Importance of Bridge Drawings in Speedy Execution of

Doubling Projects and their Fast Track Approvals.

ShrirangKamble*, PradeepBansode#

*Dy. CE(C)/Design/Central Railway, #XEN(C)/Design/Central Railway

Abstact

Indian Railways is determined to cope up with operational requirement by enhancing its route

either by new lines or by doubling, third line, quadrupling projects. To avoid time and cost

overrun it is responsibility of administration to complete these project in scheduled time.

Bridges constitutes the important links in these projects and most of the time becomes

bottleneck of the targets as they populate 2-3 per km. This paper is intended to address the

problems in developing initial scheme of GAD like selection of executable scheme, drawing

skills, minimum essential requirements in the drawing, issues in approval at divisional,

Headquarter level and views of final approving authorities like Chief Engineers, Chief Bridge

Engineer and Commissioner of Railway Safety. Detailed calculations for bridges of 6.1m and

12.2 m spans for different fill heights and track centre are presented to infer the effect of load

sharing. Calculations are carried out for BGML and 25 T loading standards. Certification of

existing bridge for loading standard of new doubled line is also discussed. Selection of bridge

super structure and sub structure depends on the limitations of components like fill height,

curvature, skew alignment, gradients, availability of standard drawings either RDSO

drawings or in-house developed drawings etc. These issues are discussed in details in this

paper. General deficiencies noticed in preparation of drawings are elaborated and preventive

measures like workshops, one to one interaction with draftsmen and SSE (Drawings) etc. are

suggested to inculcate drawing skills in the drawing originating team.

1.0 INTRODUCTION

For any construction project, approval of Design and Drawings of bridges, its GADs, ESPs,

SIPs, project sheets becomes pivotal activity. It is responsibility of design office to supply the

GADs and design & drawings which are easily executable well within time compatible with

the target set from time to time. A general Arrangement Drawing is initiated at DyChief

Engineer (Construction)’s office, routed through open line division and submitted to design

cell of construction organisation and further to CBE office if it affecting the existing bridge

as per para 317 of Bridge manual and Railway Board letter No.2017/CE-I/CT/13/ Procedure

Simplification dated 20.10.2017. Approval GAD’s at each level is herculean task in present

scenario due to limited manpower and diminishing expertise.

Central Railway is executing many projects likeDaund-Manmad doubling, Manmad-Jalgaon

third line, Itarsi-Nagpur third line, Nagpur-Wardha third and forth line, Wardha-Ballarshah

third line, Wardha-Nanded new line, Ahmadnagar-BeedParli new line, Kalyan-Kasara third

and forth line & Pune- Miraj Doubling project.

Presently Pune- Miraj section is a single line section and going to be doubled in next two

years. It is a 280 km section involving 527 minor bridges, 71 major and two important

bridges. It works out to be 2.15 bridges per kilometre. Moreover there are many ROBs,

FOBs to be executed. For completion of this project on fast track, approval of bridges with

fast executable scheme is a vital task.

2.0 AREA OF CONCERNS & REMEDIAL MEASURES

2.1 Load Sharing and overlapping:

Existing minor bridge may be of Low Level RCC slab bridge, pipe bridge,arch bridge, stone

top bridge, hume pipe bridge or box bridge. These may have fill depths varying from 0 metre

to 20 metres or even more. Track centre may vary according to topography, land availability,

alignment, gradient and track geometry. Emphasis is given on to avoid reverse curves.

Wherever Minor bridges are provided with higher fill it will require longer barrel length

resulting into overlapping of new 25 T loading standard and old loading standard.

Completion drawingsreveals important information to know whether there will be endanger

to the existing bridge during execution. There may bepossibility of overlapping with existing

pier, abutment, and wing walls foundation. Sometime imposition of speed restriction and

round the clock deputation of watchman for ensuring safety of exiting bridge becomes

indispensible. Completion drawing reveals the year of construction, loading standard, loads

considered, materialused with grades. In high embankment with minimum track centre, there

is a always a possibility that new standard load will come on existing bridge. It requires the

certification for existing bridge to state that “Existing Bridge is safe to carry 25 T loading”

i.e. new loading standard.

