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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

CRACKED WIDTH PATTERN ANALYSIS USING

DIFFERENT GRADE OF STEEL AND CONCRETE

Gopal Patel1* and Vijay Baradiya1

a Department of Civil Engineering, IES, IPS Academy, Indore, MP, India.

*Corresponding author:Gopal Patel � er.gp1586@gmail.com

ISSN 2319 – 6009 www.ijscer.com

Vol. 3, No. 1, February 2014

© 2014 IJSCER. All Rights Reserved

Int. J. Struct. & Civil Engg. Res. 2014

Research Paper

INTRODUCTION

The object of the present work is to study thebehavior of various beam sections of differenteffective depths for its different structuralproperties and to suggest feasible selectionsin order to achieve durable beam sectionwhich is safe in bending and shear. This hasbeen accomplished by the use of softwareknown as ‘Response 2000’ which gavedifferent graphs for well designed beamsections.

This paper presented the behavior of beamsections by analyzing Crack width.Conclusions have been drawn keeping in mind

The aim of this paper is to examine the influence of three variables on crack width of reinforcedconcrete beams. A computer program RESPONSE 2000 was used to predict crack width,longitudinal of reinforced concrete beams without axial loads. Nine beams of varied sectionswith different variables were analyzed using the program. The variables are concrete strength,amount of longitudinal reinforcement and spacing of transverse reinforcement. The input consistsof beam geometry, material properties and loading. A confined stress-strain curve for this isapplied in the program. Computer analysis indicates that the crack width decreases with theincrease of longitudinal reinforcement and concrete strength. On the other hand, the spacing oftransverse reinforcement does not have any significant influence on the crack width.

Keywords: Crack width, Reinforeced concrete, Beam, Response 2000

that the beam is safe in bending and shear.The percentage increase and decrease ofvarious values like deflection (in mm) andmoment (KN-m) have also been taken intoaccount. The study also helps predict the failuremode of the beam sections.

The objective of this research-based workis also to study the feasibility of using highperformance steel as shear reinforcement forconcrete beams. High performance steel ischaracterized by enhanced corrosionresistance and higher strength in comparisonto conventional Grade Fe-250 steelreinforcement. Advantages of using higher

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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

strength steel include the ability to design forlonger span lengths and reducing the amountof material needed for design. This couldgreatly reduce the overall costs of constructionfor future structures.

Nine reinforced concrete beams weredesigned using Fe-415 and Fe-500 forlongitudinal bars as well as for the stirrups. Themain variables considered in the study are:

1. Grade of Concrete,

2. Type of reinforced steel material, and

3. The diameter of bars used.

ANALYSIS OF CRACK WIDTH

This paper investigate the effects of bardiameter of reinforcing steel , grade ofconcrete and grade of steel on crack widths.The low tensile strength of concrete relative toits compressive strength means that most non-prestressed concrete in service is cracked tosome degree. In zones of tension, the steelreinforcement is engaged primarily when acrack occurs, and design of reinforcedconcrete structures is carried out based on thefact that significant portions of the structure arecracked. However, the widths of these cracksmust be limited for appearance, durability andstructural integrity. It is important to limit crackwidth so as to ensure adequate shearbehavior. As crack widths increase, their abilityto transfer shear stresses by aggregateinterlock decreases. Members in which thereis insufficient reinforcement to control crackwidths are at risk of developing wide cracksthat may result in a premature shear failure.

The crack width of a flexural crack dependson the following quantities.

1. Amount of prestress

2. Tensile stress in the longitudinal bars

3. Thickness of the concrete cover

4. Diameter and spacing of longitudinal bars

5. Depth of member and location of neutral

axis

6. Bond strength

7. Tensile strength of concrete.

LIMITS OF CRACK WIDTH

Clause 19.3.2 of IS: 1343 - 1980 specifieslimits of crack width such that the appearance

and durability of the structural element are not

affected. The limits of crack width are as

follows:- Crack width ≤0.2 mm for moderate

and mild environments ≤0.1 mm for severe

environment. The types of environments are

explained in IS: 1343 – 1980.

A. Indian Code Provisions

According to the explanatory handbook on

Indian concrete code, the width of flexural crack

at a particular point on the surface of a flexural

member is found to increase with the increase

in the following three major influence factors:

1. Average tensile strain at surface, which in

turn, increases with increase in the mean

tensile strain, εsm in the neighboring

reinforcement.

2. Distance between the point on the surface

and the nearest longitudinal bar which run

perpendicular to the crack.

3. Distance between the point on the surface

and the neutral axis.

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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

Figure 1: Response 2000 Format Sample

RESULTS AND DISCUSSION

The complete solution of the problem is shownin Figure 3 and Table 1.

In the present work Response 2000software is used to determine the crack width.The Figure and 2 shows the plot between crack

Figure 2: Crack Width Vs. Beam Depth Beam Size 300x600and 25 mm Bar Dia (Fe 415) with Varying Concrete Grade

width and beam depth for different grade ofconcrete and the reinforcement grade to bekept same (Fe-415 and Fe-500). As per thestudy we observe that for Fe-415 grade of steelthe percentage decrease in crack widthbetween grades M15 to M20 and M25 to M30 is

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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

Figure 3: Crack Width Vs. Beam Depth Beam Size 300x600and 25 mm Bar Dia (Fe 500) with Varying Concrete Grade

Table 1: Crack Width vs Beam DepthBeam Size 300x600 and 25 mm Bar Dia(Fe 415) with Varying Concrete Grade

Grade Variation 415 500

M15-M20 20% Dec 20% Dec

M20-M25 50% Dec No Effect

M25-M30 20% Dec No Effect

20%. While for grade M20

to M25

it is almostdecrease upto 50%.

For Fe-500 grade of steel the percentagedecrease in crack width between grades M15

to M20 is 20%. But for grade between M20 toM

25 and M

25 to M

30 no significant decrease in

crack width is observed.

CONCLUSION

Response-2000 program was used tocalculate the crack width of reinforced concrete

beam. The calculated crack widths werechecked with the limiting value given inIS:1343 1980. As per the study we observethat for Fe-415 grade of steel the percentagedecrease in crack width between grades M15

to M20 and M25 to M30 is 20%. While for gradeM

20 to M

25 it is almost decrease upto 50%. For

Fe-500 grade of steel the percentagedecrease in crack width between grades M15

to M20

is 20%. But for grade between M20

toM25 and M25 to M30 no significant decrease incrack width is observed

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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

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Int. J. Struct. & Civil Engg. Res. 2014 Gopal Patel and Vijay Baradiya, 2014

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