An Experimental Study on Growth of Time-Dependent Strain in Shape Memory Alloy Reinforced Concrete...

7/30/2019 An Experimental Study on Growth of Time-Dependent Strain in Shape Memory Alloy Reinforced Concrete Beams

1/15

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6308 (Print),ISSN 0976 6316(Online) Volume 3, Issue 2, July- December (2012), IAEME

108

AN EXPERIMENTAL STUDY ON GROWTH OF TIME-DEPENDENT

STRAIN IN SHAPE MEMORY ALLOY REINFORCED CONCRETE

BEAMS AND SLABS

S.R.Debbarma1

; S.Saha2

1 *SeniorScientist, CSIR-Central Mechanical Engineering Research Institute,

P.O: M.G.Avenue, Durgapur-713209, West Bengal, India.

E-mail: [email protected], [email protected]

2.Professor, Civil Engg. Dept. National Institute of Technology,

P.O: M.G.Avenue, Durgapur 713209, West Bengal, India,E-mail: [email protected], [email protected]

ABSTRACT

This paper highlights the useful properties of Shape Memory Alloy (SMA), towards utilization inconcrete structures. The ability of SMA bars to reduce growth of time-dependent and thermal

strains in concrete beams and slabs using laboratory scale model was investigated upto concrete

age of 600 days and are hereby presented in this paper. It was observed that the growth of time-

dependent strain was less in the treated beams and slabs reinforced with a combination of SMAand conventional steel bars, than in controlled beams and slabs with only conventional steel bars.

With increase in age of concrete the difference between strain growths in treated and controlled

specimens increases, maintaining the parameters of size, percentage area of reinforcement,concrete grade and environmental conditions same. With increase in span and ambient

temperature the influence of SMA reinforcement in reducing time-dependent strain growth was

more prominent. Mechanical behavior of the test specimens were analyzed using Model Codes,ACI 318 (2005) and CEB (1993) and found that, higher yield strength of SMAs, increases

cracking moment and effective moment of inertia of the treated specimens under dead-load. This

restricts growth of time-dependent deflections and therefore strains in treated flexural specimens.

Keywords: shape memory alloy, superelasticity, smart materials, time-dependent strain,

reinforced concrete, flexural member

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND

TECHNOLOGY (IJCIET)

ISSN 0976 6308 (Print)

ISSN 0976 6316(Online)

Volume 3, Issue 2, July- December (2012), pp. 108-122

IAEME: www.iaeme.com/ijciet.html

Journal Impact Factor (2012): 3.1861 (Calculated by GISI)www.jifactor.com

IJCIET

I A E M E


2/15


109

1. INTRODUCTIONThe time-dependent effects of concrete, due to creep and shrinkage, leads to a growth in strainwith its age. It causes considerable impact on the performance of concrete structures causing an

increase in deflection as well as affecting the stress distribution. Creep and shrinkage also cause

dimensional changes in the material under the influence of sustained loading. This strain inconcrete depends upon the uncertainties of inherent material variations as well as modeling.

Studies of uncertainties in creep and shrinkage effects were performed by many scholars [1], [2],

[3], [4], [5]. The variation of creep and shrinkage properties is caused by various factorscommonly classified into internal and external factors [6]. The internal factors are the variations

in quality and mix composition of the materials used in the concrete whereas external factors are

the changes in environmental conditions, such as humidity, temperature etc. Studies on the

various individual time effects due to creep and shrinkage in concrete structures can be found inthe work of Gilbert [7]. Various predictive models have been developed to predict the creep and

shrinkage in concrete. Goel et al. [8] compared the predicted strain values from different models

with experimental results, and found the model GL2000 to be the closest. The influence of

shrinkage on the behavior of reinforced concrete beams was investigated numerically by Viktoret al. [9] and compared with test data reported in literature. It was found that the shrinkage had

significantly reduced the cracking resistance and led to larger deformations. In spite of all thesestudies and great advances in theories, the time dependent effects in reinforced concrete

structures due to creep and shrinkage have not been controlled satisfactorily. The fact lies in the

complexity of time-dependent effects of concrete structures.To solve the problems of deteriorating concrete structures, there is a wide scope of researchtowards the use of smart materials like Shape Memory Alloy (SMA) in concrete structures,

