b tan kh - consteel seminar - 6aug14

1. A summary of essential

differences between EC2 and

BS8110

Prof Tan Kang Hai

Email: [email protected]

Director of Protective Technology Research Centre (PTRC)

School of Civil & Environmental Engineering All the rights of 11 lecture materials belong to Tan Kang Hai

1

Outline

Similarities and differences of BS8110 and EC2

Influence of material behaviour

Basis of design and load combination

Global geometric imperfections

Nonlinear versus linear elastic analysis

Shear design of beams and slabs

Design of columns

Detailing of members

2

Outline







Design of columns


3

- Ultimate limit state and serviceability limit state

- Permanent actions, imposed loads and wind loads

- Plane strain assumption for design of beams,

slabs, columns, and walls

- Linear elastic analysis

- Linear elastic analysis with limited distribution

- Plastic analysis

Similarities

of BS8110 and EC2

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

4

EC2 is phenomenon-based code unlike the BS8110

Entire code is based on reliability index

Based on Model Concrete Code 1978 and 1990

1. Influence of material behaviour

2. Basis of design and load combination

3. Global geometric imperfections

4. Nonlinear versus linear elastic analysis

5. Shear design of beams and slabs

6. Design of columns

7. Detailing of members

Differences

between BS8110 and EC2 Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

5

Outline







Design of columns


6

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

max stress level for idealized curve must be below the max stress

of the schematic diagram for the same area under the curve

(3.15)

The design value of concrete compressive strength fcd is given by:

Where the factor allows for the difference between the

bending strength and the cylinder crushing strength of concrete,

and is the concrete material partial safety factor.

EC2 stress-strain relationships of

concrete under compression

7

ckck

c

ckcccd f

fff 567.0

5.1

85.0

5.1c

Class 1 Class 2 Class 3

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Table 3.1 Strength and deformation

characteristics for concrete

8

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

EC2 stress-strain relationships of

reinforcing steel

k=ft/fy indicates ductility; the greater the k value, the longer is the

plateau or the plastic zone uk.

The design value of the modulus of elastic Es is 200 GPa. In

the ultimate limit state calculation, by taking a partial safety

factor of , design values of yield strength fyd and

yield strain of reinforcing steel are respectively computed as:

9

15.1s

y

yk

yk

yd ff

f 87.015.1

00217.0

1020015.1

105006

3

ss

yk

yE

f

10

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Table C.1: Properties of reinforcement

Product form Bars and de-coiled

rods

Wire Fabrics Requirement or

quantile value (%)

Class A B C A B C -

Characteristic yield

strength fyk or f0.2k (MPa)

400 to 600

5.0

Minimum value of

k = (ft/fy)k

1.05

1.08

1.15

11

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

7.2.3 Tensile properties

The specified values for the tensile properties

are given in Table 4.

Table 4 Characteristic tensile properties

Yield strength,

Re

MPa

Tensile/yield strength ratio,

Rm/Re

Total elongation at

maximum force, Agt

%

B500A 500 1.05a 2.5b

B500B 500 1.08 5.0

B500C 500 1.15,

12

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

7.2.3 Tensile properties

BS 8666:2005 - Scheduling, dimensioning, bending and cutting of steel

reinforcement for concrete Specification has been revised to incorporate:

(i) Shape codes available under BS EN ISO 3766:2003; (ii) Revised

notation in accordance with BS 4449:2005 and BS EN 10080:2005; (iii)

Revisions to BS 4449:2005 (including the omission of grade 250 and grade

460 reinforcement)

.

13

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

BS system:

notation is T

Similar to BS specification

Outline







Design of columns


14

15

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Leading variable action and accompanying variable action:

Comparison of partial factors for loading

Design situations BS 8110 EC2

With one variable action

(Live load) 1.4DL + 1.6LL 1.35Gk + 1.5Qk

With one variable action

(Wind load) 1.4DL + 1.6W 1.35Gk + 1.5Wk

With two variable

actions

(leading and

accompanying)

(Wind & live loads)

1.2DL + 1.2LL +

1.2W

1.35 Gk + 1.5 Qk + 0.75Wk

Or 1.35 Gk + 1.05 Qk + 1.5Wk

0.7x1.5Qk for office or

residential buildings 0.5x1.5Wk

(6.10)

Load combinations

according to EC0

16

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Ultimate states Combinations of actions

Eq. (6.10)

For EQU, STR,

GEO

1.35 Gk + 1.5 Qk + 1.5*0.5Wk

Or 1.35 Gk + 1.05 Qk + 1.5Wk

Eq. (6.10a)

For STR, GEO

1.35 Gk + 1.5*0.5Wk +1.5*0.7 Qk

1.35 Gk + 1.5*0.5Wk

Eq. (6.10b)

For STR, GEO

0.925*1.35Gk + 1.5Wk +1.5*0.7 Qk

Or 0.925*1.35 Gk + 1.5Wk

To be applied together

(6.10a)

