Temporary Works Whats Changed Eur. Ing. Peter Pallett FDRATION - - PowerPoint PPT Presentation

East Anglia Construction Safety Group

21 April 2011

Temporary Works What’s Changed

• Eur. Ing. Peter Pallett

FÉDÉRATION EUROPÉENE D’ ASSOCIATIONS NATIONALES D’ INGÊNIEURS The EUR ING title delivered by FEANI is designed as a guarantee of competence for professional engineers in Europe. The EUR INGs are listed in the FEANI Register, a database maintained by the Secretariat General in Brussels. Currently over 29,700 European Engineers are listed in the register (October 2007). The European Commission, in a statement to the European Parliament, has recognized the FEANI Register and the EUR ING title as valuable tools for the recognition of national diplomas among member states. " The FEANI scheme is an excellent example of self- regulation by a profession at European level and it provides a model for other professional groups in the technical and scientific sector. The Commission considers that an engineer who has obtained the title of Eur Ing should not normally be required to undertake an adaptation period or sit an aptitude test. ( Directive 2005/36/EC .)"

Content Content

• 1. Introduction
• 1. Introduction
• 2. Changes 2009 - 2011

(a) Procedures (b) Falsew ork (c) Scaffolding

• 2. Changes 2009 - 2011

(a) Procedures (b) Falsew ork (c) Scaffolding

• 3. Changes in 2011

(a) Wind (b) Formw ork

• 3. Changes in 2011

(a) Wind (b) Formw ork

Part One - Introduction Part One - Introduction

“Temporary Works” “Temporary Works”

Definition:

Works undertaken during construction but not required to form part of the finally completed construction works. Includes the works to stabilise or protect an existing building or structure that are not intended to be permanent.

Cofferdams

Tow er Crane Bases

Support to Cabins over River Thames

Temporary Façade Retention Structures

RMD-Kwikform

Scaffolding

Harsco Infrastructure

Upper Forth Crossing - 2008

27,000 ton 1.2 km

Steel wall formwork - Housing

Hindhead Tunnel A3 November 2009

1 of 2

Leada-Acrow

Soffit Formwork and Falsework

Typical costs for a reinforced concrete frame

Item material labour % of cost & plant total

Concrete 15 % 8 % 23 % Reinforcement 14 % 6 % 20 % Formw ork and falsew ork 9 % 30 % 39 % Sundries etc 12 % 6 % 18 % Totals 50 % 50 % 100%

Source: Formwork - a guide to good practice

Part Tw o - Changes 2009 - 2011

(a) Reminder of The Law

and

TW Procedures

Part Tw o - Changes 2009 - 2011

(a) Reminder of The Law

and

TW Procedures

CDM 2007

Approved Code of Practice and the

CDM Regs 2007

Document L144 March 2007 124 pages

£15

Source: http://books.hse.gov.uk Tel: 01787 881 165

1 of 4

Construction (Design and Management) Regs 2007 Approved Code of Practice (ACOP) 104 : The design of temporary works, such as falsework, formwork and scaffolding, falls within the scope of the CDM 2007 Regs.. CDM co-ordinators have to take reasonable steps to ensure co-operation between permanent and temporary works designers, in particular to ensure that arrangements are in place to ensure that designs are compatible and that the permanent works can support any loadings from temporary works.

2 of 4

CDM Regs 2007 Industry Guidance for Designers

Published May 2007 (50 pages) (Available as free *.pdf from Construction Skills )

3 of 4

Guidance for Designers (CDM07/4) 2.6.8 Designers need to consider how the structure can be constructed, cleaned, maintained and

• decommissioned. This may involve:

checking that the overall design takes

full account of any temporary works needed,

no matter who is to develop those works. checking that consideration has been given to the availability of sufficient space and adequate ground support for large plant required to construct or maintain the structure.

