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UNIVERSITI TEKNOLOGI MALAYSIA DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT
LIEW YU HAO
Author’s full name
:
Date of birth
:
12 DECEMBER 1985
Title
:
PERBANDINGAN KAEDAH REKABENTUK ELEMEN TIANG BERDASARKAN BS8110 – EUROCODE EUROCODE 2
“I hereby declare that I have read this project report and in my opinion this project 2008/2009 Academic Session:
report is sufficient in terms of scope and quality for the award of the Degree of I declare that this thesis is classified as :
CONFIDENTIAL
Bachelor in Civil Engineering” (Contains confidential information under the Official Secret Act 1972)*
RESTRICTED
(Contains restricted information as specified by the organisation where research was done)*
OPEN ACCESS
I agree that my thesis to be published as online open
ii
PERBANDINGAN KAEDAH REKABENTUK ELEMEN BERDASARKAN TIANG BERDASARKAN BS8110 – EUROCODE EUROCODE 2
LIEW YU HAO
A report submitted in partial fulfillment of the
iii
I declare that this project report entitled “PERBANDINGAN KAEDAH REKABENTUK ELEMEN TIANG BERDASARKAN BS8110 – EUROCODE EUROCODE 2
” is the result of my own research except as cited in the references. The report has not been accepted for any degree and is not concurrently submitted in candidature of any other degree.
iv
This study is especially dedicated to my beloved parents, supervisor, classmates, and all my friends for continuous support and care throughout my
studies….
v
ACKNOWLEDGEMENTS
First and foremost, I would like to express my sincere appreciation to my project supervisor, Ir Azhar Ahmad for his enthusiastic effort and concern. Without his continued support and interest, this thesis would not have been the same as presented in time here.
Beside that I would also like to thanks to t o the project panel team for the recommendation and comment. comment. With the comment and suggestion has improved improved the outcome of this project.
vi
ABSTRACT
The application of Eurocode (EC) getting popular around the world; this is due to the design by using EC are more economic and technically advanced. However the usages of EC in structural design are not as popular as expected in Malaysia. This is because perception and misunderstanding are still exists among the designers. Designers always think that there is not much difference while design using British Standard (BS) compared to EC. Furthermore, they claim that design by using EC is difficult and not easy to understand. Therefore, a study was conducted to review the design steps and also to explain technically on EC2 design on the column design. For a better understanding on EC2 design process, a works example of EC2 on column and comparison of area of reinforcement on several types of column has been done. In this research the scope of compare are only focus on area of reinforcement required with varies of dimension and loading. The result has indicated that although the design process of EC2 is more technical but it is easy to follow and understand.
vii
ABSTRAK
Pengaplikasian “Eurocode” “Eurocode” (EC) semakin popular di seluruh seluruh dunia. Ini kerana reka bentuk dengan menggunakan EC adalah lebih ekonomik dan lebih teknikal. Akan tetapi, penggunaan EC dalam reka bentuk struktur di Malaysia tidak begitu popular seperti yang dijangkakan. Ini kerana persepsi dan salah faham terhadap EC masih wujud di di antara pereka-pereka. pereka-pereka. Mereka sentiasa berpendapat berpendapat bahawa tiada banyak perbezaan mereka bentuk dengan menggunakan “British Standard”(BS) berbanding dengan EC . Tambahan pula, mereka mendakwa bahawa penggunaan EC dalam reka bentuk adalah sukar dan susah difahami. Oleh itu, suatu kajian telah dijalankan untuk mengkaji langkah-langkah mereka bentuk dan untuk menerangkan reka bentuk EC2 pada reka bentuk tiang dari segi s egi teknik. Untuk member pemahaman yang lebih jelas terhadap proses mereka bentuk EC2. Satu contoh kerja EC2 pada tiang dan perbandingan luas tetulang yang dihendaki atas beberapa jenis tiang tian g telah dilakukan. Dalam kajian ini, skop perbandingan hanya fokus kepada luas tetulang yang diperlukan dengan dimensi dan daya yang berbeza. Keputusan menunjukkan proses
viii
TABLE OF CONTENT
CHAPTER
TITLE
PAGE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENTS
iv
ABSTRACT
v
ABSTRAK
vi
ix
2
LITERATURE REVIEW
4
2.1
Introduction of Eurocode
4
2.1.1
National Annexes
6
2.1.2
Design life
7
2.2
Aims and Purposes of Eurocode
7
2.3
Eurocode 2
9
2.3.1
Basic Knowledge of Eurocode
9
2.3.2
Action on Structures
10
2.3.3
Load Arrangements
11
2.3.4
Combination of actions
13
2.3.5
Material Properties
14
2.4
Principle of Design
15
2.4.1
15
Structural Analysis
x
3
4
METHODOLOGY
38
3.1
Introduction
38
3.2
Sketching by using AutoCAD
41
3.4
Design method
41
RESULT AND ANALYSIS
43
4.1
Review of Eurocode 2 column design procedure
43
4.2
Comparison of design output
57
4.2.1
57
Comparison short column with various of column dimension
4.2.2
Comparison short column with
58
various of loading 4.2.3
Comparison slender column with
60
xi
LIST OF TABLE
TABLE NO.
