bridge construction zaqazeeq

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BRIDGE CONSTRUCTION

Bridge Construction

BYDr. Ahmed Abdel-Atty Gab-Allah

(Zagazig University)

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OUTLINE

1. INTRODUCTION.

2. BRIDGE CONSTRUCTION SYSTEMS.

3. BRIDGE CONSTRUCTION IN EGYPT.

Bridge Construction

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1. INTRODUCTION Importance of bridges.

Objective:Review latest bridge construction systems.

Scope:Highway bridges (90%).Prestressed concrete (most recent developments). Superstructures.

Bridge Construction

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2. BRIDGE CONSTRUCTION SYSTEMS Bridge Construction

Classification of Bridges: Purpose of Bridge: Highway bridges, railway bridges, foot

bridges, viaducts, elevated roads, etc.

Material of Construction: Timber, masonry, steel, reinforced concrete, prestressed concrete, etc.

Type of Superstructure: Slab, girder, arch, truss, rigid frame, etc. Type of Support: Simply supported, continuous, balanced

cantilever, cable-stayed, and suspension bridges.

Life of Bridge: Permanent and temporary bridges. Navigation Requirements: Fixed, movable, and overhead bridges. Span Length: Minor bridges (spans of 8 to 30 m), major bridges

(spans of 30 to 120 m), and long span bridges (spans above 120 m).

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2. BRIDGE CONSTRUCTION SYSTEMS Bridge Construction

Selection of Bridge Construction Systems:

Phases of Bridge Construction Projects: Surveying works, Soil investigation, Bridge layout planning, Selection of construction system, Design, and Construction (Construction-Oriented Design).

Alternative Bridge Designs: (Based on broad requirements specified by the owner).

Evaluation Criteria: Economy, Functional Requirements, Long-Term Performance, Construction and Design Requirements.

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Category Method of Construction Pre-tensioned Girder

Bridges (I- or T- Beam)

Erected with Cranes Erected with Launching

Girders

Post-tensioned Bridges

Cast in-situ: On Falsework Cantilever Segmental Span by Span

Precast: Incremental Launching Cantilever Segmental Span by Span

Cable-Stayed Bridges

Suspension Bridges

Incremental Launching Free Cantilever Balanced Cantilever

Bridge Construction Classification of Prestressed Concrete Bridges:

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System Code Description

A Precast, Prestressed Concrete Girders

B Incremental Launching Construction (Deck Pushing System)

C Cast-in-place, Balanced Cantilever Construction

D Precast Segmental, Balanced Cantilever Construction E Flying Shuttering System F Cable-Stayed Bridges G Suspension Bridges

Bridge Construction Latest Bridge Construction Systems:

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Sys. SiteCond.

Structure Level

Span Lengths Structure Depth

Other Aspects

A Inaccess. High Short(40 - 80 m)

Variable Sharp curvatures & superelevations.

B Inaccess. High Short(40 - 80 m)

Constant Straight or slightly-curved superstructures.

C Inaccess. High Long(up to 250 m)

Variable Crossing navigable waterways.

D Inaccess. High Long(up to 200 m)

Variable Crossing navigable waterways.

E Inaccess. High Short(40 70 m)

Variable Long viaducts with short spans.

F Inaccess. Very High Long(200 to 1,000 m)

Variable Crossing deep rivers, deep valleys, and mountains.

G Inaccess. Very High Very Long(500 to 2,000 m)

Variable Crossing deep rivers, deep valleys, and mountains.

Bridge Construction Suitability of Bridge Construction Systems:

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(A) Precast, Prestressed Concrete GirdersBridge Construction

System Concept: Utilization of precast, prestressed I- of T- girders, on top of

which a deck slab is cast. Girders are usually erected by means of mobile cranes. However, in case of inaccessible sites, a launching truss may

be used for this purpose.

10Launching Truss Schematic Diagram

Bridge Construction(A) Precast, Prestressed Concrete Girders

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Bridge Construction

Main System Components: Formwork: Forms for precast girders and formwork for deck slab.

(In case of T- girders, the flanges provide support for deck slab).

Gantry Cranes: Required at fabrication area (to carry girders to storage area and load them to trolleys, as well as to carry reinforcing cage to the form).

Trolleys: Two trolleys are usually required to transport girders to their spans. Specially designed rubber-tired vehicles may also be used for this purpose.

Launching Truss: A steel launching truss, equipped with two hoists, is required for erecting precast girders into their final positions.

(A) Precast, Prestressed Concrete Girders

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Bridge Construction

Construction Sequence: Casting of girders in a casting yard. Transporting girders to their spans by means of trolleys. Carrying girders by launching truss which is positioned over

respective span. Erecting girders into their final positions. Casting of deck slab. Moving launching truss forward to next span.

