HYDRAULIC VULNERABILITY ASSESSMENT IMPLEMENTATION AND ...

NYSDOT

BRIDGE SAFETY
ASSURANCE PROGRAM

HYDRAULIC VULNERABILITY
ASSESSMENT

IMPLEMENTATION
AND MONITORING

HYDRAULIC VULNERABILITY

Overview of the Hydraulic
Vulnerability Assessment Process
FHWA Item 113 Codes
Monitoring

Floodwatch
Post Flood Inspection

HYDRAULIC VULNERABILITY

Approximately
60% of bridge
failures are due
to hydraulic
forces.

Catastrophic
Partial
Collapse
Structural
Damage

HYDRAULIC VULNERABILITY

Schoharie Bridge
Failure - April 1987

Technical Advisory
T 5140.20 -- 1988
Technical Advisory
T 5140.23 -- 1991

New bridges
designed for scour
Evaluate existing bridges for scour
23 CFR 650.313.e.3 -- 2005

HYDRAULIC VULNERABILITY
ASSESSMENT

1. Screening
2. Classifying
3. Rating
4. Plan of Action

ƒ Monitoring

HYDRAULIC VULNERABILITY
ASSESSMENT (HVA)

1. Screening – Prioritize bridges to
proceed with HVA
assessment.

Was not done for local bridges

HYDRAULIC VULNERABILITY
ASSESSMENT

2. Classifying -- Evaluates the
vulnerability of a
structure to scour
failure.

General Hydraulic Assessment
Foundation Assessment

HYDRAULIC VULNERABILITY
ASSESSMENT

2. Classifying – General Hydraulic
Assessment

Streambed Material
River Slope
Historic Scour Depth
Adequate Opening
Channel Bottom
Channel Configuration

Refer to binder-Session #2-for detail form

HYDRAULIC VULNERABILITY
ASSESSMENT

2. Classifying – Foundation Assessment
Abutments and Piers

Existing Scour
Countermeasure
Foundation Type
Culverts
-- Less susceptible

to scour damage?
Refer to binder-Session #2-for detail form

CLASSIFICATION

Final General Foundation

Classification = Hydraulic + Assessment

Score Assessment Score

Higher of the
Abutment and

Pier Scores

Refer to binder-Session #2-for detail form

HYDRAULIC VULNERABILITY
ASSESSMENT

2. Classifying – Vulnerability Class

Classification < 25 20 - 40 >35
Score LOW MEDIUM HIGH

Vulnerability
Class

Refer to binder-Session #2-for detail form

HYDRAULIC VULNERABILITY
CLASSES

1. LOW -- Bridge has little potential for failure.

2. MEDIUM -- There is a recognizable potential
for failure from several storm
events.

3. HIGH -- The occurrence of a single intermediate
or large flood could result in failure.

HYDRAULIC VULNERABILITY
ASSESSMENT

3. Rating – Provide a uniform measure

of the structure’s vulnerability
to failure.

VULNERABILITY RATING
PROCEDURE

Bridge Exposure Failure Type
Classification Traffic Funct.
Volume Class
High-10
Medium-6

Low-2

Likelihood Score Consequence Score

Vulnerability Rating

VULNERABILITY RATING SCORE

Rating Rating Score

> 15 1 Safety Priority

13 - 16 2 Safety Program
9 - 14 3 Capital Program
4 Inspection Program
< 15 5 No Action
<9

Refer to binder-Session #2-for detail form

FHWA Item 113 Code
Scour Critical Bridge

Foundation of abutment or pier is unstable
due to observed, calculated or assessed
scour depth.

FHWA 113 Code - Scour Critical Bridge

‘0’ = Bridge has failed and is closed to
traffic.

FHWA 113 Code - Scour Critical Bridge

‘1’ = Field review indicates that failure of piers
and/or abutments is imminent.
Bridge is closed to traffic.

FHWA 113 Code - Scour Critical Bridge

‘2’ = Field review indicates that extensive
scour has occurred at bridge
foundations.

FHWA 113 Code - Scour Critical Bridge

Spread on Earth Supported on Piles

Assessed Are Piles
Scour Depth Stable?

‘3’ = Bridge foundations determined to be
unstable for assessed or calculated
scour conditions.

FHWA 113 Code - Scour Critical Bridge

‘7’ = Countermeasures have been installed to

mitigate an existing problem with scour
and to reduce the risk of bridge failure
during a flood event.

