RATIONAL USE OF FIRED CLAY BRICKS COMPARATIVE STUDY BETWEEN LOAD-BEARING & CONCRETE SKELETON STRUCTURES

Microsoft Word - Document1LOAD-BEARING & CONCRETE SKELETON STRUCTURES
OF MASTER OF SCIENCE IN BUILDING TECHNOLOGY
BY
NOVEMBER 2003
Dedicated to My Parents , Brothers and Sisters My Wife Nagwa and My Children Mohamed, Samah , Samar , Ethar and Israa. Those who are in the operation holes to those who are holding the gun lock in all sites. To the Martyr who sacrifice themselves for the sake of the Religion and the Homeland.
ACKNOWLEDGEMENT
I wish to express my sincere gratitude and appreciation to my Supervisors
Dr. Ahmed Mustafa Mohammed , Dr. Abdullahi Ibrahim Fadl and Dr.
Mohammed Hussein Hamid for their help and guidance which
contributed immeasurably to this work.
I am indebited to the Director of the Building and Road Research Institute
(BRRI) and the Staff for their encouragement and rewarding discussions. Special thanks are due to the Technical Staff of BRRI for their help in carrying out the laboratory work. The skill and patience of Mrs. Rafaa Ramzi who typed this dissertation is greatly appreciated.
Finally I wish to express my gratitude and thanks to the Director of Soba University Hospital, and the Staff of Maintenance Department for unfailing support and moral encouragement throughout the period of this work.
ABSTRACT
Most buildings in Northern Sudan have been constructed as loadbearing structures. In
recent years reinforced concrete skeleton is widely used in big towns and cities.
Machine made fired clay bricks are mainly used as facing skin for aesthetic and
maintenance free purposes. Can machine made bricks, when used as loadbearing
structures, be an alternative to reinforced concrete skeletons? The answer to this
question, is the main objective of this study. This dissertation attempted to cover the
following aspects:
including techniques used in the existing loadbearing structures
in Sudan, advantage and disadvantage of brickwork, physical
and mechanical properties of brickwork materials such as
bricks (ordinary and machine) and mortars.
(ii) Determination of the characteristic compressive strength of
brickwork using prism tests and some other methods according
to some of the codes of practice together with factors affecting
the compressive strength of brickwork and loadbearing
capacity of brickwork.
(iii) Experimental works, which included tests on the BRRI bricks,
mortars, prisms and the results were used in the calculations of
the characteristic compressive strength of brickwork used in the
design of the loadbearing structures.
(iv) Adoption of an existing apartment building and determination
of the number of floors, which can be supported using BRRI
Soba Factory Bricks.
(v) Design the adopted building as a loadbearing structure, and
redesign it as a reinforced concrete skeleton.
(vi) Estimation of the costs of the two types of structures applying a
suitable costing method and comparing the results for the two
structures with respect to the total values, types and quantities
of materials used, and the savings in the strategic material such
as steel reinforcement and cement. The significance of the
conclusions from these results were discussed.
(vii) The study showed clearly that machine made brick of Soba
plant can be used as loadbearing up to five storey building and
its cost is less than that for reinforced concrete frame building
systems.

