nchrp 12-112 update of the aashto national movable ......national cooperative highway research...

NCHRP 12-112 - AASHTO T8 Committee Meeting - June 2019

NCHRP 12-112 Update of the AASHTO

Movable Highway Bridge Design

Specifications

June 24, 2019| Montgomery , AL

AASHTO T8 Committee Meeting

NCHRPNATIONAL

COOPERATIVE

HIGHWAY

RESEARCH

PROGRAM

Jeff Newman


Disclaimer

2

Phase I Research DiscussionScheduleWork PlanObjectives


Presentation Outline

Project Objectives

Phase I Work - Completed

Phase II Work - Ongoing

Updated Schedule

Discussion/Questions

3



4

Firm POC Email

Modjeski and Masters, Inc. Jeffrey NewmanKevin JohnsThomas MurphyZolan PruczLance Borden

[email protected]

Hardesty & Hanover, LLC Jim PhillipsAlec NoblePaul Skelton

[email protected]

Auburn University Andrzej Nowak(Andy)

[email protected]

Independent Consultant Ian Buckle [email protected]

4

Research Team Introduction



Develop and incorporate consistent reliability-based methodology into AASHTO Movable Highway Bridge Design Specifications (MHBDS)

Update MHBDS with special focus on Electrical, Hydraulic, and Mechanical sections.

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Project Objectives



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Phase I Planning - Completed


Task

1 - Review Literature

2 – Discussion of Reliability-Based Methodology

3 – Proposed Methodology

4 – Outline Proposed Specification Modifications

5 – Interim Report No. 1


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Phase II Methodology Development - Ongoing


Task Progress

6 – Development of the Approved Methodology 90%

7 – Develop Examples 20%

8 – Sample Section 0% (Anticipated to be Section 5 for Loads)

9 – Interim Report No. 2 0%


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Phase III Specification Revision and Update


Task Status

10a – Complete Specification Development Pending Phase II Completion/Approval

10b – Fully Develop (Update) Examples Pending Phase II Completion/Approval

11 – Interim Report No. 3 Pending Phase II Completion/Approval

Phase IV Final Products

Task Status

12 – Revisions Based on Panel Input Pending Phase III Completion/Approval

13 – Final Deliverables Pending Phase III Completion/Approval


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Phase I - Results

Summary of Phase I Research Findings

1. Meaningful Sample of Movables

8 Owners from diverse locations

267 movable bridges

44% Bascule

20% Vertical Lift

31% Swing

5% Retractable

92

22

2

52

83

15

Movable Bridge Type

Trunnion Bascule Rolling Lift Bascule Other Bascule

Vertical Lift Swing Retractable


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Phase I - Results


2. Frequency of Operation

Min = 12 / yr

Max = 14,600 / yr

Average Min = 1,107 / yr (2.8 per day)

Average Max = 6,903 / yr (18.9 per day)


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Phase I - Results


3. Waterway Categories & Wind Restrictions

21

129

105

12

PORT OF ENTRY COMMERCIAL MIXED USE RECREATIONAL

Waterway Categories

Average 39 mph

40

50

3530

40 4035

40

0

10

20

30

40

50

60

1 2 3 4 5 6 7 8

Operating Wind Restrictions (mph)

Sustained Wind Limit (mph) Wind Gust Limit (mph)


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Phase I - Results


4. Reliability of Systems / Components

RATING SCALE:

5 = Excellent

4 = Good

3 = Satisfactory

2 = Fair

1 = Poor0

1

2

3

4

5

SupportMachinery

DriveMachinery

Locking / LiveLoad Transfer

Electrical Power/ Control

Traffic Control(gates / signals)

RoutineMaintenance

(over life)

Rel

iab

ility

Rat

ing

System / Component

Reliability - Routine Maintenance


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Phase I - Results


5. Conclusions

Owner Surveys were very valuable:

Consistent Responses with widely varying Owners

Owners satisfied with existing code outcomes => calibrate to existing AASHTO Movable

Other than Dutch Code, design information is limited in applicability to movable bridges

We will utilize some of the Dutch code ideas such as targeted wind loading

Reliability indices correlate to Eurocode. We will calibrate to existing AASHTO code.

