AASHTO AS Presented to AASHTO T 8, June 13, 2017

Transcription

1 AASHTO AS Support for the HSCOBS Technical Committee on Moveable Bridges (T-8) in a Technical Advisory Role for Specification Updates Span Lock Design Study Presented to AASHTO T 8, June 13, 2017 By James M. Phillips III, PE Hardesty & Hanover, Tampa, FL 1

2 Double Leaf Bascule Bridge Span Locks 2

3 STUDY TEAM Hardesty & Hanover, LLC Jim Phillips, PE Research Lead Rafal Wuttrich, PE Lead Finite Element Modeling Steve Mikucki, PE Peer Review AECOM (formerly URS and E.C. Driver & Associates, Inc.) Jim Englert, PE Project Manager Michael Reponen, PE Finite Element Modeling FDOT Will Potter, PE Structures Research Field Instrumentation and Testing District One & District Four Staff Support and Bridge Access

4 AGENDA Review of Study Purpose & Limitations Recommended Revisions to the AASHTO LRFD Movable Highway Bridge Design Specifications: Dynamic Load Allowance for Span Lock Design Edge Loading / Contact Stresses in Span Lock Design Other Observations

5 PURPOSE OF STUDY Understand Why Span Locks are Such a Maintenance Problem 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 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) 5

6 SCOPE LIMITATIONS Double Leaf Trunnion Bascule Bridges Lock Bar Type Span Locks

7 DYNAMIC LOAD ALLOWANCE Primary Objective: Determine appropriate Dynamic Load Allowance for use in design and evaluation of span locks Methodology: Measure strains for slow rolling load (static equivalent) Measure strains for same load at 30 mph (dynamic load) Utilize maximum range of strain rather than independent positive or negative values Calculate dynamic effect as ratio of dynamic to static range of strain Calculated Dynamic Ratio =,, 7

8 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Span Lock Bar Bridge Section Main Girder Elevation 8

9 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Rear Guide Forward Guide Receiver Bridge Section Main Girder Elevation 9

10 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Gauge Locations Top & Bottom of Bar between Rear Guide and Forward Guide Sides of Bar above and below neutral axis Each Face of Forward Guide and Receiver Strain Gauge Locations (14 Each Span Lock) 10

11 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Test Vehicle with 18 Block Loading Axle P1 P2 P3 P4 P5 Load (P)(kips) Test Vehicle with 30 Block Loading Axle P1 P2 P3 P4 P5 Load (P)(kips) HL-93 Vehicle Axle P1 P2 P3 P4 P5 Load (P)(kips) FDOT Test Vehicle 11

12 HILLSBOROUGH AVE. LOAD TEST Sunrise Blvd. Bridge, 30 MPH Test Inside, 30 Block Load 12

13 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Comparison of Strains in the Adjacent Lock Bar Peak Strain Static vs Dynamic Comparison at Top of Lock Bar Gauge Location N-1 Peak N-1 Range N-2 Peak N-2 Range Peak Static Strain (T/C) Peak Dynamic Strain Ratio Dynamic/S tatic 143/75 170/ / / / / Test 2 (Slow Roll) vs Test 5 (30 MPH) North Lock Bar Strain 18 Block Load, Outside Max. Measured Stress Range = 8.4 ksi (not measured at the location of max. stress N 1 is Located on Top of Lock Bar N 2 is Located on Bottom of Lock Bar N-1 T5 N-2 T5 N-1 T2 N-2 T2 13

14 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Comparison of Strains in the Opposite Lock Bar Test 2 (Slow Roll) vs Test 5 (30 MPH) South Lock Bar Strain 18 Block Load, Outside S 1 is Located on Lock Bar Above NA S 2 is Located on Lock Bar Below NA Peak Strain Static vs Dynamic Comparison, Receiver Housing Gauge Location Peak Static Strain (T/C) Peak Dynamic Strain Ratio Dynamic/ Static S-1 Peak 50/25 129/ /2.52 S-1 Range S-2 Peak 26/57 68/ /2.28 S-2 Range MicroStrain Max. Stress Range = 5.7 ksi 100 Higher Dynamic Ratio, but lower overall strain 150 Time Interval S 1 T5 S 1 T2 S 2 T2 S 2 T5 14

