Experimental Investigation of Reinforcement Couplers as Replacement of Bent Bar

Experimental Investigation of Reinforcement
Couplers As Replacement of Bent Bar
ROHITKUMAR A. PANDEY

CONTENT
• Introduction
• Literature review
• Objective
• Scope of work
• Observation Table
• Crack Pattern Study
• Conclusion
• Future scope
• Paper publication
• References

INTRODUCTION
• A headed bar is a deformed steel bar with a head attached to one, or
both ends of the bar.
• Headed bars can be used as a replacement for straight or hooked bars
in concrete members and connections.
• Headed bar reinforcement is effective in reducing rebar anchorage
length, congestion, and construction time.
• Reinforced concrete structures beam-column joints are the most
critical regions in seismic prone areas.
• The investigated database comprises most available experimental
tests on this subject around the world, including those conducted in
the U.S., Korea, Japan, and Taiwan.

Advantages & Disadvantages
• Fastest system to install
• Self aligning
• No cross threading
• Compact size
• Range of anchorage types
• Easy to Inspect
• Full tensile strength
• Low slip
• Low installed cost
• Proven track record
• Needs Position type coupler for bent bars
• Bar end threading

Why we are using mechanical anchorage (Reinforcement coupler)?

Side Spall Failure
Shear Cone Failure

Paper 1 :“Use of mechanically anchored bars in exterior beam-column joints subjected to
subjected to seismic loads” John w. Wallace, Scott w. McConnell , Erico inc., solon, ohio 1997
•Mechanically anchored bars with
diminutive heads in exterior beam-
column joints.
•Consisted of testing two, full-scale,
exterior beam-column joint sub
assemblages.
•The utilization of mechanically
anchored bar as replacement standard
hooks.
•A minimum anchorage length of 12db
is recommended for reinforcement
terminated within a beam-column joint
provide the head bearing area in tension
is at least four times the bar area.
12.75 ft (3.89 m)
10 ft
(3.05m)
TEST SETUP
Exterior Inter-Story Connections
LITERATURE REVIEW

Paper 2 :“Use of headed reinforcement in beam-column joints subjected to earthquake loads”
John w. Wallace, Scott w. McConnell, Piush gupta, Paul a. cote, Aci structural journal
September 1998
•John w. wallance to evaluate the applicability of
mechanically anchored bars with diminutive heads in
exterior beam-column joints.
•The research program consisted of testing two, full-
scale, exterior beam-column joint sub assemblages.
•One of the specimens was subjected to cyclic laod
wheras the other specimen was subjected to essentially
monotonic load .
HYDRAULIC ACTUATOR
LOAD CELL
CLEVIS
52"
HEAVY LINK
SPECIMEN
LVDT FORDISPL.
CONTROL
RIGID REFERENCE
FRAME
36"
TIE DOWN REACTION WALL
STRONG FLOOR
TEST SETUP
Exterior Roof Connections

Beam End Rotation
Exterior Inter-story Connections
BCEJ1 - Drift Level 6%
Potentiometer
Bottom Bar Push-Out @ 6%
Slight Pushout Occurs
Redistribution From
Steel to Concrete
 Minor Reduction in
Beam Moment Capacity
 Note - Compression ld
Satisfied by Checking
Tension ld

Paper 3 : “Seismic Design of Reinforced Concrete Beam-Column Joints with Headed Bars”
Thomas H.-K. Kang, Myoungsu Shin, Nilanjan Mitra, and John F. Bonacci,
Aci structural journal November/December 2009
• The test database was assessed to evaluate the
incipient ACI 318-08, Section 12.6, requisites for
applications in beam-column joints and to
supplement the current ACI 352R-02 report.
• Section 12.6 provisions of ACI 318-08 detail the
development of headed and mechanically anchored
deformed bars for the first time in the Code series.
• Joint ACI-ASCE Committee 352 published design
recommendations for headed reinforcement used in
reinforced concrete beam-column joints (ACI
352R-02). However, both ACI 318-08 and 352R-
02 are predicated on quite constrained
experimental research.
Defined notation for various dimensions

• The development length ldt for headed bars in
beam-column joints that ACI 352R-02,
• while the ldt designated by ACI 318-08 is relatively
much more conservative for headed bars in beam-
column joints.
• The equation of ACI 352R-02 can be included in
Section 21.7.5 of ACI 318-08.
• The lateral confinement is supplied by closed
hoops within the joint and by at least one beam
member covering at least 3/4 of the column width.
• Thus, either minimum head size should be
designated to ascertain the desired nonlinear joint
comportment, or a term associated with head
bearing may be considered in the development
length equation for further detailed investigation.Schematic diagrams of investigated beam-column
joint subassemblies with headed bars.

