r - The Hong Kong Polytechnic University

4. OPERATION STRATEGY OF SHMS
The operation of SHMS is in three stages, routine monitoring stage, sub-critical monitoring stage and critical
monitoring stage. The routine monitoring stage refers to the condition that if the measured data which is less
than or equal to 75% of Q SLS , then no additional monitoring work is required and routine monitoring continues,
where Q SLS is the designated performance criteria at the serviceability limit state. The sub-critical monitoring
stage refers to the condition that if the measured data which is following within 76% to 100% of Q SLS , then
components or locations associated with this measurement value will be concentrated for monitoring. The
critical monitoring stage refers to the condition that if the measured data is exceeding 100% of Q SLS , then
structural evaluation works (to be carried out by the SHES) on the relevant components/locations or whole
structural system will be carried out. The 75% of Q SLS is used as the limit or alarm limit for no additional
monitoring works because the measured data implies that there still has a safe factor of 1.3333 (=1/75%) or a
reserved capacity of 25% in the instrumented location or structural component.
In the routine monitoring, a quarterly monitoring report is produced. The customized software tools as
mentioned in Paragraphs 3.3.1 – 3.3.3 are used to generate this quarterly report semi-automatically and it, under
the normal condition, includes the monitoring results of all measurands except seismic, ship impacting and
global static features – because they are either under extreme condition or special arrangement.
5. FUNCTIONS AND COMPONENTS OF SHDMS
5.1 System Overview
The SHDMS is composed of hardware and software systems. The hardware system refers to the SHDMS-Server,
which is located in the Bridge Health Monitoring Room at the West Control (Administration) Building. This
server is a 64-bit Itanium server and is equipped with 4 dual-core processors, 64 GB RAM of main memory, a
120-day or 3000 GB rolling-buffer storage system for raw data, 2000 GB permanent storage system for
processed and analyzed data and two 600 GB DLT tape drivers as permanent storage system for raw data. The
software system refers to the Data Warehouse Management System (IBM DB2 Data Warehouse Enterprise
Edition under UNIX operation platform). This software is equipped with relational database management
system and on-line analytical processing (OLAP) tools for integrating enterprise-wide corporate data into a
single repository from which users can run queries, perform analysis and produce reports. The data flow
diagram for SHDMS is given in Figure 48.
5.2 Basic Data Operation Requirements in SHDMS
The data operation in SHDMS is devised to fulfill the four basic types of data operation requirements, i.e., (i)
subject-oriented data operation, (ii) integrated data operation, (iii) time-variant data operation and (iv)
non-volatile data operation. The first requirement means that the data warehouse is organized around the major
subjects of bridge monitoring works or the fifteen types of measurands as stated in Paragraph 3.3.2 above. The
second requirement means that the data from different sensory systems and application software systems at
different hardware platforms are having different data formats, and these inconsistent data are integrated to a
unified format for viewing, storage, processing and analysis. The third requirement means that the data in the
data warehouse is accurate and valid at some point in time or over some time interval, and the time-variance of
the data warehouse is also shown in the extended time that represents a series of snapshots. The last requirement
means that as the data is not updated in real-time but is refreshed from operational systems on a regular basis,
hence new data is always added as a supplement to the data warehouse rather than a replacement – the data
warehouse is therefore required to continually absorb the new data and incrementally integrate it with the
previous data.
5.3 Functions of the Customized Software Tools in SHDMS
The customized software tools in SHDMS are required to carry out four major functions of (i) data
administration and management, (ii) operational data storage, (iii) data manipulation, and (iv) multi-dimensional
view of data. The first function ensures the data warehouse having the capability of executing the tasks of (a)
monitoring data loading from multiple sources, (b) data quality and integrity checks, (c) managing and updating
metadata, (d) monitoring databases performance to ensure efficiency query response times and resource
utilization, (e) auditing data warehouse usage to provide user chargeback information, (f) replicating, sub-setting
and distributing data, (f) maintaining efficient data storage management, (g) purging data, (h) archiving and
backing-up data, (i) implementing recovery following failure, and (j) security management. The second function
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