry mortarsfor use with Class 2 of Execution control

Com-pressivestrengthclassa

Prescribed mortars (traditional proportionof materials by volume) (see Note)

Mortardesign-ation

Suitablefor use inenviron-mentalcondition

Cementb:lime: sandwith orwithoutair entrain-ment

Cementb:sand withor withoutair entrain-ment

Masonrycementc :sand

Masonrycementd:sand

M12 1:0 to : 3 1:3 Notsuitable

Notsuitable

(i) Severe(S)

M6 1

:

: 4 to

4

1

:

3 to 4 1

:

2 to

3

1

:

3 (ii) Severe(S)

M4 1

:

1: 5 to 6 1

:

5 to 6 1

:

4 to 5 1

:

3 to 4 (iii) Moderate(M)

M2 1:2: 8 to 9 1:7 to 8 1:5 to6

1:4 (iv) Passive(P)

Key

a The number following the M is the compressive strength for the class at 28 daysin N/mm2that may be assumed for the proportions given in columns 2 to 4; sitecompressive strength testing is not required for these traditional mixes. Checking ofprescribed mortars should only be done by testing the proportions of the constituents.

b Cement or combinations of cement (which include CEM I and many CEM IIs) in accordancewith NA.2.3.2, except masonry cements

c Masonry cement in accordance with NA.2.3.2, (inorganic filler other than lime)

d Masonry cement in accordance with NA.2.3.2 (lime)

Notes

When the sand portion is given as, for example, 5 to 6, the lower figure should be used

with sands containing a higher proportion of fines whilst the higher figure should be usedwith sands containing a lower proportion of fines.

For Class 2 of execution control site compressive strength testing is not required for thesetraditional mixes and checking of prescribed mortars should only be done by testing theproportions of the constituents.



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Table 6Durability of masonry in finished condition

Masonry conditionor situationa

Quality of masonry units and appropriate mortar designations

Clay unitsb Calcium silicate units Aggregate concrete bricks Aggregate concreteand autoclaved aerated

concrete blocksA Work below or near external ground level

A1 Low risk of saturation Without freezing: LD F0 and S0 or HD: F0,F1 or F2 and S0, S1 or S2 in M12, M6 or M4

With freezing: HD F1 or F2 and S0, S1 orS2 in M12, M6 or M4 unless a manufactureradvises against the use of HD-F1

Without or with freezing:

Compressive strength class 20or above in M4 or M2


Compressive strength16.5 N/mm2or above in M4


As Notes 4A, 4B, 4C or 4Dc.

All in M4 or M2d

A2 High risk of saturationwithout freezinge

HD F1 or F2, and S1 and S2 in M12 or M6 Compressive strength class 20or above in M6 or M4

Compressive strength 16.5 N/mm2or above in M6 or M4

As for A1 in M6 or M4

A3 High risk of saturationwith freezinge

HD F2 and S1 or S2 in M12 or M6 Compressive strength class 20or above in M6 or M4

Compressive strength 22 N/mm2or above in M6 or M4

As for A1 in M6

B Masonry d.p.c.s

B1 In buildings D.P.C units, max. water absorption 4.5% in M12fg Not suitable Not suitable Not suitable

B2 In external works D.P.C. units, max. water absorption 7 % inM12fg

Not suitable Not suitable Not suitable

C Unrendered external walls (other than chimneys, cappings, copings, parapets and sills)hC1 Low risk of saturation HD F1 or F2 and S1 or S2 in M12, M6 or

M4Compressive strength class 20or above in M4 or M2


Any in M4 or M2

C2 High risk of saturation HD F2 and S1 or S2 in M12 or M6 Compressive strength class 20or above in M4

Compressive strength18 N/mm2or above in M4

Any in M4

D Rendered external walls (other than chimneys, cappings, copings, parapets, sills) ij

Rendered external walls HD F1 or F2 and S1 or S2 in M12, M6 or M4 Compressive strength class 20or above in M4 or M2


Any in M4 or M2

E Internal walls and inner leaves of cavity walls above d.p.c level

Internal walls and inner leavesof cavity walls

LD F0 and S0 or HD: F0, F1 or F2 and S0, S1or S2 in M12, M6, M4 or M2

Compressive strength class 20or above in M4 or M2

Compressive strength 7.3 N/mm2or above in M4 or iv

Any in M4 or M2

F Unrendered parapets (other than cappings and copings)klm

F1 Low risk of saturation e.g.low parapets on somesingle storey buildings

HD F1 or F2 and S1 or S2 in M12, M6 orM4

Compressive strength class 20or above in M4


As Notes 4A, 4B, 4C or 4Dcin M4.

R2 High risk of saturation e.g.where a capping only is providedfor the masonry

HD F2 and S1 or S2 in M12 or M6 Compressive strength class 20or above in M4


As for F1 in M6

G Rendered parapets (other than cappings and copings)jo

Rendered parapets HD F1 or F2 and S2 in M12, M6 or M4 orHD F1 or F2 and S1 in M12 or M6



Any in M4

H Chimneysn

H1 Unrendered with low riskof saturation

HD F1 or F2 and S1 or S2 in M12, M6 orM4



Any in M4

H2 Unrendered with high riskof saturation

HD F2 and S1 or S2 in M12 or M6 Compressive strength class 20or above in M4



H3 Rendered HD F1 or F2 and S2 in M12, M6 or M4 orHD F1 or F2 and S1 in M12 or M6



Any in M4

I Cappings, copings and sillskl

Cappings, copings and sills HD F2 and S1 or S2 in M12 Compressive strength class 30or above in M6


As Notes 4A, 4B or 4C in M6.

J Freestanding boundary and screen walls (other than cappings and copings)J1 With coping HD F1 or F2 and S1 in M12 or M6 or HD

F1 or F2 and S2 in M12, M6 or M4Compressive strength class 20or above in M4


Any in M4

J2 With capping HD F2 and S1 or S2 in M12 or M6 Compressive strength class 20or above in M4


As Notes 5A, 5B, 5C or 5Din M6.

K Earth-retaining walls (other than cappings and copings)p

K1 Waterproofing retainingface and coping

HD F1 or F2 and S1 or S2 in M12 or M6 Compressive strength class 20 orabove in M6 or M4



K2 With coping or cappingbut no waterproofing onretaining face

HD F2 and S1 or S2 in M12 Compressive strength class 30 orabove in M6

Compressive strength33 N/mm2or above in M12or M6

As for K1 but in M12 or M6q

L Drainage and sewage, e.g. inspection chambers and manholes

L1 Surface water Engineering bricks or F1 or F2 and S1 or S2in M12

Compressive strength class 20 orabove in M6 or M4


As Notes 5A, 5B or 5C in M4.