(A) Precast, Prestressed Concrete Girders

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Advantages: Economy, speed, and improved quality of mass production. Sharp curvatures & superelevations. Inaccessible sites. No interference with traffic.

Disadvantages: Casting yard, transport and erection equipment. Unsuitability for complex roadway geometry.

14Post-Tensioning of Girders


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(B) Incremental Launching (Deck Pushing)Bridge Construction

System Concept: Superstructure segments are cast in stationary formwork in a

casting yard located at one end of the bridge. After each segment is completed, the superstructure is pushed

forward to the other end of the bridge. In case of long superstructures, two casting yards (one at each

abutment) may be provided. In this case, the superstructure is pushed forward from both

abutments towards the center of the bridge.

16Incremental Launching Construction Schematic

Bridge Construction(B) Incremental Launching (Deck Pushing)

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Bridge Construction

Main System Components: Formwork: Rear half consists of forms for bottom slab and lower

part of webs, whereas front half of forms for the rest of box section.

Lifting and Pushing Equipment: Vertical hydraulic jacks are used to lift the bridge slightly at the abutment before each advance. Then, horizontal jacks are used to push the superstructure forward.

Temporary Bearing Blocks: Concrete blocks covered with thin stainless-steel sheets, constructed on top of all supports to reduce friction during launching operation. (Friction forces can be reduced to about 2% of vertical loading by feeding Teflon sheets between the bridge soffit and the top of stainless-steel sheets).

Launching Nose: Lightweight-steel girder, tied to front end of bridge girder to reduce cantilever moment during launching operations.

Intermediate Supports: Temporary supports may be provided between final piers to reduce bending moments during launching of superstructure. (Used when span-to-depth ratio > 17:1).

(B) Incremental Launching (Deck Pushing)

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Temporary Bearing Blocks


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Bridge Construction

Construction Sequence: Construction of casting yard(s), including formwork and

launching nose. Installation of pushing and/or pulling systems, and temporary

bearing blocks. Construction of superstructure. Disassembling of formwork, pushing and pulling systems, and

launching nose. Demolition of casting yard(s). Erection and stressing of post-tensioning cables in

longitudinal girders (webs). Replacement of temporary bearings by permanent bearings.


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Bridge Construction

Advantages: Inaccessible sites. Riding learning curve (Repetitive operations). No interference with traffic.

Disadvantages: Casting yard and pushing equipment. Increase in longitudinal prestressing (cantilever moments). Large labor force during launching. Unsuitability for complex roadway geometry.


21Construction Sequence


22Inc. Launching Construction


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(C) Cast-in-Place, Balanced Cantilever (Cantilever Carriage System)

Bridge Construction

System Concept: Superstructure is cast in segments in traveling forms. These forms are supported from one end on completed part of

superstructure, while the other end is a free cantilever. After concrete reaches required strength, forms are moved

forward and prepared for next segments.

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Bridge Construction

Main System Components: Form Travelers: Consist of main frames, guide rails, and

suspended platforms. Main frames run on upper guide rails and both frames and rails are attached to finished portion of superstructure by means of tie-down anchors. Forms are suspended from main frames; they can be stripped in a single operation by lowering main frames.

Pier Brackets: Used to provide support for the formwork of pier tables. If a pier is low, pier brackets may be supported on pier footing or directly on the ground. But if a pier is high, pier brackets are usually built out from the pier cap and pier shafts.

Local Bracings: Required for closure pours.

(C) Cast-in-Place, Balanced Cantilever

25Form Travelers - Schematic Diagram

Bridge Construction(C) Cast-in-Place, Balanced Cantilever

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Bridge Construction

Construction Sequence:(C) Cast-in-Place, Balanced Cantilever

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Bridge Construction

Construction Sequence (Contd.):(C) Cast-in-Place, Balanced Cantilever

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Cantilever Carriage System Closure Pour

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Bridge Construction

Advantages: Inaccessible sites. Long navigation channels. No interference with traffic or navigation. High labor efficiency.

Disadvantages: Special equipment and skilled labor. High precision required. Increase in reinforcement (cantilever moments). Limited length of segments. Low construction rate.

(C) Cast-in-Place, Balanced Cantilever

31Cantilever Carriage Construction


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(D) Precast Segmental, Balanced CantileverBridge Construction

System Concept: Superstructure is precast and prestressed in segments in a

fabrication area. Segments are then transported to bridge site, where they are

erected into their final positions.

