Design Comparison of Different Structural Elements By using Different International Codes

Design Comparison of Different Structural Elements By using Different International Codes

Labani Nandi

M.Tech (Structural Engineering) Narula Institute of Technology Agarpara,Kol-109,W.B.,India

Prof. Priyabrata Guha Narula Institute of Technology Agarpara, Kol-109,W.B.,India

Abstract : – This paper is intended to compare the design of reinforced concrete structure with various International codes from economical point of view. Three different famous structural building codes have been adopted. These are the IS456:2000, BS8110:1985, and Euro Code2:1992. These codes have been compared in the strength design requirements of structural elements. The comparison include shear design.

Throughout this study elaborated design models and criteria of the considered codes have been exhibited. Although the principles contained in these codes are basically the same, they differ in details..

Keywords Different structural element like continuous slab,contineuous beam, column and column footing.

INTRODUCTION:

Engineering is a professional art of applying science to the efficient conversion of natural resources for the benefit of man. Engineering therefore requires above all creative imagination to innovative useful application for natural phenomenon.

THE DESIGN PROCESS:

The design process of structural planning and design requires not only imagination and conceptual thinking but also sound knowledge of science of structural engineering besides the knowledge of practical aspects, such as recent design codes, bye laws, backed up by sample experience, initiation and judgment. The purpose of standards is to ensure and enhance the safety, keeping careful balance between economy and safety.

The process of design commences with planning of the structure. primarily to meet its functional requirements. Initially, the requirements proposed by the client are taken into consideration. They may be vague, ambiguous or even unacceptable from engineering

point of view because he is not aware of the various implications involved in the process of planning and design, about the limitation and intricacies of structural science.

It is emphasized that any structure to be constructed must satisfy the need efficiently for which it is intended and shall be durable for its desired life span.

Thus, the design of any structure is categorized into the following two main types :-

1. Functional design

2. Structural design.

FUNCTIONAL DESIGN:

The structure to be constructed should be primarily serve the basic purpose for which it is to be used and must have a pleasing look.

STRUCTURAL DESIGN:

Structural design is an art and science of understanding the behavior of structural members subjected to loads and designing them with economy and elegance to give a safe, serviceable and durable.

STAGES IN STRUCTURAL DESIGN:

The process of structural design involves the following stages-

1.0 Structural planning.

2. 0 Action of forces and computation of loads.

3.0 Member analysis.

4.0 Member design.

5.0 Comparison between various RCC. Design code.

6.0 Detailing, drawing and preparation of schedules.

This paper is devoted to focus a spot of light on design the minimum or maximum area of steel

requirement for elements of concrete structure. Three different International Structural building codes are adopted in this study. These are: [1] IS 456:2000; [2] BS 8110:1985 and [3] EC2:1992 for the design of concrete structures.

1. ABBREVIATIONS AND ACRONYMS:

   1. As per IS Code:

      L = Effective span d = Effective depth

      Wd = Factored dead load Wl =Factored live load

      Mu,lim = Limiting bending moment Pt = Percentage of steel

      Vu = Shear force

      tv = Nominal shear stress tc = Design shear strength Ld = Development length P = Spacing of stirrups

      Pu = Ultimate load on column Ks = Co-efficient

      bc = Short side of column section/Long side of column section

      fck = Characteristic cube compressive strength of concrete

      f y = Characteristic strength of steel

   2. As per BS code:

      M = Bending moment

      calculating the effective span of a member

      gk, Gk= characteristic permanent action

      qk, Qk = characteristic variable action

      fck = characteristic compressive cylinder strength of concrete at 28 days

      fyk = characteristic yield strength of reinforcement

      As = Area of tension reinforcement

      AV = Area of shear reinforcement within a distance S Mu Factored IS,BS and EC Codes moment at section S: Spacing of stirrups

      V = Nominal shear strength of section

      Vc = Nominal shear strength provided by concrete VRd1 = EC2 concrete shear strength

2. UNITS:

   Use either SI (MKS) or CGS as primary units. (SI units are encouraged.) English units may be used as secondary units (in parentheses).