L2 Foul drainage (continuouscontact with masonry)

Engineering bricks or F1 or F2 and S1 or S2in M12

Compressive strength class 50 orabove in M6r

Compressive strength 48 N/mm2or above with cement content

350 kg/m3in M12 or M6

Not suitable

L3 Foul drainage (occasionalcontact with masonry)

Engineering bricks or F1 or F2 and S1 or S2in M12

Compressive strength class 20 orabove in M6 or M4r

Compressive strength 48 N/mm2or above with cement content 350 kg/m3in M12 or M6

Not suitable


Table continues on page 6


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Reinforced andprestressed masonryEurocode 6, Part 11 contains information relating to the design of

reinforced masonry, but provides no application rules on the design of

prestressed masonry. Annex J of Part 1-1 provides additional guidance

for reinforced masonry when subjected to shear. PD 6697 extends the

information provided in Part 1-1 for both reinforced and prestressed

masonry as well giving guidance on the use of bed joint reinforcement

to enhance resistance to lateral loads.

Masonry movementThe potential for movement in completed masonry needs to be

allowed for in design, and Eurocode 6, Part 2 makes recommendations

for controlling differential movements; for example, the use of

movement tolerant ties between the leaves of a cavity wall.

Movement joints need to be provided to deal with the effects of

moisture, temperature and movement caused by other agents. The

position of movement joints needs to be considered with care to

ensure that the structural integrity of the wall is maintained. Factors

affecting the location of joints include:

The type and group of masonry unit.

The geometry of the structure.

The degree of restraint.

The effect of loading, thermal and climatic conditions.

Requirements for fire, sound and thermal performance.

The presence of reinforcement.

Movement joints that pass through the full thickness of the wall should

be provided. The maximum horizontal distance, lm, between vertical

movement joints for use for all walls in the UK (in the absence of other

guidance from the manufacturer) is shown in Table 7.

Execution of masonryEurocode 6, Part 2 gives guidance on the execution of masonry including:

Permissible deviations.

Jointing and pointing.

Storage, preparation and use of materials on site.

Masonry protection during execution.

Further detail on the first two points is given in the following paragraphs.

Permissible deviationsThe permissible deviations of the constructed masonry from the

position in which it is intended to be built should form part of the

design specification. The permissible deviations should not normally be

greater than the values shown in Table 8 for structural imperfections.

Mortar pointingMost masonry is constructed in such a way that the bedding mortar also

forms the tooled surface of the finished mortar joint. If it is necessary to

point the mortar joint the unhardened mortar should be raked out to a

depth not less than 15 mm, but no more than 15% of the wall thickness.


Table 6 Continued from page 5

Notes

1 Table 6 is a reduced version of the information provided in PD 6697which should be consulted when detailed guidance is required.

2 For designations (i), (ii), (iii) and (iv) see Table 5.3 LD - clay masonry unit with a low gross dry density for use in protected masonry.

HD - clay masonry unit for unprotected masonry as well as clay masonryunit with a high gross dry density for use in protected masonry.

4 Categories used for clay masonry for freeze/thaware as follows:

F0 Passive exposure F1 Moderate exposure F2 Severe exposure.

Categories used for clay masonry for active saltcontent are as follows:

S0 No requirement for active salt content S1 Limited active salt content (see BS EN 7711, Cl. 5.3.9) S2 Limited active salt content (see BS EN 7711, Cl. 5.3.9).

5 Concrete block options: A Of net density 1500 kg/m3

B Made with dense aggregate conforming to BS EN 12620

C Having a compressive strength of 7.3 N/mm2D Most types of autoclaved aerated block (consult manufacturer).

Key

a Refer to PD 6697 for guidance on sulfatebearing ground.

b Consult masonry unit manufacturer for usebelow or near ground level.

c Consult masonry unit manufacturer.

d M2 mortar does not meet the minimumrequirements of Approved Document Aand if used refer to PD 6697 for limitationsand guidance.

e Masonry is very vulnerable between 150mmabove and 150mm below finishedground level. Refer to PD 6697 and consultmanufacturer as required.

f Masonry dpcs do not resist waterpercolating downward.

g Dpcs of clay units are not normally suitablefor use with other types of unit.

h Protect with good roof overhang anddetailing.

i Rendered walls are suitable for mostwind driven rain conditions.

j For rendered walls follow guidance inPD 6697.

k AAC blocks are not suitable for cappings,copings and cills.

l Bed dpcs for cappings, copings and cillsin same mortar as the masonry units.

mParapets are likely to be severely exposed -coping and dpc should be provided.

n For chimneys follow guidance in PD 6697.

o Single leaf walls should be rendered onlyon one face.

p Masonry in retaining walls particularlyprone to frost and sulfate attack.Check with unit manufacturer.

q Some types of aggregate concrete unitsare not suitable for capping and copings.

r Some types of calcium silicate units arenot suitable for foul drainage.


7/24

7


References

1 ROBERTS, J J & BROOKER, O How to design masonry structures using Eurocode 6: Vertical resistance (TCC/03/36). The Concrete Centre, 2013. 2 ROBERTS, J J & BROOKER, O How to design masonry structures using Eurocode 6: Lateral resistance (TCC/03/37). The Concrete Centre, 2013.

3 BRITISH STANDARDS INSTITUTION. BS EN 199611: Eurocode 6 Design of masonry structures. General rules for reinforced and unreinforced masonry

structures. BSI, 2005. Including NA to BS EN 1996-1-1:2005+A1:2012.

4 BRITISH STANDARDS INSTITUTION. BS EN 199612: Eurocode 6 Design of masonry structures. General rules. Structural fire design . BSI, 2005.

Including NA to BS EN 1996-1-2:2005:2007.

5 BRITISH STANDARDS INSTITUTION. BS EN 19962: Eurocode 6 Design of masonry structures. Design considerations, selection of materials and

execution of masonry. BSI, 2006. Including NA to BS EN 1996-2:2006:2007.

6 BRITISH STANDARDS INSTITUTION. BS EN 19963: Eurocode 6 Design of masonry structures. Simplified calculation methods for unreinforced masonry

structures. BSI, 2006. Including NA to BS EN 1996-3:2006:2007.

7 BRITISH STANDARDS INSTITUTION. PD 6697. Recommendations for the design of masonry structures to BS EN 1996-1-1 and BS EN 1996-2 . BSI, 2010.

8 BRITISH STANDARDS INSTITUTION. BS EN 1990: Eurocode Basis of structural design. BSI, 2002. Including NA to BS EN 1990:2002+A1:2005:2004.

9 BRITISH STANDARDS INSTITUTION. BS EN 1991: Eurocode 1 Actions on structures. BSI (10 parts). Including their NAs.

10 NARAYAN, R S & BROOKER, O. How to design concrete structures using Eurocode 2: Introduction to Eurocodes(TCC/03/16). The Concrete Centre, 2005.

11 BRITISH STANDARDS INSTITUTION. BS EN 771: Specification for masonry units. BSI, 2011 (6 Parts).

12 BRITISH STANDARDS INSTITUTION. BS EN 8452: Specification for ancillary components for masonry Lintels . BSI, 2013.

13 BRITISH STANDARDS INSTITUTION. BS EN 9982: Specification for mortar for masonry: Masonry mortar. BSI, 2013.

14 BRITISH STANDARDS INSTITUTION. BS EN 10152: Methods of test for mortar for masonry: Bulk sampling of mortars and preparation of test mortars. BSI, 1999.

15 BRITISH STANDARDS INSTITUTION. BS EN 101511: Methods of test for mortar for masonry: Determination of flexural and compressive strength of

hardened mortar. BSI, 1999.

