Life-Cycle-Cost Model for the
Design of a Bridge Vibration
Monitoring System (LCC-BVMS)
Current Manual Inspection System
Ahsan Zulfiqar
Miryam Cabieses
Andrew Mikhail
Namra Khan
Sponsor:
Dr. Lattanzi (GMU
Civil, Environmental,
and Infrastructure
Engineering (CEIE))
BVMS
Faculty Advisor:
Dr. Lance Sherry (GMU)
Department of Systems Engineering and Operations Research - 2014
1
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
2
Context
1. The Federal Highway Administration
(FHWA) administers 607,380 bridges
a Average age is 42 years.
2. Manual inspection process
a Every two years
i 1-3 days to inspect one bridge
ii Up to 3 months for the entire
inspection
iii $4,500-$30,000 per inspection
b Bi-Annual inspection cost is $2.7
billion for the U.S.
3. Bridges infrastructure is deteriorating
a Increasing maintenance cost
b Increasing inspection process cycle
T. J. Ryan, J. E. Mann, Z. Chill, and B. Ott, “Bridge Inspector’s Reference Manual.” Federal Highway Administration, Dec-2012.
http://www.infrastructurereportcard.org/a/#p/bridges/conditions-and-capacity
3
General Inspection Procedures
Receipt of Bridge to
Inspect
Plan for Inspection
Prepare for
Inspection
Perform On-site
Inspection
Review Inspection
Documents/Records
Determine the type
of inspection needed
Review the bridge
structure file
Visual examination
of bridge
components
Review load ratings
Select inspection
team
Identify components
& elements
Physical examination
of bridge
components
Review construction
records
Evaluate required
activities
Develop an
inspection system
Evaluation of bridge
components
Establish a schedule
Arrange for
temporary traffic
control
Report
Document data
collected
Order tools &
equipment
http://www.fhwa.dot.gov/bridge/nbis/pubs/nhi12049.pdf
4
21 States W/ Structurally Deficient Bridges
● Fatigue damage is increasing faster than the growth in inspection and repair.
● American Society of Civil Engineers (ASCE) rate bridges in the U.S. a C+
5
Periodic Manual Inspection
Historical Data
●
●
Total number of defects found per bridge per inspection year
Total time to repair already detected defect (lag time)
6
Causes of Bridge Component Failure
●
●
●
●
●
●
High winds and poor weather
conditions
Maximum loading
Vibration amplification
Applied stress
General wear and tear
...
● Delay in
Inspections
http://www.hmpfmlaw.com/articles/bridge-collapse
7
Bridge Types & Components
Arch:
Beam Bridge
Beam:
Cantilever:
Beam bridge inspection process
Suspension:
T. J. Ryan, J. E. Mann, Z. Chill, and B. Ott, “Bridge Inspector’s
http://www.ikonet.com/en/visualdictionary/transport-and-machinery/road-transport/
Reference Manual.” Federal Highway Administration, Dec-2012.
8
Structural Vibration
1.
2.
3.
4.
5.
Structural vibration is repetitive motion that can
be measured and observed in a structure.
Factors that affect vibration are characterized by
the following parameters:
a mass
b stiffness
c damping
Vibration analysis:
a Free vibration
b Forced vibration
c Sinusoidal vibration
d random vibration
Helps characterize the behavior of the structure
(Unique Fingerprint)
Knowing these values can predict how structure
will respond to vibration
9
Main Components & Failure Types
Component
Deck
●
Material
Metal
Roadway
Type of failure
Inspection Method
Cracking
Visual/Physical
Fatigue (less stiff)
Physical
Percentage to
cause failure
Detection Method
13.05%
Vibration Analysis
●
Side walk
Substructure
●
Abutments
●
Piers
Concrete
Corrosion (Loss of mass)
Visual/Physical
Bending
Visual
Missing connection
Visual/Physical
Section loss
Visual/Physical
3.26%
Image Capturing
device
20.65%
Vibration Analysis
Super-Structure
●
Floor beams
Structure crack at critical
point (ex: Fracture
critical…)
Visual/Physical
16.3%
Severe deterioration
Visual
2.17%
Bridge Failure Rates, Consequences, and Predictive Trends by Wesley Cook
Utah State University
Image Capturing
device
10
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
11
Stakeholder Analysis
#4: Lane Shutdown Time and Cost
Hires a consulting engineering company to design a bridge
+
+
#1
ay
ble
rp
Lia owe
/L
bs
Jo
Hires them for safety inspection
Designs the Bridge
se
Funds the bridge
DOT
Bid
s
Pro the p
vide roje
s th ct to
eb
ridg contra
ed
esig ctors
n
/
In
e
sp
cts
-
ts
th
id
eb
and
c
stru
n
o
c
b
the
ridg
b
Lia
Construction
Team
/
e
Bridge Users
Bridge
-/
#2
#3 Liable
dg
bri
s
Win
+
le
Inspection
Team
e
Interactions
Primary
Secondary
Tensions
Design
Engineer
Lo
Funds part of the bridge and take partial ownership
FHWA
Support
Oppose
Neutral
Tension #1: DOT holds Inspection team liable
Tension #2: Inspection team holds design engineers liable
Tension #3: Inspection team holds construction team liable
Tension #4: Bridge users complain to DOT about lane shutdown
+
12
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
13
Problem Statement
1.
