AASHTO AS 13 -0024sp.bridges.transportation.org/Documents/2016... · 2017-01-26 · 1 Presented to AASHTO T-8, June 28, 2016 AASHTO AS 13 -0024 Support for the HSCOBS Technical Committee

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Presented to AASHTO T-8, June 28, 2016

AASHTO AS 13-0024Support for the HSCOBS Technical Committee on Moveable Bridges (T-8) in a Technical Advisory Role for Specification Updates – Span Lock Design Study

By James M. Phillips III, PEHardesty & Hanover, Tampa, FL

STUDY TEAM

Hardesty & Hanover, LLC• Rafal Wuttrich, PE – Lead Finite Element Modeling

AECOM (formerly URS and E.C. Driver & Associates, Inc.)• Jim Englert, PE – Project Manager• Michael Reponen – Finite Element Modeling

• FDOT• Will Potter, PE - Structures Research – Field Instrumentation and Testing

AGENDA

Review Purpose of Study Study Limitations Sunrise Blvd. Field Tests Summarize Key Findings Present Recommendations

PURPOSE OF STUDY

4

Advance knowledge of span lock behavior Provide recommendations to T-8 Improve the general practice of span lock design Improve AASHTO LRFD Movable Highway Bridge

Design Specifications Determine appropriate impact factors Quantify the effects of operating clearances and

wear Quantify the effects of bascule span deflection Identify alternative materials

Photo 3 & 4 – Span Lock Housing (Left) and Bushing (Right) exhibiting severe wear of the turned bolt holes. Cortez Bridge, Manatee County, FL, FDOT District One; (December 2014, Hardesty & Hanover, LLC)

SCOPE LIMITATIONS

Double-Leaf Trunnion Bascule Bridge

Lock Bar Type Span Locks

SUNRISE BLVD. FIELD INSTRUMENTATION AND LOAD TESTING – 4/29/15

6

Strain Gauges: Outside Girder Span Lock; Outside Main Girders Tip Rotation via Displacement Transducers Variable Shimming of Live Load Shoe

SUNRISE BLVD. BRIDGESPAN LOCK INSTRUMENTATION & TESTING

7

FDOT Test Vehicle

Test Vehicle with 18 Block Loading

Axle P1 P2 P3 P4 P5

Load (P)(kips) 10.1 10.5 10.5 26.3 26.3

HL-93 Vehicle

Axle P1 P2 P3 P4 P5

Load (P)(kips) 8.0 16 16 16 16

SUNRISE BLVD.

8

Sunrise Blvd. Bridge30 MPH Test Outside Lane

18 Block Load

9

Sunrise Blvd. Bridge30 MPH Test

Inside Lane 18 Block Load

SUNRISE BLVD. BRIDGE – CONSISTENCY OF FIELD TESTS

10

-100

-80

-60

-40

-20

0

20

40

60

80

100

1 49 97 145

193

241

289

337

385

433

481

529

577

625

673

721

769

817

865

913

961

1009

1057

1105

1153

1201

1249

1297

1345

1393

1441

1489

1537

1585

1633

1681

1729

1777

1825

1873

1921

1969

2017

2065

2113

2161

2209

2257

2305

2353

2401

2449

2497

2545

2593

2641

2689

2737

2785

2833

2881

2929

2977

3025

3073

Mic

rost

rain

Time Interval

Chart E30mph Runs in Outside Lane

Comparison of Strain in Lock Bar for 4 Tests Sunrise Blvd. Bridge Load Tests

18O301 S9 18O302 S9 18O303 S9 18O304 S9

KEY FINDINGS OF PROJECT

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Dynamic effects are significant The Shape of Wear Plates and Load Shoes affects contact stresses Secondary effects of deformations can be significant – especially

on the Forward Guides and Receivers Wear of lock components results in a general reduction in Lock

Effectiveness Improper Adjustment of Live Load Shoes (aka Live Load Bearings)

can have a measurable effect on Span Lock and Main Girder strains

DYNAMIC EFFECTS

AASHTO Table 3.6.2.1-1, Dynamic Load Allowance, IM

Components IM

Deck Joints – All Limit States 75%

All Other Components

Fatigue and Fracture Limit State

All Other Limit States

15%

33%

Article 2.4.1.2.4, End Floorbeams, of AASHTO Movable states:

“The end floorbeams of the moving span shall be proportioned for full factored live load plus twice the normal dynamic load allowance specified in Article 3.6.2 of the AASHTO LRFD Bridge Design Specifications.”

