Post-EQK Damage Assessment of Bridges Marc J. Veletzos, Ph.D., P.E. - - PowerPoint PPT Presentation

Post-EQK Damage Assessment of Bridges

Marc J. Veletzos, Ph.D., P.E. Merrimack College

Post-Earthquake Reconnaissance Workshop 2015 EERI Annual Meeting April 3, 2015

Some Questions for You

 Who is…

 An Undergraduate Student?  A Graduate Student?

 Who has taken…

 EQK Engineering Class?  Bridge Design Class?  Concrete Design Class?  Steel Design Class?

 Who is from…

 West coast?  East coast?  Middle states?

Outline

 Current State of Practice  Reinforced Concrete Bridge Behavior  Inspection and Assessment Protocol of RC Bridge

Columns

 Questions

Current State of Practice

A Broad Perspective

ATC-20 (Buildings)

 Three placard postings:

 No apparent hazard  Hazardous condition exists  Extreme hazard present

Source: ATC, 2005

Assessment Procedures (Bridges)

 Indiana DOT

and

 Kentucky DOT



Pre-investigation, , and procedures

 Mississippi DOT

, , and

 New York DOT



Aerial reconnaissance, , , and

 Oregon DOT (multi-hazard)



First look, , , and

 Utah DOT



Initial reports, , , and

 Washington DOT



Level I investigation, , , and

ATC-20 equivalent

Washington DOT Emergency Response Inspection Procedure

Source: Reed and Wang, 1993.

Event Level I Not Collapsed Collapsed Level III Unsafe (red) Limited Entry (yellow) Safe (green) Unsafe (red) Unsafe (orange) Limited Entry (yellow) Safe (green) Repair/ Rebuild End : Inspection rating : Inspection procedure Legend: (Detailed Evaluation) Level II Forensic Investigation (Rapid Evaluation) (Engineering Evaluation)

NY DOT Damage Assessment Types - Aerial Reconnaissance

NY DOT Damage Assessment Types

NY DOT Damage Assessment Types - Preliminary Bridge Damage Assessment

NY DOT Damage Assessment Types - Special Post-EQK Bridge Inspection

NY DOT Damage Assessment Types - Further Investigation

NY DOT Process Flowchart (Mobilization of Assets)

EVENT RE receives text message and/or email notification from USGS* Affected residency conducts Preliminary Bridge Damage Assessment (PBDA) starting with state bridges on priority routes and reports findings to RSE. Response Level I: As directed by RSE. Mw ≥ 3.5? Reports of damage? Damage found? Uncertain? RSE arranges for inspection of any critically important bridges within radius of concern (R). Response Level II: 3.5 ≤ Mw < 4.5 R = 40 miles Response Level III: 4.5 ≤ Mw < 5.5 R = 60 miles Response Level IV: Mw ≥ 5.5 R = 80 miles Inspect damage bridges found in PBDA and seismically vulnerable bridges in 40 miles radius. Inspect bridges with VR = 1 or VR =2 Inspect damage bridges found in PBDA and seismically vulnerable bridges in 60 miles radius. Inspect bridges with VR = 1 or VR =2 Conduct Aerial Reconnaissance Inspect all bridges in 80 mile radius, starting with damaged and seismically vulnerable bridges Flag bridges per DOT policy. Call for further investigation if necessary STOP

No No Yes Yes * In RL1, RSE receives notification

Sources: O’Connor, 2010.

If you have a Mw=4, do you inspect every bridge in your state?

Reinforced Concrete Bridge Behavior

A more detailed perspective

Possible Location of Plastic Hinges in Bridge

You need to know where to look for damage!

Longitudinal Bar Buckling of Pre '71 Design

Pull Out Failure of Pre '71 Design

Flexural Damage at Base of Column.

Note spalling

• f concrete

Flexural Failure of Post '94 Design

Shear Failure of Pre '71 Design

Shear Failure in Hinge Region

Column Lap Splice Failure

Shear Failure Below Flare

Flexural Failure of Flared Column

(Note: Research columns are tested upside down for convenience)

Connection/Joint Shear Failure

Abutment Shear Key Failure

Bearing Failure due to Sliding

Inspection and Assessment Protocol

• f RC Bridge Columns

An approach proposed to Caltrans

PHASE I – DETERMINE PERFORMANCE CURVE

Lateral Force

D - Response SD - Response B - Response

X X X Lateral Displacement Lateral Force

D - Response SD - Response B - Response

X X X Lateral Displacement

How is your column likely to respond?

