Modellering av restlevetid og kapasitet til spennarmerte brukonstruksjoner med korrosjon- Case Hulvågbrua

Transcription

1 Modellering av restlevetid og kapasitet til spennarmerte brukonstruksjoner med korrosjon- Case Hulvågbrua Magdalena Paciorek, PhD Candidate SUPERVISORS: Gro Markeset, Professor HIOA Terje Kanstad, Professor NTNU Max Hendriks, Professor NTNU Mahdi Kioumarsi, Associate Professor HIOA

2 PRESTRESSED, PRETENSIONED BRIDGES IN NORWAY >1100 precast, pretensioned beam bridges (NIB/NOT/NOB/other) Ref. : Bruprosjektering-08, NIB-bruer: Håndbok -100, Statens Vegvesen PRECAST, PRETENSIONED BEAM BRIDGES IN NORWAY 40,2 % 59,8 % NIB beam Other types Hafrsfjord, Photo Magda Paciorek

3 PRESTRESSED, PRETENSIONED BRIDGES IN NORWAY Ref. : most-dangerous-road-in-world-terrifying-awe-inspiring/ c 35mm > 190 bridges

4 EFFECT OF CORROSION SMALL φ OF WIRE HIGH TENSILE STRESSES + PITTING CORROSION WIRE BREAK (non-ductile) STRESS CORROSION CRACKING WIRE BREAK (brittle) Hafrsfjord, Photo Magda Paciorek Hafrsfjord, Photo Statens Vegvesen

5 EFFECT OF CORROSION - Cracking - Spalling Hafrsfjordbru, Stavanger

6 EFFECT OF CORROSION WIRE BREAK PROGRESSIVE BREAKING OF WIRES STRAND BREAKING = 7 x Stress REDUCED PRESTRESS REDUCED FLEXURAL STRENGHT Non-corroded strand Corroded strand Strain Ref. : Fumin Li et.al.: Deterioration of tensile behaviour of steel strands corroded by chloride, Journal of Southeast University (Natural Science Edition)

7 EFFECT OF CORROSION ON MECHANICAL BEHAVIOUR OF STRANDS Non-corroded strand (reference) Corroded strand with varying loss of cross- section 0.8%-20.4% Ref. : Zhao-Hui Lu et.al.: An Investigation of Degradation of Mechanical Behaviour of Prestressing Strands Subjected to Chloride Attacking, 5th International Conference on Durability of Concrete Structures, Jun 30 Jul 1, 2016, Shenzhen University, Shenzhen, Guangdong Province, P.R.China

8 EVALUATION OF MAXIMUM MOMENT FOR BREAKING FIRST LAYER OF STRANDS Pm = 29% Pm.o

9 EVALUATION OF MAXIMUM MOMENT FOR BREAKING FIRST LAYER OF STRANDS ASSUMPTION I Only loss of the cross-section of bottom layer: ASSUMPTION II Change in mechanical behaviour of bottom layer: A0 - non-corroded A1 = 3.1% A0 A2 = 6.3% A0 A3 = 12.9% A0 A4 = 16.3% A0 A5 = 19.8% A0 fy=1650mpa fu=1950mpa fy=1700mpa fu=1900mpa Hulvågbrua

10 EVALUATION OF MAXIMUM MOMENT FOR BREAKING FIRST LAYER OF STRANDS Influence of corrosion level on max. moment of breaking bottom layer of strands M corroded/uncorroded % 105,0% 100,0% 95,0% 90,0% 85,0% 80,0% Failure due to crushing of concrete Failure due to breaking of strands Failure due to crushing of concrete 75,0% 0,0% 5,0% 10,0% 15,0% 20,0% 25,0% Loss of cross-section of bottom layer of strands due to corrosion % 17% ASSUMPTION II ASSUMPTION I BREAKING OF ONE LAYER OF STRANDS CAUSE PROGRESSIVE BREAKING OF REMAINING LAYERS OF STRANDS

