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CHAPTER 5

ANALYTICAL INVESTIGATION ON EXTERIOR

BEAM-COLUMN JOINTS

5.1 GENERAL

Different methods have been utilized to study the response of

structural components. Experimental based testing has been widely used as a

means to analyze individual elements and the effects of concrete strength

under loading. While this is a method that produces real life response, it is

extremely time consuming, and the use of materials can be quite costly. But

with the help FEA software versatile analysis is possible for any number of

samples. The use of finite element analysis to study these components has

been used. Finite Element Analysis can be used more efficiently to predict the

behaviour with small acceptable approximations. The use of computer

software to model these elements is much faster, and extremely cost-effective.

Analysis using cyclic load will be useful to predict the seismic behaviour of

the precast beam-column connections. Results from this work will be useful

in implementing the most efficient precast beam-column joint in construction

industry.

A three storied R.C building with exterior beam-column joint is

modeled, analysed and designed as mentioned in the Chapter 3. An exterior

beam-column joint in the first storey (marked A in Figure 3.1) is subjected to

experimental investigation. A scale factor of three has been adopted for both

experimental and finite element model. The original structure has been

reduced three times using the laws of similitude (Cauchy’s Similitude Laws).

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In this chapter, the finite element modeling of the exterior beam-column joint

has been done and the response of the joint under cyclic loading is obtained

and the results thereof are presented and discussed.

5.2 FINITE ELEMENT MODELLING

The one third scale model of exterior beam-column joint has been

modeled and analysed using the finite element software package ANSYS

(Version 10). ANSYS is the commonly used finite element analysis software

that for the research oriented studies. The elements adopted to model

concrete, reinforcement, bolt shank and nut, grout material and loading plate

are given in Table 5.1.

Table 5.1 Elements used in ANSYS

Material ANSYS ElementConcrete SOLID65Reinforcement LINK8Bolt shank and nut LINK10Grout material CONTA174 and TARGE170Steel plates, supports and angles SOLID45

5.2.1 Features of SOLID65 Element

SOLID65 is used for the 3-D modeling of solids with or without

reinforcing bars (rebar). The element is defined by eight nodes. There are

three degrees of freedom at each node which include translations in the nodal

x, y, and z directions. The solid is capable of cracking in tension and crushing

in compression. In concrete applications, for example, the solid capability of

the element may be used to model the concrete while the rebar capability is

available for modeling reinforcement behavior. The most important aspect of

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this element is the treatment of nonlinear material properties. The concrete is

capable of cracking (in three orthogonal directions), crushing, plastic

deformation, and creep. The rebar are capable of tension and compression.

The geometry, node locations and the coordinate system for SOLID65

element is shown in Figure 5.1.

Figure 5.1 SOLID65 Element (ANSYS 2006)

5.2.2 Features of LINK 8 Element

LINK8 is a spar which may be used in a variety of engineering

applications. This element can be used to model links, trusses, sagging cables

and springs. The 3-D spar element is a uniaxial tension-compression element.

Three degrees of freedom at each node: translations in the nodal x, y, and z

directions. Plasticity, creep, swelling, stress stiffening, and large deflection

capabilities are included. The element is defined by two nodes, the cross-

sectional area, an initial strain, and the material properties. The element x-axis

is oriented along the length of the element from node i toward node j. The

initial strain in the element (ISTRN) is the difference between the element

length, L, (as defined by the i and j node locations) and the zero strain length.

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The geometry, node locations and the coordinate system for LINK8 element

is shown in Figure 5.2.

Figure 5.2 LINK8 Element (ANSYS 2006)

5.2.3 SOLID45 Element

The element SOLID45 is used for the steel plates at the supports

and point of load application in order to avoid stress concentration problems.

This provided a more even stress distribution over the support area. It is also

used to model cleat angles. SOLID45 element is defined by eight nodes with

three degrees of freedom at each node, translations in the nodal x, y and z

directions. The element has plasticity, creep, swelling, stress stiffening, large

deflection, and large strain capabilities. The geometry, node locations and the

coordinate system for SOLID45 element is shown in Figure 5.3.

