Structural Health Monitoring of buildings and infrastructure

SHM follows the dynamic behaviour of the structure in ordinary service, detects degradation-related changes while they are still small and reports them in a periodic report signed by a structural engineer.

What is Structural Health Monitoring

Structural Health Monitoring (SHM) is the process of identifying damage in a structure through measurements repeated over time. In the reference definition from the technical literature, damage is a change in the material or geometric properties of the structure, including boundary conditions and the connections between elements, that affects its performance.

For buildings and civil infrastructure, it means observing how the structure vibrates in ordinary service and comparing that behaviour with its own history. Every damage assessment is a comparison between two states, and in SHM the reference is the structure itself, measured at the start of monitoring: its baseline.

The periodic SHM report

Operational modal analysis: how vibrations are read

Every structure vibrates continuously under ordinary actions: wind, traffic, machinery, ground microtremors. Operational modal analysis (OMA) uses these ambient vibrations as excitation and derives the dynamic parameters from the accelerometer signals alone, with the structure in service.

In a study of nine masonry buildings in the network of the Seismic Observatory of Structures (OSS), run by the Italian Civil Protection Department, flexural and torsional frequencies generally fall between 2 and 6 Hz: BBOX 2.0 sampling covers this band with a wide margin.

Separating the effect of temperature from the degradation signal

Temperature changes the stiffness of materials and the boundary conditions, and with them the dynamic parameters. In the same nine buildings it proved to be the main driver of frequency variation, with maximum daily differences ranging from 1.5% to around 6%.

This is why temperature compensation is the condition for reading an SHM series correctly. Every BBOX 2.0 sensor includes a temperature sensor, and the relationship between dynamic parameters and temperature is derived from the baseline data: variations explained by that relationship are thermal, and those that fall outside the expected range are the signal to interpret.

A measurement that gains value every year

The baseline is built during the first period of monitoring and covers the range of climatic conditions the structure is exposed to, so that seasonal effects are included.

From then on, each year makes the comparison more precise: the record grows longer, the range of thermal variation is better described and an anomalous change becomes easier to recognise. MOSI keeps the long-term record for the entire duration of the service. Taken together, the reports form a verifiable record of how the structure has behaved, usable in a sale, a due diligence, a refinancing or in dealings with the insurer.

When degradation is a slow movement

Rotation of towers and walls, settlement, progressive opening of cracks: these processes advance over years. The BBOX 2.0 sensor also measures static inclination, with a resolution of 0.001° and a repeatability of 0.01°, and tracks rotations over time at the same points where it acquires vibrations.

When the situation calls for other quantities, the datalogger integrates up to 36 additional sensors with 4-20 mA output through ESA units: crack meters and displacement transducers on cracks, strain gauges on structural elements, advanced inclinometers, temperature and humidity sensors. Recording crack opening together with environmental parameters is the practice indicated in the literature for distinguishing real movement from thermal cycles.

Among the representative installations is the bell tower of the church of San Nicola di Bari in Camposanto (Modena, Italy), restored in 2016 after the 2012 earthquake, where inclination is tracked over time.

SHM and regulations: existing bridges and ISO standards

For existing bridges in Italy, the Guidelines adopted by Ministerial Decree 578/2020 and updated by Decree 204/2022 provide for the installation of periodic or continuous monitoring systems on bridges in the high and medium-high attention classes (classi di attenzione, the risk categories the Guidelines assign to each bridge) (§1.3), described in the chapter on instrumental monitoring (§7.6). Internationally, ISO 16587:2004 sets out the performance parameters for condition monitoring of buildings, bridges, towers and dams in service.

Where to follow a structure over time

• Bridges and viaducts

  How the structure's behaviour evolves, for the attention classes that require monitoring.

• Heritage buildings

  Inclination and dynamic parameters of towers, bell towers and masonry, with the effect of temperature compensated.

• Industrial and logistics sites

  The industrial building followed over the years, with the zone affected by degradation marked on the plan.

• Residential buildings

  A record of the condition of apartment buildings and managed property portfolios.

• Office and retail buildings

  The documented condition of the premises, for management, due diligence and value enhancement.

• Critical infrastructure

  The long-term behaviour of facilities that must stay operational, including seismic isolation systems.

The same sensors record the response during an event

In the base configuration of BBOX 2.0, Structural Health Monitoring runs alongside seismic monitoring: when an acceleration exceeds the threshold, the same network records the event. The baseline built up over ordinary years becomes the reference for reading the structure after the earthquake.

Technical and regulatory references

• Farrar C.R., Worden K., An introduction to structural health monitoring, Philosophical Transactions of the Royal Society A 365, 2007.
• Worden K., Farrar C.R., Manson G., Park G., The fundamental axioms of structural health monitoring, Proceedings of the Royal Society A 463, 2007.
• Brincker R., Ventura C., Introduction to Operational Modal Analysis, Wiley, 2015.
• Sivori D., Merani M.G.B., Bocchi F., Spina D., Cattari S., Environmental effects on the experimental modal parameters of masonry buildings: experiences from the Italian Seismic Observatory of Structures (OSS) network, Journal of Civil Structural Health Monitoring 15, 2025.
• Italian Ministry of Infrastructure and Transport, Guidelines for risk classification and management, safety assessment and monitoring of existing bridges (Linee Guida per la classificazione e gestione del rischio, la valutazione della sicurezza ed il monitoraggio dei ponti esistenti), Ministerial Decrees 578/2020 and 204/2022.
• ISO 16587:2004, Mechanical vibration and shock, Performance parameters for condition monitoring of structures.

Let's design SHM for your structure

Sensor positions, acquisition intervals, baseline duration and report content depend on the structure and on the goals of the monitoring. The MOSI team defines the configuration with you.