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This session provides an in-depth overview of the maintenance and repair of bronze bearings in structural applications. Key issues such as corrosion due to dirt, moisture, and salts are discussed, highlighting problems like misalignment and bearing failure. Real project case studies illustrate methods for cleaning, lubricating, and resetting bearings, including SR 50 A20 and SR 79 A54. Essential procedures for ensuring effective alignment and proper construction are emphasized, alongside lessons learned for successful project execution.
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Structures Session – Part 1 Overview • BD-628 Waterproofing Changes • Strike-Off-Letter 431-11-03 • Bearing Cleaning, Painting, Lubrication & Resetting
Structures Session – Part 1 Clean, Lube, and Reset of Bronze Bearings
Problems with Bronze Plate Bearings • Accumulation of dirt, debris, moisture, and salts cause corrosion. • Excess corrosion can “lock up” the bearings, reduce bearing area, and/or cause misalignment. • Excess stress, vibration, creep, and ultimately failure can occur.
Two Recent Projects: 79 A54: (General picture of bridge) 50 A20: (General picture of bridge)
SR 50 A20, (SR50 over Chartiers Creek) • All bearings were over extended. • Masonry plates had good bearing on concrete, so it was decided that moving sole plates would be easier. • Had to be wary of 12” gas main and bearing eccentricity.
SR 50 A20 Repair Procedure • Jack beams, air arc sole plate welds and remove sole plate and bronze shim. • Blast and prime steel. Power tool clean and lubricate bronze. • Align sole plates to allow for design expansion/contraction while staying below max. allowable eccentricity. • Test fit for full contact with all components, and re-weld sole plates.
SR 50 A20 Repair Procedure Before After
SR 79 A54, (79 SB over SR 51) • Assumed construction errors left most bearings requiring shims – some as high as 1.5” • Some bearings frozen, some misaligned • Over extended on one abutment, under extended on the other.
SR 79 A54 Repair Procedure • Jack beams, cut nuts, slot masonry plate to allow for movement. • Power tool clean all components (bronze, steel) • Lube bronze, and prime and lube steel. • Align masonry plates to centerline of bearing and shim to achieve proper alignment with bronze/sole plate. • Test fit for full contact, pour epoxy below masonry plate, allow to cure and de-jack.
SR 79 A54 Repair Procedure Before After
Lessons Learned • Measure girder location before starting work. • Check for full bearing before finalizing anything. • Seal weld in addition to transverse welds to keep water out. • Make sure sole plates are oriented properly! • Get Designer/Structure Control Involved!
QUESTIONS? Steve Sneddon Construction Project Manager 412-292-9379 ssneddon@pa.gov