4 of 4

BS 5975 : 2008

Code of practice for temporary w orks procedures and the permissible stress design of falsew ork

Chairman: Frank Marples

Permissible Stress

1 of 10 First published 1982

£270 Draft for Public Comment BS 5975:2008+A1:2011 Section 2 Procedures and 17.5.1 Wind

Typical Register used as Active Site Document

2 of 10

Appointment of Temporary Works Co-ordinator 7.3.1 The appointment of a temporary works co-ordinator (TWC) should be the first operation in a chain of events culminating in the construction of a Temporary Works scheme.

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NOTE: In large organisations the TWC may be proposed by a Contracts Director / manager or similar but the designated individual should be satisfied that the proposed TWC has the abilities outlined in 7.1.2 before confirming acceptance of the proposal. The TWC should be appointed by the designated individual of the main or principal contractor.

Source BS 5975:2008+A1:2011

7.1.2 It is essential for the TWC to be competent and have relevant up-to-date training and both qualifications and the experience appropriate to the complexity of the project.

BS 5975:2008 Clause 7.2.5

Activities of the Temporary Works Coordinator

c) ensure that a design brief is prepared with full consultation, is adequate, and is in accord with the actual situation on site; d) ensure that any residual risks, (assumed construction methods or loading constraints) are included; e) ensure a satisfactory temporary works design is carried out; f) ensure that a design check is carried out by someone not involved in original design - for concept, structural adequacy and brief compliance; n) after a final check, which is satisfactory, ensure a permit to load is issued by either the TWC or TWS;

• ) when it has been confirmed that the permanent structure

has attained adequate strength, ensure a permit to dismantle is issued by either the TWC or TWS;

4 of 10 ( Source BS 5975:2008+A1:2011 )

Typical letter

• f appointment
• f a TWC

On larger sites the appointment of a Temporary Works Supervisor is also recommended

5 of 10

Appointment of Temporary Works Supervisor 7.3.1 On larger sites or where site manager or project manager considers it necessary, or where there are one or more subcontractors carrying out temporary works operations, or where the TWC requests assistance, one or more TWS’s may be appointed. The TWS should be appointed by the designated individual of the organisation for whose work the TWS is responsible.

Source BS 5975:2008+A1:2011 6 of 10

Appointment of Temporary Works Supervisor 6.4.5 Contractors carrying out a number of small contracts may appoint a TWC with overall responsibility and a TWS, with an appropriate level of authority for each individual site. 7.3.2 It is essential for the TWSs to be competent and to have relevant up-to-date training and both qualifications and the experience appropriate to the operations for which they are responsible.

Source BS 5975:2008+A1:2011 7 of 10

BS 5975:2008 Design Check Categories

Category Scope Independence

2

More complex design. by individual not excavations, structural involved in design steelwork, foundations, and not consulted by top restrained etc. the TW designer

3

Complex or by another innovative design organisation

1

Simple design ( falsework top restraint is NOT assumed ) by another member

• f design team

Restricted to standard solutions

O

Site issue - by another member of site team

• r design team

8 of 10

Typical Permit to Load

9 of 10

10 of 10

Part Tw o - Changes 2009 – 2011

(b) Falsew ork

Part Tw o - Changes 2009 – 2011

(b) Falsew ork

Any temporary structure used to support a permanent structure w hile it is not self-supporting.

RMD- Kwikform

Support of Twin wall and Precast soffit

BS EN 12812: 2008

Falsew ork

Published January 2011

Limit State Design

£170

Chairman: Frank Marples

1 of 4

BS EN 12812: 2008

Design classes for falsework Dimensional limitations and generally restricts application to building work. Structural performance is derived from pre-existing knowledge of the performance of the components of the structure, such as props etc..

Class A

Such information is often included in standard solutions.

Source NA.4

Class B

Falsework where a complete design is

• undertaken. There are two sub-classes.

