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RAILWAY LINE STANDARD HEIGHT IN INDIA
Catenary Height: The contact wire is generally at about 5.5m
from the rail level. The minimum height is around 4.8m (e.g., under
bridges or overpasses, etc.). In yards, in sheds or lines leading
up to sheds, etc., the catenary contact wiremay be higher; 5.8m is
a typical height.Note:- taken from IRFCA (Indian railways )
http://www.irfca.org/faq/faq-elec2.ht
ml
Indian Railways runs double-stacked containers on flatcars under
25 kV overheadelectrical wires. In order to do this, the wire must
be at least 7.45 metres (24ft 5 in) above the track, but IR is able
to do so because of its large loadinggauge and the extra stability
provided by its 1,676 mm (5 ft 6 in) broad gauge track
ELECTRIC LINESMinimum permissible ground clearanceFor safety
considerations, power conductors along the route of the
transmissionline should maintain requite clearance to ground in
open country, national highw
ays, rivers, railways tracks, telecommunication lines, other
powerlines, etc..,as laid down in the Indian Electricity Rules, or
Standards or codes of practicein vogue.
Rule 77(4) of the Indian Electricity Rules, 1956, stipulates the
following clearances above ground of the lowest point of the
conductor:
For extra- high voltage lines, the clearance above ground shall
not be less than5.182 metres plus 0.305 metres for every 33,000
volts or part there of by which the voltage of the line exceeds
33,000 volts.
Accordingly, the values for the various voltages, 66kV to 400
kV, are:
66kV - 5.49m132kV - 6.10m220kV - 7.01m400kV - 8.84m
The above clearances are applicable to transmission lines
running in
opencountry.http://nptel.iitm.ac.in/courses/IIT-MADRAS/Design_Steel_Structures_II/7_transmission_towers/2_material_properties.pdfTWO
LANE HIGHWAYS2.11 Lateral and Vertical Clearance at Underpasses
Wherever a cross road is proposed to be taken below the Project
Highway, minimumclearances at underpasses shall be as follows:
2.11.1 Lateral Clearance
(i) Full roadway width at the approaches including service
roads, if any, shallbecarried through the underpass. Provision
shall also be made for future expansionof the cross road for at
least next 10 years.
(ii) Guardrails shall be provided for protecting vehicles from
colliding with theabutments/piers and the deck of the
structures.
2.11.2 Vertical ClearanceVertical clearance at underpasses shall
not be less than the values given below:
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(i) Vehicular underpass 5.5 m(ii) Pedestrian and Cattle
underpass 3.0 m2.12 Lateral and Vertical Clearance at
Overpasses
Wherever any structure crosses over the Project Highway, the
minimum clearancesat overpasses shall be as follows:
2.12.1 Lateral ClearanceFull roadway width including service
roads, if any, shall be carried through theoverpass structure.
Provision shall also be made for future widening of the
ProjectHighway. The abutments and piers shall be provided with
suitable protection againstcollision of vehicles. Guardrails shall
be provided on abutment side and on sides ofpiers for this purpose.
The ends of guardrails shall be turned away from the line
ofapproaching traffic.
2.12.2 Vertical ClearanceA minimum 5.5 m vertical clearance
shall be provided from all points ofthe carriageway of the Project
Highway to the nearest surface of the overpass
structure.http://infrastructure.gov.in/pdf/FINAL_MANUAL_FOR_SPECIFICATION_STANDARDS.pdf
Highway bridges: In India, highway bridges are designed in
accordance withIRC bridge code. IRC: 6 - 1966 Section II gives the
specifications for thevarious loads and stresses to be considered
in bridge design. There are three
types of standard loadings for which the bridges are designed
namely, IRC classAA loading, IRC class A loading and IRC class B
loading.
http://nptel.iitm.ac.in/courses/IIT-MADRAS/Design_Steel_Structures_II/9_bridges/4_load_&_load_combination.pdf
Fig.7.10 IRC AA loadingIRC class AA loading consists of either a
tracked vehicle of 70 tonnes or awheeled vehicle of 40 tonnes with
dimensions as shown in Fig. 7.10. The units inthe figure are mm for
length and tonnes for load. Normally, bridges on nationalhighways
and state highways are designed for these loadings. Bridges
designed for class AA should be checked for IRC class A loading
also, since under certain conditions, larger stresses may be
obtained under class A loading.Sometimes class 70 R loading given
in the Appendix - I of IRC: 6 - 1966 - Section II can be used for
IRC class AA loading. Class 70R loading is not discussed further
here.Class A loading consists of a wheel load train composed of a
drivingvehicle and two trailers of specified axle spacings. This
loading is normallyadopted on all roads on which permanent bridges
are constructed. Class Bloading is adopted for temporary structures
and for bridges in specified areas.For class A and class B
loadings, reader is referred to IRC: 6 - 1966 Section II.Impact
loadThe dynamic effect caused due to vertical oscillation and
periodicalshifting of the live load from one wheel to another when
the locomotive is movin
gis known as impact load. The impact load is determined as a
product of impactfactor, I, and the live load. The impact factors
are specified by different
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authorities for different types of bridges. The impact factors
for different bridgesfor different types of moving loads are given
in the table 7.1. Fig.7.11 showsimpact percentage curve for highway
bridges for class AA loading. Note that, inthe above table l is
loaded length in m and B is spacing of main girders in
m.Longitudinal forces Longitudinal forces are set up between
vehicles andbridge deck when the former accelerate or brake. The
magnitude of the force F,
is given by
F= W/ V*g t/
Where, W weight of the vehicleg acceleration due to gravityV
change in velocity in time d t
This loading is taken to act at a level 1.20 m above the road
surface. Noincrease in vertical force for dynamic effect should be
made along withlongitudinal forces. The possibility of more than
one vehicle braking at the same
time on a multi-lane bridge should also be considered.