Janke L et al. [10]. The pilot study of SMA reinforced concrete beams by Saiidi M.S et at [11]

shows that average residual displacement, was less than one-fifth than that of steel reinforced testbeam. The investigation into rehabilitation properties of intelligent concrete beams reinforced

with SMA strands conducted by Di et al. [12] found that on heating the SMA strands byelectrical current, the developed cracks on loading can be reduced. The load-deflection behavior

of SMA reinforced concrete beams through a parametric study was conducted by Elbahy et al.[13] and a suitable model was recommended for deflection analysis, which was found to be more

accurate than existing models. Ding et al.[14] proposed a simplified model based on the elastic

theory of plasticity to simulate the behavior of the superelasticity of the SMA, in which themartensite volume fraction is considered as one of the state variables. The experimental results

on deformation behavior and its influencing factors on smart concrete beams strengthened with

SMA wires were presented by Jingsi et al.[15]. An increase in the initial pre-strain of SMA wirecan significantly improve the capacity of self-restoration of the beam but the main steel bars play

a very negative role in reducing residual deformation. The behavior of concrete beams driven by

heated SMA wires using electrical current was studied by Hui et al. [16] and the results indicatethat recovery forces of the SMA wires can decrease the mid-span deflection of the beam,

decrease the absolute value of compressive strain and even compress the concrete in the tensile

zone. The suitability of using sectional analysis to evaluate the moment-curvature relationship

for SMA reinforced section was investigated by Elbahyet al. [17] who proposed to estimate theirrecommended values. Lee et al. [18] investigated the buckling and post buckling control of

composite beams with embedded shape memory alloy actuators. Krstulovic-Opara et al. [19]

tested SMA composites for their ability to improve reinforcing and pre-stressing of concrete


3/15


110

structures. The deflections in specimens fully recovered and the cracks were hardly visible after

unloading. DesRoches et al. [20] and Johnson et al. [21] explored the potential use of Ni-Ti rods

as seismic restrainers in multi frame bridges. Although SMAs have been known for decades,they have not been used much in civil structures until rather recently.

This paper presents the experimental results of time-dependent strain growth upto 600 days age

of concrete, in treated beams and slabs reinforced with SMA & conventional steel bars andcontrolled beams & slabs reinforced with only conventional steel bars. Increases in stiffness of

treated specimens were determined by comparing strain results, with corresponding controlled

specimens. All the treated and controlled specimens were analyzed using two Model Codes tovalidate the experimental results.

2. OVERVIEW OF SMA APPLICATION IN CIVIL STRUCTURESThe Shape Memory Alloy is one of the smart metal alloys having two very important properties:

the shape memory effects and the superelasticity. Civil structures can act as passive, semi-active,

or active components on integration of SMA, to reduce damages caused by internal and external

forces. A mechanical stress will occur in the material if the deformation recovery of SMA isrestrained due to its superelastic properties. This recovery stress can be used in concrete

structures to introduce internal forces and restrict growth of any strain. The properties for whichSMAs can be integrated in civil structures are:

The force generated upon regaining its original shape has very useful applications. Repeated absorption of large amounts of strain energy under loading without permanent

deformation.

Higher yield strength and superelastic properties of austenite phase SMA bars increases itsstiffness.

SMA has excellent damping characteristics below the transition temperature range.

Excellent property of corrosion resistance (comparable to series 300 stainless steels) and non-magnetic in nature.

SMA has low density and high fatigue resistance under large strain cycles. It has the ability to be heated electrically for recovery of shape.Substantial research has been conducted on the use of SMAs in the construction of new

structures in the form of reinforcement, bolted connections, restrainers, bracings and pre-

stressing strands.

