11_chapter 5_finite Element Analysis Using Ansys

8/12/2019 11_chapter 5_finite Element Analysis Using Ansys

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CHAPTER5

FINITE ELEMENT ANALYSIS USING ANSYS

5.1 Introduction to Ansys

The Finite Element Method (FEM) is a numerical analysis for obtaining approximate

solutions to a wide variety of engineering problems. This has developed simultaneously with

the increasing use of high-speed electronic digital computers and with the growing emphasis

on numerical methods for engineering analysis. Although originally developed to study

stresses in complex airframe structures, it has been extended and applied to the broad field of

continuum mechanics. Because of its diversity and flexibility as analysis tool, it is receiving

much attention in engineering field and in industry. The basic concept behind FEM is that a

body or structure is divided into smaller elements of finite dimensions called finite

elements. The original structure is then considered as an assemblage of these elements at a

finite number of joints called nodes.

The properties of the elements are formulated and combined to obtain the solution for

the entire structure. The shape functions are chosen to approximate the variation of

displacement within an element in terms of displacement at the nodes of the element. The

strains and stresses within an element will also be expressed in terms of the nodal

displacement. The principle of virtual displacement is used to derive the equations of

equilibrium for the element and the nodal displacement will be the unknowns in the

equations.

The ANSYS computer program is a general purpose Finite Element Modeling

Package for numerically solving a variety of engineering problems. These problems include

static and dynamic structural analysis (both linear and non linear), steady state and transient

heat transfer problems, mode-frequency and buckling analyses, acoustic and electro magnetic

problems and various types of field and coupled-field applications. The program contains

many special features which allow nonlinearities or secondary effects to be included in the

solution such as plasticity, large strain, hyper elasticity, creep, swelling, large deflections,

contact, stress stiffening, temperature dependency, material anisotropy and radiation.

As ANSYS has been developed, other special capabilities, such as sub structuring,

submodeling, random vibration, kinetostatics, kinetodynamics, free convection fluid analysis,

acoustics, magnetics, piezoelectrics, coupled-field analysis and design optimization have


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been added to the program. These capabilities contribute further to making ANSYS a multi-

purpose analysis tool for varied engineering applications.

5.2 Element Types

Selection of proper element types is an important criterion in Finite Element

Analysis. For beam-column joints the Concrete portion was modeled by using a special

element available in the package particularly for Concrete namely SOLID 65 element. The

reinforcement was modeled by using LINK 8 element. The details of both the elements used

in the analysis are explained below briefly.

5.2.1 Solid 65

SOLID 65 elements are used to model reinforced concrete members or reinforced

composite materials, such as fiber glass. This element has eight nodes, with each node having

three translational degrees of freedom in the nodal X, Y & Z directions as shown in Fig. 5.1.

The element may be used to analyze cracking in tension and crushing in compression. The

element itself is used to analyze problems with or without reinforced bars. Up to three rebar

specifications may be defined. The rebar facility can be removed by assigning the volume

ratio as zero.

Fig 5.1 SOLID 65 Element

5.2.2 Link 8

LINK 8 is a spar, which may be used in a variety of engineering applications.

Depending upon the applications, the element may be thought of as a truss element, a cable

element, a reinforcing bar and a bolt. The three-dimensional spar element is having two

nodes and each node having three translational degrees of freedom. This element is capable


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of plasticity, creep, swelling and stress stiffening effects. The cross sectional area can be

given as the real constant. This element is shown in Fig 5.2.

Fig. 5.2 LINK 8 Element

5.2.3 SOLID 45

SOLID 45 is a three-dimensional brick element used to model isotropic solid

problems. It has eight nodes, with each node having three translational degrees of freedom inthe nodal X, Y & Z directions. This element may be used to analyze large deflection, large

strain, plasticity and creep problems. It has no real constants. This element is illustrated in

Fig 5.3

Fig 5.3 SOLID 45 Element

5.3 Non-Linear Material Model for Concrete

Material plays an important role in ANAYS modeling. Correct values of material

properties have to be given as input in ANSYS. Cube compressive strength and Yield

strength of reinforcing bars are found experimentally and these values are given as inputs.

