An Innovative Procedure for Load Rating of Suspension Bridges

Transcription

1 An Innvative Prcedure fr Lad Rating f Suspensin Bridges Hassan Sedarat Iman Talebinejad Alexander Kzak Jyce Lee, Farid Nbari, Alex Krimtat SC Slutins, Sunnyvale Califrnia 1

2 Outline Outline: Bridges in the United States: Status and Cnditin Need fr Lad Rating f Bridges Prpsed Prcedure fr Lad Rating fr Cmplex Bridges 2

3 Cllapse f Silver Bridge (1967) Ohi River First majr bridge cllapse since Tacma Narrws Bridge cllapsed n Nvember 7, killed 9 injured Stress crrsin cracking in the eyebar The bridge was carrying much heavier lads than riginally designed fr Prly maintained Cngressinal Actin Establishment f the Natinal Bridge Inspectin Standards (NBIS) Status/Cnditin U.S Silver Bridge (between Pint Pleasant, West Virginia, and Kanauga, Ohi) 3

4 Status/Cnditin The average age f the natin s 607,380 bridges is currently 42 years The natin has an entire generatin f bridges, cnstructed in the 1950s and 1960s, that need majr repair r replacement Per 2013 ASCE Reprt Card fr America s Infrastructure : Over 250 millin daily crssings n 63,207 U.S. structurally deficient bridges in need f repair Per FHWA Estimate: The current cst t repair r replace nly the deficient bridges: $76 billin Surce: All data is frm the 2013 Natinal Bridge Inventry, released in march 2013 by the Federal Highway Administratin. Number includes all bridges classified as structurally deficient withut taking int cnsideratin the year a bridge was build r recnstructed. 4

5 NBIS Mandates Current Management Strategies: Bi-annual inspectin and lad rating Federal regulatins requirements fr inspectin prcedures Preparatin and maintenance f bridge inventry recrds Visual Inspectin Methds Nn-destructive Evaluatin Methds (NDE) Structural Mnitring Methd (SM) Lad Rating Management Strategies 5

6 Lad Rating Lad Rating AASHTO Prvides General Guidance fr Simple Bridges Cmplex Bridges? Need fr an Efficient Prcedure fr Cmplex Bridges 1. T address the demand calculatins calculatin f dead lad live lad r unknwn verweight vehicles distributin factr increase in traffic vlume impact lad speed at which the vehicles travel 2. T address the capacity calculatins Cnstructin deficiencies Aging f material Prpsed Prcedure: Cmbine Structural Mnitring with Lad Rating 6

7 Prpsed Prcedure Steps 1 and 2: Finite Element Analysis Flexibility Analysis This is a ne-time effrt Step 3: Measure displacement f bridge using wireless accelermeters Measurement in real-time Step 4: Estimate the respnse f the bridge in real-time (withut perfrming finite element analysis) Step 5: Calculate the C/D rati f the estimated respnse fr any desired bridge cmpnent Or Cmpare with Baseline Cnditin A Unique prcedure Reliable tl fr lad rating and cntinuus mnitring f the bridge 7

8 Implementatin The New Carquinez Bridge (Alfred Zampa Memrial Bridge) Opened t traffic n Nvember 11, 2003 Superstructure: steel bx girders 8

9 Implementatin Steps 1 and 2: Finite Element Analysis Flexibility Analysis This is a ne-time effrt Step 3: Measure displacement f bridge using wireless accelermeters Measurement in real-time Step 4: Estimate the respnse f the bridge in real-time (withut perfrming finite element analysis) Step 5: Calculate the C/D rati f the estimated respnse fr any desired bridge cmpnent Or Cmpare with Baseline Cnditin 9

10 Step 1 : Develp FE Mdel FE mdel f the New Carquinez Bridge FE mdel: ndes, elements and 159,195 DOFs Cnstructin sequence was simulated All the bridge cmpnents were mdeled in detail 10