FHWA 113 Code
Scour Critical Bridge re-coded to “8”

‘8’ = Bridge was analyzed, countermeasure has

been designed and installed to mitigate all
existing and potential scour conditions.

FHWA 113 Code - Scour Critical Bridge

‘U’ = “Unknown” foundation that has not been

evaluated.

HYDRAULIC VULNERABILITY
ASSESSMENT

4. Plan of Action
(POA):

23 CFR 650.313.e.3
Scour Critical
bridges
Detour route
in place

HYDRAULIC VULNERABILITY
ASSESSMENT

4. Plan of Action
(POA):

Scour Retrofit
and

Countermeasures
- HEC 23

A properly designed
and installed
countermeasure can
remove a structure
from the POA.

HYDRAULIC VULNERABILITY
ASSESSMENT

4. Plan of Action:

Monitoring -- Flood Watch
-- Post Flood
Inspection

Plan of Action

Monitoring: Floodwatch
Post Flood Inspections

What ?
When ?
Who ?
Where ?
How ?

Monitoring

Floodwatch Program - What bridges?
Classification Score

High
Medium, based on recommendation by RHE

FHWA Item 113 Code

“2”
“3”
Maybe “U”

Rating Score

1 and 2
3, based on RHE recommendation

Monitoring

Floodwatch Program - What bridges?

Bridges flagged by inspectors for scour
damage.

Monitoring

Floodwatch Program - When?

During Flood Warning issued by the
National Weather Service (NWS).

During Flash Flood Warnings????

Reports of flooding from local
residents and/or maintenance crew.

Monitoring

Floodwatch Program – Who…

…determines what bridges are on the
Flood Watch Program?

…receives notification of Flood Warnings?
…carries out the Flood Watch?
…carries out Post Flood Inspections?
…reopens a bridge after it was closed as

a result of Flood Watch?

Monitoring

Floodwatch Program - Where?

GIS database of Scour Critical bridges
Track storms using satellite imagery

Internet

Monitoring

Floodwatch Program - How?

Continual Monitoring
High Risk bridges: Potential to have a
sudden or catastrophic collapse.

Monitoring

Floodwatch Program - How?

Periodic Monitoring:

Non-High Risk bridges: Bridges that will
undergo structural damage/partial
collapse as
a result of
substructure
movement.

Flood Watch Program

Inspection Procedures:

Flood Warning Inspection Report
– Critical Items

Alignment
Tilt
Vibration
Freeboard
Snagging Debris
Bridge Noise
Superstructure Distress

Flood Watch Program

Inspection Procedures:

Flood Warning Inspection Report
– Non-Critical Items

Length
Erosion
Settlement
Cracking
Debris
Impacting Debris
Flow Characteristics
Stream Noise

Critical Items

Alignment

– Vertical
– Horizontal

• Any change in
alignment
should result in
bridge closure.

Critical Items

Tilt

– Plumbness of
piers and
abutments

– Change of
inclination of
bearings

• Any change
should result in
bridge closure.

Critical Items

Vibration

– Check for
vibration or
swaying motion
from stream
flow.

• Any noticeable
amount should
result in bridge
closure.

Critical Items

Freeboard

– Zero freeboard or overtopping is cause
for immediate closure.

Critical Items

Freeboard

– Critical freeboard or water depth

Critical Items

Snagging Debris

– Any noticeable amount of snagging
debris caught along the structure is
cause for immediate closure.

Critical Items

Noise

– When there is no traffic, listen for creaks,
groans, snapping, or popping noises coming
from the bridge.

Non-Critical Items

Length

– An increase or decrease in bridge length,
measured at the deck or curb joints.

Non-Critical Items

Erosion

– Check approach roadways, embankments
slopes, shoulders, and pavement for erosion.

Non-Critical Items

Settlement

– Check approach roadways, embankments
slopes, shoulders, and pavement for
settlement.

Non-Critical Items

Cracking

– Look for cracking in pavement, shoulder
areas, and embankment slopes.

Flood Watch Program

Reopening a closed bridge as a
result of a flood watch.

The bridge can only be
reopened with the
approval of a
Professional Engineer
registered to practice in
New York State.

Post Flood Inspection Program

All bridges on the Floodwatch Program

FHWA Item 113 Code “7”, “U”

Recommended by RHE
Should be done as soon as flood water
recedes (or within 2 Weeks)
Scour Damage

– Should be retrofitted ASAP
– If not, bridge should be included on the

Floodwatch Program (if not already on it)

Post Flood Inspection Program

Bridge Pier