While executing the work, due to unavailability of land, track centre is kept minimum as per

SOD and to avoid reverse curves also. It affects the abutment, wing wall and approach

portion of existing bridge.

There may be possibility that in same bridge different pier widths are provided. It will

increase the shuttering cost. Eventually it will delay the project. Hence, it is the duty of field

engineers to convey the requirement for pier widths.

It is necessary to check fitness of existing bridge for 25 T loading standard. Also physical

condition of bridge needs to be certified. Completion drawings of existing bridge reveals the

loading standard, material and grade used. Based on these inputs, calculations can be carried

out.

As an example for existing bridge of 6.1 m RCC Slab Bridge of BGML loading standard ifwe

need to check it for 25 T loading standard a comparative statement is prepared for BGML

loading and 25 Tonne loading for various track centres, earth fills and respective live load

intensity.

As the depth of fill increases, live load intensity decreases. A difference in BGML and 25 T

loading is shown in Table-1 &Chart-1 for 6.1 m span and Table-2 and Chart-2 for 3.05 m

span. Only 0 to 10 % increase in total load intensity is observed for 25 T loading. This

increase in load intensity may be eaten up by the redundancy in factor of safety used for

designing of existing bridge.

When there is overlapping of load, a new intensity (combined with BGML and 25 T) with

combined envelope of load sharing is drawn and calculation are done in the same way as

discussed above.

The following three cases are seen in the field. In first case there is no overlapping of New

load and old load intensities and new load may or may not come on existing bridge. In second

case there is no overlapping but new load is coming on existing bridge. In third case due to

high fill there is overlapping and load sharing by existing bridge also. These cases are

explained in sketches below.

Case-1: No Load overlapping. Load is shared partially by New and Existing Bridge

Case-2: Just overlapping of load. Load sharing by existing Bridge

Case-3: Overlapping load. Load sharing by existing Bridge

Fill Height

Track Centre

BGML Live Load

intensity

1 5.3 2.57

1 6 2.57

1 7 2.57

1 8 2.57

1 9 2.57

1 10 2.57

1: No Load overlapping. Load is shared partially by New and Existing Bridge

Just overlapping of load. Load sharing by existing Bridge

3: Overlapping load. Load sharing by existing Bridge

25 T Live Load

intensity

Combined Live Load

intensity

BGML Total Load

intensity

25 T Total Load

intensity

Combined

intensity

2.59 2.97 4.37 4.39

2.59 2.81 4.37 4.39

2.59 2.61 4.37 4.39

2.59 2.44 4.37 4.39

2.59 2.29 4.37 4.39

2.59 2.15 4.37 4.39

1: No Load overlapping. Load is shared partially by New and Existing Bridge

Just overlapping of load. Load sharing by existing Bridge

Combined Total Load

intensity

% increase

in load intensity

4.77 9%

4.61 5%

4.41 1%

4.24 -3%

4.09 -7%

3.95 -10%

1 11 2.57

5 5.3 1.65

5 6 1.65

5 7 1.65

5 8 1.65

5 9 1.65

5 10 1.65

5 11 1.65

10 5.3 1.14

10 6 1.14

10 7 1.14

10 8 1.14

10 9 1.14

10 10 1.14

10 11 1.14

Table-1: Calculation for increase in load intensity for 6.1 m span (Existing

Chart-1 Increase in load intensity for 6.1 m span (Existing

Fill Height

Track Centre

BGML Live

2.59 2.03 4.37 4.39

1.66 2.24 10.65 10.66

1.66 2.15 10.65 10.66

1.66 2.03 10.65 10.66

1.66 1.93 10.65 10.66

1.66 1.83 10.65 10.66

1.66 1.75 10.65 10.66

1.66 1.67 10.65 10.66

1.15 1.72 19.14 19.15

1.15 1.67 19.14 19.15

1.15 1.59 19.14 19.15

1.15 1.53 19.14 19.15

1.15 1.47 19.14 19.15

1.15 1.41 19.14 19.15

1.15 1.36 19.14 19.15

1: Calculation for increase in load intensity for 6.1 m span (Existing-BGML & New