15 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Comparison of Strains in the Forward Guide Housing, Static vs Dynamic Peak Strain Static vs Dynamic Comparison, Receiver Housing Gauge Location Peak Static Strain (T/C) Peak Dynamic Strain Ratio Dynamic/ Static N-C Peak 7/38 7/ /1.55 N-C Range Guide Strain Comparison Test 2 (Slow Roll) vs Test 5 (30 MPH) North Lock Bar 18 Block Load in Outside N-D Peak 4/18 3/ /1.72 N-D Range N C and N D are Located on Joint Side of Forward Guide N C T5 N D T5 N C T2 N D T2 15

16 SUNRISE BLVD. FIELD INSTRUMENTATION AND LOAD TESTING Strain Gauges: Outside Girder Span Lock; Outside Main Girders Tip Rotation via Displacement Transducers Variable Shimming of Live Load Shoe Displacement Transducers Live Load Bearing Shimming Main Girder Strain Gauges (Typ.) 16

17 Hillsborough Ave. Bridge 30 MPH Test Outside 17

18 SUNRISE BLVD. BRIDGE CONSISTENCY OF FIELD TESTS Chart E 30mph Runs in Outside Comparison of Strain in Lock Bar for 4 Tests Sunrise Blvd. Bridge Load Tests Average Standard Deviation = 5.3 Coefficient of Variation = 2.1% to 8.4% Microstrain Time Interval 18O301 S9 18O302 S9 18O303 S9 18O304 S9

19 SUMMARY OF DYNAMIC RATIOS Dynamic Ratio = Bridge Table 7 (Modified) Comparison of Guide and Receiver Dynamic Ratios FDOT Test Truck with 18 Block Load Lock Bar Load in Adjacent Forward Guide Receiver Lock Bar Load in Far Forward Guide Receiver Hillsborough Ave Sunrise Blvd Corresponding Maximum Strains Hillsborough Ave Sunrise Blvd For Scale Reference: 333 Microstrain 9.6 ksi 19

20 RECOMMENDED CHANGES TO AASHTO LRDF MOVABLE Expand AASHTO Movable, Article , Dynamic Load Allowance, to add the following: 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 of the AASHTO LRFD Bridge Design Specifications. To further clarify the application of this provision to the fatigue limit state, add the following commentary: C The use of twice the normal live load dynamic allowance for span locks applies to Strength, Service and Fatigue Limit States.

21 SPAN LOCK CONTACT STRESSES Primary Objective: Quantify the effects of bascule span deflection and end rotation on span lock component contact stresses Identify span lock component geometries that reduce contact stress, thereby improve durability Methodology: Assess structural deformations that influence contact stresses Use Finite Element Model (LUSAS) to evaluate contact stresses in load shoes (aka wear plates) and lock bars Model Hillsborough Avenue bridge and span lock system Validate model by comparing predicted with measured field strains Model various load shoe shapes and evaluate performance 21

22 STRUCTURAL DEFORMATIONS GIRDER ROTATION AT THE SPAN LOCKS Sunrise Bridge Tests Included Measurement of End Rotations (Relative Slope Between Leaves) For the Test Load in the Adjacent to the Instrumented Lock/Girder Relative End Rotation Measured in/in for Static Loading and to in/in for Dynamic Loading The Calculated Equivalent Slope at a Center Joint for: Deflection of L/800 = in/in Deflection of L/1000 = in/in L Δ Relative Slope 22