3. EQUATIONS:

1. As per IS code:

   Basic L/d = 26 [For continuous beam]

   Basic L/d = 20 [For simply supported beam]

   B.M. for end span:

   WdL2/12 + WlL2/10 [B.M. at the centre of the end span] WdL2/10 + WlL2/9 B.M.[over penultimate support]

   B.M. for intermediate span:

   As = Area of steel

   WdL2/16 + WlL2/12[B.M. at the centre of the span] W L2/12 + W L2/9 [B.M. over interior support]

   S = Development length d l

   Vs = Shear force

   V = Nominal shear stress

   Pu = Ultimate load on column

   VEd = Design shear stress at the column perimeter

   Mu,lim=0.138fckbd2

   Pt = 50[1-{1-(4.6*Mu)/fck Vu = 0.6(Wd+Wl)L

   tv = Vu/bd

   bd2}½]/(fy/fck)

   As = Cross sectional area of reinforcement

   ASV = Cross-sectional area of shear reinforcement in the form of link

   F = Ultimate load

   Ld < 0.1.30(M1/Vu)+L0

   p = (0.87fyAwd/Vus)

   Pu = o.40fckAc + 0.67fyAsc

   tv = Vu/b'd' [Nominal shear stress]

   fy = Characteristic strength of reinforcement fcu = Characteristic concrete cube strength8+/

   1. As per EC code:

   MRd = Ultimate moment of resistance

   K0 = Co-efficient of main reinforcement VRd,c = Design shear resistance of concrete b = width of section

   d = effective depth of the tension reinforcement

   h = overall depth of section Z = lever arm

   A1, a2 = allowance at supports used for

   b'd' dimension at the critical section of footing. ks = 0.5+bc

2. As per BS code: M = 0.086FL

   As = M/ (0.87fyz) S (ft)/(4rfb) Smax = ft/2rfb

   M = 0.09FL [Near middle of end span]

   M = 0.11FL[At first interior support(-Ve Moment)] M = 0.07FL[At middle of interior spans]

   M = 0.08FL [At interior supports(-Ve Moment)] As = 0.156fcubd2/(0.87fyz

   Code	Actual grade of concrete	Considering grade of concrete	Actual grade of steel	Consideri ng grade of steel
   IS 456:2000	M30	M30	Fe415	Fe415
   BS8110: 1995	M30	M30	Fe460	Fe415
   EC2:1992	M30	M30	Fe500	Fe415

   Vs = 0.6F wu(support weidth/2)

   V = Vs/bd < 0.8fcu½

   Pu = 0.40fckAc + 0.67fyAsc

   can be predicted, and the probability of particular load combinations occurring. Table (1)

   Illustrates the values of partial factors of safety for the loaings, and a basic load combination Stipulated by the three codes [1, 2, 3].

   Table (1) Basic Load Combinations and Partial Safety Factors (df) at the Ultimate Limit State :

   Code	Dead Load (DL)	Live load (LL)
   IS 456:2000	1.5	1.5
   BS8110:1985	1.4	1.6
   EC2:1992	1.35	1.5

3. As per Euro code:

Basic L/d = 31 MRd = 0.167fckbd2 As = M/0.87fykZ

Z = d[0.5+(0.25-3K0/3.4)1/2]

K0 = M/fckbd2

Ds = 5/8×fck×Areq/Aprov

Checked Basic L/d = K[11+1.5f

1/2(p /p)+3.2f

Table (1)

Dead Load (DL)

Live load (LL)

1.6

1.5

1.4

1.3

1.2

(p /p-

1)3/2]

As,max = 0.04Ac

As,min = 0.26fctmbtd/fyk

ck 0

ck 0

VRd,c = [CRd,cK(100P1fck)1/3+Kdcp]bwd VEd =ß(V1d/u0d) VRd,max = 0.5vfcd

V = 0.6[1-(fck/250)]

CRd,c = 0.18/dc K = 1+(200/d)½

P1 = (p1y p1x) =[As1,y/bd . AS1,x/bd]½ Vmin = 0.035K3/2f½

VRd,c =[ CRd,cK3/2+K1dcp]×[2d/a]

RESULT:

GRADE OF CONCRETE AND STEEL:

Table (2)

LOADING :

The three codes impose partial factors of safety for loads due to design assumptions and inaccuracy of calculation, possible unusual load increases, and constructional inaccuracies.

