NCCI Vertical and horizontal deflection limits for multi-storey buildings.pdf

NCCI: Vertical and horizontal deflection limits for for multi-storey buildings

NCCI: Vertical and horizontal deflection limits for multi-storey buildings SN034a-EN-EU

NCCI: Vertical and horizontal horizontal deflection limits limits for multistorey buildings Recommendations Recommendations and guidelines guidelines are are given for horizontal and vertical vertical deflection deflection limits for multi-storey multi-storey commercial commercial and residential residential buildings. buildings.

Contents

t n e m e e r g A e c n e c i L l e e t S s s e c c A e h t f o s n o i t i d n o c d n a s m r e t e h t o t t c e j b u s s i t n e m u c o d s i h t f o e s U . d e v r e s e r 9 s 0 t 0 h g 2 i , r 9 l l 0 a e n t u h g J i , r y y a p d o s c e s u i l T a n i r o t e d a e t m a s i e r h C T

1.

Introduction

2

2.

Loads

2

3.

Horizontal deflection limits

3

4.

Vertical deflection limits

5

5.

References

7

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NCCI: Vertical and horizontal deflection limits for multi-storey buildings


1.

Introduction

No specific deflection limits are set in EN 1993-1-1 [1]. Instead it states in § 7.2 that the serviceability criteria, including deflection limits, should be specified and agreed with the client for each project. Furthermore, the verification should be based on criteria concerning deformations that affect appearance, comfort of users, functioning of the structure or that cause damage to finishes or non-structural members. In some countries, the National Annex to EN 1993-1-1 specifies the limits. Where limits are specified they have to be observed. If no limits are specified in the National Annex the following might be helpful:




Relevant functional requirements should be considered, e.g. for flat roofs, water run off has to be ensured to avoid ponding.



To avoid damage to sensitive finishes or non-structural members, e.g. partition walls with fragile elements such as masonry, glass etc, more onerous criteria may have to be adopted.



Appearance is very subjective and also context sensitive. In most cases precambering or adjustments of false ceilings can disguise the deflections.



Comfort of users may be a serious concern for long span or shallow floors. However, deflection criteria are not an adequate tool to manage the issue. SN036 provides guidance for floor vibrations.

Often it is the deflection at the serviceability limit state that governs a structure’s design, and therefore the selected deflection limits are of high importance. Different countries have different recommended values for horizontal and vertical deflection limits; examples are presented in sections 3 and 4.

2.

Loads

2.1

Serviceability limit state

EN 1990 gives three different combinations for serviceability limit states i.e. a characteristic, a frequent and a quasi-permanent combination. In the above-mentioned load combinations, ψ factors are used, as follows: ψ 0

is used in the characteristic combination that is applied for irreversible limit states, i .e. stresses above the yield point.

ψ 1

is used in the frequent combination that is applied for reversible limit states, i.e. stresses below the yield point. This is relevant for deflection limitations of steel structures.

ψ 2

is used in both the frequent and the quasi-permanent combination. In both cases the factor is used for long-term effects. These are not relevant for steel structures and therefore ψ 2 = 0. For composite structures the effects of creep may be taken into account by using appropriate modular ratios for the concrete; where this is the case, may be taken as 0.

ψ 2

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Consequently, the relevant load combinations are: 1.

The characteristic combination for irreversible limit states. This combination is only required to be considered for the serviceability limit state when some plasticity is permitted, e.g. certain classes of continuous composite beams.

∑ Gk , j + P + Qk ,1 + ∑ψ 0,i Qk ,i j ≥1

2.

(1)

i >1

The frequent combination (with ψ 2 = 0) for the reversible limit state.

∑ Gk , j + P + ψ 1,1Qk ,1

(2)

j ≥1

2.2

Ultimate limit state

Deflections at the ultimate limit state need only be considered when the deflection may lead to additional loading, for example water ponding on flat roofs.


3.

Horizontal deflection limits

In Table 3.1 guidance is given on horizontal deflection limits for a selection of countries. The definitions of horizontal deflections in Annex A1 to EN 1990 [2] are shown in Figure 3.1. u

u i

H i

H

L

Notation: u

Overall horizontal displacement over the building height H .

u i

Horizontal displacement over a storey height H i

Figure 3.1

Definitions of horizontal deflections.

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Table 3.1 Country

France

Horizontal deflection limits Structure

Multi-storey buildings

Deflection limits u

u i

H /300

H /250 i

Comments

The values to the left are given in the French National Annex to EN 1993-1-1 and should be used if nothing else is agreed with the client. The values of the deflections calculated from the characteristic combinations should be compared to these limits. The limit given for u applies when the height H does not exceed 30 m. Otherwise, see the contract.

Germany

Spain t n e m e e r g A e c n e c i L l e e t S s s e c c A e h t f o s n o i t i d n o c d n a s m r e t e h t o t t c e j b u s s i t n e m u c o d s i h t f o e s U . d e v r e s e r 9 s 0 t 0 h g 2 i , r 9 l l 0 a e n t u h g J i , r y y a p d o s c e s u i l T a n i r o t e d a e t m a s i e r h C T

There are no national deflection limits. The limits should be taken from manufacturers’ instructions (technical approvals) or should be agreed with the client. Multi-storey buildings: In general

H /500

With fragile partition walls, facades envelopes or rigid floor finishing elements High rise slender buildings (in buildings taller than 100 meters, more restrictive limits could be necessary due to wind effects such as vibrations). Sweden

UK

For medium rise buildings

H /300 i H /500 i

The values to the left are given in the national technical document for steel structures [3] and in the Technical Building Code [4] and should be used if nothing else is agreed with the client.