Article 6.8.1.5.1, Locking Devices, of AASHTO Movable states:

“Double leaf spans shall be provided with center locks to lock together the toe ends of the spans and tail locks or latches. Center locks shall transfer live load and impact from on leaf to the other.”

AASHTO Dynamic Load Allowance, IM

DYNAMIC EFFECTS

Dynamic Effect Calculated as Ratio of Measured Range of Strain for 30 MPH Truck / Slow Rolling Truck

The Dynamic Effect was consistently larger as the truck was moved away from the strain gauge of interest

Lock Bar Strains:• Dynamic Effect in the range of 1.17 to 1.58 for loading in the lane adjacent to the lock bar• Dynamic Effect in the range of 2.17 to 4.43 for loading in the lane opposite the lock bar

• Forward Guide and Receiver Strains:• Dynamic Effect in the range of 1.05 to 2.15 for loading in the lane adjacent to the lock bar• Dynamic Effect in the range of 1.49 to 4.25 for loading in the lane opposite the lock bar• The largest ratios were recorded in the forward guides on the side facing the center joint

HILLSBOROUGH AVE BRIDGESPAN LOCK INSTRUMENTATION & TESTING

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Lock Bar Strain - Static vs Dynamic Loading, Heavy Test Truck (37.5k Axle) Static is Slow Roll Across Span Dynamic is 30 MPH Across Span

Peak Strain Static vs Dynamic Comparison at Top of Lock Bar

Gauge Location Peak Static Strain

Peak Dynamic Strain

RatioDynamic/Static

Tension 108 117 1.08

Compression 209 325 1.55

Range 317 442 1.39N-1 is Located on Top of Lock Bar


15

-200

-150

-100

-50

0

50

100

150

200

160 11

917

823

729

635

541

447

353

259

165

070

976

882

788

694

510

0410

6311

2211

8112

4012

9913

5814

1714

7615

3515

9416

5317

1217

7118

3018

8919

4820

0720

6621

2521

8422

4323

0223

6124

2024

7925

3825

9726

5627

1527

7428

3328

92

Test 2 (Slow Roll) vs Test 5 (30 MPH)North Lock Bar Strain

18 Block Load, Outside Lane

N-1 T5 N-2 T5 N-1 T2 N-2 T2

Peak Strain Static vs Dynamic Comparison at Top of Lock Bar

Gauge Location

Peak Static Strain (T/C)

Peak Dynamic Strain

RatioDynamic/Static

N-1 Peak 143/75 170/113 1.18/1.51

N-1 Range 218 283 1.30

N-2 Peak 76/150 116/175 1.53/1.17

N-2 Range 226 291 1.29

Comparison of Strains in the Adjacent Lock Bar

Max. Stress Range = 8.4 ksi

N-1 is Located on Top of Lock Bar N-2 is Located on Bottom of Lock Bar

-150

-100

-50

0

50

100

150

Mic

roSt

rain

Time Interval

Test 2 (Slow Roll) vs Test 5 (30 MPH)South Lock Bar Strain

18 Block Load, Outside Lane

S-1 T5 S-1 T2 S-2 T2 S-2 T5


16

Peak Strain Static vs Dynamic Comparison, Receiver Housing

Gauge Location


Peak Dynamic Strain

RatioDynamic/ Static

S-1 Peak 50/25 129/63 2.58/2.52

S-1 Range 75 192 2.56

S-2 Peak 26/57 68/130 2.62/2.28

S-2 Range 83 198 2.39

Comparison of Strains in the Opposite Lock Bar

Max. Stress Range = 5.7 ksiHigher Dynamic Ratio, but lower overall strain

S-1 is Located on Lock Bar Above NA S-2 is Located on Lock Bar Below NA


17

Comparison of Strains in the Receiver Housing, Static vs DynamicPeak Strain Static vs Dynamic Comparison,

