BRIDGE

CONSTRUCTION
BEQ2173
Lecture
contents 01 Introduction

02 Bridge Structure Components

03 Types of Bridge
Introduction
Bridge
Bridge
❑ A bridge is a structure built to span physical
obstacles without closing the way underneath
such as a body of water, valley, or road, for the
purpose of providing passage over the obstacle.

❑ Generally bridges carry a road or railway across a

natural or artificial obstacle such as, a river, canal
or another railway or another road.

❑ The traffic that uses a bridge may include:

• Pedestrian or cycle traffic
• Vehicular or rail traffic
• Water/gas pipes
• A combination of all the above
Function of Bridge
❑ A bridge has to carry a service (which may be
highway or railway traffic, afoot path, public utilities,
etc.) over an obstacle (which may be another road
or railway, a river, a valley, etc.) and to transfer the
loads from the service to the foundations at ground
level.

❑ Different types of bridge has their own function,

design and method of construction.
Classification of Bridge
❑ According to form (or) type of superstructures:
o Arch bridge
o Truss bridge
o Cable stayed (or) suspended bridge
o Beam Bridge

❑ According to material of construction of

superstructure:
o Timber bridge
o Steel bridge
o Composite bridge
o Concrete bridge
 Classification of Bridge
❑ According to function:
o Pedestrian bridge
o Highway bridge
o Viaduct(road or railway over a valley or
river)
o Road-cum-rail or pipe line bridge

❑ According to the position of the bridge floor

relative to superstructures
o Deck through bridge
o Half through or suspension bridge

❑ According to method of connection of different

part of superstructures
o Pinned connection bridge
o Riveted connection bridge
o Welded connection bridge
Bridge Structure
Substructure & Superstructure components
Typical Bridge Components

Components:

1‐Deck and Overpass

2‐Girder
3‐Bearing
4‐Pedestal
5‐Footing
6‐Piles
7‐Underpass
8‐Embakment
9‐Live Loading
Bridge Superstructure
Bridge Superstructure
Types of Bridge Superstructure

❑There are various types of bridge

superstructure which include:

o Steel Superstructure
o Concrete Superstructure
o Timber Superstructure
o Secondary members
Bridge Superstructure
Steel Superstructures

❑ Steel has the advantage of lighter weight and

more rapid construction. Steel also lends itself
well to prefabrication at the factory and reduces
the amount of field labour for operations. Steel
primary members come in a variety of types,
some of which are as following:

o Rolled Beam
o Rolled Beam with Cover Plate
o Plate Girder
o Box Girder
Bridge Superstructure
Steel Superstructures – Rolled Beam
❑ A steel girder that has been formed by hot-rolling.
Wide-flange variety is the most common type of
rolled beam used as primary member.

Steel Superstructures – Rolled Beam

With Cover Plate
❑ To maintain an economy material, rolled beams are
equipped with a rectangular plate or cover plate at
the bottom of flange. The purpose of having the
cover plate to increase the ability of stringer to
resist flexure without using larger rolled beam..
Bridge Superstructure
Steel Superstructures – Plate Girder
❑ Has an I shape cross section. The girder is
constructed from steel plate elements that are
connected with weld, bolts or rivets rather than
being hot-rolled. Span lengths can become larger
when using plate girder as compared to rolled
beams.

Steel Superstructures – Box Girder

❑ Is a form of plate girder that combines two girders
into a single unit. It can be in a form of closed-box
or open-box. Open-box is usually more economical
than closed-box girders.
Bridge Superstructure
Concrete Superstructure – Concrete Superstructure –
Pre-stressed Concrete Box Girder
Girder
❑ Box girders are good at resisting the
❑ It can be pre-tensioned or effects of torsion and typically do not
posttensioned. require bracing elements.
❑ Pre-stressed concrete girders come ❑ It can be built in segments, can be
in a variety cross-section geometry. pre-cast and cast in-situ and have
The pre-tensioning strands are variable sections.
dependent on the length of span and ❑ Box girders are suitable for large
type of loading the structure is span lengths.
subjected to.
Pre-stressed Concrete Concrete Box Girder
Girder
Bridge Superstructure
Concrete Superstructure – Concrete Superstructure –
Concrete Slab Concrete Rigid Frame

❑ Conventionally, reinforced concrete ❑ Incorporates the superstructure and

slab bridges are common for short substructure into a single integrated
spans up to 12 m in length. unit.
❑ When longer spans and deeper slab ❑ A conventional rigid frame has a
required, voids in the slabs are deck slab integrated with abutment
introduced to decrease the structure walls.
weight. ❑ This type of structure is usually for
❑ most voided slab bridges are very short spans.
posttensioned.
 Concrete Rigid Frame
Concrete Slab/Deck
Bridge Superstructure
1. Wearing Surface
❑ The wearing surface is that portion of the deck
cross section which resists traffic wear.