2.
3.
High bi-annual inspection cost ($2.7 billion)
Periodic Bi-annual inspections → delay in detection of deficiencies
Lag in the repair times puts stress on other components of the bridge
Need Statement
1.
2.
3.
Reduce total Inspection cost
● Labor, Traffic Control, Equipment
● Decrease the rate of inspection
Detect deficiencies when they occur
Bridge Monitoring System
14
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
15
System Requirements for an
Event-Based System
1. The system shall monitor all bridge components
2. The system shall reduce the number of inspections
performed on a bridge
3. The system shall increase the rate of detection and detect
deficiencies when they occur by being continuously
available
4. The system shall be able to communicate all the data
collected to the Bridge Engineers.
16
Design Requirements for an
Event-Based System
1.
2.
3.
4.
5.
The Event-based system shall consist of the following functional components:
Acceleration detection sensors, Data Acquisition Unit (DAU), communication
between sensors and DAU, Base monitoring unit, and communication
between DAU and base monitoring unit.
The Event-based system shall convert the vibration data from time domain to
frequency domain.
The Event-based system shall send the bridge vibration frequency data to the
Data Acquisition Unit (DAU) from each accelerometer each day via a
communication network system.
The Event-based system shall alert the base if the frequency of the
accelerometer captures a deficiency for 7 consecutive days.
The Event-based system shall obtain the natural frequencies of each
component and compare it to the standard natural frequency that each bridge
component exhibits.
17
Component Diagram
Data Acquisition Unit (DAU)
A1
Time Domain
A2
A3
Electrical
Signal
Fourier
Transform
Analysis
Frequency Domain
A4
A5
OR
Alarm if there is a change in
natural frequency when
compared to reference vibration
fingerprint for 7 days
Do nothing if there is no
change in natural frequency
when compared to reference
vibrations fingerprint
Base
Monitoring
Unit
18
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
19
Bridge Vibration Monitoring System
Concept of Operations
Bridge Vibration Monitoring System (BVMS):
1. Bridges Vibrate due to dynamic loading
2. Unique vibration fingerprint
3. Accelerometers can be used to detect changes in the fingerprint due to deficiencies
Current System
BVMS
Periodic (~ every 2 years)
Event-Based (when needed)
All Manual
Accelerometers with Manual
Alarm when changes in vibration
Inspecting the entire bridge
Inspect the entire bridge
20
How Accelerometers
Work
A1221L-005
1. Structural vibrations can be measured by electronic sensors
that convert vibration motion into electrical signals.
2. Motion Sensors/Accelerometers
3. Based on Piezoelectric Effect
Natural
Frequency
Fourier
transformation
pcb.com
gcdataconcepts.com
21
BVMS Design Alternatives
Time
Cost
Periodic Inspection
1) Manual Inspection
Actual inspection (1-3
days)
$4500/inspection
Event Based Inspection
2) Wired Sensors
Manual Inspection
3) Wireless Sensors
with low-power
communication
systems
Manual Inspection
Total time to perform
Inspection
(simulation)
1-3 days
Total time to perform
Inspection
(simulation)
1-3 days
Acquisition Cost:
$77,000
$4,500/inspection
Acquisition Cost:
$75,000
Concurrent Cost:
$1000/year
$4,500/inspection
22
Agenda
1.
2.
3.
4.
5.
6.
Context
Stakeholder Analysis
Problem/Need Statement
Requirements
Proposed Solution
Simulation
23
Method of Analysis
biannually
Increase
year by 2
Inputs:
Probability of defects to be found per year derived from historical data
Probability of defects to be repaired in year “i” derived from historical data
Outputs:
Deficiency and Repair data for 100 bridges
Total number of defects found per bridge per year (average of 100 iterations)
Time it takes to repair the deficiencies found in year “i” (average of 100 iterations)
24
Simulation Requirement
1. The simulation shall use the periodic historical data for
deficiencies found on a bridge to generate the number of
defects.
2. The simulation shall compare the probability of finding the
number of defects on a bridge to the randomly generated
probability which uses a uniform distribution to identify the
number of defects found bi-annually.
3. The simulation shall use the probability of the time to
repair a defect found to assign the number of years it will
take to repair an identified defect.
25
Periodic Manual Historical Data
All Bridges
Year Built
1945
1964
1965
1965
1942
1950
Range:
1973- 2014
length
66.93
213.91
90.88
116.14
208.99
122.05
Inspections:
20
No.
1
2
3
4
5
6
Sections:
10 Years
Bridge #
1
2
3
4
5
6
7
8
9
10
Inspections
Year
Range
5
1973-1982
0
2
1
0
3
1
5
1
2
2
5
1983- 1992
2
3
3
2
6
3
5
4
2
3
5
1993-2002
4
3
3
3
2
4
2
2
3
4
5
2003-2014
6
10
6
7
5
5
7
6
4
5
Number of Repairs Identified
26
Simulation
Calculate Total Defects:
…...
