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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

113

Economic Solution of Super Structure for Bridge of 20m Span

Natraj Singh

1

, Dr. N.P. Devgan

2

, Dr. A. M. Kalra

3

1Dy. Chief Project Manager (IRSE), Dedicated Freight Corridor Corporation of India Ltd., Old Railway Colony, Near Anand

Market, Ambala Cantt.-133001, India

2Senior Structural Consultant, PEC-Centre for Consultancy Engineering, PEC University of Technology, Sector-12,

Chandigarh- 160012, India

3Formerly Prof. in Civil Engineering Department, PEC University of Technology, Sector-12, Chandigarh- 160012, India Abstract- The present study aims at exploring the

economical solution for superstructure of 20m span bridges among reinforced concrete T-beam, reinforced concrete I- beam, prestressed concrete beam and steel composite I-beam. The analysis and design is done under Indian Road Congress (IRC) loading for selection of most economical section for all four types of super structures. The effects of the placement of span are also studied in details for normal ground condition as well as launching above the Railway line. In normal ground conditions, reinforced concrete T-beam & prestressed concrete I-beam are found to be economical. Whereas in case of above railway line prestressed concrete I-beam proves to be more economical than other options considered for the study. When the effect of speed restriction is also combined with the traffic block cost then the composite steel girder becomes the most economical option but when the effect of periodic maintenance is also added, it becomes costliest option. The effect of sacrificial type of shuttering is also considered for the cost implication and this is found to be cheaper in case of bridges over railway lines. The present paper will facilitate as a hand on tool for selection of economical superstructure type for 20m span bridges.

Keywords- Prestressed concrete I-beam, railway block cost, reinforced concrete T-beam, reinforced concrete I- beam, sacrificial shuttering, steel composite I-beam.

I. INTRODUCTION

The pace of infrastructure development in India has increased to cope with the requirements of developing country. The projected gross domestic product (GDP) growth is likely to remain in double digit in near future. This increased pace of Infrastructure development has put lot of thrust on human as well as material resources. In modern era of growth in Infrastructure field related to road and rail sector, bridges consume substantial share of resources and sometimes play a critical role in working out the economic viability of the project. To meet the growing demand, infrastructure has to be developed by optimizing the resources.

Keeping in view the fund constraints faced by infrastructure organisations, the present study aims to develop an economic solution for construction of superstructure for 20m span bridge under Indian Road Congress (IRC) loading. Four different superstructure types have been chosen for the economic analysis namely, reinforced concrete T-beam, reinforced concrete I- beam, prestressed concrete I-beam and steel composite I-beam. The design of all the options is based on Indian Road Congress (IRC) codes. The effects of placement of span in normal conditions and launching above the railway line have different cost implications because cost associated with the Traffic block has a substantial cost share in launching process. There is another aspect of speed restriction imposed on the goods and passenger trains during placement of span, which led to the huge monitory loss to the Indian railways. Thus an attempt is made in this study to quantify the cost associated with the traffic block and the speed restriction. Another important aspect is the use of sacrificial shuttering in combination with conventional shuttering and its effects are explored from the economy point of view.

II. REVIEW OF LITERATURE

Many options are available to the planners with the advancement in design and construction technology. The decision of choosing the best option among the available alternatives is guided by the principal of utilisation of minimum resources.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

114 One important study about the life cycle cost is done by Huang, et. al. for new highway bridge in Taiwan. Three alternatives, namely the pre-stressed concrete bridge, the steel bridges with painting, and the steel bridge with galvanization, are considered for the new bridge and are evaluated for their life cycle cost. The study reveals that the life cycle cost of steel bridge is always higher than of Pre-stressed concrete bridge and pre-Pre-stressed concrete bridge has the lowest life-cycle cost.

The efforts of planners to reach at optimal solutions for specific bridges are well established. In most of the cases of cost analysis, generally two options of materials or shapes are taken and no specific stress on erection/launching methods is taken into account for comparison. Further in road over bridges (above railway track), the impact of traffic block cost on overall construction cost also needs evaluation. Broadly, so far cost analysis of bridges is carried with specific location and two variables.

III. DESIGN PHILOSOPHY

The super structure having 21.96m total span and 20.0m effective span is individually analyzed by the grillage analysis using main girders along the longitudinal direction and slabs in the transverse direction.