Receiver Housing

Gauge Location


Peak Dynamic Strain

RatioDynamic/Static

N-E Peak 4/23 7/35 1.75/1.52

N-E Range 27 42 1.56

N-H Peak 7/7 7/8 1.00/1.15

N-H Range 14 15 1.07-10

-5

0

5

10

15

20

25

30

35

40

1 32 63 94 125

156

187

218

249

280

311

342

373

404

435

466

497

528

559

590

621

652

683

714

745

776

807

838

869

900

931

962

993

1024

1055

1086

Receiver Strain Comparison Test 2 (Slow Roll)vs Test 5 (30 MPH)

North Lock Bar18 Block Load in Outside Lane

N-E T5N-H T2N-E T2N-H T5

Greater Dynamic Effect on Side Facing Center Joint

N-E is Located on Joint Side of ReceiverN-H is Located on Back Side of Receiver


18

Comparison of Strains in the Forward Guide Housing, Static vs Dynamic

Peak Strain Static vs Dynamic Comparison, Receiver Housing

Gauge Location


Peak Dynamic

Strain

Ratio Dynamic/

Static

N-C Peak 7/38 7/59 1.00/1.55

N-C Range 45 66 1.47

N-D Peak 4/18 3/31 0.75/1.72

N-D Range 22 34 1.55-20

-10

0

10

20

30

40

50

60

70

1 26 51 76 101

126

151

176

201

226

251

276

301

326

351

376

401

426

451

476

501

526

551

576

601

626

651

676

701

726

751

776

801

826

851

876

901

926

951

976

1001

1026

1051

1076

Guide Strain Comparison Test 2 (Slow Roll) vs Test 5 (30 MPH)North Lock Bar

18 Block Load in Outside Lane

N-C T5 N-D T5 N-C T2 N-D T2

N-C and N-D are Located on Joint Side of Forward Guide

LOAD SHOE / WEAR PLATE SHAPE

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Contact Stresses at the Lock Bar interface with the Wear Plates or Load Shoes are influenced by the Geometry and System Deformations

System DeformationsLock Bar Contact Stress

Load Shoe Contact Stress

LOAD SHOE / WEAR PLATE SHAPE

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Studied shapes of load shoes, from left: flat shape with radius on leading edge, round shape w/ large radius, compound shape (receiver shoe shown)

Figure 8a - Contact Stress on load shoes: flat shape with radius on leading edge

Figure 8b - Contact Stress on load shoes; round shape w/ large radius

Figure 8c - Contact Stress on load shoes; compound shape

72” Radius Effective In Reducing Edge Loading

STRUCTURAL DEFORMATIONS - GIRDER ROTATION AT THE SPAN LOCKS

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Sunrise Bridge Tests Included Measurement of End Rotations (Relative Slope Between Leaves)

For the Test Load in the Lane Adjacent to the Instrumented Lock/Girder Relative End Rotation Measured 0.0047 in/in for Static Loading and 0.0053 to 0.0080 in/in for Dynamic Loading

The Calculated Equivalent Slope at a Center Joint for:• Deflection of L/800 = 0.008 in/in• Deflection of L/1000 = 0.006 in/in

Relative Slope

L

Δ

STRUCTURAL DEFORMATIONS - GIRDER ROTATION AT THE SPAN LOCKS

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Table 3 – Summary of Rotation at Center JointSunrise Blvd. Bridge Load Tests