TITLE
PAGES
2.1
The structural Eurocodes
5
2.2
Concrete related Eurocodes and their
6
equivalent current standards.
2 .3
Indicative design working life
7
(from UK NA to Eurocode)
2.4
Selected bulk density of material (From EC1, part 1-1 )
10
xii
2.11
Minimum column dimension axis distances
23
for columns with rectangular or circular section method A
2.12
Minimum dimension and axis distances
23
for reinforced concrete slabs.
2.13
Maximum bar size or spacing to limit crack width
26
2.14
Partial Factor for safety for loading (BS)
28
2.15
Combination of actions and load factors at ULS
29
(EC)
xiii
LIST OF FIGURES
Figure No.
Title
Page
2.1
Typical Eurocode Layout
7
2.2
Links between the Eurocodes
9
2 .3
Alternate Spans Loaded
11
2.4
Adjacent spans loaded
12
xiv
4.1
Comparison BS and EC with various of
46
Dimension
4.2
Comparison BS and EC with various of
47
Loading
4.3
Comparison BS and EC with various of
49
Dimension
4.4
Comparison BS and EC with various of Loading
50
xv
LIST OF ABBREVIATION
Qk
Characteristic value of a variable action
Qk1 (Q (Qki)
Characteristic value of a leading variable action (Characteristic value of an
A
ccompanying variable action)
Qk
Characteristic value of a variable action per unit length r area
q b
Basic wind pressure
q p
Peak wind pressure
γ
Partial factor
xvi
Gk,inf
Lower characteristic value of a permanent action
f c
Compressive strength of concrete
cd f cd
Design value of concrete compressive strength
f ctm ctm
Mean value of axial tensile strength of concrete
E cm cm
Secant modulus of elasticity of concrete
f t
Tensile strength of reinforcement
f t,k t,k
Characteristic tensile strength of reinforcement
f yk yk
Characteristic yield strength of reinforcement
εuk
Characteristic strain of reinforcement (or prestressing steel) at maximum load
F Ed Ed
Compressive force, designvalue of support reaction
μfi μfi
Ratio of the design axial load under fire conditions to the design resistance of the column at normal temperature but with an
xvii
LIST OF APPENDICES
APPENDIX
TITLE
PAGE
A
BS column design steps
67
B
Structural Analysis
69
C
Construction Plan (Front view)
71
D
Construction Plan (Side View)
72
1
CHAPTER 1
INTRODUCTION
1.1
Introduction
Code design is one of the basic and important tools for a structural designer. There are many existing codes for design are currently using all around the world, for examples, American code (most recently ACI318-02, and older version ACI318-99), Unified Arabic Code (UAC), Canadian Code (CSA-A23.3-94),
2 Eurocodes covering all the main structural materials.In this research the main concern is on column design. Column is one of the main structural where it is a primary compression member that carries and transfers the load from beams and slabs to the foundation. foundation. The code of practice practice for column based on British Standard is included under the BS8110-1:1997 while in Eurocodes is under Eurocode 2. BS 8110 is reinforced concrete design code used all around world since 1985, whereby EC2 was officially published on 2004. Lately Government of Malaysia has decided to fully implement the Eurocode design in 2010, therefore by knowing the different between this 2 standard will gives advantages to current engineer to be ready during changes in Year 2010.
1.2
Problem Statement
Even though government of Malaysia had decided to fully implement the
3 3. To compare column design output between British Britis h Standard design and Eurocode design.
1.4
Scope of study
This research will mainly focus on the method of the design of British Standard and Eurocode on the building column. In order to achieve the objective of the research, there are a few research scopes are necessary to be revised and followed, such as: i)
Design is focused on the reinforced concrete biaxial column which included necessary check, design process and material selection.
ii)
Procedure differences of British standard and Eurocodes design on RC columns.
iii)
Compare the area of reinforcement required, As req of the design desi gn by using EC2 and BS8110.
4
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction Introductio n of Eurocode
In future, the usage of EC will getting common and in 2010 Malaysia are planning to replace the BS 8110 with EC2. Since 1901, 1901, British Standard had developed throughout the year and currently British standard has covers all the design parameters and and design consideration. For example:
5 Table 2.1: The structural Eurocodes
Where all concrete designs are assign under Eurocode 2 (EC2) where EC2 is abbreviation for BS EN 1992, Eurocode 2: Design of concrete structures. Where the EN 1992 included four parts: EN 1992-1-1
:
Common Rules for Building and Civil Engineering Structures.
6 Table 2.2: Concrete related Eurocodes and their equivalent current standards.
According to The Concrete Centre ™, during the implementation period user are recommended to consider the existing standard when the required European
7 2.1.2
Design life
The structural working life or design life is the very basic step of RC design to assume the suitable working life of the building structure. Hence it is necessary to be determining the durability requirement for design of of reinforced concrete structures during the building process. Therefore in Eurocode, the design life is under Eurocode: Basic of Basic of Structural Design. The Design. The UK National Annex (NA) to Eurocode presents UK values for design life; these are given in Table 2.3. [8]
Table 2.3 : Indicative design working life (from UK NA to Eurocode)
8 (including such aspects of Essential Requirement n°4 Safet y in use, which relate to mechanical resistance and stability) and a part of Essential Requirement n°2 Safety in case of fire, including durability.