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Table of Contents Page Abstract i Acknowledgement v Table of Contents vi List of Tables x List of Plates xii List of Drawings xiii List of Appendices xiv Notations xv
1 Introduction 1 1.1 General 1 1.2 Objective 2 1.3 Scope 2
2 Brickwork Overview 5
2.1 General 5 2.2 Traditional Techniques of Earth Construction 7 2.2.1 Cob Techniques 7 2.2.2 Adobe Technique 7 2.2.3 Gishra Technique 8 2.3 Traditional Fired Clay Bricks Walling 8 2.3.1
Walls Built in Safaya Mortar 8
2.3.2 Walls Built in Cement Sand Mortar 8 2.3.3 Walls Built in Lime Mortar 9 2.4 Advantage and disadvantage of Brickwork 10 2.4.1 General 10 2.4.2 Advantage 10 2.4.3 Disadvantage 14 2.5 Fired Clay Bricks (Technical Specification) 16 2.5.1 General 16 2.5.2 Types of Bricks 16 2.5.3 General Situation of bricks Production 17 2.5.4 Methods of Production 18 2.5.5 Properties of Bricks 23 2.6 Mortars 26 2.6.1 General 26 2.6.2 General Types of Mortars 27 2.6.3 Factor Affecting Mortars Strength 28
2.6.4 General Properties of Mortars and Their Effect on Brickwork
29
2.7 Strength of Brickwork 31 2.7.1 General 31 2.7.2 Effect of Brick and Mortar Strengths 31 2.7.3 Effect of Brick Shape 32 2.7.4 Effect of Thickness of the Mortar and
Brick Height 32
2.7.5 Effect of initial rate of Absorption of Bricks and Water Retentivity of Mortar
33
2.7.6 Effect of Ageing 33 2.7.7 Effect of Patterns and Method of Bonding 34 2.7.8 Effect of Variation in Dimensions of Bricks 34 2.7.9 Effect of Eccentricity of Loading and
Slenderness Ratio. 34
2.7.10 Effect of Small Cross-Sectional Area 35 2.7.11 Effect of Workmanship 35 2.8 Assessment of Characteristic Strength of Brickwork 39 2.8.1 Prisms Tests as a Measure of Brickwork
Strength 39
2.8.2 Assessment of Characteristics Strength of Brickwork Units and Prisms
42
44
Loadbearing Capacity of Brickwork 49
2.8.6 Increase in permissible Stress in Members Subjected to Concentrated Loads
51
53
53
2.8.9 Column Formed by Openings 56 2.9 Previous Research Work and Studies on the Use of
Fired Clay Bricks in Loadbearing Walls 58
2.9.1 Comparative Study on the Rational Use of Fired Clay Brick in Building in Khartoum
58
62
3. Experimental Work 64 3.1 Introduction 64 3.2 Characterization of Bricks 64 3.3 Mortar Tests 65 3.4 Characteristic Compressive Strength of Prisms
and Brickwork 65
3.4.1 Compressive strength of prisms 65 3.4.2 Calculation of characteristic compressive strength
of prisms and brickwork 65
3.5 Compressive Strength of Short Peirs 67 3.5.1 The Loadbearing Capacity of the Peirs 67 3.6 Discussion of the Results 69 3.6.1 Bricks 69 3.6.2 Mortar 69 3.6.3 Brickwork, Prism and Peirs 70 3.7 Conclusions 71
4. Loadbearing Design 73 4.1 Introduction 73 4.2 Design Information 76 4.3 Loading 77 4.3.1 Section Loads 79 4.3.2 Bending Moment and Shear Forces 79 4.4 Design of Slabs 79 4.5 Design of Beams 79 4.6 Design of Stair Case 80 4.7 Design of Load Bearing Walls 80 4.8 Construction Detail Consideration 81 5 Reinforced Concrete Skeleton Design 84 5.1 Introduction 84 5.2 Design Information 85 5.3 Loading 85 5.3.1 Section Loads 86 5.3.2 Bending Moment and Shear Forces 88 5.4 Design of Slabs 88
5.5 Design of Beams 88 5.6 Design of Columns 89 5.7 Design of Stair Case 90 5.8 Design of Concrete Wall 91
6 The Comparison of Costs 92
6.1 Introduction 92 6.2 The Accounting Systems 92 6.2.1 Conceptual and Preliminary Estimates 94 6.2.2 Detailed Estimates 94 6.2.3 Choice of Accounting System 94 6.3 Types of Detailed Estimate 95 6.3.1 Fair Cost Estimate 95 6.3.2 Contractors Bid Estimate 95 6.3.3 Definitive Estimates 96 6.4 Choice of Estimating Method 97 6.5 Estimates of the Construction Costs 97
6.5.1 Components of the Structures for Cost Estimating 98 6.5.2
Breakdown of Unit Rate Estimate 99
6.6 Total Estimated Costs 100 6.6.1 Results 100 6.6.2 Analysis of the Results 100 6.6.3 Discussion of the Analysis of Results 101
7 Conclusions and Recommendations 102 7.1 Conclusions 102 7.2 Recommendations 103
References 105
Tables 107
Plates 126
Drawings 130
Appendices 137
List of Tables
Page 2.1 Annual brick production in Northern Sudan 1994 107 2.2 Dimensional Tolerance (Bricks) According to BS
