TIMBER RAILROAD BRIDGES

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