Post Earthquake Bridge Safety Assessment Program

Transcription

1 Post Earthquake Bridge Safety Assessment Program WSDOT/ Structures Team-April 2017 Paul Brallier, SE-, HNTB Corporation Jeri Bernstein, SE-WSDOT 1

2 Introduction Purpose: Provide agency personnel an introduction to available training materials for rapid safety assessment of bridges after an earthquake. A self training manual is provided as a download as part of this presentation. Key points of the training manual are discussed as part of this presentation. Post Earthquake Bridge Safety Assessment Program Presentation Outline Training Program Introduction What is an Earthquake? Preparation Before an Earthquake What to do After an Earthquake Closure and Questions Jeri Jeri Paul Paul Jeri and Paul 2

3 Where to Use This Training Bridge Inspections/Assessments FHWA / NBIS Routine Maintenance Inspections Flood / Scour Inspections 3rd Party Damage Inspections Earthquake Safety Assessment Level 1 Drive By/ Fly By Collapse Identification Level 2 Rapid Visual Assessment (this presentation) By those who can be at the site quickly and have basic knowledge or familiarity of the structures (maintenance, construction inspectors, etc.) Level 3 Detailed Engineering Evaluation /WSDOT Bridge and Structures Website Link Download Materials: Training Materials Contributors Adapted from WSDOT Post-Disaster Bridge Inspection Guidelines King County Road Services Division - Structural Design and Bridge Inspection Unit 3

4 Disclaimer These training materials were prepared by volunteers working under the American Council of Engineering Companies () and the Washington State Department of Transportation (WSDOT) Bridge and Structures Office for preparation for an earthquake. These materials are provided free of charge for public use. They shall be used only by people thoroughly familiar with bridge construction. While the information presented in this training is believed to be correct, the authors, and WSDOT assume no responsibility for its accuracy or for the opinions expressed herein. The material presented in this publication should not be used or relied upon for any specific application without competent examination and verification of its accuracy, suitability, and applicability by qualified professionals. Use of information from this publication assumes all liability arising from such use. What is an Earthquake? 4

5 5

6 Terminology Peak Ground Acceleration (PGA) (% G) Alex weighs 100 pounds. 34 pounds Alex experiences an earthquake with a Peak Ground Acceleration (PGA) of 0.34 G or 34% G. The sideways force Alex would feel is.34 X 100 = 34 pounds. Nisqually Earthquake 6

7 Preparation Before an Earthquake Pre-Earthquake Planning Goal Where to Go, What to Bring 1. Essential life-line bridges and arterials are 1 st priority 2. Know your bridges and identify susceptible bridges (built before 1985) 3. Prepare a deployment plan who/where/routes/communications 4. Have a Go Box 5. Subscribe to Shakecast 7

8 Bridges Built Before 1985 Ductility and Continuity Columns constructed before 1985 Insufficient ties for ductility Bridge Seats and Seismic Restrainers Added After 1985 Bridges Built Before 1985 Ductility Columns designed before 1985 Wide tie spacing Columns Fail Widely Spaced Ties 8

9 Bridges Built After 1985 Columns designed after 1985 Ties confine the concrete core giving ductile columns Lots of closely spaced ties allow columns to bend w/o breaking Bridges Built Before 1985 Continuity No Restrainers Between Spans Photo: Dave Swanson 9

10 Seismic Retrofit Works! Pre-1985 Bridge with added restrainers Seismic Restrainers after the 2011 Japan EQ Keeps bridge from falling of bearings Unit 4 What Do I Take? Prepare a Go Box Road closure signs Caution tape, traffic cones, flares PPE s: Hard hat, vests, gloves, safety glasses Flashlight and spare batteries Spray paint and YELLOW lumber crayons Communication Equipment - phone and or radio (communication service likely to be disrupted) 100 & 25 measuring tapes, Maps, binoculars, camera Notepad for documentation of bridge assessments! Bridge Assessment forms Meals Ready to Eat (MRE s), Snacks, Water 10