Test Static/Dynamic Load Position Load Shoe Condition Slope18OSR1 Static Outside Lane Tight Contact all four LLS 4.718OSR2 Static Outside Lane Tight Contact all four LLS 4.718OSR3S Static Outside Lane 0.040” Shim NE LLS, 0.015” gap under SE LLS 4.518OSR4S Static Outside Lane 0.040” Shim SE LLS, 0.015” gap under NE LLS 5.018O301 Dynamic Outside Lane Tight Contact all four LLS 5.318O302 Dynamic Outside Lane Tight Contact all four LLS 6.618O303 Dynamic Outside Lane Tight Contact all four LLS 8.018O304 Dynamic Outside Lane Tight Contact all four LLS 6.118O305S Dynamic Outside Lane 0.040” Shim NE LLS, 0.015” gap under SE LLS 6.318O306S Dynamic Outside Lane 0.040” Shim SE LLS, 0.015” gap under NE LLS 6.3

STRUCTURAL DEFORMATIONS – ECCENTRIC LOADING

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Table 5 – Comparison of Guide and Receiver StrainsSunrise Blvd. Bridge Load Tests

Load Position

Forward Guide Receiver

Top Gauges Bott. Gauges Top Gauges Bott. Gauges

Back Side

Jt. SideBack Side

Jt. Side Jt. SideBack Side

Jt. SideBack Side

Outside Lane

43 187 47 188 64 44 48 44

Middle Lane

36 123 36 130 39 54 44 31

Inside Lane

28 69 28 82 19 31 26 20

RECOMMENDED CHANGES TO AASHTO LRDF MOVABLE

Recommendation No. 1: Make revisions to supplement the AASHTO Movable code to make explicit the dynamic allowance to apply in design of span locks. Expand AASHTO Movable, Article 2.4.1.2, Dynamic Load Allowance, to add the following:

“2.4.1.2.5 Span Locks

The span locks of double-leaf bascule bridges (center locks) shall be proportioned for full live load plus twice the normal live load dynamic load allowance, specified in Article 3.6.2 of the AASHTO LRFD Bridge Design Specifications.”

To further clarify the application of this provision to the fatigue limit state, add the following commentary:

“C2.4.1.2.5

Applying twice the normal live load dynamic allowance applies to use of the IM values for Strength, Service and Fatigue Limit States.”

RECOMMENDED CHANGES TO AASHTO, CONTINUED

Recommendation No. 2: Make explicit the requirements for the primary load transfer elements of span locks subject to contact stress, including guide and receiver bushings of lock bar type systems and shoes or wear plates of jaw and diaphragm or other lock systems to have a shape that relieves edge loading due to rotations and deformations of the supporting structural system. This could be accomplished by adding the following to Article 6.8.1.5.1, Locking Devices of the AASHTO Movable as follows:

“Contact surfaces for span locks shall be designed and detailed to minimize edge loading that may occur due to the deformation of the supporting structure under vehicular loading. Provide a minimum ½” radius on the leading and trailing edges of contact surfaces subject to edge loading. Providing a radius on one of the contact surfaces should be considered where other means are not available to relieve edge loading.”

RECOMMENDED CHANGES TO AASHTO, CONTINUEDRecommendation No. 3: Add commentary to address the rotations and deformations that should be considered. This could be accomplished by adding the following commentary:

“C6.8.1.5

Contact surfaces for span lock systems include wear plates or bushings in the guides and receivers of lock bar type span locks, jaw and diaphragm castings, forgings or shoes, and similar components that function to transfer the load across a joint through a contact stress. Under the influence of live load, movable spans deflect and the end(s) of the span(s) at the location of locking devices rotates. For double-leaf bascule bridges the end rotations of adjacent leaves are additive in relative effect and therefore more significant than for single-leaf bascule bridges. If the lock system is attached eccentrically to the main longitudinal members, such as on a cantilevered bracket, additional torsional deflection or rotation could take place. If these deformations are not accounted for, edge loading and eccentric loading of the lock system and supports will result in significant restraint and corresponding structural effects.