The challenging task in modeling the Beam -Column joints is the development of the

behavior of concrete. Concrete is purely non-linear material and it has different behavior in


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compression and tension. The tensile strength of concrete is typically 8% to 15% of the

compressive strength. Fig. 5.4 shows the typical stress-strain curve for normal weight

concrete. In compression, the stress-strain curve of concrete is linearly elastic up to about

30% of the maximum compressive strength. Above this point, the stress increases gradually

up to the maximum compressive strength, and then descends into a softening region, and

eventually crushing failure occurs at an ultimate strain cu. In tension, the stress-strain curve

for concrete is approximately linearly elastic up to the maximum tensile strength. After this

point, the concrete cracks and the strength decreases gradually to zero. ANSYS has its own

non-linear material model for concrete. Its reinforced concrete model consists of a material

model to predict the failure of brittle materials, applied to a three-dimensional solid element

in which reinforcing bars may be included. The material is capable of cracking in tension and

crushing in compression. It can also undergo plastic deformation and creep. Three different

uniaxial materials, capable of tension and compression only, may be used as a smeared

reinforcement, each one in any direction. Plastic behavior and creep can be considered in the

reinforcing bars too. For plain cement concrete model, the reinforcing bars can be removed.

Fig 5.4 StressStrain Curve for Concrete

5.4 Finite Element Modeling of Beam Column Joints

Modeling is one of the important features in Finite Element Analysis. It takes around

40% to 60% of the total solution time. Improper modeling of the structures leads to the

unexpected errors in the solution. Hence, proper care should be taken for modeling the

structures. A good idealization of the geometry reduces the running time of the solution

considerably. In many situations, a three dimensional structure can easily be analyzed by

considering it as a two dimensional structure without any loss of accuracy. Creative thinking


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in idealizing and meshing of the structure helps not only in reducing considerable amount of

time but also in reducing the memory requirement of the system. Finite Element modeling of

beam-column joints in ANSYS consist of three stages, which are listed below.

Selection of element type

Assigning material properties

Modeling and meshing the geometry

After going through literature and after several initial trials, the elements for modeling

various materials were finalized and the details of elements used are shown in Table 5.1

Table 5.1 Details of Element

S.No Material ANSYS Element

1 Concrete Solid 65

2. Steel Link 8

3. FRP Sheet Solid 45

The typical views of the reinforcements detailed as per code IS 456:2000 and IS 13920:1993

generated by the Ansys program are shown in Fig. 5.5 and Fig. 5.6 respectively. Typical

views of the control and retrofitted beam column joints generated by the Ansys program are

shown in Fig. 5.7 and Fig. 5.8 respectively.

Fig 5.5 Typical View of Reinforcement Detail as per Code IS 456:2000


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Fig 5.6Typical View of Reinforcement Detail as per Code IS 13920:1993

Fig 5.7Typical View of Model of a Control Beam-Column Joint


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Fig 5.8Typical View of Model of a Retrofitted Beam-Column Joint

5.5 Stress-Strain Relationship for Concrete

As per the Ansys concrete model, two shear transfer coefficients, one for open cracks

and other for closed ones, are used to consider the amount of shear transferred from one end

of the crack to other. Following are the input data required to create the material model for

concrete in Ansys.

Elastic Modulus, (Ec)

Poissons Ratio, ()

Ultimate Uniaxial compressive strength, (fc)

Ultimate Uniaxial tensile strength, (ft)

Shear transfer coefficient for opened crack, (0)

Shear transfer coefficient for closed crack, (c)The equations are used to estimate the values of Ecand ftas follows,

Ec = 5000 fc

ft = 0.7 fc

Where, Ec, fc and ft are in MPa.


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Poissons ratio for concrete is assumed to be 0.2 for all the specimens. Damien Kachlakev

et.al. conducted numerous investigations on full-scale beams and the value of the shear

transfer coefficient for opened crack was found to be 0.2 and for closed crack the value was

found to be 1. Even though the above parameters are adequate for the non-linear modeling of

concrete, it is better to give the value of stress and strain in the form of stress-strain curve for

achieving better accuracy in results. A typical stress-strain curve for concrete is shown in Fig.

5.9

Fig 5.9 Simplified Compressive Uniaxial Stress-Strain Curve for Concrete

The stress-strain curve for concrete can be constructed by using the Desayi and Krishnan

equations. Multi-linear kinematic behavior is assumed for the stress-strain relationship of

concrete. It is assumed that the curve is linear up to 0.3 fc. Therefore, the elastic stress-strainrelation is enough for finding out the strain value.

