REVIEW ON THE METHODS OF REINFORCEMENT …Paulay and Bull [1971] were first introduced an idea in...

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 01, January 2019, pp. 970-987, Article ID: IJCIET_10_01_090

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=01

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

REVIEW ON THE METHODS OF

REINFORCEMENT TECHNIQUE IN

REINFORCED CONCRETE BEAM-COLUMN

JOINT

K.Marimuthu, and S. Kothandaraman

Research Scholar, Professor

Department of Civil Engineering, Pondicherry Engineering College, Puducherry, India

ABSTRACT

The awareness on seismic design for reinforced cement concrete (RCC) beam-

column (BC) joint was started with publication of ACI-ASCE 352 report in 1976. In

past earthquakes, several RCC buildings were suffered by severe damages/collapses.

These failures were occurred due to the usage of poor detailing in joint and insufficient

anchorage of beam longitudinal bars. The research on the BC joint was started in 1967

and extensive research has been carried out on studying the behaviour of RCC joints

under seismic condition through experimental and analytical studies. There are

different methods of reinforcing techniques have been developed over the years and

their main aim was to determine the effective reinforcing technique for beam-column

joint which include easy to adopt, effective performance, economical and cost-effective.

This paper gives an overview of the use of different reinforcing techniques used in

beam-column joint so far. The objective of this paper is to critically review the different

techniques developed so far with reference to the effect of each technique and outlined

the salient features of each technique.

Key words: Beam-column joint, Joint shear reinforcement, Joint shear strength,

Reinforced cement concrete.

Cite this Article: K.Marimuthu, and S. Kothandaraman, Review on the Methods of

Reinforcement Technique in Reinforced Concrete Beam-Column Joint International

Journal of Civil Engineering and Technology, 10(01), 2019, pp. 970-987

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=01

1. INTRODUCTION

International building codes recognized during the 1970’s that RCC BC joints require

transverse reinforcement to confine the column concrete to avoid the failure under seismic load

conditions. It is evident that seismic type loading can cause deterioration in strength of joint

K.Marimuthu and ,S. Kothandaraman


region and a substantial degradation in stiffness. Over the past 25 years in the United States,

New Zealand, and Japan extensive and systematic research works have been carried out to

understand the behaviour of RCC BC joints. However, they have not satisfactorily succeeded

in improving the behaviour. The specific reasons are decrease in strength, stiffness and energy

dissipation of the joint leading to collapse of the structure. In order to improve the joint

performance, several researches are carried out the study in the BC joints with different

detailing technique. The detailing techniques are spiral reinforcement technique, inclined bar

technique, headed bar technique, diagonal cross bar technique, hair clip reinforcing technique,

core reinforcement technique, diagonal collar stirrups, externally anchorage technique, and

headed studs’ technique. The aim of this paper is to critically review the above technique and

list the salient features of each technique used in the BC joints.

In past earthquakes, several RC buildings suffered by severe damages or collapses. These

failures were occurred due to the usage of poor detailing in joint and insufficient anchorage of

beam longitudinal bars. The effective performance of the BC joints depends on strength and

ductility and it can be achieved by providing adequate anchorage of beam bar and confinement

of core joint. Confinement of core joint was provided in the form of transverse reinforcement

and research on this subject was started from 1967 and Park and Paulay [1973] conducted a

study on exterior beam-column joint with varying amount and arrangement of transverse steel

and anchorage of beam bar. From the test result, it was concluded that beam-column joint

deterioration was mainly happened due to diagonal tension cracking and anchorage break

down. Also, they proved that the shear reinforcement provided in the joint region in accordance

with the recommendation of ACI 318-71 was inadequate. Pampanin et al [2002] and Calvi et

al [2002] examined the effect of combined use of smooth bar and inadequate joint detailing

such as lack of transverse reinforcement and insufficient anchorage length in the joint. From

the experimental study, they reported that slippage was happened due to insufficient anchorage