Figure 5.3 SOLID45 Element (ANSYS 2006)

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5.2.4 CONTA174 Element and TARGE170 Element

CONTA174 is used to represent contact and sliding between 3-D

“target” surfaces defined by this element. Contact occurs when the element

surface penetrates one of the target segment elements (TARGE170) on a

specified target surface. The element is defined by eight nodes (the underlying

solid or shell element has mid side nodes). The geometry, node locations and

the coordinate system for CONTA174 element is shown in Figure 5.4.

Figure 5.4 CONTA174 Element (ANSYS 2006)

CONTA174 element supports isotropic and orthotropic Coulomb

friction. The 3-D contact element must coincide with the external surface of

the underlying solid or shell element can use this element in nonlinear static

or nonlinear full transient analysis. TARGE170 element is used to represent

various 3-D “target” surfaces for the associated contact elements. The contact

elements themselves overlay the solid elements describing the boundary of a

deformable body and are potentially in contact with the target surface, defined

by TARGE170 element. This target surface is discretized by a set of target

segment elements (TARGE170) and is paired with its associated contact

surface via a shared real constant set. It can impose any translational or

rotational displacement, temperature, voltage, and magnetic potential on the

target segment element. It can also impose forces and moments on target

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elements. For rigid target surfaces, these elements can easily model complex

target shapes. For flexible targets, these elements will overlay the solid

elements describing the boundary of the deformable target body.

5.3 SECTIONAL PROPERTIES (REAL CONSTANTS)

Reinforcement can be modelled as the discrete model, embedded

model and smeared model (Tavarez 2001). Fanning (2001) modeled the

response of the reinforcement using the discrete model and the smeared

model for reinforced concrete beams. It was found that the best modeling

strategy was to use the discrete model when modeling reinforcement. The

smeared reinforcement capacibilty of the SOLID65 element is turned off for

real constant set 1 (volume ratio and orientation angle were set to zero). The

parameters considered for LINK8 element are cross sectional area and initial

strain. The real constant values for LINK8 element used for modeling the

models are given in Table 5.2.

Table 5.2 Real Constant for LINK8 Element

Real ConstantSet Element Type Particulars of the Model

2Link8(Longitudinalreinforcement of beamand main reinforcementof column)

Cross sectionalarea(m2)

7.85x10-5

Initial Strain 0

3Link8(Transversereinforcement of beam)

Cross sectionalarea(m2)

7.07x10-6

Initial Strain 0

4Link8(Transverse hoops ofcolumn)

Cross sectionalarea(m2)

12.57x10-5

Initial Strain 0

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5.4 MATERIAL PROPERTIES

Three model properties are important to simulate perfect concrete

behaviour in ANSYS. They are

Elastic property

Compressive Uniaxial Stress-Strain Relationship for Concrete

Cracking behaviour

5.4.1 Elastic Property

“EX “is the modulus of elasticity of the material considered and

“PRXY” is the Poisson’s ratio. The characteristic compressive strength of the

concrete considered is (fc’) 33.28 N/mm2 which was obtained from

experiments and the Poisson’s ratio was 0.15.

Ec =57000 fc’ = 57000 33.28 = 27308.7 N/mm2

5.4.2 Compressive Uniaxial Stress-Strain Relationship for Concrete

Stress strain values are given to simulate the multi-linear behaviour

of the concrete. The multi-linear stress-strain curve for concrete under

compressive uniaxial loading is obtained using Equations (5.1) and (5.2)

(Desai and Krishnan 1964), and Equation (5.3) for modeling of concrete.

Ultimate strain is calculated by

2

1

c

o

Ef (5.1)

'2 co

c

fE

(5.2)

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cfE (5.3)

where 'cf - stress at any strain , psi

- strain at stress f

o - strain at the ultimate compressive strength 'cf

For the multi-linear stress strain curve of concrete, the first stress-

strain value corresponds to elastic limit value. i.e., 1/3rd of the 'cf using

Equation (5.3).The intermediate points are calculated from the Equation (5.1)

and (5.2). Strains are selected and the stress is calculated for each strain. The

final point is crushing strain for unconfined concrete.

5.4.2.1 Concrete Failure Criteria

The model is capable of predicting failure for concrete materials.