16 DEPARTMENT FOR COMMUNITIES AND LOCAL GOVERNMENT, Building regulations (England and Wales) Approved Document A (2004). DCLG, revised 2006.

17 SCOTTISH BUILDING STANDARDS AGENCY. Scottish building standards technical handbooks: domestic for compliance with 'Building Scotland

regulations 2004'. SBSA, 2007.

18 THE STATIONERY OFFICE. The Building Regulations (Northern Ireland) 1994 Technical Booklet D: Structure. TSO, 2000.

19 BRITISH STANDARDS INSTITUTION. BS 81032: Structural design of low-rise buildings Code of practice for masonry walls for housing . BSI, 2005.

20 BRITISH STANDARDS INSTITUTION. BS 772: Methods of test for masonry units. BSI (20 parts).

Simplified calculationmethods

Eurocode 6, Part 3 contains simplified calculation methods forunreinforced masonry structures. These methods are based on the

principles contained in Part 1 and should not be confused with simple

rules developed on the basis of experience. In general, these methods

are more conservative than design based on Part 1 and have not,

historically, been used in the UK, unlike some European countries. In the

UK guidance on the Building Regulations1618and BS 8103219provide

a very effective and economic set of simple rules for low rise masonry

and it is anticipated that these will continue to be the primary method

of demonstrating compliance for many small buildings.

Table 8Permissible deviations for structural design purposes

Position Maximum deviation

Verticality

In any one storey 20 mm

In total height of building of threestoreys or more

50 mm

Vertical alignment 20 mm

Straightnessa

In any one metre 10 mm

In 10 metres 50 mm

Thickness

Of wall leafb 5 mm or 5 % of the leafthickness, whichever is the greater

Of overall cavity wall 10 mm

Key

a Deviation from straightness is measured from a straight reference line between anytwo points.

b Excluding leaves of single masonry unit width or length, where the dimensionaltolerances of the masonry units govern the leaf thickness.

Table 7Maximum horizontal distance between vertical movement joints inwalls (in the absence of other guidance from the manufacturer)

Type of masonry lm(m)

Clay masonry unreinforced 15a

Calcium silicate masonry 9 b

Aggregate concrete and manufactured stone masonry 9b

Autoclaved aerated concrete masonry 9 b

Natural stone masonry 20 c

Key

a The value for clay masonry walls containing bed joint reinforcement may be greaterthan 15 m subject to expert advice.

b This value applies when the ratio, length to height of panel, is 3 to 1 or less. It shouldbe reduced for long horizontal panels of masonry which lie outside this ratio.

c When using this figure, movement joints should be located at not more than 8 mfrom the corner.


8/24

All advice or information from MPA The Concrete Centre (TCC) et al is intended only for use in the UK by those who will evaluate thesignificance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) forany loss resulting from such advice or information is accepted by TCC or their subcontractors, suppliers or advisors. Readers should note that

the publications from TCC et al are subject to revision from time to time and should therefore ensure that they are in possession of thelatest version.

Ref: TCC/03/35. ISBN 978-1-904818 -56-4First published November 2007(in partnership with the Modern Masonry Alliance)revised January 2009 and June 2013Price Group M MPA The ConcreteCentre

Glossary of Eurocode 6 terminology

Term Definition

Adhesion The effect of mortar developing a tensile or shear resistance at the contact surface of masonry units.

Category I masonry unit Units with a declared compressive strength with a probability of failure to reach it not exceeding 5%.This may be determined via the mean or characteristic value.

Category II masonry unit Units not intended to comply with the level of confidence of Category 1 units.

Confined masonry Masonry provided with reinforced concrete or reinforced masonry confining elements in the vertical andhorizontal direction. (Not usually used in the UK.)

Designed masonry mortar A mortar whose composition and manufacturing method is chosen in order to achieve specified properties(performance concept).

General purpose masonry mortar Masonry mortar without special characteristics.

Griphole A formed void in a masonry unit to enable it to be more readily grasped and lifted with one or both hands orby machine.

Groups 1, 1s, 2, 3 and 4 Group designations for masonry units, according to the percentage, size and orientation of holes in the unitsmasonry units when laid. Note: The group designation will normally be declared by the manufacturer. Historically only Groups

1, 1sand 2 units have been used in the UK. Group 1s is referred to in BS EN 199612.

Hole A formed void which may or may not pass completely through a masonry unit.

Lightweight masonry mortar Designed masonry mortar with a dry hardened density below a prescribed figure.

Normalized compressive The compressive strength of masonry units converted to the air dried compressive strength of an equivalentstrength of masonry units 100 mm wide x 100 mm high masonry unit (see BS EN 772-120).

Orthogonal ratio, m The ratio of the flexural strength of masonry when failure is parallel to the bed joints to that when failure isperpendicular to the bed joints.

Prescribed masonry mortar Mortar made in predetermined proportions, the properties of which are assumed from the stated proportionsof the constituents (recipe concept).

Shell The peripheral material between a hole and the face of a masonry unit.

Shell bedded wall A wall in which the masonry units are bedded on two or more strips of mortar, two of which are at theoutside edge of the bed face of the units.

Thin layer masonry mortar Designed masonry mortar with a maximum aggregate size less than or equal to a prescribed figure.

Web The solid material between the holes in a masonry unit.


For more information on Eurocode 6 and other questionsrelating to the design, use and performance of concrete units,visit www.eurocode6.org

Published by The Concrete Centre

Gillingham House, 38-44 Gillingham Street, London, SW1V 1HU

Tel: +44 (0)207 963 8000 | www.concretecentre.com

Members of the steering groupAli Arasteh, Brick Development Association; Owen Brooker, The

Concrete Centre; Ken Fisher, International Masonry Society; Cliff Fudge,

Aircrete Products Association; Charles Goodchild, The Concrete Centre;

Gerry Pettit, Concrete Block Association; John Roberts, Consultant.

Members of the steering group for 2nd revisionCliff Fudge, Aircrete Products Association; Charles Goodchild, The

Concrete Centre; Simon Hay, Brick Development Association; Andy

Littler, Concrete Block Association; John Roberts, Consultant; Guy

Thompson, The Concrete Centre.

AcknowledgementsThis publication was jointly sponsored by the following organisations:

Aircrete Products Association- www.aircrete.co.uk

Brick Development Association- www.brick.org.uk

Concrete Block Association- www.cba-blocks.org.uk

MPA - Mortar Industry Association- www.mortar.org.uk

MPA - The Concrete Centre- www.concretecentre.com


9/24

Guidance for vertical resistanceThis guide is the second in a series of three giving guidance on the design of

masonry structures to Eurocode 61. The first guide, Introduction to Eurocode 62

gives an introduction to design and assessment of actions using Eurocode 6 and

also covers the specification and execution (workmanship) of masonry. This guide

explains how to design for vertical actions and determine vertical resistance. The

third guide in the series3 covers the design of laterally loaded masonry panels.

Throughout this guide the Nationally Determined Parameters (NDPs) from the UKNational Annexes (NAs) have been used. These enable Eurocode 6 to be applied in

the UK.