The system, being a 4 girder system with spacing of 2.65m, is supported with bearings below each girder, is analyzed separately under dead load of girder. The clear carriageway is 7.5m and total width of Super structure is kept 12.0m.The footpath is provided on both sides. Composite action is considered for the slab load, super imposed dead load and live loads. Slabs are provided sloped in the direction of required camber. Girders are accordingly raised with higher pedestals. Live loads are run in position concentric to all the 4 girders, and combinations are worked out based on the minimum distance between the two lanes.

The depth of deck slab has been kept constant in all the options. The depth of girders have been chosen on the basis of guiding formulas and the section properties of all the four different options have been given in the table I.

TABLE I

SECTIONAL PROPERTIES OF GIRDERS CONSIDERED FOR COMPARISON

No Description Unit

RCC- I Sect. RCC-T beam PSC-I Sec. Steel Comp.

1 Depth of

deck slab m 0.25 0.25 0.25 0.25

2 Web depth m 1.80 2.25 1.56 1.35

3

Top Flange width (at mid span)

m 0.70 0.93 1.00 0.40

4

Web width (at mid span)

m 0.35 0.33 0.29 0.012

5 Web width

(at Support) m 0.70 0.63 0.80 0.012

6

Bottom Flange width (at mid span)

m 0.70 0.63 0.80 0.60

7

Area of section (at Mid Span)

m2 1.52 1.40 1.40 0.09

8

Area of section (at Support)

m2 1.93 1.86 1.94 0.09s

9

Moment of Inertia (Izz) at Mid Span

m4 0.69 0.69 0.51 0.02

10

Moment of Inertia (Izz) at Support

m4 0.80 0.81 0.62 0.02

For reinforced concrete beams M35 grade of concrete and for prestressed concrete M40 grade of concrete have been considered. The grade of reinforcement has been kept Fe500 for all the options.

After carrying out the analysis, the graphs are drawn for design shear force and bending moments for various combination of loads.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

115 Fig. 1: Shear force variation along the span of beam under dead load

only

[image:3.612.47.580.81.718.2]

Fig. 2: Shear force variation along the span of beam under super imposed dead load.

Fig. 3: Shear force variation along the span of beam under live load.

Fig. 4: Bending moment variation along the span of beam under dead load

Fig. 5: Bending moment variation along the span of beam under super imposed dead load

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

116

IV. CONSTRUCTION OF SUPERSTRUCTURE

The planning and coordination between the designer and site engineers is very important because erection/placing of span affects the overall cost in significant way. The erection /placement of span depends upon the ground conditions, volume of work, repetitive nature of work, utilization of existing resources etc.

The construction of superstructure involves cast in situ in case of T-Beam and casting or fabrication of span in yard and placing it with hydraulic crane in other methods. Normally in urban areas, the bridges are constructed for grade separation or for crossing the Railway track. Hence, following two ground conditions are considered.

A. Normal Ground Condition

In this condition, it is considered that the supporting ground is having sufficient bearing capacity to support the launching/erection crane and there is a sufficient space for stabling the crane for launching without disturbing the local traffic.

B. Above Railway Track

In this condition, it is considered that the supporting ground is having sufficient bearing capacity but traffic block from Railways is required for launching/erection of super-structure.

Considering above mentioned two ground conditions, following methods are adopted for erection/placement of superstructure of 20 M span of bridge.

1.Using Form work (Cast in situ Beams and deck slab)

2.With land based hydraulic cranes (Pre-cast Beams and

Caste-in-situ deck slab)

V. ESTIMATION METHODOLOGY

All the major activities affecting the cost of super-structure are bifurcated and effects of these activities are analyzed while calculating the total cost of super-structure. The activities are bifurcated on the basis of different Ground Conditions. In this work, two type of shuttering combinations are considered. In first case the conventional shuttering is used for casting of girders and deck slab.

This will require placement of shuttering and de-shuttering for both the girder and deck slab. In other case, the combination of conventional and sacrificial shuttering is considered in which conventional shuttering is opted for the beams and sacrificial shuttering is opted for deck slab. The sacrificial shuttering is left in place permanently and will not require temporary support system. This system will reduce the requirement of speed restriction. The various steps involved in construction of superstructure common in both the ground conditions and effects of conventional and sacrificial shuttering with traffic block and speed restriction

are given in flow chart , i.e., Fig 7.

A. Estimation and Costing details

The estimation of resources and its costing has been divided into various categories to appreciate effects of each stage over total costing of super structure.The different stages involved in estimation for both ground conditions are shown in the flow chart, i.e., Fig 8.