23 STRUCTURAL DEFORMATIONS GIRDER ROTATION AT THE SPAN LOCKS Summary of Rotation at Center Joint (1000 th inch/inch) Sunrise Blvd. Bridge Load Tests Test Static/Dynamic Load Position Load Shoe Condition Slope 18OSR1 Static Outside Tight Contact all four LLS OSR2 Static Outside Tight Contact all four LLS OSR3S Static Outside Shim NE LLS, gap under SE LLS OSR4S Static Outside Shim SE LLS, gap under NE LLS O301 Dynamic Outside Tight Contact all four LLS O302 Dynamic Outside Tight Contact all four LLS O303 Dynamic Outside Tight Contact all four LLS O304 Dynamic Outside Tight Contact all four LLS O305S Dynamic Outside Shim NE LLS, gap under SE LLS O306S Dynamic Outside Shim SE LLS, gap under NE LLS

24 STRUCTURAL DEFORMATIONS ECCENTRIC LOADING Table 5 Comparison of Guide and Receiver Strains (Microstrain) Sunrise Blvd. Bridge Load Tests Forward Guide Receiver Load Position Outside Middle Inside Top Gauges Bott. Gauges Top Gauges Bott. Gauges Back Side Jt. Side Back Side Jt. Side Jt. Side Back Side Jt. Side Back Side Measured Strain Variations Confirm Eccentric Loading Effects 24

25 LOAD SHOE / WEAR PLATE SHAPE Contact Stresses at the Lock Bar interface with the Wear Plates or Load Shoes are influenced by the Geometry and System Deformations Load Shoe Contact Stress System Deformations Modeled with in/in relative rotation Lock Bar Contact Stress 25

26 LOAD SHOE / WEAR PLATE SHAPE Flat shape with radius on leading edge: 13.5 ksi contact stress Eccentric contact on edge of shoe ½ R 26

27 LOAD SHOE / WEAR PLATE SHAPE Round shape w/ large radius (72 ): 16 ksi contact stress Minimal eccentric loading 72 R 72 Radius Effective In Reducing Edge Loading 27

28 LOAD SHOE / WEAR PLATE SHAPE Compound shape, Flat Center, Radius front and back: 24 ksi contact stress Limited eccentric loading Potential for additional optimization 18 R 28

29 RECOMMENDED CHANGES TO AASHTO LRFD MOVABLE Add the following to Article , Locking Devices of the AASHTO Movable: 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 or more of the contact surfaces should be considered where other means are not available to relieve edge loading.

30 RECOMMENDED CHANGES TO AASHTO, CONTINUED Add commentary for Article Locking Devices: 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.

31 RECOMMENDED CHANGES TO AASHTO, CONTINUED Add commentary for Article Locking Devices: 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. 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.

32 RECOMMENDED CHANGES TO AASHTO, CONTINUED A radius on the contact surfaces (i.e. a cylindrical surface similar to a typical rocker bearing) 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.

33 RECOMMENDED CHANGES TO AASHTO, CONTINUED 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. Lock / Load Location Comparison of Center Joint Deflections (inches) Hillsborough Ave. Bridge Load Tests 18 Block Truck 30 Block Truck Static Load Dynamic Load Ratio Static Load Dynamic Load Ratio North Lock / Adjacent South Lock / Adjacent North Lock / Far South Lock / Far

34 OTHER KEY FINDINGS OF PROJECT Wear of lock components (load shoes or wear plates) results in a general reduction in span lock effectiveness & performance Measurable increases in differential deflection Measurable but relatively small changes in strain 34

35 WEAR EFFECTS ON LOAD TRANSFER AND LOCK PERFORMANCE Simulated Wear Results on Hillsborough Ave Bridge: 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 Strain in MicroStrain / Deflection inch x Chart G Comparison of Strain & Differential Deflection For Varying Forward Guide Clearances at North Lock Bar 30 Block Load, Slow Rolling / Hillsborough Ave. Bridge Time Interval Strain No Adjust Strain Shim Strain Shim Defl No Shim Defl Shim Defl Shim 35

36 WEAR EFFECTS ON LOAD TRANSFER Lock / Load Location Comparison of Maximum Strain Range in the Lock Bar with Shim Removal Hillsborough Ave. Load Tests (30 Block Truck Load for All Cases) Strain Clearance at Top Shoe of Forward Guide of North Lock Dynamic Ratio Strain Dynamic Ratio Strain Dynamic Ratio North Lock / North South Lock / North Poorly Shimmed Lock resulted in a measurable (8-9%) but relatively small reduction Strain in Lock Bar 36

