DEVELOPMENT OF A HYBRID BRIDGE EVALUATION SYSTEM by ANDREAS JOHANN FELBER B.A.Sc., The University ofBritish Columbia, 1988 M.A.Sc., The University ofToronto, 1990 A THESIS IN PARTIALFULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OFPHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Department of Civil Engineering We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December 1993 © Andreas Johann Felber, 1993 ____________________________________ In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It. is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. (Signature) Department of /1/?/ The University of British Columbia Vancouver, Canada /93 /2 Date DE-6 (2188) 11 Abstract There is an increasing need to verify analytical dynamic models used for the seismic evaluation of existing bridges. During a retrofit evaluation, analytical models are created to predict the bridge response and damage levels due to seismic loading. These models should be verified so damage levels can be determined more confidently. Currently experimental studies are only occasionally performed on existing structures to verify analytical models because existing testing methods are toocostly, require traffic shutdowns, and do not deliverresults quickly enough for routine use. To overcome these limitations, the hybrid bridge evaluation system (HBES) was developed using ambient vibration techniques to inexpensively and quickly determine the dynamic characteristics ofalargevarietyofstructures. TheHBEScombinesstateoftheartvibrationmeasurementhardware with a series of custom developed programs to expedite ambient vibration studies. In particular, two new functions were developed and implemented as partofthe HBES software to interpret the dataquickly. These functions made itpossible to analyse thedataobtained from ambient vibration measurements in the field. This is a considerable advancement over traditional systems which require several weeks ofdata analysis afterthe field workis completed. Sincepartialexperimental results can be obtained with the HBES while some of the tests are still in progress, the quality of the collectedinformation can be assessed before leaving the site. Afterreturning from the site, the experimental results can be used to verify and tune analytical models. A numberoftestswere conductedaspartofthisthesis whichdemonstrate theHBES’ performance. The study ofthe Shipshaw Bridge data, which was analyzed in one day, demonstrated the unique 111 speed of the system. The study of the Squamish Wharf demonstrated the system’s capability to determine the dynamic characteristics of structures with very small ambient vibrations levels (+1- 0.02 mg). The complete study of the Colquitz River Bridge was used to evaluate the HBES’ components and their integration. This study confirmed the suitability of the hardware and demonstratedthat the integratedprograms were capable ofexpeditiously acquiring, analyzing, and interpreting large amounts of data. The experimentally obtained characteristics of the structure were used to refine the structure’s analytical models. The HBES system can now be used as an effective tool in the seismic evaluation ofbridges. iv Table of Contents Page Abstract ii List ofTables vi List ofFigures viii Nomenclature xvi Acknowledgements xviii Dedication Xix Chapter 1 Introduction 1 1.1 General Problem 1 1.2 Current Research 3 1.3 Objectives and Outline ofthis Thesis 4 1.4 Future Applications 5 Chapter 2 Review of Structural Dynamic Testing Concepts 7 2.1 Theoretical Background on Structural Dynamics 7 2.2 Forced Vibration Testing Methods 16 2.3 Ambient Vibration Testing Methods 21 Chapter 3 Development ofthe Hybrid Bridge Evaluation System 34 3.1 Vibration Measurementson the Second Narrows Bridge 35 3.2 HBES Hardware Description 41 3.3 HBES SoftwareDescription 49 3.4 Software and Hardware Interaction 67 V Chapter4 Application ofthe Hybrid Bridge Evaluation System 71 4.1 Preliminary Verification ofthe HBES Software 71 . 