and smooth bar. Also, they observed that “concrete wedge” brittle failure mechanism occurred

in the exterior BC joint. Kuang and Wong [2004] studied the behaviour of joint with different

types of anchorage in beam reinforcement and arrangement of laps in column bar. They

concluded that hysteretic behaviour and shear resistance of the exterior BC joints mainly

depends upon detailing of reinforcement and confinement of the joint core. They also

emphasized that the design of RCC BC joint should not be ignored even for low to medium

earthquakes region areas.In order to improve the joint performance after detailed study, Park

and Paulay [1975] suggested a few techniques, bent-up bars, bent-up bars in stub beam and

mechanical anchorage attached to the end of the bar as shown in Fig. 1 to fulfil the

requirements of anchorage, shear and confinement with the joint core. They emphasised that

joint ties should be well arranged i.e. the crtical outer column bars and the bent-down portion

of the beam bars were held against the core of the joint. By considering the importance of

anchorage length, [Leon, 1989] studied the BC joint performance with various anchorage

lengths. They concluded that the minimum requirement of anchorage length of beam bar was

24 bar diameters to reach its ultimate strength. The anchorage length 28 bar diameter required

to improve the energy dissipation and ensured formation of plastic hinges in beam.

Subsequently, Kumar and Ravi [2014] investigated the effect of increase in anchorage length

by 25% and 50% in exterior BC joint. It was observed that load carrying capacity and energy

absorption capacity were considerably increased by increase in anchorage length. Also, the

codes ACI 352R-2002, IS 456-2000 and IS 13920-1983 strongly recommended the anchorage

for beam longitudinal bar for both seismic and non-seismic zone areas.

Review on The Methods of Reinforcement Technique in Reinforced Concrete Beam-Column

Joint


(a) Bent-up bar (b) Bent-up bar with stub beam (c) Mechanical anchorage

Figure 1 Anchorage of beam bar in column

1.2. Spiral reinforcement technique

The effective performance of RCC elements strongly depends on the lateral confinement

ensured in the joint (Richart, et al. 1929 and Iyengar, et al. 1970). The lateral confinement may

be provided in the form of lateral ties or spirals. Many investigators have proved that strength

and ductility is mainly depends on confinement. Use of spiral transverse in circular columns

could improve strength and ductility of RC columns (Park & Paulay 1975, Saatcioglu & Razvi

1992, and Sheikh & Toklucu 1993). ACI 352R-02 also recommended to use spiral transverse

in RCC BC joint for seismic zone areas. Recently the use of spiral reinforcement has been

extended in RC elements with rectangular cross section. The behaviour of RCC rectangular

beams with spiral reinforcement under both monotonic and pure torsion loading was

experimentally investigated (Karayannis et al 2005 and Chalioris & Karayannis 2013). They

concluded that use of rectangular spiral reinforcement ensured better torsion capacity, higher

shear strength and improved ductile performance. Subsequently, the study carried out to

investigate the behaviour of RC exterior beam-column joint with continuous spiral

reinforcement in the joint body. It was proved that the use of rectangular continuous spiral

reinforcement enhanced shear capacity, increased load carrying capacity and better ductility

performance of joint (Karayiannis 2014, Karayannis et al 2005 and Karayannis & Sirkelis

2005). Similar studies were carried out (Asha & Sundarajan 2011) in RCC BC joint with spiral

reinforcement with inclined bar technique. They concluded that presence of spiral and inclined

bars was successfully move the plastic hinge away from the column face.

2. INCLINED BAR TECHNIQUE

Paulay and Bull [1971] were first introduced an idea in short RCC beams to prevent the brittle

failure under cyclic loading. Following the above idea, Minami and Wakabayashi [1980] and

Tegos and Penelis [1988] implemented the same technique in short column to improve the

conventional method of reinforcement. They found the most effective method to improve the

behavior of RC short column and coupling beams.