Design procedureThis guide explains how to determine the design resistance for a vertically loaded

wall. The first guide in the series, Introduction to Eurocode 6, should be referred to

so that the design load can be determined. In essence, when using the Eurocodes

the designer should check that the resistance is greater than or equal to the

effect of the actions. A flow chart for the design of masonry walls to resist vertical

actions is shown as Figure 1.

Compressive strengthEurocode 6 introduces some new concepts when dealing with the design of

masonry for vertical loads. The first of these relates to the way the compressive

strength of the masonry units is expressed. For design purposes the normalized

compressive strength,fb, of the masonry units is used. This is the compressive

strength of the units converted to the air-dried compressive strength of an

equivalent 100 mm wide by 100 mm high masonry unit. The detail is contained

in Part 1 of BS EN 772, Methods of test for masonry units4

. The advantage to thedesigner is that the normalized strength is independent of the size and shape of

the units used in the final construction.

Grouping of masonry unitsThe second change relates to the way in which masonry units are classified. This is

dealt with by grouping masonry into one of four groups as shown in Table 3.1 of

Eurocode 6. The group designation will normally be declared by the manufacturer.

The designation depends upon the volume and direction of holes in the unit and

the thickness of webs and shells. Historically only Group 1 and Group 2 units have

been used in the UK, so only values for these groups are given in the UK NAs.


2. Vertical resistanceEur Ing, Prof.J J Roberts BSc(Eng), PhD, CEng, FIStructE, FICE, FIMS, FCMI, MICT O Brooker BEng, CEng, MICE, MIStructE

IntroductionThis publication is part of a series of three

guides entitled How to design masonry structures

using Eurocode 6. The aim is to make the use of

Eurocode 6, Design of masonry structuresas easy

as possible by drawing together in one place key
















back cover).

Revision 2


10/24


2

For blocks laid flat, Table 8 of the National Annex to Eurocode 6,

Part 11 contains a specific value for Kto be used in Equation (3.1)

of Eurocode 6, Part 11.

The following limitations are placed on Equation (3.1):

The masonry is detailed and constructed in accordance with the

requirements of BS EN 199611, section 8.

fbis taken to be not greater than 110 N/mm2when units are laid

in general purpose mortar and 50 N/mm2when laid in thin layer

mortar (fbis determined in the normal direction of loading).

fmis taken to be not greater than fbnor greater than 12 N/mm2

when units are laid in general purpose mortar or 10 N/mm2when

units are laid in lightweight mortar.

The coefficient of variation of the strength of the masonry unit is

not more than 25%.

For masonry made with general purpose mortar, adjustments are

made to the value of Kas shown in Figure 2.

In addition the following points should be noted:

For masonry made of general purpose mortar where Group 2

and Group 3 aggregate concrete units are used with the vertical

cavities filled completely with concrete, the value offbshould

be obtained by considering the units to be Group 1 having a

compressive strength corresponding to the compressive strength of

the units or of the concrete infill, whichever is the lesser.

The characteristiccompressive strength of

masonryThe characteristic compressive strength of masonry (other than

shell bedded masonry) is determined from the results of tests in

accordance with BS EN 105215. The tests are carried out on small

wallette specimens rather than the storey-height panels used in the past.

The designer has the option of either testing the units intended to be

used in a project or using the values determined from a database. Values

from a large database are provided in the UK NA to Eurocode 6, Part 11

in the form of the constants to be used in the following equation:

fk= Kfba fm

b [Equation (3.1) of Eurocode 6, Part 11]

where

fk = characteristic compressive strength of the masonry, in N/mm2

K = constant see Table 1 and Figure 2

a, b= constants see Table 2

fb = normalized mean compressive strength of the units, in the

direction of the applied action effect, in N/mm2

fm = compressive strength of the mortar, in N/mm2

Figure 1Flow chart for the design of masonry walls to resist vertical actions

.

Obtain gMfrom table 1 of

Introduction to Eurocode 6

Determine requirementsfor mortar strength anddurability. See tables 5& 6 of Introduction to

Eurocode 6

Determine effective height, hef,of the wall (see page 4)

Check slenderness ratio hef/tef 27

Check area 0.04 m2

Determine eccentricity (see page 5)

Determine capacity reduction factors,Fmand Fi from (see page 6)

Determine normalizedcompressive strength, fb.

Characteristic vertical actions

Check EdNRd

Check complete

Calculate design resistance(per unit length) from least

favourable of:NRd= Fmtfk/ gM

andNRd= Fitfk/ gM

Where cross-sectional area,A< 0.1 m2, factor fkby (0.7 + 3A)

Determine design value ofvertical actions (per unit

length), Ed, using Expression(6.10), (6.10a) or (6.10b) of

Eurocode (see Introduction toEurocode 6)

Masonry unit properties Type and group Dimensions Strength

Determine characteristic compressive strength of masonry,fk, from Equation (3.1) of Eurocode 6 and Tables 1 & 2

Determine effective thickness,tef,of the wall (see page 4)



11/24

2. Vertical resistance

3

For collar jointed aggregate concrete masonry made with general

purpose mortar, with or without the collar filled with mortar, the unit

shape factor correction to obtain the normalized strength should use the

width of the wall as the unit width and the height of the masonry units.

Where action effects are parallel to the direction of the bed joints, the

characteristic compressive strength may be determined fromEquation (3.1) withfbderived from BS EN 7721, where the direction

of application of the load to the test specimens is in the same

direction as the direction of the action effect in the masonry, but with

the shape factor, d, as given in BS EN 7721 taken to be no greater

than 1.0. For Group 2 and 3 units, Kshould then be multiplied by 0.5.

Table 1Values of Kto be used with equation (3.1)

Masonryunit

Generalpurposemortar

Thin layermortar(bed joint 0.5 mm and3 mm)

Lightweight mortarof density (kg/m3)

600 rd800

800 < rd1300

ClayGroup 1 0.50 0.75 0.30 0.40

Group 2 0.40 0.70 0.25 0.30

Group 3 and 4 a a a a

Calcium silicate

Group 1 0.50 0.80 b b

Group 2 0.40 0.70 b b

Aggregate concrete

Group 1 0.75 0.90 0.45 0.45

Group 1c(units laid flat)

0.50d 0.70d 0.40d 0.40d

Group 2 0.70 0.76 0.45 0.45

Group 3 and 4 a

a

a

a

Autoclaved aerated concrete

Group 1 0.75 0.90 0.45 0.45

Manufactured stone

Group 1 0.75 0.90 b b

Dimensioned natural stone

Group 1 0.45 b b b

Key

a Group 3 and 4 units have not traditionally been used in the UK, so no values are available.

b These masonry unit and mortar combinations have not traditionally been used inthe UK, so no values are available.

c If Group 1 aggregate concrete units contain formed vertical voids in the normal direction,multiply Kby (100 n) /100, where nis the percentage of voids, maximum 25%.

d When aggregate concrete masonry units are to be used laid flat the normalised strength

of the unit should be calculated using the width and height of the unit in the uprightposition along with the compressive strength of the unit tested in the upright position.

