Short notes For Civil Engineer LDCE & Other Exam (P Way)

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(a) Mean annual rail temperature 

Ans (a): Mean Rail temperature- Denoted at tm for a section, it is the average of the maximum and minimum rail temperature recorded for the section. tm= (tmax +tmin ) / 2 

(b)Stress free temperature 

Ans (b): Stress free temperature- Denoted as to , it is the rail temperature of which the rail is free of thermal stress.

(c) Breathing length in a LWR 

Ans (c.): Breathing length in LWR- Breathing length is that length at each end of LWR/CWR, which is subjected to expansion/Contraction on account of temperature variations. 

(d) Gap less joint behind CMS crossing in a turnout 

Ans (d): Gapless joints behind CMS crossing in a turnout- it is desirable to have no gap in fishplate joint behind CMS crossing to have good running and to avoid hammering actions which may cause fractures from bolt holes. 

To achieve this 

(a) – Use a drill bit of 26.05 mm size.

(b) - Take centre of first hole at 183mm rail end and centre for second hole at 249mm from rail end. 

(f) Strengthening of bridge approach 

Ans (f): Strengthening of bridge approach – To strengthen the approaches of Major/ Important Bridges –

 i. PRC sleepers to Drawing No. T-4089 to T-4079 should be provided under guard rails. 

ii. In case of CST-9, ST and wooden road on approaches, PRC sleepers should be provided under the guard rails as well as up to a length of 100 M on the approach with full ballast cushion. 

iii. Ensure 100% fittings at all times both on running rail and guard rails and in approach track up to 100M/ breathing length. 

iv. No buffer rails. Provided SEJ and full ballast section of LWR track up to 100M from abutment. 

v. Provided ballast retainers for one rail length to check slipping of ballast and to ensure full ballast section. 

vi. The sleeper spacing on approaches of bridges up to 100M length should be made 60Cm. vii. Rail level of track in approaches should avoid dips immediately after abutments. viii. Guard rails must be notching at spikes and tie bars should be fixed on outside of sleepers with hook bolts passing through tie bars. ix. Clear timber sp[acing should be 450MM and spacing under joint sleepers should not exceed 200MM. x. Cess width should be 90CM clear of full ballast section for 100M on either side if girder bridges.

(g) Reconditioning of CMS crossing 

Ans (g): Reconditioning of CMS crossing – CMS crossing should be planned for reconditioning when it is chipped at nose or worn out near to the recommended limits. Presently it is being done with hand facing electrodes using welding machines. The CMS is brought to the reconditioning workshops and is kept in water tub, so that high temperature produced during welding may not damage the CMS crossing requiring reconditioning is transported to and back from the workshop. Also it needs traffic block for removing and putting back the CMS in track. A new technology called “Translamatic Robotic Welder” has been found suitable for in- situ reconditioning of CMS crossing without any traffic block. Cost is about Rs. 40, Per CMS and reconditioning life is about 30GMT. 

(h) Classification of bridges as important, major, minor and culvert 

Ans (h): Classification of bridges – On consideration of size of water way and span of the bridge, the bridges are classified as – 

i. Important bridge: A bridge an “Important Bridge” if it has a total area of waterway of more than 1000Sqm or linear waterway of more than 300meters. 

ii. Major bridge: Major Bridge is one, which has a total linear waterway of 18M or more or which has a clear opening of 12M or more. 

iii. Minor bridge: The Bridge having a linear waterway of less than 12M in case of a single span bridge and less than 18M in case of multiple span bridge is called a “Minor bridge.”

 iv. Culvert: A very small bridge is called a “Culvert”. Normally a bridge having a span of less than 6M may #railways #rail #railway #indianrailway #indianrailways #pway