Pack Rust Identification and Mitigation

Transcription

1 Pack Rust Identification and Mitigation Strategies for Steel Bridges Mark Bowman P.E. Ph.D. Professor of Civil Engineering Chintan Patel Graduate Research Assistant School of Civil Engineering Purdue University SPR

2 Study Advisory Committee Timothy Wells (PA) Stephanie J. Wagner (BO) Christopher Wheeler Jose Ortiz Michael Black Nathaniel Pfeiffer 2

3 Literature review. 3 Major Tasks Reviewing existing mitigation strategies and repair procedures for selected DOTs. Pack rust in Indiana Bridges. 3

4 Task 1 Literature Review 4

5 Pack Rust or Crevice corrosion Localized attack on metal surface. Crevice formed between two joining surfaces. Metal Metal Metal Non-metal 5

6 Initiation Process Crevice corrosion initiation process Differential oxygen concentration needed Aqueous solution(water), pathway for ions to flow Process accelerated [Cl ] present ph acidic present 6

7 Mechanism Formation of differential oxygen concentration cell. Steel Specimen 7

8 Mechanism 8

9 Inhibitors like chromium decreases the corrosion rate. Severe corrosion takes place near the mouth of the crevice. Bulk ph > 7 H + Crevice ph < 7 Steel Specimen 9

10 Attributes of crevice corrosion Crevice height Ranging from 0.1 mm to 3 mm. Large enough to allow entry of electrolyte (water) small enough to not allow electrolyte to flow out.

11 Rust build-up eventually seals the crevice and the corrosion process stops. (U.R.Evans, researcher in corrosion science) On contrary Sealing the crevice without neutralizing the active corrosion product can cause accelerated corrosion.(roads and Bridges, Sept,2003) 11

12 Task 2 Mitigation strategies and repair procedures of selected DOTs 12

13 Mitigation and repair strategies Stripe coat Caulking Penetrating sealer Backer rod 13

14 Stripe coat 14

15 Caulking 15

16 Penetrating sealer Has viscosity to penetrate into the crevice. Ability to neutralize the corrosive environment inside the crevice. 16

17 Backer rod and sealant Sealant Backer Rod 17

18 State Dept. of Transportation Stripe coat (21 states) Caulking (10 states) Penetrating sealers (5 states) Alabama, California, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Maryland, Massachusetts, Minnesota, New Jersey, New York, North Carolina, North Dakota, Ohio, Oregon, South Dakota, Virginia, West Virginia, Wisconsin California, Delaware, Florida, Iowa, Maryland, Missouri, Ohio, Oregon, Washington, West Virginia Washington, Missouri, Iowa, Illinois, Delaware Backer rod (2 states) Oregon, Washington 18

19 Repair Procedure Oregon Remove pack rust by mechanical cleaning, and heating water-saturated pack rust to a minimum of 250 F and a maximum of 400 F, or Using 35,000 psi ultra-high pressure water jet. 19

20 Missouri Calcium sulfonate rust penetrating sealer Suitable for any steel structure that has developed pack rusting in overlapping steel plates, joints or at bolted areas. Applied in accordance with SSPC-PA1. 20

21 Missouri Continued. Can be applied to bearings, overlapping steel plates, pin connections, pin and hanger connections and locations where rust bleeding, pack rust, layered rust occurs. 21

22 Washington Pack rust of 1/16 inch or greater. Clean to a depth of ½ of the gap width, maximum of ¼ inch. Cleaned gap treated with rust penetrating sealer. Apply Caulk to form watertight seal. If gap greater than ¼ inch Gap should be filled with foam backer rod material. Apply sealant over the backer rod. 22

23 Task 3 Pack Rust in Indiana Bridges 23

24 Pack Rust in Indiana Bridges Gathered relevant pack rust information from Bridge inspection reports. 24

25 Typical Members Affected by Pack Rust Bearings(Rocker, some cases Elastomeric) Splice connections Hinge-pin connection Gusset plate and other connections Beam cover plates End diaphragms 25