❑ In some instances this is a separate layer made

of bituminous material, while in some other cases
it is an integral part of concrete deck.

o The integral wearing surface is typically 1/2 to

2 in (13 to 51 mm).
o The bituminous wearing course usually varies
in thickness from 2 to 4 in (51 to 102 mm).
o Latex Modified Concrete
Bridge Superstructure
Wearing Surface – Bituminous
Material (Asphalt)
❑ An asphalt Layer which have less voids and high
surface resistance. Asphalt concrete overlay
rests on top of the deck.

❑ Asphalt concrete layer ranges from 2 to 4”. It is

recommended that to roughen its surface prior to
placement of the asphalt concrete overlay
Bridge Superstructure
Wearing Surface – Latex Modified
Concrete
❑ Latex modified concrete layer ranges [1.5 in (38 mm)].
It is recommended that to the concrete deck surface
should be blast cleaned and wetted.

❑ It is composed of cement, aggregate, and a latex

emulsion admixture (such as styrene butadiene).

❑ The properties of latex modified concrete are:

o Less porous
o Resist thermal forces caused by temperature
changes.
o Used to replace the wearing surface of existing
bridge decks.
o Less depth than asphalt concrete.
Bridge Superstructure
2. Deck
❑ The deck is the physical extension of the roadway
across the obstruction to be bridged.

❑ The main function of the deck is to distribute loads

transversely along the bridge cross section.

❑ The deck either rests on or is integrated with a frame or

other structural system designed to distribute loads
longitudinally along the length of the bridge.
Bridge Superstructure
Deck Types
❑ Bridge decks can vary according to material and
configuration. There are various types of deck
which include:

o Non-composite or composite deck

o Cast-in-place concrete slab
o Full-depth Precast concrete panels
o Corrugated Metal
o Fiber Reinforced Polymer (FRP)
Bridge Superstructure
Deck Types – Non-composite and composite deck
❑ When deck is physically connected to and working with superstructure load-bearing member in
resisting loads, it is said to be composite.

❑ If the deck is just resting on top of the superstructure and has no means of transferring longitudinal
shear from primary members to the deck, then it cannot assist in the resistance of bending moments
induced by vehicle loading is said to be non-composite.

❑ Composite deck offers more benefits and therefore composite construction is utilized whenever
possible to maximize the performance of different structural elements.
Bridge Superstructure
Deck Types – Cast-in-place concrete slab
❑ The predominant form of deck use is the cast-in-place reinforced concrete deck slab.

❑ If properly designed, the concrete slab can offer many years of service.

❑ When working in composite action, the slab essentially becomes a load resisting elements in the
superstructure components.

❑ To protect the concrete slab, a deck overlay or a protection of the deck reserved can be used to resist
the wear and tear of traffic.
Bridge Superstructure
3. Primary Members
❑ Primary members distribute loads longitudinally and are
usually designed principally to resist flexure and shear.

❑ Beam type primary members also called stringers or

girders.

o These stringers could be steel wide flange stringers,

steel plate girders, pre-stressed concrete, glued
laminated timber, or some other type of beams.

o A small fillet or haunch can be placed between the

deck slab and the top flange of the stringer to adjust
the geometry between the stringer and the finished
deck.
Bridge Superstructure
4. Secondary Members
❑ Secondary members are bracing between primary
members designed to resist cross‐sectional
deformation of the superstructure frame and help
distribute part of the vertical load between stringers.
They are also being used during the construction for
stability purposes.

❑ Secondary members, composed of crossed frames at

the top or bottom flange of a stringer, are used to resist
lateral deformation.

❑ This type of secondary member is called lateral bracing

Bridge Substructure
Bridge Substructure
1. Abutments
❑ Abutments are earth‐retaining structures which support
the superstructure and overpass roadway at the
beginning and end of a bridge. It retaining earth
underneath and adjacent to the approach roadway.
Abutments always consists of:

o Backwall sometimes called the stem, is the primary

component of the abutment acting as a retaining
structure at each approach.

o Wingwall is a side wall to the abutment backwall,

designed to assist in confining earth behind the
abutment . It can be cast monolithically with the
abutment backwall to form a single, integrated
structure.
Bridge Substructure
2. Piers
❑ Piers are structures which support the superstructure at
intermediate points between the end supports
(abutments) in long span and come in a variety of
shapes and sizes.
Bridge Substructure
3. Bearings
❑ Bearings are mechanical systems which
transmit the vertical and horizontal loads of
the superstructure to the substructure, and
accommodate/adjust movements between
the superstructure and the substructure.

