Durability design for highway bridges4th_jci-aci_joint_seminar/pdf/03-Oshima.pdf · Durability...
Transcript of Durability design for highway bridges4th_jci-aci_joint_seminar/pdf/03-Oshima.pdf · Durability...
Durability design for highway bridges
YOSHINOBU OSHIMACenter for Advance Engineering
Structural Assessment and Research (CAESAR)
Public Works Research Institute (PWRI)
Durability design for highway bridges
Introduction• Japanese Specifications for Highway
Bridges (SHB) was revised in July 2017– The legally-binding design codes for
national highways and expressways and the de-facto standards for other roads.
Provisions (legally-binding)Commentary
Actions/loads Accumulation of persistent actions/effects
Durability requirements
Material deterioration or distress to structural elements will not violate the strength design assumptions to the end of the given design life
Verification index Period on the time axis
3
Design service period
Strength limit
Initial
Strength
Revised SBHPeriod to maintain Strength
Alternative
Strength limitStrength with deterioration
TimeEnd of service life
Strength limit
Initial
Strength
TimeEnd of service life
Durability design for highway bridges
How to ensure the reliability of durability?Action Resistance
Index
Variation of resistance
Strength?
Variation of action
Assumption is reliable?
Durability design for highway bridges
Prerequisites• Ex. Chloride attack
Diffusion phenomenon
Flying salinity
Deicing agent
Splash condition
Leakage
Durability design for highway bridges
Environmental loading
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distance from coastline(km)
amou
nt o
f sup
plie
d N
aCl(m
g/dm
2 /day
)
amou
nt o
f sup
plie
d N
aCl(m
g/dm
2 /day
)am
ount
of s
uppl
ied
NaC
l(mg/
dm2 /d
ay)
distance from coastline(km)
Okinawa Islands
area b.
b.
c.
a.
distance from coastline(km)
area c.
area a.average97% confidence limit
266 locations over 3 years
Durability design for highway bridges
Uncertainty of durability Various environment in a bridge Several factors may affect one phenomenon Large divergence between the assumption and reality
Durability design for highway bridges
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The gap between the prerequisites and actual exposure condition
Breakage of PC lateral tendons
Leakage from the upper flange of T-girder
The water splashes from the breakage of PVC drain pipe
Leakage from precast joints
Durability design for highway bridges
Several approaches of chloride
Joint or cracks of pavement
Leakage from end edgeChloride
Wetted by strong wind or leakage from a drain pipe
Remaining water Leakage from the inside drain pipe
Deicing agent (CaCl2)
Durability design for highway bridges
Inspection in 1979The 3rd block anchorage
Inspection in 19838th block lateral beam
1) Infiltration from the girder end
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A case in a segmented box PC girder
Bridge deck water
Stored water
Water ingress from the anchorage into the ductThe anchorage Lat. Beam
Durability design for highway bridges
Damage in the drain pipe
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2) Infiltration from the broken drain pipe
Leakage water ingress from the broken pipe
Water ingress from the anchorage into the duct
A case in a segmented box PC girder
Durability design for highway bridges
Clogging of drain hole on the pavement
Leakage stain on the upper flange 12
A case in a segmented box PC girder3) Infiltration from the box joint
Walkway boundary
Construction joint of pavement
Stored water due to drain clogging
Upper anchorage
CablesWater
Durability design for highway bridges
Corrosion and Breakage of PC Cables due to Insufficient Grouting
PC Cables are corroded and broken in the Bottom Flange of a Box Segmented PC Bridge
Broken PC Cables
Myoko Bridge(Nigata Prefecture, Japan)Built in 1972
Direction of seasonal strong wind
Water from the drain pipe issplashed by strong wind
Durability design for highway bridges
Durability design•Variation and uncertainty of durability can be reduced by fitting the actual situation to the prerequisites.
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Design consideration
Action Resistance
Index
Variation of resistance
Variation of action
(Tips from best practice)
Durability design for highway bridges
Concept of durability
• Durability is the capability to have a time reliability to sustain the strength assumption for designated period
• “Durability” indicates not only material durability but also the feasibility of inspection and repair (maintenance), at any moment over the service life
Time
Stre
ngth
End of service life
??
Inspection
Repair
Strength criterion
Durability design for highway bridges
Maintainability and inspectability• Develop the guidelines consisting of best
practices of maintainability and inspectability
Existing edge detailof concrete girder Model specimen Examining
inspectability
The monitoring regarding deflections (geodetic measurement) and opening changes in some joints between concrete panels had been executed for 24 hours from 2013.
Inspection is overwhelming?The footbridge collapse in Prague, the Czech Republic (2017 Dec.)
Durability design for highway bridges
• Sudden collapse can be avoided not only by inspection but also the other alternativessuch as structural redundancy:– Enhancement of inspectability?– High durable material?
19http://35wbridge.pbworks.com/w/page/900718/Mianus%20River%20Bridge%20Collapse
Inspection vs. Redundancy
Durability design for highway bridges
Design consideration in SHBConsider the followings as necessary1. Quality control in construction 2. Redundancy3. Maintainability and inspectability4. Certainty of design assumption
It is difficult to standardize the method to attain the above points for all kinds of bridges
These points should be considered at any phase of design
Durability design for highway bridges
Verification for 100 years
IRABU bridgeSESOKO bridge
Verification of the 100-year-durability of bridges on remote islands in Okinawa
• Chloride penetration in an actual bridge
How worse should we assume?Does Chloride penetrate as we thought?
Durability design for highway bridges
IRABU bridge
IRABU island
Miyakoisland
Durability design for highway bridges
Durability design for highway bridges
Additional cover concrete
+3.3m
+5.6m
Effective area for load bearing capacity
Additional cover concrete for bore holing (+120mm)
Durability design for highway bridges
Durability design for highway bridges
Durability design for highway bridges
SummaryIn Japanese design specifications for Highway bridges, • Durability should be associated with
proper maintenance– Strategy to ensure the strength performance for
design period should be clarified
• Further research should be done for reducing the variation of durability– Learning from best practice, enhance the reliability
of design assumption
Thank you very much for your attention
Okinawa Irabu Bridge