1 = fc1/ Ec = (0.3 fc)/ Ec

The Ultimate strain can be found out from the following formula.

0 = 2 fc/ Ec

The total strain in the non-linear region is calculated and corresponding stresses for

the strains are found out by using the following formula.

fc(2 , 3 & 4)= (Ec )/(1+ ( / 0)2)

The above input values are given as material properties for concrete to define the non-

linearity.

5.6 Non-Linear Modeling of Steel

Steel reinforcement in the experimental programme consisted of Fe 415 bars.

Properties like youngs modulus and yield stress, for the steel reinforcement used in this


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FEM study are found out by conducting the required tests on the sample specimens. The steel

for the finite element models is assumed to be an elastic-perfectly plastic material and

identical in tension and compression. Poissons ratio of 0.3 is used for the steel reinforcement

in this study. Fig. 5.10 shows the stress-strain relationship used in the modeling.

Fig 5.10Stress - Strain Curve for Steel

5.7 Finite Element Discretization

The first step in finite element analysis after the creation of the model is meshing. In

other words, the model is divided into a number of finite elements. After the application of

loads, stresses and strains are calculated at integration points of these small elements. An

important step in finite element modeling is the selection of the mesh density. A convergence

of results is obtained when an adequate number of elements are used in a model. The

accuracy of the results is directly proportional to the number of elements chosen. However, if

the number of elements goes beyond a limit, the running time to get a solution becomes more

and Convergence problems may also arise. Thus there exist an optimum number of elements

using which one can get reliable and accurate results.

5.8 Application of Loads and Boundary Condition

Displacement boundary conditions are needed to constrain the model to get a unique

solution. To ensure that the model acts the same way as the experimental beam boundary

conditions need to be applied at points of symmetry, and where the supports and loadings

exist. Both the column ends were provided with hinged boundary conditions. At one of the

column ends, a constant load was applied. A transverse load was applied at the free end of


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the beam. The load applied for model detailed as per code IS 456:2000, which is taken from

experimental investigation for a controlled deflection. Same load was applied in the model

detailed as per code 13920:1993. The material properties for reinforcement concrete are

given in Table 5.2

Table.5.2Material Properties of Reinforced Concrete

ELEMENT TYPE MATERIAL PROPERTY

Solid 65 Modulus of elasticity 2.5 x 10 N/m

Passion ratio 0.23

Density 25000 N/m

Link 8 Modulus of elasticity 2.1 x 10 N/m

Passion ratio 0.3

Density 78500N/m

During the present study twelve exterior reinforced concrete beam-column joint

specimens were modeled using Ansys software. Out of these twelve models, one had

reinforcement details as per code IS 456:2000 and another had reinforcement details as per

code IS 13920:1993. Third model had reinforcement details as per code IS 456:2000 and was

retrofitted with GFRP sheets. Fourth model had reinforcement details as per code IS

456:2000 and was retrofitted with AFRP sheets. Fifth model had reinforcement details as per

code IS 456:2000 and was retrofitted with CFRP sheets. Sixth model had reinforcement

details as per code IS 456:2000 and was retrofitted with sisal fiber sheets. Seventh model had

reinforcement details as per code IS 456:2000 and was retrofitted with glass-carbon hybrid

fiber reinforced polymer sheets. Eighth model had reinforcement details as per code IS

456:2000 and was retrofitted with carbon-glass hybrid fiber reinforced polymer sheets. Ninth

model had reinforcement details as per code IS 456:2000 and was retrofitted with glass-

aramid hybrid fiber reinforced polymer sheets. Tenth model had reinforcement details as per

code IS 456:2000 and was retrofitted with aramid-glass hybrid fiber reinforced polymer

sheets. Eleventh model had reinforcement details as per code IS 456:2000 and was retrofitted

with carbon-aramid hybrid fiber reinforced polymer sheets. Twelveth model had

reinforcement details as per code IS 456:2000 and was retrofitted with aramid-carbon hybrid

fiber reinforced polymer sheets. Both the ends of column were hinged during the analysis.

