Structural Monitoring
Structural Subsidence
General - Subsidence
Subsidence is a specific term that relates to the motion of the ground or the earths’ surface as it moves down. However, the term is colloquially used to describe the movements of a building/structure relative to the surrounding ground and the damage that may be caused by such movements. In general parlance the term subsidence is used when the damage is by the upward or downward movement of the surrounding ground. In the UK it is highly unusual for subsidence to cause the total destruction of a building/structure except where there is extreme coastal erosion, however, that does not mean that subsidence damage cannot be considerable and deny the owner/occupier the use of a building where subsidence has occurred.
There is a very substantial list of culprits that can cause structural property damage, including:-
Inadequate design of foundations
Poor construction of foundations
Ground heave (shrinkage or swelling)
Old/New mineworkings
Changes in water table
Vegetation adjacent to foundations
Landslip
Leaks in sewers or water supply pipes
Adjacent heavy construction works
Major flooding
Subsidence is very much time related, for example, a building that has settled some 25mm over a 100 year period is not normally in any danger, however a building that suffers the same movement over a six month or one year period is a potential danger. Furthermore, differential settlement can have a more detrimental effect on a structure as walls/floors/lintels can part company with their supports.
Monitoring deformation, settlement and subsidence on larger structures such as dams, bridges etc has always been relatively cost effective due to the high cost of repairs to these structures, however, monitoring of domestic and low rise buildings until recently was, relative to the repair, expensive.
Remote Datum Ltd now has a range of low cost remote monitoring solutions to enable owners, consultants and insurers to monitor structural movement from any internet enabled PC. All our systems may be hard wired together or may be part of a wireless network transmitting back to a datalogger that onward transmits the data back a local computer or to a web address where the information can be viewed by any stakeholder (with permission) with an internetconnected computer. The data is presented as spreadsheet file or as a timeline graph. Alarms may be configured to warn stakeholders of any excess movement by means of emails and/or SMS text messages.
Crack Monitoring
Discrete low cost electronic crack sensors placed at locations where cracking is visible, or in certain cases invisible, in structural connections along with walls and floors these instruments can detect movements as small as 0.1mm. Easily installed and removed these instruments are ideal for providing a timeline history of any cracking.
Frequently installed with a temperature sensor this can determine whether the structural movement is occurring in relation to a temperature movement. Installed in conjunction with our other sensors a full picture can be built up of a structures movement. This equipment may be hard wired together on larger structures or on an estate be part of a wireless network back to a wireless hub for onward transmission to the web portal.
Deformation Monitoring
Deformation monitoring sometimes referred to a spatial monitoring is used in to determine if a structure, large or small, is deforming under load or due to age or inadequacy of it's original design. The monitoring may be by a variety of methods on large structures such as bridges and buildings a robotic total station is frequently used, this an instrument that can automatically rotate and measure in three dimensions to a fixed point many metres away. In the historic areas of Amsterdam these robotic total stations are located on street corners taking measurements 24/7 to tiny mirrors all down the street. These instruments are measuring tiny bulges and height changes in the walls of the old buildings, thereby enabling an early warning should these measurements significantly change.
However, in the main a variety of different systems are incorporated into deformation monitoring such as crack sensors, strain gauges, tilt sensors and total stations all reporting to a central server with pre-specified parameters that trigger an alarm should the data measurements exceed the specified tolerances.
Bridges and tunnels often use deformation monitoring to ensure the integrity of the structure, in the case of tunnels to ensure the tunnel is remaining circular and not being deformed by excessive ground pressure. A bridge may be checking that the bridge deck is not deforming under load.
Condition Monitoring
Monitoring all aspects of a building or structure's condition to enable analysis of possible future and early warnings of a failure, condition monitoring is particularly used in motors and machinery where vibration and sound are used to great effect to monitor the general smooth running of plant. Vibration and noise signatures are obtained by using strategically placed sensors on the target machinery, as the machine is running any deviation from the initial signature will cause an alarm and thereby enabling preventative maintanence.
Building condition monitoring is not quite so immediate as problems may take some time to show, structural failure excepted. however, two areas where monitoring a building can show immediate benefits though is power useage and infra red imagary. This can show where a company is wasting substantial amounts of expensive energy and that heat is literally going through the roof or out of the door, rapidly followed by your money.
Humidity and temperature are good indicators to the health of a building, a building that has a high average humidity can be be an unhealthy work place and may in extreme examples cause structural problems over time, due to condensation on structural members and dampness on plaster causing mould. Simarly a noisy building or noise from external sources is not a pleasant place to work and may also excarcerbate sick leave.
Typical monitoring of a building may include:-
Humidity
Temperature
Strain on structural members
Noise
Crack sensors
Tilt sensors
Thermal imaging
Vibration monitoring
Power usage
Power hot spots
Flood detection
All aspects of condition measurements can be remotely monitored, complete with early warning systems for preventative maintanence.
Tilt Monitoring
Tilt sensors small sensors are attached to the walls/floors of a building externally and/or internally and will monitor and record the rotation of the structure. Accurate to 0.66 degree they will detect if a building is tilting (rotating) and by how much.
Correctly installed and located within a structure these devices will give details of which walls/floors are rotating and if these structural segments are moving in tandem or are rotating independently of each other.
This system can be used in conjunction with our other sensors
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