Capacity Evaluation of Older Bridges

1. Capacity Evaluation of Older Bridges By: Afshin Esfandiari Capacity Evaluation of Older Bridges by Afshin Esfandiari

2. Outline • Introduction • Required Data for Bridge Evaluation • Static and Dynamic Load Testing • Reliability Theory for Bridge Evaluation • Code Approach • Effect of type of Analysis • Conclusions Capacity Evaluation of Older Bridges by Afshin Esfandiari

3. Why do we evaluate older bridges? Defects Deterioration or Damage Change in the Design or Load evaluating Specification Application for a Permit to Allow Controlled Vehicle Unsatisfactory Serviceability or Fatigue Performance Introduction Capacity Evaluation of Older Bridges by Afshin Esfandiari

4. Actual strength of material Cracking, spalling, delamination or yielding Corrosion of structural steel, reinforcement or prestressing tendons Actual minimum areas of the structural members, location of reinforcement and bridge geometry Settlement, deformation or rotation producing redistribution of stress Changes of redistribution of permanent stresses due to prestressing or dead load Effectiveness of bolted joints and bonded components Life of any fatigue prone details Restraints at joints and bearings Required Data For Bridge Evaluation Capacity Evaluation of Older Bridges by Afshin Esfandiari

5. Concrete Tests Strength Method Sonic Method Ultrasonic Method Magnetic Test Electrical Method Thermography Radar Radiography Endoscope Steel Tests Radiography Magnetic Particle and Eddy Currents Examination Dye Penetration Method Ultrasonic Examination Nondestructive Tests Capacity Evaluation of Older Bridges by Afshin Esfandiari

6. Destructive Tests Standard ASTM and AASHTO test methods for material sampling Capacity Evaluation of Older Bridges by Afshin Esfandiari

7. Destructive Tests (Cont.) Standard ASTM and AASHTO methods for concrete used in laboratory Capacity Evaluation of Older Bridges by Afshin Esfandiari

8. Destructive Tests (Cont.) Standard ASTM and AASHTO methods for structural steel used in laboratory Capacity Evaluation of Older Bridges by Afshin Esfandiari

9. Static Full Scale Loading Test • Test Procedure • Theoretical analysis • Load application at the critical locations in steps • Measurement of deflections after loading and unloading of each load step • Comparison of the actual and the theoretical load-deflection curve • Determination of bridge capacity by correlating analytical and experimental results Capacity Evaluation of Older Bridges by Afshin Esfandiari

10. Natural Frequencies and Mode Shapes Modal Assurance Criteria Mode Shape Area Flexibility Matrix Sensitivity Based Model Updating Method Direct Stiffness Calculation (DSC) Method Vibration Based Damage IdentificationMethods (VDIM) Capacity Evaluation of Older Bridges by Afshin Esfandiari

11. Review of a Comprehensive Research in VDIMs • Research Description • A bridge was artificially damaged • Existing methods of damage identification were studied and compared • Bridge Name and Location • Romeo Bridge located close to Lucerne in Switzerland • Reference • Damage Identification Using Modal Data • By Huth et al. • Journal of structural engineering December 2005 Top view Cross section Capacity Evaluation of Older Bridges by Afshin Esfandiari

12. Review of a Comprehensive Research in VDIMs (cont.) Summary of the performed tests on the Romeo Bridge Capacity Evaluation of Older Bridges by Afshin Esfandiari

13. Review of a Comprehensive Research in VDIM Methods (cont.) Natural frequencies in HZ throughout the second damage scenario Shapes of identified mode shapes Capacity Evaluation of Older Bridges by Afshin Esfandiari

14. Review of a Comprehensive Research in VDIM Methods (cont.) Shapes of identified mode shapes by finite element analysis Shapes of identified mode shapes by test results Capacity Evaluation of Older Bridges by Afshin Esfandiari

15. Review of a Comprehensive Research in VDIM Methods (cont.) Damage effects on modal assurance criterion (MAC ) Relative changes of mode shapes areas with respect to Test 5 Capacity Evaluation of Older Bridges by Afshin Esfandiari

16. Review of a Comprehensive Research in VDIM Methods (cont.) Changes of the flexibility matrix with respect to Test 5 Changes of bending stiffness EI computed with DSC method using Bending Mode B2 Capacity Evaluation of Older Bridges by Afshin Esfandiari

17. Reliability Theory for Bridge Evaluation Failure probability model Failure probability and safety index (Safety Index) Probability of Failure Capacity Evaluation of Older Bridges by Afshin Esfandiari

18. Code Approach for Live Load Evaluation • Permit Vehicle Loads • PA: annual basis permit for a specific period to carry indivisible load along with other traffic without supervision • PB: bulk haul, divisible load traffic by permit for many trips mixed with normal traffic • PC: indivisible load authorized by permit under supervision and specified travel condition • PS:indivisible load authorized by permit for a single trip mixed with other traffic without supervision. • Normal Traffic Loads • EP1: a bridge is required to carry vehicle trains within the normal traffic without restriction • EP2: a bridge is required to carry two unit vehicles (load restriction is applied) • EP3: a bridge is required to carry single unit vehicles (load restriction is applied) Capacity Evaluation of Older Bridges by Afshin Esfandiari

19. Code Approach for Live Load Evaluation • System behaviour category • S1: element failure leads to the failure of the structure • S2: element failure do not lead to total collapse • S3: element failure lead to local failure only • Element behaviour category • E1: element is subject to sudden failure with little or no warning • E2: element is subject to sudden failure with little or no warning but retain post-failure capacity • E3: element is subject to gradual failure with warning of probable failure Capacity Evaluation of Older Bridges by Afshin Esfandiari

20. Code Approach for Live Load Evaluation • Evaluation Procedure • target reliability factor shall be obtained from relevant tables • load factors shall be obtained from the relevant tables • live load capacity factor shall be obtained from: • Inspection Level • INSP1: component is not inspectable • INSP2: component is inspected and results are available for the evaluator • INSP3: component is fully inspected by the evaluator Capacity Evaluation of Older Bridges by Afshin Esfandiari

21. Review of a Finite Element Study on Redistribution of Moments Longitudinal moment diagram of a two span bridge Distribution parameters a two span bridge with increasing the load Reference: Esfandiari, Masters Thesis, Carleton University, November 2001 Capacity Evaluation of Older Bridges by Afshin Esfandiari

22. Conclusions • In the absence of drawings and documents nondestructive and destructive tests may be required to collect the necessary data. • Static full scale loading is capable of predicting the ultimate capacity of a bridge as a whole, but can not locate or identify the damages. • Damage identification methods using modal data can be a good tool to localize and identify damages in bridges. However, there is still ambiguity in the existing methods. • Code approach to evaluate bridges is based on reliability theory and considers the probability of variation in the material strength due to uncertainties. • Code does not specify how to locate damages or how to include the effect of damages in the bridge evaluation. • Nonlinear behaviour of bridges is important and needs to be considered in evaluation of bridges. Capacity Evaluation of Older Bridges by Afshin Esfandiari

23. Thank You Capacity Evaluation of Older Bridges by Afshin Esfandiari