II) Determine the performance of structural components and kits with regard to mechanical resistance and stability and resistance to fire, insofar as it is part of the information accompanying CE marking (e.g. declared values).
III) Provide common design criteria and methods to fulfill the specified requirements for mechanical resistance, stability and resistance to fire, including aspects of durability and economy between owners, operators and users, designers, contractors and manufacturers of construction products.
IV) Facilitate the marketing and use of materials and constituent products, the
9 2.3
Eurocode 2
2.3.1
Basic Knowledge of Eurocode
In order to start design based on Eurocode2 , there are some basic principles should be clarify such as the philosophy of design codes which is In EN 1992-1-1 only explained the the basic of different phenomena phenomena (e.g. bending, shear, bond) bond) where as in BS are tend explained in the types of members (e.g. beam, slabs, columns).
In addition, knowing the relationship or the roles of each eurocodes is important too. Hence figure 2.2 has been included in the research.
10 2.3.2
Action on Structures Structures
After knowing basic knowledge of the Eurocode, the next steps is to design the structural, action on structures or load and imposed deformations we cal l it in current practices has to be determine. According on Eurocode 1: actions on structures consists of 10 parts that gives detail of a wide variety of action. Further information on the action of structural can be found in Eurocode in Eurocode 1 Part 1-1 Genera; actions Densities, self weight, imposed loads for building gives gives the necessary information of building materials as Table 2.4
Table 2.4 : Selected bulk density density of material material (from EC1, part 1-1 )
11 * Again it is advised that existing standards st andards are considered for use where European standards have not yet been issued.[8]
2.3.3
Load Arrangements Arrangements
Load arrangements are basically refer to the arranging of variable action such as dead, imposed and wind loads. Where by these arrangements of variable of actions give the most critical load in a member or structured are described in the Eurocode 2 and its UK NA. For building structures, the UK NA to Eurocode Eurocode 2, part 1-1 allows any of the following sets of load arrangements to be used for both the ultimate limit state and serviceability limit state.[8]
In Eurcode 2, there are 3 phenomena of load arrangement such as:
12
Or
Figure 2.4 : Adjacent spans loaded
Any two adjacent spans carrying the design variable and permanent loads with other spans loaded with only the design permanent load as above Figure 2.2.
The value of γG should be the same throughout.[8]
II)
Load set 2: All or alternate span loaded
13 Generally, this type of arrangement will be used for beams and slabs in the UK as it requires three load arrangements to be considered, while load set 1 will often require more than three arrangements to be assessed.
II)
Load set 3: Simplified arrangements for slabs
Eurocode 2 allow this type of load arrangements can be simplified f or slabs where it is only necessary to consider the all spans loaded arrangement as Figure 2.3, provided the following conditions conditions are met:
In a one-way spanning slab the area of each bay exceeds 30 m 2 (a bay means a strip across the full width of a structure bounded on the other sides by lines of support).
The ratio of the variable actions (Q ( Qk) to the permanent actions (G ( Gk) does not exceed 1.25
The magnitude of the variable actions excluding partitions does not exceed 5 KN/m2.
14 2.3.5
Material Properties Properties
During the design of structure, knowing the concrete properties and steel properties are rather important. In Eurocode 2 the design of of reinforced concrete is based on the characteristic cylinder strength rather than cube strength and it specified according to BS 8500: Concrete – Concrete – complementary complementary British Standard to BS EN 206 – 17 (e.g. for class C28/35 concrete the cylinder strength i s 28 MPa, whereas the cube strength is 35 MPa). Typical concrete properties are given in Table 5. Concrete up to class C90/105 can be designed using Eurocode 2. For classes above C50/60, however, there are additional rules and variations.[8]
Table 2.6 : Selected concrete properties based on Table 3.1 of EC2, Part 1-1.
15 Table 2.7 : Characteristic tensile properties of reinforcement
2.4
Principle of Design
2.4.1
Structural Analysis
16 depth to neutral axis). Regardless of the method of analysis used, the following principles apply:
Where a beam or slab is monolithic with its supports, the critical design hogging moment may be taken as that at the face of the support, but should not be taken as less than 0.65 times the full fixed end moment.
Where a beam or slab is continuous over a support that may be considered not to provide rotational restraint, the moment calculated at the centre line of the support may be reduced by ( F Ed,sup /8), where F where F Ed,sup Ed,sup t /8), Ed,sup is the support reaction and t is the width of the support.
