002 basic 04-03-14

Course # CE-5120

03 Credit Hours

Lecture # 02

Introduction to Bridge Engineering

Bridge EngineeringLecture # 02 Email: ali@civionics.pk04-Apr-2014 2Dr. Syed Mohammad Ali

Sequence of Presentation

• What is Bridge?

• Roles & Responsibilities of a Bridge Engineer

• Types of Bridges & Bridge Components

• Bridge Failures

What is Bridge?

• A1.2

• Bridge is a structure that has the heaviest responsibility in carrying a free flow of traffic

• Width of the bridge (number of lanes) dictates the traffic volume of a road segment

• The Load Carrying Capacity of a bridge

would dictate the weight of truck allowed

to cross the bridge (load limits can be

posted )

• Thus bridge controls both capacities:– The volume and

– Weight of the traffic of the transportation system.

Golden Gate Bridge California

What is Bridge?

• The most costly component of Transportation network

• Currently ~8,000 bridges on Natl. Highways– ~Rs. 400-1,000 bn asset (NHA bridges only)

– NHA budget FY 2013-14 was ~Rs.63.04 bn

– (5.5 % of PSDP Rs.1,155 bn) [http://www.pc.gov.pk]

4411,000

8371,504

01,0002,0003,0004,0005,0006,000

New KhiarabadBrdg. (2003)

Indus Brdg M1(2007)

Kabul RiverBrdg M1 (2007)

Northernbypass Karachi

Value in Respective Year

NPV 2014

Roles and Responsibilities of a Bridge Engineer

• Safe and Economical Design

• The bridge engineer is often involved with several or

all aspects of bridge planning, design, & management

• This situation is not typical in the building

Architect usually heads a team (architects, civil,

structural, mechanical, & electrical engineers)

• In the bridge engineering, the bridge engineer works

closely with other civil engineers (roadway alignment

and design)

• After the alignment is determined, the engineer

often controls the bridge type, aesthetics, and

technical details

• The bridge engineer has significant control over – The design,

– construction, and

– maintenance processes

Sher Shah Bridge Collapse 2007Karachi

Hen-Shen Expwy Japan , Kobe EQ6.9 Mw, 1996

Types of Bridges & Bridge Components

• Broad Classification of Bridges

Bridge Classification

Material

Steel Concrete Wood Hybrid Stone/Brick

Pedestrian Highway, Railroad, Aircraft

Structural Form

Slab Girder Truss Arch Suspension

Cable-Stayed

Type Traffic

Highway, Pedestrian, trains, transit, others

Short , Medium & Long

Classification According to Traffic

• Classification as per Structural Form

– Girder Bridge

– Arch Bridge

– Truss Bridge

– Suspension Bridge

– Cable-Stayed Bridges

• Girder Bridge

– Most commonly constructed

– Usually used for Short and Medium spans (up to 50 m)

– Structural Action is to carry load in Shear and Flexural

– Economical and long lasting solution for vast majority of bridges

– Decks and girder usually act together to support the entire load in highway bridges

• Girder Bridge

• Typical Deck Super-structures Table A4.6.2.2.1-1

• Span lengths for various types of Super-structures

Ayub Bridge Havalian, KKH

• Arch Bridges

• Arch action reduces flexural stresses (that is Tensile Stresses )

• Arch is predominantly a compression member. Buckling needs attention.

• Can be economical as compared to equivalent straight simply supported girder or truss bridge

• Suitable site would be Valley which has strong foundations on a rocks

• Arch Bridges

• Generally conventional curved arch rib has high fabrication & erection costs

• Erection easiest for Cantilever Arch and most difficult for Tied Arch

Bridge in Neelum Valley, AJKIs it an Arch?

Tied Arch

Wooden Arch Bridge, Rocky Mountains, Colorado, USA

• Arch Bridges

• Truss Bridges

• The primary member forces are axial tension or compression

• The open web system allows deep girders than for an equivalent solid web girder

• This may lead to economy in material and reduced dead weight

• The cost of fabrication and maintenance is high

• The truss is attractive choice in suspension bridges due to its superior aerodynamic behavior

• Truss results in light structure that can be assembled member by member using small lifting capacity equipment

• Truss Bridges

• Suspension Bridges

– Major element is a flexible cable, that transfers the loads to the towers and anchorage

– This cable is from High Strength wires

– The deck is hung from the cable by Hangers also of high strength ropes (in tension)

– Suitable for very long spans

– Expensive to build and maintain

Totakan (near Swat)Thakot Bridge over River Indus Golden Gate Bridge California

• Cable-Stayed Bridges

– In comparison to suspension bridge, the cables are straight rather than curved. Therefore the stiffness is greater

– The cables are anchored to the deck

– All individual cables are shorter than full length of the superstructure.