The various stages of estimation and costing are discussed below:

B. Attributed to Material Quantities

The quantities of materials have been calculated based on design parameters. While considering the sacrificial shuttering, the advantage of substituting the tensile reinforcement in composite deck slab is not considered. The quantities of shuttering materials are calculated based on the two methods. In first method, conventional shuttering is considered for girders and deck slab and in second method, conventional shuttering for girders and sacrificial shuttering for deck slab has been considered.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

117

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

118

Fig: 8- Flow Chart for Estimation and costing.

TABLE II

QUANTITIES OF MATERIALS REQUIRED FOR VARIOUS TYPE OF SUPER-STRUCTURES OF 20 M SPAN

No Type of Superstructur e

Qty of Material per Span (Including Deck Slab Concrete)

Concrete Reinforcement Conventiona l Shuttering

Combination of Shuttering Pre-Stressing

Cable Structural Steel Conventional for

girders

Sacrificial for deck slab

Unit Cum MT Sqm Sqm Sqm Kg. MT

1 RCC T-beam 159.0 29.0 680.0 680.0 0.0 0.0 0.0

2 RCC I-beam 173.0 38.0 644.0 427.0 217.0 0.0 0.0

3 PSC I-Section 162.0 19.5 563.0 373.0 190.0 3420.0 0.0

4 Composite Steel girder and RCC deck slab

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

119 The rates adopted for the estimation of cost are based on the Bridge works executed by Indian Railways in Northern Part of India. The old tender rates are updated based on WPI index. For the sacrificial shuttering rates are taken from market. The cost estimation for casting/ fabrication of girders including deck slab considering conventional shuttering only and combination of conventional and sacrificial shuttering has been calculated by multiplying the quantities (given in Table-II) with Cost and this cost is considered same for both the cases, i.e., in normal ground condition as well as above railway track.

C. Composite cost for Normal Ground Condition

To arrive at total cost, the estimation of machinery and other resources required for launching of beams is calculated for the normal ground condition.

It is considered that two cranes will work simultaneously from both ends.

There is no constraint on working hours of crane and sufficient space is available for working of cranes. The crane capacity for reinforced concrete I- beam and prestressed concrete I- beam is kept 75 MT which is more than double the load to be carried. The rates for hiring of cranes are taken from the market.

The Composite Steel girder having weight 8 MT is the lightest among all the four options and launching cost of Rs. 80,000.0 for composite steel girder is least among all the categories considered. The launching cost of Rs. 3,00,000.0 for pre-stressed concrete beams having weight 65MT and reinforced concrete beams having weight 75 MT is same and is approximately 3.75 times the launching cost of steel beams.

The total cost of superstructure in case of normal ground conditions is calculated by adding the cost attributed to material quantities, launching resources and other allied activities.

TABLE III

COMPOSITE COST STATEMENT CONSISTING OF CONSTRUCTION/FABRICATION COST (MATERIAL COST )AND PLACEMENT COST IN CASE OF NORMAL GROUND CONDITIONS (IN INDIAN RUPEES)

N o

Type of Superstructu re

Construction/ Fabrication Cost (material cost)

Launching Cost by Crane(placeme nt cost)

Total Cost

Conventional Shuttering

Combinati on of Shuttering

With Conventional Shuttering

With Sacrificial Shuttering

1 RCC T-beam 3341800 3341800 NA 3341800 3341800

2 RCC- I-beam 4041500 4160850 300000 4341500 4460850

3 PSC I-Section 3253000 3357500 300000 3553000 3657500

4

Composite Steel and RCC Girder

3797200 3857950 80000 3877200 3937950

D. Composite cost above Railway Track

To arrive at total cost in this case, the cost of railway traffic block and cost associated with speed restrictions and launching is considered. The Railway traffic block due to detention of moving trains plays significant role in the total cost of super structure. Presently, there are no clear guidelines to charge the cost effect of speed restriction in addition to the traffic block cost.

The railway traffic block cost depends upon no of trains plying in the section. This cost of block per hour has been calculated for trains varying from 20 to 80 running on section per 24 hours. The cost associated with speed restriction of 20 Kmph in a stretch of 100 meters has also been calculated.

