The document discusses retrofitting of broken rebar piles during construction of a bridge foundation in Bangladesh. During construction, some rebar piles broke when the pile heads were cut off. The contractor proposed using mechanical couplers and epoxy to splice the broken rebar and add new inner core rebars. The design consultant approved this approach but recommended deeper epoxy insertion and adding stiffener rings and spiral reinforcement. Pictures show the repaired pile heads. The project aimed to strengthen broken piles in a cost-effective way while meeting design requirements.

1. WELCOME
CONSTRUCTION SUPERVISION CONSULTANT,PMBP
BANGLADESH ARMY

2. RETROFITTING OF BROKEN RE-BARS DURING
CONSTRUCTION OF PILES
FOR
BRIDGE FOUNDATION

3. INTRODUCTION

4. RETROFITTING: Modifying existing equipment or structures
with additional or new components or members.
SPLICING: Connection of existing broken re-bar with
additional rebar by coupler.
COUPLER: A Mechanical device that connects two thing.
EPOXY-TIE ADHESIVE: Epoxy-Tie (ET) is a two-component,
100% solid system for uses as a high strength, non-shrink
anchor grouting material.
TERMINOLOGIES

5. A CASE STUDY
ON
SIKDERKANDI BRIDGE PILE

6. INCIDENT
 At Sikderkandi Bridge 48 numbers (4x12) of pile under 4
piers and 36 numbers (18x2) of pile under 2 abutments
were designed.
 For the pier piles 16 numbers of 32 mm and for abutment
piles 23 numbers of 32 mm re-bars were used.
 500 grade Anwar Ispat bars were used in the construction
work. All procedure had been followed for source approval.
The 500 grade Anwar Ispat bars were tested from BUET.
The test result was satisfactory.

7.  After curing period pile heads were broken at the cut off
level for onward construction of pile cap.
 Pile heads were broken by using concrete breaker
(Pneumatic Drill) and then upper concrete portion were
removed by crane.
 During breaking of pile heads some of the re-bars in
number of piles were broken.
INCIDENT

11. Sl.
No
Structures Pile no
of
Broken
Bars
Total
Bars
per pile
No of
Bars
broken
per pile
% of
broken bars
per pile
No of
Piles per
cap
No of
bars per
cap
% of
broken
bars for
cap
Rmks
1
Abutment-1
Pile-2
23
1 4.35
2.17
Narrow
Bridge
2 Pile-5 3 13.04
Wide
bridge
3 Pile-10 3 13.04 18 414
4 Pile-12 1 4.35
5 Pile-13 1 4.35
Total Numbers of Broken Bars, AB-1= 9
6
Abutment-2
Pile-1
23
1 4.35
7.49
Narrow
Bridge7 Pile-2 2 8.70
8 Pile-10 5 21.74 18 414
Wide
bridge
9 Pile-12 5 21.74
10 Pile-13 6 26.09
11 Pile-14 10 43.48
12 Pile-15 2 8.70
Narrow
Bridge
Total Numbers of Broken Bars, AB-2= 32
STATISTICS OF BROKEN BARS
ABUTMENT

12. STATISTICS OF BROKEN BARS
Sl.
No
Structures Pile no
of
Broken
Bars
Total
Bars
per pile
No of
Bars
broken
per pile
% of
broken bars
per pile
No of
Piles per
cap
No of
bars per
cap
% of
broken
bars for
cap
Rmks
13 Pier-1 Pile-10 16 1 6.25 12 192 0.52
Narrow
Bridge
Total Numbers of Broken Bars, Pier-1= 1
14 Pier-2 Pile-4 16 3 18.75 12 192 1.56
Narrow
Bridge
Total Numbers of Broken Bars, Pier-2= 3
15
Pier-3
Pile-1
16
4 25.00 Narrow
Bridge
16 Pile-2 2 12.50
17 Pile-3 3 18.75 12 192 5.21 Wide
Bridge18 Pile-4 1 6.25
Total Numbers of Broken Bars, Pier-3= 10
19 Pier-4 Pile-1 16 1 6.25 12 192 0.52
Narrow
Bridge
Total Numbers of Broken Bars, Pier-4= 1
 Total no of Bars for the Bridge - 1596 nos
 Total no of Bars Broken for the Bridge - 55 nos
 % of Broken Bars for the Bridge - 3.45 %
 No of Pile for bars Broken - 19 nos
PIER