For the design of columns the elastic moments from the frame action should be used without any redistribution. [8] Table 2.8 : Bending moment and shear co-efficients for beams
17 2.4.2
Minimum concrete cover design
The nominal cover can express in such as a way: Cnom = Cmin + ∆ cdev Cmin should be set to satisfy the requirements below:
Safe transmission of bond forces
(see 2.4.2.1)
Durability
(see 2.4.2.2)
Fire resistance
(see 2.4.2.3)
Where ∆ cdev is an allowance has to should be made during during design for deviations from the minimum cover. It should be taken as 10 mm, unless fabrication (i .e. construction) is subjected to a quality assurance system, in which case it is permitted to reduce ∆ cdev to 5 mm.[8]
2.4.2.1
Minimum cover for safe transmission of bond forces
18 minimum concrete cover and maximum cement content for various elements in a structure based on the types of exposure of element. [8] Table 2.9 : Exposure classes
19 Table 2.10 : Selected recommendation for normal-weight reinforced concrete quality
for combined exposure classes and cover reinforcement for a t least a 50 years intended-working life and 20mm maximum aggregate size.
2.4.2.3 Design for fire resistance
According to Eurocode 2 Part 1 – 2: 2: Structural fire design, design, gives several methods to determining the fire resistance of concrete elements; detail guidance are not covered in this research where that be obtained from specialist literature. Design
20
There are three standard fire exposure conditions that fire resistant design should be met R Mechanical resistance for load bearing E Integrity of separation I Insulation
Tables 2.11 and 2.12 given the minimum dimensions for columns and slabs to meet the above conditions. The tables offer more flexibil ity than BS 8110 in that there are options available to the designer e.g. e. g. section sizes can be reduced by
21 Tables 2.12 : Minimum dimension and axis distances for reinforced concrete slabs.
2.4.3
Stability and imperfections imperfections
The effects of geometric imperfections are a re considered in combination with the effects of wind loads (i.e. not as an alternative load combination). For global analysis, the imperfections may be represented by an inclination
θi .
22 In most cases, an allowance for imperfections is made in the partial factors used in the design of elements. However for columns, the effect of imperfections, which is similar in principle to the above.
2.4.4
Crack control
Members subject to bending generally exhibit a series of distributed flexural cracks, even at working loads. These cracks are unobtrusive and harmless unless the width becomes excessive. Therefore the crack widths should be limited to ensure appearance and durability is satisfactory. satisfactor y. In the absence of specific durability requirements (e.g. water tightness) the crack widths may be limited to 0.3 mm in all exposure classes under the quasi-permanent combination. In the absence of requirements for appearance, this limit may be relaxed (to say 0.4 mm) for exposure classes X0 and XC1 (refer to Table 2.9). The theoretical size of the crack can be
23
Figure 2.8 : Determination of steel stress for crack width control
24 2.4.5
Design of Moment
Column sections should be designed axial load N and , in each direction, design moments as follows : M = (Mo+Mi)+ M2 ≥ Ne0,
eo = h/30 ≥20 mm
Where, M0 is the first order moment obtained by elastic analysis of the structure. M1 is an additional first order moment resulting from the imperfections, M2 is a nominal second order moment resulting from deflection.
Note: In Eurocode, M0 is used to represent the total first order moment including the effect of imperfections. The approach adopted here is more s ensible when using the following equation for M 0e. In braced columns, differing first order end moment and M 01 and M02 maybe replaced by an equivalent moment :
25 K Ψ = Creep effect factor derived from K Ψ = (1+βΨef )
β = (0.35 + f ck ck /200 -λ/150) Ψef = effective creep ration = Ψ(∞,t0) x (M0qp/M0)
M0qp = first quasi-permanent load combination.
2.4.6
Biaxial bending checking
As first steps, a separate se parate design each principal direction may ma y be made, ignoring biaxial bending. Imperfections need to be considered only in the direction where they have to more unfavourable effect. No further checking is needed if the following two conditions conditions are satisfied : (a)
0.5 λy ≤ λx ≤ 2λy ,
where λx and λy = slenderness ratio
(b)
Mx/h is either ≤ 0.2My/b or 5 M y/b.
26 2.5
Procedure of design of column based on EC2
In general axial loads and first order moments are assumed to be available. The designs consider slenderness in order to determine design moments, M moments, M Ed Ed. The columns are designed and checked for biaxial bending. The effects of allowing for imperfections are illustrated. [9] The general method of designing columns based on Eurocode is as follows: 1. Determine design life.
2. Assess actions on the column.
3. Determine which combinations of actions apply.
27 10. Check spacing of bars and links.
2.6
Comparison of Column design procedure of BS 110 and EC2
A comparison between the EC2 and BS braced column design processes is shown in the flowcharts below.
28
29 2.6.1
Loading and moments
British Standard
Eurocode
Where the Load combination for the ultimate states from above are based on the table below :[
Factor for safety for loading (BS) Table 2.14 : Partial Factor
30 2.6.2
Column classification and failure modes
According to BS8110 a column classified as short when both l ex /h and l ey ex /h and ey /b are: Less than 15
(braced column)
Less than 10
(unbraced column)
Where lex and ley are the effective heights that related to the XX and YY axis ; h is the overall depth of the section in the plane of bending bending about XX axis, meaning that h is dimension perpendicular to the XX axis.
The effective Height are obtain by equation below: l e=β l o, Where, l o is the clear distance between of column end restrains.
