MODELING THE ATTENUATION CHARACTERISTICS OF URBAN VIBRATIONS AND THEIR IMPACT ASSESSMENT ON INFRASTRUCTURES IN AREQUIPA, PERU
Rapid and unplanned urban growth in developing countries can lead to increased urban vibrations, which may have an adverse impact on the urban and archaeological infrastructures. The severity of damage is a function of several site-specific variables (i.e., distance, speed, weight, conditions and type of soil, and age of the building, among others) and hence the numerical prediction equation requires local adjustments based on field measurements. Hence, for the present study, measurements have been performed in densely populated areas of Arequipa, the second economic hub and densely populated (about 1 million inhabitants) city in Peru.
The vibrations were analyzed using DIN 4150-3 standards to evaluate the peak particle velocity (PPV) patterns in the frequency domain. The regression fit models were obtained using the generalized Levenberg-Marquardt inversion approach. The analysis of geometric and material damping coefficients was automated using a neural network for the different sources evaluated.
The results show railway traffic records where the PPV = 18 mm/s with frequencies of 30 to 60 Hz; in vehicular traffic records, the PPV = 40 mm/s with resonance frequencies of 10 and 20 Hz; while for records of the compaction roller, the PPV = 30 mm/s with frequencies of 20 to 60 Hz. Possible structural damage to the buildings was estimated due to the vibrations generated by the compaction roller. A resonance effect was also evident in bridges; in both cases the records exceeded the second limit of Standard DIN 4150-3, while in railway traffic sources, possible structural damage to sensitive material was estimated.
The ground vibration attenuation analysis marked an inverse relationship between the maximum velocities and the distance from the source, which vary depending on the geometric and material damping. In cohesive soils such as concrete slabs, with compact granular material, high porosity and low humidity, the wave propagation speed is greater, reducing the foundations’ stresses and the direct transmission to the structure. While, in silty sandy soils, with lower porosity and higher humidity, the propagation speed decreases, which increases the stress transmitted in the foundations.