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)


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


How to ensure the reliability of durability?Action Resistance

Index

Variation of resistance

Strength?

Variation of action

Assumption is reliable?


Prerequisites• Ex. Chloride attack

Diffusion phenomenon

Flying salinity

Deicing agent

Splash condition

Leakage


Environmental loading

6

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)


Okinawa Islands

area b.

b.

c.

a.


area c.

area a.average97% confidence limit

266 locations over 3 years


Uncertainty of durability Various environment in a bridge Several factors may affect one phenomenon Large divergence between the assumption and reality


8

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


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)


Inspection in 1979The 3rd block anchorage

Inspection in 19838th block lateral beam

1) Infiltration from the girder end

10

A case in a segmented box PC girder

Bridge deck water

Stored water

Water ingress from the anchorage into the ductThe anchorage Lat. Beam


Damage in the drain pipe

11

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


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


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•Variation and uncertainty of durability can be reduced by fitting the actual situation to the prerequisites.

15

Design consideration

Action Resistance

Index

Variation of resistance

Variation of action

(Tips from best practice)


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


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.)


• 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


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


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?


IRABU bridge

IRABU island

Miyakoisland


Additional cover concrete

+3.3m

+5.6m

Effective area for load bearing capacity

Additional cover concrete for bore holing (+120mm)


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

durability design for highway bridges4th_jci-aci_joint_seminar/pdf/03-oshima.pdf · durability...

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