11 Post Earthquake Plan Goal - Ensure the Safety of the Public 1. Timely and current assessment of damage 2. Closing bridges if necessary 3. Reporting findings as often as needed (aftershocks) 4. Protecting the bridges from additional damage (shoring) 5. Essential life-line bridges and arterials are 1 st priority 6. Restoring traffic on bridges as quickly as possible (repair) When Do I Go? Where Do I Go? Magnitude 5.5 or greater (Strong enough to wake you up in the middle of the night or strong enough to move knick-knacks on your shelves) Inspect within a 100-mile radius of the epicenter Inspect life-line and main arterial routes first, then secondary routes. Take standard protective gear and road closure supplies Close bridges as needed and plan detour routes 11

12 Field Safety Photo: Dave Swanson USGS Shakecast What is Shakecast? Software Available for download from USGS Provides the Earthquake Intensity at specific locations identified by the user by an message. Useful for agencies that have an urgent need to know an earthquake s impact on specific structures in their inventory. 12

13 Shakecast USGS Shakecast 13

14 USGS Shakecast Nisqually Earthquake 100-mile radius 14

15 Bridge Parts and Nomenclature Getting Started Parts of a Bridge 15

16 Typical Bridge Parts NEXT - 10 Steps of Assessment 1. Check Approaches 2. Check Rails 3. Check Expansion Joints 4. Check Wingwalls 5. Check Abutments 6. Check Bearings 7. Check Girders 8. Check Soffit and Deck 9. Check Bents or Columns 10. Check Bent Caps 16

17 Post Seismic Bridge Inspection Sample Pretend Bridge Safety First Approaching the Bridge You have to stop at the bridge anyway so inspect the bridge BEFORE you drive across. In fact, stop at least 30 before the bridge in case there is an approach slab with a problem. 17

18 10 Steps for Assessment X Approach Slab Settlement 1 to 6 Settlement > 6 Settlement 18

19 2. & 3. Taking the First Look at the Bridge Sight down the rail lines Straight Hmm looks straight Photo from King County 2. & 3. Railing and Curb Bending but no separation or spalling 19

20 4. Wingwall Damage Minor Damage: Shear Cracking Moderate Damage: Rotation and Separation 5. Abutment Damages Cracks, but No Separation Large cracks spalling, but still supporting and no separation 20

21 5. Abutment Damages (cont d) Pile Foundation Rotation more than 6 Bridge Assessment Forms Sample from California Office of Emergency Services Safety Assessment Program (SAP) 21

22 STATE OF CALIFORNIA SAFETY ASSESSMENT PROGRAM BRIDGE Assessment Report No. Assessment Report # 22

23 Assessment Report # 6. Bearings Bearings at Hinge Seats Significant Hinge Seat Edge Spalling / Hinge Still Sound 23

24 6. Bearings (cont d) Steel Rocker Bearings Tilted Rocker Bearing 6. Bearings (cont d) Steel Pin Bearing and Others Substantial Girder End Spalling above Bearing 24

25 7. Girders Concrete Girder Full Depth Web Cracks 7. Girders (cont d) Straight Steel Girder Buckled or Fractured Horizontal Crossframe 25

26 9. Bent or Column (cont d) Shear Cracks & Cover Spall 9. Bent or Column (cont d) Buckled Primary Reinf. Crumbled Core Moderate to Severe Damage: Spalled Column; Buckling of Primary Reinforcement (MCEER) Failed Confinement Reinf. Severe Damage: Mid-height Flexural Damage (PEQIT) Severe Damage: Confinement Failure (MCEER) 26

27 10. Bent Cap Catcher Block Minor Spalling of Concrete Summary Have equipment, tools and safety items available. Know your lifelines & high volume/high priority bridges. Know your EQ Inspect if >5.5 Magnitude & within 100 miles radius Conduct inspections in your area ASAP after seismic event inspect all 10 bridge components. Document findings on paper forms and report bridges inspected and damage found. Close damaged and failed bridges to protect the public report closures. Practice personal and public safety. 27

28 Thank You Questions? Post Earthquake Bridge Safety Assessment: Shakecast: WSDOT/ Structures Team-April 2017 Paul Brallier, SE-, HNTB Corporation Jeri Bernstein, SE-WSDOT 28