bridges by span

015

BRIDGES-BY SPAN

CE 5154 Introduction to Bridge Engineering-RevisedCE 5154 Introduction to Bridge Engineering-Revised

http://www.cpi-team.com

http://www.cpi-team.com/

Science Art Religion Politics Scholarly Science Art Religion Politics Scholarly Articles For Mathematics and ProductivityArticles For Mathematics and Productivityhttp://www.twitlonger.com/show/n_1sp9pjo?new_post=trueMICROSOFT OneDrive PPT’s PDF’s MICROSOFT OneDrive PPT’s PDF’s BOOK LESSONS BOOK LESSONS Dr f Dejahang BSc CEng, BSc (Hons) Dr f Dejahang BSc CEng, BSc (Hons) Construction Mgmt, MSc, PhDConstruction Mgmt, MSc, PhD

http://www.twitlonger.com/show/n_1sp9pjo?new_post=true

http://www.twitlonger.com/show/n_1sp9pjo?new_post=true

BRIDGES

Discussion on Classification Discussion on Classification According To According To SPANSPAN

BRIDGES

Extra Large (Long) Span Extra Large (Long) Span Bridges(Over 150m)Bridges(Over 150m)

BRIDGES

Main Structure Below the Deck LineMain Structure Below the Deck Line

BRIDGES

Main Structure Coincides with Main Structure Coincides with the Deck Linethe Deck Line

Girder BridgeGirder Bridge

FACTORS CONSIDERED IN FACTORS CONSIDERED IN DECIDING BRIDGE TYPEDECIDING BRIDGE TYPE

BRIDGES

Geometric Conditions of the Geometric Conditions of the SiteSite


• Relatively high bridges with Relatively high bridges with larger spans over navigable larger spans over navigable waterways will require a waterways will require a different bridge type than different bridge type than one with medium spans one with medium spans crossing a flood plaincrossing a flood plain


• The site geometry will also The site geometry will also dictate how traffic can be dictate how traffic can be handled during construction, handled during construction, which is an important safety which is an important safety issue and must be issue and must be considered early in the considered early in the planning stageplanning stage

Subsurface conditions of the Subsurface conditions of the soilsoil

Subsurface conditions of the Subsurface conditions of the soilsoil

• The potential for seismic activity at a site The potential for seismic activity at a site should also be a part of the subsurface should also be a part of the subsurface investigation.investigation.

• If seismicity is high, the substructure If seismicity is high, the substructure details will change, affecting the details will change, affecting the superstructure loads as wellsuperstructure loads as well

• All of these conditions influence the choice All of these conditions influence the choice of substructure components which in turn of substructure components which in turn influence the choice of superstructureinfluence the choice of superstructure

Functional RequirementsFunctional Requirements

• Bridge must function to carry present and Bridge must function to carry present and future volumes of traffic.future volumes of traffic.

• Decisions must be made on the number of Decisions must be made on the number of lanes of traffic, inclusion of sidewalks lanes of traffic, inclusion of sidewalks and/or bike paths, whether width of the and/or bike paths, whether width of the bridge deck should include medians, bridge deck should include medians, drainage of the surface waters, snow drainage of the surface waters, snow removal, and future wearing surface.removal, and future wearing surface.


For Example: For Example: In the case of stream and flood In the case of stream and flood plain crossings, the bridge must plain crossings, the bridge must continue to function during periods continue to function during periods of high water and not impose a of high water and not impose a severe constriction or obstruction severe constriction or obstruction to the flow of water or debris.to the flow of water or debris.


• Satisfaction of these functional Satisfaction of these functional requirements will recommend some requirements will recommend some bridge types over others.bridge types over others.

• For Example: if future widening and For Example: if future widening and replacement of bridge decks is a replacement of bridge decks is a concern, multiple girder bridge types concern, multiple girder bridge types are preferred over concrete are preferred over concrete segmental box girders.segmental box girders.

Economic and ease of Economic and ease of maintenancemaintenance

• The initial cost and maintenance cost over The initial cost and maintenance cost over the life of the bridge govern when the life of the bridge govern when comparing the economics of different comparing the economics of different bridge types.bridge types.