RECOMMENDED CHANGES TO AASHTO, CONTINUEDRecommendation No. 3 Continued:

Typical clearances provided between lock components (e.g. lock bar and receiver bushing) may be considered in determining the magnitude and effect of edge loading. Bushings supported on multiple springs that allow the bushing to rotate with the contacting surface, may provide relief from edge loading. A radius on the contact surfaces is an effective means of accommodating movable span deformation and alleviating undesirable restraint in the span lock system. Past experienced has shown that providing wear plates or bushings with a radius of 72 inches or smaller across the contact surface provides relief from edge loading of typical deck girder double-leaf bascule spans. A larger radius may be adequate for stiff bridges, such as those with truss members or single-leaf spans with smaller end rotations. Use of a radius results in line contact which must be considered in selecting the lock bar and wear plate materials.

Additional consideration and analysis may be warranted if a double-leaf bascule is expected to carry rail traffic as the tolerances for rail alignment may be more stringent than that required for highway or pedestrian traffic.”

Questions?or More?

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KEY FINDINGS OF PROJECT

29

Dynamic effects are significant The Shape of Wear Plates and Load Shoes affects contact stresses Secondary effects of deformations can be significant – especially on

the Forward Guides and Receivers Wear of lock components results in a general reduction in Lock

Effectiveness:• Measurable increases in differential deflection• Measurable but relatively small changes in strain

Improper Adjustment of Live Load Shoes (aka Live Load Bearings) can have a measurable effect on Span Lock and Main Girder strains

30

Hillsborough Avenue Bridge30 MPH Test, Outside Lane, 30 Block Load

WEAR EFFECTS ON LOAD TRANSFER

31

Simulated Wear Results: Measurable Decrease

in Effectiveness of the Locks

Relatively Small Decrease in Lock Bar Strain for Typical Wear (8 to 9%)

Up to 25% Decrease in Lock Bar Strain for Excessive Wear

Significant Increase in Differential Deflection

-350

-300

-250

-200

-150

-100

-50

0

50

100

150

1 38 75 112

149

186

223

260

297

334

371

408

445

482

519

556

593

630

667

704

741

778

815

852

889

926

963

1000

1037

1074

1111

1148

1185

1222

1259

1296

1333

1370

1407

1444

1481

Stra

in in

Mic

roSt

rain

/ De

flect

ion

inch

x 1

000

Time Interval

Chart GComparison of Strain & Differential Deflection For Varying Forward

Guide Clearances at North Lock Bar30 Block Load, Slow Rolling / Hillsborough Ave. Bridge

Strain No Adjust Strain 0.042 Shim Strain 0.130 Shim

Defl No Shim Defl 0.042 Shim Defl 0.140 Shim

WEAR EFFECTS ON LOAD TRANSFER

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Table 8 – Comparison of Maximum Strain Range in the Lock Bar with Shim RemovalHillsborough Ave. Load Tests

(30 Block Truck Load for All Cases)

Lock / Load Location

Clearance at Top Shoe of Forward Guide of North Lock

0.011” 0.052” 0.140”