Column Failure Mode and Performance Curve Decision Making Flowchart

“BRITTLE” Shear dominated failure “STRENGTH DEGRADING” Flexural failure

• r

End End

• 1. Column Retrofits
• 2. Aspect Ratio
• 3. Column

Reinforcement Splices

Yes No “BRITTLE” Shear Dominated Failure F-F column jacket retrofit Yes No “DUCTILE” flexure failure P-F column jacket retrofit Yes “STRENGTH DEGRADING” flexural failure but the column will retain vertical load capacity  collapse possible Start Check for Column Retrofits L/D < 2 Yes “BRITTLE” Shear Dominated Failure Check Aspect Ratio column jacket retrofit Yes No No

• 3a. Check

TRANSVERSE Reinforcement for Lap Splices Are hoops

• r spirals

continuous No P column jacket retrofit Yes Check “2. Aspect Ratio” and “3. Transverse Reinforcement”. This column may be moved to “BRITTLE” but will be no better than “STRENGTH DEGRADING”. End End End End “BRITTLE” Shear dominated failure “STRENGTH DEGRADING” Flexural failure

• r

End End End End End End

• 1. Column Retrofits
• 2. Aspect Ratio
• 3. Column

Reinforcement Splices

Yes No “BRITTLE” Shear Dominated Failure F-F column jacket retrofit Yes No “DUCTILE” flexure failure P-F column jacket retrofit Yes “STRENGTH DEGRADING” flexural failure but the column will retain vertical load capacity  collapse possible Start Check for Column Retrofits L/D < 2 Yes “BRITTLE” Shear Dominated Failure Check Aspect Ratio column jacket retrofit Yes No No

• 3a. Check

TRANSVERSE Reinforcement for Lap Splices Are hoops

• r spirals

continuous No P column jacket retrofit Yes Check “2. Aspect Ratio” and “3. Transverse Reinforcement”. This column may be moved to “BRITTLE” but will be no better than “STRENGTH DEGRADING”. End End End End End End End End End End End End

Column Failure Mode and Performance Curve Decision Making Flowchart

End

• 4. Column Transverse

Reinforcement

Any longitudinal splices in column Yes No Column trans rebar spacing > 8” “STRENGTH DEGRADING” Flexure

• failure. Regardless of column

reinforcement, under extreme cycles the splice may slip and act more like a strength degrading column. The column may retain vertical load capacity.  collapse is unlikely “BRITTLE” Shear failure. The column may not retain vertical load capacity  collapse possible Yes No Make note of inadequate development of column

• long. rebar. Use this

information to assess the bridge system l < ld

• 4a. Check Column

TRANSVERSE Reinforcement Spacing

• 3b. Check

LONGITUDINAL Reinforcement for Lap Splices Check Development of Column Longitudinal Reinforcement Yes No s <= min(6db, 8”)  “DUCTILE” Flexural failure

• 4b. Check Confinement
• f Plastic Hinge Regions

(adjacent to fixed connections at footing and/or bent cap) s >= min(6db, 8”) “STRENGTH DEGRADING” Flexural failure #4 @ 12” (typ. of pre ‘72)

• r spacing

> 12” Yes No “BRITTLE” Shear Dominated Failure Yes No

• 5. Comments

End End End End End Splicing not an issue. Check Column Transverse Reinforcement End End End

• 4. Column Transverse

Reinforcement

Any longitudinal splices in column Yes No Column trans rebar spacing > 8” “STRENGTH DEGRADING” Flexure

• failure. Regardless of column

reinforcement, under extreme cycles the splice may slip and act more like a strength degrading column. The column may retain vertical load capacity.  collapse is unlikely “BRITTLE” Shear failure. The column may not retain vertical load capacity  collapse possible Yes No Make note of inadequate development of column