Both cracking and crushing failure modes are accounted for. The two input

strength parameters i.e., ultimate uniaxial tensile and compressive strengths –

are needed to define a failure surface for the concrete. Consequently, a

criterion for failure of the concrete due to a multi-axial stress state can be

calculated (William and Warnke 1975). An isotropic multi-linear compressive

stress–strain curve for concrete is used to define the plastic behavior of

concrete. Figure 5.5 represents a general 3D failure surface for concrete. The

3D failure surface represents the states of stress that is biaxial or nearly

biaxial and the most significant nonzero principle stresses are in the x and y

directions. When the principal stresses in the x and y directions are both

negative (compressive), the failure mode is a function of the sign of the

principal stress in the z direction, and three failure surfaces are possible as

shown in Figure 5.5, with the principal stresses in the z direction slightly

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greater than zero (cracking), equal to zero (crushing), and slightly less than

zero (crushing). When one or both the principal stresses in x and y directions

are positive (tensile) the failure mode is cracking as shown in Figure 5.5.

Figure 5.5 3D Failure Surface for Concrete (ANSYS 2006)

5.4.2.2 Convergence Criteria for Non-Linear Finite Element Solutions

Finite element analysis executed on computers cannot employ

continuous functions for either analysis over time or non-linear analysis. The

analysis is always performed at discrete steps. In ANSYS, the cyclic load

analysis is carried out by dividing the loading history into a series of

incremental load steps and load substeps. The finite element package applies

the load in a particular load step and at the end of the load step adjusts the

stiffness matrix to reflect the no-linear changes in that load step (ANSYS,

2006). Then the next load step is applied and at the end of the analysis the

stiffness matrix is adjusted to reflect the non-linear changes in that load step.

Thus, the analysis continues throughout the given loading history.

It shall be noted that the non-linear behaviour of the concrete and

steel reinforcements and loss of stiffness in the materials, the generation of

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the cracks and their propagation make the convergence of the model difficult.

The convergence is carried out by employing Newton-Raphson equilibrium

iterations in ANSYS (2006). Usually 30 iterations are specified for the

Newton-Raphson equilibrium iterations to converge to the solution.

Convergence tolerances are also specified to control the iterative convergence

procedure. ANSYS (2006) uses a convergence tolerance default values of

0.5% for force checking and 5% for displacement checking and the same was

used for the analysis in the present work for the initial part of the loading

history. Later, the nonlinear behaviours dominant and it is difficult for the

convergence algorithm to satisfy the stringent convergence criteria. The

criteria are slightly relaxed to 2.5% for the force checking criterion and upto

10% for the displacement checking criterion. On reaching the failure criterion,

ANSYS (2006) prompts a message specifying divergence of the analysis due

to large deflection exceeding the displacement limitation of the program.

5.4.2.3 Finite Element Discretization

Selection of the mesh density is an important step in finite element

modeling. A convergence of results is obtained when an adequate number of

elements are used in a model. The convergence of results is achieved when an

increase in the mesh density has a negligible effect on the results (Adams and

Askenazi 1998). Therefore, in this finite element modeling study a

convergence study was carried out to determine an appropriate mesh density.

Initially a convergence study was performed using plain concrete beams in a

linear analysis. The finite element models dimensions replicated model beams

of size 550mm x 100mm x100mm. Three plain concrete beams with the same

material properties were modeled in ANSYS, 2006 with 739, 1345, 2876

elements respectively. The deflection at the free of the beam was studied.

These results were compared with theoretical deflection of the beam. The

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results started to converge with a model having 2876 elements. Numbers of

elements used in this study are summarized in Table 5.3.

Table 5.3 Number of Elements used in the Different Specimens

S.No Specimen Number of Elements inANSYS model

1 ML 7829

2 PC-JB 8203

3 PC-TR 8324

4 PC-CL 84775 PC-SS 8629

6 PC-DS 8778

7 PC-DW 82138 PC-DWCL 8239

5.4.3 Cracking Behaviour

Additional concrete material data, such as the shear transfer

coefficient t for open cracks and c for closed cracks are also needed for the

concrete constitutive material data. The shear transfer coefficients t and c

control the amount of shear transfer across the cracks. Typical shear transfer

coefficients range from 0.0 to 1.0, with 0.0 representing a smooth crack

(complete loss of shear transfer) and 1.0 representing a rough crack (no loss

of shear transfer). A value of 0.5 and 0.9 was used in the FE model for t and

c, respectively. Table 5.3 gives the material properties input in ANSYS.