β is a coefficient which depends on the degree of end restrains as specified in table 2.16 [2]
31 Where
l o is the effective height of the column i is the radius of gyration about about the axis considered I is the second moment of area of the section about the axis A is the cross-sectional area of the column
In additional, l o is the height of a theoretical column of equivalent section but pinned at the both ends. This depends depends on the degree of fixity at each end of the columnm which itself depends on the relative stiffness of the columns and beams connected to either end of the column under consideration.
Hence, EC2 gives 2 two general formulae for calculating the effe ctive height : For braced members :
…………………………………….
Eqn (1)
32 The stiffness can also formulate as below ,
By assuming typical column in a a symmetrical frame with spans approximately equal length as figure 2.9
Figure 2.9
33 Finally, the slenderness ratios are required to compare with the limiting slenderness ratio. This limit is given by:
λlim= 20 X A X B X C/
where :
∅) B= (1 + 2 )
A = 1/(1+0.2
ef
C=1.7-r C=1.7-r m
∅
ef
= effectiv creep ratio
w = Asf yd yd/(Acf cd cd) (if not known B can be taken as 1.1) f yd yd = the design yield strength of the reinforcement f cd cd = the design compressive stregth of the concrete As = the total area of logistudinal reinforcement n = NEd/(Acf cd cd) NEd = the design ultimate axial load in the column
34 2.6.3
Reinforcement Reinforcement details
In this topic will talk about the differences of BS8110 and EC2 on reinforcement detailing. Firstly, the differ in minimum and maximum area for longitudinal steel :
In BS 8110,
Minimum area,
I)
100A s/Acol must not be less than 0.4
II)
100As/Acol must not be greater than 6.0 in vertically cast column.
Or, 100As/Acol, must not greater than 8.0 in a horizontally cast column. But at laps 100As/Acol, must not greater than 10.0 for both types of columns.[2]
35 Secondly the differences of Links design,
In BS 8110,
I) Maximum spacing = 12 x size of the smallest compression bar II) The links should be arrange so that ever y corner bar and alternate bar or group in an outer layer layer of longitudinal steel is supported by a link passing round the bar and having an included angle not greater than 135°[2]
In EC2,
I) Maximum spacing should not exceed the lesser of 20 x size of the smallest compression bar or the least lateral dimension of the column or 400 mm. This spacing should be reduced by a factor of 0.60 a) For a distance equal to the larger lateral dimension of the column above and below or slab, and b) At lapped joints of longitudinal longitudinal bars > 14mm diameter
38
CHAPTER 3
RESEARCH METHODOLOGY
3.1
Introduction
In this chapter will mainly explain about the method and the process that will go through in order to fulfill the objective of the research. As explained earlier, this research is mainly about the code different between Eurocode and British standard
39 The research was then continuing with design by using British Standard 8110 . Where the initials design will start with the frame analysis of the structure to determine the load and moment occurred on the typical column, for a four fl oors office plan manually. The calculations by done done by excel to avoid repetitive work to be done. Necessary check such as the shear resistance, moment resistance, fire resistance and deflection check will conducted conducted manually , and cross section of the RC column will be draw will the number reinforced bar.
The design process was then continuing with design by Eurocode 2, basically most of the steps are almost similar just the partial factor are difference from each other. Further detail could refer to Chapter 2: 2.6 Comparison of Column design based on BS 8110 and EC2. Necessary check will be conduct and cross section of RC column will be drawn.
After obtaining the Eurocode design and British standard design, comparison
40 For a better understanding a flow chart has been drawn to show the process of research
START – Preliminary Research (Internet)
IDENTIFY –
Problem Statement and
REVIEWING -
DESIGN –
Literature Review
Column Design by using BS 8110 and EC2
RESULT AND
REPORTING -
DISCCUSION-
Report the result and finding in
Compare the outcome and the
the research project.
41 3.2
Sketching by using AutoCAD
Autocad had been very important tools in design tool now in construction field nowadays. This is due to user friendly drawing command and interface that allow the user to draw the construction plan in a short period. Nowadays many design software had cooperate with AutoCAD and allow the output of AutoCAD (DWG files) to be import to proceed to the design purpose. In this research, the
AutoCAD uses to drawn the four floors office‟s architect plan and also structural plan in order to give clearer picture on the design plan
3.3
Design method
Excel a very common and handy tool to formulated calculations and logic flows. Excel also provides user friendly interface and function to the user in mathematical problem. Furthermore excel also help increase the speed of calculation
42
Determine design lifeRefer to table 2.1 EN 1990:
Assess the action on the column – Clause 6.2.2 EN1991-1-1 or Local NA or UK NA
Determine the critical combination of action Refer to table A1.1& A1.2 (B) EN1990
Assess the durability requirement and the concrete strength-
Check cover requirement for corresponding fire resistance period
Determine cover for fire, durability and bond Refer to Cl 4.4..1, EN 1992-1-1 1992-1-1
43
CHAPTER 4
RESULT AND ANALYSIS
In this chapter, the result and analysis of the research will . The objective that had achieve in this research were outlined the different of Eurocode 2 and BS 8110, the column design example of EC2 based on a real construction case and also compared the outcome of the of BS design and EC2 design.