3. RESEARCH SIGNIFICANCEGrowth of time-dependent strain causes reduction in service life of concrete structures and it may

causes failure with increase in age of concrete. The ability of superelastic austenite phase SMAbars to restrict growth of time-dependent strain in concrete flexural members under dead load,

when used as reinforcements in combination with conventional steel has been investigated.Development of durable and cost effective high performance construction materials and systems

is very important for the economy of a country, as the valuation of civil infrastructure constitutes

a major portion of the national wealth. Thus the results of this study will be useful to understandthe time-dependent behavior of concrete flexural members when reinforced partially with SMA

bars.


4/15


111

4. EXPERIMENTAL PROGRAMEight numbers of laboratory scale Reinforced Cement Concrete (RCC) beams of 125mm widthand 250mm depth and four numbers of RCC slabs of size 1000 sq. mm and 75mm thick were

designed and constructed using similar grade of concrete. Four beams were of span 1.0 meter

and rests four were of span 2.0 meter. Among all the test specimens, half of them were controlledspecimens reinforced with conventional steel bars and other half were treated specimens

reinforced with combination of conventional steel and SMA bars. The total percentage areas of

reinforcement in respective controlled and treated specimens were kept same. In 1.0 meter spanbeams all the bars were placed for the whole length, where as in 2.0 meter span beams, tension

zone reinforcements other than corner bars were placed for middle half length of 1.0 meter.

Shear reinforcements were 8 mm diameter steel stirrups spaced at 150 mm center to center with

clear concrete cover of 25 mm.

Regular monitoring was done to record the growth of time-dependent strain in all the beams and

slabs with increase in its age. Details of the controlled & treated beams and slabs are shown in

Table-1. Test variables were types of reinforcements, its span and the age (days) of concrete. Tomeasure the growth of time-dependent strain and corresponding temperature, Vibrating Wire

(V.W) strain gauges were embedded in test beams and slabs at mid-span during construction. Inbeams V.W strain gauges were fixed along compression and tension reinforcement and in slabs,

along the top layer of reinforcement.

Table-1: Identity and parameters of Experimental Beams and Slabs:

Test Specimens Identity Span(mm)

No ofSam-

ple

% area

of Fe415

% area

of SMA

% area ofSMA to total

reinforcement

Controlled Beams B1Fe2 1000 02 0.96 --

B2Fe2 2000 02 0.96 --

Treated

Beams

B1SM2 1000 02 0.64 0.32 33.3

B2SM2 2000 02 0.64 0.32 33.3

Controlled Slab S1Fe4 1000 02 1.08 --

Treated Slab S1SM4 1000 02 0.81 0.27 25.0

4.1MaterialsThe materials used in the concrete were Type-I Portland cement, crushed stone aggregate with amaximum size of 15mm and fresh river coarse sand. The proportion of cement: coarse aggregate:

coarse sand: water by weight were 1: 1.23 : 2.75 : 0.45. The average compressive strength of the

concrete using cube specimen of size 150x150x150 mm3 at 7 days was 19.9MPa, and at 28 days

was 25.3 MPa. Modulus of elasticity of concrete was 25.2 GPa and flexural strength was 3.5MPa.


5/15


112

Figure 1: Stress Strain relationship of 8 mm SMA bar

Table-2: Chemical composition of SMA bars in use:

Elements Ni Ti Cu Cr H Fe Nb C

% by

weight

56.25 Balance 0.8 0.9 0.3 4.2 2.0 1.1

Conventional steel reinforcements were 8mm diameter high yield strength deformed bars

conforming to IS:1786, Grade Fe415. Modulus of elasticity of steel was 200KN/mm2, bulk

density 7860 kg/m3, Yield stress 415 MPa, Ultimate tensile strength 485 MPa and 14.5

percentage elongation.