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Table 5.4 Material Properties Input Data for ANSYS*

MaterialModel No.

ElementType Material Properties

1 LINK8

Linear IsotropicEX 199000 N/mm2

PRXY 0.3Bilinear IsotropicYield Stress 443.38 N/mm2

Tangent Modulus 20 N/mm2

2 SOLID65

Linear IsotropicEX 32249 N/mm2

PRXY 0.15Concrete

Shear transfer coefficients for anopen crack 0.5

Shear transfer coefficients for aclosed crack 0.9

Uniaxial tensile cracking stress3.06

N/mm2

Uniaxial crushing stress -1Biaxial crushing stress 0Ambient Hydrostatic stress state 0Biaxial crushing stress underambient hydrostatic stress state 0

Uniaxial crushing stress underambient hydrostatic stress state 0

Stiffness multiplier for crackedtensile condition 0.6

3 SOLID45 Linear IsotropicEX 200000 N/mm2

PRXY 0.3* All other values in the fields are entered as zero.

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5.5 MODELING MONOLITHIC CONNECTION

To model a monolithic beam column, elements to make concrete

and reinforcement are enough i.e., SOLID65 for concrete and LINK8 for

reinforcement. Reinforcement was provided discrete modeling method. i.e.,

The reinforcement in the discrete model uses bar or beam elements that are

connected to concrete mesh nodes. Therefore, the concrete and the

reinforcement mesh share the same nodes and concrete occupies the same

regions occupied by the reinforcement. There are other methods of

reinforcement modeling available like embedded and smeared model. The

discrete model was found to be better than the other two methods as it was

widely adopted by many researches.

5.6 PRECAST BEAM-COLUMN CONNECTIONS

Four Precast beam-column connections were modeled in ANSYS

using similar discrete reinforcement technique as used in monolithic. The

contact faces between corbel and beam and gap between column and beam

face are provided with contact and target elements.

5.6.1 Bolt and Nut Model

There are six different methods to model a bolt and nut. They are

1. No Bolt Simulation

2. Coupled Bolt

3. RBE (Rigid Body Element) Bolt

4. Solid Bolt

5. Hybrid Bolt

6. Spider Bolt

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To model the bolt and dowel bar spider bolt modeling is adopted.

The spider bolt simulation substitutes line elements for the head, nut, and

stud. A series of line elements represent the head/nut in a web-like fashion.

Thus, the name spider bolt. It is the most logical approach to using line

elements and transferring the loads to the stud. The head/nut bending and

stiffness must be simulated by the line elements. A portion of the stud line

elements should be line elements with tension only capability, since no

contact elements are used at the head/nut to flange connection. The Spider

bolt method was adopted here because of its simplicity in modeling and more

over the stresses and behaviour within the cross section of the bolts are out of

the scope of this work, so solid type of 3D bolt model was avoided.

5.6.2 Contact Surfaces

The interfaces of beam and corbel, beam and column gap are

modeled with coinciding node method of surface contacts using CONTA170

and TARGE174 elements. Model was already planned and modeled to have

common ordinate value nodes for beam and corbel.

5.7 BOUNDARY CONDITIONS

5.7.1 Displacement Boundary Conditions

The column is hinged at the base (the translations are restrained x,y

and z directions) whereas the column top is restrained in z- direction. The free

end of the beam is restrained against x-direction. Figure 5.6 shows the

boundary condition of the monolithic specimen.

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Figure 5.6 Monolithic Specimen with Boundary Conditions

5.7.2 Force boundary Conditions

The exterior beam column connection is subjected to reverse cyclic

loading. The command prompt line input data was adopted for applying the

reverse cyclic load in ANSYS. The axial load of column is applied as

pressure. The reverse cyclic loading is applied as displacement controlled

loading as explained in section 4.3.1. The modeling details of the different

connections are shown in Figure 5.7 (a) to (n).