– Economical over 100-350m, some bridges are as long as 800m

– No such bridge built in Pakistan as yet but one is in construction phase in AJK, work on one started in Muzaffarabad, AJK

Naluchi, Muzaffarabad, AJk

• Classification with respect to Span

– Small Span Bridges up to 50 feet (15m)

– Medium Span Bridges up to 250 feet (75m)

– Large Span Bridges up to 500 feet (76-150m)

– Extra Large ( Long ) Span Bridges over 500 feet (150m)

• Small Span Bridges up to 50 feet (15m)

– Culverts

– Slab Bridges – 40 ft (12m)

– T-Beam Bridge – 30-60 ft (10-20m)

– Wood Beam Bridge

_________________

• Medium Span Bridges up to 250 feet (75m)

– Pre-cast Concrete Box Beam Bridge – 30-150 ft (10-50m)

– Rolled Steel Beam Bridge up to 100 ft (30 m)

– Pre-cast Concrete I-Beam Bridge – 30-150 ft (10-50m)

– Cast-in-place RC Box Girder Bridge (20-40 m)

– Composite Steel Box Girder

• Large Span Bridges 150-500 feet (50-150m)

– Composite Steel Plate Girder Bridge

– Cast-in-place Post-Tensioned concrete Box Girder

– Post-Tensioned Concrete Segmental Construction

– Concrete Arch and Steel Arch

• Extra Large ( Long ) Span Bridges over 500 feet (150m)

– Cable Stayed Bridge

– Suspension Bridge

• Structural Arrangement

• Bridge types can also be classified according to the location of the main structure elements relative to the surface on which the user travels:

– Main Structure Below the Deck Line

– Main Structure Above the Deck Line

– Main Structure coincides with the Deck Line

• Main Structure Below the Deck Line

– Arch Bridges

– Truss-Arch Bridges

• Main Structure Above the Deck Line

– Suspension Bridges

– Cable Stayed Bridges

– Through-Truss Bridges

• Main Structure coincides with the Deck Line

– Slab (solid and voided)

– T-Beam (cast-in-place)

– I-beam (pre-cast or pre-stressed)

– Wide-flange beam (composite & non- composite)

– Concrete Box (cast-in-place, segmental & pre-stressed)

– Steel Plate Girder (straight & haunched)

– Steel box (Orthotropic deck)*

• Main Structure coincides with the Deck Line

• *An orthotropic bridge or orthotropic deck is one whose deck typically comprises a structural steel deck plate stiffened either longitudinally or transversely, or in both directions. This allows the deck both to directly bear vehicular loads and to contribute to the bridge structure's overall load-bearing behavior. The orthotropic deck may be integral with or supported on a grid of deck framing members such as floor beams and girders.

• The same is also true of the concrete slab in a composite girder bridge, but the steel orthotropic deck is considerably lighter, and therefore allows longer span bridges to be more efficiently designed.

• Two Main Components of a Bridge

– Superstructure (above the bearing pads)• Beams or Main Load Carrying Elements

– Steel or concrete girders

– Segmental boxes

– Suspension or cable-stayed

– Trusses

• Deck –typically concrete

• Wearing Surface –bituminous or concrete

– Substructure (below the bearing pads)• Piers

• Abutments

• Main Components

Girders

Guard Rails

Pier / column / bent

Transom / Pier Cap

Diaphragms

• Super-structure (deck)

• Super- and Sub-structure

• Main Components

Guard Rails

Pier / column

Abutment

Pile Cap

• Main Components

Pile Cap

• Main Components

Multi-column Pier

• Substructure

• Bearings– AASHTO defines a bearing as “

“A structural device that transmits loads while facilitating translations and/or roration”

Bearing Pad

• Main Components

Isolator / Base Isolator

Thanks!

002 basic 04-03-14

bridge controls

bridge type

bridge engineer safe

bridge load limits

bridge number of lanes

aspects of bridge planning

syed mohammad aliwhat

syed mohammad aliroles

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