SMA bars were 8mm diameter NITINOL bars and chemical compositions are shown in Table-2.

Unit weight of 8mm diameter SMA bar was 0.326 kg/meter and bulk density was 6492 Kg/m3.

Transformation temperature of SMA bars was measured in a Differential Scanning Calorimeter

at stress free state. Austenite start temperature (As) was observed -38.0 C and austenite finish

temperature (Af) was -28.3 C. The recorded value of tensile strength and elongation of the SMAbars were 502 MPa and 20.2% respectively. The stress strain graph of 8 mm diameter SMA bar

is shown in Figure-1. Modulus of elasticity of SMA was 110 KN/mm2. Transformationtemperature of the SMA bar was selected such that it exhibits super-elastic properties and higherstiffness at normal atmospheric temperature. Straight, austenite phase SMA bars in stress free

condition were embedded in tension zone of experimental beams and slabs as reinforcement.

Anchorage of plain surfaced SMA bars in concrete beams were made by fixing hexagonal steel

bolts of 20mm outer diameter at both the end of each SMA bars after making thread.


6/15


113

4.2Experimental beams and slabsSteel moulds with open end blocks were used for casting of beams and slabs. Vibrating nozzles

were used for proper compaction of machine mixed concrete in the steel moulds. All theexperimental beams and slabs were cured under moist condition for 28 days before putting in

simple supported condition. Details of the experimental beams and slabs are shown in Figure-2,

3 and 4. Sample photographs of experimental beams and slabs before and after concreting areshown in Figure-5.

4.3Testing Apparatus and ProcedureV.W embedment strain gauges fixed inside the beams and slabs (as shown in Figure 5) provided

frequency and temperature data through Read Out unit. In V.W strain gauges, plucking the wire

with electromagnetic coils and measuring the frequency of the resulting vibration provides the

development of tension in the wire. Measured frequency values were converted into strain valuesby multiplying gauge factors and also compensating for atmospheric temperature variations.

Growth of strain and corresponding temperature, at mid span were measured above and below

the neutral axis in all experimental beams and along the top layer of reinforcement in

experimental slabs at regular interval of days.

Figure 2: 1.0 meter span Experimental Beams, B1Fe2 & B1SM2

Figure 3: 2.0 meter span Experimental Beams, B2Fe2 & B2SM2


7/15


114

Figure 4: Experimental Slabs, S1Fe4 & S1SM4

5. TEST RESULTS AND DISCUSSIONDevelopment of strain at different atmospheric temperatures, with increase in age of concrete incontrolled and treated beams and slabs, under self weight is presented and discussed in this

paper. For every identical beam and slab specimens the results were almost same, so average

values are analyzed and presented in this paper.

5.1Growth of time-dependent strain with age of concreteAfter concreting, all the beams and slabs were kept over a flat surface for curing without any

imposed load. During these days of concrete, the growth of strain was observed negative ortensile in all the beams and was more in the treated beams than in the controlled beams. The

development of heat of hydration of cement during curing and lesser surface area to volume ratio

of concrete beams for radiation of heat causes minor expansion of concrete volume and results in

growth of tensile strain. Growth of negative or tensile strain was not observed in experimentalslabs during curing due to geometry of test slabs which helps to dissipate the hydration heat

temperature rapidly.All the beams and slabs were placed in Simply Supported (SS) condition after 28 days of moist

curing. In this position the growth of strain in all the controlled and treated beams were recorded

compressive at mid span sections above and below Neutral Axis (N.A). The recorded strains at

mid span in all the slabs were also compressive in nature. These strain values graduallyincreases further with increase in age of concrete. The recorded strain values were combination

a. SMA reinforced beam b. SMA reinforced slab c. Collection of strain and temperature

Figure 5: Photographs of experimental beams & slabs before and after concreting


8/15


115

of strain due to self-weight of experimental specimens and time-dependent strain at that

particular age of concrete. The growth of time-dependent strain at any particular age of concrete

was determined by deducting self-weight strain from the recorded strain values and shown inFigure-6, &7 for beams B1Fe2, B1SM2 and B2Fe2, B2SM2 respectively and Figure-8 for slabs.

