1. Causes of Bumps at Pavement-Bridge Interface
AKM Anwarul Islam, Ph.D., P.E.
Associate Professor
Youngstown State University
Amar Shukla
Graduate Student
Presenter: Amar Shukla
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2. Youngstown State University
Definition of Bumps
Differential settlement of bridge and approach slab and/or approach slab and pavement
Approach slabs are provided for smooth transition of vehicles
Briaud et al. (1997) summarized that 25% of total bridges in the USA had bridge bumps that cost almost $100 million per year for repair
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3. Youngstown State University
Behavior of approach slab due to pavement settlement and bump mechanism
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4. Youngstown State University
Goals of Research
Cost-effective solution to the existing problems of the bumps
Reduce safety hazards and maintenance cost
Smoother ride to drivers
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5. Youngstown State University
Causes of Bumps
Movement of soil beneath slab
Strength deficient approach slabs
Continual impact of vehicles running over already compacted area
Insufficient compaction of soil especially of the embankment backfill
Types of soil
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6. Causes of Bumps (contd.)
Short-term and long-term settlement
Bridge-end conditions
Construction methods, roadway paving and bridge/roadway joint
Water seepage
Traffic volume
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7. Experimental Investigations
2 bridges with bumps and 3 bridges without bumps were visited
Atterberg Tests (Liquid Limit and Plastic Limit) and Sieve Analysis tests were conducted
Soil samples were collected from the surface
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8. Experimental Investigations (contd.)
Results on
Bridges without bumps
Bridges with bumps
COL
COL
COL L
COL
COL
Liquid Limit
34.1
21.5
24.9
33.6
32.2
Plastic Limit
24.5
25.5
21.9
30.7
38.4
Plasticity Index
9.6 NP
3.4
2.9
AASHTO Soil Classification
A-2-4 (0)
A-3 (0)
A-1-b (0)
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9. Experimental Investigations (contd.)
Soil is granular
Various methods through which proper compaction of granular soil can be obtained:
Pneumatic rubber-tired rollers
Vibratory rollers
Handheld vibrating plates
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10. Approach slab designs in state DOTs
Lmin (ft) h
(in)
fc‘
(ksi) As
(in2/ft)
As’ d‘ Cc
Φ Mn
(k*ft/ft) Mu AZ 15 12 3
1.053
0.133
2.5
37.57
9.77
FL* 30
4.5
0.310 4
32.57
80.03 IN 20 10
0.630
0.203 2
19.14
30.16 KY 25 17
3.5
1.58
90.10
61.72
MI*
0.895
21.87
31.72 OH
2.345
0.207
129.81
90.4 PA 16
1.693
0.31
85.22
60.5
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11. Youngstown State University
Geometric Parameters
Approach slab of L = 30 ft. and B = 20 ft.
Bottom Steel: #10 reinforcing 6.5 in. c.c.
Top Steel: #5 reinforcing 18 in. c.c.
Bent Steel: #5 reinforcing in. c.c.
Vertical Steel: #5 reinforcing 6 in. c.c.
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12. Youngstown State University
Model Parameters
Surface to surface contact b/w approach slab and sleeper slab
Bonded contact b/w approach slab and end bent
HL-93 truck single lane loading conditions
Model was built as a simple supported
2 models were built considering soil underneath and soil completely moved out
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13. Model with soil underneath
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14. Model without soil underneath
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15. Analytical Simulation Results
Soil underneath slab:
Deflection = in.
Maximum Beam Stress = lb/in2.
Soil moved out
Deflection = in.
Maximum Beam Stress = lb/in2.
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16. Approach Slab Model under HL-93 with soil underneath
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17. Approach Slab Model under HL-93 without soil underneath
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18. Recommendations for Ohio Approach Slab
ΦMn calculated by using ODOT specs. = kip-ft.
Mu calculated by using ALGOR values = kip-ft.
Design of approach slab
L = 30 ft. B = 20 ft.
Bottom reinforcement = 5.5 in c.c
Top reinforcement = 18 in c.c.
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19. Youngstown State University
References
American Association of State Highway and Transportation Officials, LRFD Bridge Design Specifications, 4th edition, 2007.
Briaud, J. L., James, R. W., and Hoffman, S. B. (1997). NCHRP synthesis 234: “Settlement of Bridge Approaches (the bump at the end of the bridge),” Transportation Research Board, National Research Council, Washington, D.C., 75 pp.
Cai, C.S., Voyiadjis, G.Z., and Shi, X. (2005). “Determination of Interaction between Bridge Concrete Approach Slab and Embankment Settlement,” Report No. FHWA/LA. 05/403, Louisiana Transportation Research Center, Louisiana Department of transportation, 152 pp.
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20. Causes of Bumps at Pavement-Bridge Interface
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