Paper 4 : “Prediction of performance of exterior beam-column connections with headed bars
subject to load reversal”
Thomas H.-K. Kang, Nilanjan Mitra
Engineering Structures April 2012
• ACI 318-08 provisions and 352R-02
recommendations have been developed predicated
on quite constrained experimental data, an
extensive database was assembled by Kang.
• which contains most of the available test data of
reinforced concrete exterior beam-column
connections with headed bars subject to load
reversal.
• The recent data focusing on the investigation of
design parameters of clear bar spacing and head
size, and re-evaluated utilizing a variety of
statistical and empirical techniques.
• binomial logistic regression methodology has been
applied.
• A reliable and robust goodness-of-fit test, the
loglikelihood ratio test, was performed to evaluate
the developed logistic regression model.
Reinforced concrete beam-column connection with headed bars

• Binomial logistic regression methodology has been developed to quantify the effect
of each design parameter in determining the performance of the beam-column
connection with headed bars subject to load reversal.
• An incrementation in development length, head thickness and head size and a
decrementation in joint shear demand result in a qualitatively better performance of
the connection.
• An incrementation in bar yield strength, joint transverse reinforcement, and column
axial force correlates to incremented probability of unsatisfactory performance.
• two of the most influential design parameters on the connection performance and
the feasibility of the applications of very high strength headed bars in beam-column
connections is highly disputable.

Paper 5 : “Investigation on the seismic behavior of exterior beam–column joint using T-type
mechanical anchorage with hair-clip bar”
S. Rajagopal , S. Prabavathy
Journal of King Saud University “Engineering Sciences” September 2013
• An endeavor has been made to study and evaluate
the performance of exterior beam–column joint
utilizing opportune reinforcement anchorage and
joint core detail.
• The anchorages are detailed as per ACI-352
(Mechanical anchorage), ACI-318 (90º Standard
bent anchorages) and IS-456 (Full anchorage)
along with confinement as per IS-13920.
• Consequential amendments were observed in
seismic performance, ductility and strength while
utilizing proposed hair-clip bar plus X-cross bar in
amalgamation with mechanical anchorage detail
for higher seismic prone areas, apart from
resolution to reducing congestion of reinforcement
in joint core.
Schematic diagram of test setup

• Specimen A1 which has proposed adscititious hair clip and X-cross bar with the cumulation of T-type
mechanical anchorage joint detail offers a better moment carrying capacity thereby amending the seismic
performance without compromising the ductility and stiffness.
• The utilization of conventional 90º bent hook anchorage arrangements in the beam–column connection.
• earthquake leads to an incrementation in size of column to accommodate the required amount of beam
reinforcement in the joint core.

 CONCLUSION FROM LITERATURE REIVIEW
• Mechanical anchorage joint detail offers a better moment carrying capacity
thereby improving the seismic performance without compromising the ductility
and stiffness.
• Arrangement of reinforcement detail in the exterior beam-column joint core
reduces congestion of reinforcement, easier placement of concrete and aids in
faster construction at site.
• Combination of anchorage and joint detailing may be used in locations
demanding low and moderate ductility situation.

OBJECTIVE
 Establishing different type of RC beam specimens using Reinforcement couplers as replacement of Bent bar.
 A comprehensive literature review on Reinforcement coupler and structure interaction problems as it relates
to the foundation was undertaken to review the concept of the bridge design, building construction.
 The effect on casted RC beam specimens under the monolithic loading condition were investigated.
 Review on the behavior of reinforcement couplers over conventional method is studied with different
specimens.
 Preparation of chart of load & displacement test result for each casted specimen.
 The effect of loading condition & failure patterns of casted beam specimens has been investigated & studied.

Outline of project
Study of
literature
review
Define testing
setup
Computing
steel section
Casting of
specimens as
per mix design
Preparetion of
testing setup as
per reqirement
To test
specimens
Study about
Failur pattern

SCOPE OF WORK
• After review on comprehensive literature reinforcement coupler is replace with bent bar of specimens.
• For making testing specimens setup ACI 352R-02, ACI 318-14, IS 456-2000, & IS 13920-2016 guidelines
were used and for casting beam specimens M25 grade mix design is used.
• Preparing testing setup for test of casted specimens is generate with steel beam ISMB 300.
• Each casted specimens is situated in testing setup and load applied on specimens with help of hydraulic jack.
• After application load on each casted specimens have to be study for deflection.
• For each testing specimens have to be study of crack patter after the application of increasing monolithic
loading.

