Explosion in the Port of Beirut: campaign to assess buildings impacted by the catastrophe

Acquisition system (CitySharkTM and Lennartz 5s) used to measure ambient vibration in damaged buildings in Beirut, following the explosion on 4 August 2020. (Source: C. Cornou, IRD/ISTerre)

Following the dramatic explosion on 4 August 2020 in the Port of Beirut, the ISTerre laboratory1 has contributed expertise to evaluate the structural integrity of buildings in Lebanon. In late August 2020, an online survey was also launched in conjunction with Lebanese researchers, targeting people who felt the explosions in the capital. The objective was to better understand the behaviour, movements and mobility of people during disasters.

In November 2020, the Institute of Earth Sciences (ISTerre) in Grenoble, the Cerema in Nice, and the Lebanese University and Notre Dame University in Beirut conducted a campaign to evaluate the structural integrity of buildings impacted by the explosion in the Port of Beirut on 4 August, using vibration.

Ambient vibration can be used to measure the dynamic properties of buildings or bridges as part of structural health monitoring (SHM). This is a non-destructive method that provides information on a building's overall state of damage after an extreme event, like an earthquake or explosion.

This experiment in the Port of Beirut was funded by the National Institute of Sciences of the Universe at the National Centre for Scientific Research (INSU-CNRS) and Research Institute for Sustainable Development (IRD). It involved measuring the dynamic properties of structures using ambient vibration (resonance frequencies and shock absorption). More than 100 buildings were able to be tested in just a few days using a lightweight, tried and tested acquisition system, developed by ISTerre in the early 2000s. These buildings were located at varying distances from where the explosion originated and had known modal parameters before the explosion.

Between 2012 and 2014, a similar assessment campaign was carried out in Beirut by ISTerre and Lebanon's Notre-Dame University on a total of 328 buildings (Salameh et. al., 2016). Most were located less than 2 km from the port. The changes in the buildings’ dynamic properties pre- and post-explosion made it possible to analyse the variation according to the level of damage, in relation with the distance from the explosion and the type of construction, evaluate the parameters most sensitive to damage, fine-tune the characterisation methods and break down the damage caused by the explosion and the seismic wave generated.

The initial results confirm the efficiency of modal parameters in detecting damage, but also reveal a wide variety of changes within a group of identical buildings.

1 ISTerre is a mixed research unit, under the supervision of Université Gustave Eiffel, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS and IRD.