InterfaceEngineering

Publications is aCo-Construct

initiativesupported by

Services Integrationwith Concrete Buildings

Guidance for a defect-free interface

By Roderic Bunn, Deryk Simpson and Stephen White

What is Co-Construct?Co-Construct is a network of five leading construction research and informationorganisations - Concrete Society, BSRIA, CIRIA, TRADA and SCI - who areworking together to produce a single point of communication for constructionprofessionals.

BSRIA covers all aspects of mechanical and electrical services in buildings,including heating, air conditioning, and ventilation. Its services to industry includeinformation, collaborative research, consultancy, testing and certification. It also hasa worldwide market research and intelligence group, and offers hire calibration andsale of instruments to the industry.

The Construction Industry Research and Information Association (CIRIA )works with the construction industry to develop and implement best practice,leading to better performance. CIRIA's independence and wide membership basemakes it uniquely placed to bring together all parties with an interest in improvingperformance.

The Concrete Society is renowned for providing impartial information andtechnical reports on concrete specification and best practice. The Society operatesan independent advisory service and offers networking through its regions andclubs.

The Steel Construction Institute (SCI) is an independent, international, member-based organisation with a mission to develop and promote the effective use of steelin construction. SCI promotes best practice through a wide range of trainingcourses, publications, and a members advisory service. It also provides internet-based information resources.

TRADA provides timber information, research and consultancy for theconstruction industry. The fully confidential range of expert services extends fromstrategic planning and market analysis through to product development, technicaladvice, training and publications.

For more information on Co-Construct visit www.construction.co.uk.

Services Integration with Concrete BuildingsCopyright of all material in this publication rests with The Concrete Society andBSRIA. Guidance appearing in the green text boxes is copyright The ConcreteSociety Ltd, while all guidance in blue text boxes is copyright BSRIA. Case studymaterial was kindly supplied by Max Fordham LLP. Additional input was providedby John Clarke and Richard Day and Neil Crook from The Concrete Society, IanHaining from Costain and John Payne from Edmund Nuttal.

Photographs and illustrations in this publication were provided by BSRIA and TheConcrete Society unless otherwise credited.

Cover Illustration: The concrete barrel-vault moulding process for the SASBuilding, showing chilled water pipework fitted to steel re-enforcement prior tothe concrete pour. Copyright Max Fordham LLP.

This publication was part-funded by the Department of Trade and Industry underthe Partners In Innovation (PII) collaborative research programme. The viewsexpressed in this publication are not necessarily those of the DTI. Final editorialcontrol and publishing responsibility of this publication rested with BSRIA.

©BSRIA/The Concrete Society IEP3/2004 May 2004 ISBN 0 86022 639 5 Printed by Multiplex Medway Ltd

All rights reserved. No part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or by any means electronic or mechanicalincluding photocopying, recording or otherwise without prior written permission ofthe publisher.

1SERVICES INTEGRATION WITH CONCRETE BUILDINGS

IntroductionThe aim of this document is to provide designers with guidance on theprovision of both vertical and horizontal holes through concrete elements,both pre-formed and post-formed. The guidance given represents asound common-sense approach to the design and detailing of holes andopenings and should cover most eventualities.

This guide, the third in a series called Interface Engineering Publications,is designed to appeal to both structural and services design engineers.BSRIA and The Concrete Society have pooled their technical knowledgeto provide both professions with consistent, interlocking advice.

This advice is often based on material repackaged from existing BSRIAand Concrete Society guidance. Details of the original publications,relevant European and British Standards and other references for furtherreading are provided at the end of this publication.

A document such as this cannot cover all services to concrete interfacesthat may arise, and it is also dangerous to generalise when so manyinterfaces are specific to a particular context: the nature of the project, therelationship of the professional parties in the contract, and the clientrequirements for the building, which may be very particular.

In order to demonstrate how many of the key interfaces should behandled, the authors have used a recent project as a case study: Theconcrete-framed headquarters for the SAS Institute in Buckinghamshire.This project has been used to illustrate practical aspects of the moregeneric guidance on the integration of services with structure provided inthis publication.

Roderic Bunn, BSRIADeryk Simpson, The Concrete Society

May 2004

2 SERVICES INTEGRATION WITH CONCRETE BUILDINGS

Introduction 1

Early design issues 4The structural perspective 4

Project pre-planning 4Post-cut holes 4Structural surveys 5

The building services perspective 6Exposed concrete structures 6Active thermal storage 6Fixings and fittings 6Plantrooms and basements 7

Structural design 8Structural issues 8

Reinforced and pre-stressed concrete 8Methods of forming holes 8Shape of penetrations 8Hole locations in beams 9Hole size in beams 9Holes in pre-cast floor units 9Holes in beam and block floors 10Holes in reinforced concrete slabs 10Holes in steel composite decks 10Post-tensioned floors: pre-formed holes 10Post-tensioned floors: post-formed holes 12Pre-formed vertical holes in beams 12Pre-formed horizontal holes in beams 12Post-formed vertical holes in beams 14Post-formed horizontal holes in beams 14Installing boxes 14Embedded pipe services in concrete 15Ph

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3SERVICES INTEGRATION WITH CONCRETE BUILDINGS

How to use this guide

Standards for structural and services design

Further reading to support this guide

Glossary for terms and definitions

Advice about the services engineering requirementsof running mechanical and electrical services throughconcrete elements will be found in blue-tinted boxes.

Advice about the structural engineeringrequirements of running services through concreteelements will be found in green-tinted boxes.

