Structural Engg_Lec_19_Introduction to Bridge Engineering

Course # CE-5154

03 Credit Hours

Lecture # 02+03

19 & 27-Mar-2011

Introduction to Bridge Engineering

Department of Civil Engineering,

University of Engineering & Technology, Peshawar, Pakistan

CE-5154 Intro. to Bridge Engg.Lecture # 02 Email: [email protected] 2Dr. Syed Mohammad Ali

Sequence of Presentation

What is Bridge?

Roles & Responsibilities of a Bridge Engineer

Types of Bridges & Bridge Components

Bridge Failure


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 ~6,000 bridges on Natl. Highways ~Rs. 400-700 bn asset (NHA bridges only)

NHA budget FY 2009-10 was ~Rs.39.9 bn

(6.2% of PSDP Rs.646 bn) [Min. of Fin. 2009]

4411,000

500

3,500

7031,262

631

4,419

0

1,000

2,000

3,000

4,000

5,000

New Khiarabad Brdg. (2003)

Indus Brdg M1 (2007)

Kabul River Brdg M1 (2007)

Northern Bypass (2007)

Co

st in

Mill

ion

sP

KR

Value in Respective Year

NPV 2011


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



Broad Classification of Bridges

Bridge Classification

Material

Steel Concrete Wood Hybrid Stone/Brick

Usage

Pedestrian Highway, Railroad, Aircraft

Structural Form

Slab Girder Truss Arch Suspension

Cable-Stayed

Type Traffic

Highway, Pedestrian, trains, transit, others

Span

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 150-500 feet (50-150m)

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)*

*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.



Main Components

Girders

Guard Rails

Pier / column

Transom / Pier Cap

Diaphragms



Main Components

Guard Rails

Pier / column

Abutment

Abutment

Piles

Pile Cap



Main Components

Pile Cap

Piles



Main Components

Bearing Pad



Main Components

Multi-column Pier

Isolator / Base Isolator


Bridge Failures

Bridges do Fail!


Q & A

Thanks!

Structural Engg_Lec_19_Introduction to Bridge Engineering

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