H /600

–

–

The national regulations [5] contain only a principle that deformations should not be harmful or damage other parts of the buildings.

H /300

H /300 i

There are no national deflection limits The values to the left are recommended in industry guidance [6].

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4.


In Table 4.1, guidance is given on vertical deflection limits for a selection of countries. The definitions of vertical deflections in Annex A1 to EN 1990 [1] are shown in Figure 4.1. W c

W 1 W 2

W max

W tot

W 3

Notation:


w c

Precamber in the unloaded structural member

w 1

Initial part of the deflection under permanent loads of the relevant combinations of actions

w 2

Long-term part of the deflection under permanent loads

w 3

Additional part of the deflection due to the variable actions of the relevant combination of actions

w tot

Total deflection as sum of w 1, w 2, w 3

w max

Remaining total deflection taking into account the precamber

Figure 4.1

Definitions of vertical deflections.

Table 4.1


Country

France

Germany

Structure

Deflection limits

Comments

w max

w 2+w 3

Roof, in general

L /200

L /250

Roofs frequently carrying personnel other than for maintenance

L /200

L /300

The values to the left are given in the National Annex to EN 1993-1-1 and should be used if nothing else is agreed with the client.

Floors, in general

L /200

L /300

Floors and roofs supporting plaster or other brittle toppings or non-flexible parts

L /250

L /350

The values of the deflections calculated from the characteristic combinations should be compared to these limits.

Floors supporting columns (unless the deflection has been included in the global analysis for the ultimate limit state)

L /400

L /500

When w max can affect the appearance of the building

L /250

–

There are no national deflection limits. The limits should be taken from manufacturers’ instructions (technical approvals) or should be agreed with the client.

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Country

Structure

Deflection limits w max

Spain


w 2+w 3

The values to the left are given in the national technical document for steel structures [3] and in the Technical Building Code [4] and should be used if nothing else is agreed with the client.

Roofs, with access only for maintenance

–

L /250

Roofs in general

–

L /300

Beams and floors, without fragile elements susceptible to failure

–

L /300

Beams and floors, supporting ordinary partition walls and rigid floor finishing elements with expansion joints

-

L /400

Beams and floors, supporting fragile elements such as, partition walls, facades envelopes or rigid floor finishing elements

-

L /500

Beams supporting columns

-

L /500

Beams supporting masonry walls

-

L /1000

–

–

There are no national deflection limits.

Not checked

L/200

There are no national deflection limits. The values presented are recommended in industry guidance [6].

Sweden UK

Comments

Beams generally

is usually ignored. It is negligible for both steel beams and unpropped composite construction (the norm in the UK). W 2

For brittle finishes

L/360

There are no national deflection limits. The values presented are recommended in industry guidance [6]. is usually ignored. It is negligible for both steel beams and unpropped composite construction (the norm in the UK). W 2

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5. 1

References EN 1993-1-1 Design of steel structures – Part 1-1: General rules and rules for buildings. CEN:

2

EN 1990 Eurocode. Basis of structural design. CEN .

3

Instrucción de Acero Estructural

Ministerio de Fomento, España, 2006. 4

Código Técnico de la Edificación

Ministerio de Vivienda, España, 2006 5

Regelsamling för konstruktion, Boverkets konstruktionsregler, BKR, byggnadsverkslagen och byggnadsverksförordningen,

Boverket, Sverige, 2003 t n e m e e r g A e c n e c i L l e e t S s s e c c A e h t f o s n o i t i d n o c d n a s m r e t e h t o t t c e j b u s s i t n e m u c o d s i h t f o e s U . d e v r e s e r 9 s 0 t 0 h g 2 i , r 9 l l 0 a e n t u h g J i , r y y a p d o s c e s u i l T a n i r o t e d a e t m a s i e r h C T

6

Steelwork Design Guide to BS 5950 Volume 4: Essential Data for Designers, P 070, The Steel Construction Institute, 1991.

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Quality Record RESOURCE TITLE


Reference(s) ORIGINAL DOCUMENT Name

Company

Date

Created by

Björn Uppfeldt

SBI

Technical content checked by

Bernt Johansson

SBI

1. UK

G W Owens

SCI

10/3/06

2. France

A Bureau

CTICM

10/3/06

3. Sweden

A Olsson

SBI

10/3/06

4. Germany

C Müller

RWTH

10/3/06

5. Spain

J Chica

Labein

10/3/06

G W Owens

SCI

08/6/06

Editorial content checked by Technical content endorsed by the following STEEL Partners:


Resource approved by Technical Coordinator TRANSLATED DOCUMENT This Translation made and checked by: Translated resource approved by:

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NCCI Vertical and horizontal deflection limits for multi-storey buildings.pdf

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