3921/65 107
107
2.4 Compressive Strength and Absorption of bricks to both B3921/65 and MSS/No/6/1990
108
2.5 Mortar Designation. According to BS/5628-1978 108 2.6 Aspect ratio (H/T) Correction Factors for Compressive
Strength in accordance with AS/1640-1974 109
2.7 Sample size Factor for Characteristic Strength. According to BS 5628-1978
109
2.8 Characteristic Compressive Strength of Brickwork According to BS 5628- 1978.
109
2.9 Partial Factors of Safety on Materials as Specified by BS 5628 –1978.
109
2.10 Effective Height in Accordance with BS 5628-1978 109 2.11 Effective Length in Accordance with BS 5628-1978 109 2.12 The Appropriate Stiffness Factor “k” . According to
BS5628-1978. 110
2.13 Capacity reduction Factor β According to BS5628-1978 111 2.14 Reduction Factor (Ka,Ke) for Slenderness Ratio and a
uniform eccentricity of Force as Prescribed by AS 1640- 1974.
111
112
2.16 The Effective Height of Column in Accordance with BS 5628/1978.
112
2.17 Quantities and Their Cost of the Reinforced Concrete Skeleton and the Loadbearing Walls Structures , Egypt 1975.
112
113
3.2 Water Absorption of Machine Bricks 113 3.3 Compressive Strength of Machine Bricks 113 3.4 Efflorescence of Machine Bricks 114 3.5 Sieve Analysis of Sand Used for Mortar Preparation 115 3.6 Grades of Sand. According to BS 882-1973 115
3.7 Physical Properties of Cement. According to BS 12/1978 116 3.8 Compressive Strength of Mortar Cubes 116 3.9 Compressive Strength of Prisms 117 Page 3.10 Compressive Strength of Peirs (1.0m high) 117 3.11 Compressive Strength of Peirs (1.5m high) 118 3.12 Design Loads. According to BS 5628-1978 119 3.13 Comparison between the Loadbearing Capacity
Calculated Using Different Methods 120
4.1 Design and parameter informations 121 6.1 Bill of Quantities of Loadbearing 122 6.2 Bill of Quantities of Reinforced Concrete Skeleton 123 6.3 Quantities and Their Costs of Reinforced Concrete
Skeleton and the loadbearing Walls Structures. 124
6.4 Quantities of main materials 125 6.5 Saving in Materials for the loadbearing Structure 125 6.6 Saving in Materials for the Reinforced Concrete
Skeleton. 125
Page
3.1 Constructed Piers covered with polythin sheets as a curing. 126
3.2 BRRI crushing machine and the piers after failure. 127
3.3 Piers after release of loads and the cracking on both sides. 128
3.4 Splitting failure of Piers. 129
List of Drawings
Page 4.1 Plan arrangement showing the grid notation and selected 130
sections for loadbearing structure. 4.2 Arrangement of Reinforced steel for the whole slab of load- 131
bearing structure. 4.3 Plan of designed walls of load-bearing structure. 132 5.1 Plan arrangement showing the grid notation and selected 133
sections for reinforced concrete skeleton 5.2 Arrangement of reinforced steel for the whole slab of
reinforced concrete skeleton. 134 5.3 Beams detail 135 5.4 Columns detail 136
Appendix
(i) Load Bearing Structure Appendix (A) Bending moments and Shear Forces Calculation 137 Appendix (B)
Design of Selected Slabs 145 Design of Beams 154 Design of Stair Case 155
Appendix (C) Design of Selected Walls and Piers 157
(ii) Concrete Skeleton Structure Appendix (D) Bending Moments and Shear Forces Calculation 169 Appendix (E) Design of Selected Slabs 177 Appendix (F) Design of Beams 186 Appendix (G) Design of Selected Columns 209 Design of Reinforced Concrete Wall 225 (iii) Calculations Appendix (H) Calculations of Reinforcements Bars 226 Breakdown of Rate Estimates 228
Abstract and Calculation of Quantities 231