The work of placement of spans above railway track will be carried out during the traffic block. There is provision of extra crane to meet out any failure during the block period. The capacity of extra crane is kept the same to utilize in case of defect in the regular working crane. Two Crane will work simultaneously from both ends and third crane will be kept as stand by. It is assumed that work of placement of girders in the traffic block will be completed in two days. The cost of hiring of cranes is taken for complete job per span, which is Rs. 6, 00,000.0 for reinforced & prestressed beams and Rs. 1, 60,000.0 for steel composite beams.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

120 The cost of placement for all the four options of super-structure is calculated by adding the cost of launching and cost of traffic block for various frequencies of running of trains in a section.

From the table IV, it is clear that cost of placement is less in case of RCC T Beam and steel composite girders. The cost of placement of RCC I Beam and PSC I Section is same but is higher than the other two options. As the frequency of trains increases in a section, the difference in cost in the placement of girders for options 1 & 4 and 2 & 3 increases sharply.

The total cost of Super-Structure above Railway Track is calculated by adding the construction/fabrication cost of girders, launching cost of girders, Cast-In-Situ cost (T Beam), and Railway Traffic Block cost. This total cost of Super-Structure has been calculated for both combinations of shuttering and various frequencies of trains in a section. This cost comparison does not include the cost of speed restriction and the affect of sacrificial shuttering is not appreciable in the table VA & VB.

TABLE IV

COST STATEMENT CONSISTING OF PLACEMENT OF SPAN INCLUDING LAUNCHING COST AND BLOCK COST ABOVE RAILWAY TRACK (IN INDIAN RUPEES)

S N o

Type of Superstructur e

Block Duratio n (in hours)

Total Cost for Placement of Span

20 Trains per day

35 Trains per day

50 Trains per day

65 Trains per day

80 Trains per day

1 RCC T-beam 2 4137036 7009383 9881731 12754078 15626426

2 RCC- I-beam 3 6805553 7609383 15422596 19731118 24039639

3 PSC I-Section 3 6805553 7609383 15422596 19731118 24039639

4

Composite Steel and RCC Girder

2 4297036 7169383 10041731 12914078 15786426

TABLE VA .

COMPOSITE COST STATEMENT CONSISTING OF CONSTRUCTION/FABRICATION COST (MATERIAL COST) AND PLACEMENT COST ABOVE RAILWAY TRACK (IN INDIAN RUPEES)

No

Type of Super-Structure

20 Trains per day 35 Trains per day 50 Trains per day

with

Conventional Shuttering

with Sacrificial Shuttering

with

Conventional Shuttering

with Sacrificial Shuttering

with

Conventional Shuttering

with Sacrificial Shuttering

1 RCC T-beam 7478836 7478836 10351183 10351183 13223531 13223531

2 RCC- I-beam 10847053 10966403 11650883 11770233 19464096 19583446

3 PSC I-Section 10058553 10163053 10862383 10966883 18675596 18780096

4

Composite Steel and RCC Girder

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

[image:9.612.46.568.166.326.2]

121 TABLE VB

COMPOSITE COST STATEMENT CONSISTING OF CONSTRUCTION/FABRICATION COST (MATERIAL COST) AND PLACEMENT COST ABOVE RAILWAY TRACK (IN INDIAN RUPEES)

No Type of Superstructure

65 Trains per day 80 Trains per day

with Conventional Shuttering

with Sacrificial Shuttering

with Conventional Shuttering

with Sacrificial Shuttering

1 RCC T-beam 16095878 16095878 18968226 18968226

2 RCC- I-beam 23772618 23891968 28081139 28200489

3 PSC I-Section 22984118 23088618 27292639 27397139

4 Composite Steel and RCC

Girder 16711278 16772028 19583626 19644376

To understand the benefits of sacrificial shuttering, the affect of cost of speed restriction imposed during the construction of Super-Structure is added in the already calculated total cost vide table VA-VB . It is assumed that speed restriction of 20 KMPH for conventional shuttering of deck slab will be imposed for 45 days for reinforced concrete T-beam and 21 days for other three types of superstructure.

This time period will remain same for reinforced concrete T- beam and will be reduced to 07 days for sacrificial shuttering of deck slab for other three types. In Table No. VI the cost has been calculated for conventional shuttering only.

Table No. VII shows total cost for placement of super-structure including the cost of speed restriction imposed for combination of conventional shuttering for girder & sacrificial shuttering for deck slab.