Static load was applied at the free end of the cantilever beam. The load was increased in steps

up to a controlled load. Nonlinear analysis was carried out for beam-column specimens. The


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performance of the retrofitted beam-column joints predicted by the Ansys model was

compared with the experimental results and the details are presented in this chapter.

5.9 Results and Discussion

5.9.1 Ansys Modelling of Beam-Column Joint Specimen Retrofitted with GFRP Sheets

A typical out put of the Ansys modeling for the beam-column joint specimen (BCJ 2)

detailed as per code IS 456:2000 is shown in Fig 5.11. The output of the Ansys modeling for

the beam-column joint specimen (BCJ 5) detailed as per code IS 13920:1993 for a given load

is shown in Fig 5.12. The out put of the Ansys modeling of the beam-column joint specimen

(BCJ 8) detailed as per code IS 456:2000 and was retrofitted with GFRP sheets for the same

given load is shown in Fig 5.13.

Fig.5.11 Ansys Model for the Beam-Column Joint Specimen BCJ 2



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The results of the Ansys analysis are compared with that of the experimental investigation.

The percentage error between experimental results and Ansys results for the M 20 concrete

control and retrofitted (GFRP) beam-column joint specimens are given in Table 5.3

Table 5.3 Percentage Error between Experimental Results and Ansys Results for M 20

Concrete Beam-Column Joint Specimens Retrofitted with GFRP Sheets

Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 2 456 NIL 45 42 6.67

BCJ 5 13920 NIL 35 32 8.57

BCJ 8 456 GFRP 13 15 1.33

From Table 5.3, it is seen that the variations between the Ansys results andexperimental results were found to be less than 10 %. Fig. 5.14 shows the load deflection

curve of the beam-column joint specimens BCJ2, BCJ 5 and BCJ 8.

Fig.5.14 Load-Deflection Curve for the Beam-ColumnJoint Specimens BCJ 2, BCJ 5 and BCJ 8


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From Fig 5.14, it is seen that the deflection of the specimen detailed as per code IS

456:2000 is found to be maximum for a given load. The deflection of the beam-column joint

specimen detailed as per code IS 13920:1993 is less than that of the specimen detailed as per

code IS 456:2000. The deflection of the beam-column joint specimen retrofitted with GFRP

sheets is the least for a given load.

A typical out put of the Ansys modeling for the beam-column joint specimen (BCJ

38) detailed as per code IS 456:2000 is shown in Fig 5.15. The out put of the Ansys modeling

of the beam-column joint specimen (BCJ 41) detailed as per code IS 13920:1993 is shown in

Fig 5.16. The out put of the Ansys modeling of the beam-column joint specimen (BCJ 44)

detailed as per code IS 456:2000 and was retrofitted with GFRP sheets is shown in Fig 5.17.




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Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 38 456 NIL 61 56 8.20

BCJ 41 13920 NIL 49 45 8.16

BCJ 44 456 GFRP 30 32 6.25

From Table 5.4, it is seen that the variations between the Ansys results and experimentalresults were found to be less than 10 %. Fig. 5.18 shows the load deflection curve of the

beam-column joint specimens BCJ 38, BCJ 41 and BCJ 44.

Fig.5.18 Load-Deflection Curve for the Beam-ColumnJoint Specimens BCJ 38 , BCJ 41 and BCJ 44


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A typical ut put for the Ansys modeling of the beam-column joint specimen (BCJ 74)

detailed as per code IS 456:2000 is shown in Fig 5.19. The out put of the Ansys modeling of

the beam-column joint specimen (BCJ 77) detailed as per code IS 13920:1993 is shown in

Fig 5.20. The out put of the Ansys modeling of the beam-column joint specimen (BCJ 80)

detailed as per code IS 456:2000 and was retrofitted with GFRP sheets is shown in Fig 5.21.




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Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 74 456 NIL 75 70 6.67

BCJ 77 13920 NIL 60 62 3.23

BCJ 80 456 GFRP 52 56 7.15

From Table 5.5 it can be seen that the percentage error is less than 10%. Hence the results of

the Ansys modeling can be used to understand the performance of beam-column joint

specimens made with other grades also which are retrofitted with glass fiber polymer sheets.

Fig. 5.22 shows the load deflection curve of the beam-column joint specimens BCJ 74 , BCJ

77 and BCJ 80.