4.2 Study ofthe Shipshaw Bridge Vibration Data 76 4.3 Study ofthe Colquitz River Bridge 87 4.4 Study ofthe Squamish Wharf 149 Chapter 5 Summary of the Features of the Hybrid Bridge evaluation System 156 . . Conclusions 159 List ofReferences 162 Appendix A Measurement Hardware Selection and Specifications 170 . Appendix B Program AVTEST User’s Manual 206 . . Appendix C Program ULTRA User’s Manual 214 . . Appendix D Program VISUAL User’s Manual 255 . . Appendix E Program SUBSAP User’s Manual 265 . . Appendix F Details ofIndividual Test Setups 269 . . . Appendix G Index ofTerms and Abbreviations 276 vi List of Tables Page Table 4.1: AnalyticalDerivedandNumericallyObtained Dynamic Characteristicsof the Three Degree ofFreedom System Example 74 Table 4.2: SensorLocations for Shipshaw Bridge Tests 80 Table 4.3: Experimentally Determined and Analytically Derived Frequencies of the Shipshaw Bridge 84 Table 4.4: Key Element Properties for the Base Model ofthe Colquitz River Bridge 91 Table 4.5: Experimentally Determined Modal Frequencies of the Colquitz River Bridge 100 Table 4.6: Damping Estimates from the First Ten Cycles ofthe Transverse Pullback Test ofthe Colquitz River Bridge 113 Table 4.7: DampingEstimatesfromtheFirstTenCyclesoftheLongitudinalPullback Test ofthe Colquitz River Bridge 117 Table 4.8: Effective Moments of Inertia of Beam Elements for the Colquitz River Bridge Model 127 Table 4.9: Experimentally Determined and Analytically Derived Frequencies of the Colquitz River Bridge 140 Table 4.10: DifferenceBetweenExperimentallyDeterminedandAnalyticallyDerived Frequencies ofthe Colquitz River Bridge 141 vii Table 4.11: Experimentally Determined Frequencies of the Squamish Wharf 152 . Table A.1: AmplificationLevels of the Kinemetrics Signal Conditioner 186 Table A.2: Configuration ofHardware Components forHardware Test 202 Table F.1: Sensor Locations for Vertical Ambient Vibration Survey at the Colquitz River Bridge 270 Table F.2: SensorLocationsforTransverseAmbientVibration SurveyattheColquitz River Bridge 271 Table P.3: Sensor Locations for Longitudinal Ambient Vibration Survey at the Colquitz River Bridge 272 Table F.4: Sensor Locations for Transverse Pullback Tests at the Colquitz River Bridge 273 Table F.5: Sensor Locations for Longitudinal Pullback Tests at the Colquitz River Bridge 273 Table F.6: Sensor Locations for Ambient Vibration Tests at the Squamish Wharf 275 viii List of Figures Page Fig. 2.1 Idealized Single Degree ofFreedom Model 8 Fig. 2.2 Absolute Value and Phase Angle of The Dimensionless Frequency Response Function 12 Fig. 2.3 Three Degree ofFreedomExample 13 Fig. 2.4 Mode Shapes and Natural Frequencies of the Three Degree of Freedom Example 16 Fig. 2.5 Acceleration Response of a Undamped SDOF System to Initial Displacements 20 Fig. 2.6 RoofAccelerationResponseofaThreeDegreeofFreedomSystemSubject to White Noise Excitation 25 Fig. 2.7 Acceleration PSD of Top Mass of Three DOF System Subject to White Noise Excitation 26 Fig. 3.1: View ofthe Second Narrows Bridge 37 Fig. 3.2: Elevation View of the Second Narrows Bridge 37 Fig. 3.3: Typical Recording Setup for Ambient Vibration Measurements 42 Fig. 3.4: HBES Sensor Attached to a Steel Beam 43 Fig. 3.5: Ambient Vibration Measurement Hardware 43 Fig. 3.6: Quick Release Mechanism 48 ix Fig. 3.7: Typical Release Force Time History of the QRM Developed at UBC 49 . Fig. 3.8: Schematic ofData Reduction with ULTRA 52 Fig. 3.9: Transfer Function of Sample Data 56 Fig. 3.10: Phase Angle of SampleData 57 Fig. 3.11: Phase Window Function Corresponding to Sample Data 57 Fig. 3.12: Coherence Function ofSample Data 58 Fig. 3.13: Coherence Window Function Corresponding to Sample Data 58 Fig. 3.14: Potential Modal Ratio Function ofSample Data 59 Fig. 3.15: Schematic ofData Interpretation with Visual 62 Fig. 3.16: Relationship Between the Series, Signal, and Spectra Classes 66 Fig. 3.17: Interaction of AVTEST, ULTRA, VISUAL, and the Measurement Hardware 68 Fig. 3.18: Interaction ofSUBSAP and SAP9O 70 Fig. 4.1: ANPSD for the Three Degree ofFreedom System Example 73 Fig. 4.2: View ofthe Shipshaw Bridge 77 Fig. 4.3: Sensor Locations for the Shipshaw Bridge 80 Fig. 4.4: Acceleration RecordforSensorNo.6Duringthe5thTestofthe Shipshaw Bridge 81 Fig. 4.5: AccelerationRecordforSensorNo.3Duringthe2ndTestofthe Shipshaw Bridge 81