(6.10b)

For unfavourable

permanent

actions single source principle

in EC0 - Table

A1.2 (B) Set B

Load combinations

according to EC0

17

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Instantaneous value of Q

t2 t3

Combination value 0Qk

Characteristic value Qk

Frequent value 1Qk

Time

Quasi-permanent value 2Qk

t1

Fig. Representative values of variable actions

Load combinations

according to EC0

18

Combination Value 0Qk

Frequent Value 1Qk

Quasi-permanent Value 2Qk

OTHER REPRESENTATIVE VALUES OF VARIABLE ACTIONS:

For:

1) ULS and

2) Irreversible SLS

3) Apply to non-leading variable

actions

(consider the reduced probability of

simultaneous occurrences of two or

more independent variable actions.)

For:

1) ULS involving accidental actions,

and

2) Reversible SLS

3) Apply to leading variable actions

(e.g. for buildings, the frequent value is

chosen so that the time it is exceeded is

0.01 of the reference period of 50

years)

For:

1) ULS involving accidental

actions, and

2) Reversible SLS

3) Used for calculation of long-

term effects.

(e.g. for loads on building floors, the

quasi-permanent value is chosen

so that the proportion of the time it

is exceeded is 0.50 of the reference

period.)

1. BS EN 1990:2002 (EC0)

19

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Combinations of actions for the Serviceability Limit State

Combination Permanent action

Gd Variable action Qd

Leading Others

Characteristic Gk,j Qk,1 0,iQk,i

Frequent Gk,j 1,1Qk,1 2,iQk,i

Quasi-

permanent Gk,j 2,1Qk,1 2,iQk,i

Load combinations

according to EC0

20

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Load combinations

according to EC0

Exposure Reinforced members and

prestressed members

without bonded tendons

(quasi-permanent load

combination)

Prestressed

members with

bonded tendons

(frequent load

combination)

X0, XC1 0.3a 0.2

XC2, XC3, XC4 0.3 0.2b

XD1, XD2, XD3, XS1, XS2,

XS3

0.2 and decompressionc

a For X0, XC1 exposure classes, crack width has no influence on durability and this limit is set to produce

acceptable appearance. In the absence of specific requirements for appearance this limit may be relaxed.

b For these exposure classes, in addition, decompression should be checked under the quasi-permanent

combination of loads.

c wmax = 0.2 mm applies to parts of the member that do not have to be checked for decompression.

Crack width limit

UK Annex Table NA.4 Recommended values of wmax (mm)

maxw w

21

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Failure conditions under ULS

according to EC0

1.35Gk

1.35Gk + 1.5Qk

1.35Gk + 1.5Qk

1.0Gk

1.35Gk 1.35Gk

1.35Gk + 1.5Qk

Single source for Gk

1.4Gk + 1.6Qk

1.4Gk + 1.6Qk

1.4Gk + 1.6Qk

22

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Load combinations

according to EC2 Cl 5.1.3

1.35Gk + 1.5Qk

1.0Gk 1.0Gk

Outline







Design of columns


23

24

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

In EC2, there is no notional

horizontal load.

Global geometric imperfections due

to out-of-plumbness of vertical

elements must be modelled by

equivalent loads in two design

situations:

Persistent design situations:

Possible extreme loading condition

of wind, imposed loads.

Accidental design situations: fire,

impact.

When to consider

geometric imperfections?

25

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Imperfection loads are quantified by three considerations:

Global analysis of building structures.

Analysis of isolated vertical members.

Analysis of floor diaphragms as horizontal elements

transferring forces to bracing members.

Only imperfection loads in global analysis are similar to

notional horizontal loads, although they are very different in

the way to be considered.

Imperfections need not be considered for serviceability limit

states.

When to consider


26

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

The structure is assumed with inclination l, given by:

where: 0 is the basic value (0 = 1/200)

h is the reduction factor for height

m is the reduction factor for number of members:

where m is the number of vertically continuous members

in the storey contributing to total horizontal forces on the

floor.

How to consider


27

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members The imperfection on each floor may be represented by a

force acting on the floor where Na and Nb are the factored

axial forces above and below the floor considered. (see

EC3 Figure 5.3)

To design for slab

(member transferring

forces to bracing

elements)

How to consider


28

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Lateral load case: in BS 8110: Hdesign = Max(HN, 1.2Wk)

However, in EC 2: Hdesign = 1.0 Hi + FWk where Hi is horizontal loads for geometric imperfection

How to consider


Outline







Design of columns


29

30

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

First order elastic analysis: represents conditions at normal service loads very well (Section 5.4)

First order elastic analysis with limited redistribution: excluded nonlinearity, represents conditions at normal

service loads very well (Section 5.5)

First order inelastic analysis: Plastic analysis with no geometrical nonlinearity (Section 5.6)

Second order elastic analysis: Effects of finite deformation considered. Good representation of P- effect

(Section 5.7)

Second order inelastic analysis: Both geometrical and material nonlinearities are considered. Model can faithfully

reflect the behavior of structures up to ultimate limit state

Different types of analysis

31

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Source: Fig. 8.1 of Matrix Structural Analysis, Second Edition, William

McGuire, Richard H. Gallagher and Ronald D. Ziemian, John Wiley & Sons, Inc,

2000, ISBN 0-471-12918-6

e

Different types of analysis

32

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Taken from EC2

Local second order effects

Cl 5.8.7 or Cl 5.8.8

33

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

States that if there are additional action effects caused by

structural deformations under the influence of significant axial

load, second order effects should be considered.

