Tel/Fax  01923 682300

1. Index
2. CMCS at BRE
3. Development of AMS
4. Non-destructive testing of Marine Jetties
5. Fixed sensor monitoring of Diaphragm walls
6. Monitoring Buildings during Redevelopment
7. Tunnel Monitoring
8. Embankment Systems
9. Loggers
10. Tunnel Distortion Monitoring
11. In-place tilt monitoring system
12. Tunnels Interaction System
13. Re-Development of Small Properties
14. Viaducts
15. DLR at Mansion House
16. Tunnel Monitoring System (Discrete beams)
17. CTRL 240
18. Dams
19. Electro-levels
20. Movement indicators
21. Results of Charing Cross Load Cells
22. Non-destructive testing of concrete structures
23. Radio in Construction Monitoring
24. Settlement Reducing Piles
25. Land Surveying and Total Station Monitoring
26. Vibration Monitoring
27. Monitoring the complete strain history of concrete elements
28. Past CMCS Projects

CMCS have developed a radio system over the past five years that has been used to great effect on six major projects, three of which are illustrated in this document. A radio link between sensors and a data logger can replace vulnerable signal cabling on a construction site whilst on existing buildings it removes the need to route cables through the structure.

One of the first commercial uses of the system was on Mansfield College Oxford, where it was used to monitor crack movements inside the Grade A listed buildings as well as movements of the structure and a new diaphragm wall protecting the buildings during an excavation for a new chemistry building. The photograph opposite shows the start of the excavation close to Mansfield College clock tower. The photograph on the right shows two of the 24 crack monitors installed inside the College. The crack monitors and surveying points were fixed using 2 mm diameter stainless steel pins (a method unique to CMCS) and the radio transmitters avoided the necessity of having to drill holes through interior and exterior walls. The system operated successfully from 2000 to 2002 with a minimum of maintenance and was installed for J Laing.

The photographs (left) show the sheet piled wall that supported the excavation of a basement area at White City. Movements of the wall were monitored by CMCS for Bovis using electro-levels linked by radio transmitters to the site engineers computer to allow constant surveillance of the wall profiles.

The site engineer commented that he had been amazed by the advancement in the monitoring technology and during the 18 month installation the system had automatically warned of a large crane parked too close to the wall which caused the rate of movement to suddenly increase. CMCS software can be set to warn of overall movement or changes in the rate of movement over any given period.

The photograph opposite shows the May Gurney site at Norwich where a CMCS radio monitoring system has operated successfully for the past 18 months monitoring both the movements and bending strains in the diaphragm wall.

The site engineer uses CMCS software to process data from the system.

Other notable sites include Edinburgh where for the past 12 months the buildings surrounding a new 10,000 m2 site have being monitored by radio. At Harrow Road in London, radio systems are also being used to monitor the long-term performance of two of the repaired bents supporting the elevated section of the Harrow Road flyover. The systems include both electro-levels and vibrating wire gauges and utilise rechargeable batteries and a small solar panel to power the transmitters.

The layout below illustrates the various components in a typical CMCS system. The central unit is the logger that has 128Kb memory and is powered by a 12 volt d.c. supply. The logger is fitted with both RS 232 and 485 communication ports. The transmitters are powered by 6 volts d.c. and have a 15 bit AD converter for electro-levels and a 1/10th micro strain count for vibrating wire gauges. The operating range of the systems so far deployed by CMCS has varied from 250 m to 400 m, but the systems have been tested up to as far as 1000 m. Frequencies used by CMCS are licence exempt and the latest models are fitted with bi-directional radios and data storage capacity of up to 32 Kb.

Since the transmitters are designed to operate inside buildings, when mounted outside they need a suitable enclosure.

CE Certified two way radio system for intelligent structures

One of the most difficult engineering judgements is to estimate how close an element in a structure is to failure. The difficulty arises because the stress history of the element is not known. For concrete elements a solution may be to cast into the element strain monitors. Vibrating wire gauges are ideal for this purpose with a known track record of successfully monitoring changes in strain for decades. The problem up until now has been keeping a record of the strains monitored by the gauges. Advances in electronics and radio technology have now made the recording task much easier.

CMCS's two-way radio with storage at the transmitter has been developed for use in new structural concrete to record its stress history. One of the first applications is to record the stress changes in concrete tunnel lining segments from manufacture to inclusion as part of a tunnel lining.

The system currently consists of a six-channel VW radio (868MHz) transmitter fitted with a 32k byte of non-volatile RAM for data storage and powered by 4 x C cells. The data is recorded along with time and date, battery voltage and temperature, in total 26 bytes giving 307 days of storage before over writing. The battery life is also estimated to be approximately 1 year.

The receiver also battery powered has 128k bytes of non-volatile RAM and can be carried in the palm of the hand and is fitted with a RS232 communication port for down loading the data to a computer. The receiver if left in operational proximity to the transmitters can be set to automatically recover the data from up to 50 transmitters.

Currently the software allows for stored data recovery (automatically or on command) and the viewing real time data. If the receiver is connected to a computer then the real time data can be stored in the computer. The later operation is intended for use during loading tests of the element.

Manual operation

After pressing any key allow time for transmit - receive sequencing to link.

To recover stored data manually press the 'Log now' button after which you will be asked to input the serial number (SN) of the transmitter from which data is to be recovered. After inserting the SN the receiver will count down the scans of data as they are recovered, after which the pointers in the transmitter will be reset so that during the next recovery only new data will be transmitted. Full data store can, however, be recovered if required

To recover data real time press the 'Read input' key followed by the SN and the channel number from which data is to be recovered. Once radio link is established changing channels can be done by using the up and down arrows.

Other buttons on the receiver allow further development of the software to instigate other functions as and when defined.

Data from the system can be fully processed with CMCS Log-Safe software.