Smart Structures Presentation

8/3/2019 Smart Structures Presentation

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Smart Structures LLC

Leading the Technology inStructural Health Monitoring


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US Transportation Infrastructure Issues Having built the transportation system and with the expansion days largely behind, the biggest

challenge faced by the transportation authorities now in the 21st century is to preserve the qualityof the national investment.

As documented over the past few years by the American Society of Civil Engineers (ASCE),

America is failing to address its current substandard transportation infrastructure conditions,

which affect highway safety and the health of the economy.

Americas highway system is faced with a growing number of concerns, including aging

infrastructure, dramatically expanding traffic volumes, and an urgent need for increased security

and safety.

Improvements are needed in transportation infrastructure, homeland security.

In order to reduce the large number of deficient bridges, a more cost effective procedure for

allocating bridge funds must be established. The principal objective of a Bridge Health Monitoring

System is to make the best use of available funds in an overall bridge maintenance,

rehabilitation, and replacement program.

The decision making, either at the level of the entire bridge population in a state (network level) or

for an individual bridge (project level), is based on bridge conditions at the present and in the

future. The allocation of funds for bridge maintenance can best be made by analyzing the data

collected from sensors and then considering several improvement, maintenance, rehabilitation,

and replacement options and optimizing the selected option on a network or project level.


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Concept of Health Monitoring The Structural Health Monitoring System is designed to monitor and evaluate the

health status for the Bridge and to provide necessary information for facilitatinginspection and maintenance activities.

The sensors of the Structural Health Monitoring System are designed to collectstructural responses such as strain, crack opening displacement and acceleration.

The objectives of Health Monitoring are mainly to:

1) Analyze traffic concerning inputs and responses;

2) Obtain the structures global dynamic characteristics;

3) Obtain real-time data for acceleration, displacement, stress, strain for the structure.

4) Characterize temperature influences on strain, crack opening displacement, andacceleration;

5) Provide information on the extent of crack growth, the state of shear reinforcement in

the web, and possible changes in load carrying capacity;6) Report on overall health of the structure including scouring, bridge bearing, expansion

joints, light posts, sign posts.

7) Determine the parameters for Finite Element model (FEM) updating (important fordamage sensitivity analysis);

8) Provide useful information to help owners and maintenance authorities make rationaldecisions in allocating maintenance and repair budgets.


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Smart Structures

Accomplishments

Smart Structures has been working on the sensor technology development for healthmonitoring of bridges and other civil infrastructure in collaboration with University ofIllinois at Chicago.

Smart Structures has, in collaboration with University of Illinois at Chicagosuccessfully monitored the Kishwaukee bridge in Illinois and installed healthmonitoring systems overseas on bridges and structures in China and Japan.

Smart Structures is involved in integrating sensor technology and developing anddeploying smart monitoring systems on the structures for cost effective managementand preservation of transportation assets and thus improve the safety and efficiencyof highway infrastructure.

Smart Structures collaborates with ATREL (Advance Transportation Research Lab)

also in Rantoul, Illinois which works in cooperation with the Uof I, Army Corp ofEngineers, Association of American Railroads, Federal Aviation Administration,Illinois Department of Transportation, National Cooperative Highway ResearchProgram, other governmental and private agencies.


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Smart Structures

Goals and Vision

With the experience of 3 years of real-time monitoring of the Kishwaukee Bridge onI-39 in Illinois, Smart Structures is involved in integrating sensor technology anddeveloping and deploying smart monitoring systems on the structures for costeffective management and preservation of transportation assets and thus improvethe safety and efficiency of highway infrastructure.

Smart Structures is supporting research in the field of innovative sensordevelopment to introduce new products/technologies to facilitate a better andimproved transportation infrastructure.

Smart Structures will be participating in creating health assessment database forNational Bridge Structures.

Smart Structures promotes improved safety, security, performance and efficiency of

transportation infrastructure.

Smart Structures is participating with a group of business associates to create anindustry association.


