ASSESSMENT OF SEISMIC VULNERABILITY OF BUILDING STRUCTURES IN ALMATY, KAZAKHSTAN

Abstract

Kazakhstan's southern and southern-eastern regions exhibit intraplate seismicity, which is characterized by numerous destructive earthquakes. The major metropolis in this area, Almaty, features a variety of buildings with different materials for construction and seismic-resistant systems. Numerous buildings were constructed during the Soviet Union era with inadequate seismic-resisting design, necessitating an empirical and analytical evaluation of their ability to withstand significant earthquakes. Thus, it is necessary to evaluate the seismic risks associated with these structures. This study adopted both empirical and analytical techniques to assess the seismic vulnerability of these structures in two phases. In the first phase, the macro-level seismic assessment was conducted on residential, industrial, and commercial buildings. The European Macroseismic Scale was used to categorize these structures according to their seismic vulnerability. Different earthquake intensities and peak ground accelerations led to the development of vulnerability curves as well as the probability of damage for each damage grade chart. The likelihood of damage in the Almaty region was established for design basis and maximum considered earthquakes. Residential buildings made of unreinforced masonry and wood sustain significant damage, and in some cases, complete collapse when subjected to earthquakes of the maximum magnitude that are normally taken into account. While industrial and commercial buildings made of unreinforced masonry sustain the heavy to very heavy damage. Since damaged and precast concrete buildings are likely to sustain heavy to very heavy damages, an additional analytical assessment was necessary. In the second phase, the analytical assessment was carried out to study the detailed performance and behavior of the pre-cast emulated moment frame buildings under the earthquakes. For this purpose, two pre-cast emulated moment frames were selected named VP and VT series, which were constructed between the 1970s to 1990s. Based on the data collected from the government agency, OPENSEES was used to produce two-dimensional nonlinear models for these buildings. The next step was to conduct increased amplitude dynamic analyses using 16 previously recorded strong ground motions, which share similar fault features with the Almaty. The results of the investigation were used to produce fragility curves using two parameter lognormal distribution function for Immediate occupancy, life safety and collapse prevention as per FEMA 356, which were subsequently used to evaluate the building structures' ability to withstand seismic activity.