Ice-Structure Interaction at the Confederation Bridge Pier Dhruba - PowerPoint PPT Presentation

Ice-Structure Interaction at the Confederation Bridge Pier Dhruba Tripathi Department of Civil Engineering, University of Calgary Calgary, Canada

Overview  Confederation Bridge Introduction  Monitoring – Direct, indirect, and observations  Pressure panels  Data analysis  Activation Analysis  Detailed Pressure Distribution Analysis  Correlation Analysis  Conclusion 5/18/2010 Tripathi 2

Confederation Bridge 5/18/2010 Tripathi 3

Confederation Bridge  12.9 km long  100 years design life  40 m above water (typical)  4.5m to14m deep precast concrete box girder  Bridge Footings- Gravity foundation on bedrock 5/18/2010 Tripathi 4

Ice Force Monitoring  Direct measurement of ice pressure  Indirect measurement of the global ice force  Observation of ice kinematics 5/18/2010 Tripathi 5

Indirect measurement of ice force  Tilt meters measure displacements  Stiffness of the pier determined by a pull test 5/18/2010 Tripathi 6

Ice load on the Bridge  Limit stress (ice failure)  Vertical structures – Crushing failure of ice  Conical ice shield – flexural failure – causes lower load  Limit force (ice driving force) 5/18/2010 Tripathi 7

Ice Load History 5/18/2010 Tripathi 8

Real-Time Monitoring  Computers at the bridge can be accessed through internet  Ice load – live chart at website updated every 15 minutes (http://ice.ucalgary.ca)  Real-time access - videos from four cameras for the observation of ice-structure interaction 5/18/2010 Tripathi 9

Direct measurement of ice pressure 20 panels Covering 40m 2 5/18/2010 Tripathi 10

Ice Force Panels (IFPs) 1 10 2 9 3 8  A total of 160 4 5 6 7 sectors in 20 11 20 12 19 13 18 14 17 panels on the 15 16 cone 5/18/2010 Tripathi 11

Typical Panel  8 sectors (~500 x 500 mm)  ~ 30 button on each sector  2 buttons instrumented  Best represents average pressure 5/18/2010 Tripathi 12

Data  120 channels – upper cone (level ice and rubble)  40 channels – lower cone (Thick ice)  64 channels – pier shaft (Large keels)  Tiltmeter data – Global ice force (comparison)  4 time-lapse video data, upward-looking sonar 5/18/2010 Tripathi 13

Ice Structure Interaction What happens at the ice structure interface? Pressure zones ( hpz ) ICE ? STRUCTURE Spatial and temporal pressure distribution ? 5/18/2010 Tripathi 14

Data  Electrical signals  Average data- every 17 seconds  Full Ice season – continuous recording  Triggered data- every 34 milliseconds  For Events only 5/18/2010 Tripathi 15

Typical data header (120 data channels) 5/18/2010 Tripathi 16

Panel Reliability 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120  4 panels and 10 sectors  42 sectors bad in 1998  7 panels and 16 sectors  72 sectors bad in 2003 5/18/2010 Tripathi 17

Events selection and Panels  Events selection  Ice forces – (tiltmeter data)  Availability of pressure panel data  Video analysis, when available  Panels  Panels on cone for interaction of level ice  Waterline panels – level ice impact  Panels above water-line – Rubble piles 5/18/2010 Tripathi 18

Data Conversion 93 94 89 90 113 114 109 110 2.5 LEGEND 2 89 90 93 94 Pressure, y ip (MPa) 109 110 113 114 1.5 1 0.5 0 -0.5 -1 09:04.3 09:13.0 09:21.6 09:30.2 09:38.9 09:47.5 09:56.2 10:04.8 Time stamp (min.) 5/18/2010 Tripathi 19

Baseline  Unrealistic negative pressure  Baselines differ in different channels  Clear pressure peaks (sustained pressure for longer duration – very rare)  Baselines changed over time 5/18/2010 Tripathi 20

Baseline Correction- Trimmed 5/18/2010 Tripathi 21

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Ice pressure and ice force 5/18/2010 Tripathi 25

Data Analysis Activation Analysis  Sector considered active  [pressure peak] > [a threshold] Detailed Pressure Distribution Analysis  Peaks – supported by at least 5 adjacent peaks in each side 5/18/2010 Tripathi 26

Horizontal and vertical pressure distribution 93 94 89 90 113 114 109 110 5/18/2010 Tripathi 28

Activation, Integrated load 5 0.6 Integrated load =∑[ y i a i cos( α i )] 0.5 4 Panel Activation (No.) Integrated Load (MN) 0.4 3 0.3 2 0.2 1 0.1 0 0 09:09.3 09:11.9 09:14.4 09:17.0 09:19.6 09:22.2 09:24.8 09:27.4 09:30.0 09:32.5 09:35.1 09:37.7 09:40.3 09:42.9 09:45.5 09:48.0 09:50.6 09:53.2 89 90 93 94 109 110 113 114 Panel Activation Integrated Load 5/18/2010 Tripathi 29

Horizontal Pressure Distribution 5/18/2010 Tripathi 30

Horizontal Distribution 5/18/2010 Tripathi 31

Vertical pressure distribution 5/18/2010 Tripathi 32

Detailed Pressure Distribution Analysis 2 2 Sector 90 Sector 89 Sector Pressure (MPa) Sector Pressure (MPa) 1 1 0 0 -1 -1 -2 -2 12:09 12:09 Time (HH:MM) Time (HH:MM) 2 2 Sector 93 Sector 94 Sector Pressure (MPa) Sector Pressure (MPa) 1 1 0 0 -1 -1 -2 -2 12:09 12:09 Time (HH:MM) Time (HH:MM) 89 90 93 94 109 110 113 114 5/18/2010 Tripathi 33

Probability of exceedance 5/18/2010 Tripathi 34

Correlation Analysis • Strength and direction of a linear relationship of pressure between different sectors • Activation correlation • Time-series corrleation 5/18/2010 Tripathi 35

Time-series correleation 1 81 0.8 Correlation Coefficient 82 0.6 83 0.4 84 0.2 85 0 86 -0.2 89 -0.4 90 81 90 82 89 83 86 s 84 85 r o t c 85 84 e S 86 83 89 82 90 81 5/18/2010 Tripathi 36

Limitations  Pressure panels readings - representation of absolute pressure  Many of the sectors were damaged  Availability of video data at night (apparently, the largest events occur at night) 5/18/2010 Tripathi 37

Further works  Test the results by using numerical methods like finite element method.  Process limit driving force events  Add some more events to refine the result. 5/18/2010 Tripathi 38

Acknowledgements Dr. Tom Brown Noorma Shrestha Susan Tibbo Kelly Obert Mohamed El-Seify Derek Myane Dambar Tiwari May 29, 2009 39

Thank You ! Questions ?