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Figure 5.7(a) Reinforcement details of the Monolithic Specimen with

Solid Plate Element

Figure 5.7(b) Reinforcement Details of the Precast specimen

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Figure 5.7(c) J-Bolt used in Connection PC-JB

Figure 5.7(d) Isometric View of Specimen PC-JB

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Figure 5.7(e) Isometric View of Tie Rod of Specimen PC-TR

Figure 5.7(f) Isometric View of Specimen PC-TR

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Figure 5.7(g) Isometric View of Bolts of Specimen PC-CL, PC-SS and

PC-DS

Figure 5.7(h) Isometric View of Specimen PC-CL

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Figure 5.7(i) Isometric View of Specimen PC-SS

Figure 5.7(j) Isometric View of Specimen PC-DS

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Figure 5.7(k) Isometric View of the Dowel Bar in Specimen PC-DW

Figure 5.7(l) Isometric View of Specimen PC-DW

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Figure 5.7(m) Isometric View of Specimen PC-DWCL

Figure 5.7(n) Isometric View of the Dowel Bar and Bolt in specimenPC-DWCL

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5.8 RESULTS

The finite element analysis was carried out on the one-third scale

model of an exterior beam-column connection. Displacement controlled

loading was applied. The observations were made from the analytical

investigations are presented in the following sections. The parameters

considered for the present study are (i) Ultimate Load Carrying Capacity, (ii)

Cracking Pattern and Failure Mode, (iii)Load-Displacement Hysteretic

Behaviour, (iv) Energy Dissipation, and (v) Displacement Ductility. The

specimens were classified as (i) TYPE I Connection - Bolt and Rod

connections, (ii) TYPE II Connection - Cleat Angle and Stiffened Cleat

Connections and (iii) TYPE III Connection - Dowel Connections.

5.8.1 Load Carrying Capacity

The yield load and ultimate load carrying capacity for the

monolithic and seven precast specimens for both positive and negative

directions of loading are presented in Table 5.5. The particulars pertaining to

each specimen are discussed in the following sections.

5.8.1.1 Monolithic Specimen

The monolithic specimen performed better than all the other precast

specimens. The ultimate load carrying capacity of specimen ML was 13.02kN

and13.55kN in the positive and negative directions respectively.

5.8.1.2 TYPE I Connection: Bolt and Tie Rod connections

It was observed that in the type I connection, specimen PC-TR

exhibited 38.15% and 50.93% more load carrying capacity than specimen

PC-JB. Hence, the specimen with tie rod PC-TR performed well when

compared to the other precast specimen with J-bolt PC-JB. The load carrying

capacity of specimen PC-JB was 57.61% and 59% lesser than the monolithic

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specimen in the positive and negative direction respectively. Specimen

PC-TR showed 31.49% and 16.45% reduction in load carrying capacity when

compared to monolithic specimen ML in positive and negative direction

respectively. In comparison with the precast specimens, the monolithic

specimen performed better in resisting the load.

5.8.1.3 TYPE II Connection: Cleat Angle and Stiffened Cleat

connections

The precast connection with (i) Cleat angle (PC-CL) (ii) Cleat

angle with single stiffener (iii) Cleat angle with double stiffener has been

classified as TYPE II connection. The ultimate load carrying capacity for

specimen PC-DS is 35.61% and 11.62% greater than the specimen PC-SS in

the positive and negative direction respectively. Compared to the monolithic

specimen ML, the specimen PC-DS exhibited only 18.38% and 25.59%

reduction in the load carrying capacity in the positive and negative direction

respectively. It was observed that the load carrying capacity of specimen PC-

CL was 61.65% and 69.53% lesser than the monolithic specimen ML in the

positive and negative direction respectively. Of all three precast specimens,

specimen PC-DS exhibited the best performance.

5.8.1.4 TYPE III Connection: Dowel connections

The precast connection with (i) Dowel bar (PC-DW) (ii) Dowel bar

with cleat angle (PC-DWCL) has been classified as TYPE III connection. The

ultimate load carrying capacity for specimen PC-DWCL is 20.72% and

33.16% greater than the specimen PC-DW in the positive and negative

direction respectively. The load carrying capacity of specimen PC-DW was

43.37% and 49.98% lesser than the monolithic specimen ML in the positive

and negative direction respectively, whereas, specimen PC-DWCL was

28.57% and 25.16% lesser than the monolithic specimen in the positive and

negative direction respectively. The specimen PC-DWCL performed better

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than specimen PC-DW in terms of ultimate load carrying capacity. Figure

5.8(a) and (b) shows then comparison for measured strength in the positive

direction and negative direction respectively. Table 5.6 lists the ultimate

moment carrying capacity for all the specimens.

