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Impact of the 4 August 2020 Beirut, Lebanon, Port Explosion on Dynamical Building Properties

Session: Analyses and Implications of the 4 August 2020 Beirut Explosion Series [Poster]

Type: Poster

Date: 4/23/2021

Presentation Time: 11:30 AM Pacific

Description: 

Thousands of buildings have been more or less damaged after the August 4, 2020, explosion in Beirut, Lebanon. Operational Modal Analysis method based on seismic ambient noise recordings in buildings can be used to assess their modal parameters (e.g. resonance frequency). This is thus a valuable tool to assess and monitor the structural health of civil engineering structures. Between 2012 and 2014, a seismic ambient noise campaign was carried out on a set of 328 RC buildings in Beirut covering various building typologies and soil types (Salameh et al., 2016). These measurements were used to derive empirical relationships between the number of stories and the fundamental resonance frequency. Following the August 4, 2020 explosion in Beirut, a set of these buildings (132) of various height and located at different distances from the explosion was re-measured in order to evaluate if the variation in resonance frequencies before and after the explosion can be related to buildings damage. Some buildings (41) located very close to the port area were also measured in order to check variation in resonance frequency compared to the empirical relationship. Results show a decrease in resonance frequencies ranging from up to 20% to about 3% for buildings located 1 km away to about 4 km from the port area, respectively, taller buildings exhibiting systematically a higher relative decrease in resonance frequency before and after the explosion. Interestingly, we also observe a large variability of the difference of frequencies in-between buildings with the same height and located at a similar distance from the explosion, as well as between frequencies extracted from seismic sensor horizontal components aligned or perpendicular to the longitudinal direction of the buildings. Spatial decay from the explosion of difference in resonance frequencies are compared to the damage assessment of buildings inferred from satellite images or visual inspection. The contribution of the blast and the seismic waves generated by the explosion on the building damages is then discussed.

Presenting Author: Bertrand Guillier

Student Presenter: No

Authors