2 of 4

Design classes for falsework

Class A Class B1 Class B2

3 of 4

Simplified design in BS EN 12812 and/or in accordance with relevant EuroCodes Slab area < 0.3 m² (ie 300mm) Beams < 0.5 m² Clear span < 6.0 m Height < 3.5 m (measured to underside

• f permanent works)

Design in accordance with relevant EuroCodes Most falsework in this class But there is a γm x 1.15

BS 5975 : 2008

Code of practice for temporary w orks procedures and the permissible stress design of falsew ork

First published 1982

Permissible Stress

£270

Chairman: Frank Marples

4 of 4

BS 5975:2008

New Loadings

• n Falsew ork

BS 5975:2008

New Loadings

• n Falsew ork

Construction Operations - Working Area Load

Allow for a Service Class 1 load of only 0.75 kN/m²

• ver the entire area, including access and working areas.

i.e. only 30mm extra concrete ! BS 5975 - The British Standard Heap - Cl 17.4.3.1

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Working Area Load

Working area Service Class 1 load 0.75 kN/m²

BS 5975 Clause 17.4.3.1

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Additional Transient In-situ Concrete Load

Working area Service Class 1 load 0.75 kN/m² In-situ concrete loading 0.75 kN/m² to 1.75 kN/m² 3m 3m Total load equal to 10% concrete load

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BS 5975 Clause 17.4.3.1

In-situ Concrete Construction Operations Loads

Summary

Thickness calcs Total Up to 300mm 0.75 + 0.75 1.50 kN/m2 Over 700mm 0.75 + 1.75 2.50 kN/m2 300 to 700mm 0.75 + 10% t 0.75 +

10% of weight

• f concrete

Slab thickness t

3 of 3

1 of 1

Permanent formwork minimum construction load of 1.50 kN/m2

Working Areas - Access for striking Wherever falsework requires removal of individual pieces, for example striking primary or secondary bearers, consideration should be given to a working platform about two metres below the underside of the permanent works. Where the formwork and falsework is handled in large areas, provision for access to make-up areas should be considered. ( Use Service Class 1 load - 0.75 kN/m2 )

1 of 2

BS 5975 Clause 19.1.1

Consider access underneath for striking

Tall frame structure

2 of 2

BS 5975:2008

The Four Design Checks for Falsew ork

BS 5975:2008

The Four Design Checks for Falsew ork

Falsew ork Analysis

It is recommended that for each falsew ork structure FOUR design checks be carried out:

Check ONE - on the STRUCTURAL STRENGTH

• f the individual members and their

connections to transmit the applied loads / forces;

Check TWO - on the LATERAL STABILITY

• f both individual members and the

structure as a w hole;

Check THREE - on the OVERALL STABILITY

• f the falsew ork structure;

Check FOUR - on POSITIONAL STABILITY to

ensure the falsew ork does not slide.

Source: BS 5975 Clause 19.4.1.1

THINK VERTICAL THINK HORIZONTAL

and then,

THINK HORIZONTAL AGAIN

and again, and again, and again.

BS 5975:2008 Check One

Structural Strength

BS 5975:2008 Check One

Structural Strength

BS EN 1065

Adjustable telescopic steel props

Published November 1999 Committee: CEN

£150.00

1 of 6

Class Max. Extension Characteristic strength A 25 2.50 m 20.40 kN A 30 3.00 m 17.00 kN A 35 3.50 m 14.60 kN A 40 4.00 m 12.80 kN B 25 2.50 m 27.20 kN B 30 3.00 m 22.70 kN B 35 3.50 m 19.40 kN B 40 4.00 m 17.00 kN B 45 4.50 m 15.10 kN B 50 5.00 m 13.60 kN B 55 5.50 m 12.40 kN C 25 2.50 m 40.80 kN C 30 3.00 m 34.00 kN C 35 3.50 m 29.10 kN C 40 4.00 m 25.50 kN C 45 4.50 m 22.70 kN C 50 5.00 m 20.40 kN C 55 5.50 m 18.60 kN D 25 to D55 2.50m to 5.50m 34.00 kN E 25 to E55 2.50m to 5.50m 51.00 kN