26 Bearings 26

27 Pack Rust 27

28 Pack Rust 28

29 Pack Rust 29

30 30

31 Pack Rust 31

32 Splice plates Pack rust 32

33 Pack rust 33

34 Hinge-pin connection Pack Rust 34

35 Pack rust 35

36 Gusset plates, battens and angles 36

37 37

38 38

39 39

40 Cover plates 40

41 41

42 Diaphragms 42

43 Cross bracings connections Pack Cross rust bracing fallen down 43

44 Statistical Analysis on Data Collected Total state owned steel bridges in 4 districts inspected 1235 No. of bridges with some form of pack rust

45 Percentage 60 Percentage of Bridges with Pack Rust 56 % % % 22 % Fort Wayne Crawfordsville Greenfield Seymour 45

46 BERCENTAGE OF BRIDGES WITH PACK RUST PERCENTAGE OF BRIDGES WITH PACK RUST BASED ON FEATURE INTERSECTED Water Body Road RR Abandoned RR FORT WAYNE CRAWFORDSVILLE GREENFIELD SEYMOUR DISTRICTS 46

47 NUMBER OF BRIDGES MEMBER WISE COUNT Fort Wayne Crawfordsville Greenfield Seymour

48 PERCENTAGE OF OCCURRENCE COMPARISON OF PERCENTAGE OCCURRENCE OF PACK RUST Fort Wayne Crawfordsville Greenfield Seymour SPLICE BEARING 48

49 District wise Salt usage (lane-miles) salt (tons) (tons/lane-miles) Fort Wayne 4, Annual Winter Maintenance Report FY 2013 by Phil Ivy Crawfordsville 4, Greenfield 4, Seymour 4,

50 Splice plate pack rust in detail 50

51 Severity rating for pack rust in splices Rating 1 Severe PR - > ¾ inch bowing of splices or bolt failure 51

52 Rating 2 Moderate to severe PR - ¼ to ¾ inch bowing of the splice plates Rating 3 Moderate PR Visible bowing of the splice plates < ¼ inch of PR 52

53 Rating 4 Minor to moderate PR - Visible middle of splice Connection. Rating 5 Minor PR - Rust middle of splice Connection. 53

54 Number of years after painting YEARS AFTER PAINTING VS. PACK RUST SEVERITY IN SPLICES (4DISTRICTS) Pack Rust Severity 54

55 Avg. age at pack rust detection AGE AFTER BUILT VS. PACK RUST SEVERITY IN SPLICES (4DISTRICTS) Pack rust severity 55

56 0 0 PERCENTAGE OF BRIDGES PERCENTAGE OF BRIDGES WITH PACK RUST IN SPLICES OVER FEATURE INTERSECTED DISTRICT BREAKUP Water Roads RR Abandoned RR FORT WAYNE CRAWFORDSVILLE GREENFIELD SEYMORE 56

57 PERCENTAGE OF BRIDGES PERCENTAGE OF BRIDGES WITH PACK RUST IN SPLICES OVER FEATURE INTERSECTED WATER ROADS RR ABANDONED RR FEATURE INTERSECTED 57

58 Age ofpack rust after painting Trends for Cover Plates Cover plate condition vs age after painting minor moderate severe Condition 58

59 Conclusions Pack rust frequently occurs in Indiana bridges Most common locations Bearings(top and bottom) Splice plates (joints) Hinge-pin connections Gusset plates Lower chords of truss No correlation between pack rust occurrence and salt usage. 59

60 Conclusions Common mitigation and repair methods Stripe coat Caulking Penetrating sealer (Promising mitigation and repair method) 60

61 Future Tasks Investigate remaining 2 districts of Indiana. Investigate strength degradation due to pack rust. Review repair strategies for Indiana.

62 Questions? 62