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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

http://www.infrastructurereportcard.org/a/#p/bridges/conditions-and-capacity

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

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● 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

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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


-

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

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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

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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

15


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

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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

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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

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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

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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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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

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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.

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Simulation Sample OutputHistorical Data Repairs happening 20% earlier

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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


13.73 6.364

Table from Historic delay to

repair times

Table with probability of


13.89 6.326

Table with shorter delay to

repair times (10% decrease)Table with probability of


11.84 4.338

Table with shorter delay to

repair times (20% decrease)Table with probability of


10.13 3.413

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Periodic vs. Event Based BVMS Total Cost for a 50 Year Lifespan

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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 Equipment Cost

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Event-Based BVMS Inspection Cost


BVMSμ+2σ μ μ-2σ

$365k $268k $170k

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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

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Breaking Even Point:42 years Wired

Breaking Even Point:41 years Wireless

LCC Model Recap

OR

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Business CaseTotal Cost Savings


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

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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)

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Questions

41