Figure 2 Spiral arrangement in BC joint (Source: Karayannis and Sirkelis, 2005 & Asha and

Sundarajan, 2010)

Usage of inclined bar exhibited better hysteresis behavior and eliminated the cleavage shear

fracture at the joint. Subsequently, Tegos et al [1988] extended this technique to BC joints by

providing diagonal reinforcement [Fig. 3]. They concluded that the seismic performance of BC

joints has been improved substantially by the use of diagonal bars at the joints. Tsonos et al

[1992] introduced same technique in exterior BC joint and tested the joint sub assemblage

under seismic loading. They found that presence of cross inclined bar in the exterior BC joints

exhibited higher strength, improved hysteresis behaviour and less damage than the

conventional joint. Also, the presence of inclined bars introduced an additional new mechanism

of shear transfer. Similar studies were carried out by Chalioris et. al (2008) with different joint

shear reinforcement such as stirrups, X-bar, vertical bars and combination of them. The results

were presented in terms of strength, energy absorption, hysteresis curves and damage mode.

They concluded that specimen with combination of cross inclined bar and additional joint

stirrups showed excellent behaviour. Cracking was mainly localized in the BC joint interface

and plastic hinges were formed in the beam only. Providing an additional shear reinforcement

may cause the congestion and construction problem such as steel fabrication, placing and

compaction of concrete etc., In order to overcome the above problem, Kotsovo [2011]

introduced a steel plate for anchoring of beam’s longitudinal reinforcement with same

technique. They reported that combination of both steel plate and inclined bar arrangement in

the column exhibited improved behaviour and reduced the number of joint hoops (75%

reduced).

Figure 3 Inclined bar arrangement in BC joint and Short column (Source: Tsonos et al, 1992 &

Minami and Wakabayashi,1980)

3. HEADED BAR TECHNIQUE

This technique was originated from the French engineer Hennibique who obtained a patent for

his technique. In the United States, Nelson Stud Welding Company and the researches of

Lehigh University have extended this technique for the beam-column joints. After detailed

investigation, Park and Paulay [1975] suggested this technique to improve the performance of


Joint


the BC joint. The anchorage of straight bar and hook ended bar were used in conventional

detailing, but that led to steel congestion and serious construction problem such as fabrication,

placing and casting etc., To overcome these problems, Wallace et al. [1998 &1996] studied the

behaviour of RCC BC joints by using headed reinforcement (Refer Fig. 4). They commented

that headed reinforcement may not help to improve the performance of BC joints, but aided to

easy fabrication and may solve the construction difficulties. Also, behaviour of headed

reinforcement joint was better than the conventional standard 90-degree hooks. Similar studies

were carried out by Bashandy [1996] they concluded that the joint with headed reinforcement

exhibited superior performance compared to the hooked bar arrangement in terms of

maintaining stiffness and load carrying capacity. Formation of plastic hinges at the face of the

joint led to strength and stiffness deterioration. To eliminate the problem, Chutarat and

Aboutaha [2003] used straight headed bars in the BC joint and their arrangement was

successfully relocated the plastic hinge from the face of column. The effectiveness of headed

bar mainly depends upon the head size, clear spacing and bond behavior. Chun et.al (2009)

commented that the ratio of head area to bar area is 3 to 4 was sufficient to anchor the headed

bar in joint and use of smaller head size in joint resulted improve constructability, bond

behavior and anchorage capacity of the BC joint. Kang [2012] investigated the effect of clear

spacing between the headed bar and multilayer of headed bar in the beam. They concluded that

clear bar spacing between the headed bar approximately 2 bar diameter and two layers of

headed bar may be permitted. The two-layer head bar arrangement in the BC joint showed

improved energy dissipation and stiffness.