Table 5.5 Comparison of Analytical Yield and Ultimate Loads for all the

Specimens

Designationof Specimen

Analytical Yield Load(kN)

Analytical Ultimate Load(kN)

Upwarddirection

Downwarddirection

Upwarddirection

Downwarddirection

ML 10.85 11.18 13.02 13.54PC-JB 4.5 4.28 5.52 5.17PC-TR 7 9.82 8.92 11.32PC-CL 3.75 3.48 4.55 4.18PC-SS 5.7 7.9 6.78 9.03PC-DS 8.8 8.4 10.53 10.22PC-DW 5.42 5.59 6.65 6.51PC-DWCL 7.1 8.5 9.30 10.14

Table 5.6 Comparison of Analytical Ultimate Moment Carrying Capacity

for all the Specimens

Designation ofSpecimen

Analytical Ultimate Moment (kNm)Upward direction Downward direction

ML 7.16 7.45PC-JB 3.04 3.05PC-TR 4.91 6.23PC-CL 2.5 2.4PC-SS 3.73 4.97PC-DS 5.79 5.62PC-DW 4.06 3.73PC-DWCL 5.12 5.58

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Figure 5.8(a) Comparison of Measured Strength of all the Specimens in

the Positive Direction

Figure 5.8(b) Comparison of Measured Strength of all the Specimens in

the Negative Direction

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5.8.2 Hysteretic Behaviour

The behaviour of joint under cyclic loading had been represented as

the hysteretic curves with respect to load-displacement relationship.

5.8.2.1 Load-Displacement Relationship

The Load-displacement relations for the monolithic and seven

precast specimens are shown in Figure 5.9. At the early stage of loading, the

seven connections exhibited a stable load versus displacement hysteretic

response and then pinching could be observed in the hysteresis loops of all the

seven connections. Figure 5.9(a) shows the load- displacement hysteretic

response of the monolithic specimen ML. These figures exhibited fat

hysteresis loops with very less pinching. The areas of the hysteresis loops

gradually became larger as the displacement cycle increased, which indicates

good energy dissipating capacity.

Figure 5.9(b) to (h) show the load- displacement hysteretic

response and hysteretic response of the precast specimens. For specimens PC-

SS, the hysteresis curves were not symmetrical due to the presence of corbel

on one side and cleat angle with stiffener on the other side. Specimen PC-TR

also exhibited similar behavior, as the connection on the top was made by

using Tie rod and bottom connection was by welding two steel plates.

Because of this, there was a difference in load carrying capacity in both the

directions. Greater pinching was observed for all the precast specimens when

compared with the monolithic specimen, because of predefined gap opening

at the connections. Among the precast specimens, specimens PC-DS and PC-

DWCL pinching behavior was less than the other precast specimens. Figure

5.10 shows the load- displacement envelope response of all the specimens.

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Figure 5.9 (a) Hysteresis Load-Displacement Curve of Specimen ML

Figure 5.9 (b) Hysteresis Load- Displacement Curve of Specimen PC-JB

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Figure 5.9 (c) Hysteresis Load- Displacement Curve of Specimen PC-TR

Figure 5.9 (d) Hysteresis Load-Displacement Curve of Specimen PC-CL

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Figure 5.9 (e) Hysteresis Load- Displacement Curve of Specimen PC-SS

Figure 5.9 (f) Hysteresis Load-Displacement Curve of Specimen PC-DS

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Figure 5.9 (g) Hysteresis Load- Displacement Curve of Specimen PC-DW

Figure 5.9(h) Hysteresis Load- Displacement curve of Specimen PC-DWCL

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Figure 5.10 Hysteresis Load- Displacement Curves of all the Specimens

5.8.3 Energy Dissipation Capacity

Figure 5.11 (a) shows the comparative study of the cumulative

energy dissipation of the monolithic and that of TYPE I connection (PC-PB

and PC-TR). At the initial stages of loading upto drift 2.35% the energy

dissipative capacity of the precast specimens were higher than that of the

monolithic specimen because of the predefined gap opening present. The

precast connection with J-Bolt PC-JB shows 43.07% reduction in the

cumulative energy dissipation when compared to monolithic specimen

whereas specimen PC-TR exhibited 2.08% higher than the specimen PC-JB.

