SN035a-En-EU_NCCI- Practical Deflection Limits for Single Storey Buildings

NCCI: Practical deflection limits for single storey buildings SN035a-EN-EU

NCCI: Practical deflection limits for single storey buildings

Recommendations and guidelines for horizontal and vertical defection for single storey buildings.

Contents

1. Introduction 2

2. Horizontal deflections for portal frames 2

3. Vertical deflections for portal frames 5

4. Vertical deflections for horizontal roof members 6

5. References 8

NCCI: Practical deflection limits for single storey buildingsC

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1. Introduction No specific deflection limits are set in Eurocode 1993-1-1 [1]. According to EN 1993-1-1, § 7.2 and EN 1990 – Annex A1.4 [2], deflection limits should be specified for each project and agreed with the client. The National Annex to EN 1993-1-1 may specify limits for application in individual countries. Where limits are specified they have to be satisfied. Where limits are not specified, the following might be helpful when deciding relevant deflection limits.

2. Horizontal deflections for portal frames

u

H

L

Figure 2.1 Definition of horizontal deflection


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http://www.access-steel.com/discovery/linklookup.aspx?id=EC130

http://www.access-steel.com/discovery/linklookup.aspx?id=EC130


Table 2.1 Limiting horizontal deflection

Deflection limits

Country Structure

u

Comments

France Portal frames without gantry cranes Buildings with no particular requirements regarding the deflection.

Deflection at the top of the columns

H/150

Difference of deflection between two consecutive portal frames

B/150

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.

Member supporting metal cladding

Post H/150

Rail B/150

Other single storey buildings Buildings with particular requirements regarding the deflection (brittle walls, appearance…).

Deflection at the top of the columns

H/250

Difference of deflection between two consecutive portal frames

B/200

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

Spain Portal frames (without fragile elements susceptible to failure in the envelopes, façade and roof)

H/150 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.

Single storey buildings with horizontal roofs (without fragile elements susceptible to failure in the envelopes, façade and roof)

H/300

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


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Deflection limits

Country Structure

u

Comments

UK Portal frames without gantry cranes, with walls of :

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

Steel sheeting - deflection at top of column

H/100

Fibre reinforced sheeting - deflection at top of column

H/150

Brickwork - deflection at top of column

H/300

Differential deflection between two consecutive portal frames

660

22 BH +

Hollow concrete brickwork - deflection at top of column

H/200

Differential between two consecutive portal frames

500

22 BH +

Precast concrete units - deflection at top of column

H/200

Differential defection between two consecutive portal frames

330

22 BH +


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3. Vertical deflections for portal frames

Figure 3.1 Definitions of vertical deflection of apex of portal frame

Recommended limiting values for vertical deflection are given in Table 3.1

Table 3.1 Vertical deflection limits

Deflection limits Comments Country Structure

wmax w3

Roofs in general L/200 L/250

Roofs frequently carrying personnel other than for maintenance

L/200 L/300

France

Roofs supporting plaster or other brittle toppings or non-flexible parts

L/250 L/350

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

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

Sweden There are no national deflection limits.


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Deflection limits Comments Country Structure

wmax w3

UK Portal frames without gantry cranes, with rafter slopes ≥3r

There are no national deflection limits. These figures are recommended in industry guidance [6].

Differential deflection relative to adjacent frame

- metal sheeting and fibre reinforced sheeting 100

B

- felted metal decking on purlins 100B

- felted metal supported on rafters 200

B

4. Vertical deflections for horizontal roof members 4.1 Serviceability limit states Guidance for the deflection limits are given in Table 4.1 for a selection of countries. Definition of vertical deflection in Annex A to EN 1990 is shown in Figure 4.1

wc

wmax

w1

w2 w3

wtot

wc : precamber in the unloaded structural member

w1 : Initial part of the deflection under permanent loads of the relevant combination of actions

w2 : Long-term part of the deflection under permanent loads, not to be considered for single storey steel buildings,

w3 : Additional part of the deflection due to the variable actions of the relevant combination of actions

wtot = w1 + w2 + w3

wmax : Remaining total deflection taking into account the precamber

Figure 4.1 Definition of vertical deflections


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Table 4.1 Recommended limiting values for vertical deflections

Deflection limits Country Structure

Wmax W3

Comments

France Roofs in general L/200 L/250

Roofs frequently carrying personnel other than for maintenance

L/200 L/300

Roofs supporting plaster or other brittle toppings or non-flexible parts

L/250 L/350

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

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

Roofs in general L/300(*) -

Roofs with access only for maintenance

L/250(*)

Spain

The values to the left are given in the national technical document for steel structures [4] and in the Technical Building Code [5] and should be used if nothing else is agreed with the client.

Sweden There are no binding restrictions.

UK Roofs with access for maintenance

- L/200 There are no national deflection limits. The figures presented are taken from industry guidance [6].

Roofs accessible to personnel other than for maintenance

- L/360

(*) This values refers to w2 + w3 but w2 = 0 for steel structures.

4.2 Ultimate limit state: Ponding Where the roof slope is less than 5%, additional calculations should be made to check that collapse cannot occur due to the weight of water :

either collected in pools which may be formed due to the deflection of structural members or roofing material,

or retained by snow.

These additional checks should be based on the combinations at the Ultimate Limit States.

Precambering of beams may reduce the likelihood of rainwater collecting in pools, provided that rainwater outlets are appropriately located.


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5. References 1 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

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 NCCI: Practical deflection limits for single storey buildings

Reference(s)

ORIGINAL DOCUMENT

Name Company Date

Created by Alain BUREAU CTICM

Technical content checked by Jean-Pierre Pescatore CTICM

Editorial content checked by

Technical content endorsed by the following STEEL Partners:

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

Resource approved by Technical Coordinator

G W Owens SCI 08/6/06

TRANSLATED DOCUMENT

This Translation made and checked by:

Translated resource approved by:


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SN035a-En-EU_NCCI- Practical Deflection Limits for Single Storey Buildings

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