In structural concrete, the provisions for anchorage of straight bars and hooks normally present detailing problems due to conjunction of reinforcement bar. Mechanical anchorage device eliminates detailing problems when conjunction of reinforcement bar. This paper represents the various method of mechanical anchorage and past work carried out on mechanical anchorage which shows the effectiveness of mechanical anchorage method over the most commonly used method.

1. “Critical Review on
Mechanical Anchorage as
Replacement of Bent Bar”
Presented By : Rohitkumar A. Pandey

2. Contents
• Introduction
• Type of Mechanical Anchorage
• Laboratory Based Testing Setup
• Review of Literature
• Summary of Finding

3. Introduction
• The detailing problems related to
anchorage of reinforcement bars in RC
structure.
• In middle of the 20th century develop a
method we known as mechanical
anchorage.

4. Type of Mechanical Anchorage
• Friction-welded anchorage
– pressing the end of a deformed reinforcing bar onto a plate spinning at very high speed.
– shapes: square, rectangular, circular, and oval
• Thread anchorage
– More efficient stress transfer than conventional straight thread connections.
– Threading may be accomplished in the field. all that is needed is the Terminator nut and a
torque wrench.

5. Laboratory Based Testing Setup
• The Joint assemblage was subjected to monolithic loading using Hydraulic jack of 25 Ton
capacity.
• The specimen column is kept in horizontal direction and beam is kept vertical as illustrated in
Fig . Both ends of the RCC columns are restrained in vertical and in both horizontal directions
by using strong built up steel boxes which in turn are connected to the reaction floor using
holding down anchor bolts.
• To facilitate the application of monolithic load Standard hook Thread anchorage Straight bar
anchorage Welded anchorage on either side of the RCC beam, hydraulic jacks are used which
are connected to the strong steel frame using mechanical fasteners and the RCC beam was
loaded as shown in Fig .
• The Linear Variable Differential Transducer (LVDT) was connected on either side of the
specimen to monitor the displacements. To record the loads accurately, the specimen was
tested to reach its maximum failure load.

7. Review of Literature

8. 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

9. 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. Wallace to evaluate the applicability
of mechanically anchored bars with
diminutive heads in exterior beam-column
joints.
•The research program consisted of testing
two exterior, five corner joint, full-scale,
beam-column joint sub assemblages.
•One of the specimens was subjected to cyclic
load whereas the other specimen was
subjected to essentially monotonic load .
TEST SETUP
Exterior Roof Connections

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

11. Paper 3 : “Seismic Assessment of Beam-to-Column Interaction
Utilizing Headed Bars” Thomas H.-K. Kang, Sang-Su Ha, Dong-Uk Choi,
The 14thWorld Conference on Earthquake Engineering, October 2008
• A total of twelve pullout tests
and two, full-scale, cyclic
beam-column joint tests.
• Carried out to examine
pullout and seismic anchorage
demeanor of headed bars.
• The seismic tests designated
that both beam-column joints
failed in a ductile manner,
exhibiting kindred patterns of
cracking and the same level
of lateral strength.
• The joint utilizing headed
bars showed better seismic
performance in terms of the
damage extent, lateral drift
capacity and energy
dissipation, compared with
that utilizing hooked bars.

12. • the head size of at least 2.6 was
efficacious to achieve adequate
anchorage.
• the development length was 10db.
• The loading condition, head shape, and
head-annexing technique did not impact
the anchorage deportment substantially
during pullout.
• The exterior joint containing headed bars
with a development length of 15db and
with head size of approximately 3 was
capable of transferring probable moments
and forces in the members without loss
up to 3.5% drift.
• This denotes that reduced joint
confinement does not impact adversely
on the headed bar anchorage in inter-
story joints, likely due to the bearing
stress acting against the concrete above
the joint.
Dimenation of specimens

13. Paper 4 :“Cyclic Response of Exterior Beam-Column Joints with
Different Anchorage Methods”Hung-Jen Lee and Si-Ying Yu,
Aci-structural journal MayJune 2009
• Six exterior beam-column joints with
or without eccentricity to evaluate
the utilization of mechanical
anchorages in lieu of hooked bar
anchorages.
• Eccentric beam-column joints with
mechanical anchorages can exhibit
satisfactory performance and
adequate anchorage capacity for a
inhibiting drift ratio.
• To conduct design as par ACI code.
• Test results withal betoken that the
cyclic demeanor of exterior beam-
column joints can be significantly
amended by annexing double
mechanical contrivances on each
beam bar within the joint. Details of mechanical devices for test specimens

14. • The experimental data showed that
double mechanical contrivances could
obviate push-out on the back of the joint
and reduce the yield perforation and
bond deterioration along the beam bar
into the joint.
• The degradation of potential joint shear
capacity could be delayed beyond the
constraining drift ratio of 4%.
• Shear stresses computing as per as ACI
352R-0210.
• The side-face blowout failure was not
observed during tests of eccentric beam-
column joints with mechanical
anchorage, even though there was only
3db side cover for the extreme headed
bar without any supplemental restraining
stirrups.
• It is concluded that the minimum clear
spacing of 4db between headed bars
could be further reduced for longitudinal
beam bars terminated within a perpetual
column.
Test setup and loading procedure

15. Paper 5 : “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

16. • 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.

17. Paper 6 : “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

18. • 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.

19. Paper 7 : “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

20. • 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.

21. Paper 8: “Cyclic loading of exterior beam - column joint with threaded
headed reinforcement” Vaibhav R. Pawar, Dr. Y.D.Patil, Dr. H.S.Patil ,
International Journal of Applied Engineering – 2017
• In many cases, the requisites for straight
bar anchorage and lap splices cannot be
provided within the available dimensions
of elements.
• Hooked bars can be acclimated to
abbreviate anchorage length, but in many
cases, the bend of the hook will not fit
within the dimensions of a member or the
hooks engender congestion and make an
element arduous to construct.
• Experimental work was conducted on
exterior beam-column joint specimens
with T-type mechanical anchorage.
Welded and threaded anchorage
reinforcement bars were utilized as T-type
anchorage with short development length.

22. • The result from 1/3 scale seismic testing of a joint with mechanical anchorage were evaluated
by compression with a companion specimen with hooked bars and by utilizing the acceptance
criteria of ACI 374.1-05.
• No brittle concrete brake out occurred for any mechanical anchorage in pullout, provided that
the anchorage size was at least 2.5 and embedment depth was 11db.
• This implicatively insinuates a possibility that the amount of transverses reinforcement in the
exterior inter-story joint may be reduced when mechanical anchorages are utilized.

23. Summary of Findings
• The net bearing area of an anchorage is suggested to be at least three times the bar area for the
design of beam-column joints. The data of beam column joints subject to cyclic loading
provide a means to update both ACI code .
• The transverse reinforcement within the joint region should be positioned essentially inline
with the mechanically anchored bars to restrain the heads from pushing off the cover concrete
as well as to provide lateral stability to the column vertical bars.
• 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.

24. Thank you