PROJECT REPORT DESIGN CONCEPTS OF BOW STRING GIRDER (40 M SPAN) OF ROAD OVERBRIDGE AND DESIGN OF SUB STRUCTURE FOR THE SAME.

PRESENTED BY 1. R.M.MEENA 2. SIVA KUMAR (AXEN/Designs/MTP®/MS/S.R.) (XEN/C/JU/NWR) 2. SIVA KUMAR (AXEN/Designs/MTP®/MS/S.R.) 3. L.N.LOKHARE (AXEN/C/KTT/WCR) 4. L.B.SINGH MAURYA (Vice Principal/SRETC/TBM/S.R.)

INTEGRATED COURSE BATCH NO-514 PROJECT GUIDE Sri.G. Bansal COURSE DIRECTOR Sri A.K.Rai

INTRODUCTION On Indian Railway there are 16471 Nos of manned level crossings and 19284 Nos of unmanned level crossings as on date. These Level crossings are affecting the safe & effective functioning of Railways. The Level crossings are the accident prone zones and causes delay of trains due to detention by road traffic at gate.

INTRODUCTION- cont There are loss of valuable human life and Railways properties due to accidents taking place on this level crossings. Keeping safety point of view it become necessary to replace these level crossings by ROB/RUB..

INTRODUCTION- cont Replacing the level crossings with ROB/RUB are being done by Railways in a phased manner based upon its TVU. Where ever possible ROB is preferable over RUB due to its less maintenance, effective usefulness, even though the initial cost of ROB is more.

SCOPE OF THE PROJECT The ROB comprises following different structure:- 1. Main railway span (40 m) 2. Approach spans having 20 m spans 3. Abutment 4. Reinforced earth retaining wall beyond abutment on the approaches where height is less than 4.0 m

SCOPE OF THE PROJECT - cont As far as super structure is concerned only design concept of Bow string girder is emphasized. However for substructure complete design is made and enclosed.

ELEMENTS OF BOW STRING GIRDER MAIN I- GIRDER Main I- girder is purely a tension member because of its geometry. This member is proposed as a prestressed member .The amount the prestressing required shall be less since the same required only nullify the tension.

ARCH MEMBER SUSPENDERS MAIN I GIRDER

ARCH MEMBER Arch member is always in compression and hence RCC is sufficient to take this load. A member size of 450x900 at supports and 450x600 at crown is normally sufficient to carry the compression for this 40 meter span.

SUSPENDERS Since suspenders are pure tension members and it does not requires any flexural rigidity , these members can be provided as HTS strands firmly anchored between main I beams and arch members

CROSS GIRDER Cross girder can be of RCC, which spans between main I -girders. The spacing of cross girders is kept as 4.15 meter & the span is 8.0 meter. At the top of cross girder, a continuous slab of span of 4.15 meter and thickness of 230 mm is provided. Over the slab road-wearing surface as per IRC, specification is provided.

PLAN AT DECK LEVEL BOW STRING CROSS GIRDER 8m 41500 C LINE OF SPAN L C LINE OF BEARING L CROSS GIRDER 8m 4150 41500 PLAN AT DECK LEVEL

LOADING Live load Combinations are Load as per IRC-6 Combinations are 1. Single lane 70R wheeled/track vehicle 2. Two lane IRC –class A, wheeled

ADVANTAGES OF BOW STRING OVER DECK TYPE GIRDERS There is some considerable savings in depth of construction in case of bow string girder compared to typical deck type girder Due to reduced depth of construction, the over all length of ROB get reduced and overall economy achieved

7500 ROAD SURFACE 2500 DEPTH OF CONSTRUCTION=2.50m BOX GIRDER TYPE ROB

BOW STRING GIRDER TYPE ROB 7500 BOW STRING GIRDER ROAD SURFACE 2400 1000 DEPTH OF CONSTRUCTION=1.0m BOW STRING GIRDER TYPE ROB

DESIGN CONCEPT OF BOW STRING GIRDER LIVE LOAD Like our railway bridge rules, these IRC codes does not provide any EUDL,so for the above rolling loads maximum bending moment and shear force shall be worked out using STAAD-PRO 2003 software. However a manual calculation is also shown. Due provision for impact is also considered as per the code.

DEAD LOAD This comprise of dead load of all element of bow string span ,the carriage way wearing coat, foot path and other miscellaneous load such as cables, parapets, crash barriers have been considered

WIND LOAD Wind load is arrived at as per IS 875 part-III.the wind intensity multiplied by the projected area gives the wind load on the structure.

SUB STRUCTURE The substructure consists of two numbers of 1.80 meter dia column spaced at 8.0 meter apart. The depth of trestle beam is fixed as 1.25 meter for stiffness and other practical consideration such as requirement during construction and replacement of bearing.

ELEVATION OF SUBSTRUCTURE 8.0m 1.25m 6.525m 1.80m COLUMN 1.80m dia Rail level PILE CAP PILE 1.0m dia ELEVATION OF SUBSTRUCTURE 4

LOADS AND OMENTS ON COLUMN As we know the the column is critical at the pile cap level . Maximum moments will come at this level which are all explained through the following sketches. Algebraically adding all the moments the column section is designed

SESMIC LOAD Lateral Seismic Coefficient=0.04 Importance Factor =1.5 (for important bridges) Foundation system factor =1.0 (for pile foundation) Design for seismic force=.04x1.5x1.0=.06

SESMIC LOAD Code followed IRC 78 Even though the seismic load does not affect the super structure, the impact on the substructure design is considerable. Seismic Zone III

Lumped mass of super structure Adjoining span -20m Bow string span- 40m Lumped mass of super structure Lever arm Pile cap 1.DUE TO DEAD LOAD Pile

2.DUE TO DL OF SUB STRUCTURE Adjoining span -20m Bow string span- 40m Lumped mass of trestle beam Lever arm Pile cap 2.DUE TO DL OF SUB STRUCTURE Pile

higher load * y-lower load *x Adjoining span -20m Bow string span- 40m y x Lower load Higher load Un balanced moment = higher load * y-lower load *x Pile cap Pile

4. DUE TO LIVE LOAD Adjoining span -20m Bow string span- 40m 1.83 m Lever arm Pile cap 4. DUE TO LIVE LOAD Pile

Foundation The foundation system consists of four no of 1.0m dia pile spaced at 3.0m apart. The piles are proposed to be founded on hard strata, which is available at 25.0m depth. The piles are of bored cast in situ.

Foundation Max. vertical Load in pile workout to be :- under seismic condition = 264 tonnes under normal loads = 214 tonnes lateral load per pile = 14 tonnes

Foundation Vertical load bearing capacity of pile = 320 t The above capacity of piles is based on soil capacity at site. The pile derives its capacity both from friction as well as end bearing.

FOUNDATION Reinforcement design of pile The length of fixity of pile below ground level “Le” is found based on lateral modulus of subgrade reaction of the pile The moment on pile = Horizontal load x Le Based on the moment and the vertical load on the pile,the reinceforcement of the pile is designed

Pile cap L1=2.5m Le 5.318m L=22.5m CALCULATION OF LENGTH OF FIXITY OF PILE