Table Of ContentComposite reinforced concrete
Composite
reinforced
concrete
R.TAYLOR
BSc, DIC, MICE, MIStructE
Senior Lecturer in Civil Engineering
University of Manchester
Simon Engineering Laboratories
Thomas Telford Limited, London, 1979
Published by Thomas Telford Limited, Telford House, PO Box 101,
26-34 Old Street, London EC1P 1JH
ISBN: 0 7277 0077 4
© R. Taylor, 1979
All rights, including translation, reserved. Except for fair copying,
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Division, Institution of Civil Engineers, PO Box 101, 26-34 Old
Street, London EC1P 1JH
Typeset and printed by Henry Ling Limited, Dorchester
FOREWORD
There is no doubt that none of the major structural materials is ideal.
Despite the long-standing use of various combinations of steel and
concrete, all methods of combining these materials have some draw
backs. While ordinary reinforced concrete combines the use of the
tensile strength of steel with the compressive strength of concrete, it
cannot take full advantage of high tensile steels because of the limited
capacity of concrete to undergo tensile strain without excessive crack
ing. Although this problem is overcome in prestressed concrete, the
economy resulting from the use of ultra-high strength steels is offset by
the costly prestressing operation, at least for site construction. The
other main traditional steel—concrete combination — composite con
struction — has undoubted advantages in construction but is extravagant
in its use of steel.
It would be advantageous if the economic use of ultra high strength
tensile steel could be combined with the convenience of composite
construction. While composite reinforced concrete does not completely
achieve this ideal, it goes some way towards it.
The Author of this monograph, Mr R. Taylor, has developed his pro
posals for composite reinforced concrete as a result of pursuing two
other lines of research. The first arose from the aim of improving the
efficiency of the use of steel in composite construction by incorporating
deep haunches in the beams without sacrificing constructional advan
tages. In the second investigation, Mr Taylor sought a means of
improving the exploitation of reinforced concrete beyond the limits
currently recommended by Codes of Practice. As a result of these two
investigations, it was realized that the incorporation of deep haunches
in composite beams could be achieved alongside the use of high tensile
reinforcement to give a possible improvement in overall economy.
It is hardly likely that innovatory methods of construction will be
accepted unless they show distinct advantages. Composite reinforced
concrete may well have such advantages in multi-storey structures when
it is desired to use precast flooring units in conjunction with an in situ
concrete frame in which the beams need to be of minimum construc
tional depth.
The present monograph is published with the intention of stimulating
practical exploration of this proposed method of construction. Con
siderable theoretical economies are possible; the realization of these
economies in practice could lead to major steps forward in the more
economic exploitation of steel—concrete composite construction.
M. R. Home
Manchester
March 1979
PREFACE
This research monograph on composite reinforced concrete is based on
lectures given at a research seminar in April 1979 at the Simon
Engineering Laboratories of the University of Manchester. At this stage
composite reinforced concrete is only a research material and has not
been used in practice. Indeed hitherto it has not been possible to use
composite reinforced concrete as there has been insufficient information
available to the designer. It was the purpose of the seminar, and is the
purpose of this monograph, to make available the information that has
been obtained at the University of Manchester from research over a
period of several years, and also to indicate those areas in which more
information is still needed.
Although aimed essentially at engineers concerned with research in
concrete structures, a wide cross-section of engineers from industry also
attended the seminar. Such varying backgrounds of the participants of
the seminar determined the material presented and its manner of presen
tation. It could not be assumed, for example, that each had a good
knowledge of reinforced concrete design and the requirements of CP 110,
nor that each had a good knowledge of composite construction and the
requirements of CP 117. For this reason somewhat fuller explanations
are given than would normally be the case in a research report.
Chapter 1 introduces the idea of composite reinforced concrete and
presents examples of design for the case of simply supported beams.
Chapter 2 discusses the problem of continuity and gives examples of
design of continuous beams. Chapter 3 covers the problems of vertical
and horizontal shear and the design of the shear connections. Chapter 4
discusses some miscellaneous problems such as deflexion, cracking,
fatigue and fire resistance.
CONTENTS
Chapter 1. Simply supported beams 1
Background
Composite reinforced concrete
Experimental data for flexure
Calculation of ultimate resistance moment
Comparative designs
Chapter 2. Problems of continuity 31
Compressive strength of concrete contained by channel
Tests on some 'hogging type' beams
Calculation of ultimate hogging resistance moment
Design of continuous beams
Constructional aspects
Chapter 3, Problems of shear 67
Effects of vertical shear
Problem of horizontal shear
Alternative types of shear connectors
Longitudinal shearing
Chapter 4. Miscellaneous problems 92
Problem of deflexion
Cracks at the service load
Problem of fatigue
Problem of fire resistance
Summary and conclusions 109
Appendix 1. Calculations for the comparative designs in chapter 1 111
Appendix 2. Calculations of hogging resistance moments of
test beams 115
CHAPTER 1
Simply supported beams
The combination of steel and concrete for structural purposes normally
falls into one of the traditional categories, such as reinforced concrete,
prestressed concrete and composite construction. These are quite well
defined categories but it is not unknown for the boundaries to be
crossed and prestressed reinforced concrete (or partially prestressed
concrete) and prestressed composite construction are examples of steel-
concrete combinations where the traditional boundaries have been
crossed. All these various modes of construction have their advantages
and disadvantages which determine their use in practice.
It will be suggested that a new combination of steel and concrete
combines many of the advantages of the traditional forms whilst
eliminating some of their attendant disadvantages. Nevertheless it is
emphasized that this new material, designated composite reinforced
concrete, is not suggested as a replacement of the traditional forms, but
merely as an additional and alternative form to be used in appropriate
circumstances. It is considered that composite reinforced concrete will
be found to be most suitable for the multi-storey framed structure.
Starting with a consideration of costs, it is shown that the traditional
forms for concrete structures leave something to be desired. It will be
shown for example that, although reinforced concrete is very efficient
in its use of materials, one could reduce the cost of the basic materials
by introducing a new philosophy of design. Moreover the constructional
advantages of composite construction over fully in situ reinforced con
crete are shown to be negated by the extra cost of the materials and also
the cost of the shear connectors. These relative advantages and disad
vantages of the traditional forms are shown to lead to composite
reinforced concrete.
