1

Actions and

combinations of actionswww.eurocode2.info

Outline

We will look at the following topics:

• Actions

• Ultimate limit state

• Serviceability limit state

• Combinations of actions

Outline

We will look at the following topics:

• Actions

• Ultimate limit state

• Serviceability limit state

• Combinations of actions

2

Characteristic values of actions

Characteristic values of actions are obtained by:

• measurements and calculations (e.g. self weights)• observations, measurements and analysis (e.g. climatic

loads)• surveys and experience (e.g. floor loads)• engineering judgement (e.g. some accidental actions)

Characteristic values for actions are normally obtained from ten parts of BS EN 1991 and their National Annexes

Classification of actions

• Direct (e.g. forces applied to the structure)

• Indirect (e.g. imposed deformations caused for example by

temperature changes or differential settlements)

• Permanent – variation in magnitude with time negligible

• Variable – variation in magnitude is neither negligible nor

monotonic

• Fixed – distribution and position over the structure is fixed

• Free – various spatial distribution over the structure possible

• Accidental – loads of short duration but with significant

magnitude

Eurocode 1 has ten parts:

• 1991-1-1 Densities, self-weight and imposed loads

• 1991-1-2 Actions on structures exposed to fire

• 1991-1-3 Snow loads

• 1991-1-4 Wind actions

• 1991-1-5 Thermal actions

• 1991-1-6 Actions during execution

• 1991-1-7 Accidental actions due to impact and explosions

• 1991-2 Traffic loads on bridges

• 1991-3 Actions induced by cranes and machinery

• 1991-4 Actions in silos and tanks

Eurocode 1

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Eurocode 1 Part 1-1: Densities, self-weight and imposed loads

• Bulk density of mass concrete is 24 kN/m3

• Bulk density of reinforced concrete is 25 kN/m3

• This represents 1.84% reinforcement

• Add 1 kN/m3 for wet concrete

• The UK NA uses the same loads as BS 6399

• Plant loading not given

Eurocode 1

Eurocode 1 UK NA

10.02.5Gross vehicle weight 30 kNF

7.04.8 per m ht (min 15.0)

Dense mobile stacking in warehousesE17

7.02.4 per m htGeneral storageE12

3.64.0Shopping areasD1/2

3.65.0Assembly area without fixed seating, concert halls, bars, places of worship

C5

2.72.5Offices for general useB1

2.0 4.0 minBalconies in hotels and motelsA7

2.02.5Balconies in single family dwelling unitsA5

2.02.0Bedrooms in hotels and motels, hospital wards and toilets

A3

2.01.5Bedrooms and dormitoriesA2

2.01.5All uses within self-contained dwelling unitsA1

Qk (kN)Char. value of pt load

qk (kN/m2)Char. value of udl

Example UseCate-gory

Outline

We will look at the following topics:

• Actions

• Ultimate limit state

• Serviceability limit state

• Combinations of actions

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Ultimate Limit State – CategoriesEurocode - EC 0

The ULS are divided into the following categories:

EQU Loss of equilibrium of the structure.

STR Internal failure or excessive deformation of the

structure or structural member.

GEO Failure due to excessive deformation of the ground.

FAT Fatigue failure of the structure or structural members.

Representative value of an action

Frep = FK

FK - is the characteristic value of action

FK - is the representative value

- Four values, namely, 1.0 or 0 or 1 or 2

0 Qk Combination Value 1 Qk Frequent Value

2 Qk Quasi-permanent Value

Fd = F Frep = F ( FK )

The code sets out the following:

• Basis for calculating design resistance of materials

• Combinations for ultimate limit state

Either:

G, jGk,j + Q,1 Qk,1 + Q,I0,IQk,I Exp. (6.10)

Or the more adverse of:

G, j Gk,j + Q,10,1 Qk,1 + Q,I 0,I Qk,I Exp. (6.10 a)

G, j Gk,j + Q,1 Qk,1 + Q,I 0,I Qk,I Exp. (6.10 b)

= 0.925 (UK NA)

Eurocode

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For one variable action: 1.25 Gk + 1.5 QkProvided:

1. Permanent actions < 4.5 x variable actions2. Excludes storage loads

Eurocode – ULS (GEO/STR)