BS EN 1065

Props to have minimum of 1.0m adjustment, and not to be intentionally dis-engaged

2 of 6

Characteristic strength is the value at w hich 95% of those tested w ill fail above value

(ie 5% w ill fail below value)

Characteristic strength is the value at w hich 95% of those tested w ill fail above value

(ie 5% w ill fail below value)

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Stellenbosch - South Africa - 2009

Removed TWO internal walls

200mm thick x 14m slab

4 of 6

Supplier claim 29.80kN characteristic load Thin walled props 3.2m (too short)

5 of 6

BS5975:2008 Safe Working Load - BS EN 1065 props erected 1o out-of-plumb with 10mm eccentricity of load

6 of 6

BS 5975:2008 Check Tw o

Lateral Stability

BS 5975:2008 Check Tw o

Lateral Stability

BS 5975 : Horizontal Disturbing Force Clause 19.2.9.1

At each phase of construction falsework should resist the applied vertical loads PLUS a horizontal disturbing force the greater of EITHER

2½ % W

OR the summation of wind force, erection tolerance ( 1% W) , concrete pressure force, water and wave forces, dynamic and impact forces, forces from the permanent works (e.g. stressing etc.) etc..

1 Of 2

Falsework’s horizontal disturbing force F H Design for minimum lateral stability load of 2½ % W Load W

• r

know n lateral loads PLUS 1%W

2 of 2 (BS 5975 : Clause 19.2.9.1 )

Load Case 1 - Erected but not concreted

Lateral Forces :- Maximum wind load plus Increases to at least 2% of known vertical loads if Class B2 1% known vertical loads (BS 5975 and Class B1)

Load Case 2 - While placing the permanent w ork / concrete

Lateral Forces :- Working wind load plus Increases to 2% known vertical loads if Class B2 1% known vertical loads including full concrete load (BS 5975 and Class B1)

NOTE: If the structure is not connected to a permanent structure then the full wind load might need to be considered

• consult with the Temporary Works Designer (TWD )

UK BS 5975 load Case - Minimum stability

Horizontal disturbing force FH will be a minimum of 2½ % total vertical load including self weight, concrete, and full construction

• perations load

Top Restrained Load Case - connected to Permanent Works

Restraining force RH will be a minimum of:-

2½ % (vertical loads)

(BS 5975 and Class A)

• r

2 % (self weight) plus maximum wind (Class B2)

• r

2 % (vertical loads) plus working wind (Class B1 and B2)

NOTE: Although bracing is not shown, the structural strength still needs checking (Cat. 2) and bracing may be required to create effective nodes.

Conditions of use stated by supplier require top restraint

1 of 3

2 of 3

3 of 3 North Staffs PFI SGB GASS braced for 2½ % W

Or is it ?

Top restrained falsework

Lateral Stability of steel beams - Web stiffeners For structural steelwork at points of reaction or concentrated load, web stiffeners should be provided at ALL loading transfer points including supports, UNLESS calculations are provided to show that such stiffeners are not required.

Web stiffeners No Calculations

(BS 5975 : Annex J Clause J.1)

BS 5975:2008

Back propping flat slabs

BS 5975:2008

Back propping flat slabs

Falsew ork Formw ork Backpropping

European Concrete Building Project (ECBP) - 4th floor

1 of 1

Method One - One level of backpropping NEW Slab to be cast Falsework load (wp ) Supporting slab (1) Backprops (wb1 ) Lower slab (2)

Distribution of Applied Load using Rigid Props SLAB PROP

100% 100% 50% 50% 50%

Distribution of Applied Loads using Elastic Props SLAB PROP

100% 100%

70%

30% 30% This is 70% of the applied load and is in addition to the existing load on the slab With preloaded props to value Pp

