Case Study of a Heavily Damaged Building during the 2016 MW 7.8 Ecuador Earthquake: Directionality Effects in Seismic Actions and Damage Assessment

Abstract

In this work, the directionality effects during the MW 7.8 earthquake, which occurred in Muisne (Ecuador) on 16 April 2016, were analyzed under two perspectives. The first one deals with the influence of these effects on seismic intensity measures (IMs), while the second refers to the assessment of the expected damage of a specific building located in Manta city, Ecuador, as a function of its azimuthal orientation. The records of strong motion in 21 accelerometric stations were used to analyze directionality in seismic actions. At the closest station to the epicenter (RRup = 20 km), the peak ground acceleration was 1380 cm/s2 (EW component of the APED station). A detailed study of the response spectra ratifies the importance of directionality and confirms the need to consider these effects in seismic hazard studies. Differences between IMs values that consider the directionality and those obtained from the as-recorded accelerograms are significant and they agree with studies carried out in other regions. Concerning the variation of the expected damage with respect to the building orientation, a reinforced concrete building, which was seriously affected by the earthquake, was taken as a case study. For this analysis, the accelerograms recorded at a nearby station and detailed structural documentation were used. The ETABS software was used for the structural analysis. Modal and pushover analyses were performed, obtaining capacity curves and capacity spectra in the two main axes of the building. Two advanced methods for damage assessment were used to obtain fragility and mean damage state curves. The performance points were obtained through the linear equivalent approximation. This allows estimation and analysis of the expected mean damage state and the probability of complete damage as functions of the building orientation. Results show that the actual probability of complete damage is close to 60%. This fact is mainly due to the greater severity of the seismic action in one of the two main axes of the building. The results are in accordance with the damage produced by the earthquake in the building and confirm the need to consider the directionality effects in damage and seismic risk assessments.

Correction Factors to Account for Seismic Directionality Effects: Case Study of the Costa Rican Strong Motion Database

“…As for RotD100, the ratio falls within the range of 1.23 to 1.29. Notably, all the obtained ratios demonstrate an agreement with the findings of similar studies conducted in other regions [1][2][3]6,14,21,22].…”

“…As for RotD100, the ratio falls within the range of 1.23 to 1.29. Notably, all the obtained ratios demonstrate an agreement with the findings of similar studies conducted in other regions [1][2][3]6,14,21,22]. The results of the directionality effects are applied to improve the knowledge of PSHA, which does not consider the increased hazard due to this effect, and they have been performed in many countries with similar findings, although with some differences.…”

Time-domain deconvolution procedure for elastoplastic materials: Application to the Treasure Island site during the 1989 Loma Prieta earthquake

“…Even though epicentres occurred at considerable distances (80 km, 350 km, and 150 km, respectively), significant damage took place in urban areas due to the amplification of seismic waves caused by local site conditions. These observations confirmed the need of carrying out details studies and provide tools to improve the assessment of seismic risk, including phenomena that could increase the potential of damage [4] , [5] , [6] , [7] .…”