44 Before begin the construction, the selection of material are one of the important element. In EC2 the reinforced bar strength are suppose to takes t he value 500MPA or 500kN/mm 2 which having higher strength than reinforced bar under BS8110 But due to the common reinforced bar in Malaysia was 460MPa, so in this paper the value taken as 460 MPa. Due to the project are belong small scales construction concrete C30/37, and the common high strength steel bar f y y = 460MPA or 460 kN/mm 2 will be use as the main reinforcement reinf orcement and also f y=250MPA will be use as the link for column design. In fact the rei nforced bar strength in EC2 are suppose to take the value 500MPA or 500kN/mm 2 which having higher strength than reinforced bar under BS8110. . But due to the reinforced in Malaysia are always taking as 460MPA, so in this paper the strength are going to consider is 460 MPA The detail of material selection on EC2 can be found in Concise Eurocode 2, Chapter 3: Material.
The design was then continue with design the checking cover requirement for corresponding fire resistance period. The design of cover in EC2 is much more
45 After decided the minimum cover and suitable dimension of column width, analysis structure will be conducted. The purpose of have structure anal ysis is to obtain the design moment and axial load. The details of structural analysis are not interest in this research. However, the analysis is taken from previous analysis that had been done by using British standard approach. In the analysis a most critic al situation will be selected to conduct the design. In such case column A/1 has been selected and axial force and a nd maximum moment has calculated with combination analysis value from frame, 1/A-D and A/1-6. .The analysis result had attached in appendix as a reference.
Determining slenderness of a column is the initial step in column design. It is important to know that in British standard approach X-X axis has change to Z-Z axis. In EC2 in order to determine the slenderness a s pecify column the upper limit on the slender ratio have to determine first then compare with the actual slenderness ratio. The used of upper limit is to determine the necessity of considering the second order effect. While determine limiting slenderness ratio several factor have to consider for
46
coefficients, Ψef as and Mechanical Mechanical reinforcement ratio, ω. In additional the selected column also assume experienced biaxial forces, which is the most common case happen in the construction. In order to determine the design moment, EC2 suggested to takes the maximum value out of 3 different of moment combination. The details of design can be found in Concise EC2, Chapter 5:5.6.2(Design of bending moment).
The design process was then continue to find area of reinforcement required in order sustain the design moment and axial load. In EC2, d 2/h need to be found before refer to the Concise EC2 Chapter 15.9.3 (Column Chart) to find the area of reinforcement. Whereby d2 is equal to Cnom + ф/2+фlink . Unlike in BS 8110, d/h, d is is equal to h- ф/2+фlink . In addition, the As min and Asmax in EC2 were different from BS8110. Where Asmin =Max (0.1Ned/f yd yd ; 0.002Ac), Asmax=0.04Ac outside laps and 0.08Ac at laps. After decided the number of reinforcement, checking of biax ial bending should be be done , where the detail of calculation can be found on Concise on Concise EC2 Chapter 15.9.4 (Biaxial bending) and bending) and also BS also BS EN 1992-1-1:2004 1992-1-1:2004 Section 5: 5.8.9 Biaxial Bending). Lastly, to determine the link size there are 3 situations need
47
Practise of EC2 on a real construction project
A plan has been attached to explain the construction situation I)Determine I)Determine design life This project is categories under (Building and common structures) Hence, Design life
=
50
year
II) Assess the durability requirement and the concrete strength Concrete, The concrete class that has been selected are class C30/37 , fck fck,cube acc
= = =
30 37 1
MPA MPA (Under all phenomena) phenomena)
48
III)Check cover requirement for fire resistance period (90mins) To design a suitable cover required for fire resistance. Type of method have ro be determine first. First order eccentrcirty, eccentrcirty, Proposed column dimension, di mension, e = Med/Ned = 0.15b = 0.15*h = 0.25b = 0.25*h = Hence, Chose Method B w = 1 n = 1 Minumun dimension column width /axis distance distance a of main main bar
600 173.99 105 175
* mm
700
(conservative value) (conservative value) =
IV)Determine cover cover for fire, durability and bond
500/50
OK!
49
V)Analyse structure for critical combination moments and axial forces In this research the detail detail of structure analysis was not the main concern. The value of structure has taken from the previous calculation. calculation. The design will only conduct according to the higher value of momentand shear member . Which is happened on the column A/1
Moment, Z-Z direction From frame 1/(A-D),(MAX MIN MAX) Mzmaxtop = 123.3 kNm Mzmaxbtm = 0.5*Maxtop y-y direction From frame A/(1-6), (MAX MIN MAX) Mymaxtop = 48.54 kNm Mymaxbtm 0.5*Maxtop
=
61.65
kNm
24.27
kNm
50
VI)Check Slenderness and determine design moments.