TABLE VI

COMPOSITE COST STATEMENT CONSISTING OF CONSTRUCTION/FABRICATION COST (MATERIAL COST), PLACEMENT COST AND SPEED RESTRICTION COST ABOVE RAILWAY TRACK (CONVENTIONAL SHUTTERING) IN INDIAN RUPEES

No Type of Superstructure 20 Trains per day

35 Trains per day

50 Trains per day

65 Trains per day

80 Trains per day

1 RCC T-beam 14485354 21128511 27771674 34414831 41057995

2 RCC- I-beam 14116762 16680303 26253230 32321462 38389698

3 PSC I-Section 13328262 15891803 25464730 31532962 37601198

4 Composite Steel and RCC

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

122 TABLE VII

COMPOSITE COST STATEMENT CONSISTING OF CONSTRUCTION/FABRICATION COST (MATERIAL COST), PLACEMENT COST AND SPEED RESTRICTION COST ABOVE RAILWAY TRACK (COMBINATION OF SACRIFICIAL SHUTTERING) IN INDIAN RUPEES

No Type of Superstructure 20 Trains per day

35 Trains per day

50 Trains per day

65 Trains per day

80 Trains per day

1 RCC T-beam 14485354 21128511 27771674 34414831 41057995

2 RCC- I-beam 12056306 13446706 21846491 26741583 31636675

3 PSC I-Section 11252956 12643356 21043141 25938233 30833325

4 Composite Steel and RCC

Girder 9244888 12703806 16162725 19621643 23080562

The total cost for the reinforced concrete T- beam remains same in table VI & VII, because caste-in-situ construction of reinforced concrete T- beam considered with conventional shuttering only. There will be no advantage of using sacrificial shuttering in this case, because speed restriction will remain in place due to the erection of staging along the track for support of cast-in-situ beam.

E. Maintenance Cost

Among the four options used for comparison, only composite steel beam will require periodic painting and maintenance. All other three options are being constructed with cement concrete and will not require any periodic maintenance as concrete structures are considered free from maintenance. The normal frequency for painting of steel structure of the bridge is as taken as 6 years.

The total area of the steel composite girders for complete super structure is calculated as 437.0Sqm, and the cost per unit area of painting has been arrived at Rs. 115.0 per sqm as per the current prevailing rates. It is assumed that the bridge will be painted 16 times in its life span of 100 years. By considering 5% yearly inflation in the rates, the total cost of all the 16 cycles of paintings comes out to Rs. 14273117.

F. Effect of web-depth of girder on bridge approaches

It is clear from the table I, that the web-depth varies considerably in all four superstructure types. The maximum web depth is of reinforced concrete T-beam among all the four options. The extra cost required for more height of approaches due to increase in web depth in case of T-beam in comparison with all other three options is tabulated in table VIII.

TABLE VIII

EXTRA COST OF MATERIAL CONSUMED IN APPROACHES BY THE REINFORCED CONCRETE T-BEAM IN COMPARISON WITH OTHER OPTIONS DUE TO DIFFERENCE IN WEB-DEPTH.

No Cost details Reinforced cement

I-beam

Prestressed I-beam

Steel composite I-beam

1 Cost of Retaining wall

a. with Reinforced Earth wall 94500 144900 189000

b. with Reinforced Concrete wall 216000 331200 432000

2 Cost of Filling material 48600 74520 97200

3 Total cost with RE wall 143100 219420 286200

[image:10.612.43.567.168.275.2] [image:10.612.39.573.525.676.2]
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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

123

VI. CONCLUSIONS

The conclusions are drawn for different ground conditions, different shuttering types, different shapes and their effects on approaches. The lifecycle cost of superstructure considering the initial capital cost and periodic maintenance cost is considered for evaluating various options.

A. Normal ground conditions 1. Considering total capital cost

From Table III, it is clear that the total cost of superstructure consisting of fabrication/casting cost (Material Cost ) and placement cost in normal ground conditions using conventional shuttering is minimum for reinforced cement concrete-T beam and the total cost using combination of conventional and sacrificial shuttering is also minimum for reinforced cement concrete-T beam among the four options used for comparison.

In normal ground conditions, the total superstructure cost with sacrificial shuttering is higher than the total cost with conventional shuttering. However, the difference in both the cases is small, but where the time is essence for early completion of the project; the sacrificial shuttering may proves to be better choice.

2. Considering maintenance cost(Life Cycle Cost)

Considering the periodic maintenance requirement, the composite steel I-beam becomes the costliest option and reinforced concrete T beam is again the most economical option among all the four superstructure types.

