Effect of ambient vibrations and earthquake ground motions on the response of a 14-story building.

Abstract:

Structure analysis and evaluation by continuous monitoring in areas where the seismic activity and the ambient vibrations are quite frequent, has recently become a priority field in seismology research in Colombia.

In a recent investigation, a 14-story building located in the downtown area of Bogota – Colombia, has been instrumented with six 3-component ETNA-2 accelerometers. One of the sensors is located in the basement of the building, and the others are distributed to the 2nd, 5th, 8th, 11th, and 14th floors. The building array recorded continuously starting June 2019 until February 2020. Among the continuous data available, more than 30 M4+ earthquakes were recorded, most of them coming from the Bucaramanga Nest, but also from other regions like Eastern Mountain Range where a M6 earthquake was recorded followed 15 minutes later by a M5.8 aftershock, showing a significant change in the building response using both earthquake and ambient vibration data. Changes both in wave speed and damping are observed.

In addition to the building response to earthquakes, periodic changes are also observed associated with the amplitude of the ambient vibrations, between day and night or weekdays and weekends.

Combining all the available data has provided fundamental information about the dynamic response of the building, how fundamental frequencies may vary due to earthquake ground motions or other environmental variables like weather conditions.

The 250-day long monitoring campaign of the building using deconvolution interferometry and measuring the velocity variations from the resulting impulse response functions (IRF), provides a unique opportunity to better understand the dynamic response of buildings to ground motions.