Q 1 What do you understand by Camber, Dead load camber and Live load camber in steel triangulated (Open web) girders? What do you mean by Loss of camber and the reasons for it?
Answer: - camber: - It is the curvature/ deflection intentionally induced in the Girder to compensate for deflection which is to be encountered by it, during service for a particular designed load.The part of the camber corresponding to dead load is called dead load camber and the balance left over is called Live load camber, which should be available as visible and measurable camber in the girder when not carrying load.
Loss of camber: - It is the loss in deflection between the initially induced deflection and that measured at any interval of time with no live load.
The loss of camber is due to:- Over stressing of members beyond the elastic limit.Over stressing of Joint Rivets. Loose Rivets.
Q 2. Give planning of construction of subway (LHS) in place of level Xing including block working within 5.30 hours and what precautions to be taken during block working and in monsoon.
Ans Criteria:- The level crossing having following condition should be identified to replace with LHS.
I.Accident prone LC’s where visibility is not clear
II.Where embankment height is at least 3 met.
III.Where TVU is less but have potential of getting manned level crossing
IV.Other condition as required.
Methodology of execution:- there are various methods such as
I.Pre cast box segment placing (Cut & Cover method )
II.Placement of Precast box after inserting RH girder
III.Box pushing IV.Box puling
V.Cast in Situ The most popular method is cut & cover as per planning boxes to be casted in cess and then If 5:30 hrs block is required to do the work
I.Track dismantling & ballast removal - 25 minuet
II.Earth work in cutting - 60 minuet
III.Sand filling in Bed- 15 minuet
IV.Slab Placing- 30 minuet
V.Box placing - 100 minuet
VI.Geo Textile and Geo membrane- 30 minuet
VII.Back filling- 20 minuet
VIII.Ballast putting- 20 minuet
IX.Track linking - 30 minuet
Equipment required at site during block:-
I.Crawler crane cap-125 ton.- 02 Nos. + 01 No for emergency
II.Poclain- 02 Nos. +01 No. For emergency
III.JCB- 02 Nos.
IV.Tippers - 02 Nos.
V.Water Tanker- 01 Nos.
VI.Gas Cutting and welding set- 01 Nos.
VII.Men Power- 60 Nos.
Cut and cover method include following steps :-
I.Demarcation at site:- Demarcation at site is a pre block activity so that should be done as per site requirement well before block started .
II.Track dismantling and removal of ballast :- these activities should be done as per demarcation at the site with the help of adequate men and machine power. Dismantled material should be placed out of working space and within a easy approach to facilitate at the time of restoration work.
III.Earth cutting :- Earth cutting will be done with the help of poclain and JCB. And slop in cutting is maintained in the ratio of 2:1 to 1:2:1 depending upon the local condition of earth.
IV.Send filling :- send filling with 150 mm in thickness is done over a levelled and compacted surface
V.Slab Placing :- precast slabs are placed over levelled bed of send with the help of crane and the joints of slab are filled with appropriate material.
VI.Box Placing:- the precast RCC boxes are placed as per fresh demarcation over precast slab with the help of crane in proper alignment.
VII.Geo Textile and Geo membrane :- Geo Textile is provided to the surface exposed to earth and ballast to cover the tope and side of boxes in order to filter the water during rain and the Geo membrane is pasted at the joints of boxes with the help of flame to check the flow (seapage) of water through joints of boxes.
VIII.Back filling :- Back filleting is done with machine to fill the space between side of box and embankment across the track and get compacted simultaneously.
IX.Ballast Putting:- Ballast putting is done with the help of men and machine available at site as per track profile .
X.Track linking:- Track linking is done over spreaded ballast and then track is linked with the existing track with all relevant activities and traffic to allow with S.R.Precautions:-
1.Earth cutting to be done properly with proper slope and care should taken that it should not falled and labours/supervisor should be keep safe distance.
2.Sand begs should be provided to bank to retain earth.
3.Sling should check4.After linking track should packed and XL and gauge should check.
Q.3 Explain classification of railway bridges. Define distressed bridge and its category and frequency of inspection. Write the various steps for inspection of triangulated girder through bridge.
1)Important bridges: Important bridges is one which has a very large size of waterway. As per the old practice*, the bridge having total areas of water-way of 110 sq. metre (1200 sq. ft.) and more, or having linear water-way of 180 metres (600 ft) or more, was classified as an ‘Important Bridge’ . The criteria for classifying the bridge has recently been revised by the Railway board.** as per the revised standers ,a bridge is an ‘Important bridge’ if it has total area of water –way of more than 1000 sq. metres or has linear water-way more than 300 metres.
2)Major bridge: major bridge is one, which have a total linear water 0 way of 18 metres (60 ft) or more or which have a clear opening of 12 metres (40 ft) or more.
3)Minor Bridge: The bridge having linear water-way of less than 12 metres (40 ft) in case of single span bridge and less than 18 meters (60 ft) in case of multipal span bridge is called a ‘minor bridge’
4)Culvert: a very small bridge is called a ‘culvert’. Normally a bridge, having span of less than 6 meters, may be called a culvert.
DISTRESSED BRIDGES
1.Definition of distressed bridge
A distressed bridge is one which shows some physical deterioration of its physical condition, indicating the need for rehabilitation through special repairs, strengthening or rebuilding (including replacement of girders).
2.Classification of distressed bridge
Category-1: Those requiring rehabilitation to be done immediately, say with in a year’s time.
Category-2: Those requiring to be kept under observation and to be taken up for rehabilitation on a programme basis.
Group 1: Distressed bridges in Group 1 category are recommended for speed restriction upto 15 KMPH.
Group 2: Distressed bridges in Group 2 category are recommended for speed restriction 25 KMPH to 40 KMPH.
Schedule of inspection of distressed bridges.
Category Inspection By Periodicity
1.(a) Inspector (concerned) Once in a month
(b) AEN or ABE Once in two months
(c) DEN or Sr. DEN Once in three months
2. (a)Inspector (concerned) Once in three months
(b) AEN or ABE Once in a six months
(c) DEN or Sr. DEN Once in a yea
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