• Pp

+ Pp + Pp

BS 5975 Cl 19.3.4 Table 20

Method One - Tw o levels of backpropping NEW Slab to be cast Falsework load (wp ) Supporting slab (1) Upper Backprops (wb1 ) Lower slab (2) Lower Backprops (wb2 ) Lower slab (3)

Distribution of Applied Loads using Rigid Props SLAB PROP

100% 100% 33% 67% 33% 33% 33%

Distribution of Applied Loads using Elastic Props SLAB PROP

100% 100%

65%

35% 23% 12% 12% With preloaded props to value Pp

• Pp

+ Pp + Pp + Pp This is 65% of the applied load and is in addition to the existing load on the slab

BS 5975 Cl 19.3.4 Table 20

Part Tw o - Changes since 2009

(c) Scaffolding

Part Tw o - Changes since 2009

(c) Scaffolding

Temporary construction, w hich is required to provide a safe place of w ork for the erection, maintenance, repair or demolition of buildings and other structures and for the necessary access

Harsco Infrastructure

BS EN 12811-1 : 2003

Part 1: Scaffolds - Performance requirements and general design

Published June 2004

£182.00

Chairman: CEN TC 53

“States BS 5973 withdrawn”

BS EN 12811-1

Introduces:- TWO Load Combinations : In Service Condition One platform with full imposed service load and the next above or below with 50% of service load Plus in absence of wind a lateral force of 0.3 kN / bay / working area Out of Service Condition Full wind load (BS EN 1991-1-4) and imposed Service Load limited to only 25% or 50%

NASC Guide for Scaffolding w ith tubes and fittings

TG20:08 Volume 1

November 2008

120 pages Authors: Dr M.H.R. Godley Eur Ing P.F. Pallett

Based on BS 5973 and updated to BS EN 12811-1 with simplified BS 6399 wind information Information for erection and use

• f standard scaffolds and

includes FOUR summary tables

• f safe heights for scaffolds

£135 + p&p Vol 1 & 2

Source : NASC

1 of 4

TG20:08 Volume 2

November 2008

128 pages

TECHNICAL DATA Information on weights and properties, additional wind info., worked examples, and method for height of unclad scaffolds. Safe Height tables for :- 3 tables fully loaded inside boards 3 tables part ledger braced scaffolds Fuller calculation method heights: 24 tables fully ledger braced 12 tables part ledger braced (alt. ties)

£135 + p&p Vol 1 & 2

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TG20:08 Supplement 1

February 2011

16 pages

Takes account of the Wind Code BS EN 1991-1- 4:2005 + A1:2010 using a simplified method to update the SAFE HEIGHT tables for Basic Scaffolds Incorporates Apprendix H for use of ties on UNCLAD scaffolds erected to open structures. Source : NASC

3 of 4

TG20:08 Overview TOOLBOX TALK

Published by National Access and Scaffolding Confederation in July 2009

Plus a FREE Powerpoint toolbox presentation from www.nasc.org.uk £2.50

Handy Pocket Sized booklet

Available from NASC

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SG4 : 10

Preventing Falls in Scaffolding

Published by National Access and Scaffolding Confederation with Foreword by HSE in December 2010

£25 60 pages

Available from NASC

1 of 5

SG4 : 10

No longer permitted to traverse along a platform (known as tunnelling method) Create “scaffolders safe zones” For scaffolds with 2m lifts use of Step-ups

Figure 39

2 of 5

Erection hop-up for next guardrail

Quick release connection

3 of 5

SG4 : 10

Introduces use of ‘Scaffolders Safe Zone’ Reaching below guardrail “clip-on”

Figure 9 Figure 12 4 of 5

SG4:You User Guide Preventing Falls in Scaffolding

Published by National Access and Scaffolding Confederation with Foreword by HSE

( 84pp January 2011)

Handy Pocket Sized booklet

£5

Available from NASC

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Designation of Scaffolds to TG20:08

EXAMPLE

3 – 5 - 1

Load Class 3

(General Purpose)

Number of boards between standards Number of inside boards ( 0, 1 or 2)