Design load = characteristic load* partial load factor of safety

The value of this factors of safety takes into account the importance of the limit state under Consideration and reflects to some extent the accuracy with which different types of loading

A.CALCULATING AREA OF STEEL WITH RESPECT TO ACTUAL GRADE OF CONCRETE AND STEEL:

Code	SLAB [Ast]	BEAM [Ast]	COLUMN[ Ast]	FOUNDATI ON[Ast]
IS 456:2000 [M30 &Fe415]	279	619.64	1240.37	1676.88
BS8110: 1995[M30& Fe460]	203.41	583.88	1653.23	2080
EC2:1992 [M30&Fe50 0]	269.57	743.17	1512	2080

Table (3)

2500

Code

2000

1500

SLAB

1000

BEAM

500

0

COLUMN[Ast]

1 2 3 4 5 6 7 8

B.CALCULATINGAREAOFSTEELWITH RESPECT TO CONSIDERIND GRADE OF CONCRETE AND STEEL:

Code	SLAB [Ast]	BEAM [Ast]	COLUMN[ Ast]	FOUNDATI ON[Ast]
IS 456:2000 [M30 &Fe415]	279	619.64	1240.37	1676.88
BS8110: 1995[M30& Fe415]	225.47	647.12	1840.21	2080
EC2:1992 [M30&Fe41 5]	324.78	895.39	1821.67	2080

SLAB

2500

2000

1500

1000

500

0

Table (4)

FOUNDATION[

Ast]

CONCLUSION:

The main conclusions from this study can be summarized as follow:

[1]. Although the principles contained in the considered the grade of concrete is same for three codes differ in grade of steel.

[2]. Calculating the area of steel with respect to actual grade of concrete and grade of steel. Result showing that-

1. For slab Area of steel is maximum as per IS code than BS and EC.

2. For beam Area of steel is maximum as per EC code than IS and BS.

3. For column Area of steel is maximum as per BS code than IS and BS.

4. For foundation Area of steel is minimum as per IS code than BS and EC.

5. For foundation with respect to EC code minimum steel are to be provided.

[3]. Calculating the area of steel with respect to providing grade of concrete and grade of steel. Result showing that-

1. Increasing the area of steel of the all structural element with respect to actual grade of concrete and steel.

2. For foundation with respect to EC code minimum steel are to be provided.

REFERENCE:

1. Indian Standard PLAIN AND REINFORCED CONCRETE CODE OF PRACTICE.[IS 456:2000].

   BEAM

   COLUMN[Ast]

2. BS8110:1995 Structural Use of Concrete, Part 1, 2 British Standard Institute.

3. W. H., Mosley, R., Husle, and J. H., Bungey, Reinforced Concrete Design to Euro Code 2, Macmillan Press Ltd, 1996.

4. DESIGN OF STRUCTURAL ELEMENTS CONCRETE,STEEL WORK,MASONRY AND TIMBER DESIGNS TO BRITISH STANDARD AND EUROCODES By Chanakya Araya.

5. DESIGN OF REINFORCED CONCRETE STRUCTURE By S. Ramamurtham.

6. DESIGN OF REINFORCED CONCRETE STRUCTURE By Krishna raju.

7. Journal on Strength Design Requirements of ACI-318M-02 Code, BS8110, and EuroCode2 for Structural Concrete by Asst. Lect. Ali Abdul Hussein Jawad Civil Engineering Department, College of Engineering Al-Mustansiriya University, Baghdad, Iraq

8. Mini project report on ANALYSIS AND DESIGN OF COMPONENT REINFORCED CONCRETE STRUCTURE By DIVYA Kamath(08241A0113) & K.Vandana Reddy(08241A0155),Department of civil engineering, Gokaraju Rangaraju Institute and Technology, Bachupally,Hyderabad.

9. INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING vol-2,No-3 2001 by Manish Varma, Umesh Pendharkar, Ravi K. Sharma.

10. [10] Manual for design and detailing of RC code of practice for structural use of concrete 2004 by housing department may 2008(version 2.3).