Fig. 5.22 Load-Deflection Curve for M 30 Concrete Specimens Retrofitted with GFRP


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Fig.5.23 show a typical view of analyzed M 35 concrete beam-column joint specimen

detailed as per code IS 456:2000. Fig.5.23 show a typical view of analyzed M 35 concrete

beam-column joint specimen detailed as per code IS 13920:1993. Fig.5.24 show a typical

view of analyzed M 35 concrete beam-column joint specimen detailed as per code IS

456:2000 retrofitted with glass fiber reinforced polymer sheets.

Fig.5.23 Ansys Model for M 35 Concrete Beam-Column Joint Specimen

Reinforcement Detailing as per IS 456 : 2000

Fig.5.24 Ansys Model for M 35 Concrete Beam-Column Joint SpecimenReinforcement Detailing as per IS 13920 :1993


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Retrofitted with GFRP Sheets

Fig.5.26 shows the load deflection curve of the M 35 concrete beam-column joint specimens

retrofitted with GFRP sheets.











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Fig.5.28 Ansys Model for M 40 Concrete Beam-Column Joint SpecimenReinforcement Detailing as per IS 13920 : 1993




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retrofitted with GFRP sheets.












Fig.5.31 Ansys Model for the M 45 Concrete Beam-Column Joint Specimen



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Fig.5.33 Ansys Model for the M 45 Concrete Beam-Column Joint SpecimenRetrofitted with GFRP Sheets

Fig.5.34 show the load deflection curve of the M 45 concrete beam-column joint specimens

retrofitted with GFRP sheets

Fig.5.34 Load-Deflection Curve for M 45 Concrete Specimens Retrofitted with GFRP


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beam-column joint specimen detailed as per code IS 13920:1993. Fig.5.37 show a the typical



Fig.5.35 Ansys Model for the M 50 Concrete Beam-Column Joint SpecimenReinforcement Detailing as per IS 456: 2000




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retrofitted with GFRP sheets

Fig.5.38 Load-Deflection Curve for M 50 Concrete Specimens Retrofitted with GFRP





sheets is the least for a given load.5.9.2 Ansys Modelling of Beam-Column Joint Specimen Retrofitted with AFRP Sheets

A typical out put the Ansys modeling for the M 20 concrete beam-column joint

specimen (BCJ 11) detailed as per code IS 456:2000 and was retrofitted with AFRP sheets is

shown in Fig 5.39.


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Fig.5.39 Ansys Model for M 20 Concrete Beam-Column Joint

Specimen Retrofitted with AFRP Sheet



beam-column joint specimens retrofitted with AFRP sheets are given in Table 5.6


Concrete Beam-Column Joint Specimens Retrofitted with AFRP Sheets

Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 2 456 NIL 45 42 6.67

BCJ 5 13920 NIL 35 32 8.57

BCJ 11 456 AFRP 12 13 7.69

From Table 5.6, it is seen that the variations between the Ansys results and experimental

results were found to be with in 10 %.The load-deflection curve for the M 20 concrete beam-

column joint specimen retrofitted with AFRP sheets is shown in Fig.5.40

Fig 5.40 LoadDeflection Curve for M 20 Concrete Beam-Column JointSpecimen Retrofitted with AFRP Sheets.


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code IS 456:2000. The deflection of the beam-column joint specimen retrofitted with AFRP


A typical out put of the Ansys modeling of the M 25 concrete beam-column joint


shown in Fig 5.41.







Concrete Beam-Column Joint Specimens Retrofitted with AFRP Sheets

SpecimenID

Codeas per

Retrofittedby

Deflection as perexperiment in mm

Def. as perAnsys in mm

% error inresult

BCJ 38 456 NIL 61 56 8.20

BCJ 41 13920 NIL 49 45 8.16

BCJ 47 456 AFRP 26 24 7.70


results were found to be less than 10 %.The load-deflection curve for the M 25 concrete

beam-column joint specimen retrofitted with AFRP sheets is shown in Fig.5.42


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Fig.5.42 Load-Deflection Curve for M 25 Concrete Specimens

Retrofitted with AFRP Sheets








shown in Fig 5.43

Fig.5.43 Ansys Modeling for M 30 Concrete Beam-Column Joint



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Concrete Beam-Column Joint Specimens Retrofitted with AFRP SheetsSpecimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 74 456 NIL 75 70 6.67

BCJ 77 13920 NIL 60 62 3.23

BCJ 83 456 AFRP 52 55 5.45

From the Table 5.8 it can be seen that the percentage error is less than 10%. The load-

deflection curve for the M 30 concrete beam-column joint specimen retrofitted with AFRP

sheets is shown in Fig.5.44






code IS 456:2000. The deflection of the beam-column joint specimen retrofitted with AFRPsheets is the least for a given load.

