- BUILDING STRUCTURES, BUILDINGS AND FACILITIES
- Special Limit Condition Of Reinforced Concrete Structures And Its Normalization
- UDC 624.012.3 DOI: 10.33622/0869-7019.2020.05.04-09

**Nikolay N. TREKIN**, e-mail: otks@narod.ru

**Emil N. KODYSH**, e-mail: otks@narod.ru

Central Scientific Research and Project Experimental Institute of Industrial Buildings and Constructions, Dmitrovskoe shosse, 46, korp. 2, Moscow 127238, Russian Federation

**Abstract**. One of the ways to improve the resilience of buildings in the event of failure of the bearing structure or emergency, seismic effects is a more complete account of the behavior of elements and their mates at short-term action of loads and dynamics of change of the scheme of the bearing system of the building. To do this, it is advisable to allow more cracks to open, the development of deflections and partial destruction of some sections, which contradicts the current criteria for the first and second limit states that ensure the operational suitability of structures and buildings. Therefore, it is necessary to introduce specific standards of a special limit state for structures. A special limit state is the stage of operation of the structure after reaching the load-bearing capacity for the first and the deformation limits for the second limit states. Exceeding this state, in which the structures do not fully meet the functional requirements, leads to their collapse. The implementation of this limit state is most appropriate in load-bearing systems with a high degree of static indeterminability and constructive interaction of all bearing elements. The introduction and consideration of a special limit stress-strain state of reinforced concrete structures make it possible to detect significant strength and deformation reserves, even after significant fragmentation of the compressed concrete zone and, as a result, reducing the working section of the structure. As the main criteria of a particular limit state for reinforced concrete structures, it is recommended to adopt: the ultimate deformations of compressed concrete and tensile reinforcement with higher values than permissible under normal conditions; as well as the deflections of elements, provided that the minimum allowable length of the zone of bearing and anchorage of reinforcement.

**Key words**: stability against progressive collapse, special limit state, crack opening, deflections, partial destruction of cross-sections, extreme deformations of concrete. - REFERENCES

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