Track structure on bridges Rail and rail joints
Track structure on bridges
Rail and rail joints • Longitudinal profile of rails. • Rail cant. • Rail joints over the bridgea) Small bridges having opening < 6. 1 m rail joint should be avoided. b) For other spans, the preferred position is at 1/3 the span from the ends. c) Rail joint should be avoided within 3 m from abutment.
SWR on bridges • SWR may be continued over girder bridges with unballasted decks upto 13. 3 m opening if symmetrical. • In case of unsymmetrical upto 6. 1 m opening. • 26 m long rolled rails may also be provided. • If SWR is laid, no fish plated joint should be located on the girder or within 6 m from abutment
LWR on bridges • LWR can be continued over ballasted deck bridges without bearings like slabs, box culverts and arches. • LWR / welded panel can be laid over bridges with / without ballasted deck are as follows: 1. Bridges provided with rail free fastenings (single span not exceeding 30. 5 m and having sliding bearings on both sides). 2. Bridges provided with rail free fastenings and partly box anchored (single span not exceeding 30. 5 m and having sliding bearings on both sides).
Table -1 Maximum overall length of bridges permitted on LWR / CWR on BG Temperature Zones Rail section Rail free fastening (PRC/ST) in approaches Rail free fastening and partly box anchored (PRC/ST) in approaches I 60 Kg 52 Kg / 90 R 30 45 77 90 II 60 Kg 52 Kg / 90 R 11 27 42 58 III 60 Kg 52 Kg / 90 R 11 27 23 43 IV 60 Kg 52 Kg / 90 R 11 27 23 43
3. Welded rails may be provided from pier to pier with rail free fastening and box anchoring as per the case with SEJ on each pier. 4. LWR / CWR may be continued over a bridge with the provision of SEJ at the far end approach at 10 m from abutment. 5. Welded panel may be provided over a single span bridge with rail free fastenings and box anchoring as per the case with SEJ at 30 m from abutment.
Rail Max Temp. movement Zone of SEJ Max. length of bridge with SEJ With ST / PRC approach sleeper Initial gap provided at td. With CST-9 With ST / PRC With CST-9 approach sleeper approach IV 190 55 45 7 Cm 6. 5 Cm III 190 70 70 7 Cm 6. 5 Cm II 190 110 100 6. 5 Cm I 190 160 150 6. 5 Cm 6. 0 Cm --------------------------------------------------------------------------II 120 20 15 4. 0 Cm I 120 50 50 4. 0 Cm
The length of single span bridge permitted temperature zone-wise shall be as under: Temp. Zone IV Max. length of single span br. with SEJ (190 mm gap) at 30 m away from both abutments with full creep resistant fastening at approaches (td = tm) 75 m III 87 m II 110 m I 146 m
Provision of guard rails • Should be provided on all girder bridges. • Should be provided on prestressed concrete girder bridges without deck slab. • Should be provided on all major and important ballasted bridges and where derailment may cause serious damages. • On all flat top, arch and prestressed concrete girder bridges with deck slab where guard rail is not provided the whole width of the bridge between parapet walls shall be filled with ballast upto sleeper level.
Design of guard rail
Splaying of guard rail • In the case of through girder bridges on double lines, guard rails should be splayed on either ends. • Other than through bridges splaying be done only on the facing direction. • However the non splayed end should be bent downwards after it is stopped at the end of the abutment and wooden block provided.
Trolley refuse • Bridges with span < 100 m • Bridges with span > 100 m at 100 m. on each pier.
Stipulation. • Rail joint should be avoided within 3 m from abutment. • In case of LWR full ballast section be provided up to 100 m from abutment. • Joggle plating of AT welds if length of water way is ≥ 100 m and on approaches upto 100 m avoided.
Steel sleepers on bridges • It refers to both channel sleeper and H-Beam sleeper.
Introduced • Channel sleepers were first introduced in India in the year 1992. • ‘H’ beam sleepers in the year 2005.
Channel Section • Made with ISMC section
‘H’ beam section • Made with ISHB rolled section
Weight of H-Beam sleeper • Weight of H-Beam sleeper complete with ZRF fitting is 159. 1 Kg for 200 mm height compared to 151. 33 and 181. 00 for 150 mm and 200 mm respectively for channel sleeper.
Suitability • May be provided over all types of track geometry like plain, curved or skewed track.
Clip & bolt
ZRF (Zero restraint fastening)
ERC on ‘H’ Beam sleeper
ZRF on H-Beam sleeper
Spacing • Existing clear spacing is 510 mm. • Channel sleepers should be kept: a. Maximum centre to centre spacing at 600 mm except in open web girder where the spacing may be suitably increased depending upon the top flange width. b. Clear distance between joint sleepers not be > 200 mm. If the width of top flange exceeds 450 mm the special channel sleepers to be provided.
Design dimensions and sections • Fabrication of steel sleepers and its protective coating should be in conformity with BS-45 of RDSO. • For girder, location of steel sleeper should be marked and numbered. • Fabrication of steel sleeper should be location specific considering girder center, top flange cover plates, rivet pitch etc.
Continued. . • In case of bridge on curves, location of sleeper should be marked after taking into account the realigned curve. • In case of transition curves the thickness of pad plates should take care of the cant gradient.
Laying of steel sleeper. • Creep should be adjusted and rails pulled back to position ensuring that no joint is supported. • SSP (sleeper seat painting) and the entire top. • Wherever required cross levels and alignment be corrected in advance. • Single pad plate below sleeper is preferable. • Packing plate can be used if required to adjust parameters. • Pad plates are not required if Neoprene pad is provided to cover the rivet heads.
Inspection. • Thoroughly by ADEN and SSE once in a year by rotation. • SSE (P Way) and SSE S&T once in six months if sleepers are insulated.
Thank you.
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