Frequently asked questions on structural monitoring

Structural monitoring is the instrumental observation of how a building or piece of infrastructure behaves, through sensors installed on the structure. The sensors measure quantities such as accelerations, displacements and inclinations, and return objective data on how the structure behaves over time and during significant events.

Unlike a visual inspection, which captures the apparent condition at a given moment, monitoring measures real behaviour continuously.

It serves to base decisions about a structure on measurements. Over time it makes it possible to follow how behaviour evolves and to identify early signs of degradation, directing maintenance where it is needed. After an earthquake or another extraordinary event it provides the data to establish quickly what happened to the structure.

A structural assessment is a technical evaluation carried out by a qualified professional on the basis of surveys, calculations and analysis. Structural monitoring provides the measurements on which that evaluation rests.

The two are complementary: monitoring makes the assessment better documented and repeatable, while the assessment interprets the data in the light of the characteristics of the structure.

Monitoring is useful at two distinct moments. Under ordinary conditions it observes how the structure evolves and catches degradation while correcting it is still inexpensive. After an event it records the response of the structure and provides the data for immediate decisions.

BBOX 2.0 includes both modes in its base configuration.

Industrial and logistics buildings, residential complexes, corporate headquarters and retail properties, hospitals and emergency facilities, bridges and viaducts, historic and protected heritage buildings.

Monitoring is particularly relevant where downtime carries a high cost, where the structure hosts many people, where surveillance obligations exist, or where the value of the asset has to be documented.

BBOX 2.0 is the continuous structural monitoring system developed and manufactured by MOSI. It consists of accelerometer sensors, a datalogger and a web platform, and brings together in a single architecture the monitoring of structural health under ordinary conditions and the recording of the response during events.

BBOX 2.0 is the second generation of the BBOX system. Same company and same product line, with significantly different capabilities. The first generation recorded the structural response during a seismic event and made the measured data available for the assessments that followed.

BBOX 2.0 keeps that function as one of its two modes and adds a second one, continuous monitoring of structural health through the ordinary years. The architecture changes, with next-generation MEMS sensors, a datalogger that accepts several sensor types and data transmission over wired or mobile networks. And what the client receives changes too: a report interpreted and signed by a structural engineer.

"Black box" is the analogy used to describe the system for years, and it captures one of its two modes well: during a seismic event BBOX 2.0 records accelerations, displacements and interstorey drift, and that data becomes the objective basis for the post-event assessment.

The description covers what happens during the event, so part of the current system. The other mode works in the absence of events: it follows the structure's dynamic characteristics through the ordinary years to catch degradation while correcting it is still cheap.

No. The system grew out of MOSI's experience in seismic monitoring and covers both modes in its base configuration, with no additional components: Structural Health Monitoring (SHM), which follows structural condition under ordinary conditions, and the recording of the response during significant dynamic events.

Yes. The system is specified in projects and tender documents for the structural monitoring of buildings, bridges and infrastructure, in both public and private contexts.

Structural Health Monitoring is the continuous monitoring of the condition of a structure under ordinary operating conditions. It is based on observing dynamic parameters, that is, the way the structure vibrates, and on comparing those parameters over time.

A stable change in the dynamic characteristics indicates a change in the structure, and makes it possible to catch degradation before it becomes visible.

Operational modal analysis extracts the dynamic parameters of a structure from ambient vibration, without applying artificial excitation. The accelerometer signals are processed to obtain three quantities.

The natural frequencies, that is, the frequencies at which the structure tends to resonate, related to stiffness and mass distribution. The mode shapes, which describe how the structure deforms at each frequency. The damping, that is, its capacity to dissipate vibrational energy.

A change in these parameters over time indicates a structural change.

Continuous structural monitoring is the general term: it refers to the instrumental observation of a structure over time. Structural Health Monitoring is one of its modes, the one that observes behaviour under ordinary conditions in order to follow how it evolves.

The other mode is event monitoring, which records the response during extraordinary loading. Both fall within continuous structural monitoring.

No. It means that the structure is observed in a stable and systematic way over time, at the interval defined in the monitoring design. Acquisitions can be scheduled at regular intervals or triggered when a threshold is exceeded.

In BBOX 2.0 the recording interval is programmable remotely and can be changed while the system is in service.

Temperature and humidity affect the dynamic parameters of a structure, and on historic masonry the effect is significant. A seasonal variation that is not compensated for risks being read as degradation.

BBOX 2.0 acquires thermal data in parallel and uses it to compensate for the effect of temperature, so as to separate reversible variations from structurally significant ones.

Yes, and it is one of its main effects. Catching a change early turns an emergency job into scheduled work, at lower cost and without unplanned downtime.

Monitoring enables early detection. A quantified estimate of the remaining service life of a structure is a frontier that no system delivers today.