Inside boards assumed lightly loaded

F

Inside boards fully loaded I.e. Load Class

S

Special case with 1.8m bay length

TG20 Cl 4.2 page 19

BASIC Scaffolds to TG20 Guide to T&F Scaffolds Part Boarded Fully Boarded 2 m lifts with possible 2.7m pavement lifts Tied to the building façade: either at alternate lifts 4m

• r at every lift

Ledger bracing at alternate bays Façade bracing fitted every SIX bays but note: Plan bracing needed every FOUR lifts, and every twelve bays if façade braced across single bay

The controlling Table 1

Load Desigtion Activity Load M ax Max Class kN/m² Bay Boards

1

1 - 3 - 0 Inspection, v. light duty

0.75 2.7m 3

2

2 - 4 - 0 Light duty

1.50 2.4m 4

3

3 - 5 - 0 General purpose 2.00

2.1m 5

3 - 4 - 1 3 - 4 - 2 3 - 5 - 1 3 - 5 - 2 4 + 1 4 + 2 5 + 1 5 + 2

( inside boards are 0.75 )

4 - 4 - 1 4 - 4 - 2 4 - 5 - 1 4 - 5 - 2 4 + 1 4 + 2 5 + 1 5 + 2

4

4 - 5 - 0 Heavy Duty 3.00

1.8m 5 ( inside boards are 0.75 )

Source TG20:08 Vol. 1 Table 1 page 21

TG20 Figure 1 page 18

Typical independent tied scaffold

Tie assembly

Façade bracing every SIX bays - to top platform

Ledger bracing alternate bays

Ties shown at alternate lifts

Plan bracing NOT required Plan bracing NOT required

1 of 2

Tie assembly

Façade bracing every SIX bays - to top platform

2 of 2

Plan bracing REQUIRED between ties as façade brace is NOT between ledger braced frames H > 8m every FOUR lifts and every twelve bays

1 of 1

One transom at every lift within 300mm of ledger braced standards fitted with right angle or swivel fittings

Ledger bracing Tie assembly TG20 Cl. 10.2 (page 51)

ALL sheeted & debris netted - unclad over 15m

Part Three : Changes in 2011

(a) Wind (b) Formw ork

Part Three : Changes in 2011

(a) Wind (b) Formw ork

Part Three : Changes in 2011

(a) Temporary Works Wind

Part Three : Changes in 2011

(a) Temporary Works Wind

Status of Wind Codes in the UK BS 6399-2: 1997 Loading for buildings, Part 2: Code of practice for wind loads, was published in July 1997 TG20 (scaffolding) first published in 2005 a simplified method based on BS 6399-2 Supplement No. 1 uses BS EN 1991-1-4+A1 The European Code BS EN 1991-1-4:2005+A1:2010 was amended in March 2011 (£246) The UK National Application Document (£170) was also amended in March 2011 The Background Information PD 6688 (£182) to the Annex was published in December 2009

ALL British Standards superseded by European Standards were withdrawn on 31st March 2010

Wind in Temporary Works

Aim: same procedure in all temporary works Falsework - BS 5975:2008 +A1:2011 to introduce revised simplified method based on the UK NA to BS EN 1991-1-4 +A1 Scaffolding - TG20 Supplement No. 1 now issued Formwork - Revision will include the same method extended to suit climbing formwork. Duration of work

(assume less than two years)

Simplified method will use similar factors and town descriptions as existing for structures less than 50m with “orography” and less than 100m without “orography”.

Information needed by designer

Location of the site How far from the nearest sea? less than 0.1km, 2 km, 10 km or 100 km Is it in a town that extends more than 2 km from the site in all directions? Is the topography fairly flat around the site, or is it near the top of the hill, or part-way up ? What is the altitude of site?

(in metres above sea level)

Duration of work

(normally less than two years)

Is the falsework or the scaffold to be unclad, debris netted or sheeted?

