Monitoring of buildings: what are the risks of a “box-ticking” approach?

Edgars Pinkovskis, head of the geodetic company Geomatic, has observed that monitoring of buildings is a part of the construction process that is often treated as a pro forma task in Latvia, as merely a matter of fulfilling the requirements specified in the work organisation project (WOP). This often leads to situations where a construction project needs to be halted completely, and compensation needs to be given for damage caused to surrounding buildings.  Project developers, for their part, are often forced to deal with fairly large compensation claims, when it is discovered that (for example) the walls of buildings have cracked, or the roof has started to leak, or any number of other building problems have emerged.

Edgars Pinkovskis explains when and why monitoring of buildings is necessary: “Construction of a site tends to result in deformations in the buildings adjacent to the construction work, so monitoring of buildings is a very important aspect of the construction process. This is specialised geodetic work to be carried out if, according to legislative requirements, monitoring of buildings is included in the WOP, with indication of the buildings to be monitored, the methods to be used, and the required frequency of measurement (weekly, monthly, etc.). Unexpected and unpleasant situations tend to arise, for a variety of reasons. Edgars Pinkovskis describes one such case: A site was being built on Cesu Street in Riga with a WOP requirement to monitor the buildings twice a week. No deformations were observed during the specified monitoring of the buildings. However, there was an element present that could not have been foreseen: the piling works being carried out at the site between the monitoring measurements.  Some buildings were located near the construction site, and over time, several buildings developed significant cracks that had not been there before. Such consequences could have been prevented by continuous monitoring of activity at the site via sensors, Edgars Pinkovskis says. The specialist explains that, in contrast to traditional monitoring, the buildings under monitoring in this case are fitted with sensors that, in normal working mode, take measurements every hour, recording the smallest deformations that cannot be spotted visually. The resulting data is sent to the base station and then to the server, where it is processed via special software. The system will report whether the deformation has reached a certain degree (when the yellow or red line has been crossed), and immediately alerts the responsible person(s) via e-mail and SMS. This monitoring system can be configured to capture data within seconds, and is available to designated personnel in online mode.

Edgars Pinkovskis emphasises a significant advantage: “Continuous monitoring of activity using sensors makes it possible to spend resources intended for formal monitoring more efficiently and avoid potential problems.”

What deformations can be detected using sensors?

Sensors can measure and detect various different types of deformations. Inclination sensors are used to measure the tilting of a structure. They can be installed on a vertical structure, such as a wall, where they then measure the inclination from the vertical line; these sensors can also be installed on horizontal floors and measure their tilt. Crack measurement sensors, on the other hand, are installed at a structure’s most significant cracks, and measure the extent to which the cracks increase as a result of construction work. Geophones or vibration sensors measure vibrations from a construction site. Particularly strong vibrations can occur during the course of pile drilling and embedding work; both vertical deformations and cracks can occur in the course of using a vibratory compactor.

Sensors designed to measure structural deformations (stress) can determine whether structural deformation occurs under a load. Such sensors are very often installed on metal structures. Edgars Pinkovskis reveals that a property is currently being built in Latvia wherein three types of sensors are used for building monitoring: inclination measurement, crack measurement, and geophones or vibration sensors. This site’s WOP required the monitoring of buildings with automatic systems, and sensor monitoring was chosen as the most appropriate solution.

Continuous monitoring of activity using sensors is particularly useful for builders working on a site who are required by the WOP to monitor buildings. This type of monitoring is a practical and reliable solution for construction experts carrying out construction supervision of sites where monitoring of buildings is required. At the same time, it would be advisable to install inclination sensors, stress measurement sensors, and crack sensors at logistics centres, in large warehouses, and in buildings that many people pass through every day, because the sensors would monitor the bolted structures and enable elimination of the potential risk to human safety. At construction sites where monitoring of buildings is necessary for more than two years, purchasing of sensors is the more advantageous option.  On the other hand, at sites where monitoring of buildings is necessary for a shorter period of time, it is more advantageous to lease them.

The purchase or lease of sensors includes service consisting of the installation of sensors, the preparation of the data obtained for subsequent analysis by the relevant construction experts and, where necessary, training and provision of advice.