1 Increase in load intensity for 6.1 m span (Existing-BGML & New-25 T)

25 T Live

Combined Live

BGML Total

25 T Total

Combined

3.83 -12%

11.24 6%

11.15 5%

11.03 4%

10.93 3%

10.83 2%

10.75 1%

10.67 0%

19.72 3%

19.67 3%

19.59 2%

19.53 2%

19.47 2%

19.41 1%

19.36 1%

BGML & New-25 T)

Combined Total

% increase

Load intensity

Load intensity

Load intensity

Load intensity

Load intensity

Load intensity

in load intensity

1 5.3 4.10 4.66 4.51 5.90 6.46 6.31 7%

1 6 4.10 4.66 4.24 5.90 6.46 6.04 2%

1 7 4.10 4.66 3.90 5.90 6.46 5.70 -3%

1 8 4.10 4.66 3.61 5.90 6.46 5.41 -8%

1 9 4.10 4.66 3.37 5.90 6.46 5.17 -12%

1 10 4.10 4.66 3.15 5.90 6.46 4.95 -16%

1 11 4.10 4.66 2.96 5.90 6.46 4.76 -19%

5 5.3 2.39 2.72 3.30 11.39 11.72 12.30 8%

5 6 2.39 2.72 3.15 11.39 11.72 12.15 7%

5 7 2.39 2.72 2.96 11.39 11.72 11.96 5%

5 8 2.39 2.72 2.79 11.39 11.72 11.79 4%

5 9 2.39 2.72 2.64 11.39 11.72 11.64 2%

5 10 2.39 2.72 2.51 11.39 11.72 11.51 1%

5 11 2.39 2.72 2.39 11.39 11.72 11.39 0%

10 5.3 1.58 1.79 2.47 19.58 19.79 20.47 5%

10 6 1.58 1.79 2.39 19.58 19.79 20.39 4%

10 7 1.58 1.79 2.28 19.58 19.79 20.28 4%

10 8 1.58 1.79 2.18 19.58 19.79 20.18 3%

10 9 1.58 1.79 2.08 19.58 19.79 20.08 3%

10 10 1.58 1.79 2.00 19.58 19.79 20.00 2%

10 11 1.58 1.79 1.92 19.58 19.79 19.92 2% Table-2: Calculation for increase in load intensity for 3.05 m span (Existing-BGML & New-25 T)

Chart-2 Increase in load intensity

2.2 Drafting issues in GADs

Due to very scarce expertise in field

is outsourced. The consultant appointed for this task

preparation of GADs. Due to inadequa

They are not very keen to improve the qu

unable to devote time for grooming the consultant

General Deficiencies noticed during GADs are listed below

1) North direction not shown

2) Third angle projection system

3) Existing bridge details

4) Borehole details/trial pit details very casually shown.

5) No SBC is mentioned.

Increase in load intensity for 3.05 m span (Existing-BGML & New-25 T)

ue to very scarce expertise in field and limited manpower, the work of preparation of GAD

The consultant appointed for this task are employing fresh gradu

ue to inadequate experience, they are adopt “ copy

They are not very keen to improve the quality of GAD. Due to staff crunch R

time for grooming the consultants.

ies noticed during GADs are listed below-

North direction not shown or shown incorrectly.

Third angle projection system is not adopted.

isting bridge details are not shown.

Borehole details/trial pit details very casually shown.

No SBC is mentioned.

25 T)

of preparation of GAD

are employing fresh graduates for the

“ copy –paste culture”.

ality of GAD. Due to staff crunch Railwayis also

6) Notes are incorrect or irrelevant most of the times.

7) Waterway calculations are not properly done.