3. Considering the effects on approaches

After adding the additional cost of approaches due to increase in the height of superstructure, the cost of superstructure with reinforced concrete T-beam and prestressed concrete I-beam is almost same subject to the condition that, approaches are built with reinforced earth walls. If the approaches are built with reinforced concrete retaining wall then prestressed concrete I-beam is the most economical option.

B. Above railway track

1. Considering total capital cost

From Table V-A & V-B, it is clear that the total cost of superstructure consisting of fabrication/casting cost (Material Cost) and placement cost (launching cost including railway block Cost), using conventional shuttering as well as combination of conventional and sacrificial shuttering; is minimum for reinforced concrete-T beam among the four options used for comparison.

It is important to mention that the cost is considerably less in case of reinforced concreteT- beam being case-in-situ.

From table V-A & V-B, it is clear that among the options of pre-casted/pre-fabricated, the cost of Composite steel girder is lowest in both the cases, i.e. with conventional and with sacrificial shuttering. With increase in number of trains per day in the section the cost implication is increased considerably, but the Composite steel girder remains the cheapest. The reinforced concrete-I beam and pre-stressed concrete-concrete-I girders are costliest with little cost difference between them.

From table VI, it is clear that the total cost of superstructure consisting of fabrication/casting cost (Material Cost), placement cost (launching cost,railway block Cost and speed restriction cost), using conventional shuttering; the cost of Composite steel girder is lowest. With increase in no of trains per day in the section the cost implication is increased considerably, but the Composite steel girder remains the cheapest. The reinforced concrete-T beam is the costliest due to imposition of longer duration of speed restriction for casting of deck slab.

From table VII, it is clear that the total cost of superstructure consisting of fabrication/casting cost (Material Cost), placement cost( launching cost, railway block Cost and speed restriction cost), using combination of conventional and sacrificial shuttering; the cost of Composite steel girder is lowest. With increase in no of trains per day in the section the cost implication is increased considerably, but the Composite steel girder remains the cheapest. The reinforced concrete T- beam is the costliest due to imposition of longer duration of speed restriction for casting of deck slab.

2.Considering maintenance cost (life cycle cost)

Considering the periodic maintenance requirement, the composite steel I-beam becomes the costliest option and prestressed concrete I-beam comes out most economical option among all the four superstructure types.

3.Considering the effects on approaches

After adding the additional cost of approaches due to increase in the height of superstructure, the cost of superstructure with prestressed concrete I-beam is most economical with any type of retaining wall in approaches.

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International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 5, Issue 7, July 2015)

124 The advantage of sacrificial shuttering comes into picture when the cost implication of the speed restriction is also combined with the traffic block cost.

The effect of sacrificial shuttering is more pronounced when the numbers of trains in a section are high. The difference in cost for conventional and combination of sacrificial shuttering for prestressed I-beam is Rs. 2075300 with 20 trains in a section and this difference increases to Rs. 6767873 with 80 trains in a section.

Fig:9- variation in cost of superstructure with Conventional and Combination of sacrificial shuttering due to increase in frequency of

trains in section.

Overall the prestressed concrete I-beam proves to be most economical in all the conditions studied for arriving at best solution for the selection of superstructure for 20m span.

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[12] Saxena Amit and Maru Dr. Savitri, Comparative Study of the Analysis and Design of T-Beam Girder and Box Girder Supersructure, International Journal of Research in Engineering & Advanced Technology, April-May 2013, Vol-I, Issue 2.

[13] Design criteria for Pre-stressed concrete road bridges (Post-tensioned Concrete), IRC: 18-2000, The Indian Road Congress. [14] Standard Specifications and code of practice for road bridges, IRC:

6-2000, The Indian Road Congress.

[15] Code of practice for Pre-stressed concrete, IS: 1343-1980, Bureau of Indian Standards.

[16] Standard Specifications and code of practice for road bridges, section III-cement concrete (plain & reinforced), IRC: 21-2000, The Indian Road Congress.

[17] Standard Specifications and code of practice for road bridges, section IV- composite construction (first revision), IRC: 22-1986, The Indian Road Congress.

Figure

Fig. 3: Shear force variation along the span of beam under live load.
TABLE VB  ABRICATION
TABLE XTRA COST OF MATERIAL CONSUMED IN APPROACHES BY THE REINFORCED CONCRETE DIFFERENCE IN WEBVIII  T-BEAM IN COMPARISON WITH OTHER OPTIONS DUE TO -DEPTH

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