Plate Bearing

The Plate Bearing are devided into 2 type which is Top Plate Bearing & Bottom Plate Bearing.
Top Plate Bearing will be installed at the SBG while Bottom Plate Bearing will be installed at the Pier Head. Following are Hercules Plate Bearing photos:

Top Plate Bearing - Cylinder Type (to be slot in and cast inside the SBG)

 

 

Top Plate Bearing - Rectangular Type (to be slot in and cast inside the SBG)

 

 

Bearing Design By Hercules Engineering

Bearing Top Plate Sockets

Bearing design by Hercules Engineering were previously reviewed by DDC with comments that large and closely spaced bearing top sockets(less than 20mm gap) was not acceptable, as the sockets will clash with the SBG segment reinforcement T20. One sample was brought in to the meeting table for deliberation.

Socket gaps > 20mm but end plate gaps less than 20mm

Gap between sockets less than 20mm

Space Limitation At Segment Downstand

Hercules Engineering informed due to large bearing forces on curved spans, along with up-lift forces, space constraint on the segment down-stands limits the spacing of the bearing sockets.

Hercules Engineering informed that higher grade of steel was used in the bearing design i.e. upgrade from Grade 43A to Grade 53. 

 

Bearing Forces at Curved Spans(R>215 )

25 cases in Package A, all at curved spans (both ST and DT) were identified with large bearing forces and up-lift forces, remained facing difficulty to have sockets spaces wide enough to avoid clash with the segment reinforcement.

Hercules Engineering to look into smaller socket size. Other option is to add another row of socket, or enlarge the bearing plate in one direction.

Hercules Engineering to revert back to DDC by next week Tuesday 02/Oct/2012.

Installation of Bearings At The Site

Due to rebar congestion at the pier head and at the RC up-stand plinths, Launching Contractor informed it was extremely difficult to launch the span in position precisely

 

Cutting Reinforcement at RC Plinths

The option of cutting some of the T20 reinforcement was discussed. DDC was not in fovour of cutting the re-bar. The bars are required to take care of the up-lift forces.

Hercules/MC/LC to explore the possibility to provide steel pins locked up with the bottom plate sockets to replace rebar in cases where the re-bars are inevitably forced to be cut-off.

DDC informed that cutting of the re-bars shall be treated as case by case, particular at areas where there are no up-lift forces.

 

Option To Widen Pier Head

MC was asked to study the possibility to widen the pier head from current 2.0m wide. A larger pier head will be able to accommodate a bigger bottom bearing plate.

LC/MC informed a larger pier head may be constraint by the current LG pier bracket design. The stressing bars used to secure the LG pier brackets may be too close to the surface of the pier head (25mm+/-). BBR to check and inform Minco.

 

Special Crossings – Bearing Movement

The construction drawing indicated the movement for the free bearing is 8mm. Hercules Engineering requested DDC to reduce the movement from 8mm to 5mm.

DDC will check and revert back to Hercules Engineering.