 Replacing of bent bar by Reinforcement coupler (Mechanical anchorage).
8 mm Reinforcement Coupler

 To making testing specimens according to ACI 352R-02, ACI 318-14, IS 456-2000.
Type B
ACI:352R-02
MECHANICAL
ANCHORAGE
(Reinforcement
coupler)
Type A
IS 456:2000 &
ACI: 318-11
STANDARD 90°
BENT-
ANCHORAGE
Type C
Reinforcement
coupler with
stirrups

Casting of Specimens
Form work Steel Cage Placing of
Concrete
Removal of
Form work
Curing of
Specimens
Completed
Specimens

 Construction & installation of Steel frame having with 25 ton capacity.
Schematic diagram of test
setup
Filed arrangement of test setup
ISMB300
ISMB300

 Each casted specimens is situated in testing setup and load applied on specimens with help of
hydraulic jack.
Hydraulic Jack of 25-ton (250 KN) capacity with pumping units

Observation Table
Specimen Type
Yielding
displacement
in mm (∆y)
Ultimate
load in KN
(Pu)
displacement
for ultimate
load(∆u)
displacement
ductility factor
µ=∆u/∆y
stiffness
KN/mm
k=Pu/∆y
Type A
(conventional)
A1 2.15 83.81 68.00 31.63 38.98
A2 2.40 87.07 72.00 30.00 36.28
A3 2.20 89.40 74.00 33.64 40.64
Type B
(Reinforcement
coupler)
B1 2.30 88.47 50.00 21.74 38.47
B2 2.85 93.13 53.00 18.60 32.68
B3 3.00 97.78 55.00 18.33 32.59
Type C
(Reinforcement
coupler with
stirrups)
C1 3.15 97.78 45.00 14.29 31.04
C2 3.20 100.11 48.00 15.00 31.28
C3 3.25 102.44 50.00 15.38 31.52

Avg. Value of Observation Table
Specimen Type
Yielding
displacement in
mm (∆y)
Ultimate load in
KN (Pu)
displacement
for ultimate
load(∆u)
displacement
ductility
factor
µ=∆u/∆y
stiffness
KN/mm
k=Pu/∆y
Type A
(conventional)
2.25 86.76 71.33 31.75 38.63
Type B
(Reinforcement
Coupler)
2.72 93.13 52.67 52.67 34.58
Type C
(Reinforcement coupler
with stirrups)
3.20 100.11 47.67 47.67 31.28

Load Vs. Displacement Graphs
68.00
72.00
74.00
67.00
68.00
69.00
70.00
71.00
72.00
73.00
74.00
75.00
83.00 84.00 85.00 86.00 87.00 88.00 89.00 90.00
DISPLACEMENT(mm)
LOAD (KN)
LOAD Vs. DISPLACEMENT (TYPE A)

50.00
53.00
55.00
49.00
50.00
51.00
52.00
53.00
54.00
55.00
56.00
88.00 90.00 92.00 94.00 96.00 98.00 100.00
DISPLACEMENT(mm)
LOAD (KN)
LOAD Vs. DISPLACEMENT (TYPE B)

45.00
48.00
50.00
44.00
45.00
46.00
47.00
48.00
49.00
50.00
51.00
97.00 98.00 99.00 100.00 101.00 102.00 103.00
DISPLACEMENT(mm)
LOAD (KN)
LOAD Vs. DISPLACEMENT (TYPE C)

Avg. Graph of load Vs. displacement Type (A,B,C)
71.33
52.67
47.67
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
86.00 88.00 90.00 92.00 94.00 96.00 98.00 100.00 102.00
DISPLACEMENT(mm)
LOAD (KN)
LOAD Vs. DISPLACEMENT

83.81
87.07
89.40 88.47
93.13
97.78 97.78
100.11
102.44
0.00
20.00
40.00
60.00
80.00
100.00
120.00
A1 A2 A3 B1 B2 B3 C1 C2 C3
Type A (conventional) Type B (Reinforcement Coupler) Type C (Reinforcement coupler with stirrups)
LOAD(KN)
DIFFERENT TYPE OF SPECIMENS
Ultimate load in KN (Pu)

68.00
72.00
74.00
50.00
53.00
55.00
45.00
48.00
50.00
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
A1 A2 A3 B1 B2 B3 C1 C2 C3
DISPLACEMENT(mm)
DIFFERENT TYPES OF SPECIMENS
Displacement for ultimate load(∆u)

