Introduction to Bridges
2.
BRIDGE STRUCTURE TYPES AND COMPONENTS
Objectives
 know the different types of bridges that are located throughout
Alberta and their characteristics
 ability to identify the various components/parts that make up a
bridge and know how they function
Overhead #2 - Types of Bridges
 bridge is a structure spanning and affording passage over a river,
chasm, road or the like
 types are many and varied usually named after the type of main load
carrying members i.e. beams, trusses, slabs, etc.
 by definition culverts are also bridges
Overhead #3 - Culvert Types
 earliest rigid culverts were timber, now cast-in-place or precast
concrete
 now large concrete culverts used only in unusual circumstances
where flexible would not work
 flexible culverts are all corrugated galvanized steel
 small diameters 3 m or less are CSP (corrugated steel pipe) which are
fabricated as big tubes and connected circumferentially
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 larger diameter 3 m - 8 m or more are SPCSP (structural plate
corrugated steel pipe) these are fabricated from curved plates which
are bolted together in the field into a tubular shape
Overhead #4 - Girder Bridges
 girders/beams spanning between supports
 girder bridges are by far most common type of bridge
 spans vary from 6 m – 125 m
 material used may be timber, concrete or steel
 concrete most common for short span and steel predominates in
longer span
 before 1950’s all short spans were timber
Overhead #5 - Steel Girder Bridge
 fabricated in plants and shipped to site
 steel girders most often are an I-section either rolled or welded
 shorter spans are rolled up to 0.9 m deep, others are welded plates
 deck and curbs usually are field cast concrete
Overhead #6 - Steel Box Girder
 plant fabricated and shipped to site
 these are all welded from various thickness and widths of plate
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 bottom flange is a single thinner wide plate
 otherwise similar to other I-girder
 deck and curbs field cast concrete
Overhead #7 - Prestressed Concrete Girder
 concrete can easily be cast into any shape so there is a great variety in
the shape of concrete girders
 longer span will usually be some kind of I shape as shown
 deck and curbs field cast concrete
 girders are plant cast then shipped and erected on site
Overhead #8 - Concrete T Girder Bridge
 these bridges are all field cast monolithically
 girders are simple in X-section since forms are all built on site
 depth of girders usually varies so have a shallow arch shape
(attractive)
Overhead #9 - Flat Slab Bridge
 “girders” in this bridge become very thin and deck becomes thicker
to the extent that only a slab remains
 usually reinforced concrete
 short spans
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 only a few in province
Overhead #10 - Standard Prestressed Concrete Girder Beam
 these are relatively short span bridges, plant cast and stressed up to
14 m long
 called standard bridges, constructed and fabricated from standard
drawings
 relatively new design – first use in 70’s
 recognizable since box section flat on bottom
 lateral connections between girders
Overhead #11 - Standard Precast Concrete Girder Beam
 plant cast short span bridges 6 m - 8.5 m
 reinforced concrete, not prestressed
 all are U or channel shaped with down turned legs
 bolted lateral connection between girders, some not connected
 cheap low cost, short life, first used in 50’s
Overhead #12 - Timber Girder Bridge
 none have been built recently since only lower quality and smaller
size timber now available
 short span, 6 m and 8.5 m lengths
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 many replaced by reinforced concrete and metal culverts
 primarily on local roads now
Overhead #13 - Truss Bridge
 many relatively small steel components, assembled in the field
 components made from angles, plates or channels
 old technology
 way to create long spans with smaller light weight members
 spans 25 m – 100 m or more
 earliest long span bridges in province were steel trusses
 some timber trusses (rare)
Overhead #14 - Pony Truss Section
 shorter spans are pony trusses
 trusses on each side of roadway only (no overhead bracing)
Overhead #15 - Through Truss Section
 these have main load carrying trusses on each side with bracing over
the road was as well
 longer spans typically 38 m – 100 m
 last one built in province about 1970
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
Overhead #16 - Deck Truss (Elevation)
 similar to through truss except deck is placed on top
 longer spans 80 m - 120 m or longer
 advantages, no vertical or horizontal restrictions
 disadvantage, requires a higher grade line
 truss no longer cost effective, high labour content in member
fabrication, large cranes now handle large sections more cheaply
Overhead #17 - Deck Truss Section
Overhead #18 - Rigid Frames
 can be steel or concrete
 rigid refers to connection between girders and legs (piers)
Overhead #19 - Rigid Frame Section
 X-section same as a steel girder bridge
 welded steel version is shown - looks good but expensive
 not very common
Overhead #20 - Span Types
Simple Spans
 most common since construction and analysis are most simple
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 not most efficient for load carrying ability
 have a gap or joint over each support
 higher maintenance
Overhead #21 - Simple Span
 bearing under each end or girder, one expansion and one fixed
 simple spans only in lower standard roads
 group of elements above bearings called superstructure
 below bearings is called substructure
Overhead #22 - Span Types
Continuous Spans
 more efficient for load carrying
 only have joints at end of bridge