Note

Where a mortar joint is parallel to the face of the wall Kshould be modified (see Figure 2)

Table 2Values to be used in Equation (3.1)

Type of mortar Values to be used

General purpose mortar a= 0.7 and b= 0.3

Lightweight mortar a= 0.7 and b= 0.3

Thin layer mortar in bed joints of thickness 0.5to 3 mm (using clay units of Group 1, calciumsilicate units, aggregate concrete units and

autoclaved aerated concrete units)

a= 0.85 and b= 0

Thin layer mortar in bed joints of thickness 0.5 to3 mm (using clay units of Group 2)

a= 0.7and b= 0

When the perpendicular joints are unfilled, Equation (3.1) may be

used, with consideration of any horizontal actions that might be

applied to, or be transmitted by, the masonry. (See also CI. 3.6.2(4)

of BS EN 199611.)

The characteristiccompressive strength ofshell bedded masonryShell bedding provides two strips of mortar rather than a full mortar bed.

It serves to improve rain penetration resistance but reduces the strength

of the masonry. A typical shell bedded unit is shown in Figure 3.

For Group 1 and Group 4 units the procedure above may be used to

obtain the characteristic compressive strength of the masonry.

Figure 2Modifications to Kfor units laid with general purpose mortar

Plan sections of bonded masonry

a) Kfrom Table 1

b) Kfrom Table 1

c) Kfrom Table 1 multiplied by 0.8

d) Kfrom Table 1 mult iplied by 0.8

Masonrythickness

Masonrythickness

Masonry

thickness

Masonrythickness

Figure 3Shell bedding


12/24


4

provided that:

The width of each strip of mortar is at least 30 mm.

The thickness of the masonry wall is equal to the width or length

of the masonry units so that there is no longitudinal mortar joint

through all or part of the length of the wall. The ratio g/tis not less than 0.4

where

g= total width of the mortar strips

t= the thickness of the wall.

Kis taken as above when g/t= 1.0 or half this value when g/t= 0.4.

Linear interpolation may be used for intermediate values.

Groups 2 and 3 may be designed as non-shell bedded masonry

provided that the normalized mean compressive strength of the units

used in Equation (3.1) is obtained from tests carried out in accordance

with BS EN 77214for shell bedded units.

Effective heightThe effective height of a masonry wall is obtained by applying a factor

to the clear height of the wall such that:

hef= rnh

where

hef = effective height of the wall

h = clear storey height of the wall

rn = reduction factor, where n= 2, 3 or 4, depending upon the

edge restraint or stiffening of the wall

The reduction factor to be applied depends upon the restraint offered

by adjoining elements. Masonry walls may be stiffened by a number

of rigid structural elements such as floors, roofs and other walls.

Stiffening walls should have a length of at least 1/5 of the clear height

Figure 4Minimum length of stiffening wall with openings

h2(window)

h2(door)

h

Stiffened wall Stiffening wall

>h/5 h1

t

1 (h1+ h

2)

5 2> t

and have a thickness of at least 0.3 times the effective thickness of

the wall to be stiffened. When the stiffening wall contains openings,

the minimum length of wall should be as shown in Figure 4 and the

stiffening wall should extend a distance of at least 1/5 of the storey

height beyond each opening.

Where a wall is restrained at the top and bottom by reinforced

concrete floors or roofs spanning from both sides at the same level or

by a reinforced concrete floor spanning from one side only and having

a bearing of at least 2/3 of the thickness of the wall then:

r2= 0.75

unless the eccentricity of the load at the top of the wall is greater

than 0.25 times the thickness of the wall, in which case r2= 1.0.

Where the wall is restrained by timber floors or roofs spanning from

both sides at the same level or by a timber floor spanning from one

side having a bearing of at least 2/3 the thickness of the wall but not

less than 85 mm, then:

r2= 1.0.

For walls restrained at the top and bottom and stiffened on one

vertical edge, use rn = the value r3from Figure 5 and where both

vertical edges are stiffened, use rn = the value r4from Figure 6. Note

that Equations (5.6), (5.7) and (5.8) in Eurocode 6, Part 11 may be

used as an alternative to the use of the graphs.

Effective thicknessFor a single-leaf wall, a double-leaf wall (with ties at a density of

2.5 per m2or greater), a faced wall, a shell bedded wall and a grouted

cavity wall, the effective thickness, tef, is taken as the actual thickness

Figure 5Graph showing values of r3

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0 1 2 3 4 5

Ratio hef

/tef

Reductionf

actor,r3

r2= 1.0

r2= 0.75



13/24


5

of the wall (t), provided this is greater than the minimum thickness,

tmin. The value of tminfor a loadbearing wall should be taken as 90 mm

for a single-leaf wall and 75 mm for the leaves of a cavity wall.

For a cavity wall the effective thickness is determined using the

following equation:

tef=

3Rt13+ t2

3 t2

where

t1= actual thickness of the outer or unloaded leaf

t2= actual thickness of the inner or loaded leaf

Note that the effective thickness of the unloaded leaf should not be

taken to be greater than the thickness of the loaded leaf and that ties

should be provided at a density of 2.5 per m2 or greater.

When a wall is stiffened by piers the effective thickness is enhanced byusing the following equation:

tef= rtt

where

tef = effective thickness

rt = coefficient obtained from Table 3

t = thickness of the wall

Slenderness ratio

The slenderness ratio of the wall is obtained by dividing the effectiveheight by the effective thickness and should not be greater than 27 for

walls subjected to mainly vertical loading. Note also that the effects of

creep may be ignored in walls with a slenderness ratio up to 27.

Figure 6Graph showing values of the reduction factor, r4

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0 1 2 3 4 5

Ratioh/l

Reduction

factor,r4

r2= 0.75

r2= 1.0

Assessment of eccentricityWhen a wall is subjected to actions that result in an eccentricity at

right angles to the wall, Eurocode 6 requires the resistance of the wall

to be checked at the top, mid-height and bottom. The eccentricity attop or bottom of the wall is:

Midei= + ehe+ einit 0.05t Nid

where

Mid = design value of the bending moment at the top or the

bottom of the wall resulting from eccentricity of the floor

load at the support

Nid = design value of the vertical load at the top or the bottom of

the wall

ehe

= the eccentricity at the top or bottom of the wall resulting

from the horizontal loads

einit= initial eccentricity for construction imperfections, which

may be taken as hef/450, with a sign that increases the

absolute value of eiand emas appropriate


The mid-height eccentricity, emk, is:

emk = em+ ek 0.05t

where

Mmd em = + ehm+ einit N

mdek = 0, when the slenderness ratio 27 (ie. ignoring creep)

Mmd = design value of the greatest moment at the mid-height

of the wall resulting from the moments at the top

and bottom of the wall, including any load applied

eccentrically to the face of the wall (see Figure 7)

Nmd = design value of the vertical load at the mid-height of the

wall, including any load applied eccentrically to the face

of the wall

ehm = the eccentricity at mid-height resulting from horizontal loads

A sub-frame analysis may be used as a simplified method forobtaining the moments at the top and bottom of vertically loaded

walls, as given in Annex C in Part 11 of Eurocode 6.

