Structural Health Monitoring System

for Bridges

COMPUTER ENGINEERING SENIOR PROJECT – Semester 2 , Spring 2011

Ralph Kliza

April 29, 2011

AGENDA

Background

Project Motive

Project Scope

Design Process

System Architecture and Components

Conclusion

Background: I-35W Bridge Collapse,

August 1, 2007

Background:NTSB Report Findings

Visual Inspections alone are inadequate

Inspections failed to give attention to gussets

Failure of tracking and documentation of structural component conditions

Gusset plates not used in computer modeling

Improperly designed gusset plates

Background: Texas Bridges

Over 50,000 bridges in Texas, July 2008

Steel Truss same as Minnesota: 6

1,871 bridges rated as “structurally deficient”, July 2008

$330 million spent on replacing, widening, rehabilitation and maintenance of Texas bridges, August 2007 – August 2008.

Project Motive

Paradigm Shift in Civil Structures

Prevent Catastrophic Structural Failures

Adaptability to Other Civil Structures

Aid in Evaluation / Inspection of Structurally Deficient Bridges

H.R. 3999 “Highway Bridge Reconstruction and Inspection Act”, July 2008

Project Scope:

Hardware

- Strain Gauge Circuit

- Traffic Counter Circuit

- Rechargeable Power System

- Imote2 to PC Interface

Software

- GUI

- Database

- Data Analysis

- PC Interface

Design Process[4]

Hardware Design- Architecture- Synthesis- Compiler

Software Design- Application- Operating System- compiler

RequirementsAnalysis

Specifications

System Architecture

Interface Design- Software Drivers- Hardware Drivers

Integration AndTest

Requirements:Requirements Gathering

I-35 W Bridge Collapse NTSB Report

International Society of Structural Health Monitoring, www.ishmii.org

Academic Research / Papers

Senior Project Scope

Requirements:User Requirements[2]

Quantify the overall integrity of the structure over a given period of time.

Historical metrics will augment the regular inspection cycle of the structure.

Quantify the integrity of critical structural elements.

Detect changes in structure geometry after completion and over the life of the structure, due to repetitive large live loads or dead loads or other unusual loads.

Monitor the integrity of the structure using nondestructive evaluation technologies.

System Specifications[1]

data acquisition subsystem

maximum sampling rate 500 Hz to 1–2 kHz

channels 4–8 simultaneously

resolution at least 16 bits

computational core

data storage: 256 KB

program memory: 256 KB

processing capabilities engineering analyses

wireless communication channel

radio band unregulated ISM bands

open-space range over 200 m

Data rate at least 20 kbps

System Architecture:Crossbow Imote2

Sensors & DAQ

Analog to Digital Conversion

Computational Core

Wireless Communication

Data Management / Analysis

User Interface / Software

ITS400 BASIC SENSOR BOARD

SENSOR ARRAY

IPR2400 PROCESSOR / RADIO BOARD

INTERFACEADC, SPI, UART

System Architecture:Sensors & Data Acquisition Sensors Onboard (ITS400 Basic Sensor Board)

- Temperature (ITS400)

- Humidity (ITS400)

- Accelerometer (ITS400)

- Light (ITS400)

Additional Sensors

- Signal Conditioner / Strain Gages (Implemented)

- Traffic Counter

- System Power Supply

System Architecture:Signal Conditioner

Measuring Circuit Selection Criteria

1. Cost

2. Portability

3. Reliability

General Design

1. Wheatstone Bridge

2. In-Amp

- AD623 & AD8223

SIGNAL CONDITIONER

STRAIN GAUGE

SIGNAL AMPLIFIER

MEASURINGCIRCUIT

IMOTE2INTFC

IMOTE2POWER

System Architecture:AD8223 IN-AMP

System Architecture:ADC, Computation & Wireless

- Imote2 Sensor Board (ITS400)Analog-to-Digital Conversion (ITS400)- Maxim MAX1363 12 bit / 4 Channel

System Architecture:ADC, Computation & Wireless

- Imote2 Processor Radio Board (IPR2400)Computational Core used for Data Analysis

- Intel Xscale Processor PXA271 - 13 – 416 MHz

Preliminary Data Management - 256 kB SRAM / 32 MB Flash 32 MB SDRAM

Wireless Communication - Wireless MMX Coprocessor TI CC2420 - 802.15.4 radio / 2.4 GHz - 250 kb/s

System Architecture:User Interface / Software

Data Management / Analysis - Imote2 Builder Kit

Visual Studio 2005 - .NET & C# Several Manufacturer Namespaces

- Serial Dump - Data Base

GUI / User Interface - Data Analysis Display

- Network Information

System Architecture:Serial Dump

Sensor packet format:byte field0 board_id1 packet_id2-3 node_id4-5 count6-7 accel_x8-9 accel_y10-11 accel_z12-13 temperature1 ; from TI sensor14-15 temperature2 ; from sensirion sensor16-17 humidity18-19 light20-21 adc022-23 adc124-25 adc226-27 adc3

System Architecture:Serial Dump

Software Interface:GUI

Signal Conditioner Test:Prototype Circuit

Conclusion:SPRING 2011

Many Design Considerations

Future Design Considerations

GRADUATION!

QUESTIONS?

References:1. Lynch, Jerome Peter, “An overview of wireless

structural health monitoring for civil structures”, Philosophical Transactions of the Royal A Society, 14 Dec 2006

2. “Collapse of I-35W Highway Bridge, Minneapolis, Minnesota, August 1, 2007”, Accident Report NTSB HAR-08/03 PB2008-916203.

3. “Imote2 Hardware Reference Manual”, Rev. A, September 2007, Crossbow Technology, Inc..

4. Ford, Ralph M., Coulston, Chris S., “Design for Electrical and Computer Engineers: Theory, Concepts and Practice”, McGraw-Hill Companies, Inc., New York, NY, 2008.