11 Measured and Cmputed Frequencies Mdel Calibratin Validatin f the FE mdel Excellent agreement between measured and un-calibrated frequencies N significant imprvement after FE mdel calibratin Mde number Measured Frequencies FE Frequencies (uncalibrated) FE Frequencies (calibrated) % difference (measured and uncalibrated) % difference (measured and calibrated) Accelermeters and 4 Strain gauges were installed n the bridge 11

12 Validatin f the FE Mdel Installatin f Temprary Sensr n Suspenders f the New Carquinez Bridge by Caltrans Maintenance Crew 12

13 Validatin f the FE Mdel Frces in the hangers: Measured and cmputed Errr n ttal measured lad = 3% 13

14 Step 2 : Develp Flexibility Analysis 14

15 Implementatin Steps 1 and 2: Finite Element Analysis Flexibility Analysis This is a ne-time effrt Step 3: Measure displacement f bridge using wireless accelermeters Measurement in real-time Step 4: Estimate the respnse f the bridge in real-time (withut perfrming finite element analysis) Step 5: Calculate the C/D rati f the estimated respnse fr any desired bridge cmpnent Or Cmpare with Baseline Cnditin 15

16 Step 3: Measure Displacement f Bridge Bridge displacements are measured thrugh frces in the hangers Install sensrs t selected number f hangers Lcatin f sensrs n the hangers 16

17 Implementatin Steps 1 and 2: Finite Element Analysis Flexibility Analysis This is a ne-time effrt Step 3: Measure displacement f bridge using wireless accelermeters Measurement in real-time Step 4: Estimate the respnse f the bridge in real-time (withut perfrming finite element analysis) Step 5: Calculate the C/D rati f the estimated respnse fr any desired bridge cmpnent Or Cmpare with Baseline Cnditin 17

18 Results (Lad at apprach span) Step 4: Estimate Respnse in Real-Time 18

19 Step 4: Estimate Respnse in Real-Time Results (Lad at main span) 19

20 Results (Lad at three lcatins) Step 4: Estimate Respnse in Real-Time 20

21 Results (Lad at five lcatins) Step 4: Estimate Respnse in Real-Time 21

22 Step 4: Estimate Respnse in Real-Time Cable frces due t traffic lad - estimated versus actual 22

23 Step 5: Lad Rating Steps 1 and 2: Finite Element Analysis Flexibility Analysis This is a ne-time effrt Step 3: Measure displacement f bridge using wireless accelermeters Measurement in real-time Step 4: Estimate the respnse f the bridge in real-time (withut perfrming finite element analysis) Step 5: Calculate the C/D rati f the estimated respnse fr any desired bridge cmpnent Or Cmpare with Baseline Cnditin 23

24 Step 5: Lad Rating Baseline Cnditin: Displacements due t Pre-determined lading (e.g. HL-93) One-time effrt (will nt be repeated) Lad Rating Displacements due t Pre-determined Designed Traffic Lad Hanger frces based n prcessed measurement (bi-annual) Hanger frces based n prcessed measurement in real-time Cmpnent-specific Lad (Demand) Estimatr Finite Element Analysis Flexibility Analysis Updated, if needed, based n bi-annual assessment Cmpnent-specific Lad (Demand) Estimatr Baseline Cnditin State f stresses & strains database Estimated state f stresses & strains database Cmpare with baseline Baseline Capacity Database Real-time Autmatic reprt generatin Lad Rating 24

25 Cnclusins Cnclusins The prpsed prcedure estimates demands in real-time withut perfrming FE analysis Demands (frces and displacements) can be estimated with very gd accuracy fr: Dead Lad & Live Lad Defined Vehicle Lads (knwn lad) Traffic Lads (unknwn lad) Unknwn Overweight Vehicles Increase in Traffic Vlume Speed f Vehicles Temperature Effect 25

26 Cnclusins Cnclusins Distributin Factr and Impact Factr are autmatically included in demand calculatins Cnstructin deficiencies are autmatically included in demand calculatins Capacity updates This technique can be used fr lad rating f cmplex bridges 26

27 Thank Yu 27