Maximum wind pressure on falsework and formwork

2 wind T e, e p

S (z)c c 613 . 7 . q × × × =

qp is the peak wind pressure N/m² Swind is the wind factor for the site Ce(z)ce,T is combined exposure correction factor

Where Formula is for falsework erected less than TWO years

Source BS 5975:2008 +A1:2011 (Cl 17.5.1.3) and BS EN 12812 (Cl 8.2.4.1)

The wind factor Swind

⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + × × = 1000 A 1 T v S

wind map b, wind

Where vb,map is the fundamental wind velocity (in m/s) Twind is the topography factor allowing for whether site is on a hill, cliff or on the flat. A is the altitude of the site in metres above sea level.

1 of 8

Mean hourly wind speeds

BS 5975:2008 Figure 4

2 of 8

10 minute mean wind speeds vb,map

b,map NA to BS EN 1991-1-4

T w ind = Topographical factor depends

• n w hether the terrain around

the site is flat, moderately steep (1 : 5 ) or very steep (1 : 3 )

Structures without “orography” Twind = 1.00 (z < 100m)

BS 5975 Figure 5 (a)

3 of 8

Topography Factor Twind Skip wind

SEA

Definition of ‘sea’ from BS 6399

BS 5975:2008 Figure 7

4 of 8

TOWN

Built up areas

BS 5975:2008 Figure 6 (a)

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“TOWN”

Woodland areas

BS 5975:2008 Figure 6 (c)

6 of 8

COUNTRY You’ll like this one !

Country is all terrain which is not sea or town ! Less than 2km of built-up area around the site.

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COUNTRY

Built up areas

BS 5975:2008 Figure 6 (b)

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Part Three : Changes in 2011

(b) Formw ork

Part Three : Changes in 2011

(b) Formw ork

A structure, usually temporary, but in some cases w holly or partly permanent used to contain poured concrete to mould it to the required dimensions and support it until it is able to support itself. It consists primarily of the face contact material and the bearers that directly support the face contact material.

Published by The Concrete Society

Second Edition: June 1995

R e v i s e d d u e 2 1 1

Chairman: Peter Pallett

Skip to TWf

More emphasis on proprietary panel formw ork

More guidance on Soffit Formwork systems

New Sections on Climbing Formwork

Peri

Update on Permanent Formwork - e.g. Twin wall

1 of 2

2 of 2

Significant updates to sections on:- Surface finishes and tolerances to

BS EN 13670

“Execution of concrete structures” Striking and Curing

BS EN 1992-1-1:2004: Eurocode 2: Design of concrete

• structures. General rules and rules for buildings

does not cover surface finishes (replaces BS 8110) BS EN 13670: 2010 Execution of concrete structures. Includes informative guidance (£186 Feb 2010)

Annex F Table F.4 Types of surface finish Basic Finish Where no particular requirement needed Ordinary Finish Where not of visual importance. e.g. unseen areas such as lift shafts Plain Finish Visual effect of some importance e.g. Seen occasionally, direct painted etc. Special Finish Where special requirements needed. e.g. Where surface irregularity and colour are important.

Concrete Pressure envelope when placed from top

Max Dh

Pmax

Concrete stiffening

Pmax

Design formwork pressures for a range of new cements and self-compacting concretes

DTI Contract Ref: 39/3/739 CCC2399 September 2004 133 pages Quote: “ The findings indicate that the use of CIRIA R108 was conservative for the range of new concrete types for walls and columns. There appears to be no case for change from the existing UK approach to concrete pressure determination.” NOTE: The report is confidential and NOT available to the public. See article in “CONCRETE” March 2009

Concrete Groups and the values of C2

Group Concrete

C2

• 2. With any admixture except with retarding property 0.3

CEM I , SRPC, CEM II A with metakaolin / silica fume

1 of 2

Self-compacting - With any admixture except with 0.45 retarding properties. ALL cements except CEM III B & CEM IVB

• 5. With any admixture except with retarding property 0.45

CEM II A, CEM II B, CEM III A

3.

