٨Research Trends and Results

Towards theEstablishment of AssetManagement Methods forRoad BridgesTAMAKOSHI Takashi, Head OKUBO Masanori, Senior Researcher
SEKIYA Mitsuaki, Senior Researche
Bridge and Structures Division, Road Department
1. Introduction During this period when road structures are steadily
aging, considering the degree of damage and thepredicted decline of investment capacity, maintenancemust become more efficient, requiring the creation ofdata based scientific maintenance to advance roadasset management. Road bridges managed by thenational government are, under the provisions ofManual for Periodic Inspections of Bridges (Draft)(March 2004), given a direct visual inspection for thefirst time within 2 years after the beginning of service
and periodically every five years afterwards. The
second inspections will soon be carried out. The
NILIM is conducting research based on detailed andmulti-faceted analysis using vast data which has been
accumulated from these inspections.

2. Optimization of the inspection system Periodic inspections are performed by directly
examining the entire bridge and all of its members
every five years. If the correlation of thecharacteristics of the occurrence and progress ofdamage and related factors can be clarified, it will bepossible to do these inspections more efficiently by
optimally combining inspection items and frequency
for the bridge and each of its members. Changes of
two inspection results performed on the same locationof the same bridge will be analyzed by damage, bymember, by type of bridge, and by bridge erection
environment in order to achieve this greater efficiency.
 Inspections are primarily visual, so the state insidemembers cannot be clarified unless symptoms appearon the surface. Specified inspections including
non-destructive inspection methods are required tocompensate for this weakness. In order to narrow thelocations and the time of the specified inspections, thecorrelation between the characteristics of steel
member fatigue cracking etc. and related factors andthe relationship between the damage and the bridge’s
performance are being researched.
 Inspections are intermittent and there are limits totheir ability to catch sudden malfunctions, so thedepartment is studying methods of detecting fatal
damage by constant monitoring of change of position
and risk management methods to introduce these intoinspection systems.
3. Establishing road bridge management methods The foundation of management is reducing the life
cycle costs (below, “LCC”) by clarifying the present
state of a bridge by the above inspections, predicting
its future condition, and repairing damage orretrofitting at appropriate times. The deterioration of abridge encompasses a wide variety of forms ofdeterioration or damage according to the condition ofeach bridge, so the results of deterioration prediction
are always scattered. This is an important point toremember when trial calculating LCC, so thedepartment is developing deterioration prediction
equations which provide LCC matched to the degreeof reliability (see Fig. 1).Degree of damage

Research Trends and Results(Key words) road bridge, periodic inspection, inspection system, asset management㪈㪅㪇㩷

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Middleof girderᩴਛ㑆ㇱy Average+ǻᐔဋ+ʍ
y Average
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Large
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Noneή

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㪇㪅㪉㩷㪇㪅㪇㩷㪇 㪌 㪈㪇 㪈㪌 㪉㪇 㪉㪌 㪊㪇 㪊㪌 㪋㪇 㪋㪌 㪌㪇Elapsed years㪇 㪌 㪈㪇 㪈㪌 㪉㪇 㪉㪌 㪊㪇 㪊㪌 㪋㪇 㪋㪌 㪌㪇 ⚻ㆊᐕ

The Markov transition probability is obtained and degree of damage
weighted based on changes of the results between two inspection (none 1.0
to large 0.0), and the mean value and standard deviation are calculated foreach number of elapsed years (tentative value by damaged member).

Figure 1. Example of Deterioration Curve of Main
Girder Corrosion on a Steel Girder Bridge
4. Future research policies The department will link a variety of research
activities with related organizations in order thatengineers skillfully employ information processing
technologies and other most advanced scientificmethods to perform inspections optimized for eachbridge, that smart maintenance systems capable of
minimizing the LCC of overall road resources andminimizing risk to road users are created, and that
required performances are established for new bridges
to control durability and reduce scattering in order toenhance maintainability.
[Reference] Web site of the Bridge and Structures
Division (with access to related reports)
 http://www.nilim.go.jp/lab/gcg/index.htm

٨Research Trends and Results