• long. rebar. Use this

information to assess the bridge system l < ld

• 4a. Check Column

TRANSVERSE Reinforcement Spacing

• 3b. Check

LONGITUDINAL Reinforcement for Lap Splices Check Development of Column Longitudinal Reinforcement Yes No s <= min(6db, 8”)  “DUCTILE” Flexural failure

• 4b. Check Confinement
• f Plastic Hinge Regions

(adjacent to fixed connections at footing and/or bent cap) s >= min(6db, 8”) “STRENGTH DEGRADING” Flexural failure #4 @ 12” (typ. of pre ‘72)

• r spacing

> 12” Yes No “BRITTLE” Shear Dominated Failure Yes No

• 5. Comments

End End End End End End End End End End End End End End End Splicing not an issue. Check Column Transverse Reinforcement

PHASE II – DETERMINE DAMAGE LEVEL

Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Strength Degrading Curve Brittle Curve

X X X Lateral Displacement

Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Strength Degrading Curve Brittle Curve

X X X Lateral Displacement Lateral Force

Ductile Curve Strength Degrading Curve Brittle Curve

X X X Lateral Displacement

Where is your column on each curve?

Performance Classifications (Five Damage Levels)

Damage Level Damage Classification Damage Description Repair Description Socio- Economic Description I None Barely visible cracking No Repair Fully Operational II Minor Minor cracking Possible Repair Operational III Moderate Open cracks; onset

• f spalling

Minimum Repair Life Safety IV Major Very wide cracks; extended spalling Repair Near Collapse V Local Failure/Collapse Reinforcement buckling/rupture; Visible structural damage Replacement

• r substantial

retrofit Collapse

(Ref. Hose)

PHASE II – DETERMINE DAMAGE LEVEL

 Step 1. - Check for diagonal cracks.  Step 2. - Check for horizontal cracks.  Step 3. - Check for concrete crushing or spalling.  Step 4. - Check for longitudinal bar buckling.  Step 5. - Check for rupture of transverse

reinforcement

 Step 6. - Determine the damage level based on

the observations above.

Determination of Extension of Diagonal Cracks

Extension of diagonal cracks D Extension of diagonal cracks D

Length of Spalled Region

Length of spalled region D spalled concrete Length of spalled region D spalled concrete

Performance Assessment

Damage Level Performance Level Qualitative Performance Description Quantitative Performance Description

I Cracking Onset of hairline cracks Barely visible residual cracks II Yielding Theoretical first yield of longitudinal reinforcement Residual crack width ~ 0.008in III Initiation of Local Mechanism Initiation of inelastic deformation. Onset of concrete spalling. Development of diagonal cracks. Residual crack width 0.04in – 0.08in Length of spalled region >1/10 cross- section depth. IV Full Development of Local Mechanism Wide crack widths/spalling over full local mechanism region. Residual crack width > 0.08in. Diagonal cracks extend over 2/3 cross-section depth. Length of spalled region > ½ cross- section depth. V Strength Degradation Buckling of main reinforcement. Rupture of transverse reinforcement. Crushing of core concrete. Lateral capacity below 85% of maximum. Section depth expands to >5% of

• riginal dimension.

(Ref. Hose)

Decision-making Matrix for Damaged Bridge Columns

Pronounced Horizontal Cracks Pronounced Diagonal Cracks Incipient Concrete Crushing/ Spalling

• Long. Bar

Buckling Damage Level Possible Failure Type No Yes No No III Shear Yes or No Yes Yes Yes or No IV or V Shear Yes No No No II or III Flexure Yes No Yes No IV Flexure Yes No Yes Yes V Flexure Conclusions Field Observations

PHASE III – ASSESS BRIDGE SYSTEM

Lateral Force

Brittle Curve

X Lateral Displacement x

Level I Level II Level III Level IV Level V Bent 1 – Column 1 (Brittle) Bent 1 – Column 2 (Brittle) Remaining Capacity

Lateral Force

Brittle Curve

X Lateral Displacement x

Level I Level II Level III Level IV Level V

x

Level I Level II Level III Level IV Level V Bent 1 – Column 1 (Brittle) Bent 1 – Column 2 (Brittle) Remaining Capacity

Lateral Force

Strength Degrading Curve

X Lateral Displacement x

Level I Level II Level III Level IV Level V Bent 2 – Columns 1 and 2 (Strength Degrading) Remaining Capacity

Lateral Force

Strength Degrading Curve

X Lateral Displacement x

Level I Level II Level III Level IV Level V

x

Level I Level II Level III Level IV Level V Bent 2 – Columns 1 and 2 (Strength Degrading) Remaining Capacity

Thanks! Questions?