With admixtures that retard - CEM I (OPC), SRPC, 0.45 CEM I I A with metakaolin or with silica fume

4.

Without admixture - CEM II A, CEM II B, CEM III A 0.45

1.

Without admixture - CEM I (OPC) , SRPC, 0.3 CEM II A with metakaolin or with silica fume

A

basic

B

retarded

Concrete Groups and the values of C2

Group Concrete

C2 6.

With admixtures that retard

0.6

CEM II A, CEM II B and CEM III A

C

heavily retarded

7.

With or without admixtures

0.6

CEM III B and CEM IVB Self-compacting - With any admixture except with 0.6 retarding properties. CEM III B & CEM IVB Self-compacting - With retarding properties 0.6 ALL cements

2 of 2 Source: CIRIA R108 and March 2009 “CONCRETE”

2m 35 40 45 45 50 50 50 3m 40 45 50 55 60 70 75 10°C 4m 45 50 55 60 65 75 90 5m 45 55 60 60 70 80 100 6m 50 55 60 65 75 85 105 4m 30 35 45 45 50 65 85 20°C 5m 35 40 45 50 60 70 90 6m 35 40 45 50 60 70 90 Rate of Rise R in metres per hour 0.5 1.0 1.5 2.0 3.0 5.0 10.0 H

Table AA WALLS & BASES Pmax

max (kN/m²)

Basic Concrete Group A (1) CEM I (OPC)

• r

(2) CEM I with admixture 2m 40 45 50 50 50 50 50 3m 50 55 60 65 70 75 75 5 °C 4m 55 60 65 70 75 85 100 5m 65 65 70 75 80 95 110 6m 70 75 80 80 90 100 115 2m 30 35 40 45 50 50 50 3m 30 40 45 50 55 65 75 15°C 4m 35 45 50 50 60 70 90 5m 40 45 50 55 60 70 90 6m 40 45 50 55 65 75 95

PFP/002E page 8

increase 45 55 55 80 % = −

Table BB WALLS & BASES Pmax

max (kN/m²)

2m 40 45 50 50 50 50 50 3m 50 55 60 65 65 75 75 10°C 4m 55 60 65 70 75 85 100 5m 60 70 70 75 80 90 100 6m 65 75 75 80 85 95 115 4m 40 45 50 55 60 70 90 20°C 5m 40 45 50 55 65 75 95 6m 45 50 55 60 70 80 100 Rate of Rise R in metres per hour 0.5 1.0 1.5 2.0 3.0 5.0 10.0 H Retarded Concrete Group B (3) CEM I with retarder (4) Blend with <35% pfa

• r <65%ggbs

(5) Blend <35% pfa <65% ggbs with admixture 2m 50 50 50 50 50 50 50 3m 65 70 75 75 75 75 75 5°C 4m 75 80 85 90 95 100 100 5m 85 90 95 95 105 110 125 6m 95 100 100 105 110 120 135 2m 35 40 45 45 50 50 50 3m 40 45 50 55 60 70 75 15°C 4m 45 50 55 60 65 75 90 5m 50 55 60 65 70 80 100 6m 50 60 65 65 75 85 105

PFP/002E page 9

Sustainable Forests

Where timber is used in formwork, it is recommended that only material which is certified under the Forest Stewardship Council scheme should be used. This ensures that timber is sourced from FSC certified forests which are managed sustainably. There is a “Chain of Custody” which tracks the timber from forest to consumer. Source www.fsc.org

Safe Working Properties - Timber in Wall formwork

Source: Third Edition Formwork Guide ( PFP/009A page 4 of 18 )

Formwork to precast edge forms

Source: New Table 10 Formwork Guide (Third Edition)

Safe Working Properties - WALL Formwork

and finally and finally

T W f T W f

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• n unacceptable risks, recommend research

areas, watching brief on overseas issues

www.twforum.org.uk

Thank You

The End