Two Span Bridge

Koshy Varghese, Ph.D. Professor

Building Technology & Construction Management Department of Civil Engineering

I.I.T. Madras

Two Span Bridge Scheduling

Koshy Varghese IIT Madras

Learning Objectives

• General activities & operations for the two-span bridge exercise

• Initial estimate of duration of activities based on operation details

• Establishing predecessor relationships

This example is only for classroom discussion Intent is to illustrate some of the aspects to be considered for time planning. It is not a comprehensive procedure.


Pre-cast Piles

EAST WEST

Two Span Bridge- Example

Pre-cast Beams

Recall Discussion on Activities identified in Lecture -3


TWO SPAN BRIDGE Koshy Varghese IIT Madras

Pre-cast Piles

EAST ABUTMENT

WEST ABUTMENT

Two Span Bridge- Example

Pre-cast Beams

Define activities required to schedule this project


Two Span Bridge

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1

Cast Piles

2 Casting of beams

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4

EAST WEST

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14 15

1. Order & Deliver Piles 2. Cast Beams 3. Drive Piles East 4. Const East Pile Cap 5. Const E. Abutment 6. Drive Piles Centre 7. Const Centre Pile Cap

9. Drive Piles West 10. Const West Pile Cap 11. Const W. Abutment 12. Place Beams E. Span 13. Place Beams W. Span 14. Deck Slab East 15. Deck Slab West 16. Lay Roads 8. Const Centre Pier

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1. Order & Deliver Piles

Casting Operation

Stored Piles


1. Order & Deliver Piles - Duration

Standard sizes of prefabricated piles are available. No. Piles required is say East (4x3) + Center (2x3) + West (4x3) = 30 When should Order be placed ? Find Lead time for delivery. (Stock availability, Delivery to location)

What if the piles were cast on site ?

No. piles required (4x3) + (2x3) + (4x3) Operation Sequence: 1.0 Reinforcement Fabrication – 1 day 2.0 Casting Pile 2.1 Formwork Assembly – 1 day 2.2 Concrete pouring – ½ day 2.3 Form removal after – 1 day 2.4 Form removal time- ½ day Curing before usage – 21 days regular 2 days steam curing

Production Rate vs. based on No. Forms 1 1 pile in 3 days -> 90 days for 30 piles

2 2 piles in 3 days -> 45 days “

3 3 piles in 3 days -> 30 days “

What determines production rate ?

Casting Yard Set-up 10 days


2. Cast Beams

Casting Operation

Transport


2. Cast Beams - Duration

Beams are prefabricated in casting yard set-up on site. No. Beams required is say 3 for each span- total = 6

No. beams required = 3 + 3 Operation Sequence: 1.0 Reinforcement Fabrication – 2 days 2.0 Casting Beam 2.1 Formwork Assembly – 1 day 2.2 Concrete pouring – 1 day 2.3 Form removal after – 1 day 2.4 Form removal time- 1 day Curing before usage – 28 (14) days regular 3 days steam curing Assume reinforcement fabrication is done in parallel

Production Rate – based on No. Forms/Beds No. Sets of forms 1 1 beam in 4 days -> 24 days for 6

beams

2 2 beams in 4 days -> 12 days “

3 3 beams in 4 days -> 8 days “

What production rate is required ?

Total Duration= 2 +14 (1st set); Day 6+14 (2ndset)?

Assume 3 sets of forms:


3, 6 & 9. Drive Piles

Pile Driving Operation


3, 6 & 9. Drive Piles - Duration

Driving Rate depends on Soil type and Rig Characteristics

Assume 1 day / pile

East & West Piles – 12 days Each Side

Center Piles – 6 days


4, 7 & 10. Construct Pile Cap Koshy Varghese IIT Madras

4, 7 & 10. Construct Pile Cap - Duration

East & West Pile Cap - 12 piles Operation Sequence: 1.0 Excavation & PCC Bed– 1 day 2.0 Chipping 1 day 3.0 Reinforcement 1 day 4.0 Formwork 1 day 5.0 Concreting 1 day 6.0 Form removal after 1 day 7.0 Form Removal 1 day 8.0 Backfill 1 day Curing before usage – 3 days regular curing Total duration for East & West Pile Cap= 5days + 3days=8 days