Similarly Figure 5.11(b) shows the comparative study of the energy

dissipation capacity of TYPE II connection with that of the monolithic

specimen. It is observed that the precast specimen with cleat angle PC-CL has

very less energy dissipation capacity whereas precast specimen with double

stiffener PC-DS has exhibited very good energy dissipation capacity almost in

comparison with the monolithic specimen ML. Figure 5.11(c) shows the

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comparative study of the energy dissipation capacity of TYPE III connection

with that of the monolithic specimen. At the drift ratio of 7.1% the precast

connection with dowel PC-DW shows 29.85 % reduction in the cumulative

energy dissipation when compared to monolithic specimen whereas specimen

PC-DWCL has exhibited very good energy dissipation capacity almost in

comparison with the monolithic specimen ML.

Figure 5.11 (d) provides a comparison of the cumulative energy

versus displacement levels of all the specimens. Generally, all the precast

specimens are dissipating greater energy when compared to monolithic

specimens ML in the initial displacement cycles, with the exception of

specimen PC-CL. The specimen PC-DS and PC-DWCL dissipates more

energy than the specimen ML upto 18 mm and 21mm displacement cycles

respectively. The specimen PC-JB PC-TR, PC-SS and PC-DW dissipates

more energy than specimen ML upto 10mm displacement cycle.

Figure 5.11 (a) Comparison of Cumulative Energy Dissipation of TYPE I

Connection with Specimen ML

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Figure 5.11(b)Comparison of Cumulative Energy Dissipation of TYPE II

Connection with Specimen ML

Figure 5.11 (c) Comparison of Cumulative Energy Dissipation of

TYPE III Connection with Specimen ML

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Figure 5.11 (d) Cumulative Energy Dissipation of all the Specimens

5.8.4 Displacement Ductility

Table 5.7 shows the comparison of displacement ductility factor. It

is observed that the displacement ductility factor of precast specimen PC-DS

and PC-DWCL was greater than the monolithic specimen ML whereas for the

other precast specimens, the displacement ductility was lesser than the

monolithic specimen ML. The specimen PC-DWCL and PC-DS showed

24.13% and 6.02% increase in ductility when compared to the monolithic

specimen respectively. Specimen PC-TR, PC-SS and PC-DW exhibited

almost the same displacement ductility.

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Table 5.7 Comparison of Displacement Ductility Factor

Specimen

Yielddisplacement y,

(mm)

Ultimatedisplacement

u (mm)

DisplacementDuctility factor( )

AverageDisplacement

Ductilityfactor( )Positive Negative Positive Negative Positive Negative

ML 6.7 7.1 30 30 4.478 4.225 4.351PC-JB 6.2 9.5 30 30 4.839 3.158 3.998PC-TR 5.8 11.5 25 25 4.310 2.174 3.242PC-CL 14..8 8.8 30 30 2.027 3.409 2.718PC-SS 7.3 13.9 30 30 4.110 2.158 3.134PC-DS 6.4 4.7 25 25 3.906 5.319 4.613PC-DW 7.8 12 30 30 3.846 2.500 3.173PC-DWCL 4.2 8.2 30 30 7.143 3.659 5.401

5.9 SUMMARY

The analytical investigation focused on developing a dry

mechanical exterior precast beam-column connection that emulates the

monolithic beam-column connection so that it can be adopted for low rise

buildings in seismic risk regions. Finite element models were developed using

the ANSYS software to study the response of exterior beam-column joint

under reverse cyclic loading. The element types, sectional and material

properties adopted for the finite element modeling in ANSYS were discussed

in detail. The analysis results were presented in the form of ultimate load

carrying capacity, ultimate moment carrying capacity, load-displacement

hysteretic curves, load-displacement envelope curves, energy dissipation and

ductility. The analytical study shows that the precast specimen with double

stiffener PC-DS and precast specimen with dowel and cleat PC-DWCL

performed well when compared to the entire precast specimen. The specimens

PC-DS and PC-DWCL compared well with the reference monolithic

specimen in terms of energy dissipation and ductility. In terms of load carrying

capacity the specimen PC-DS performed better than specimen PC-DWCL.