ON ONE POSSIBILITY OF THE ASSESSMENT OF PROGRESSIVE COLLAPSE OF STRUCTURES IN FIRE

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. The paper proposes an algorithm for determining the responsible elements in the progressive collapse of a building in fire. The algorithm is based on the use of the most flexible calculation schemes and iterative procedure of energy portraits of the building according to the Vasilkov-Shmukler criterion. The implementation of the algorithm is demonstrated on the example of determining the responsible elements of a real residential complex in Lviv. The object of the study is the residential complex «America», which consists of two 17-storey paired blocks and a block of two-storey shopping centre, located between them. Structurally, each of two buildings is a monolithic reinforced concrete frameless structure with voided overlappings made according to «Monofant» technology. At the beginning, all the initial data related to the structural scheme of the building are collected and systematized, such as geometric parameters, physical and mechanical characteristics of materials, engineering and geological conditions, loads and impacts. Then the computational model of the building is created. Herein the «Lira» software based on finite element method is used. Based on the results of the generated initial data and the building model, a static calculation is performed. After verification of compliance with the requirements for structures of the 1st and 2nd groups of limit states, the analysis of possible fire scenarios and modes is performed. The next step is determination of temperature fields, which gives the possibility to generate temperature loads. In general, 16 separate downloads were formed. The first download included all vertical loads from static calculation, and the next 15 downloads - all vertical loads and 1 different temperature load. The main aspect in the proposed algorithm is the criterion for selecting the responsible elements based on the approach of building of energy portrait of structure. After Vasylkov-Shmukler criterion, it is proposed to determine the values of the strain energy density for each finite element and strain energy of the whole system. According to the results of compiling 15 scenarios of emergency fire on one of the buildings and determining the largest values of strain energy density, the most dangerous accident scenario for the whole complex was identified.