Table 3Stiffness coefficient,rt, for walls stiffened by piers

Ratio of pier spacing(centre to centre) to pierwidth

Ratio of pier thickness to actualthickness of wall to which it is bonded

1 2 3

6 1.0 1.4 2.0

10 1.0 1.2 1.4

20 1.0 1.0 1.0

Note

Linear interpolation is permitted in this Table.


14/24


6

Capacity reduction factorsAt the top or bottom of the wall, the reduction factor for slenderness

and eccentricity is given by:

eiFi= 1 2 t

where

Fi = reduction factor at the top or bottom of the wall

ei = eccentricity at the top or bottom of the wall


A method for calculating a capacity reduction factor at the mid-height

of the wall, Fm, is given in Annex G of Eurocode 6, Part 11, which

simplifies the principles given in Cl. 6.1.1. This is shown graphically in

Figure 8, which shows the corresponding capacity reduction factors for

different values of slenderness and eccentricity for an elastic modulus1000 fk , which is the value recommended in the UK NA.

The least favourable value of Fiand Fm should be used to calculate NRd.

Vertical load resistance ofsolid walls and columnsThe design resistance of a single-leaf wall per unit length, NRd, is given

by the following:

NRd= Ftfd

where

F = capacity reduction factor allowing for the effects of

slenderness and eccentricity of loading

Figure 7Moments from calculation of eccentricities

N1d

M1d

(at undersideof floor)

Mmd

(at mid-heightof wall)

M2d

(at top of floor)

Nmd

N2d

h

h2

h2

a) Section b) Bending moment diagram


fd= design compressive strength of the masonry (fk/gM)

For sections of small plan area, less than 0.1 m2,fdshould be

multiplied by (0.7 + 3A)

where

A = loadbearing horizontal cross-sectional area of the wall in m2

In the case of a faced wall, the wall may be designed as a single-leaf

wall constructed entirely of the weaker material with a longitudinal

joint between leaves.

A double-leaf (collar-jointed) wall may also be designed as for a

single-leaf wall provided that the leaves are tied together adequately

and both leaves carry similar loads and the cavity does not exceed

25 mm, or it may be designed as a cavity wall with one leaf loaded.

In the case of cavity walls, check each leaf separately using a

slenderness ratio based on the effective thickness of the wall.

Concentrated loadsFor a Group 1 unit (not shell bedded) the vertical load resistance is:

NRdc = bAbfd

where a1 Abb = 1 + 0.3 1.5 1.1

hc Aef

= enhancement factor for load that should not be lessthan 1.0 nor taken to be greater than:

1.25 +a1

or 1.5, whichever is the lesser 2hcFigure 8Capacity reduction factor, Fmat the mid-height of the wall

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

0 5 10 15 20 25 30Ratio, hef/ltef

Capacityreductionfactor,Fm

Eccentricity =

0.05t

0.10t

0.15t

0.20t

0.25t

0.30t

0.35t

0.40t

Values of Fmat the mid-height of the wall against slenderness ratio for differenteccentricities, based on E=1000 fk



15/24


7

a1 = distance from the end of the wall to the nearer edge of

the loaded area

hc = height of the wall to the level of the load

Ab = loaded area

Aef = effective area of the bearing,lefmtlefm = effective length of the bearing as determined at the

mid-height of the wall or pier

t = thickness of the wall, taking into account the depth of

recesses in joints greater than 5 mm wide

Ab/Aef 0.45

The enhancement factor, b, is shown graphically in Figure 9.

For walls built with Groups 2, 3 and 4 masonry units and when shell

bedding is used, it is necessary to check that, locally under the bearing

of a concentrated load, the design compressive stress does not exceed

the design compressive strength of the masonry,fd(i.e. bis taken to

be 1.0).

In any case, the eccentricity of the load from the centre line of the

wall should not be greater than t/4 as shown in Figure 10.

In all cases where a concentrated load is applied, the requirements

for vertical load design should be met at the mid-height of the wall

below the bearings. Account should be taken of the effects of any

other superimposed vertical loading, particularly where concentrated

loads are sufficiently close together for their effective lengths

to overlap.

The concentrated load needs to bear on a Group 1 unit or other solid

material. The length of this unit or bearing should equal the required

bearing length plus a length on each side of the bearing based on

a 60 spread of load to the base of the solid material. For an end

bearing the extra length is required on one side only.

Figure 9Enhancement factor, b, concentrated load under bearings

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0 0.1 0.2 0.3 0.4 0.45 0.5

Ratio, Ab/A

ef

Enhancementfactor,b

a1= 0

2a1= 1

hc

The concentrated load may be applied through a spreader beam of

adequate strength and stiffness that has a width the same as the wall

thickness, a height greater than 200 mm and a length greater than

three times the bearing length of the load. In this case the design value

of compressive strength beneath the concentrated load should not

exceed 1.5fd.

Walls subject to shear forcesThe design value of shear resistance is given by:

VRd = fvdtl c

where

VRd = the design value of shear resistance of the wall

fvd = the design value of the shear strength of the masonry (the

characteristic shear strength divided by the partial factor

for masonry, gM) based on the average vertical stresses over

the compressed part of the wall that is providing the shear

resistance

t = the thickness of the wall resisting the shear

lc = the length of the compressed part of the wall, ignoring any

part of the wall that is in tension

In calculating lcassume a linear distribution of the compressive stress,

take into account openings, etc. and do not include any area of the

wall subjected to vertical tensile stresses.

Effect of chasesEurocode 6 recognises that chases and recesses should not impair

the stability of a wall and provides appropriate guidance. Further

explanation is given in the third guide in this series, Lateral resistance3.

Figure 10Walls subjected to concentrated load

hc/2

NEdc

NEdc

a1

60o 60o60o

NEdc

++++

lefm

lefm

lefm

lefm

a1

h

hc

NEdc

NEdc

t

t/ 4

t

Ab60o

c) Plan d) Sectionb) Section

a) Elevation


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8

Ref: TCC/03/36. ISBN 978-1-904818-57-1First published December 2007(in partnership with the Modern Masonry Alliance)revised January 2009 and June 2013Price Group M MPA The ConcreteCentre

References1 BRITISH STANDARDS INSTITUTION. BS EN 1996: Eurocode 6 Design of masonry structures.BSI (4 parts). Including their NAs.

2 ROBERTS, JJ & BROOKER, O. How to design masonry structures to Eurocode 6: Introduction to Eurocode 6. The Concrete Centre, 2013.

3 ROBERTS, JJ & BROOKER, O. How to design masonry structures to Eurocode 6: Lateral resistance . The Concrete Centre. 2013.

4 BRITISH STANDARDS INSTITUTION. BS EN 7721: Methods of test for masonry units Determination of compressive strength. BSI, 2011.

5 BRITISH STANDARDS INSTITUTION. BS EN 10521: Methods of test for masonry Determination of compressive strength. BSI, 1999.