Figure 4 Headed bar arrangement (Source: Wallace et al, 1998)

An anchorage and confinement of core joint were major issues in BC joint. In order to

improve the core joint, Rajagopal and Prabavathy [2013] conducted a study on headed bar

reinforcement with different joint detailing. They found that combination of mechanical

anchorage and joint reinforcement such as “X” or hair clip arrangement exhibited better

moment carrying capacity and improved seismic performance. Hasaballa and Salakawy [2012]

investigated the joint by using GFRP bar with headed bar arrangement. They reported that, the

specimen with headed bar arrangement enhanced flexural carrying capacity (10%) and superior

performance compared to control specimen.

3.1. Diagonal cross bar (“X”) technique

The seismic design requires confinement of core joint and shear strength of joint. Provision of

shear reinforcement in the form of transverse reinforcement resulted serious congestion and

construction problem. Also, the BC joints without confinement led non-ductile behaviour and

brittle failure of joint. To eliminate these problems, Au et al (2005) and Pam et.al [2008]

introduced the same technique in the interior beam-column joint region. It was found that use

of diagonal bar in the joint region resulted, improvement in bond condition, better crack control



and aided the joints to maintain its stiffness. Also, they suggested that, the proposed technique

was suitable for joints of RC frame structure located in low to medium seismic regions.

Following the above study, Bindhu and Jaya [2010] carried out study on exterior BC joint with

cross bracing technique. The results showed that better performance in terms of increased load

carrying capacity, ductility, energy absorption capacity and lesser cracks in the joint. Also they

reported that using this technique cleavage failure in the joint can be avoided and presence of

additional cross bar in the joint introduced new shear transfer mechanism. Lu et al [2012] tested

ten full scale interior column joints with different joint detailing, such as diagonal cross bar,

joint transverse reinforcement, and straight bar (Refer Fig. 5). From the results, they concluded

that additional diagonal cross bar in the joint region helped to prevent cracks in the joint region,

formation of plastic hinges in the beam and increase strengthening capacity and ductility

capacity while increase lateral loading. Xian et al [2013] used the same technique in interior

and exterior BC joint with specially shaped column joint. The joints were tested with or without

“X” bar and the results of the experiments showed improved ductility behaviour (15% higher),

delayed stiffness degeneration and less damage. Rajagopal and Pravathy (2013) tested a series

of six specimens of the RCC BC joint with different anchorage detailing of beam bar and

different details of joint reinforcement.

Figure 5 “X” bar arrangement in BC joint (Source: Lu et al, 2012)

They revealed that specimen with mechanical anchorage and “X” bar offered a better

moment carrying capacity and improved seismic performance without compromising the

ductility and stiffness. Also, they suggested that this arrangement in exterior beam column joint

helped to reduce congestion of reinforcement, easier placement of concrete and aided in faster

construction at site.

3.2. Hair clip reinforcement

The performance of joint was mainly depending on detailing of joint and the detailing should

have unproblematic fabrication and easy placing of the reinforcement in the core joint. In order

to reduce the practical construction problem, Murty et al [2003] conducted a study on exterior

BC joints with four details of longitudinal beam bar anchorage and three details of transverse

joint reinforcement. They found that the combination of ACI standard hook and the suggested

hairclip-type was found to be more effective and easier to construct. Also, they suggested that

this combination could be used where the ductility demand was moderate. Especially this

technique could be used in low rise buildings which are located in low seismic zone area.

Following the above study Rajagopal and Prabavathy [2013] investigated the behaviour of

exterior BC joint with three different anchorage detail such as ACI-352 (Mechanical

anchorage), ACI-318 (90-degree standard bent anchorages) and IS-456 (Full anchorage along

with confinement as per IS-13920). They concluded that use of mechanical anchorage with an

additional “hair clip” bar imparted significant improvement in strength, ductility and stiffness.


Joint


Also, they reported that usage of this technique in exterior joint could reduce the congestion,

easier placement and speedy construction at site.