❑ Bearings allowing both rotation and

longitudinal translation are called expansion
bearings, and those which allow rotation
only are called fixed bearings.

❑ The use and functionality of bearing is

greatly depending on the size and
configuration of the bridge.
Bridge Substructure
4. Pedestals
❑ Pedestals. is a short column on an abutment
or pier under a bearing which directly
supports a superstructure primary member.

❑ As shown at the left abutment cutaway, the

wide flange stringer is attached to the
bearing which in turn is attached to the
pedestal.

❑ Normally pedestals are designed with

different heights to obtain the required
bearing seat elevations.
Bridge Substructure
5. Stem

❑Stem is a primary component of the

abutment above the footing,
supporting pedestals. Its main
function is to transfer loads from
superstructure to the foundation. In
some old bridge, stem may be
omitted to save materials.
Bridge Substructure
6. Footings
❑ As bearings transfer the superstructure
loads to the substructure, so in turn do the
abutment and pier footings transfer loads
from the substructure to the subsoil or piles.

❑ A footing supported by soil without piles is

called a spread footing.

❑ A footing supported by piles is known as a

pile cap.
Bridge Substructure
7. Piles

❑When the soil under a footing

cannot provide adequate support
for the substructure (in terms of
bearing capacity, overall stability, or
settlement), support is obtained
through the use of piles, which
extend down from the footing to a
stronger soil layer or to bedrock.
Bridge Substructure
8. Sheeting

❑In cofferdams or shallow excavation,

the vertical planks which are driven
into the ground to act as temporary
retaining walls permitting excavation
are known as sheeting.

❑Steel sheet piles are one of the most

common forms of sheeting in use
and can even be used as abutments
for smaller structures.
Appurtenances and
Site‐Related Features
Appurtenances and
Site‐Related Features
1. Embankment and Slope
Protection
❑ The slope that tapers from the abutment to
the underpass called (embankment) which
is covered with a material called (slope
protection), which should be both
aesthetically pleasing‐ and provide for
proper drainage and erosion control.

❑ Slope protection could be made of

reinforced concrete slab, crushed stones, or
even block pavement materials.
Appurtenances and
Site‐Related Features
2. Underdrain

❑It is often necessary to install an

underdrain in an abutment, which is
a drainage system transports runoff
away from the structure and into
appropriate drainage channels.
Appurtenances and
Site‐Related Features
3. Approach
❑ The section of overpass roadway which
leads up to and away from the bridge
abutments is called the approach roadway.

❑ To compensate for potential settlement at

the approaches, a reinforced concrete slab
or approach slab is sometimes used for a
given distance back from the abutment.

❑ It helps to distribute the traffic loads evenly

on the soil behind the abutment to avoid
different settlements from happening.
Appurtenances and
Site‐Related Features
4. Bridge and Traffic Barriers
❑ A traffic barrier is a protective device used to
shield drivers from obstacles or slope
located along either side of roadway.

❑ Traffic barriers can vary from a guard rail

made of corrugated steel to reinforced
concrete parapets.

❑ On bridges, they are usually called bridge

railings rather than traffic barriers.
Other Related Terms
Other Related Terms
1. Vertical Clearance
❑ Is the minimum distance between the structure and the underpass. AASHTO specifies an
absolute minimum of 14 ft (4.27 m) and a design clearance of 16 ft (4.88 m).

2. Sheeted Pit
❑ A temporary box structure with only four sides that can be used as an earth support system
in excavation for substructure foundations.

❑ When this types of system used for ground level below the water, it should be watertight
and also called as cofferdam.
Other Related Terms
3. Loads

Dead Loads - Permanent loads placed on a structure before the concrete

slab hardens are
called dead loads.

Superimposed Dead Loads - Superimposed dead loads are permanent

loads placed on the structure after
the concrete has hardened (e.g., bridge railing, sidewalks, wearing surface,
etc.). They are generally considered part of total dead loads.

Live Load - Temporary loads placed on the structure, such as vehicles,

wind, pedestrians, etc., are called live loads.
Thank You