Selected symbols

Symbol Definition

A Loadbearing horizontal cross-sectional area of the wall in m2

a1 Distance from the end of the wall to the nearer edge of the loaded area

Ab Loaded areaAef Effective area of the bearing

ehe Eccentricity of the top or bottom of the wall resulting from horizontalloads

ehm Eccentricity at the middle of a wall, resulting from horizontal loads

ei Eccentricity of the wall

einit Initial eccentricity

em Load eccentricity

emk Eccentricity at the mid-height of the wall

fb Normalized mean compressive strength of a masonry unit

fd Design compressive strength of the masonry in the direction beingconsidered

fm Compressive strength of the mortar

fk Characteristic compressive strength of the masonry, in N/mm2

fvk Characteristic shear strength of masonry

fvd Design value of the shear strength of the masonry

g Total of the widths of the mortar strips

h Clear storey height of the wall

hc Height of the wall to the level of the load

hef Effective height of the wall

htot Total height of the structure

K Constant to be used with Equation (3.1) of Eurocode 6, Part 11

lc Length of the compressed part of the wall, ignoring any part of thewall that is in tension.

Symbol Definition

lefm Effective length of the bearing as determined at the mid-height of thewall or pier

Mid Design value of the bending moment at the top or the bottom of thewall resulting from eccentricity of the floor load at the support

Mmd Design value of the greatest moment at the mid-height of the wallresulting from the moments at the top and bottom of the wall,including any load applied eccentrically to the face of the wall

Nid Design value of the vertical load at the top or the bottom of the wall

Nmd Design value of the vertical load at the mid-height of the wall,including any load applied eccentrically to the face of the wall.

NRd Design resistance of a single-leaf wall per unit length

NRdc Design vertical load resistance to a concentrated load

t Thickness of the wall

t1 Effective thickness of the outer or unloaded leaf

t2 Effective thickness of the of the inner or loaded leaf

tef Effective thickness

tmin Minimum thickness of loadbearing wall

VRd Design value of shear resistance of the wall

v Notional inclination angle to the vertical

aand b Constants to be used with Equation (3.1) of Eurocode 6, Part 11

b An enhancement factor for concentrated load

F Capacity reduction factor allowing for the effects of slenderness andeccentricity of loading

gM Partial factor for a material property

rn Reduction factor (depending upon the edge restraint or stiffening ofthe wall, h/l and floor restraint)

rt Stiffness coefficient


For more information on Eurocode 6 and other questionsrelating to the design, use and performance of concrete units,visit www.eurocode6.org

Published by The Concrete Centre

Gillingham House, 38-44 Gillingham Street, London, SW1V 1HU

Tel: +44 (0)207 963 8000 | www.concretecentre.com

Members of the steering groupAli Arasteh, Brick Development Association; Owen Brooker, The

Concrete Centre; Ken Fisher, International Masonry Society; Cliff Fudge,

Aircrete Products Association; Charles Goodchild, The Concrete Centre;

Gerry Pettit, Concrete Block Association; John Roberts, Consultant.

Members of the steering group for 2nd revisionCliff Fudge, Aircrete Products Association; Charles Goodchild, The

Concrete Centre; Simon Hay, Brick Development Association; Andy

Littler, Concrete Block Association; John Roberts, Consultant; Guy

Thompson, The Concrete Centre.

AcknowledgementsThis publication was jointly sponsored by the following organisations:

Aircrete Products Association- www.aircrete.co.uk

Brick Development Association- www.brick.org.uk

Concrete Block Association- www.cba-blocks.org.uk

MPA - Mortar Industry Association- www.mortar.org.uk

MPA - The Concrete Centre- www.concretecentre.com

All advice or information from MPA The Concrete Centre (TCC) et al is intended only for use in the UK by those who will evaluate thesignificance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) forany loss resulting from such advice or information is accepted by TCC or their subcontractors, suppliers or advisors. Readers should note that

the publications from TCC et al are subject to revision from time to time and should therefore ensure that they are in possession of thelatest version.


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Guidance for lateral resistanceThis guide is the third in a series of three giving guidance on the design of

masonry structures to Eurocode 61. The first guide, Introduction to Eurocode 62

gives an introduction to design and assessment of actions using Eurocode 6

and also covers the specification and workmanship of masonry. The second

guide in the series3covers the design of vertically loaded masonry. This guide

explains how to design for horizontal actions. Throughout this guide the

Nationally Determined Parameters (NDPs) from the UK National Annexes(NAs) have been used. These enable Eurocode 6 to be applied in the UK.

Eurocode 6 methods for lateralresistanceEurocode 6 offers two approaches to the design of laterally loaded panels. The

first method relies on the flexural strength of the masonry and makes use of

yield line analysis to provide bending moment coefficients. The second method

is an approach based on arching and the assumption of a three-pinned arch

being formed within the wall. Both methods are presented in this guide.

The flexural strength approach is the most widely used and does not depend

upon rigid supports to resist arch thrust. In the UK, the reliance on the

development of tensile strength in the masonry has meant that this design

approach has usually been limited to transitory loads only. Eurocode 6 indicates

that the flexural strength of masonry should not be used in the design of walls

subjected to permanent lateral actions, e.g. gravity or reinforced retaining walls.

The assessment of the edge conditions is a requirement for the flexural strength

approach. A free edge is easily identified but some judgement on the part of the

engineer is necessary in deciding between simply supported or fixed conditions.

When considering the vertical support condition, attention also needs to bepaid to the potential position of movement joints and the changes the provision

of such joints make to the panel size and restraint conditions.

Where the walls are not rectangular, for instance a trapezoidal-shaped wall

to a mono-pitched structure, engineering judgement may be applied to

determine the effective wall height.

Wall panels with openings need to be treated with care and may typically be

sub-divided into smaller panels around the opening. It is beyond the scope of

this guide to deal with the topic in detail and reference should be made to

suitable handbooks4,5. Alternatively, a yield line analysis from first principles may

be used; the guidance in Practical yield line design6can be applied to wall panels.


3. Lateral resistanceEur Ing, Prof.J J Roberts BSc(Eng), PhD, CEng, FIStructE, FICE, FIMS, FCMI, MICT O Brooker BEng, CEng, MICE, MIStructE

IntroductionThis publication is part of a series of three guides

entitled How to design masonry structures using

Eurocode 6. The aim is to make the use of

Eurocode 6, Design of masonry structuresas easy as

possible by drawing together in one place key
















back cover).

Revision 2


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2

MEd2= a2WEdl2when the plane of failure is perpendicular to the bed

joints

where

a1 = bending moment coefficient parallel to the bed joints

(= a2, see Table 2)

a2 = bending moment coefficient perpendicular to the bed

joints (see Table 2)

WEd = design wind load per unit area (gQ WK)

l = length of panel between supports

= orthogonal ratio (fxk1/fxk2)

Lateral resistance using flexural strengthThe presence of a vertical load increases the flexural strength of a panel in

the direction parallel to the bed joints. The design moment of resistance

within the height of the wall is given by:

MRd=fxk1+sd Z

gMwhere

fxk1= characteristic flexural strength of masonry bending about an

axis parallel to bed joints (see Table 1)

gM = appropriate partial factor for materials

sd = design vertical load per unit area (< 0.2fk/gM)

Z = section modulus of the plan shape of the wall

fk = characteristic compressive strength (see Vertical resistance3).

