Keywords: data, acquisition, control systems, structural monitoring, real time.

This paper describes the new and novel aspects of an advanced monitoring system known as the Cardington Test System (CTS) developed for a unique structural test undertaken by the BRE. The test involved dismantling a section of a corner column at the bottom of a full scale seven storey structure, then lowering and raising the corner of the building to generate damage and simulate settlement and heave.

To set the context for the monitoring system the paper briefly describes the building being tested, the reasons for the testing, the test apparatus and the testing itself. The paper outlines why an advanced monitoring and control system was desirable.

Earlier work in this area by the authors had developed a list of six aims for advanced monitoring systems these included; Improved presentation of the available information and Situation and model matching. The paper will briefly explain these aims and how they relate to the CTS. In general the objectives of the CTS was to further the advancement these aims and fulfil some specific requirements of the engineers undertaking the test.

A novel aspect of the CTS was the requirement to interact with an existing monitoring installation. The CTS has to collect the required data via the monitoring installation, but not adversely effect it's operation. The paper presents details of the monitoring installation with schematics and photographs. The CTS interacts with the loggers of the monitoring installation via a star network of RS232 cables. Such an arrangement allows rapid collection of data and reliability of operation (a logger connection can be lost without affecting the others). The CTS sends text commands and receives text responses that are processed to establish the sensor and sensor value.

The CTS was developed using a real time expert system environment (shell) from Gensym called G2 on a medium specification Windows NT workstation. G2 is a real time object orientated knowledge based system shell. G2 was chosen more for its excellent ability to handle real time data and supportive development environment, than for its in-depth expert system components. The expert system, or more specifically the rule-based components, was used to undertake much of the processing (using the English like rules). However the rule base is simple (no extensive forward or backward chaining) and hence the CTS can only be considered a very restricted expert system. The paper does not address the expert system nature of the CTS in depth, the expert system techniques can simply be considered as good tools that support the rapid system development.

The paper describes the development of the components of the CTS in some depth. For example, it will show how English like rules can be used to process the data and how such a rule formats support verification of the system. The system was developed using the rapid prototyping methodology. The paper illustrates a selection of the facilities within the CTS available to the engineers during the test. These include:

• How the CTS supports navigation to specific sensors. This includes standard formats for objects (such as slabs), clear icons for sensors and colour to aid rapid recognition and interpretation of say the location, type and position of a sensor.
• The presentation of data in ways most useful to the engineer. These include, real time graphs for an individual sensor which could be presented on demand and compared with other sensors, plots of one sensor outputs against en other and summary tables of sensor values
• Prediction of values. Prediction was used to estimate longer-term items such as the final deflection (when the corner of the building was being lowered) and shorter-term predictions such as how long it will be until the current change in hydraulic jack load increment achieves the desired value.

The paper shows how:

• Experts systems can be used not so much for detailed knowledge handling, but as a good tool to support the rapid development of monitoring and control systems.

• Advanced control systems can be integrated with an existing monitoring system.

• Engineers undertaking safety critical testing can be well supported by the use of advanced monitoring and information handling systems.

• A monitoring system was developed to address the aims of improving presentation, performing sensor validation, applying engineering rules of thumb, undertaking prediction and providing supporting the operator.

1

Chana P. S., Moss R., "The European Concrete Building Project at Cardington", Paper to be published in Structural Concrete: the Journal of the fib

2

Goodier A., Matthews S.L., "A Role for Real-time Structural Monitoring Expert Systems", Proceeding of the International Conference on Information Technology in Civil and Structural Engineering Design", Glasgow, August 1996.

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