Cantilever Bridge

1. Analysis and Design of Cantilever Bridge
Image: Wikipedia7/13/2019 Vinayak Patil 1

2. Vinayak Patil
Contents
1. Introduction
2. General Features
3. Methods of Design
4. Design Sequence
5. Arrangement of Supports
6. Selection of Cross Section
7. Shear Variation
8. Articulation
9. Design of deck slab
10. Design of longitudinal girder
11. Construction
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3. Vinayak Patil
1. Introduction
• Balanced cantilever bridges are adopted for comparatively
longer spans where simply supported, continuous or rigid
frame type superstructures are found unsuitable. Simply
supported decks of any type having spans more than 20 to
25 m. require comparatively greater depths and therefore,
become uneconomical.
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4. 2. General Features
• Partially Continuous Structures
• Reduction of Moments
• Not Affected by Settlement of Supports
• Odd spans
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5. 3. Method of Design
• Working Stress Method
 IRC 21:2000
• Limit State Method
 IRC 21:2001
• Using Softwares
 STAAD
 Csi Bridge
 MIDAS etc
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6. 4. Design Sequence
• Arrangement of Support
• Design of Deck slab
• Design of longitudinal Girder
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7. 5. Arrangement of Support
• To get the most economical design, the proportioning of the
members should be such that the sections at mid-span and at
support satisfy both the structural and architectural
requirements and at the same time require minimum quantity
of materials.
• Typical 5 Span system
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8. 6. Selection of Section
• Girder of maximum depth at support and reducing towards center are used
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9. Vinayak Patil
7. Shear Variation
• Due to change in C/S
• Given by
S = (M/h) tan
Where,
S = Shear at section
M = Moment at Section
h = Depth of Section
 = Angle made by tangent to curve with horizontal
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10. 8. Articulation
• The junction of cantilever and simply supported span is known as ARTICULATION
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11. 9. Design of Deck Slab
• Load calculation
• Determination of maximum moment
• Effective depth calculation
• Reinforcement calculation
• Check for shear (Table 12B of IRC : 21-2000)
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12. 10. Design of Longitudinal Girder
• Preliminary Design
1. Design of cantilever section
2. Design of Mid-section
• SFD and BMD of section
• Reinforcement Design
• Design of Articulation
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13. Piyush Santhalia
11. Construction
Sequence
Balanced Cantilever Bridge : Delhi Metro Phase III
60 + 60m span7/13/2019 Vinayak Patil 13

14. 9. Construction Sequence
Casting of Stitch at Mid-
span using suspender.
Balanced Cantilever Bridge :
Delhi Metro Phase III
(34 + 60 + 34m)
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15. THANK YOU
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