Because degradation accumulates invisibly. Material fatigue, corrosion, foundation settlement and thermal cycling act for years before becoming visible, and a periodic inspection captures a single moment without revealing the trend.

Much of the Italian and European building stock was built before the 1990s, often in reinforced concrete and to superseded seismic codes. Continuous monitoring follows the evolution of the dynamic parameters and turns uncertainty about the structure's condition into a series of comparable measurements over time.

Quantified prognosis of remaining service life is an open research frontier, and no monitoring system delivers it today as a reliable result.

What continuous monitoring does allow is catching changes in structural behaviour while they are still small, so that interventions can be planned rather than endured. Maintenance becomes a decision taken on measurements, with the timing chosen by the owner.

It is the measurement of how a building or an infrastructure responds during an earthquake. The system records accelerations at the foundation and at floor level, and from these derives displacements and interstorey drift, the code-referenced damage indicator: comparing it with the design limits gives a quantitative picture of the condition of the structure. Recording starts automatically when a threshold is exceeded and includes the seconds preceding the peak.

No. No system installed on a building predicts earthquakes. The purpose of seismic monitoring is to measure the response of the structure during the event and to make that data available afterwards, when decisions have to be taken quickly.

It is the acquisition mode that starts recording when a set threshold is exceeded. The primary reference is the earthquake, but the same approach applies to impacts, extreme wind, floods and any extraordinary dynamic action.

In BBOX 2.0 the threshold is independent for each sensor and programmable remotely. Acquisition is continuous, so the seconds preceding the peak are always included, and it continues after the event to capture the residual free oscillations. The system stays active even during a blackout.

The system records in four phases. The seconds before the threshold is exceeded are already included in the recording, thanks to continuous pre-trigger acquisition. When the threshold is exceeded, recording of the event begins. Recording continues after the event to capture the free oscillations. The uninterruptible power supply keeps the system running even if power fails during the tremor.

Because decisions are taken within hours and concern people and operations: whether it is safe to go back in, whether production can restart, which parts should be inspected first.

Without measured data, caution prevails and the structure stays out of use longer than necessary. With data, the decision rests on measurements of the real response, available before the inspection takes place.

Yes. Seismic design aims to protect people and to keep damage within acceptable limits, which leaves open the possibility of damage to structural, non-structural and building service elements.

This is one of the reasons why measuring the real response remains useful even on recent buildings designed to seismic criteria.

Seismic isolation is a system designed to work during an earthquake, and its performance shows up at that moment. Monitoring provides an objective measurement of how the system responded: how much motion arrived from the ground, how much of it was held back by the isolation plane and how much entered the superstructure. On an uninstrumented building, after an event those quantities remain analytical estimates. On an instrumented building they are recorded.

By comparing the accelerations measured on the two sides of the isolation plane. The ratio between the signal recorded above the device and the one recorded immediately below expresses how much the system actually dissipated during the event. It is a direct measurement of the device performance under the conditions it was designed for, obtained from real event data instead of from a calculation model.

Because the effectiveness of isolation is by definition a difference between two levels. A sensor placed on one side only records an acceleration, and from that isolated quantity you cannot derive how much the device contributed. The pair of measurements across the isolation plane is the configuration that makes performance quantifiable, and it is the reason why installations on isolated structures include sensors on both sides.

Accelerations are measured on both sides of the isolation plane, at the instrumented bearings. The comparison between the two measurements describes how much motion the device held back during the event. At the new INRCA hospital in Camerano thirty-two accelerometric sensors are installed, arranged so that the comparison across the device is available at each of the monitored bearings. The measured quantities are accelerations, and from these the response parameters of the structure to the event are derived.

The number depends on the geometry of the structure and on the number of bearings to be monitored. At the new INRCA hospital in Camerano thirty-two accelerometric sensors are installed. The criterion that matters is coverage: enough points in plan are needed for the acceleration ratios to be comparable between different zones of the building, together with the measurement on both sides of the isolation plane at each instrumented bearing.

The comparison between ratios computed at different bearings indicates whether the isolation system worked uniformly across the whole plan. Homogeneous values describe regular behaviour. Significant differences between zones show where to concentrate the inspection, and describe any rotational component of the response. It is the level of detail that takes the measurement from global performance to a localised indication on the structure.

Visual inspection is required and remains necessary: it allows residual deformations, damage to the element, anomalous displacements and the condition of the connections to be detected. It returns the apparent state of the device at that moment. Instrumental measurement of accelerations across the isolation plane adds the information on performance during the event, which direct observation does not provide. The two activities answer different questions and are used together.

What is needed are the acceleration recordings on the two sides of the isolation plane during the event, and a technical interpretation comparing them with the behaviour expected from the design. MOSI delivers this work in a post-event report signed by a structural engineer, reporting the recorded accelerations, the ratios computed for each instrumented bearing and the assessment of the response. It is a technical document usable in decisions about reoccupation and in dealings with the parties involved.