Reliability-Based Methods are best applied to Loads that are Resisted by Mechanical and Structural components

Electrical and Hydraulic design are subjected to NEC and NFPA, respectively


Sections 1 -4: General Updates

Section 5: Modify (Mechanical Design Loads and Power Requirements)

Add: Bridge Availability (Operational Requirements)

Add: Wind Loading During Operation

Add: Design Loads for Mechanical Subsystems and Components (Relocated from 6.5 & 7.4.1 and Updated)

Section 6: Update Resistance Factors

Section 7: Update Resistance Factors

Section 8: General Updates

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Outline of Proposed Specification Modifications


Appx B: New “System Reliability”Objectives and Limitations

Failure Mode Analysis

• Acronyms and Definitions

• Methodology

Subsystem Development

• Reliability Block Diagram

• Mech / Elec (power) / Control / Hydraulic / Locking / Span Support / Traffic Control

Identifying Critical Failure Items

• Risk Assessment

Redundant Design

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Outline of Proposed Specification Modifications


Survey 1: Bridge OwnersBridge Importance / Availability

Bridge Maintenance / Subsystem Malfunction

Component Reliability

Manufacturers / SuppliersStandard Product Reliability (limited data available such as L10)

Fabricated Product Reliability (no standardized data available)

Opportunities for future research (beyond this project)On-going input from:

• Bridge Owners / Manufacturers / Designers

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Knowledge Gaps

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Ph II Development DiscussionScheduleWork PlanObjectives

Execution of Methodology| Task 6

Movable Bridge Limit States

Mechanical, Hydraulic, Electrical Design Limit States

Service

Fatigue

Overload

Extreme Event

Structural Limit StatesStrength

Service (not in current AASHTO)

Fatigue (not in current AASHTO)

Overload (not in current AASHTO)

Extreme Event


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Service Limit StateDefinition: A state in which the function of the machinery, its performance,

durability, maintainability, and safety are preserved under normal use.

Objectives: Avoid elastic deformations in machinery components that may impair serviceability or produce localized stresses under normal operating loads that reduce the anticipated service life of components (i.e. premature or accelerated wear).

Load Cases:• Case 1a: 150% FLT of the motor (AASHTO Movable Ref: 5.7.1)

• Case 1b: Pump Pressure at Normal Pressure (relief valve setting) (AASHTO Movable Ref: 7.4.2)

• Case 1c: 1.0 FLT for Internal Combustion Engine (AASHTO Movable Ref: 5.7.1)

• Case 2: Motor or Machinery Brake Torque (AASHTO Movable Ref: 5.7.3) (Option 1)

Values in red are

from current

code and subject

to change

pending further

analysis


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Fatigue Limit StateDefinition: A state in which crack development and growth in

machinery, due to repetitive loading, is prevented under normal use.

Objectives: Avoid development and growth of fatigue cracks in structural and mechanical components subject to tensile stress from repetitive loading due to bridge operation or truck loading.

Load Cases:• Case 2a: 100% FLT of the motor (AASHTO Movable Ref: 5.7.1)

• Case 2b: Pump Pressure at Normal Pressure (relief valve setting) (AASHTO Movable Ref: 7.4.2)

• Case 2c: Loading caused by movement of the movable span

Values in red are

from current

code and subject

to change

pending further

analysis


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Values in red are

from current

code and subject

to change

pending further

analysis

Overload Limit StateDefinition: A state in which the functionality of the operating machinery,

its ability to resist or transmit loads, is preserved under maximum operating or resisting loads.

Objectives: Avoid localized yielding that may permanently deform machinery components while allowing higher stresses for load cases of limited frequency.

