Assessment of shear wave velocity concept on the site specific analysis and its effects over performances of building codes

Abstract

Earthquakes’ effects on the ground especially to superstructures vary depending on the local site conditions. As the seismic waves move towards the surface, the dynamic behavior is affected by the depth of the bedrock, layer thickness, and the soil type. Site specific soil behavior analyses are carried out to estimate the seismic force spread from the bedrock to the ground along the soil layers and to determine the spectral properties of the site. During the transmission of the wavelength, the amplitude and frequency content change depending on the properties of the soil layers. Both the alteration of the dynamic properties of soil layers and the earthquake characteristics must be analyzed in order to predict the ground surface behavior. Turkey is one of the most important earthquake prone country in Europe and it is crucial to reduce any possible damage as a result of seismicity by taking the necessary measures. This study focuses on a region near North Anatolian Fault which is one of seismically active faults in Yalova region in Turkey. The goal is to understand the nonlinear site specific behavior along with the equivalent linear option using two boring data with similar shear wave velocity and site class. Eleven different earthquakes were chosen for the analysis. The fault type and the soil class are the main characteristics to determine those records. The spectral behaviors of the ground surface were obtained from different models and they were compared with three different building codes (the new Turkish Building Code (TBC 2018), the Eurocode8 (EC8) and the International Building Code (IBC)). Analysis show that 1) the performance of the building codes vary a lot to predict the surface behavior, 2) equivalent and nonlinear site response differ in terms of short and long period spectral behavior and 3) the determination of site classes from shear wave velocity solely may not be sufficient to understand the propagation of the wave and sandy or clayey behavior should also be considered in design purposes.