31.63
30.00
33.64
21.74
18.60 18.33
14.29 15.00 15.38
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
A1 A2 A3 B1 B2 B3 C1 C2 C3
DUCTILITY(mm)
DIFFERENT TYPE OF SPECIMENS
DUCTILITY FACTOR µ=∆u/∆y

38.98
36.28
40.64
38.47
32.68 32.59
31.04 31.28 31.52
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
A1 A2 A3 B1 B2 B3 C1 C2 C3
STIFFNESS(KN/mm)
DIFFERENT TYPES OF SPECIMENS
STIFFNESS (KN/mm) k=Pu/∆y

Average Graph of specimens
Type A
(conventional)
Type B
(Reinforcement
Coupler)
Type C
(Reinforcement
coupler with
stirrups)
displacement for ultimate
load(∆u)
71.33 52.67 47.67
71.33
52.67
47.67
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
Displacement(mm)
Different Type of Specimens
Displacement for ultimate load(∆u)
displacement for ultimate load(∆u)
Type A
(conventional)
Type B
(Reinforcement
Coupler)
Type C
(Reinforcement
coupler with
stirrups)
Ultimate load in KN (Pu) 86.76 93.13 100.11
86.76
93.13
100.11
80.00
85.00
90.00
95.00
100.00
105.00
Load(KN)

Type A
(conventional)
Type B
(Reinforcement
Coupler)
Type C
(Reinforcement
coupler with
stirrups)
displacement ductility factor
µ=∆u/∆y
31.76 19.56 14.89
31.76
19.56
14.89
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Ductility(mm)
Ductility factor µ=∆u/∆y
displacement ductility factor µ=∆u/∆y
Type A
(conventional)
Type B
(Reinforcement
Coupler)
Type C
(Reinforcement
coupler with
stirrups)
stiffnessK N/mm k=Pu/∆y 38.63 34.58 31.28
38.63
34.58
31.28
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
Stiffness(KN/mm)
Stiffness (KN/mm) k=Pu/∆y
stiffnessK N/mm k=Pu/∆y

Compare To Type A Graph of Ductility & Stiffness for Type (B, C)
Type B (Reinforcement Coupler)
Type C (Reinforcement coupler with
stirrups)
81.93 53.11
81.93
53.11
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
Ductility(mm)
Ductility Factor
Type B (Reinforcement Coupler)
Type C (Reinforcement coupler with
stirrups)
12.96 19.03
12.96
19.03
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Stiffness(KN/mm)

2.15 2.40 2.20 2.30 2.85 3.00 3.15 3.20 3.25
83.81
87.07 89.40 88.47
93.13
97.78 97.78 100.11 102.44
68.00
72.00 74.00
50.00 53.00 55.00
45.00 48.00 50.00
31.63 30.00
33.64
21.74 18.60 18.33
14.29 15.00 15.38
38.98 36.28
40.64 38.47
32.68 32.59 31.04 31.28 31.52
0.00
20.00
40.00
60.00
80.00
100.00
120.00
A1 A2 A3 B1 B2 B3 C1 C2 C3
Type A (conventional) Type B (Reinforcement
Coupler)
Type C (Reinforcement
coupler with stirrups)
Yielding displacement in mm (∆y) Ultimate load in KN (Pu)
displacement for ultimate load(∆u) displacement ductility factor µ=∆u/∆y
stiffness KN/mm k=Pu/∆y

 Crack Pattern study
Type A Conventional
87.07
KN
83.81
KN
89.40
KN

Type B
Reinforcement Coupler
88.47
KN
97.78
KN
93.13
KN

Type C
Reinforcement Coupler With Stirrups
97.78
KN
100.11
KN
102.44
KN

 Conclusion
 It has been observed from the experimental test results that the reinforcement coupler with stirrups as per IS-
456(specimens C1and C2,C3) offer better performance than the specimens reinforced with conventional 900
standard bent hooks anchorage as per ACI-318(specimens B1and B2,B3) and as per ACI-352 (specimens A1
and A2,A3).
 Type C gives better performance Compare to type A in ductility is 53.11%, & Stiffness 19.03%.
 Type C gives better performance Compare to type B in ductility is 23.87%, & Stiffness 9.54%.
 The specimen C1 and C2, C3 with mechanical anchorage with stirrups shows lesser crack pattern than other
specimens using conventional anchorage and joint details.