The decision rests with the competent parties and is based on verification of the condition of the structure. The contribution of monitoring is to provide, within the first hours, measured data on how the structure and the isolation system responded, instead of an estimate. On buildings that have to stay operational this shortens the time between the event and the decision, and makes the decision documented. The new INRCA hospital in Camerano was instrumented with this purpose.

Seismic isolation is applied where operational continuity or the value of the contents justify the additional protection: healthcare facilities, school buildings, corporate headquarters, logistics and production hubs, refurbished residential complexes, buildings housing valuable assets. The measurement principle remains the same in all cases, because it depends on the device and on its position in the structure rather than on the intended use of the building.

In its base configuration BBOX 2.0 acquires accelerometer data, from which peak accelerations, displacements, interstorey drift and the dynamic parameters of the structure are derived, along with inclinations and thermal data.

With the expansion units the system integrates sensors of other kinds: strain gauges, crack gauges, advanced inclinometers, displacement transducers, environmental sensors and water level sensors.

Interstorey drift is the relative displacement between two consecutive floors of a building, expressed relative to the storey height. It is a code-defined damage indicator: comparing it with design limits gives a quantitative picture of the condition of the structure after an event.

They are the maximum acceleration values recorded during the event, at foundation level and at the floors. They allow the loading actually experienced to be compared with the loading assumed at design stage.

Displacements are obtained by numerical integration of the accelerometer signal and describe the actual deformation of the structure during the event.

Inclinations make it possible to follow the attitude of a structure or of one of its elements over time. On towers, bell towers and slender structures, inclination is provided by the base configuration itself, and how it evolves is the first indicator of settlement in progress.

Because temperature changes the dynamic parameters of a structure: every BBOX 2.0 sensor measures it, which makes it possible to compensate for its effect and to read the observed variations correctly. Environmental quantities recorded by additional sensors, such as humidity, also help interpret phenomena such as crack opening.

The BBOX 2.0 datalogger acquires sensors with a 4-20 mA output through the ESA expansion units. Each unit handles up to six sensors and one datalogger supports up to six units.

This makes it possible to bring instruments of different kinds into a single data stream, including those already present on the structure, which matters on bridges and infrastructure where instrumentation is often heterogeneous.

The number depends on the geometry of the structure, the objectives of the monitoring and the parameters to be acquired. The aim is to identify points that represent the behaviour of the structure, without instrumenting every element.

To give an order of magnitude from real installations: a 48,000 m² manufacturing plant is followed by 32 sensors, a road bridge by 10, the bell tower of a church by 4.

In buildings, at significant points such as the base, upper floors and relevant structural nodes. On bridges and viaducts the layout depends on spans, bearings and the elements to be observed. The configuration is defined at design stage for each structure.

The client receives technical reports interpreted and signed by a qualified structural engineer. The data and the platform are the means; the technical document is what gets delivered and what decisions rest on.

There are two types of report, depending on the mode that produces them.

It is the document issued at a defined interval under ordinary operating conditions. It reconstructs how the dynamic behaviour of the structure has evolved, compares the measured parameters against the recorded history and flags significant changes, indicating the areas where signs of degradation concentrate.

Over time, the series of reports forms a verifiable record of the condition of the structure.

It is the document produced after an earthquake or another extraordinary event, interpreted and signed by a structural engineer. It reports the accelerations, displacements and interstorey drifts recorded, with the severity and location of the effects detected, and compares the values with the design limits. It provides the technical basis for decisions on the use of the structure. On request, MOSI can produce a technical report on post-earthquake structural safety assessment.

The reports are prepared and signed by a qualified structural engineer, who takes professional responsibility for them. MOSI works on an ongoing basis with structural engineering professionals and practices.

The separation between who measures and who certifies is a deliberate choice of method: it makes the document a verifiable technical report rather than a supplier's statement about itself.

No. The reports provide the objective measurements on which the appointed engineer bases their assessment, direct inspections towards the elements that need them, and document the decision-making process.

On request, MOSI can produce a technical report on structural fitness for use after an earthquake. This remains distinct from the measures that fall to the competent authorities.

The interval is defined together with the client, based on the type of building, its use and the objectives of the monitoring. A plant in continuous operation and a protected heritage building followed for preventive conservation have different needs, and the frequency is set accordingly.

The historical series of reports forms a verifiable record of how the structure has behaved, signed by a structural engineer. It is documentation that can be used in a sale, in due diligence, in a refinancing or in discussions with an insurer.

The value lies in being able to demonstrate at any moment how the structure has behaved, with measured data rather than an after-the-fact estimate.

