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TIMBER RAILROAD BRIDGESTIMBER RAILROAD BRIDGES
Terry WipfDoug WoodBrent Phares
Iowa State University
Mike RitterForest Products Laboratory
OVERVIEWOVERVIEW
Timber used in RR bridges more than 100 years (many still in service)Solid sawn lumber superstructuresRailroads need to be made aware of value of glued laminated options for rehabilitation and new constructionResearch and education needed to identify most cost effective options
PERTINENT PAST/CURRENT PERTINENT PAST/CURRENT ACTIVITIESACTIVITIES
Testing and evaluation of RR bridges in TexasTesting and evaluation of RR bridge in Washington stateResearch needs study
BACKGROUNDBACKGROUND--Testing and Testing and Evaluation of RR BridgesEvaluation of RR Bridges
Existing timber bridges on SP railway lineLong term performance – >60 years
Recent heavy axle loads Condition assessment Rehabilitation program to strength existing bridge (evaluation of effectiveness)
OPEN DECKOPEN DECK
Packed Chord
TieOpen Deck
Bent Bent Bent Bent
Packed Chord
BALLAST DECKBALLAST DECK
Ballast Deck
Typical Damage and DeteriorationTypical Damage and Deterioration
Existing Stringer ConditionExisting Stringer Condition
Can’t see interior stringers when in place
““ExperimentalExperimental”” Usage of Glued Usage of Glued Laminated StringersLaminated Stringers
RESEARCH PROGRAMRESEARCH PROGRAM
D’Hanis bridge testTest trainRevenue trafficStatic and dynamic loadsDeflections, accelerations and wheel loads
Civil and Construction Engineering
DD’’HANIS BRIDGEHANIS BRIDGE
approx. 165'-8"
Span 8
Span 2
Bent 2test spans
helper bent
DD’’HANIS BRIDGEHANIS BRIDGE
Cross Section - Span 8
4 stringer chord(glued laminated)
4 stringer chord(sawn)
DD’’HANIS BRIDGEHANIS BRIDGE
Cross Section - Span 2
4 stringer chord(glued laminated)
helper stringer
5 stringer chord (sawn)
Glued laminated packed chord
Solid sawn chord with helper
INSTRUMENTATIONINSTRUMENTATION
STRINGER 8
STRINGER 1
SPAN 8BENT 9 BENT 8
displacement transducer
accelerometer
Measuring Shear DeformationsMeasuring Shear Deformations
Instrumented Rails for Load Instrumented Rails for Load EstimationEstimation
Controlled Test TrainControlled Test Train
LOAD TEST RESULTSLOAD TEST RESULTSTest Train Wheel LoadsTest Train Wheel Loads
16 18 20 22 24 26
0
10.0
20.0
30.0
40.0
50.0 DRGW25101
SPMW4337
SPMW4345
EMD6870
Whe
el lo
ad (k
ip)
Time ( sec.)
LOAD TEST RESULTSLOAD TEST RESULTSDynamic Load FactorDynamic Load Factor
Velocity(mph)
MaximumWheel Load
in Span 8(kips)
MaximumWheelLoad
in Span 2(kips)
MaximumWheel Load
on Approach (kips)
Span 8DLF
Span 2DLF
ApproachDLF
crawl
15
30
40
41.0
41.6
41.6
41.0
40.0
40.7
46.8
40.7
40.0
39.8
42.8
53.1
-
1.02
1.01
1.00
-
1.02
1.17
1.02
-
1.00
1.06
1.32
LOAD TEST RESULTSLOAD TEST RESULTS
60 80 100 120 140-0.250
-0.200
-0.150
-0.100
-0.050
0.000
0.050
Def
lect
ion
(in)
Time (sec)8 9 10 11 12 13
-0.250
-0.200
-0.150
-0.100
-0.050
0.000
0.050
Def
lect
ion
(in)
Time (sec)
Slow Fast
LOAD TEST RESULTSLOAD TEST RESULTSDynamic Amplification FactorDynamic Amplification Factor
Test TrainVelocity(mph)
15
30
40
Test TrainVelocity
DAF
Span 2 Span 8
NorthChord
SouthChord
NorthChord
SouthChord
1.00 1.05 1.00 1.00
1.15 1.05 1.07 1.01
1.22 1.06 1.14 1.07
Span 2 Span 8
NorthChord
SouthChord
NorthChord
SouthChord
1.00 1.05 1.00 1.00
1.15 1.05 1.07 1.01
1.22 1.06 1.14 1.07
LOAD TEST RESULTSLOAD TEST RESULTSSpan 8Span 8
7 8 9 10 11 12-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
Def
lect
ion
(in)
Time (sec.)7 8 9 10 11 12
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
Def
lect
ion
(in)
Time (sec.)
Sawn Chord Glulam Chord
LOAD TEST RESULTSLOAD TEST RESULTSSpan 2 vs. Span 8Span 2 vs. Span 8
7 8 9 10 11 12-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
Def
lect
ion
(in)
Time (sec.)8 9 10 11 12 13
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
STRINGER HDef
lect
ion
(in)
Time (sec)
Sawn ChordSpan 8
Sawn ChordSpan 2
LOAD TEST RESULTSLOAD TEST RESULTSSpan 2Span 2
8 9 10 11 12 13-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
STRINGER H
Def
lect
ion
(in)
Time (sec)8 9 10 11 12 13
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
Def
lect
ion
(in)
Time (sec)
Sawn Chord Glulam Chord
LOAD TEST RESULTSLOAD TEST RESULTSSpan 8 Span 8 -- GlulamGlulam
0 10 20 30 40 50 60 70 80-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1D
efle
ctio
n (in
)
Time (sec)
ExperimentalAnalytical - ContinuousAnalytical - Simple
Research Needs StudyResearch Needs Study
Currently in progressSeeking to define what research is needed to advance the use of timber by railroads