Crack monitoring: a critical safety requirement for stadium stands

Around the world, several sports facilities have been partially or temporarily closed in recent years due to structural safety concerns. In 2019, part of the roof structure of the AFAS Stadium in Alkmaar (Netherlands) collapsed as a result of progressive structural weaknesses in steel elements. Although no spectators were present at the time, the incident highlighted how undetected structural defects can lead to sudden and serious failures.

While a total stand collapse remains a rare event, it cannot be entirely ruled out, particularly in aging or heavily loaded structures. In this context, regular crack monitoring is a crucial component of preventive maintenance and responsible asset management.

Identifying the causes of cracking in stadium stands

Cracking in stadium terraces can have multiple origins. Whether the stand is constructed in concrete, timber, or steel, it is subjected to various stresses that may generate cracks:

• Repeated dynamic loads caused by crowd movements and jumping during events;
• Temperature variations leading to differential material expansion;
• Water ingress and freeze–thaw cycles in weather-exposed areas;
• Soil settlement or subsidence beneath the structure’s foundations;
• Material aging and corrosion of load-bearing elements over time.

These phenomena may result in cracks appearing in the stands, typically at risers, landings, expansion joints, or concrete construction joints.

Such cracks often reveal deeper structural disorders (for example: reduced load-bearing capacity of an element, excessive shear stresses, or differential displacement between elements).

Without appropriate monitoring, these defects may worsen over time and, in the worst-case scenario, compromise the stability of the structure. Implementing regular crack monitoring makes it possible to verify structural stability and to plan maintenance or strengthening works in a timely manner.

Structural monitoring: a matter of responsibility

Under current regulations governing public-access buildings operators of sports infrastructures bear full responsibility for spectator safety. This implies maintaining up-to-date knowledge of the structural condition of the stands and documenting the monitoring of any defect, even minor, that could affect structural integrity.

In the absence of monitoring and traceability of inspections, facility managers may face sanctions in the event of an incident. Conversely, implementing regular crack monitoring constitutes an essential preventive measure, in line with professional best practices and regulatory requirements. It is a responsible management decision aimed at preventing any risk, however small, of collapse or structural failure.

Recommendations for sports facility managers

To ensure regulatory compliance and public safety, it is advisable to adopt a structured approach to stand monitoring. The main recommended steps are as follows.

Carry out an initial structural assessment

Before implementing any monitoring system, a comprehensive technical inspection of the structure should be performed. This initial assessment, generally entrusted to a specialized engineering consultancy, aims to accurately evaluate the structural condition, identify visible defects (cracks, spalling, corrosion, deformation), and formulate hypotheses regarding their origin.

In practical terms, inspection teams visit the site to directly examine the relevant structures. At this visual stage, several elements enable a first level of diagnosis:

• Shape and orientation of cracks (vertical, horizontal, diagonal);
• Location of defects within the structure (risers, supports, cantilever areas);
• Crack pattern (open, stepped, branched, fine, or active);
• Chronology of appearance, if known, often based on discussions with the operator or analysis of previous documentation.

These initial observations guide further investigations. At this stage, non-destructive testing is often carried out to better characterize the structural pathologies:

• Measurement of crack width and depth;
• Detection of near-surface reinforcement using a cover meter;
• Identification of deeper reinforcement using structural radar;
• Sonic testing to estimate the depth of concrete cracking.

The initial assessment provides an objective evaluation of the defects, determines their severity, and prioritizes areas to be instrumented. It forms the technical foundation of any short- and medium-term structural monitoring strategy.

Install appropriate crack gauges on identified cracks

Following the initial assessment, certain cracks may require instrumented monitoring, particularly if their evolution is uncertain or if they affect structurally sensitive areas.

Installing suitable crack gauges enables long-term monitoring by accurately measuring variations in crack width, shear movement, or displacement between cracked elements. This monitoring is essential to distinguish between a stabilized crack and an evolving defect that may require intervention.

By integrating these data into a structured maintenance plan, instrumented monitoring helps anticipate structural risks and prevents localized deterioration from compromising the overall safety of the structure.

Continuously monitor critical structural areas

Certain areas of a stand are more exposed to extreme stresses than others: for example, junctions between stand modules, cantilever sections, or areas permanently exposed to weather conditions. If left unmonitored, these sensitive zones could ultimately lead to major structural failure (including partial stand collapse).

It is therefore recommended to install measurement sensors in these areas, ideally connected sensors capable of transmitting data at regular intervals to quickly detect any abnormal evolution.

Centralize measurements in a secure interface

To ensure monitoring consistency and data reliability, it is advisable to consolidate all recorded measurements on a dedicated digital platform. Such a centralized interface allows visualization of crack evolution trends, configuration of automatic alert thresholds, and generation of actionable reports. It also provides secure archiving of historical data, ensuring long-term traceability as required by regulations.

Periodically review the monitoring plan

A stadium’s operating conditions and structural state evolve over time. It is therefore essential to periodically review the monitoring system based on observed results and any structural works carried out.

This continuous improvement approach makes it possible to anticipate maintenance needs and proactively manage structural risks – preventing a simple crack, if it reappears or worsens, from eventually leading to a far more serious issue.

Saugnac solutions for crack monitoring

To address these structural safety challenges in sports infrastructures, Saugnac Jauges offers a comprehensive range of measuring instruments specifically designed for crack monitoring. These technical solutions integrate into a preventive maintenance strategy while meeting the regulatory requirements applicable to public-access buildings.

The initial assessment

The first stage of monitoring consists of accurately evaluating crack width and severity. The Saugnac enhanced crack ruler is a portable instrument that instantly quantifies crack width with an accuracy of approximately 0.1 mm.

This tool greatly facilitates the initial diagnosis by providing fast and reliable measurements, helping classify cracks according to their significance. The analysis obtained at this stage makes it possible to target areas requiring priority monitoring and to select the most suitable sensor type for each crack.

Installing gauges on identified cracks

Once cracks have been identified and characterized, the Saugnac G1 gauge range provides a monitoring solution adapted to each configuration:

• G1 standard gauge: weather-resistant, ideal for exposed structures.
• G1.1 gauge: for precise monitoring to 1/10 mm in covered areas.
• G1.2 transparent gauge: discreet and suitable for highly visible areas.

For structures requiring simple and precise monitoring, the G1+ gauge offers digital readings to 1/20 mm accuracy.

For differential displacements frequently observed at risers and landings, the G3 gauge accurately measures the evolution of vertical and horizontal offsets, indicating any structural movement.

Monitoring using a removable gauge

The E1 removable crack meter is based on a patented mounting system with fixed base plates ensuring measurement repeatability. It measures crack opening, shear displacement and, under certain conditions, differential offset using a specific accessory.

The PA12 base plates are suitable for outdoor installation. This material is resistant to sunlight exposure, humidity, and temperature variations.

Continuous connected monitoring

The R1 connected crack meter automatically transmits data via a digital platform, with multi-year autonomy thanks to its long-life battery. It is well suited to hard-to-access stands or areas requiring close monitoring.

The R5 connected inclinometer measures tilt evolution on two axes, enabling detection of progressive structural deviation.

These instruments are compatible with Saugnac.app, which centralizes readings, facilitates remote access, report generation, and data history management. This digital interface ensures the documentary traceability required by public-access building regulations and supports decision-making in the event of concerning structural evolution.