3.3. Core reinforcement

Strength and ductility are major criteria for effective functioning of reinforced concrete BC

joint. To improve the ductility and strength, Ha and Cho [2008] placed an anchor type

intermediate bar and doubly confined closed stirrups in the core joint. They found that their

technique improved load carrying capacity, energy dissipation capacity, ductility, less damage

and successfully shifting the plastic hinges from the joint region. Bindhu and Sreekumar [2011]

used same technique and joint was tested with or without additional beam bars. The results

showed that improved behaviour. Following the above study, Kaliluthin and Kothandaraman

[2014] proposed a new reinforcement technique which is called as “core reinforcement” and

they conducted the study with three different categories of joint such as Reference joint (joint

detailed as per IS 456-2000), ductile joint (joint detailed as per 13920-1993) and core joint

(same as Reference joint detailing, but cage reinforcement was provided in the core of the

joint). They reported that presence of core reinforcement as shown in Fig. 6 enhanced load

carrying capacity, stiffness and ductility factor.

Figure 6 Core reinforcement arrangement in BC joint (Source: Kaliluthin and Kothandaraman, 2014

& Ha and Cho, 2008)

3.4. Diagonal Collar stirrups

Bindhu and Sreekumar [2011] investigated the BC joints with four types of joint detailing

techniques. The first joint was ductile joints as per IS:13920. Second joint was ductile joint

with additional beam reinforcement and diagonal collar stirrups. Third joint was ductile joint

with additional beam reinforcement and fourth joint was same as the first joint but with reduced

number of ties. They concluded that second and third type of joints performed well in terms of

load carrying capacity, ductility and energy absorption capacity. However, they did not

comment on the problems with congestion of reinforcement at the joints.

3.5. Externally anchorage technique

The beam longitudinal bars both top and bottom were anchored externally by providing a small

projection beyond the column face. Park and Paulay [1973] conducted a study on RC exterior

BC joint with providing stub beam. They found that the specimen with stub beam performed

better than the other specimen. After detailed study, Park and Paulay [1975] also suggested this

technique to fulfil the requirements of anchorage, shear and confinement with the joint core.

Similar studies were carried out by Chidambaram and Thirugnanam [2012] and their main

investigation was behaviour of exterior BC joints with stub (Refer Fig.7). From the results,



they reported that the specimen with stub beam exhibits increased first crack load (45%), better

hysteretic behaviour, enhanced load carrying capacity, energy absorption capacity (4 times),

and ductility. Also, they suggested that the joint with stub exhibited superior performance and

it can be recommended for structure that located in seismic prone areas.

3.6. Headed Studs technique

Seismic joint requires closed hoops, cross ties and anchorage of beam bars but combination of

all together in the joint causes serious construction problem and this leads to weak joint. To

replace the conventional shear reinforcement, Cui [2012] introduced the studs on solid SFRCC

slab and examined the behaviour of solid SFRCC slab. It was reported that headed stud

embedded in solid SFRCC slab was succeeded in beam hinge mechanism. Also, it exhibited

better load resisting capacity and improved seismic behaviour. Mojarradbahreh [2013]

investigated behaviour of the BC joint with double-headed studs (Refer.8). They concluded

that specimen with deformed double-headed studs showed superior behaviour in terms of load

carrying capacity, energy absorption capacity and better controlling the crack compared to the

conventional joints. Also, they have noted that the behaviour of headed studs’ specimen was

very closer to conventional joint behaviour.

Figure 7 Externally anchorage arrangement in BC joint

(Source: Chidambaram and Thirugnanam, 2012 & Park and Paulay,1973)

Figure 8 Heded studs’ arrangement in BC joint (Source: Mojarradbahreh and Elbadry 2013)

Table 1 Summary of Findings on BC joint with Various Reinforcement Technique.

S.No Researcher’s Salient features

Anchorage of beam longitudinal bar

1 Park and Paulay [1973]

• Quick deterioration due to diagonal tension

cracking and anchorage breakdown

• Transverse reinforcement provided in the

joint as per ACI 318-71 was inadequate.


Joint


• Spacing of transverse reinforcement in the

joint should not exceed 6 inches

• Narrow column needs beam stubs for

anchoring the beam main bar.