11 INFLUENCE OF CORROSION ON FLEXURAL BEHAVIOUR OF PRETENSIONED NIB BEAMS - MORE DETAILED ANALYSES NECESSARY TO EVALUATE CHANGES IN LOAD BEARING CAPACITY AND DUCTILITY OF THE BEAM DUE TO PROGRESSIVE BREAKING OF THE STRANDS (LAYERS) - PROGRESSIVE BREAKING OF THE STRANDS (STRAND LAYERS) WILL DEPEND ON CORROSION LEVEL IN REMAINING LAYERS - NO AVAILABLE EXPERIMENTAL ANALYSES ON CORRODED MULTILAYERED PRETENSIONED SPECIMENS - FLEXURAL BEHAVIOUR OF THE NIB-BEAM DEPENDS ON STRANDS ARRANGEMENT - FLEXURAL BEHAVIOUR OF THE BEAM DEPENDS ON MECHANICAL BEHAVIOUR OF THE STRANDS (BOTH CORRODED AND NON-CORRODED)

12 INFLUENCE OF CHLORIDE INGRESS ON CORROSION Strands in corners the most heavily corroded

13 INFLUENCE OF CORROSION ON FLEXURAL BEHAVIOUR OF PRETENSIONED NIB BEAMS Average for whole layer Average for whole layer

14 INFLUENCE OF CORROSION ON FLEXURAL BEHAVIOUR OF PRETENSIONED NIB BEAMS Corrosion on the connection beam-plate When connection beamplate is lost due to corrosion FLEXURAL CAPACITY?

15 INFLUENCE OF CORROSION ON FLEXURAL BEHAVIOUR OF PRETENSIONED NIB BEAMS FLEXURAL FAILURE SHEAR FAILURE

16 SUMMARY AND FURTHER RESEARCH >190 precast, pretensioned bridges in Norway, which might already corrode In some of the bridges visual signs of corrosion were already found, while in some no signs of corrosion were found Pitting corrosion of the strands lead to changes not only in crosssection, but also in mechanical behaviour of the strands (including effect of SCC) When evaluating performance of corroded NIB beam, assumption of decreasing only the cross-section of strand layer can lead to overestimated breaking load (for relevant layer). In reality strand layer will break for lower load value, with different failure mode and much faster than assumed.

17 SUMMARY AND FURTHER RESEARCH Flexural response of the NIB beam signifficantly depends on the mechanical behaviour of corroded and uncorroded strands made of relevant type of steel used in considered bridges. POSSIBILITIES OF TENSILE TEST OF THE STRANDS? Breaking of one layer of strands cause progressive breaking of remaining layers of strands. Progressive breaking of remaining layers will depend on their corrosion level and arrangement of the strands. MORE RESEARCH NEEDED ON PROGRESSIVE BREAKING OF THE CORRODED STRAND LAYERS AS WELL AS ON THE INFLUENCE OF STRAND ARRANGEMENT. No experimental data available for flexural response of multilayered corroded pretensioned beams FUTURE POSSIBILITIES FOR BENDING TEST OF THE CORRODED NIB BEAM?

18 SUMMARY AND FURTHER RESEARCH RESEARCH NEEDED INCLUDING EFFECT OF MORE RELIABLE CORROSION DISTRIBUTION IN CROSS-SECTION POSSIBLE EFFECT OF STRESS REDISTRIBUTION AFTER BREAKING OF THE STRAND. POSSIBILITY FOR MORE FIELD INVESTIGATION TO CHECK AND QUANTIFY CORROSION LEVEL IN STRANDS FOR VARYING STRAND LOCATION? CHECKING THE INFLUENCE OF LOOSING THE COOPERATION WITH BRIDGE DECK ON THE LOAD BEARING CAPACITY OF THE PRETENSIONED BEAM. RESEARCH NEEDED ON INFLUENCE OF CORROSION ON SHEAR CAPACITY