Center Pile Cap - 6 piles Operation Sequence: 1.0 Excavation & PCC Bed– 1 day 2.0 Chipping 1/2 day 3.0 Reinforcement 1/2 day 4.0 Formwork 1 day 5.0 Concreting 1/2 day 6.0 Form removal after 1 day 7.0 Form Removal 1/2 day 8.0 Backfill 1/2 day Curing before usage – 3 days regular curing Total duration for East & West Pile Cap= 4 days+ 3days= 7 days


5 & 11. Construct Abutments Koshy Varghese IIT Madras

5 & 11. Construct Abutments - Duration

Assume Abutment is done in 2 stages

Operation Sequence: (Stage-1)(Lower Level) 1.0 Reinforcement Erection – 3 days 2.0 Formwork Assembly – 3 days 3.0 Concrete pouring – 1 day 4.0 Form removal after – 1 day 5.0 Form removal time- 2 day Curing before next stage pour – 3 days

Operation Sequence: (Stage-2) (Higher Level) 1.0 Reinforcement Erection – 4 days 2.0 Formwork Assembly – 4 days 3.0 Concrete pouring – 1 day 4.0 Form removal after – 1 day 5.0 Form removal time- 2 days Abutment cap + Bearing Pad = 7 days

Duration = 10 (Stage-1) + 12 (Stage-2) + 7 (Cap +bearing pedestal) + 7 Curing

=36 days Each Abutment


8. Construct Centre Pier


8. Construct Centre Pier - Duration

Assume Pier is done in 2 stages + Pier cap and Bearing Pedestal

Operation Sequence: (Stage-1)(Lower Level) 1.0 Reinforcement Erection – 1 day 2.0 Formwork Assembly – 2 days 3.0 Concrete pouring – 1 day 4.0 Form removal after – 1 day 5.0 Form removal time- 1 day Curing before next stage pour – 3 days (?)

Operation Sequence: (Stage-2) (Higher Level) 1.0 Reinforcement Erection – 2 days 2.0 Formwork Assembly – 3 days 3.0 Concrete pouring – 1 day 4.0 Form removal after – 1 day 5.0 Form removal time- 1 day Curing before Pier cap – 3 days Pier cap + Bearing Pad – 5 days

Duration = 6 (Stage-1) + 8 Stage-2 upto form removal + 1 day (after stage 2) + 5 (Pier Cap Construction) + 7 days curing before loading

Pier cap etc = 1 days after Stage 2 + 5 days const + 28 days before Girder Placement

= 27 days


12 & 13 Place Beams Koshy Varghese IIT Madras

12 & 13 Place Beams- Duration

Depends on lifting & placing method & distance from fabrication yard Assume 1 day / girder

East & West girders placement – 3 days each side.

+

4 days for girder diaphragm

Total = 7 days each side.


14 & 15. Construct Deck Slab Koshy Varghese IIT Madras

14 & 15 Construct Deck Slab- Duration

Operation Sequence 1.0 Staging - 2 day 2.0 Formwork Assembly– 1 day 3.0 Reinforcement Erection – 2 days 4.0 Concrete pouring – 1 day 5.0 Form removal after – 7 day 6.0 Form removal time- 2 day Curing for 7 days Total = 15 days Each Side

Assume staging is done for each sides in 4 days


16. Lay road Koshy Varghese IIT Madras

16. Lay road - Duration

Operation Sequence 1.0 Earthwork (Filling/grading/rolling) 10 days (Each side) with stone pitching revetment etc 2.0 Blacktopping – 5 days. (Full length)

Total Duration = 20 + 5 = 25 days (No overlap is done)

Is overlap possible ? What is the saving in duration ?


Two Span Bridge – Activity-Duration-Predecessors

Draw Network. Do Network Analysis - Any Changes suggested ?


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No Resource Constraints

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Order/ Cast Piles

2 Casting of beams

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EAST WEST

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Discussion Points

What are the resources needed for each activity ? How does resource affect activity durations ? Which activities ? Should resource availability affect precedence relationship ? How can the duration of the project be reduced ?


To be continued……


Documents

Two Span Bridge