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Life-Cycle-Cost Model for the Design of a Bridge Vibration
Monitoring System (LCC-BVMS) Ahsan Zulfiqar
Miryam CabiesesAndrew Mikhail
Namra Khan
Department of Systems Engineering and Operations Research - 2014 1
Faculty Advisor:Dr. Lance Sherry (GMU)
Sponsor:Dr. Lattanzi (GMU
Civil, Environmental, and Infrastructure
Engineering (CEIE))
Current Manual Inspection System
BVMS
Agenda
2
1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
Context1. 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 bridgeii Up to 3 months for the entire
inspectioniii $4,500-$30,000 per inspection
b Bi-Annual inspection cost is $2.7 billion for the U.S.
3. Bridges infrastructure is deterioratinga Increasing maintenance costb Increasing inspection process cycle
3T. 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
4
General Inspection Procedures
http://www.fhwa.dot.gov/bridge/nbis/pubs/nhi12049.pdf
Receipt of Bridge to Inspect
Review Inspection Documents/Records
Review load ratings
Review construction records
Plan for Inspection
Determine the type of inspection needed
Select inspection team
Evaluate required activities
Establish a schedule
Prepare for Inspection
Review the bridge structure file
Identify components & elements
Develop an inspection system
Arrange for temporary traffic
control
Order tools & equipment
Perform On-site Inspection
Visual examination of bridge
components
Physical examination of bridge
components
Evaluation of bridge components
Report
Document data collected
21 States W/ Structurally Deficient Bridges
5
● 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+
Periodic Manual Inspection Historical Data
6
● Total number of defects found per bridge per inspection year● Total time to repair already detected defect (lag time)
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-collapse7
Arch:
Beam:
Cantilever:
Suspension:
Bridge Types & Components
8http://www.ikonet.com/en/visualdictionary/transport-and-machinery/road-transport/
T. J. Ryan, J. E. Mann, Z. Chill, and B. Ott, “Bridge Inspector’s
Reference Manual.” Federal Highway Administration, Dec-2012.
Beam Bridge
Beam bridge inspection process
Structural Vibration 1. Structural vibration is repetitive motion that can
be measured and observed in a structure.2. Factors that affect vibration are characterized by
the following parameters:a mass b stiffnessc damping
3. Vibration analysis:a Free vibrationb Forced vibrationc Sinusoidal vibrationd random vibration
4. Helps characterize the behavior of the structure (Unique Fingerprint)
5. Knowing these values can predict how structure will respond to vibration
9
Main Components & Failure Types Component Material Type of failure Inspection Method Percentage to
cause failureDetection Method
Deck Metal Cracking Visual/Physical
Vibration Analysis
● Roadway Fatigue (less stiff) Physical 13.05%
● Side walk Corrosion (Loss of mass) Visual/Physical 3.26%
Substructure Bending Visual Image Capturing device
● Abutments Missing connection Visual/Physical
Vibration Analysis ● Piers Concrete Section loss Visual/Physical 20.65%
Super-Structure Structure crack at critical point (ex: Fracture critical…)
Visual/Physical 16.3%
● Floor beams Severe deterioration Visual 2.17% Image Capturing device
10Bridge Failure Rates, Consequences, and Predictive Trends by Wesley CookUtah State University
Agenda
11
1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
-
DOT Design Engineer
Construction Team
Inspection Team
Bridge Users
FHWA
Stakeholder Analysis Hires a consulting engineering company to design a bridge
Designs the Bridge
Bids the project to contractors
Provides the bridge design
Wins the bid and constructs the bridge
Fund
s pa
rt of
the
brid
ge a
nd ta
ke p
artia
l ow
ners
hip
Hire
s th
em fo
r saf
ety
insp
ectio
n
Fund
s th
e br
idge
Inspects bridge
12
InteractionsPrimarySecondaryTensions
Bridge
#2 Liable
#3 Liable
#1 Liable
Lose Jobs/Lower pay
#4: Lane Shutdown Time and Cost
+ +
+
-
+ SupportOpposeNeutral
/
/
/
Tension #1: DOT holds Inspection team liableTension #2: Inspection team holds design engineers liableTension #3: Inspection team holds construction team liableTension #4: Bridge users complain to DOT about lane shutdown
Agenda
13
1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
1. High bi-annual inspection cost ($2.7 billion)2. Periodic Bi-annual inspections → delay in detection of deficiencies3. Lag in the repair times puts stress on other components of the bridge
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Problem Statement
1. Reduce total Inspection cost● Labor, Traffic Control, Equipment● Decrease the rate of inspection
2. Detect deficiencies when they occur3. Bridge Monitoring System
Need Statement
Agenda
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1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
1. The system shall monitor all bridge components 2. The system shall reduce the number of inspections
performed on a bridge3. 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.