 The use of a single mechanical anchorage device in place of the 90-degree hook terminating in the
joint resulted in an equivalent or better performance under large inelastic displacement.
 Mechanical anchorage joint detail offers a better moment carrying capacity thereby improving the
seismic performance without compromising the ductility and stiffness.
 The use of conventional 900 bent hook anchorage arrangements in the beam–column connection
region for severe earthquake leads to an increase in size of column to accommodate the required
amount of beam reinforcement in the joint core, whereas the use of mechanical anchorage results
in the reduction of reinforcement and rebar congestion in the joint core area. The mechanical
anchored bar is a viable alternative to the use of conventional 900 bent hook anchorages.

 Future scope
 In Indian design practice, beam-column joints are given less attention. The above finding, recent
research and suggestions by various national and international codes for using the mechanical
anchorage systems may be accounted for in the upcoming revisions.
 To try for different type of heads and diameter of reinforcement bar.

REFERENCES
• John w. Wallace, Scott w. McConnell“use of mechanically anchored bars in exterior beam-column
joints subjected to subjected to seismic loads” Erico inc., solon, ohio- 1997
• Wallance, J.W., McConnell, S.W., Guta, P., Cote, P.A., 1998. Used of headed reinforcement in
beam–column joints subjected to earthquake loads. ACI Structural Journal 95 (5), 590–606.
• Kang TH-K. Recommendations for design of RC beam-column connections with headed bars
subjected to cyclic loading. The 14th world conference on earthquake engineering (14WCEE),
Beijing, China (Paper No. 08–01-0017); 2008b.
• Kang, T. H.-K.; Ha, S.-S.; and Choi, D.-U., “Seismic Assessment of Beam-to Column Interactions
Utilizing Headed Bars,” Proceedings of the 14WCEE, Beijing, China, Oct. 2008, 8 pp. (Paper No.
05-03-0047).
• Lee, H.-J., Yu, Si-Ying, 2009. Cyclic response of exterior beam–column joints with different
Anchorage methods. ACI Structural Journal 106 (3), 329–339.
• Kang, T.H.-K., Shin, M., Mitra, N., Bonacci, J.F., 2009. Seismic design of reinforced concrete
beam–column joints with headed bars. ACI Structural Journal 106 (6), 868–877.
• Thomas H.-K. Kang, Nilanjan Mitra “Prediction of performance of exterior beam-column
connections with headed bars subject to load reversal” Engineering Structures – April 2012

• S. Rajagopal , S. Prabavathy “Investigation on the seismic behavior of exterior beam–column joint
using T-type mechanical anchorage with hair-clip bar” Journal of King Saud University
“Engineering Sciences” - September 2013
• S. Rajagopal , S. Prabavathy “Exterior beam-column joint study with non-conventional
reinforcement detailing using mechanical anchorage under reversal loading” Indian Academy of
Sciences - October 2014
• S. Rajagopal , S. Prabavathy “Seismic behavior of exterior beam-column joint using Mechanical
anchorage under reversal Loading: an experimental study” The Islamic Republic of Iran, 2014
• Vaibhav R. Pawar, Dr. Y.D.Patil, Dr. H.S.Patil “Cyclic loading of Exterior Beam - Column Joint
with Threaded Headed Reinforcement” International Journal of Applied Engineering – 2017
• ACI Committee 318 (2014). Building code requirements for structural concrete (ACI 318-14) and
commentary (318R-14). Farmington Hills, Mich., U.S.A.
• Joint ACI-ASCE Committee 352 (2002). Recommendations for design of beam-column
connections in monolithic reinforced concrete structures (ACI 352R-02). Farmington Hills, Mich.,
U.S.A.
• IS-1893, 2002. Indian Standard Code on Criteria for Earthquake Resistant Design of Structures,
Code of Practice. Bureau of Indian Standards, New Delhi, India.
• IS-13920, 2016. Indian Standard Ductile Detailing of Reinforced Concrete Structure Subjected to
Seismic Forces, Code of Practice. Bureau of Indian Standards, New Delhi, India.
• IS-456, 2000. Indian Standard Plain and Reinforced Concrete, Code of Practice. Bureau of Indian
Standards, New Delhi, India.

Experimental Investigation of Reinforcement Couplers as Replacement of Bent Bar

Recommended

Recommended

More Related Content

What's hot

What's hot (18)

Similar to Experimental Investigation of Reinforcement Couplers as Replacement of Bent Bar

Similar to Experimental Investigation of Reinforcement Couplers as Replacement of Bent Bar (20)

Recently uploaded

Recently uploaded (20)

Experimental Investigation of Reinforcement Couplers as Replacement of Bent Bar