Fig.5.45 show a typical view of analyzed M 35 concrete beam-column joint

specimen detailing as per code IS 456:2000 retrofitted with aramid fiber reinforced polymer

sheets.


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Fig.5.45 Ansys Model for M 35 Concrete Beam-Column JointSpecimen Retrofitted with AFRP Sheet


retrofitted with AFRP sheets

Fig.5.46 Load-Deflection Curve for M 35 Concrete Beam-Column JointSpecimens Retrofitted with AFRP Sheets







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detailing as per code IS 456:2000 retrofitted with aramid fiber reinforced polymer sheets.

Fig.5.47 Ansys Model of M 40 Concrete Beam-Column JointSpecimen Retrofitted with AFRP Sheet











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Fig.5.50 Load-Deflection Curve for M 45 Concrete Beam-Column Joint

Specimens Retrofitted with AFRP Sheets







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Fig.5.51 Ansys Model of M 50 Concrete Beam-Column Joint





Specimens Retrofitted with AFRP Sheets





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5.9.3 Ansys Modelling of Beam-Column Joint Specimen Retrofitted with CFRP Sheets


specimen (BCJ 14) detailed as per code IS 456:2000 and was retrofitted with CFRP sheets is

shown in Fig 5.53.


Specimen Retrofitted with CFRP Sheet

The results of the Ansys analysis arre compared with that of the experimentalinvestigation. The percentage error between experimental results and Ansys results for the M

20 concrete beam-column joint specimens retrofitted with CFRP sheets are given in Table

5.9

Table 5.9 Percentage Error between Experimental Results and

Ansys Results for M 20 Concrete Beam-Column Joint Specimens

Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 2 456 NIL 45 42 6.67

BCJ 5 13920 NIL 35 32 8.57BCJ 14 456 CFRP 11 10 9.10

From Table 5.9, it is seen that the variations between the Ansys results and

experimental results were found to be less than 10 %.The load-deflection curve for the M 20

concrete beam-column joint specimen retrofitted with CFRP sheets is shown in Fig.5.54


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Fig 5.54 LoadDeflection Curve M 20 Concrete Beam-Column JointSpecimen Retrofitted with CFRP Sheets.








shown in Fig 5.55.

Fig.5.55 Ansys Model of M 25 Concrete Beam-Column Joint



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The results of the Ansys analysis arre compared with that of the experimental investigation.


beam-column joint specimens retrofitted with CFRP sheets are given in Table 5.10


Concrete Beam-Column Joint Specimens Retrofitted with CFRP SheettsSpecimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 38 456 NIL 61 56 8.20

BCJ 41 13920 NIL 49 45 8.16

BCJ 50 456 CFRP 22 20 8.69


results were found to be less than 10 %.The load-deflection curve for the M 25 concrete

beam-column joint specimen retrofitted with CFRP sheets is shown in Fig.5.56

Fig 5.56 LoadDeflection Curve M 25 Concrete Beam-Column JointSpecimen Retrofitted with CFRP Sheets.







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shown in Fig 5.57.

Fig.5.57 Ansys Model for M 30 Concrete Beam-Column JointSpecimen Retrofitted with CFRP Sheet

The results of the Ansys analysis arre compared with that of the experimental investigation.


beam-column joint specimens retrofitted with CFRP sheets are given in Table 5.11


Concrete Beam-Column Joint Specimens Retrofitted with CFRP Sheets

Specimen

ID

Code

as per

Retrofitted

by

Deflection as per

experiment in mm

Def. as per

Ansys in mm

% error in

result

BCJ 74 456 NIL 75 70 6.67

BCJ 77 13920 NIL 62 60 3.23

BCJ 86 456 CFRP 42 39 7.14

From the Table 5.11 it can be seen that the percentage error is less than 10%. Hence

the results of the Ansys modeling can be used to understand the performance of beam-column joint specimens made with other grades also which are retrofitted with carbon fiber

reinforced polymer sheets.The load-deflection curve for the M 30 concrete beam-column

joint specimen retrofitted with CFRP sheets is shown in Fig.5.58


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Fig 5.58 LoadDeflection Curve M 30 Concrete Beam-Column Joint

Specimen Retrofitted with CFRP Sheets.







detailing as per code IS 456:2000 retrofitted with carbon fiber reinforced polymer sheets.




