Totally Prefabricated Counterfort Substructure System for

National University Rail Center
Totally Prefabricated Counterfort
Substructure System for Highway and
Railway Applications
Maen Farhat, University of Illinois at Chicago
Momenur Rahman , University of Illinois at Chicago
Prof. Mohsen Issa, University of Illinois at Chicago
NURail Annual Meeting 2014
Altoona, PA
August 19, 2014
Slide 1
NURail Center
Motivation
Continuous need to:!
¢  Provide
additional
highways and railroad
track bridges!
¢  Enhance
existing!
Fast and
Easy
Construction
Quality
control
Most important
Slide 2
¢  Railway
¢ 
system upgrade!
Environmental Issues!
¢  Economic
Easy
Maintenance
Efficiency!
Economy
Safety and
cost
reduction
NURail Center
Overall Objectives
Design and construct a Totally Precast
Counterfort retaining Wall system that will: !
Optimize the design and constructability
Achieve strength, durability and
serviceability requirements
Promote fast track construction, safety
and economy
Slide 3
NURail Center
What is Totally Prefabricated Concrete
Counterfort Retaining Wall system (TPCCRW)
FRONT ELEVATION
SIDE ELEVATION
Components:!
Two Prefabricated entities: !
•  The face wall stem cast integrally with three
counterforts !
•  Base slab!
Slide 4
NURail Center
What is TPCCRW?
1 2
3
4 5
Counterfort and face panel
during transportation!
Key Features:!
•  Headed anchors used to connect each precast counterfort to
the base slab. !
•  Inclined main reinforcement in the counterfort!
•  Counterfort is designed as T-section!
•  Base slab was designed with shear pockets to accommodate
the embedment length of the anchors!
NURail Center
Slide 5
Deflection of the wall
At service load!
Deflection contour at
service load (144 kip)
Slide 6
NURail Center
Strain Results in the Anchors
Anchor 1
Anchor 2
Anchor 4
Anchor 5
Anchor 3
250
Load (Kip)
200
Anchors 1
and 2 cross
the yield
point!
150
100
50
Yield line for
steel!
0
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
Strain (in/in)
The load vs. strain curves indicate that the first two #7 anchors
yielded while the other three #6 bars did not yield and showed a
decreasing strain reading as we come closer to the face of the
wall.
NURail Center
Slide 7
Crack propagation
All red marks represent cracks!
(a) Crack propagation at 67
Kips!
Slide 8
(b) Crack propagation at
144 Kips (service load)!
(c) Crack propagation at!
230 Kips (Ultimate load)!
NURail Center
Fabrication of wall components
Slide 9
NURail Center
Erection
Slide 10
NURail Center
Testing Procedure
Soil Backfilling
Soil pressure was applied by filling the
back of the retaining wall with soils
Surcharge Load
Surcharge was applied using Dozers to
simulate the actual condition for live load
Test 1
Two Hydraulic cylinder were used to apply
load up to 178000 lbs. at H/3 and 16000
lbs at top
Test 2
Hydraulic cylinder up to 136000 lbs. at H/3
Test 3
Hydraulic cylinder up to 97000 lbs. at H/3
Test 4
Hydraulic cylinder up to 192400 lbs. at H/3
Slide 11
NURail Center
Testing setup
Testing
setup
Slide 12
Backfilling
Live Load
Surcharge
Loading
beam
Hydraulic
Cylinders
NURail Center
Deflection results
Deflection
measured by the
3 LVDTs at H/2!
Deflection
measured by the
4 LVDTs at H/3!
Slide 13
NURail Center
Strain results in the anchors
3000
2659
2421
2000
2010
1748
1599
1292
Number of Anchors from
furthest to closest to face of
0 wall
1
2
3
4
Number of Anchor
Slide 14
836
1189
Anchor 5 (#6)
Anchor 4 (#6)
500
internal face
of wall
Anchor 3 (#6)
1000
Linear (Left Counterfort)
2203
Anchor 2 (#7)
1500
Anchor 1 (#7)
Maximum Strain, mε
2500
Linear (Middle counterfort)
Linear (FEA of Middle counterfort)
778
5
6
NURail Center
Strain readings in Counterforts’ main
reinforcement
2500
2000
Strain, mε
1st Test
Live Load
surcharge
1500
Left Counterfort
2nd Test 3rd Test
4th Test
Soil
Backfill
1000
500
0
0
-500
48
96
144
192
240
Elapsed Time, hrs.
288
336
Yielded in the same fashion with anchors supporting the design assumptions.!
Cracks developed in the concrete due to high overturning moment resisted
by the T-section of the counterforts and the face-panel.!
Slide 15
NURail Center
Conclusions
1. TPCCRW exhibited good performance in resisting applied loads.
2. Stability and strength requirements were satisfied at service and
ultimate loads as per AREMA and AASHTO LRFD.
3. The main reinforcement in the counterforts showed a good
performance as expected.
4. The anchors showed excellent performance in maintaining the
composite action between the precast wall and the base slab at
service and ultimate loads
5. The L-bars was found to be very effective in maintaining the
composite action between the face panel and the counterforts
6. TPCCRW can be utilized for highway applications. It
satisfies the need for fast track construction.
Slide 16
NURail Center
Future work
•  Experimental testing and FEA modeling the pullout
behavior of the anchors using precast concrete blocks
designed specifically for this purpose (in progress)
•  Expand the design to cover performance against crash
test at the level of the barrier on top of the wall
•  Expand the design to cover abutments as part of Fast
Track Construction
•  Final design procedure based on AREMA
Requirements for rail road loads
Slide 17
NURail Center
National University Rail Center
THANKS FOR YOUR
ATTENTION!
Acknowledgements and Support!
“This project was supported by the National University Rail
(NURail) Center - a US DOT RITA University
Transportation Center"!
Utility Concrete Products (UCP)!
“Special Thanks to UCP for their support”!
Slide 18
NURail Center