If a damp proof course (dpc) is present in a wall subjected to flexure

then the degree of fixity may be altered. The bending moment

coefficient at a dpc may be taken as that for an edge over which full

continuity exists, provided that there is sufficient vertical load on the

dpc to ensure that the f lexural strength capacity is not exceeded.

Walls may be either horizontally and/or vertically spanning and the

ultimate strength of the wall is governed by the capacity of the

masonry to resist flexural tension. This capacity is enhanced by the

presence of vertical load. Clearly the potential flexural strength is

greater if the potential plane of failure is perpendicular rather than

parallel to the bed joint.

Figure 1 shows a flow chart for lateral load design. The designer needs

to assess the panel support conditions (or assume a free edge) and

decide whether these provide simple or continuous (fully restrained)

support. Care also needs to be exercised in considering the effect ofdpcs, movement joints, openings in walls, etc. There are handbooks

that provide further guidance on these aspects4,5.

Bending moments using coefficientsFor panels without openings, the bending moments per unit length

(MEd) are:

MEd1= a1WEdl2when the plane of failure is parallel to the bed joints

Obtain height,h

Check serviceability slenderness limits using Figures 2, 3 or 4 as appropriate

Check slenderness ratio h/t30 for wallssupported top and bottom only

Determine design value of vertical l oad, GEd, usingExpressions (6.10), (6.10a) or (6.10b) of Eurocode.

(see Introduction to Eurocode 6) Check shear

Characteristic verticalactions

Obtain thickness, t

t

h

Characteristic lateral actions

Obtain water absorptionfor clay masonry unit or

declared compressivestrength from

manufacturer for othermasonry types

Masonry unit properties

Type and group Dimensions

Strength

Determine requirementsfor mortar strength and

durability. See tables 5 & 6of Introduction to Eurocode 6

Determine design value oflateral actions, WEd, using

Expressions (6.10), (6.10a) or

(6.10b) of Eurocode. (seeIntroduction to Eurocode 6) Obtain fxk1and fxk2 from Table 1 and calculate

orthogonal ratio, m where: m= fxk1/ fxk2

Obtain a from Table 2 and calculate, MEd1and MEd2, where:

MEd1 = a1WEd l2, parallel to the bed joints or

MEd2 = a2WEdl2, perpendicular to the bed joints

Check MEd1 MRd1and MEd2MRd2

z

Obtain fxk2 from Table 1 and calculate design momentof resistance perpendicular to the bed joints, MRd2, where:

Obtain,gMfrom table 1Introduction to Eurocode 6

MRd2 =

fxk2ZgM

Obtain fxk1 from Table 1 and calculate design momentof resistance parallel to the bed joints, MRd1, where:

l

MRd1 =fxk1

+ sd ZgM


Figure 1Flow chart for the design of masonry walls to resist lateral actions


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The design procedure is iterative and may be summarised as

follows:

1 Make initial assumption of support condition.

2 Make assumptions as to strength and thickness of masonry unit

required; the minimum wall thickness or thickness of one leaf of acavity wall is 100mm.

3 Check serviceability slenderness limits. For wall panels supported

top and bottom only, hshould be limited to 30t. For other support

conditions use Figure 2 below or Figures 3 and 4 on page 6.

4 Determine orthogonal ratio,, and hence bending moment

coefficient appropriate to panel shape (Table 2).

5 Determine the design value of the applied moment, MEd.

6 Check the design value of the moment of resistance, MRd.

7 If MEd MRdthen the wall is acceptable if not return to either

step 1 or 2 and modify.

8 Check shear.

Cavity wallsIn a cavity wall, the design lateral load per unit area, WEd, may be

apportioned (either according to capacity or stiffness) between the

two leaves, provided that the wall ties are capable of transmitting the

actions that result from the apportionment.

Lateral resistance using archingWhere a masonry wall is built between supports capable of resisting

an arch thrust, then it may be assumed that a horizontal or vertical

arch develops within the thickness of the wall in resisting a lateral

load. The analysis can be based upon a three-pin arch, and the bearingof the arch thrust at the supports and at the central hinge should be

assumed to be 0.1 times the thickness of the wall.

Figure 2Limiting height and length to thickness ratios of walls restrained on allfour edges

Simply supported

or with full continuity

Key

l

80

70

60

50

40

30

20

10

0 120110100908070605040302010

Ratio

h/

t

h

Ratiol/t

Permissible range

3. Lateral resistance

3

Table 1Characteristic f lexural strength of masonry, fxk1and fxk2, in N/mm

2

Values of fxk1Plane of failure parallel tobed joints

Values of fxk2Plane of failureperpendicular to bed joints

Mortar strength class:

M12 M6 & M4 M2 M12 M6 & M4 M 2

Clay masonry units of Groups 1 and 2 having a water absorptionaof:

Less than 7% 0.7 0.5 0.4 2.0 1.5 1.2

Between 7%& 12%

0.5 0.4 0.35 1.5 1.1 1.0

Over 12% 0.4 0.3 0.25 1.1 0.9 0.8

Calcium silicate brick-sizedbmasonry units

0.3 0.2 0.9 0.6

Aggregate concrete brick-sizedbmasonry units

0.3 0.2 0.9 0.6

Aggregate concrete masonry units and manufactured stone of Groups1 and 2 and AACcmasonry units used in walls of thickness up to 100mmd,eof declared compressive strength (N/mm2):

2.9

0.25 0.2

0.4 0.4

3.6 0.45 0.4

7.3 0.6 0.5

Aggregate concrete masonry units and manufactured stone of Groups1 and 2 and AACcmasonry units used in walls of thickness of 250 mmor greaterd,e, of declared compressive strength (N/mm2):

2.9

0.15 0.1

0.25 0.2

3.6 0.25 0.2

7.3 0.35 0.3

Aggregate concrete masonry units and manufactured stone of Groups1 and 2 and AACcmasonry units used in walls of any thicknessd, ofdeclared compressive strength (N/mm2):

10.40.25 0.2

0.75 0.6

17.5 0.9f 0.7f

Key

a Tests to determine the water absorption of clay masonry units are to be conducted inaccordance with BS EN 77277.

b Units not exceeding 337.5 mm 225 mm 112.5 mm.

c Autoclaved aerated concrete (aircrete).

d The thickness should be taken as the thickness of the wall, for a single-leaf wall, or thethickness of the leaf, for a cavity wall.

e Linear interpolation may be used to obtain the values offxk1andfxk2for:1) wall thicknesses greater than 100 mm and less than 250 mm;2) compressive strengths between 2.9 N/mm2and 7.3 N/mm2in a wall of

given thickness.

f When used with flexural strength in the parallel direction, assume the orthogonal ratio= 0.3.


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4

Wall support condition A h/l

0.30 0.50 0.75 1.00 1.25 1.50 1.75 2.00

1.00 0.031 0.045 0.059 0.071 0.079 0.085 0.090 0.094

0.90 0.032 0.047 0.061 0.073 0.081 0.087 0.092 0.095

0.80 0.034 0.049 0.064 0.075 0.083 0.089 0.093 0.097

0.70 0.035 0.051 0.066 0.077

Eurocode 6 - Introduction

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Transcript of Eurocode 6 - Introduction