37 OTHER KEY FINDINGS OF PROJECT Improper Adjustment of Live Load Shoes (aka Live Load Bearings) can have a measurable effect on span lock and main girder strains but relatively small Increase in strain in main girders and span lock components 37

38 EFFECT OF LIVE LOAD SHOE SHIMMING Improper Adjustment or Wear of Live Load Shoe Simulated by Inserting a Shim Under NE Load Shoe NE SE Shim Gap Outside Instrumented Span Lock Inside NW Poorly Shimmed Live Load Shoe resulted in a measurable (6%) but relatively small Increase in Strain in the Lock Bar SW Table 6 Comparison of Maximum Range of Strain for Various Live Load Shoe Shim Adjustments Sunrise Blvd. Bridge Tests Load Type Static Static Dynamic Dynamic Static Static Dynamic Dynamic Static Static Dynamic Dynamic Load Position Outside Outside Outside Outside Middle Middle Middle Middle Inside Inside Inside Inside LLS Condition +(Shim) (Gap) Inch x 10 3 NE SE North East Girder Live Load Shoe MicroStrain Lock Center Joint Top of Bar Bott. of Bar North West Girder Live Load Shoe

39 EFFECT OF LIVE LOAD SHOE SHIMMING Improper Adjustment or Wear of Live Load Shoe Simulated by Inserting a Shim Under SE Load Shoe NE SE Gap Shim Instrumented Span Lock NW Poorly Shimmed Live Load Shoe resulted in a measurable (8%) but relatively small Increase in Strain in the Main Girders SW Table 6 Comparison of Maximum Range of Strain for Various Live Load Shoe Shim Adjustments Sunrise Blvd. Bridge Tests Load Type Static Static Dynamic Dynamic Static Static Dynamic Dynamic Static Static Dynamic Dynamic Load Position Outside Outside Outside Outside Middle Middle Middle Middle Inside Inside Inside Inside LLS Condition +(Shim) (Gap) Inch x 10 3 NE SE North East Girder Live Load Shoe MicroStrain Lock Center Joint Top of Bar Bott. of Bar North West Girder Live Load Shoe

40 Questions? 40

41 DYNAMIC EFFECTS AASHTO Dynamic Load Allowance, IM AASHTO Table , Dynamic Load Allowance, IM Components IM Deck Joints All Limit States 75% All Other Components Fatigue and Fracture Limit State 15% All Other Limit States 33% Article , 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 of the AASHTO LRFD Bridge Design Specifications. Article , 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.

42 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Comparison of Strains in the N&S Lock Bars For Various North Lock Receiver Shim Adjustments South Bar Strain Variable Shim of top of North Forward Guide 30 Block Load Applied in Inside lane North Bar Strain Variable Shim of top of North Forward Guide 30 Block Load Applied in Inside Microstrain Microstrain Time Interval Time Interval S 1 No Adjust S 1 w/0.042" S 1 w/0.130" N 1 No Adjust N 1 w/0.042" N 1 w/0.130" 42

43 HILLSBOROUGH AVE. BRIDGE SPAN LOCK INSTRUMENTATION & TESTING Comparison of Strains in the Receiver Housing, Static vs Dynamic Peak Strain Static vs Dynamic Comparison, Receiver Housing Gauge Location Peak Static Strain (T/C) Peak Dynamic Strain Ratio Dynamic/St atic N-E Peak 4/23 7/ /1.52 N-E Range Receiver Strain Comparison Test 2 (Slow Roll) vs Test 5 (30 MPH) North Lock Bar 18 Block Load in Outside N E is Located on Joint Side of Receiver N H is Located on Back Side of Receiver N E T5 N H T2 N E T2 N H T5 N-H Peak 7/7 7/8 1.00/1.15 N-H Range Greater Dynamic Effect on Side Facing Center Joint 43