Different span of beams are plotted separately due to their differences in self-weight and

corresponding strain values.

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 100 200 300

Strain,(xE-4)

Age of concrete in Days

below N.A, B1Fe2above N.A, B1Fe2below N.A, B1SM2

above N.A, B1SM2

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 100 200 300 400 500 600

Strain,(xE-4)

Age of concrete in days

above N.A, B2Fe2

below N.A, B2Fe2

above N.A, B2SM2

below N.A, B2SM2

Figure 6: Growth of strain with age of concrete in short span beams

Figure 7: Growth of strain with age of concrete in long span beams


9/15


116

The values of instantaneous strain of experimental specimens under self weight was calculatedusing standard bending theories of flexural members and found tensile below N.A andcompressive above N.A. The values of time-dependent strain in experimental specimens, and

percentage reduction of strain growth in treated specimens are shown in Table-3. The patterns of

strain development with increase in age of concrete were similar in all the experimentalspecimens with lesser values of strain in treated specimens, than in controlled specimens. During

early days of concrete, the rate of strain development was observed to be more rapid in

controlled specimens than in treated specimens. Presence of SMA as reinforcement in treatedspecimens having higher yield strength and superelastic properties prevents this rapid growth of

strain.

Table-3: Strain in treated and controlled specimensIdentity Age ofConc.

(days)

ExperimentalStrain (x10-4)

Strain due toself-weight

(x10-6

)

Time-dependent

strain (x10-4

)

Averagetime-

dependent

strain (x10-

4)

%reducti-

on of

strainTop

layer

Bottom

layer

Top

fiber

Bottom

fiber

Top

layer

Bottom

layer

B1Fe2 380 3.19 3.00 1.35 -3.87 3.18 3.04 3.11 6.75

B1SM2 380 2.92 2.85 1.47 -3.81 2.91 2.89 2.90

B2Fe2 600 5.63 4.65 5.38 -15.5 5.58 4.80 5.19 21.6

B2SM2 600 4.32 3.72 5.89 -15.3 4.26 3.87 4.07

S1Fe4 600 5.62 7.90 5.54 5.54 25.6

S1SM4 600 4.20 8.22 4.12 4.12

The growth of time-dependent strain at 600 days age of concrete was reduced by 21.6% in 2.0

meter span treated beams than that in controlled beams. In these treated beams one third area of

total steel was replaced with SMAs which were placed at tension zone in middle half span. Intreated beams of 1.0 meter span, the growth of time-dependent strain at 380 days age of concrete

was reduced by 6.8% than that of controlled beams by replacing one third area of total steel with

SMAs placed at tension zone for whole span. With increase in age of concrete this reduction in

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0 100 200 300 400 500 600

Strain,(x

E-4)

Age of concrete in days

treated slab

controlled slab

Figure 8: Growth of strain with age of concrete in slabs


10/15


117

strain growth will further increase. In both 1.0 meter and 2.0 meter span beams the area of steel

replaced with SMA were same but reduction in growth of strain was more prominent in longer

span beams as its age and span were more. In experimental treated slabs the growth of time-dependent strain at 600 days age of concrete was reduced by 25.6% by replacing one fourth area

of conventional steel bars with SMA bars. The higher yield strength property of SMA

reinforcing bars in treated specimens increases its stiffness and restricts growth of time-dependent strains.

It was observed that, in all the experimental beams, strain values were more in section above,

than in section below N.A (Figure-6 & 7 and Table-3). Presence of lesser percentage area ofreinforcement above N.A, results in more growth of strain than in section below N.A.