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Erection Procedure

Bridge Construction(D) Precast Segmental, Balanced Cantilever

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Erection Procedure (Contd.)


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Bridge Construction

Main System Components: Formwork: Consists of a rigid outer shuttering and a hydraulically

operated collapsible inner shuttering. Inner shuttering can be completely removed during demoulding.

Transport Equipment: Precast segments are normally transported to the site by trailers. Segments should be of transportable size and weight.

Erection Equipment: A variety of erection equipment types can be used (such as truck cranes, crawler cranes, floating cranes, launching girders, cableways, etc.). However, a launching truss equipped with hoists is commonly used.

(D) Precast Segmental, Balanced Cantilever

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Bridge Construction

Fabrication of Precast Segments: To achieve a perfect fit between the ends of adjacent segments,

each segment is cast against the end face of the preceding one. (This is called Match-Casting of segments). Segments are then erected in the same order in which they

were cast. An epoxy resin (about 0.8 mm thick) is normally applied to

the match-cast contact surface. It serves as a bonding and leveling agent that transfers the shear and bending stresses to the adjacent segment. Shear keys are usually provided in each web of the segments

to handle erection stresses prior to the epoxy achieving final strength.


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Bridge Construction

Erection of Precast Segments: Precast segments are picked from transport trailer and

launched to their spans by means of launching truss. They are then lowered to their level where epoxy resin is

applied to the contact surface with the previously erected segments. They are finally tied to previously erected segments by post-

tensioning cables. Segments are erected on either sides of the pier alternatively

(to maintain balanced cantilevers, which will minimize the out-of-balance moment at the pier). After the two cantilevers reach mid-span, the launching truss

is moved forward to next span, where it will be ready for erecting another pair of balanced cantilevers.


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Bridge Construction

Advantages: Economy, speed, and improved quality of mass production. No interference with traffic or navigation. Low labor requirement for both fabrication and erection

operations. Adaptability to curvatures and superelevation.

Disadvantages: Casting yard, transport and erection equipment. High precision required. Increase in reinforcement (cantilever moments).


40Precast Segmental Construction


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(E) Spanwise Construction Using Stepping Formwork (Flying Shuttering System)

Bridge Construction

System Concept: Entire span is cast in place in stepping formwork (flying

shuttering), supported on specially designed and fabricated steel trusses extending over the piers. After completion of the span, form trusses carrying the

formwork are moved forward to next span.

42Stepping Shuttering Construction Schematic Diagram

Bridge Construction(E) Flying Shuttering System

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Bridge Construction

Main System Components: Stepping Formwork: Made of steel panels. Outer formwork is

supported by steel trusses, whereas inner formwork rolls forward on rails within the box section.

Form Trusses: Two longitudinal steel trusses are erected beneath the two side cantilevers of the box girder. They are designed to carry the forms of entire span.

Support Frames (or Pier Brackets): Erected on top of piers to support form trusses. Steel rollers are usually used at support frames to facilitate launching of trusses.

Hydraulic Jacks: Used for advancing form trusses. They may be installed at end of trusses, at next pier, or at finished portion of the bridge.

Intermediate Supports: In case of long spans, intermediate supports for the trusses may be used.

(E) Flying Shuttering System

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Bridge Construction

Construction Sequence: Erection of support frames. Erection of form trusses and outer formwork. Concreting of the box girder floor. Erection of inner formwork. Concreting of webs and top slab at one pour. Partial prestressing of longitudinal cables. Opening the stepping shuttering, and advancing form trusses

and stepping shuttering to next span using hydraulic jacks. Preparation of stepping shuttering to cast the next span. Final prestressing of cables after concreting of all spans, to

make the whole bridge continuous.


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Bridge Construction

Advantages: Long viaducts with short spans. No interference with traffic. High construction progress rate.

Disadvantages: Special equipment. Unsuitability for long spans.


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Construction Sequence:Concreting Phase and Advancing Phase


47Flying Shuttering Details


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Bridge Construction

System Concept: The superstructure is supported at one or more points by

high-tensile steel cables, extending from support towers and connected directly to the deck.

(F) Cable-Stayed Bridges

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Longitudinal:(a) Radiating(b) Harp(c) Fan(d) Star

Transverse:(a) Single Plane Vertical(b) Single Plane - Vertical/Lateral(c) Double Plane Vertical(d) Double Plane - Sloping

Cable Arrangements:

Bridge Construction

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Bridge Construction

Construction Methods: The selection of appropriate construction method depends on

many factors (stiffness of pylon, cable anchorage system, possibility of installing temporary supports, maximum length of unsupported spans permitted by design, and ease of transporting materials). Balanced cantilever construction is probably the most

favorable construction method for modern cable-stayed bridges. However, other construction methods can also be used [e.g,

Incremental Launching (Deck Pushing) and Free Cantilever Construction].