Notations A Cross-sectional area Ag Gross-sectional area As Area of Tensile Reinforcement Asc Area of Compressive Reinforcement b Major axis of column C Mean of Sample DL Dead Load d Effective depth to tensile reinforcement e Eccentricity ea Additional Eccentricity due to deflection in wall. eI Eccentricity at bottom of wall et Total design eccentricity at approx. mid-height ex Eccentricity at top of wall f Reduction Factor fcu Characteristic compressive strength of reinforced concrete fk,fm Characteristic compressive strength of masonry fp Characteristic compressive strength of prism fy Characteristic tensile strength of steel fy1 Characteristic Strength of Mild Steel fyv Characteristic Strength of Shear Reinforcement GK Characteristic DL GQ Characteristic LL H Average height of prisms hb Height of bearing relative to the lower support Kci Aspect ratio correction factor k Sample Size Factor ka Capacity Reduction Factor ke Capacity Reduction Factor L Length LL Live Load Lx Length of span in short direction Ly Length of Span in long direction N Design vertical axial load n Axial Load Per unit length of wall nw Design vertical load per unit length of wall PL Point Load R Group Range S Standard Deviation of Sample SR Slenderness ratio
Su Spacing of link reinforcement T Average thickness of prisms Tw Standard thickness of wall t Thickness of wall, minor axis of column tef Effective thickness of wall UDL Uniformly distributed load
V Shear Force Wm Unit weight of machine brick wall Wt Unit weight of traditional brick wall w Total unfactered load wx Load in short span wy Load in long span x Mean of Sample β Capacity Reduction Factor γf Partial Safety Factor For Load γm Partial Safety Factor for Material
CHAPTER ONE
1.1 General:-
Brick is a universal building material however, there is a tendency to use
brick masonry more as cladding and in-fill material rather than as
structural material. A large proportion of brickwork buildings for
residential and other purposes is satisfactorily designed and built in
accordance with empirical rules and practices without the need for special
structural consideration . However, the limits of this approach can not be
extended much beyond the scale of two storey houses of conventional
construction without having to resort to very thick walls, which in turn
result in waste of materials and other disadvantages. However in old
conventional practice, the thickness of brickwork is decided on the basis
of storey height without relating it to the load it has to withstand. The
economic success of brickwork construction has been achieved not only
by the rationalization of structural design, but also because it is possible
for the walls which comprise a brick building structure to perform several
functions, such as thermal and a accaustic insulation, fire and weather
protection as well as sub-division of space. As a building material it is
relatively cheap and durable, can provide virtually infinite flexibility in
plan form and offer an attractive external appearance. Furthermore
brickwork buildings can be constructed without heavy capital expenditure
on the part of the builder.
Recent studies have established brick as structural material. It has been
established that brick masonry can be designed as a loadbearing structural
element in conjunction with other structural parts of the building such as
floors, beams and columns. To make the best use of the inherent
advantages of brickwork, it is necessary to apply its construction in cases
where the accommodation gives rise to moderate or small floor spans,
and where it is possible to continue the loadbearing walls uninterrupted
from foundation to roof.
In the Sudan it is now generally accepted that brickwork forms an
attractive, durable cladding with good thermal and accaustic insulation,
excellent fire resistance, etc; but it is not so widely appreciated as an
economical structural material that can often be built faster more simple
than its main rivals steel and concrete, for multi-storey structures.
1.2 Objective of the Dissertation:-
The overall objective of this study is to work out the loadbearing capacity
of brickwork built from locally produced machine made bricks and then
to prove that it can be used in multi-storey apartment buildings by
determining the number of floors it can carry.
It is also attempted to compare the cost of such type of construction with
concrete frame structure apartment buildings of the same plan form and
number of storey high.