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Capabilities

Bridge Damage Inspection and Damage Assessment

Bridge Ratings by Rapid Load Tests Bridge global Health Monitoring Innovative sensor development Rapid sensor assembly for measuring strain, acceleration, displacement, vibration,

strain/stress and temperature. Sensor Integration

Wireless Data Acquisition; facilitating reduction in cable costs and installation. Real time data acquisition, Web-Base Interface Seismic data analysis Monitoring stability of bridge bearings Monitoring for piers, scouring for bridges Expansion joint assessment for bridges

Expansion bearing motion Span rotation Pier tilt and subsidence

Vibration frequency and amplitude Rebar corrosion Assessing the safety of roadside light posts and sign posts


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Kishwaukee BridgeHealth Monitoring Project

The Kishwaukee River Bridge is a

twin pre-stressed concrete box

girder structure located in

Winnebago County, Illinois. The

bridge was the first continuous

single-cell box girder bridge with

pre-cast concrete segments posttensioned and epoxied together.

The box girders are five-span

continuous structures with three

interior spans (250 ft/ 76.2m) and

two exterior spans (170ft/51.8m)

with total length of 1090 ft.

The remote Structural Monitoring System was designed to monitor and

evaluate the health status for the Kishwaukee Southbound Bridge and to

provide necessary information for facilitating inspection and maintenance

activities.


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Sensors Installed on Kishwaukee Bridge

Strain gages, accelerometers, clipgages and LVDT gages wereinstalled on the bridge for globaland local monitoring of the bridge.

Local strains and displacementswere measured on the inside andoutside of the webs, the presenceand extent of crack growth andstate of shear reinforcement inwebs were observed. FEM modelupdating for global monitoring wasperformed.

Static load test was performed on

the bridge in 2000, mid-spandeflection, axial strains in webclosures; average strains and crackopening in webs were recorded.Shear stress/strain analysis wasperformed.


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Sensor Network (Optical fiber cable)

DataArchiving

Data

Processing

Expert

System

Internet

LAN

Sensor Station# 1

Sensor Station# 2

Sensor Station# 3

Sensor Station# n

Main

Server

Web

Server

/User

Interface

Customer

PC

Customer

PC

Distributed data

processing andstructure analyzing

Ethernet-based data

transmission

Powerful data storage

and processing

capability Embedded expert

system

Multi-levels warning

strategy

Web-based server

application

Data Acquisition System Network for Health Monitoring


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To access real time data, a customizeduser-friendly remote web-based Bridge

Monitoring System (BMS) was developed.

The BMS is a combination of sensor

integration, warning and alarm system,

statistical analysis and expert system.

An automated monitoring system for the

bridge has been deployed since December

2001. The system provides critical

information on strains, displacements,

accelerations and temperature at the key

segments.

A multi-year system maintenance and data

analysis program was considered for the

bridge for identification of an effective retrofit

design.

Bridge Monitoring Software for Kishwaukee Bridge


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QianJiang Bridge, China

A Smart Structures Project

Smart Structures is contracted by the Qianjiang Fourth Bridge Authority (China) toinstall stress and force measurement devices on several cables and hangers. The

objective of this proposal is to provide a practical and proven approach of using E-M

(Elasto-Magnetic) sensors to measure cable and hanger stresses and forces. A total

of 35 sensors are to be installed at several hangers and post-tension cables for 3

spans. This proposal includes some methodologies and details regarding the design,

placement and number of sensors as well as the knowledge of the power supply and

data acquisition system for E-M sensors. It is our intention to design a simple, cost-effective system that is easy to operate and maintain.

Sensors installed on the hangers of the

QianJiang Bridge

The EM sensors were installed on the

Qianjiang Bridge cables during the

construction period.


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ZhanJiang Bridge, ChinaAnother Smart Structures Project

Smart Structures is working in collaboration with the Chinese Railroad Bridge Institute to

design a distributed Intelligent Bridge Monitoring System for ZhanJiang Bay Bridge.