Comments marked by � link to structuralengineering sections listed under also see.

Comments marked by � link to mechanicalengineering sections listed under also see.

Comments marked by denote a link common toboth specialisms.

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Links to services sectionsLinks to structural sectionsLinks to common sections

Key services watchpoints

� Essential mechanical engineeringmessages from the guide

Key structural watchpoints

� Essential structural messages fromthe guide

Also see

Services detailed design 16Detailed design issues 16

Services penetrating through concrete 16Reinforcing large openings 16

Externally-bonded fibre composites 18Near-surface mounted reinforcement 18

Below ground penetrations 18Testing pipework systems

Services fixings to concrete 20Fixing methods 20

Fixing to floor soffits 20In-situ flat slabs 20Voided construction 20Exposed rib construction 21

Integrated systems 24Principles of thermal storage 24

Active thermal storage: a case study 25Design issues 26Installation issues 26

RefurbishmentInteraction of services with structure 30

Limited storey height 30Creating openings in slabs 30Openings in beams and walls 31

Further reading and standards 32

Glossary 33

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4 SERVICES INTEGRATION WITH CONCRETE BUILDINGS

The need to cast or cut holes in a concrete element to allow for the passage of services is acommon requirement. For some interfaces the problems are easy to resolve, but others require moredesign expertise and greater involvement between structural and services engineers. For critical areas, likeexposed concrete finishes in occupied areas, engineers need to liaise very closely with the client, architectand installing contractors over the details to ensure a functional and aesthetically acceptable solution.

Early design issuesA clients’ guide to

Services and structural engineers need towork together very closely to ensure that thedecisions made by the structural engineer willsuit the building’s comfort requirements. Thereverse is also true, as the technicalrequirements of a particular services solutionmay dictate elements of the structural design.It is in the client’s interest to foster a closeworking relationship.

It is a common occurrence for holes to becast or cut into reinforced concrete elements,usually to allow for the passage of services.Wherever possible, the structure should bedesigned to include a service zone tominimise the need for holes for service runs.Even though this is a common situation facedby designers, guidance on the design anddetailing holes is limited. This guide aims tosatisfy that need.

Project pre-planningPre-planning is preferable to retrospectiveprovision of any holes or openings. Pre-planned holes or openings are those markedon the layout drawings. They have beendesigned into the structural configuration sothat the resulting stresses are distributed andthe structure is not compromised.

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The structural perspective

Circular holes are preferable as square andrectangular holes can induce stressconcentrations around their corners,increasing the risk of cracking. Whether thehole is formed in an element at the precastfactory or formed in-situ makes no difference.

There are three forms of pre-planned holes:� Holes that are cast at the point ofconstruction of the element and are left openready to receive services� services that are cast into the element andremain in position� areas within a concrete element that aredesignated for holes to be cut retrospectively.

Occasionally there may be a need for alarge hole in an element where standardguidance will not apply. It is not possible togive definitive guidance for such situationsbecause each case will be different.

When large holes are required, anexperienced structural engineer should be usedto assess the resulting capacity of the elementand to design any additional strengthening.

Post-cut holesRefurbishment, change of use or poorplanning presents other problems, notablywhen the need for new or extra services

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Figure 1: Even the simplestconcrete-framed building has awealth of integrated engineeringservices.

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5SERVICES INTEGRATION WITH CONCRETE BUILDINGS

Also see

Holes in precast floor units, page 9Structural design, page 12Table 1, page 17Services fixings to concrete, page 20Figures 14 and 15, page 19Figure 13, page 18

Standards on page 32

Further reading on page 32

Glossary on page 33

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Pre-planning is always preferableto retrospective provision of anyholes or openings

The location and size of a hole iscrucial to maintaining structuralintegrity

Circular holes are preferable assquare and rectangular holes caninduce stress concentrationsaround their corners, increasingthe risk of cracking

When large holes are required,structural engineers should assessthe resulting capacity of theelement and design any additionalstrengthening

Structural engineers shoulddetermine whether holes need tobe sealed against water, sound orfire penetration, and whetheradditional strengthening of thestructure is required

Key structural watchpoints

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requires additional holes to be cut in anexisting structure. Questions that need to beaddressed include:� Why is the hole required?� will the hole be cut through re-inforcementor prestressing strand?� does the hole and service interface need tobe sealed against water, sound or fire?� is the concrete element pre-stressed?� did the original design provide nominatedzones, free of reinforcing bars or stressedtendons, for services distribution?� what additional strengthening is required?� can the services be fixed directly to theconcrete or is a separate fixing needed?

Structural surveysBefore undertaking any work that involvescutting into an existing concrete structure(apart from minor fixings), it is important tounderstand the form of construction andhence how the operation may affect the safetyand performance of the structure.Reinforcement can be in both the top andbottom part of an element.

The location and orientation of steelreinforcing bars and prestressing strands canbe determined using a covermeter. Acovermeter is a simple, hand-held electro-magnetic device consisting of a search headand a control box. The head is moved acrossthe surface of the concrete and an audiblesignal or digital readout is used to locate theposition of the reinforcing bar. For moredetails see Concrete Society Technical Report54, Diagnosis of deterioration in concrete structures.

With composite decks the steel soffit willprobably impair the reading of a covermeter.However, as they are generally standarddetails, the location of reinforcing bar is less ofa problem. The location and size of the holeis, however, crucial to maintaining structuralintegrity.

Services engineering issues

Structural issues

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