For a braced column the minimun limiting value of λ Ned fck fyk fcd
= = = =
λlim
= =
Braced Members
Z - Z axis
708.7 30 460 fcu/1.5
KN
=
20
26.2/(Ned/Acfcd)^0.5 90.2007 (Conservative Eq. for braced column)
51
Y-Y Axis
Column Size Icolumn Acol
= = =
600 1.7E+10 420000
x mm^4 mm2
700 4
lcol
=
3.8
Beam Size
=
300
x
400
lbeam
=
8
Ibeam Abeam
= =
1.6E+09 120000
mm^4 mm2
Icol/lcol
=
4513158 (Eq
52
Find design moment
h
=
700
b = 600
where
,
w
=
Asfyd/(Acfyd)
= nu
=
1 1+w
(conservative design, w=1) =
2
53
Z-Z Direction
M₀₂zz
=
123.3
KNm
M₀₁zz =
61.7
KNm
Determine Design Moment (Clauses 5.8.8.2 EC2 : Design of Concrete)
Medz Where
₁ e₀ Ned Ned
e e₀
= = = =
₀₂ ₀
₂ ₀₁
Max [ M , M ed + M , M + 0.5M ]
₂
₀
l /400 max( h/30 ; 20 ) 16.53633 KNm
= =
( 5.8.8.2) 0 0
54
Y-Y Direction
M₀₂yy
=
48.54
M₀₁yy
=
24.3
Determine Design Moment (Clauses 5.8.8.2 EC2 : Design of Concrete) Medy = Max [ M , M ed + M , M + 0.5M ]
₀₂ ₀
Where
₁ e₀ Ned Ned
e e₀
= = =
₂ ₀₁ l₀/400
₂
max(b/30 ; 20 ) 14.174
= =
( 5.8.8.2) 0 0
55
Find As by using charts
₂ d₂/h d
=
Cnom + ф/2+фlink
=
0.086
= = =
0.056 136.27 0.015
=
60
Use figure 15.5, Ned/bhfck Med Med/bh^2fck
From Figure , Asfyk/bhfck
=
0
Use Asmin = 0.002Ac Chose Section :
As
=
840.00
4H32 Asprov=
Check for Biaxial Bending
3220
56
•Check whether (Medz/Mrdz)^a + (Medy/Mrdy)^a (Medy/Mrdy)^a ≤ 1.0 and
Find
Interpolating the value of Med/bh^2fck from fig 15.5 By using, Asfy/bhfck = 0.118 Ned/bh^2fck = 0.056 Med/bh^2fck
=
0.04
Med=Mrz=Mry
=
352.8
a Nrd fcd fyd hence, Nrd Ned/Nrd
= Ned/Nrd = Acfcd+Asfyd = 0.85*fck = = fyk/1.15 = = =
kNm
Fig15>
25.5 400
11998.0 0.05907
interpolate the value a from table, Clause 5.8.9(4), Notes to Exp 5.39
57 4.2
Comparison of design output
Eurocode 2 designs are always claim to produce more economic result of compare with BS 8110 designs. In this research the comparison on the column design have been done to justify the claim. Theoretically direct c omparison between 2 different codes is difficult to be made because 2 codes are differs from each other from very beginning of the design process. For example: Characteristic concrete
strength, stress block, ways of load combination and partial load factor (γ G, γQ). Hence in order to compare the both codes assumptions need to be made and checking on the biaxial bending will ignore. In this research will only compare the design output of Short Biaxial column and Slender Biaxial column with varies of column size and loading applied.
4.2.1
Comparison short column with various of column dimension
58 1)
Lenght of column and length of beam are fixed to be 3m and 5m.
2)
Beam dimension are fixed to 300mm*500mm.
3)
The axial load are equal to 1000kN.
4)
The moment on top and bottom of column are 500kNm and 250kNm.
5)
The column are assumse to be in a symmetrical frame with equal span length.
The result and data has been collected to form a table as below : Types of dimension Dimension(mm^2) Asreq(EC2) Asreq(BS8110) % of different
1 400*500 4565 8400 45.65
2 500*600 3521 6600 46.65
3 600*700 2739 5040 45.65
4 700*800 1826 4480 59.24
5 800*900 1440 3600 60
Table 4.1 : Percentage of differere on area of reinforcement required.
The average of differences among all the dimension is equal to 51.44%
Average 51.44
59 In this comparison several assumption has been done in both code of pratice in other to show the significant change between EC2 and BS8110 column design, for example : 1)
Lenght of column and length of beam are fixed to be 3m and 5m.
2)
Beam dimension are fixed to 300mm*500mm.
3)
Column dimension are fixed to 600mm*700mm
4)
The moment on top and bottom of column are 700kNm and 350Nm in both
direction. 5)
The column are assumse to be in a symmetrical frame with equal span length.
The result and data has been collected to form a table as below : Types of Loading Load(kN)
1 1000
2 2000
3 3000
4 4000
5 5000
60 4.2.3
Comparison slender column with various various of dimension of column column 20000
2 ^ 15000 m m / d e r 10000 i u q e r S 5000 A
15600 EC Column Design 9000
7826
BS Column Design
4620
3522
840
0 0
1
2
3
2880 1440
2240 1120 4
5
6 Types of Dimension
Fig 4.3 Comparison of BS and EC with various of Dimension In this comparison several assumption has been done in both code of pratice in other to show the significant change between EC2 and BS8110 column design, for example : 1)
Lenght of column and length of beam are fixed to be 9m and 5m.