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Bridge Construction

Stay Technology: Cables(F) Cable-Stayed Bridges

Types of Stay Cables: (a) Parallel-Bar; (b) Parallel-Wire;(c) Stranded; (d) Locked-Coil

(a) (b)

(c) (d)

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Bridge Construction

Stay Technology: Anchorages(F) Cable-Stayed Bridges

Anchorage System for Parallel-Wire Cables

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Bridge Construction

Stay Technology:(F) Cable-Stayed Bridges

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Bridge Construction

Advantages: High clearance for traffic or navigation. Suitability for long spans. Less material quantities (smaller depths).

Disadvantages: High risks involved in bridge construction. High tech. required (very long span lengths). High degree of control required on quality, time and budget.


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Balanced Cantilever(Cast-in-Place)

Free Cantilever

Construction Systems: Balanced Cantilever. Free Cantilever. Deck pushing.

Bridge Construction(F) Cable-Stayed Bridges

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Bridge Construction(G) Suspension Bridges System Concept: The superstructure is supported by steel suspenders (vertical

hangers) attached to main cables that are stung over the support towers in the form of a catenary.

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Bridge Construction(G) Suspension Bridges

Construction Methods: Most construction methods for cable-stayed bridges are still

applicable for suspension bridges. However, the suspension cable technology is different from the

stay cable technology, particularly the anchorage of main cables, and the connections of vertical hangers to the main cables.

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Bridge Construction

Construction Sequence:

(G) Suspension Bridges

1. Construction of towers and precasting of superstructure segments.

2. Erection of main cables. Strands are pulled by winches and erected individually using specialized equipment.

3. Installation of cable clamps and hanger rods using cranes.4. Transporting superstructure segments below their final

position on barges.5. Erection of segments using erection equipment (erection

girders, for example).

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Bridge Construction

Construction Sequence: (Contd.)6. Jacking-up of each segment prior to erection of hanger

bars.7. Erection of hanger bars and their adjustment to

predetermined lengths to bring the segments into alignment.8. Interconnection of superstructure segments.9. Cambering the superstructure upwards by controlled

adjustment of hangers before casting the deck.10. Bringing the deck to its final level through a final set of

hanger adjustments.

(G) Suspension Bridges

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Bridge Construction(G) Suspension Bridges

Advantages: High clearance for traffic or navigation. Suitability for very long spans. Less material quantities (smaller depths).

Disadvantages: High risks involved in bridge construction. High tech. required (very long span lengths). High degree of control required on quality, time and budget.

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3. BRIDGE CONSTRUCTION IN EGYPT Major Bridge Projects in EgyptSys. Major Applications Span Lengths

(m)Comp.Date

A 6th of October Bridge (Ramsis/Ghamra). Ring Road 9-D Bridge.

33 4040

19881998

B Zamalek Elevated Road. Dessouk Overhead Bridge.

31@25, [email protected], [email protected], 5@40, 34

19861987

C Al-Giza New Bridge. 6th of October Bridge. Abou El-Ela Bridge. Rod El-Farag Bridge. New Benha Bridge. Al-Warrak Bridge

104, 2@69110, 2@100, 2@70

115, 2@69130, 2@75120, 2@69120, 2@60

196919761986199019902000

D Has Not Been AppliedE 6th of October Br. (Ghamra/ Autostrad).

Suez Canal Bridge, Approach Spans.4240

19982001

F 6th of October Br.(Ghamra/Autostrad). Suez Canal Bridge, Main Spans.

133 (66.5 in each side)404, 2@163

19982001

G Has Not Been Applied

Bridge Construction

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Bridge Construction Systems Applicable for Different Site Conditions in Egypt

# Site Conditions System Code System Description

I Under Running Traffic

A B E

Precast concrete girders. Incremental launching. Flying shuttering.

II Across Navigable Waterways

C D F

Cantilever carriage. Precast segmental construction. Cable-stayed bridges.

III Deep Waterways and Mountains F G

Cable-stayed br. (up to 1000 m). Suspension bridges (> 1,000 m).

IV At Accessible Sites* A* B* E*

Precast concrete girders. Incremental launching. Flying shuttering.

Bridge Construction

* May be feasible for accessible sites, particularly for very high superstructures (high approach spans and viaducts).

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Bridge Construction

bridge construction zaqazeeq

Documents

material of construction

purpose of bridge

bridge construction31

life of bridge

bridge construction42

highway bridges

foot bridges

railway bridges