The main contribution concerns governance: a continuous, verifiable record of asset condition is documentary evidence usable in portfolio reporting and in physical risk management.

On the social side, monitoring concerns the safety of the people occupying the buildings and the decisions about returning after an event. On the environmental side the contribution is indirect: extending the service life of an existing building defers a reconstruction, in line with the whole-life carbon approach of the EPBD.

No. Sensors, acquisition units and data transmission components are applied to the structure without altering the load-bearing structure. The system can be installed on existing buildings according to a configuration defined at design stage.

Three elements: the sensors installed on the structure, the datalogger that acquires and transmits the data, and the web platform for consultation and remote management.

No. Installation is minimally invasive and is planned taking into account the operational continuity requirements of the structure. On a plant in production or a building in use this is often the first requirement, and the intervention is configured accordingly.

Yes. The web platform makes it possible to consult the data, access the history, view the main indicators and export the information without going to the installation site.

Yes, in standard formats, so that it can be analysed, shared or integrated into the workflows of engineers, consultants and authorities.

Yes. Recording interval, trigger thresholds and acquisition parameters can be changed remotely through the platform, without any intervention on site.

The system is fitted with an uninterruptible power supply, which keeps it running even during a blackout caused by a seismic event. This is a necessary condition, because the moment when the data matters most often coincides with the loss of power.

Yes. BBOX systems installed with the first generation are operational and MOSI continues to provide support for them.

For anyone considering the move to BBOX 2.0, the current generation adds continuous structural health monitoring, remote access to the data and periodic signed technical reports.

The cost depends on the number of sensors, which is a function of the geometry of the structure and the parameters to be acquired, on the monitoring modes activated, on any integration of sensors other than accelerometers, and on the duration of the service together with the frequency of the reports.

As a reference point: a system in its most contained configuration starts at around 15,000 euro. On large structures or where many points have to be instrumented, the figure grows in proportion to the number of sensors and the complexity of the system.

Annual periodic checks are scheduled. The system automatically reports any sensor malfunction, so that a fault is detected when it occurs rather than at the next check.

The malfunction is notified automatically and replacement is carried out with a minimally invasive intervention, without modifications to the structure and without interrupting monitoring at the other points.

In Italy there is no general obligation to carry out continuous structural monitoring on buildings. There are, however, contexts in which surveillance of the condition of a structure forms part of a process set out in legislation, and areas where documenting structural condition matters for obligations of a different kind, such as insurance.

The guidelines on the classification and risk management of existing bridges, adopted with Ministerial Decree 578/2020 and updated by Decree 204/2022, organise the management of structures by Classes of Attention. For the higher classes the prescribed process includes further investigation and surveillance activities.

Yes, for companies. The obligation to insure buildings, plant and machinery against earthquakes, floods and landslides stems from the 2024 Budget Law, with implementing rules set out in Ministerial Decree no. 18/2025. After a phase-in period by company size and sector, it has applied since 31 March 2026, with only fishing and aquaculture extended to 31 December 2026.

The policy covers the damage. Documenting what the event actually did to the structure remains a separate technical problem.

The Directive of the President of the Council of Ministers of 9 February 2011, which sets out the guidelines for assessing and reducing seismic risk for cultural heritage, recognises monitoring among the tools for tracking how structural damage evolves and for planning conservation work.

Directive (EU) 2022/2557 on the resilience of critical entities, transposed in Italy by Legislative Decree no. 134 of 4 September 2024, covers eleven sectors including health, energy, transport and drinking water. It requires entities identified as critical to assess their own risks, natural disasters included, and to adopt adequate measures to keep operating or restore service quickly after an incident.

Because downtime carries a direct and immediate cost. After an event the choice lies between restarting without knowing and stopping as a precaution for longer than necessary. In the 2012 Emilia earthquake, business interruption losses in the industrial sector exceeded the value of the physical damage to buildings.

Because an inspection captures the structure on a single day, while the bridge works every hour under traffic, thermal cycles and erosion. Continuous monitoring fills the space between one inspection and the next with measurements, and on structures in the higher Classes of Attention it addresses surveillance requirements.

Because rotations, settlement and material decay progress at a pace that a periodic inspection struggles to quantify. On towers and bell towers, inclination and how it evolves are the first indicator of settlement in progress, and every intervention has to be justified to the heritage authorities with measured evidence.

Because uncertainty multiplies by the number of households. Whoever manages the property has to decide whether and when residents can return, and a rapid fitness-for-use assessment after the event reduces both the risk of hasty decisions and prolonged waiting.

Because they host large numbers of people and operations whose shutdown carries an immediate cost, and because in ordinary life the condition of the building affects fitness-for-use assessments and the value of the asset.

Because they have to stay operational at precisely the moment when everything else stops. On these structures service continuity is a collective function, and the CER Directive has made the resilience of critical assets a matter of European law.