Development of these non-uniform strains across the depth of beam section will result in change

of its curvature with increase in its age as shown in Figure-9. The differences of strain values

between sections above and below N.A of 1.0 meter and 2.0 meter span controlled and treatedbeams are shown in Figure-10 &11 respectively. More the differences in strain values more will

be the changes in curvature of the beam axis under constant load. These differences in strain

values were observed to be less in treated beams than in controlled beams for both 1.0 meter and

2.0 meter spans.

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0 100 200 300 400

Strain(xE-4)


controlled beam

treated beam

Figure 9: Change in curvature of RCC beam with age of concrete

Figure 10: Difference in strain growth between sections above & below

N.A in 1.0 meter span beams


11/15


118

5.2Influence of ambient temperature in growth of time-dependent strainThe changes in atmospheric temperature directly influence the growth rate ratio of creep and

shrinkage and also affect the rate of aging of concrete (ACI209R-92). The growth of time-

dependent average strain in controlled and treated beams and slabs at different ambienttemperature are plotted in Figure-12 and 13 respectively. The rate of growth of time-dependent

strain was recorded higher in all the beams and slabs during summer days than in winter days.

Comparing the rate of strain growth between controlled and treated specimens at different

atmospheric temperature, it was observed that rate of strain growth was lesser in treatedspecimens than in controlled specimens. Differences between recorded temperatures at sections

above and below N.A of all the experimental beams were very small, so growths of non-uniform

thermal stress distribution were neglected. The change in ambient temperature did not influenceany phase transformation of SMA bars in use as they were so chosen to remain in austenite phase

under normal environmental temperature.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600

Strain,(xE-4)


controlled beam

treated beam

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

16.0 26.0 36.0

Strain,(xE-4)

Ambient Temperature in C

B1Fe2 B1SM2

B2Fe2 B2SM2

Figure 11: Difference in strain growth between sections above & below

N.A in 2.0 meter span beams

Figure 12: Growth rate of strain in beams at different ambient temperature


12/15


119

6. SECTIONAL ANALYSIS:Considering sectional equilibrium and from known stress-strain models of steel, SMA and

concrete the mechanical behavior of the controlled and treated specimens were analyzed. Foranalysis it was assumed that plane sections remain plane and perfect bond exists between the

concrete and reinforcing bars [22], [17]. In composite section of RCC, for balancing of strain the

concrete cannot reaches the strain level of SMA, which is ductile whereas concrete is very

brittle. When stress in steel bars reaches its yield value, maximum stress induced in the SMAbars will be less than their yield values due to higher yield strength properties. This causes

increase in depth of neutral axis (xu) of treated specimens in comparison to similar controlled

specimens, from their extreme compression fibers. The depth of neutral axis of the flexuralmembers directly influences its cracking moment (Mcr) of the section. This cracking moment and

bending moment due to imposed load over the flexural member, varies the effective moment of

inertia (Ie) [23] of the section.Cracking moments and Effective moment of inertiaunder self-weight of treated and controlled

specimens were calculated using two Model codes, ACI 318 [24] and CEB-FIP [25] and shown

in Table-4. The Mcr values for both 1.0 meter and 2.0 meter span beams were same as cross-sectional dimensions and reinforcement areas were similar at mid-span. It was observed from the

analyzed values that, the Mcr and Ie of treated specimens were more in comparison to similar

controlled specimens under dead load. Increase in effective moment of inertia of treatedspecimens increases its stiffness, which results in more resistance to the time-dependentdeflections and therefore strains.