8) U/S, D/S , curtain walls/drop walls are not shown

9) Sectional elevation, cross section, half top half bottom are not drawn correctly

10) No scale is followed. Scaling is done as per the whims and fancy of AUTO CAD

operator.

11) Seismic zone , standard of loading of existing and proposed loading not mentioned.

12) Nameplate is not correctly written.

13) Names of officers are not written. Sometime designations are also missing.

14) OPT sheets are submitted in nonstandard format.

Due to these deficiencies it takes considerable amount of time to correct the GADs in HQ. It

is seen that correcting the Gad’s required lot of time during checks. For this design cell of

Central Railway construction organisation has organised workshop at Deputy Chief

Engineers office Pune to import know how for preparing a good GAD which is easily

readable and executable. All the persons who are dealing with preparation of GADs attended

the workshop. The same awareness programs are being followed in other divisions also. CBE

Central Railway had also organised a seminar about drafting skills in preparation of Gads.

Representatives of construction, RITES, RVNL, MRVC, DFCCIL and divisions attended this

seminar. Every effort is being made to improve the quality of GADs.

Photo-1 & Photo-2: Discussion about the deficiencies in the drawing with field

Some of the sample drawings of Pune

Figure-

2: Discussion about the deficiencies in the drawing with field

Some of the sample drawings of Pune –Miraj section are shown below-

1 Sectional elevation of Hume pipe bridge

Figure-2 Plan of Hume pipe bridge

2: Discussion about the deficiencies in the drawing with field draftsmen

Figure-

4 Sectional elevation of Abutment-slab bridge

Figure-3 Plan of Abutment-slab bridge

slab bridge

.

Figure-

3.0CONCLUSION

5.1 Use of standard drawings:

5 Sectional elevation of Box bridge

Figure-6 Plan of Box bridge

Use of standard drawings:

Use of standard drawings should be encouraged in the drawing preparing units. First

step is to circulate the list of available standard RDSO drawings with the

limitations/constraints to use such drawings like curvature, gradients, fill height etc. Many

railways have develop in-house designs and drawings of small sub structures like

abutment/piers for small span like 3.05m, 4.55m, 6.1m, 9.15m for different Soil conditions.

These are very useful in preparation of drawings for minor bridges. RDSO website on railnet

10.100.2.19 and local website of Central Railway 10.31.3.3/drg is used for this purpose.

5.2 Awareness programs, interactions

Due to deployment of new inexperienced draftsmen in the consultancies it is

responsibility of design unit to organise workshops and seminars to address the issues of

drafting and drawing skills. The seminars conducted by CBE, Central Railway were really

eye opening for all draftsmen. Similar seminars and interactions to be continued to improve

the quality of drawings and to avoid unnecessary shuttling of the drawings between division

and headquarter. One to one interaction of drawing preparing person and experts with some

selected drawings with common deficienciesshould be done frequently. Healthy environment

must be created to have free interaction in the interest of work.

5.3 Meticulous use of Check list issued by RDSO and CBE/CRS

RDSO has issued checklist for preparations of drawings of bridges. Similarly CBE

and CRS have issued detailed checklist for Railway Bridges, ROB/RUB, Launching schemes

separately. These check lists are exhaustive and very useful in preparation of drawings.

5.4 Quality improvement of Geotechnical investigations

It is suggested to conduct small workshops and field visits to enhance knowledge of

supervisors and draftsmen about geotechnical investigations. Even small things like reading

of bore-logs and interpretation of the parameters should be taught at field level. This will not

only reduce time of preparation of sub structure drawings but it will ensure fast decision

making and speedy execution of bridges.

5.5 Overlapping and load sharing issues

As the depth of fill increases, live load intensity decreases. A difference in BGML

loading standard and 25 T loading standard is worked out. Only 0 to 10 % increase in total

load intensity is observed for 25 T loading in comparison with BGML loading standard. This

increase in load intensity may be eaten up by the redundancy in factor of safety used for

designing of existing bridge. Hence strengthening of existing bridges should be last option to

save money as well as time.

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