Research Trends and Results

Development of under-floor deterioration diagnosis
equipment for preventive maintenance engineering ofwooden building
TSUCHIMOTO Takahiro, Head (DAg), WAKIYAMA Yoshio Senior Researcher (DE)
Evaluation System Division, Research Center for Land and Construction Management(Keywords) palpation examination, moisture content measurement, dark place imaging, sampling, biodeterioration,
boring resistance
1. Background of the study

Nowadays, conversion is progressing from newsocial investment to ‘stock-type society’ whichkeeps past social capital long and takes care of it.
Previously, damages, etc. were dealt withrespectively and ex post facto. However,considering that damage risks due to aging willrapidly increase in the future, a strategic
maintenance is required. This is based on the idea of‘preventive maintenance’ which regularly inspects
and diagnoses structure conditions, and takes
measures prior to development of critical risks withthe aim of reducing life cycle cost. Technologicaldevelopment in the inspection field is crucial for
efficient preventive maintenance engineering.
Particularly, development of the technology isrequired in order to efficiently inspect many target
structures and to inspect locations difficult for visualconfirmation.
Therefore, a comprehensive technologicaldevelopment project of Ministry of Land,
Infrastructure, Transport and Tourism named‘Development of inspection and observation
technology for preventive maintenance engineeringof social capital’ was implemented. In the woodenbuilding field under the project, narrow and dark
underfloor was focused on and the equipment for
efficient under-floor diagnosis was developed.
2. Sorting out requirements, design and trial
manufactureof
deterioration
diagnosis
equipment
Requirements to be met by the deterioration diagnosis
equipment, its design principle and contents of trial
manufacture and improvements were decided after muchdiscussion in ‘Development Committee on deterioration
diagnosis equipment for preventive maintenanceengineering of wooden building’ held by NILIM(Chairman: Professor of Kanto Gakuin University,
Masao NAKAJIMA).
The results of sorted out
requirements to be met by the equipment are as follows.
* As a result of survey of effective underfloor height ofpublic housing and former Housing Loan Corporation
housing (total about 64,000 buildings), the maximum
dimension must be 30cm or less.
*As it is difficult to give a diagnosis for preventive
maintenance engineering by imaging only, it isindispensable to conduct palpation examination andmoisture content measurement.

*A small Phillips screw driver is comparatively suitable
for the shape of tip section of palpation examination
feature.
Based on the above, the underfloor deterioration
diagnosis equipment was manufactured experimentallyand its functionality was verified empirically.
3. Improvements of deterioration diagnosis
equipment
As a result of the above verification test of function,
the following improvements were required in view ofnecessity to increase diagnosis efficiency.
*To enable to continuously conduct palpation
examination in running and orthogonal direction inorder to make it easy to continuously conduct palpation
examination of underfloor horizontal bracing.
*To introduce boring resistance measurement of screws,etc. which are easy to judge the presence or absence of
biological deterioration in palpation examination.
*To add a mechanism for sampling of the surface ofdeteriorated wood and hyphae, etc.
In case all of the above improvements are included, thechassis will be too large. Accordingly, two types ofimproved version of diagnosis equipment (picture) weremanufactured as final products, one of which is to rotate
palpation and moisture content measurement mechanism
by 90°by remote control and another is to rotate by
90°manually, thereby making the chassis dimensions
smaller.
This will lead to improvements in efficiency of
preventive maintenance engineering for narrow
underfloor to where no one can enter and of deterioration
diagnosis aiming at performance evaluation of existinghouses.

Picture:Under-floor
deterioration
diagnosis
equipment for preventive maintenanceengineering of wooden building (withfunction of rotation by remote control)