γQ,i Ψ0,i Qk,iγQ,1 Qk,1γG,j,inf Gk,j,infξ γG,j,supGk,j,supEqn (6.10b)

γQ,i Ψ0,i Qk,iγQ,1Ψ0,1Qk,1γG,j,inf Gk,j,infγG,j,sup Gk,j,supEqn (6.10a)

γQ,i Ψ0,i Qk,iγQ,1 Qk,1γG,j,inf Gk,j,infγG,j,sup Gk,j,supEqn (6.10)

OthersMain(if any)FavourableUnfavourable

Accompanying variable actions

Leading variable action

Permanent actionsComb’tionexpression reference

Design values of actions, ultimate limit state – persistent and transient design situations (Table A1.2(B) Eurocode)

1.5 Ψ0,i Qk,i1.5 Qk,11.0 Gk0.925x1.35GkEqn (6.10b)

1.5 Ψ0,i Qk,i1.5 Ψ0,1 Qk1.0 Gk1.35 GkEqn (6.10a)

1.5 Ψ0,i Qk,i1.5 Qk,11.0 Gk1.35 GkEqn (6.10)

Eqn (6.10), (6.10a) or (6.10b) ?

1.0

1.5

2.0

2.5

3.0

1 2 3 4 5 6

Eqn (6.10)

Eqn (6.10a)

Eqn (6.10b)

Ratio Gk/Qk

Fac

tor,

F(U

ltim

ate

load

= F

x G

k)

4.5

Eurocode – ULS (EQU)

γQ,i Ψ0,i Qk,iγQ,1 Qk,1γG,j,inf Gk,j,infγG,j,sup Gk,j,supEqn (6.10)

OthersMain(if any)FavourableUnfavourable

Accompanying variable actions

Leading variable action

Permanent actionsComb’tionexpression reference

Design values of actions, ultimate limit state – persistent and transient design situations (Table A1.2(A) Eurocode)

1.5 Ψ0,i Qk,i1.5 Qk,10.9 Gk1.10 GkEqn (6.10)

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Outline

We will look at the following topics:

• Actions

• Ultimate limit state

• Serviceability limit state

• Combinations of actions

Eurocode SLS

Eurocode: Annex A1 - Buildings

00.20.5Wind loads on buildings (BS EN 1991-1-4)

00.20.5Snow (For sites located < 1000 m asl)

000.7Category H: roofs

0.30.50.7Category G: traffic area(30 kN < vehicle weight < 160 kN)

0.60.70.7Category F: traffic area(vehicle weight < 30 kN)

0.80.91.0Category E: storage areas

0.60.70.7Category D: shopping areas

0.60.70.7Category C: congregation areas

0.30.50.7Category B: office areas

0.30.50.7Category A: domestic, residential areas

210Action

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Serviceability Limit States

Characteristic combination (Normally used for irreversible limit states, e.g. where deflection would cause damage to other components)

Gk,j + Qk,1 + 0,IQk,I

Frequent combination (Normally used for reversible limit states, e.g. cracking in prestressed concrete)

Gk,j + 1,1Qk,1 + 2,IQk,I

Quasi-permanent combination (Normally used for long term effects and appearance of the structure, e.g. deflection)

Gk,j + 2,IQk,I

Eurocode SLS

Outline

We will look at the following topics:

• Actions

• Ultimate limit state

• Serviceability limit state

• Combinations of actions

Procedure for establishing value of actions for analysis

1. Identify various design situations (e.g. persistant,

transient,accidental

2. Identify all realistic actions that can occur

3. Determine the partial factors for each applicable combination

of actions

4. Arrange the action to produce the most critical conditions

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UK NA: Arrangement of actions

All spans loaded

Alternate spans loaded

1.35 Gk or 1.25 Gk

1.5 Qk

1.35 Gk or 1.25 Gk

1.5 Qk

1.35 Gk or 1.25 Gk

1.5 Qk

Cantilever

EQU1.1 Gk

1.5 Qk0.9 Gk

STR/GEO - 1 1.35 Gk or1.25 Gk

1.5 Qk

STR/GEO - 31.35 Gk or1.25 Gk

1.5 Qk

1.0 Gk

1.5 Qk

STR/GEO - 2

STR/GEO - 31.0 Gk

1.5 Qk