61 4.2.4
Comparison slender column with various of loading
20000
2 ^ m 15000 m / d e r 10000 i u q e 5000 r s A
15900
EC Column Design BS Column Design
13500 10200
10200
8400
4891
9587 7435
5870
4500
0
Types of loading
0
1
2
3
4
5
6
Fig 4.4 Comparison EC and BS with various Loading
In this comparison several assumption has been done in both code of pratice in other to show the significant change between EC2 and BS8110 column design, for example : 1)
Lenght of column and length of beam are fixed to be 3m and 5m.
2)
Beam dimension
fixed to 300mm*500mm.
62 4.3
Analysis Analysi s of the output of comparison
From the result above, the percentage of differences generally is is more than 40%. The cause of the differences on both codes is the way to determine the design moment are different from each other. For example, in EC 2 the design moment taken from the highest value of Z-Z and X-X direction was then select a suitable reinforced area required. The sufficient of reinforcement will check with the biaxial bending with trial and error method. For the purpose of comparison the biaxial bending checking are not not perform in this paper. Where as in BS the bending toward major or minor direction need to figure out first then t hen design moment will be taken as
moment experienced plus with certain percentage(β) of moment from the other direction. Therefore , it is found that the design moment of EC2 are far more lesser than BS. Beside N-M interaction chart is also another factor that cause the different in the result above. Direct comparison on N-M interaction chart are not applicable this is because different approach are using in both codes. But some other research has been done and shown the effect.
63 Figure 4.5 : Different N-M interaction chart
64
CHAPTER 5
CONCLUSION AND RECOMMENDATION RECOMMENDATION
5.1
Conclusion
With the aid of Microsoft Excel the design step of EC2 on column design and the comparison on both codes of practice have been done. The Microsoft Excel helps in eliminate the repetitive and help shorten the time of design and comparison. Beside the calculation with condition and graph plotting also been done more accurately if compare with manual design.
65 5.2
Recommendations
Even though this research has done, but the improvement still needed in order to obtain a more accurate and more reliable design outcome. There are several recommendations as below: 1)
In this research the columns are assumed to experience biaxial moment.
Other types of behavior could be use in the future. 2)
Due to the short of data the design of nominal cover and second order effect
are using conservative value. A more economic nominal cover and moment moment can be obtained with sufficient data in the future. 3)
Comparison on varies of loading and column have been done. It is suggest to
try on varies loading and varies column height in the future. 4)
Simply Excel sheet had built during this research. Users are required to
manually input several data. Therefore, it is recommend to upgrade the excel sheet to more user friendly interface.
66 REFERENCES
1.
Bill Mosley,John Bungey and Ray Hulse . Reinforced Concrete Design to Eurocode 2(Sixth Edition. New York : PALGRAVE
2.
Bill Mosley,John Bungey and Ray Hulse . Reinforced Concrete Desig n. New York : PALGRAVE
3.
BSI British Standard.BS Standard.BS EN EN 1990:2002 Eurocode: Eurocode: Basis of structural design
4.
BSI British Standard. BS Standard. BS EN 1991-1-1:2002 1991-1-1:2002 Eurocode 1 : Actions on
Structurs
(Part 1-1 : General actions - Densities self-weight, imposed loads for
buildings)
5.
2004 Eurocode 2 : Design of BSI British Standard ,“ BS EN 1992-1-1: 2004
67 11.
Dr. Usama Zakout Ministry of Public Works and Housing, Arab States
League St,
Gaza, Palestine .Comparison Palestine .Comparison of Different Codes for Analysis and
Design of RC Sections to/24 Flexural Moments .
12
Companion Document (EN1992-1-1 : Eurocode 2 :Design of Concrete Structures - Part 1 : General rules and rules for building. London :
Department
for Communities and Local Government. Government.
13
Mohd Asfanani Bin Sukiman. Computerized Sukiman. Computerized Design of Reinforced Elements
to
Eurocode 2, UTM 2006/2007
14
Chales E. Reynolds (2006) . Reynolds’s Reynolds’s Reinforced Concrete Designer’s Handbook Eleventh edition. Publish by Taylor & Francis Group
15
Dr R M Moss BSc PhD CEng MICE MIStructE , EC2 and BS8110 BS8110 compared.
68 APPENDIX A BS Column design Effective height
X-X Direction
b h Acolumn
= = =
500 mm 600 mm 300000 mm^2
69
Design moment and Asreq for a Short Column
Checking the direction of bending Mx = 700 N My = 700 fcu b' = 550 , b'/b h' = 650 , h'/h Mx/h' = 1.08 My/b' = 1.27
= = = =
5000 kN 30 1.10 1.08 Chose,
d/h=
1.08
70
APPENDIX B Structural Analysis
71
72
APPENDIX C Construction Plan (Front)
73
APPENDIX D Construction Plan (Side view)
74
APPENDIX E Construction plan ( Plan view)
