French infrastructure put to the test by the episodes of extreme cold

Extreme cold exerts a much more subtle — and sometimes critical — pressure on essential infrastructure, which is subject to complex mechanical phenomena, foremost among which is differential thermal expansion.

Cold, a mechanical phenomenon with very real effects

When temperatures drop, all materials contract, but not at the same rate. Concrete, steel, and copper react differently to the cold. When assembled within a single structure—a bridge, railway, or overhead power line—these differences in behavior generate internal stresses. If these stresses are not properly absorbed, they can lead to cracks, deformations, or breaks, sometimes without any visible warning signs.

Concrete incidents already observed on the ground

These phenomena are not theoretical. On bridges, a 10°C drop in temperature can cause a contraction of approximately one centimeter for a 100-meter structure. When expansion joints are blocked by frost or ice, the structure can no longer absorb these movements. In 2021, several bridges on the A10 motorway underwent inspections after cracks appeared due to winter conditions, according to the Nouvelle-Aquitaine Regional Directorate for the Environment, Planning and Housing (DREAL).

Railway infrastructure is also highly vulnerable. Steel rails can contract by nearly 24 centimeters per kilometer for every 20°C drop in temperature, increasing the risk of breakage without appropriate protective measures. In 2022, overhead line failures severely disrupted the Munich–Berlin ICE line when temperatures plummeted below -20°C, according to Deutsche Bahn. Overhead lines are a particularly striking example of differential thermal expansion: copper cables contract more than steel poles, increasing mechanical stress and the risk of failure.

Concrete solutions exist to secure structures during the winter period.

Faced with the mechanical stresses caused by low temperatures, proven technical solutions enable the diagnosis and improvement of critical infrastructure. For example, the company SITES provides services for the inspection and monitoring of expansion joints and pavement joints designed to absorb the contraction and expansion movements of structures, including during severe winter weather.

SITES also deploys sensor-based monitoring systems, enabling continuous measurement of key parameters such as temperature, displacement, and structural deformation. This data is used by teams to refine diagnoses, anticipate areas of weakness, and prevent problems before they become critical.

Upstream, SITES integrates the requirements of the Eurocodes in order to guarantee a design adapted to climatic constraints throughout the life cycle of the infrastructures.

Finally, during the most demanding winter periods, SITES supports facility managers in implementing enhanced maintenance and targeted inspection of sensitive cables and equipment to maintain the safety and performance of installations.