2 Leon [1989 ]

• Anchorage length from 24 to 28 bar

diameter needed for effective functioning

of joint.

• Anchorage length less than 20 bar diameter

caused very rapid deterioration.

3 Pampanin [2002]

• Concrete wedge brittle damage mechanism

was found due to use of smooth bar, end-

hook anchorage and absence of transverse

reinforcement in the joint.

• Slippage of beam bar mainly due to use

smooth bar and inadequate anchorage.

4 Kuang and Wong [2004]

• Shear capacity and hysteretic behavior of

the exterior BC joint depends on the

detailing of reinforcement and anchorage

length.

• Design of joint must be considered in low

to medium earthquake prone areas.

• Laps in columns bar at the lower zone do

not affect the shear strength of joint.

5 Anoop kumar [2014]

• Ultimate load carrying capacity (20%) and

energy absorption capacity (20% to 46%)

were significantly increased by increase in

anchorage length.

• First crack load was improved (15 to 17%).

Spiral reinforcement technique

6 Karayannis, et al. [2005]

• Enhanced shear strength (15% to 17%) and

improved performance.

• Observed ductile failure.

7 Chalioris and Karayannis

[2013]

• Increase in number of hoops resulted

increased torsional capacity and ductility.

• Effective performance was found when

spiral arrangement was in locked position.

• Increased torsional strength (14% to 18%).

8 Karayannis [2014]

• Damages were localized in beam’s critical

region and hinges were formed at beam.

• Enhanced energy absorption capacity

(34%) and better performance in terms of

maximum load.



9 Karayannis & Sirkelis [2005]

• Plastic hinges were in beam-column

interface.

• Superior performance was observed in

terms of energy absorption and ductility.

10 Asha and Sundararajan

• Spiral and inclined bars arrangement in the

joint were successfully moved the plastic

hinges away from the column face.

• Improved load ratio (2% to 48%), initial

stiffness (31%) and energy absorption

capacity (9% to 45%).

Inclined bar technique

11 Tegos and Penelis [1988]

• Most effective method to improve the

behavior of RC short column and coupling

beams.

• Presence of inclined reinforcement exhibit

better hysteresis behavior and eliminate the

cleavage shear fracture at the joint.

12 Tsonos, et al. [1992]

• Enhanced energy absorption capacity and

less damages were found at ultimate

capacity.

• Most effective method for exterior BC

joint to improve the seismic behavior and

introduced an additional mechanism of

shear transfer.

• Overall performance of the joint was

improved than the conventional joint.

13 Chalioris, et al [2008]

• Improve the shear capacity and restrain the

bent anchorage deformation

• Combination of cross inclined bar and

additional joint stirrups showed excellent

behaviour.

• Cracks were localized in the BC joint

interface and plastic hinges were formed in

the beam.

14 Kotsovo [2011]

• Improved seismic behaviour.

• Presence of inclined bar and steel plate

arrangement for anchorage exhibited

reduced number of joint hoops (75%

reduced).

Headed bar technique

15 Wallace, et a. [1998] • Headed reinforcement may not help to

improve the performance of BC joints but


Joint


aided to easy fabrication and may solve the

construction difficulties.

• Behaviour of joint was superior than the

conventional standard 90-degree hooks.

• Minimum anchorage length in the joint

should be 12 bar diameter and tension head

area on the bar must be presented 4 times

the bar area.

16 Chutarat [2003]

• Straight headed bars in the BC joint were

effectively relocated the plastic hinge from

the face of column.

• Adequate shear strength must be provided

in the joint to relocate the plastic hinges.

• The effectiveness of headed bar mostly

depends upon the head size, clear spacing

and bond behavior.

• Enhanced beam shear demand.

17 Chun [2007]

• Ratio of head area to bar area is 3 to 4 was

sufficient to anchor the headed bar in joint.