References

• ATC. 2002. Rapid Visual Screening of Buildings for Potential Seismic Hazards: A
• Handbook. FEMA P-154, Edition 2.
• ATC. 2005. ATC-20-1: Field Manual: Procedures for the Postearthquake Safety

Evaluation of Buildings, Second Edition. Applied Technology Council, Redwood City, California. Hose, Y.D., Silva, P., Seible, F., “Performance Library of Concrete Bridge Components, Sub-Assemblages, and Systems under Simulated Seismic Loads”, Structural Systems Research Program, SSRP 99/08, University of California, San Diego, La Jolla, CA, January, 1999. O’Connor, J. S. 2010. Post-Earthquake Bridge Inspection Guidelines. Final Report for NYSDOT SPR Project # C-06-14. Reed, D. A., and J. Wang. 1993. An Emergency Response Plan for Bridge

• Management. Report No. WA-RD 289.1. Washington Department of

Transportation. Veletzos, Panagiotau and Restrepo. 2006. Post Seismic Inspection and Capacity Assessment of Reinforced Concrete Bridges. UCSD Structural Systems Research Project SSRP-06/19.

Training Course: Post Earthquake Inspection and Capacity Assessment

• f RC Bridges

Prepared by: University of California, San Diego Department of Structural Engineering

Lectures

Lecture 1: Introduction, Seismic Design Concepts (A) Lecture 2: Seismic Design Concepts (B) Lecture 3: Performance of Bridge Components (A) Lecture 4: Performance of Bridge Components (B) Lecture 5: Post Earthquake Evaluation Lecture 6: Lessons Learned

Lecture 6 – Lessons Learned

 Flexure vs. Shear  Design Era  Shear vs. Lap Splice  Abutments  Connections

Lesson 1a. Flexure vs. Shear

Lecture 6

Flexural behavior (ductile curve) is progressive and gives warning Shear behavior (brittle curve) is sudden and compromises gravity load carrying capacity.

Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV

Lesson 1b. Flexure vs. Shear

Lecture 6

Level II – Flexural Column  Horizontal cracks Level II – Shear Column  Diagonal cracks

Flexure and shear have different crack patterns

Lesson 1c. Flexure vs. Shear

Lecture 6

Level IV Flexure Level IV Shear

Similar level of damage  very different amount of remaining capacity

Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Brittle Curve

X X Lateral Displacement

Level IV

Lesson 2a. Design Era

Lecture 6

Similar level of damage (crack sizes)  different amount of remaining capacity

Level IV Post ‘71 Level IV Pre ‘71

Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Strength Degrading Curve

X X Lateral Displacement

Level IV Level I Level II Level III Level IV Level V Level V

Lateral Force

Ductile Curve Strength Degrading Curve

X X Lateral Displacement

Level IV

Lesson 2b. Design Era

Lecture 6

Pre ’71 columns  typically strength degrading

• r brittle behavior

Level I Level II Level III Level V Lateral Force Strength Degrading Curve Brittle Curve

X X

Lateral Displacement Level I Level II Level III Level IV Level V

Lesson 2c. Design Era

Lecture 6

Pre ’94 columns with aspect ratio < 4  susceptible to brittle shear behavior

Lesson 2d. Design Era

Lecture 6

Post ’94 columns with aspect ratio >4  typically ductile flexural behavior

Note heavy confinement

• f hinge

region

Lesson 3. Shear vs. Lap Splice

Lecture 6

Shear F-∆ Response Lap Splice F-∆ Response

Similar response, but ….

Lesson 3. Shear vs. Lap Splice

Lecture 6

Shear Failure Lap Splice Failure lap splice failure may retain vertical load capacity. Shear failure will not support gravity load.

Lesson 4. Abutments

Lecture 6

typically characterized by brittle performance curve

Lesson 5. Connections

Lecture 6

Pre ’94 designs  typically brittle

Note lack

• f joint

reinforcement