P Elliott & Co limited
P Elliott & Co limited commissioned NVM to install a monitoring system capable of measuring existing cracks and monitoring a load test on a 4 storey basement slab.
It was agreed that a manual system be put in place to monitor cracks and results sent to the client on a weekly basis. NVM installed monitoring studs on a series of cracks and monitored these with a digital callipers and a metric feeler gauge. The studs were installed over two days and a base reading then taken. All subsequent readings taken were referenced to this base reading.
In January 2010, 4 number automatic crack meters were installed on cracks currently monitored by the manual system to verify the results of the manual system. These sensors were connected to a data storage device and collected data hourly, these units also recorded temperature at each of the locations where the crack meters were installed.
A further series of load tests where carried out on using a monitoring system to record automatically any movement on the existing cracks and also to measure the displacement of the slab while the loading was taking place..
In February 2010 NVM installed a further 11 number automatic crack meters and 4 number displacement monitors at various agreed locations. These monitors were connected to two data storage devices and recorded at varying intervals depending on testing. A programme was then decided on the loading of each area, both areas would be loaded as follows:
Test one
- Load in increments of 50 mm to 250 mm and then unload in increments 50 mm until the tank was empty. The data logging equipment was set to record every 10 minutes during this test.
Test two
- Load in increments of 50 mm to 340 mm and then unload in increments 50 mm until the tank was empty. The data logging equipment was set to record every 10 minutes during this test.
Test three
- Load fully to 340 mm and leave in place for 24 hours. The data logging equipment was set to record every 30 minutes during this test.
Test four
- Cars were moved into the loading area as agreed with the consultant and the data logging equipment was set to record every 5 minutes during this test.
This is the first time a multi channel logger has been used as part of an automatic monitoring schedule and as a result the man hours on this project were greatly reduced.
For further information on any of the monitoring systems used above please
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