• Improved constructability, bond behavior

and anchorage capacity of the BC joint

were achieved by using smaller head size

in joint.

• Hysteretic behavior was similar or higher

than hooked anchorage.

18 Bashandy[1996]

• Superior behavior was observed than

hooked bar arrangement.

• Minimum stiffness degradation and less

damage.

• Strain in the head bar and longitudinal bar

was similar to hooked bar specimen.

• Anchorage capacity was increased when

increasing side cover.

• Good level of confinement in the joint

exhibited enhanced bearing capacity of

head and ultimate load.

19 Hsaballa and Salakawy [2012]

• GFRP bar with headed bar arrangement

exhibited improved load carrying capacity

(10% higher).

• Combination of GFRP bar with headed bar

was exhibited high stable and less spalling

and at 5% drift.

20 Rajagopal and Prabavathy

[2013] • Better crack control and improved seismic

performance.



• Reduced congestion, easy fabrication and

placing of concrete.

Hair clip reinforcement technique

21 Murty et al [2000]

• More effective and easy to construct.

• Used in low rise buildings which are

located in low seismic zone area.

22 Rajagopal and Prabavathy

[2013]

• Enhanced moment carrying capacity,

ductility and stiffness.



“X” bar technique

23 Bindhu and Jaya [2010]

• Enhanced load carrying capacity, ductility,

energy absorption capacity and fewer

cracks in the joint.

• Cleavage failure in the joint could be

avoided.

• Established a new shear transfer

mechanism.

24 Lu. et al. [2012]

• Strength and ductility of the specimen

were improved using diagonal bar.

• Crack at the end of the joint was prevented.

• Plastic hinges formed in the beam in

advance than the column.

25 Au. et al. [2005]

• Improved strength and bond condition.

• Delayed stiffness degradation and

controlled crack formation at BC joint

interface.

• Suitable for low to medium seismic area.

26 Pam. et al. [2008] • Improved ductility and suitable for low to

medium seismic area.

27 Rajagopal and Prbavathy [2013]

• Enhanced moment carrying capacity,

ductility and stiffness.



Core reinforcement

28 Kaliluthin and Kothandaraman

[2014]

• First crack load of core joint specimen was

increased about 15% than reference and

ductile joint.


Joint


• Ultimate load carrying capacity of core

joint was 25% more than the reference

joint and 6% more than the ductile joint.

• Stiffness factor of core joint was 38% more

than the reference joint and 47% more than

the ductile joint.

• Ductility factor of core joint was 50% more

than the reference joint and 25% more than

the ductile joint.

29 Ha and Cho [2008]

• Plastic hinges were successfully shifted

away from the joint.

• Improved load carrying, ductility and

energy dissipation capacity

• Lesser amount of damage.

30 Bindhu and Sreekumar [2011] • Improved load carrying, ductility and

energy dissipation capacity.

Externally anchorage technique

31 Park and Paulay [1973] • Beam stubs are necessary for narrow

column for anchoring the beam main bar.

32 Cidambaram and Thirugnanam

[2012]

• First crack load was improved (45%).

• Energy absorption and ductility were

improved 4 times and 2 times respectively.

Diagonal collar stirrups

33 Bindhu and Sreekumar [2011]

• Increased load carrying capacity (98%),

ductility (54%) and energy dissipation

capacity (22%) was observed compared to

specimen detailed as per IS13920.

Headed Studs technique

34 Mojarradbahreh [2013]

• Deformed double-headed studs revealed

better behavior than the conventional

methods.

• Diagonal arrangements of headed studs

improved load carrying capacity and

control of shear cracks.

35 Cui, et al. [2012]

• Solid SFRCC slab exhibited larger

resisting load and shear resistance of stud

depends on longitudinal spacing

• Load transfer of SFRCC slab with one

headed stud arrangement was 15% higher.

• By using sufficient studs and appropriate

rebar exhibited beam hinge mechanism



4. SUMMARY

This review has explored various methods of detailing technique developed till now. The

strength and ductility of the joint were achieved by providing sufficient anchorage length to

the beam bar and good confinement to the joint. These are the major issues in BC joints so far.