Zhanjiang Bay Bridge is a cable-stayed suspension bridge composed of 3 portions: eastapproach viaduct, main bridge, and west approach viaduct. The Main Bridge has a totallength of 840meter. The monitoring system includes measurement of stress and the strain inthe structure, temperature of the structure; dynamic mode analysis; force in stay-cables;structural space deformation; wind loads; structural loading condition; monitoring theconnection joints of the steel and concrete beams.

The Bridge Monitoring System would

include :

sensor installation and sensor integration

real time data acquisition

Real time data preprocessing and postprocessing

warning/alarm system,

data archiving,

expert system

data interpretation and reporting.


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Innovative Sensors Developed by Smart Structures EM Sensors :

These sensors are capable of measuring the cable force/stress directly and thus provideinformation on the stress state of the bridge.

Wireless SensorsWireless sensors can be customized to measure strain, acceleration, temperature wirelessly inreal-time.

Large Motion Sensors ( Fiber optics, no electrical current input)These Large Motion Sensors, placed at the extremities of the bridge spans, are fiber optic digital encoders thatcan measure several inches of motion with a resolution of 2 thousandths. Placed above and below the NeutralAxis, these sensors will track:

1) Expansion bearing motion as a function of temperature

2) Span rotation arising from deflection due to: Long term degradation Transient traffic loading

3) Vibration frequency and amplitude4) Pier tilt and subsidence

5) Side wind effects

All of these parameters were correlated with the strain gauge and crack opening data for estimating theaccuracy

The marriage of conventional sensors and the innovative sensors developed will result in aholistic picture of structural health


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Magnetoelastic (EM) stress sensors are employed

to monitor stress and corrosion in steel duringbridge health evaluations.

It functions by obtaining magnetic properties from

steel cables and tendons, which can then be used

to interpret the bridge cables state of stress.

EM sensors can be custom made for any size of

cables/strands.

Projects successfully completed

Nanjing Bridge, China Ashida Gawa bridge, Japan South Dakota Bridge Kumagaya Dome, Japan

EM sensor


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Wireless Sensors

Wireless sensors developedby Smart Structures measurestrain, displacement,acceleration and temperaturewirelessly and in real-time.

Wireless sensors reduce thecable installation andmaintenance cost, thusenabling rapid installationand assembly of sensors.

The data is obtainedremotely and analyzedefficiently.

Mother Board

Sensor point

Child BoardMain station

8-CH PVDF

Customized

Board


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New Fiber Optic Sensors

Passive optical encoders No electrical connections

Fiber cable encoders tethers to CPU Designed for 40 year lifetime

Three encoders per span Measure deck rotation Correlate with strain gauges

Instant health change reading Deck sag Vibration frequency changes Expansion bearing anomalies Pier attitude changes

Holistic bridge condition monitor

Global picture of condition Vehicular impact effects Changes due to erosion Earthquake effects

Encoder

Typical Bridge Encoder Layout


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Sensors under Development

Rebar corrosion sensor Retrofitted in borehole

Isolates a sacrificial coupon

Coupon corrosion induces expansion

Analog readout of changes

Visual Fiber optic remote option

Rotten Concrete Sensor Retrofitted in borehole

Isolates fixed pressure penetrometer

Matrix softening allows penetration

Analog readout of changes

Visual

Fiber optic remote option

Indicator Arms

Rebar corrosion sensor

Rotten ConcreteSensor


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Sensors under Development

Threaded Fastener Clamp Load Monitor

First true clamping force monitor Attached to bolt-head Integral with fastener Totally reversible visual readout >90% accurate No torque wrench needed

No turn-of-nut needed

Magnifies bolt-head deflection Bolt-head is cantilever beam Deflection shrinks upper surface Laser-bonded shim magnifies motion

Shim magnifies motion 80X Pointers angled when loose Pointers parallel when correct load Pointers touch when over-tight

Not tightened

Correct load

Over-tightened

Smart Structures Presentation

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