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System Requirements for an Event-Based System
1. 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.
2. The Event-based system shall convert the vibration data from time domain to frequency domain.
3. 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.
4. The Event-based system shall alert the base if the frequency of the accelerometer captures a deficiency for 7 consecutive days.
5. 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.
Design Requirements for an Event-Based System
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Component Diagram
18
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
A1
A2
A3
A4
A5
Data Acquisition Unit (DAU)
Electrical Signal
Base Monitoring Unit
OR
Fourier Transform Analysis
Time Domain Frequency Domain
Agenda
19
1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
Bridge Vibration Monitoring System Concept of Operations
Bridge Vibration Monitoring System (BVMS):1. Bridges Vibrate due to dynamic loading2. 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
Inspecting the entire bridgeAlarm when changes in vibration
Inspect the entire bridge
20
How Accelerometers Work1. Structural vibrations can be measured by electronic sensors
that convert vibration motion into electrical signals.2. Motion Sensors/Accelerometers3. Based on Piezoelectric Effect
pcb.com
gcdataconcepts.com21
Fourier transformation
A1221L-005
Natural Frequency
BVMS Design Alternatives
22
Time Cost
Periodic Inspection
1) Manual Inspection
Actual inspection (1-3 days) $4500/inspection
Event Based Inspection
2) Wired Sensors Total time to perform Inspection
(simulation)
Acquisition Cost: $77,000
Manual Inspection 1-3 days $4,500/inspection
3) Wireless Sensors with low-power communication systems
Total time to perform Inspection
(simulation)
Acquisition Cost: $75,000
Concurrent Cost: $1000/year
Manual Inspection 1-3 days $4,500/inspection
Agenda
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1. Context2. Stakeholder Analysis3. Problem/Need Statement4. Requirements5. Proposed Solution6. Simulation
Method of Analysis
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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)
biannually
Increase year by 2
Simulation Requirement1. 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.
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Periodic Manual Historical DataAll Bridges
Year Built 1945 1964 1965 1965 1942 1950
length 66.93 213.91 90.88 116.14 208.99 122.05
No. 1 2 3 4 5 6
Bridge # 1 2 3 4 5 6 7 8 9 10
Inspections Year Range Number of Repairs Identified
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
Range: 1973- 2014
Inspections: 20
Sections: 10 Years
26
Simulation
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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.
…...
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
Design of ExperimentInputs 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
times (20% increase)Table with probability of
defects found per year
13.85 6.506
Table with longer delay to repair
times (10% increase)Table with probability of
defects found per year
13.73 6.364
Table from Historic delay to
repair times
Table with probability of
defects found per year
13.89 6.326
Table with shorter delay to
repair times (10% decrease)Table with probability of
defects found per year
11.84 4.338
Table with shorter delay to
repair times (20% decrease)Table with probability of
defects found per year
10.13 3.413
30
Periodic vs. Event Based BVMS Total Cost for a 50 Year Lifespan
31
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
Periodic
Manual $0.9M $0.9M $0.9M
Manual:30000*(30 inspections)
Event-Based BVMS Inspection Cost
50 years monitoring Worst Expected Best
BVMSμ+2σ μ μ-2σ
$365k $268k $170k
33
AVG (μ) $267,600
STD (σ) $48,557
Mode $270,000
● 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 95%
confidence level
Life-Cycle-Cost (LCC) of Periodic vs. Event-Based in 50 Years
34
Breaking Even Point:42 years Wired
Breaking Even Point:41 years Wireless
Business CaseTotal 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
36
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)
Multi-Attribute Utility Theory (MAUT)
37
Utility = WA + WS + WU = 1WS = WBI + WBU = 1
Availability(0.3)
Safety (0.4) Communicability(0.3)
Bridge Inspectors (0.5) Bridge Users (0.5)
Range 1-10 1-10 1-10 1-10
Preference Higher the better Higher the better Higher the better Score
Periodic 1 3 7 9 5
Event-Based 9 10 9 8 8.9
● 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?
Note: Utility for Wireless & Wired Alternatives are similar, therefore, only Wireless is taken into account.
Utility Vs. Cost
Lifecycle Cost
Utility
0.5M 1M
BVMS
Manual (Current)
5
10
0
38Note: Wireless & Wired Alternatives are similar, therefore, only Wireless is taken into account.
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
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