Robostness of precast monolithic concrete frames under special impacts

Abstract

This paper examines the problem of assessing the survivability of precast-monolithic reinforced concrete frames and frame structures in buildings under special accident loads. Survivability is defined as the system’s ability to redistribute the load between load-bearing elements after the failure of one of the elements in the structural system without causing any change in its geometry. The methodology is based on a two-level calculation scheme: first, the spatial frame of the entire building is considered as a whole, then a section of the frame in the zone of possible local failure. The calculation involves determining the stress-strain state under service loads, assessing dynamic post-loadings following the removal of an element, and calculating the structural system’s resilience parameter. Three-line deformation diagrams—‘moment–curvature’ and ‘shear force–shear angle’—are used, taking into account the formation of flexural and shift cracks, as well as the ductility of the joint between the precast and monolithic layers of the beams. The influence of the spacing of transverse reinforcement in the bearing zone of the beam was investigated. It has been established that, prior to the formation of shift cracks between the precast and monolithic layers of the beams, the beam cross-section behaves as a monolithic structure; once shift crack have formed, it behaves as a composite structure.