StrainDynamic

RatioStrain

Dynamic Ratio

StrainDynamic

Ratio

North Lock / North Lane 429 1.41 383 1.37 334 1.32

South Lock / North Lane 285 2.61 274 2.54 250 2.36

North Lock / South Lane 272 3.24 328 4.90 253 3.95

South Lock / South Lane 443 1.39 458 1.40 449 1.42


33

-60.000

-50.000

-40.000

-30.000

-20.000

-10.000

0.000

10.000

20.000

30.000

40.000

1 54 107

160

213

266

319

372

425

478

531

584

637

690

743

796

849

902

955

1008

1061

1114

1167

1220

1273

1326

1379

1432

1485

1538

1591

1644

Mic

rost

rain

Time Interval

North Bar StrainVariable Shim of top of North Forward Guide

30 Block Load Applied in Inside Lane

N-1 No Adjust N-1 w/0.042" N-1 w/0.130"-250

-200

-150

-100

-50

0

50

100

150

1 47 93 139

185

231

277

323

369

415

461

507

553

599

645

691

737

783

829

875

921

967

1013

1059

1105

1151

1197

1243

1289

1335

1381

1427

1473

1519

1565

1611

1657

Mic

rost

rain

Time Interval

South Bar StrainVariable Shim of top of North Forward Guide

30 Block Load Applied in Inside lane

S-1 No Adjust S-1 w/0.042" S-1 w/0.130"

Comparison of Strains in the N&S Lock Bars For Various North Lock Receiver Shim Adjustments

Poorly Shimmed Lock resulted in a measurable (8-9%) but relatively small

reduction Strain in Lock Bar

EFFECT OF LIVE LOAD SHOE SHIMMING

34

Improper Adjustment or Wear of Live Load Shoe Simulated by Inserting a 0.040” Shim Under NE Load Shoe

Table 6 – Comparison of Maximum Range of Strain for Various Live Load Shoe Shim Adjustments

Sunrise Blvd. Bridge Tests

Load Type

Load Position

LLS Condition+(Shim) -(Gap)

Inch x 10-3

MicroStrainNorth East Girder Live Load Shoe

Lock Bar @ Center Joint

North West Girder Live Load Shoe

NE SETop of

BarBott. of

Bar

StaticOutside

Lane0 0 119 109 98 138

StaticOutside

Lane+40 -15 129 113 103 134

DynamicOutside

Lane0 0 169 137 123 183

DynamicOutside

Lane+40 -15 201 145 128 213

StaticMiddle

Lane0 0 70 65 59 87

StaticMiddle

Lane+40 -15 81 69 67 83

DynamicMiddle

Lane0 0 136 102 90 166

DynamicMiddle

Lane+40 -15 153 104 93 167

StaticInside Lane

0 0 30 25 22 38

StaticInside Lane

+40 -15 34 24 23 33

DynamicInside Lane

0 0 67 63 56 74

DynamicInside Lane

+40 -15 69 66 60 66

NE NW

SWSE

0.040” Shim

0.015” Gap

Instrumented Span Lock

Inside Lane

Outside Lane

EFFECT OF LIVE LOAD SHOE SHIMMING

35

Improper Adjustment or Wear of Live Load Shoe Simulated by Inserting a 0.040” Shim Under SE Load Shoe

Table 6 – Comparison of Maximum Range of Strain for Various Live Load Shoe Shim Adjustments

Sunrise Blvd. Bridge Tests

Load Type

Load Position

LLS Condition+(Shim) -(Gap)

Inch x 10-3

MicroStrainNorth East Girder Live Load Shoe

Lock Bar @ Center Joint

North West Girder Live Load Shoe

NE SETop of

BarBott. of

Bar

StaticOutside

Lane0 0 119 109 98 138

StaticOutside

Lane-15 +40 120 103 94 138

DynamicOutside

Lane0 0 169 137 123 183

DynamicOutside

Lane-15 +40 186 141 123 193

StaticMiddle

Lane0 0 70 65 59 87

StaticMiddle

Lane-15 +40 74 66 59 86

Dynamic Middle Lane

0 0 136 102 90 166

DynamicMiddle

Lane-15 +40 146 110 92 164

StaticInside Lane

0 0 30 25 22 38

StaticInside Lane

-15 +40 30 23 23 33

DynamicInside Lane

0 0 67 63 56 74

DynamicInside Lane

-15 +40 70 73 65 91

NE NW

SWSE0.040” Shim

0.015” Gap

Instrumented Span Lock

Poorly Shimmed Live Load Shoe resulted in a measurable (8%) but relatively small Increase

in Strain in the Main Girders

Questions?

36