Local second order effect

on isolated members (P-)

Global second order effect on whole structure (P-)


Cl 5.8.7 or Cl 5.8.8

How to account for second order effects?


- Method based on nominal stiffness (EC2 Clause 5.8.7)

- Method based on nominal curvature (EC2 Clause 5.8.8)


Cl 5.8.7 or Cl 5.8.8 Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Outline







Design of columns


35

36

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Methodology

DC : the concrete acts as the

diagonal struts;

VT: the stirrups act as the

vertical ties;

BT: the tension reinforcement

forms the bottom chord;

TC: the compression

steel/concrete forms the top

chord.

= 21.80 450 (strut angle)

(EC2 6.2.3(2))

(a) Beam and reinforcement

(b) Analogous truss

EC2 uses The Variable Strut Inclination Method for shear

design.

BS 8110 uses Truss Analogy with truss angle = 450

37

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Comparison of shear design

BS 8110

1. = 45o

2. BS 8110 compares shear

stresses.

3. The maximum shear

stress is limited to 5

N/mm2 or 0.8fcu,

whichever is the lesser.

4. The design shear force

must be less than the

sum of the shear

resistance of concrete

plus shear links.

EC2

1. = 21.8o 45o

2. EC 2 compares shear forces.

3. The maximum shear capacity

of concrete VRd,max cannot be

exceeded.

4. Where the applied shear

exceeds the min shear

resistance of concrete VRd,c,

the shear reinforcement

should be capable of resisting

all the shear forces.

38

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Punching shear design of slabs

Control perimeters

Basic control perimeter u1:

Control perimeters

39

For slabs with a rectangular column with a rectangular head

with lH < 2hH, the value rcont may be taken as the lesser of:

1 2 12 0.56 and 2 0.69 cont contr d l l r d l

1 1 1 2 2 2 1 22 ; 2 ;

H Hl c l l c l l l

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Control perimeters

40

For slabs with enlarged column heads where lH > 2hH, the

control sections both within the head and in the slab should

be checked. For circular columns:

cont,ext

cont,int

2 0.5

2 0.5

H

H

r l d c

r d h c

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Punching shear stress VEd

41

(EC2 6.4.3 (3))

How to calculate b?

For rectangular columns:

221

1 1 2 2 14 16 2

2

cW c c c d d dc

1

1

1 Ed

Ed

M uk

V Wb

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Outline







Design of columns


42

43

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Differences in symbols

44

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Differences in symbols

45

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Differences in design

46

Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

Differences in design

Outline







Design of columns


47

48

Minimum cover due to

environmental conditions cmin,dur Similarities and

differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

49



differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

50



differences of

BS8110 and EC2

Influence of

material behaviour

Basis of design

and load

combination

Global geometric

imperfections

Nonlinear versus

linear elastic

analysis

Shear design of

beams and slabs

Design of columns

Detailing of

members

DESIGN ANCHORAGE LENGTH

For the effect of the form of the

bars assuming adequate cover

1=0.7~1.0 (in comp. is 1.0)

For the effect of concrete minimum

cover 2=0.7~1.0 (in comp. is 1.0)

For the effect of confinement by tied

transverse bars along the design anc.

length 3=0.7~1.0 (in comp. is 1.0)

For the effect of confinement by welded

transverse bars along the design anc. length

4=0.7

For the effect of confinement by transverse

pressure along the design anc. length 5=0.7

Basic anchorage length

Design stress of the bar:

Design ultimate stress:

For the quality of bond condition 1=0.7

(poor) - 1=1.0 (good)

For the bar diameter 2=1.0 for 32mm 2=(132-)/100 for >32mm

The design concrete tensile strength (

DESIGN ANCHORAGE LENGTH lbd


52

Complex load combinations due to leading and accompanying

variable load cases;

In EC0 - Eq 6.10 compared with Eq 6.10(a) and Eq 6.10(b).

Definition of member types and the choice of suitable elements;

Represent global geometrical imperfection load by horizontal

loads and consider in all ULS;

Need to consider global second order effect unless structure

satisfies Clause 5.8.3.3;

Calculation model should reflect realistic global and local

behaviour of the designed RC structure

High strength concrete is permitted (above 50 MPa till 90 MPa);

SUMMARY on Differences between BS and EC

53

Thank You!

54

b tan kh - consteel seminar - 6aug14

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