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Fig.5.60 shows the load deflection curve of the M 35 concrete beam-column joint

specimens retrofitted with CFRP sheets


Specimens Retrofitted with CFRP Sheets











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sheets is the least for a given load.Fig.5.65 show a typical view of analyzed M 50 concrete beam-column joint specimen


Fig.5.65 Ansys Model for M 50 Concrete Beam-Column JointSpecimen Retrofitted with CFRP Sheet


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5.9.4 Effect of Grade of Concrete on Load Carrying Capacity of Beam-Column Joint

Specimens

The effect of grade of comcrete on the load carrying capacity of beam-column joint

specimen has been investigated experimentally and using Ansys software. Experimental

investigation was carried out on nine beam-column joint specimens. Three specimens made

of grade M20, M25and M30 retrofitted with glass fiber reinforced polymer (GFRP) sheets

were tested. The other three specimens made of concrete of grade M20, M25and M30

retrofitted with aramid fiber reinforced polymer (AFRP) sheets. The remaining speciemens

made of concrete of grade M20, M25 and M30 retrofitted with carbon fiber reinforced

polymer (CFRP) sheets.The experimental results were compared with that Ansys results and

the variation in load carrying capacity predicted by Ansys model was found to be 1% to 9%.


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Hence it is sassumed that the results of the Ansys analysis are reliable. Ansys model was

used to estimate the load carrying capacity of beam-column joint specimens for the concrete

greade of M35, M40, M45 and M50.

The results of the Ansys model and the experimental investigation for the beam-

column joint specimens retrofitted with GFRP sheets are shown in Fig 5.67

Fig 5.67 Load Carrying Capacity Vs Grade of Concrete for

Beam-Column Joint Specimens Retrofitted with GFRP Sheets

From Fig.5.67 it is found that the load carrying capacity of beam-column joint

specimens retrofitted with glass fiber reinforced polymer sheets increases nonlinearly with

respect the grade of concrete. The load carrying capacity of the beam-column joint specimens

retrofitted with GFRP sheets can be estimated using the equation y = -0.0011x3+0.1248x

2-

3.8193x +57.214 were x is the grade of concrete.

The results of the Ansys model and the experimental investigation for the beam-

column joint specimens retrofitted with AFRP sheets are shown in Fig 5.68


42/43


43/43

From Fig.5.69 it is found that the load carrying capacity of beam-column joint

specimens retrofitted with carbon fiber reinforced polymer sheets increases nonlinearly with

respect the grade of concrete. The load carrying capacity of the beam-column joint specimens

retrofitted with CFRP sheets can be estimated using the equation y = -0.0004x3- 0.0538x2-

1.5341x + 41.69 were x is the grade of concrete.

The deflection at the free end of the beam-column joint when the applied load was 30

kN were found for various grades of concrete and for various types of wrapping sheets. The

variations of deflection with respect to the grade of concrete are shown in Fig.5.70

Fig.5.70 Deflection Vs Grade of Concrete for

Beam-Column Joint Specimens Retrofitted with FRP Sheets

From the Fig.5.70, it is seen that the deflection at the free end of the beam-column

joints were found to decrease as the grade of concrete increase. It also seen that the changes

in the value of deflection tent to reduce beyond M35 concrete. This shows that grade superior

than M35 may not be required for beam-column joint.

It is also seen that GFRP resulted in maximum deflection where as CFRP gives least

deflection. The percentage reduction in deflection values ranges between 7 % to 47 % when

AFRP sheets are used instead of GFRP sheets. The percentage reduction in deflection values

ranges between 27 % to 75 % when GFRP sheets are replaced with CFRP sheets.

11_chapter 5_finite Element Analysis Using Ansys

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