13. Sl.
No
Structure
Name
Total Piles
per
Structure
Total Bars
per
Structure
Numbers
of Bar
Broken
% of
Broken
Bars
Rmks
1. Aboutment-1 18 414 9 2.17
2.
Aboutment-2
18 414 31 7.49
3. Pire-1 12 192 1 0.52
4. Pire-2 12 192 3 1.56
5. Pire-3 12 192 10 5.21
6. Pire-4 12 192 1 0.52
Total 84 1596 55 3.45
STATISTICS OF BROKEN BARS

14. EXPLANATION OF CONTRACTOR
Likely Reason for Breaking of Re-bar
About 1.0 m long segment of pile head was broken by
removing skin concrete from the pile re-bar above the cut-off
level and further about 50 mm thick concrete was taken out
inside the core of every individual re-bar at 100 mm above
the cut-off level. Electric drill was used for breaking the
concrete.

15. Likely Reason for Breaking of Re-bar
Single piece of concrete (approx 4.0 ton) was taken out from
the pile head by Crane. During the process of removal of the
broken concrete from pile head, few main 32 mm diameter
re-bar were broken at cut-off level due to lateral pressure
which may be called Cold Shear Cut of bar.
EXPLANATION OF CONTRACTOR

16. Contractor’s Proposal to Prevent Breaking of
Re-Bar in Future
Previously minimum 1.0 m length of pile head used to be
broken by removing skin concrete from the pile above
the cut-off level. In future pile head shall be broken 300
mm above the cut-off level by removing skin first and
then 50 mm thick concrete will be broken out from inside
the core of the pile. Thus the core concrete will get
free which will be broken by electric drill.
EXPLANATION OF CONTRACTOR

17. Contractor’s Proposal to Prevent Breaking of
Re-Bar in Future
Then the single piece of concrete will be taken out from
the pile head. Removal of rest 300 mm will be done by
using chisel upto the cut-off level with care.
EXPLANATION OF CONTRACTOR

18. 1. Extension of broken re-bar will be done by mechanical
splicing system (DEXTRA’s Unitec co-axial) consisting of a
sleeve that is fitted with one longitudinal row of redial bolts
through its wall thickness and 2 longitudinal saddles insides
its inner cavity.
2. Existing broken re-bar will be exposed by removing the
concrete around the broken re-bar upto 150 mm depth over
which the coupler of the splicing system is inserted until
contact with centre pin.
CONTRACTOR’S PROPOSED
RETROFICATION SYSTEM

19. 3. The end of the other reinforcing bar is inserted into the
sleeve until contact with a centre pin.
4. The bolts are first hand-tightened with an L-wrench for
pre-locking, and then tightened with a pneumatic ¾’’ power
drive until the heads of the screws shear off.
5. In addition re-bars of same diameter (32 mm) to be
anchored chemically with a 40 mm dia hole, at depth of 350
mm @ 150 mm spacing as technically specified in the
manual of Simpson ET-HP Epoxy.
CONTRACTOR’S PROPOSED
RETROFICATION SYSTEM

20. COMMENTS OF CSC DESIGN
CONSULTANT
The comments and recommendations of CSC design
consultant were as follows:
 The damages were caused by heavy and hard impact
from pile head concrete mass during removal process.
 All other secondary reasons might weaken the re-
bars but not adequate for breaking 32 mm dia re-
bars.
 Replenishment of re-bars by DEXTRA’s Unitec co-
axial mechanical splicing is OK.

21.  Retrofitting with 16-32 mm re-bars as inner core is
OK both for abutment and pier piles. The depth of
insertion shall be 400 mm in place of 350 mm as
shown on the drawing for SIMPSON ET22 Epoxy-Tie
Adhesive.
 After fixing inner core re-bars, 4 numbers of Stiffener
Rings shall be provided as inner ring along the 1.0 m
extended bars. Spiral of 12 mm bar at 75 mm pitch
shall be provided as outer ring around the existing re-
bars.
COMMENTS OF CSC DESIGN
CONSULTANT

22. PICTORIAL VIEW OF PILE HEAD WITH
BROKEN BARS AFTER RECTIFICATION

23. PLAN OF THE PILE WITH
BROKEN BARS

36. CONCLUSION