0.0

2.0

4.0

6.0

15.0 20.0 25.0 30.0 35.0 40.0

Strain,(xE-4)

Ambient Temperature (C)

S1Fe4

S1SM4

Figure 13: Growth rate of strain in slabs at different ambient temperature


13/15


120

Table-4: Cracking moment & effective moment of inertia of test specimens

Identity

Depth of

N.A (mm)

Cracking Moment

(KN.m)

Effective Moment of

Inertia (m4)

ACI 318 CEB-FIP ACI 318 CEB-FIP

B1Fe2 64.5 3.14 2.26 4.33 1.62B1SM2 69.6 3.23 2.33 4.82 1.80

B2Fe2 64.5 3.14 2.26 0.07 0.025

B2SM2 69.6 3.23 2.33 0.08 0.028

S1Fe4 32.5 2.96 2.13 0.046 0.017

S1SM4 33.8 3.05 2.20 0.048 0.018

7. CONCLUSIONIn this paper, the behavior of cement concrete beams and slabs reinforced with SMA and

conventional steel bars was investigated through an experimental program. Their behaviors were

also analyzed through sectional analysis using two different Model Codes. The parameters, such

as growth of time-dependent strain and corresponding ambient temperature, were monitoredthrough this program. From these results the following conclusions can be drawn.

1. SMA bars can be used in practical civil engineering structures as reinforcement incombination with conventional steel bars, to reduce growth of time-dependent strain and

increase in stiffness; the resulting effect is considerable. A small percentage area of SMA

bars placed at maximum tension zone of flexural members could generate a large force dueto its higher yield strength and superelastic properties to restrict growth of time-dependent

strain.

2. The growth of time-dependent strain at 600 days age of concrete was reduced by 21.6% in2.0 meter span treated beams than that in controlled beams by replacing one third area oftotal steel with SMAs, placed at tension zone in middle half span. In treated beams of 1.0

meter span, the growth of time-dependent strain at 380 days age of concrete was reduced by6.8% than that of controlled beams by replacing one third area of total steel with SMAsplaced at tension zone for whole span.

3. The reduction of time-dependent strain growth was more prominent in longer span treatedbeams than in shorter span beams.

4. The growth of time-dependent strain at 600 days age of concrete in simple supported RCCtreated slabs was reduced by 25.6% than that in controlled slabs, by replacing one fourth area

of conventional steel bars with SMA bars.5. Analysis of test specimens shows that higher yield strength properties of SMAs, increases

cracking moment and effective moment of inertia, of the treated specimens under dead load

and restricts growth of time-dependent deflection and therefore strain.

6.

Increase in ambient temperature increases the growth rate of time-dependent strain and wasrelatively more in specimens reinforced with conventional steel bars, than in specimens

reinforced in combination with steel and SMA.

7. Growth of any non-uniform strain across the depth of RCC flexural members minimized onuse of SMA reinforcements which restricts the changes in curvature of beam axis with its

age.


14/15


121

ACKNOWLEDGMENT

I acknowledge that, this research fund was granted from CSIR-CMERI, through Project No.OLP096312.

REFERENCES

1. Bazant, Z.P. and Liu, K.I. (1985). Random creep and shrinkage sampling. Journal ofStructural Engineering, ASCE., 111(5), pp.1113-34.

2. Diamonds, D., Madsen, H.O. and Rackwitz, R. (1983) On the variability of the creepcoefficient of structural concrete.Journal of Materials and Structures,17(100):pp.321-8.

3. Madsen, H.O. and Bazant Z.P. (1983). Uncertainty analysis of creep and shrinkage effectsin concrete structures.ACI Journal: 80(2): pp. 116-127.

4. Li, C.Q. and Malchers, R.E. (1992). Reliability analysis of creep and shrinkage effects.Journal of Structural Engineering, ASCE:118(9): pp. 2323-2337.

5. Choi, B.S, Scanlon, A., Johnson, P.A. and Monte C. (2004). Simulation of immediate andtime-dependent deflections of reinforced concrete beams and slabs.ACI Structural Journal,101(5): pp.633-41.

6. Bazant, Z.P (1998).Mathematical Modeling of creep and shrinkage of concrete. John Wiley& Sons.

7. Gilbert, R.I. (1988) Time effects in concrete structuresElsevier.8. Goel, R., Kumar. R. and Paul, D.K. (2007).Comparative study of various creep and

shrinkage prediction Models for concrete. Journal of Materials in Civil Engineering,Vol.19, No.3.

