Ultimate State Evaluating Criteria of RC Structural Systems at Loss of Stability of Bearing Element

The paper deals with the deformation of reinforced concrete structural systems of multi-story buildings and structures under accidental impacts. One of these impacts is instantaneous removal of a bearing element of a system. Before this moment researches of survivability and resistance against progressive collapse of structural systems under such impacts were based on the strength criteria. At the same time instantaneous removal of structural element may be caused by loss of stability at evolutionary accumulation of corrosion damages or other physical impacts. That is why the deformation criteria of loss of stability of a structural system under accidental impacts are proposed in this paper. The energy approach and the mixed method of structural mechanics are applied to evaluate survivability and resistance against progressive collapse of a structural system at loss of stability of a bearing element. Two - level computational models are used to solve this problem. An example of calculation of 14-storey building under such impact in accordance to deformation criteria is presented. It is shown, that critical force, that lead the structural system to progressive collapse at evolutionary accumulation of damages is less then ultimate compressive force, which were calculated in accordance to strength criteria.