• A general rule is that the bridge with the A general rule is that the bridge with the minimum number of spans, fewest deck minimum number of spans, fewest deck joints, and widest spacing of girders will be joints, and widest spacing of girders will be the most economical.the most economical.


For Example:For Example:(1) By reducing the number of spans (1) By reducing the number of spans in a bridge layout by one span, the in a bridge layout by one span, the construction cost of one pier is construction cost of one pier is eliminated.eliminated.(2) Deck joints are a high (2) Deck joints are a high maintenance cost item, so minimizing maintenance cost item, so minimizing their number will reduce the life cycle their number will reduce the life cycle cost of the bridge.cost of the bridge.


there is little cost increase in the deck there is little cost increase in the deck for wider spacing for girders and for wider spacing for girders and fewer girders means less cost fewer girders means less cost although at the “expense” of deeper although at the “expense” of deeper sections.sections.

• Generally, concrete structures require Generally, concrete structures require less maintenance than steel structure. less maintenance than steel structure.


• The cost and hazard of maintenance The cost and hazard of maintenance painting of steel structures should be painting of steel structures should be considered in type selection studies.considered in type selection studies.

• One effective way to reduce the One effective way to reduce the overall project cost is to allow overall project cost is to allow contractors to propose an alternative contractors to propose an alternative design or designs.design or designs.

Construction and Erection Construction and Erection ConsiderationsConsiderations

BRIDGES

Legal ConsiderationsLegal Considerations

BRIDGES

General Bridge ComponentsGeneral Bridge Components

BRIDGES

Components of a Components of a Girder bridge Girder bridge (Beam Bridge)(Beam Bridge)

Components of a Components of a Suspension Suspension BridgeBridge

Anchor BlockAnchor Block• Just looking at the figure we can compare Just looking at the figure we can compare

it as a dead man having no function of its it as a dead man having no function of its own other than its weight.own other than its weight.

Suspension girderSuspension girder• It is a girder built into a suspension bridge It is a girder built into a suspension bridge

to distribute the loads uniformly among the to distribute the loads uniformly among the suspenders and thus to reduce the local suspenders and thus to reduce the local deflections under concentrated loads.deflections under concentrated loads.

BRIDGES

SuspendersSuspenders• a vertical hanger in a suspension bridge a vertical hanger in a suspension bridge

by which the road is carried on the cablesby which the road is carried on the cablesTowerTower• Towers transfers compression forces to Towers transfers compression forces to

the foundation through piers.the foundation through piers.

BRIDGES

SaddlesSaddles• A steel block over the towers of a A steel block over the towers of a

suspension bridge which acts as a bearing suspension bridge which acts as a bearing surface for the cable passing over it.surface for the cable passing over it.

CablesCables• Members that take tensile forces and Members that take tensile forces and

transmit it through saddles to towers and transmit it through saddles to towers and rest of the forces to anchorage block.rest of the forces to anchorage block.

CASE STUDY TO VISULAIZE THE IMPORTANCE CASE STUDY TO VISULAIZE THE IMPORTANCE OF BRIDGE SPECIFICATIONSOF BRIDGE SPECIFICATIONS

BRIDGES

ROLE OF A BRIDGE ROLE OF A BRIDGE ENGINEERENGINEER

The role of an engineer can The role of an engineer can be broadly classified in two be broadly classified in two major working major working environments.environments.

• Consultancy Environment Consultancy Environment • Contractor EnvironmentContractor Environment

Consultancy EnvironmentConsultancy EnvironmentMeeting the demand of clientsMeeting the demand of clientsNot compromising on quality Not compromising on quality control at the same time while control at the same time while remaining economical.remaining economical.Must work properly on factors Must work properly on factors such as environment of the such as environment of the location, traffic growth rate, location, traffic growth rate, population growth rate etc before population growth rate etc before designing.designing.

BRIDGES

Design should be flexible to Design should be flexible to the practical considerations.the practical considerations.Following the proper design Following the proper design specifications.specifications.Proper Management both off Proper Management both off site and on site.site and on site.

Contractor EnvironmentContractor Environment