9. Viktor, G., Gintaris, K. and Darius, B. (2008). Shrinkage in reinforced concrete structures:A computational aspect.Journal of Civil Engineering and Management, 14(1); pp. 49-60.

10.Janke L, Czaderski C, Motavalli M, Ruth J. (2005), Application of Shape Memory Alloys incivil engineering structures-overview, limits, and new ideas. Materials Structures 38(5);pp.578-592.

11.Saiidi M.S, Zadeh M.S., Ayoub C., Itani A. (2007), Pilot study of Behaviour of concreteBeams Reinforced with Shape Memory Alloys, Journal of Materials in Civil Engineering,

ASCE, 19(6), pp.454-461.

12.Di, C. and Ping, G. (2011). Rehabilitation of Concrete Beam by Using Martensitic ShapeMemory Alloy Stands.Advanced Materials Researches, Vol.243-249, pp. 5527-5530.

13.Elbahy, Y. I., Youssef, M. A. and Nehdi, M. (2010). Deflection of superelastic shapememory alloy reinforced concrete beams: assessment of existing models. Canadian Journal

of Civil Engineering, Vol.37, Number 6, pp. 842-854 (13).

14.Ding, Y., Chen, X., Li, A. and Zuo, X. (2011). A new isolation device using shape memoryalloy and its application for long-span structures. Journal of Earthquake engineering andEngineering Vibration, June, Vol.10, pp. 239-252.

15.Jingsi, H., Yan, X. and Zongjin, L. (2008). Experiment and Analysis of Smart ConcreteBeam Strengthened Using Shape Memory Alloy Wires. Engineering Materials, Vol. 400-

402, pp. 371-377.16.Hui, L., Zhi-qiang, L. and Jin-ping, O. (2006) Behavior of a simple concrete beam driven by

shape memory alloy wires. Smart Material Structures, Vol.15, No.4.


15/15


122

17.Elbahy, Y.I., Youssef, M. A. and Nehdi, M. (2009). Stress block parameters for concreteflexural members reinforced with superelastic shape memory alloys. Materials and

structures, 42:1335-1351.18.Lee, J.J. and Seo, D.C. (2000). A study on the buckling and post buckling control of

composite beams with embedded NiTi actuators. Journal of Composite Materials, 34(17);

pp. 1494-1510.19.Krstulovic-Opara, N. and Naaman, A.E. (2000). Self-stressing fiber composites. ACI

Structural Journal, 97(2), pp. 335-344.

20.DesRoches, R. and Delemont, M. (2002). Seismic retrofit of bridges using shape memoryalloy.Engineering Structures, 24(3), pp. 325-332.

21.Johnson R. Maragakis E., Saiidi. M. (2004).Experimental evaluation of seismic performanceof SMA bridge restrainers. REP. No. CEER 04-02, Center for Civil Engineering Earthquake

Research, Univ. of Nevada, Reno, Nev.22.Youssef MA, Rahman M (2007) Simplified seismic modeling of reinforced concrete

flexural members, Mag Concr. Res. 59(9):639-649

23.Kalkan I., (2010), Deflection prediction for reinforced concrete beams through differenteffective moment of inertia expression,Int. J. Engg. Research & Development, Vol.2, No.1,Jan.2010.

24.American Concrete Institute. ACI (2005), Building Code Requirements for StructuralConcrete (ACI 318-05) and Commentary (ACI R318-05), Farmington Hills. Michigan.

112pp.

25.CEB. Comit Euro-International du Bton. CEB-FIP model code 1990. Lausanne, (1993).

An Experimental Study on Growth of Time-Dependent Strain in Shape Memory Alloy Reinforced Concrete...

Documents

Transcript of An Experimental Study on Growth of Time-Dependent Strain in Shape Memory Alloy Reinforced Concrete...