To improve the behavior of BC joint, various techniques have been studied over the years

through experimentally and analytically. The outline of the reviewed BC joint technique are

summarized below:

• Park and Paulay [1975] suggested a few techniques and these techniques were bent up

bar, bent up bars in stub beam and mechanical anchorage attached to the end of beam

bar.

• Lack of detailing such as inadequate anchorage bar and absence of transverse

reinforcement caused sudden degradation in strength and stiffness (Pampanin, 2002,

Calvi, 2002 and Kuang and Wong; 2004). To find out solution for anchorage, Leon

[1989] and Kumar [2014] studied the BC joint with varying anchorage length. They

found that increase in anchorage length of beam bar resulted enhanced strength and

energy dissipation capacity.

• Then confinement of joint was achieved by providing sufficient amount of transverse

reinforcement in the joint. Hanson and Conner [1967] emphasized the importance of

transverse reinforcement that was provided in the BC joint.

• The effective performance of the joint strongly depends on the lateral confinement

ensured in the joint (Richart, et al. 1929 and Iyengar, et al. 1970). To encounter

confinement issue, several researchers reported the effect of spiral reinforcement in the

joint (Karayannis, 2014, Karayannis, et al. 2005, and Karayannis & Sirkelis, 2005).

They concluded that use of spiral reinforcement in the joint exhibited enhanced shear

capacity, load carrying capacity and ductility of joint.

• For improving conventional method, an inclined bar technique was introduced in the

joint (Tegos and Penelis, 1988, Tsonos, et al. 1992 and Chalioris; et al. 2008) This

technique offered improved behavior, enhanced energy absorption capacity, less

damage at ultimate stage and formed additional mechanism of shear transfer.

• Kotsovo [2011] found that use of inclined bar in the joint resulted reduced amount

hoops (75%) in the joint and reduce the congestion problem.

• To replace the conventional ninety-degree hooks and bundle of bar in the joint, the

researchers were found headed bar technique and their result showed that improved

performance, reduced congestion, easy fabrication and easy placing of concrete in the

joint (Wallace, et al. 1998 &1996, Bashandy 1996, Rajagopal and Prabavathy. 2013

and Hasaballa and Salakawy, 2012).

• As joint without confinement led to non-ductile behavior, researchers (Au, et al. 2005

and Pam et.al, 2008 Bindhu and Jaya, 2010, Lu, et al. 2012 Xian, et. al, 2013 and

Rajagopal and Pravathy, 2013) tried to improve the confinement of core by using

diagonal cross bar in the joint. They found enhanced strength and increased ductility,

better crack control, improved bond condition, and reduced congestion. Also, they

suggested that this technique may be suitable for low to medium seismic regions.

• Ha and Cho, [2008], Bindhu and Sreekumar, [2011] and Kaliluthin and

Kothandaraman, [2014] made an effort to improve the strength and ductility by using

core reinforcement. They found that enhanced behavior in terms of strength, ductility.


Joint


Also, Ha and Cho, 2008 reported that the plastic hinges were successfully moved to

beam.

• As effective performance of the joint was mainly depending on the anchorage of beam

bar, Park and Paulay [1975], and Chidambaram and Thirugnanam [2012] introduced

the beam stub in the BC joint and the beam bar has external anchored. This technique

exhibited increased first crack load (45%), enhanced load carrying capacity, energy

absorption capacity (4 times), and ductility.

• Diagonal collar was another method to improve confinement in the joint and Bindhu

and Sreekumar [2011] reported that use of diagonal collar stirrups exhibited better

performance in terms of strength, ductility and energy absorption capacity.

• Mojarradbahreh [2013] reported that use of headed studs in place of conventional shear

reinforcement in the joint was superior performance and behaviour of headed stud joint

was very closer to convention behaviour.

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