●
●
Demonstrates multinomial distribution with 26 inspections for 17 bridges for 51
years with its fixed success probability of identifying a defect for that given year.
Uniform random generator is used to calculate the total number of defects per
bridge bi-annually with 100 iterations for 51 years repeated for 100 bridges.
27
Simulation (Cont.)
Calculate Total Repairs:
●
●
Used in the monte carlo simulation to compare randomly
generated probabilities using a uniform distribution to the
probabilities shown on the left.
Giving an output of the lag time between the identified
defect to the actual repair.
28
Simulation Sample Output
Historical Data
Repairs happening 20% earlier
29
Design of Experiment
Inputs
Outputs (Results at 51 Years)
Defects Fixed per Year
New defects Per Year
Defects Remaining
on Bridge
Mean time to
repair a defect
found
Table with longer delay to repair
Table with probability of
defects found per year
13.85
6.506
13.73
6.364
times (10% increase)
Table with probability of
defects found per year
Table from Historic delay to
repair times
Table with probability of
defects found per year
13.89
6.326
Table with shorter delay to
Table with probability of
defects found per year
11.84
4.338
Table with probability of
defects found per year
10.13
3.413
times (20% increase)
Table with longer delay to repair
repair times (10% decrease)
Table with shorter delay to
repair times (20% decrease)
30
Periodic vs. Event Based BVMS Total Cost
for a 50 Year Lifespan
Total Cost for a 50 Year Lifespan
System Lasts
5 years
8 years
10 years
50 years monitoring
Worst
Expected
Best
Event-Based
Wired
$1.123M
$0.7471M
$0.561M
Wireless
$1.077M
$0.718M
$0.538M
$0.9M
$0.9M
Periodic
Manual
$0.9M
Manual:
30000*(30 inspections)
31
Event-Based BVMS Equipment Cost
32
Event-Based BVMS Inspection Cost
●
Worst, Expected & Best are based on Bridges behaviour:
○ Worst behaviour: Needs more total number of inspections (Higher cost)
■ Longer time to fix repairs identified
○ Expected behaviour: Average total number of inspection (Average Cost)
○ Best behaviour: Less number of inspection needed (Lower Cost)
■ Higher maintainability
50 years monitoring
95%
confidence level
Worst
Expected
Best
AVG (μ)
$267,600
μ+2σ
μ
μ-2σ
STD (σ)
$48,557
$365k
$268k
$170k
BVMS
Mode
$270,000
33
Life-Cycle-Cost (LCC) of Periodic vs. EventBased in 50 Years
Breaking Even Point:
41 years Wireless
Breaking Even Point:
42 years Wired
34
LCC Model Recap
OR
35
Business Case
Total Cost Savings
50 years monitoring
Worst
Expected
Best
Event Based Inspection
Wired
$0.9M- $1.123M
= -$0.223M
%125
$0.9M-$0.7471M=
$0.153M
%17
$0.9M-$0.561M=
$0.339M
%37.7
Wireless
$0.9M-$1.077M=
-$0.177M
%120
$0.9M-$0.718M=
$0.182M
%20.2
$0.9-$0.538M=
$0.362M
%40.2
Periodic Inspection
Manual
$0.9M
$0.9M
$0.9M
Note: In the worst case scenario BVMS implementation would cause higher cost than current cost.
(The monitoring system set lasts for 5 years and highest number of inspections needed for the bridge
based on simulated data)
36
Multi-Attribute Utility Theory (MAUT)
●
Utility = WA + WS + WU = 1
WS = WBI + WBU = 1
●
●
Availability
(0.3)
Safety (0.4)
Communicability
(0.3)
Bridge Inspectors (0.5)
Bridge Users (0.5)
1-10
1-10
1-10
Higher the better
Higher the better
Periodic
1
3
Event-Based
9
10
Range
Preference
Availability: How available
is the alternative?
Safety: How safe are the
alternatives for bridge
users/inspectors?
Communicability: how
easily is the inspection
communicated in bridge
engineers?
1-10
Higher the better
Score
7
9
5
9
8
8.9
Note: Utility for Wireless & Wired Alternatives are similar, therefore, only Wireless is taken into
account.
37
Utility Vs. Cost
Utility
10
BVMS
Manual (Current)
5
0
0.5M
1M
Lifecycle Cost
Note: Wireless & Wired Alternatives are similar, therefore, only Wireless is taken into account.
38
Conclusions & Recommendations
●
●
The Event-Based system is recommended for the following reasons:
○
Savings of up to 40.2%
○
Provides a higher overall utility of 8.9
The Wireless Event-Based system is recommended due to the fact that it will not
require the installation of wires for power source and communication.
39
Special Thanks To...
1. Dr. Sherry (GMU)
2. Dr. Lattanzi (GMU)
3. Will Kenney (GMU)
4. Adil Rizvi (DDOT)
5. Chee How (VDOT)
40
Questions
41