www.sefindia.org

[vikram.jeet]

Vehicular loadings :-

These are explained in IRC 6 ,,

(A) For Highways
1) IRC Class 70R
I) Class 70R Train of axle loads  , Total load 100 tonne
ii) Class 70R Tracked Load 70 tonne

2) Class A  train of Axle loads

3) Single Axel /Bogey Axles , also to be seen  , these can govern  for small Bridges and culverts,, also for deck slab design



(B) For Townships Bridges and culverts
1) Class  40 R Or higher
2) Class A Or Class B as specified

3) Sinle axle, Bogey axle loadings

Based on  Width of  road on bridge,  the nos of lanes to be considered is given in IRC 6.



IMPACT FACTORS  & REACTION FACTORS

Impact Factors :-

The Bending moments and shears are further increased by Impact Factors.

Based on Loading Class, impact factors are calculated as per IRC 6.



REACTION FACTORS

IN cross section of bridge deck ,, wheels are placed  on extreme to have maximum eccentricity,  Reaction Factors are worked out based on accepted theories. Curbon's  method to work out Reactions on various Girders (inner / outer)  and these are Reaction Factors
l. e. Reaction factor for Outer Girders
Reaction Factor  for  Inner Girder


As per practice BM and SF were worked  based on whole train loads on bridge in longitudinal span and these were further multiplied  by respective loading Impact Factor   and also Reaction Factor.

[vikram.jeet]

Superstructures
Bridge general arrangement , was basically simply supported spans  over Piers and abutments. This was a period when computer working was not there and no such desktop or any softwares in India. All was manual design show.

X section wise, the GA comprised of two Girders, three Girders or Four girders system with thick deck slab,  kerb with rsiling. Crash barrier came later in codes.

  Girders were mostly Pre stressed Concrete with 12/7 cables,  later 12T13 Tendons.
for longitudinal strength,,

The x direction members - deck slabs,, Intermediate cross girders and End X girders were all RCC design.

[vikram.jeet]

Super structure :-

For moving loads  on deck  , use of INFLUENCE LINE DIAGRAMS (ILD's) was adopted to work out absolute maximum BMs and  SFs by drawing these ILDs for BM and S F  at respective sections in span.


ILDs were the best means to work out absolue Max values  , thou now a days, software likd Staad provides these absolue values of moving loads,
Study of ILD is very important for structural engineers as it provides visualisation of loads placement at critical locations .

Longitudinal analysis for Max Bm,  Max SF were done using ILDs for one lane/two lane / three lanes as the case of various load  classes. Sections at Mid Span,, 1/4 th Span,  1/8th span and Face of End Block (FOB). The absolute maximum values so obtained are for all girders of deck combine.
These values were multiplied further with Impact Factors and reaction Factors to get values of outer girders and inner girders .

[vikram.jeet]

Super structure :-

For moving loads  on deck  , use of INFLUENCE LINE DIAGRAMS (ILD's) was adopted to work out absolute maximum BMs and  SFs by drawing these ILDs for BM and S F  at respective sections in span.


ILDs were the best means to work out absolue Max values  , thou now a days, software likd Staad provides these absolue values of moving loads,
Study of ILD is very important for structural engineers as it provides visualisation of loads placement at critical locations .

Longitudinal analysis for Max Bm,  Max SF were done using ILDs for one lane/two lane / three lanes as the case of various load  classes. Sections at Mid Span,, 1/4 th Span,  1/8th span and Face of End Block (FOB). The absolute maximum values so obtained are for all girders of deck combine.
These values were multiplied further with Impact Factors and reaction Factors to get values of outer girders and inner girders .

[abhy_vivek]

Hello Er. Prashant,


   For any queries related to bridge design and construction (or other infrastructure works / metros) you may connect with undersigned or visit to our office during working days (our present office is at just 15minutes walking distance from your office in Vileparle-E) ...


Best Regards
Vivek Abhyankar
www.sgawings.com

[vikram.jeet]

Dear Er Prashant ji,,

As expressed by Er Abhyankar Vivek ji,, you can seek and share on Bridge designs,,

You can also visit Gsmmon India office, Bridge design Department,  and request for some  Bridge design calculation sheets on some Bridge from their sister concern M/s Gilcon  Delhi (of period 1975-1990) as a sample calcs,, to understand the sequence and presentation of bridge designs. No book can teach the bridge designs in totality and must go thru such calculations. That is what I feel.

But Vivek ji at yr neighborhood,, you are lucky to be benefited.

I will keep posting what little I know out of my fading memory,,

Best regds

[vikram.jeet]

Superstructure
Gap Slab at piers :-

As stated earlier,, the Bridges were seen with Simply supported spans. The Main girders wete PSC (Post tensioned) and to facilitate the  prestressing cables/Tendon s  tensioning, space on pier cap  is required and two side spans were srparated by 1.2 to 1.5 gap. An rcc gap slab is placed resting on bracket created in End X girders on each side. Continuos Bridges came later with as advent of computerisation / softwares

Approach slab at abutments :-

Role of this slab is well known. This needs to be provided to distribute wheel loads on approach  backfill  so that minimal equivalent LL surcharge 1.2 m fill ht can  be taken  for earth pressures. Otherwise the Live Load surcharge will be very high at approach


Kerb & Railing :- these were reinforced ,  but now replaced by Crash Barriers

Expansion Joints :- Earlier these were provided with steel Angles on two sides filled with bitumen filler but with passage of times these joints trouble. Now with rubberised materials, newer products in markets  joint are rider friendly.

[LELE AND ASSOCIATES]

[LELE AND ASSOCIATES]

Dear Vikramjeet Sir and Vivek Sir,


The design philosophy information shared in the above posts and the extended invitation by Vivek Sir is overwhelming, I am highly obliged.

After reading the post I have understood that it is a long journey after the start, but I think with your guidance I should be able to travel it.

I have begun with the text of Krishna Raju and Victor Johnson, and getting myself introduced to the subject. I shall keep posting my queries as I encounter difficulties in this journey.

Thank you once again,
Prashant Lele.

[vikram.jeet]

Dirt wall at edge of Abutment cap :-

This wall is provided as barrier wall  between earthfill and superstructure . It also protect bearings from approach fill.

This is normally 150 to 200 mm thick and one end of approach slab rest over it,,
On bridge side is expansion gap.

This designed for wheel load directly over it and earth pressures plus LL surrchage pressure.