Overhead #23 - Continuous Span
 where span is continuous, only one bearing rather than two on the
pier
 joint is eliminated which leads to less maintenance on bridge
 all major bridges are now continuous
Overhead #24 - Superstructure - Decks
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 carry the traffic and transfers load to main load carrying members
 exposed to most wear and tear, elements and traffic
 can be timber or concrete (rarely steel)
 highest maintenance cost
Overhead #25 - Superstructure - Curbs and Medians
 define travel lanes or limits of roadway on the bridge
 safety feature
 also called wheelguards when on trusses and made of timber or steel
 typically, curbs are made of concrete
Overhead #26 - Girder and Stringer Elements
 girder load carrying members in most cases have identifiable
elements
 flanges top and bottom elements
 web - thin vertical element
 diaphragms - connection between girders enhances load sharing and
lateral stability
 stiffener - provides lateral stability and increases load carrying
capacity
Overhead #27 - Truss Elements
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 top chord, heavy top member built up from rolled plates and
channels riveted or bolted
 bottom chord, lower longitudinal member usually an assembly of
plate and angles or channels depending on span length
 batter post - main member that transfers dead and live loads into
bearing
 vertical and diagonals - interior load carrying members that resist
vertical forces
Overhead #28 - Through Truss Elements
 stringers - support the deck
 floor beams - transfer deck loads into the trusses
 bracing - top and bottom laterals provide lateral stability and
stiffness
 bracing - sway or wind bracing provides strength to resist side wind
loads
 portal - main member connecting ends of top chords
Overhead #29 - Abutments
 substructure element at the end of the bridge that supports the
superstructure
 two types
- spill through
- retaining wall
 spill through most common
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 main elements are seat, backwall, wing wall, then piles or footing
Overhead #30 - Abutments
 retaining wall type reduces bridge length but more costly than spill
through
 retaining walls need to be massive therefore expensive and often
reduced cost of superstructure not enough to off-set
Overhead #31 - Piers
 these are the intermediate supports in or near the water
 two styles
- column type
- shaft type
 both styles have caps which support the bearing and girders
 column type has cap carried by 2 or more columns
 shaft type has a single solid element supporting the cap
Overhead #32 - Bearings
 types are fixed or expansion
 expansion bearings allow length changes due to temperature changes
 fixed ensure superstructure doesn’t move off the substructure
 materials
Belke Consulting Ltd.
- steel
- neoprene, rubber
- teflon
Overhead Notes
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Introduction to Bridges
- etc.
Overhead #33 - Bearings
 neoprene is a flexible material that allows rotation as well as some
minor longitudinal movement
 used in both expansion and fixed bearing
 economical maintenance free bearing
 steel expansion bearing are of a variety of styles
 rockers usually under older long spans
 rollers most often under trusses
 susceptible to corrosion and seizing up
Overhead #34 - Neoprene Bearing
 most common bearing now used has steel plates with a flexible
neoprene pad which has a teflon bonded surface sliding on a stainless
steel plate
Overhead #35 - Deck Joints
 spans the gap at the ends of the girder and deck where expansion and
contraction due to temperature changes is occurring
 like the bearings, there are fixed and expansion types
 fixed joints still have some movement caused by the girder deflections
called (articulation/rotation)
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
Overhead #36 - Deck Joints
 earlier joints were not watertight whereas today they are
 where bridges are very long and lots of movement required finger
plates are still used with appropriate drainage controls
Overhead #37 - Railing
 these provided for road user safety
 work together with curbs
 various types have been used
 such as flex beam, vertical bar or tube type
 sometimes concrete barriers used instead of railing with curbs
 materials used are steel, concrete, timber, aluminum, etc.
Overhead #38 - Culvert Types
 culverts are classified as rigid or flexible
 some variations where rigid and flexible are combined, such as ABC
(arch beam culvert) or CAB (concrete arch beam)
Overhead #39 - Rigid Culverts
 built from concrete or timber
 carry loads in a similar manner to bridges
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
Overhead #40 - Flexible Culverts
 these are corrugated metal culverts which are usually round or semiround (elliptical)
 flexible culverts range in size from very small to spans up to 15 m
Overhead #41 - Flexible Culverts CSP & SPCSP
 flexible culverts are fabricated from thin corrugated metal
 shape of the corrugation varies
 two styles
- small diameter is CSP
- section of pipe
- large diameter is SPCSP
- individual plates
Overhead #42 - Flexible Culvert Components
 barrel consisting of top, bottom and side plates
 usually a bevel at each end
 inlet and outlet
 end treatment - headwall
- shoulders, collars
- cut-off wall
 erosion protection or rock rip-rap
Overhead #43 - Rigid Culvert Components
Belke Consulting Ltd.
Overhead Notes
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Introduction to Bridges
 floor, roof and sidewall
 also inlet and outlet with bevels similar to flexible culvert
 rock rip-rap for erosion protection
Belke Consulting Ltd.
Overhead Notes
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