Broadly the scope is of three folds:-
a) Establish the loadbearing capacity of brickwork built of
machine made bricks of Soba Brick Factory of the Building
and Road Research Institute – University of Khartoum
(BRRI- U. of Kh.)
parameters resulted from (a) above as a loadbearing
structure.
c) Design the same a apartment building as a concrete frame
structure of the same storey high. .
d) Compare the cost of the two types of construction method in
relation to the overall cost of the buildings and their
component cost of the various materials, labour etc.
The methodology of the study is as follows:-
(i) Characterization of BRRI bricks in order to study their
physical and mechanical properties such as
dimensions, compressive strength, absorption,
(ii) Study of compatible mortar to be used, which include
study of materials such as sand, cement, and its cube
compressive strength.
of brickwork by means of crushing test carried out on
prisms of bricks. The prisms are constructed, cured,
and tested as specified by Australian Standard
AS/1640/1974.
using the above obtained characteristic strength.
(v) Construction of two types of short piers in order to
verify the results obtained by prism tests, namely
compressive strength, loadbearing capacity and the
mode of failure.
accordance with the function of the building and to
provide lateral strength and rigidity and to ensure that
the building is generally robust.
(vii) Determination of number of floors that such type of
bricks can carry according to the results of strength
obtained from brickwork tests, the loading
characteristic of an apartment loadbearing building,
logical thickness of walls and environment considered
(viii) Redesign of the same building with the number of
floors but as a reinforced concrete frame building.
(ix) Calculation and comparison of the two types of
construction in relation to overall cost, materials,
labour construction time…etc.
CHAPTER TWO
BRICKWORK OVERVIEW
2.1 General The use of earth as a building material is an old practice in Sudan. For wall
construction, the people use different traditional techniques such as cob (jalous),
adobe blocks, wattle and daub and gishra. Mud house is one of the earliest types of
construction known in Sudan. Traditional earth building techniques were developed in
various regions of the country to suit the available materials and the climatic
conditions. In Southern Sudan, Wattle and daub methods of construction are
promoted by the availability of timber and also by the continuous rain almost
throughout the year. In northern Sudan, the weather is dry hence cob and adobe
blocks are extensively used. Traditional buildings are noted for their simplicity,
utilization of local materials and good thermal insulation. However, they deteriorate
easily and require periodic maintenance. The annual expenditure on maintenance
sometimes outweighs all the economy achieved in the initial cost of the building.
Fired clay bricks are an important development of earth construction. The produced
bricks are more durable, since they withstand action of rain, and still have the good
properties of earth building of good thermal insulation, good fire resistance etc.
Fired clay bricks are extensively used in Sudan. The annual consumption of fired clay
bricks is estimated to be about 2.8 billion bricks per annum(1). Such extensive use
necessitate scientific exploration of the great potential that brickwork and other earth
building could offer to ever-growing building industry.
This chapter attempts to cover the following aspects:-
a) Brief information about the traditional techniques of earth
construction (Cob, adope, gishra) and the traditional fired clay brick
walling in Sudan.
c) Technical specification of rational fired clay bricks and machine
made bricks such as general situation of production in Sudan,
method of production, physical and mechanical properties of bricks
as reported in previous studies.
d) General information about mortars, which includes, general types,
factors affecting mortar strength, general properties of mortar and
their effect on brickwork.
e) Strength of brickwork, which includes effect of brick and mortar
strengths on brickwork strength , assessment of characteristic
strength using prism tests as a measure of brickwork strength and
factor affecting the prism tests.
f) Calculation of characteristic strength and permissible compressive
strength of brickwork and units using formulae and equations
according to BS 5628/1978 and AS 1640-1974.
g) Factors affecting the permissible stress such as eccentricity, small
cross-sectional area and slenderness ratio.
h) The loadbearing capacity of brickwork calculations according to AS
1640-1974 and BS 5628-1978.
i) Permissible compressive force in columns, the effect of slenderness
ratio, eccentricity on them.
j) Previous research work and studies on the use of fired clay bricks in
loadbearing walls which include comparative study on the rational
use of fired clay bricks in building, comparative study between
loadbearing and reinforced concrete skeleton buildings.
2.2 Traditional Techniques of Earth Construction
2.2.1 Cob Technique
Most of the soils used are light, grey, sandy…