Load Cases:• Case 3a: 1.5 ST or 1.5 BDT for uncontrolled AC motors (AASHTO Movable Ref: 5.7.1)

• Case 3b: 1.0 ST or 1.5 AT for controlled AC motors (AASHTO Movable Ref: 5.7.1)

• Case 3c: 3.0 FLT for controlled DC motors (AASHTO Movable Ref: 5.7.1)

• Case 3d: Hydraulic Pressure at Maximum Working Pressure (overriding pressure relief valve setting)

• Case 3e: 1.0 PT at Full Throttle for Internal Combustion Engine (AASHTO Movable Ref: 5.7.1)

• Case 4: Combined Motor or Machinery Brake Torque (Option 2)


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Execution of Methodology| Task 6Extreme Event Limit State

Definition: A state in which the capacity of the machinery to perform its functions related to maintaining stability of the movable span is preserved during an extreme event such as an earthquake or vessel allision.

Objectives: Avoid failure of machinery that participates in supporting or stabilizing the movable span during extreme events. Permanent plastic deformation that renders the machinery inoperable is acceptable provided the resulting displacements do not compromise the survivability of the movable span.

Load Cases:• Case 5a: Serviceability Earthquake bridge closed / Case 5b: Serviceability Earthquake bridge open

• Case 5c: Survivability Earthquake bridge closed / Case 5d: Survivability Earthquake bridge open

• Case 5e: Vessel Impact bridge closed / Case 5f: Vessel Impact bridge open


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Wind Loads

Maintain existing code correlation to operation up to Tropical Storm Force Winds (39mph / 10 psf)

Harmonize basis with AASHTO LRFD & ASCE 7-10 (3 second wind gust)

Correlate equivalent wind loadings for holding, structural design and temporary conditions (operating and holding)


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Wind Loads

Provide alternative method for bridges with outlying conditions

Traffic Importance

Waterway Importance

Limit minimum to 7.5 psf and recommend maximum of 12.5 psf

Provides basis for states like Michigan to use 50mph operating condition

Provides basis to adjust for critical bridge locations, e.g. port entrance / evacuation traffic

Provides options to lower cost of less critical bridges, e.g. seldom operated / low traffic bridges


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Task Submission Review completed Phase

5 – Interim Report No. 1 - Preliminary April 29, 2018 May 2018 I

5 – Interim Report No. 1 - Final August 31, 2018 September 2018 I

6 – Develop and Execute Methodology November 30, 2019 February 2020 II

7 – Develop Illustrative Examples December 31, 2019 February 2020 II

8 – Complete Sample Section of the Guide December 31, 2019 February 2020 II

9 – Interim Report No. 2 December 31, 2019 February 2020 II

10 & 11 – Complete Revised Specs & Examples / IR 3 August 31, 2020 September, 2020 III

12 & 13a – Revisions and Draft Final Report December 31, 2020 February, 2021 IV

13b – Final Report and End of project March 31, 2021 IV

Research Schedule


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- Open Discussion -

NCHRP 12-112 Update of the AASHTO LRFD

Movable Highway Bridge Design Specifications


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Proposed New Target Reliability IndicesβT ~ 1.0: Service LS

• Correlates to Pf = 0.15 = 15%

βT ~ 2.75: Overload LS• Correlates to Pf = 0.0049 = 0.49%

βT ~ 3.75: Extreme Event LS• Correlates to Pf = 0.0001 = 0.01%


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Service Limit Stateβ = 1.09: Reliability Index – Current MHBS

• Value as calculated by Auburn Team

βT ~ 1.0: Target Reliability Index – Proposed New• Correlates to Pf = 0.15 = 15%

β = 1.23 : Calculation Results with:• Recommended Load Factor: 𝛾 = 2.5

• Recommended Resistance Factor: 𝜙 = 0.8


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Develop Illustrative Examples| Task 7

Service Limit State – Sample ProblemTorsion in a shaft

• Required Diameter = 1.402” Existing MHBS

• Required Diameter = 1.420” Proposed New LRFD Method

• Proposed New LRFD Method slightly more conservative by 1.3% for this example.

More samples will be run to verify consistency of results.

nchrp 12-112 update of the aashto national movable ......national cooperative highway research...

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