Introduction to Bridges
6.
BRIDGE MAINTENANCE AND REPAIR
Objectives
 understand the need for routine and preventative maintenance
 know some methods and materials that are used
Introduction
Maintenance of bridges is required to provide a reasonable level of safety and
service to the traveling public. It is also desirable to maximize the economic
return on the investment in the bridge system. Preventative maintenance and
regular routine maintenance are cost effective ways to achieve both of these
objectives. This lecture will discuss the typical kinds of damage and
deterioration that various bridge components experience and some of the
maintenance methods applied to mitigate or fix them.
Overhead #2 - Preventative Maintenance Objectives
 primary purpose is to protect investment in infrastructure by
maximizing life and also keep system safe for the road user
Overhead #3 - Preventative Maintenance is Cost Effective
 proven fact
 small expenditure on changing oil in your car results in long term
saving
Overhead #4 - General Maintenance Methods - Concrete
 repair damage and protect from intrusion of moisture and harmful
chemical by sealing
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Overhead Notes
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Introduction to Bridges
 concrete is a porous (permeable) material
Overhead #5 - General Methods - Steel
 steel will corrode or return to natural state (rust) so must be
protected against exposure to elements
 cathodic protection prevents electrical potential required for
corrosion
Overhead #6 - General Methods - Timber
 timber needs protection from fungus attack
- kept dry or treated with chemicals
Overhead #7 - Bridge Seats and Caps
 run off from deck contains salt which damages concrete and
promotes corrosion of bearing and concrete reinforcing
Overhead #8 - Bridge Seats and Caps
 maintenance in form of washing to remove salt or control flow of
water through the joints as well as protective coatings is necessary
Overhead #9 & 10 - Substructure - Concerns
 substructures are damaged by material deterioration mechanisms
such as freeze-thaw, corrosion, spalling, decay, etc. or by mechanical
impact, abrasion, etc.
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Overhead Notes
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 differential settlements and unexpected soil pressures (slides, uneven
side loads) can also be very destructive
Overhead #11 & 12 - Substructure Maintenance
 material deterioration prevented by sealers and coatings
 foundation problems can be mitigated with regrading subsurface
drains, struts, etc.
Overhead #13 - Superstructure - Concerns
 deterioration and damage most often due to chemical attack from
salt, CO2 (carbonation) which some times are caused by poor design
and construction
 impact from high load damage and occasionally ice and drift
associates with flood
 fatigue most common on superstructures
Overhead #14 - Superstructure Maintenance
 protection systems in the form of coatings and sealers most common
 pressure washing and cleaning
 improve drains or drainage
Overhead #15 - Deck
 due to exposure conditions, directly in contact with traffic, decks are
most susceptible to deterioration
 exposed to salts, acid rain, UV, mechanical impact, etc.
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Overhead Notes
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 protects the rest of structure from exposure
Overhead #16 - Concrete Decks
 concrete is most common deck material
 reinforced concrete and salt are a bad mix
- causes corrosion, spalls, etc.
Overhead #17 - Concrete Decks
 effects can be mitigated by good design and construction practices
such as concrete cover, good drainage, thicker slabs to reduce
exposure and methods such as silica fume, low w/c ratio, proper
curing, etc. to reduce concrete permeability
Overhead #18 - Concrete Decks
 preventative maintenance intended primarily to reduce moisture and
chemical content of deck concrete by washing, filling cracks, sealing,
and applying overlays
 installing deck drains in low spots
Overhead #19 - Curbs & Railings
 material deterioration will occur over time
 experience exposure similar to decks
 collision damage also is a major factor
Belke Consulting Ltd.
Overhead Notes
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 galvanizing is appropriate since paint quickly chipped and abraided
by sand-salt from deck
Overhead #20 & 21 - Deck Drains
 very important element which is often overlooked
 when not properly maintained can increase rate of deck deterioration
and also traffic hazard
 should be retrofitted wherever water is seen to pond after rain or
spring thaw
Overhead #22 - Approach Road
 approach bumps are common due to headslope settlement
 bump causes road user discomfort but also can seriously affect life of
bridge by dramatically increasing impact loads applied to the bridge
 guard rail should be continuous from approach to bridge (connected)
the transition from flexible to rigid as provided for in standard
drawings is important
 some older style rails require modification to attach guard rail
 drainage off the side of approach and not onto deck should be
maintained
Overhead #23 - Approach Road
 erosion at toe of slope and ditches can cause instability and slides
 signing vertical clearance, load limit and delineators protect bridge
as well as the road user
Belke Consulting Ltd.
Overhead Notes
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Overhead #24 - Streams and Channels
 channel damage usually associated with floods or high water
 slope protection, bank protection, rip-rap, etc. are required to
maintain integrity of bridge as well as approach roadway
Overhead #25 - Bridge Major Maintenance and Rehabilitation
 in addition to preventative and routine maintenance more extensive
work is required from time to time. These actions are undertaken
when, despite other efforts, deterioration becomes serious but before
costs become too high or before replacement is required
 important to do at optimum time
- premature work wastes money but when too late cost
becomes too high
Overhead #26 - Culvert Major Maintenance and Rehabilitation
 measures to maintain integrity of structure
 usually affect hydraulic capacity
Overhead #27 & 28 - Repair Materials
 concrete with additives to improve mechanical properties
 in addition to regular materials many specialty products have been
developed with unique properties for special uses
 some are very good, others not
Overhead #29 - Approved Products
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Overhead Notes
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 due to the number and diversity of products on the market
procedures for evaluation have been developed
 procedures lay down standard test methods carried out by certified
labs at manufacturers’ expense
Overhead #30 - Concrete Sealers
 sealers are categorized by end use, penetrating for decks which wear,
coatings for non-wearing surfaces and pigmented coatings for
aesthetics
 further by relative moisture content of concrete to be treated
Overhead #31 - Concrete Patching Materials
 patching materials categorized by use or application
 horizontal surfaces (poured)
 vertical or overhead
 temperature range
 high early strength
Overhead #32 - Paints
 many paints on market but only a few suitable for bridges
 some paints are difficult to handle & apply
 most durable paints used for severe exposure
 new paints are non toxic and low VOC
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Overhead Notes
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 old toxic paints must be recovered and treated as hazardous waste
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Overhead Notes
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