Simplified analytical method for the robustness assessment of precast reinforced concrete structural systems

Abstract

The article presents the simplified implementation of alternative load path method based on the energy balance approach. This method should be used to check the global resistance of a damaged structural system after the occurrence of an accidental event. Basic assumptions of simplified analytical models for modelling resistance of horizontal ties in a damaged structural system, taking into account the membrane (chain) effects, were presented. An approach to modelling the dynamic resistance of a damaged structural system based on the energy balance method is described. Calculated dependencies for checking the robustness of a prefabricated multi-storey building with hollow-core slabs after the loss of the central column are proposed and considered using an example. On the considered example, a comparison of the required tie sections area with the dynamic resistance designed using the energy balance method (EBM) and according to the current standards, and a statistical assessment of the reliability of the load-bearing capacity models are carried out. In the end, a brief algorithm for the simplified calculation of the dynamic resistance of a damaged structural system is proposed.

Experimental and theoretical study of the reinforced concrete flat slabs with the central support loss

“…The methods based on the principles of macro-modeling are more promising methods for modeling damaged (modified) structural systems when its robustness checks, than methods based on continuum modeling [37]. According to macro-modeling rules, linear elastic behavior beams and slabs modeled the elastic behavior of the structural system.…”

“…Moreover, nonlinear dynamics procedure consists of sufficient uncertainties and the required computational resources will further increase if all typical column removal scenarios in building need to be evaluated [19]. As was shown in [37], it is thus necessary to develop a simplified and accurate methods to assist in the quick assessment of the progressive collapse fragility of RC structural systems considering the dynamic effects.…”

“…Current provisions [2,3,7,9,13,33,34] regulate that the structural systems should be evaluated under systematical alternate path (AP) analyses that comprehensively consider various column removal scenarios. Most structural codes [2,3,7,9,13,33,34] and current studies [8,17,19,30,37] commonly considered the removal scenarios of one specific column or some of the typical columns (i.e. corner column, edge column and internal column) usually on the ground story of building.…”

“…In most cases, the robustness of structural systems is checked by indirect methods, such as the tie force method, aimed at a general increase in the plasticity (ductility) and integrity of structural systems. However, as it was shown in [1,36,37], such methods are based on pre-accepted, constant values of limit deflections and do not take into account the real deformability of the tie elements. In some cases a such simplification can lead to an inadequate assessment of the design resistance and overestimation of the robustness of the damaged system.…”

“…The quantitative criterion for robustness assessment can be found with usage energy-based method as the ultimate dynamic response of the structural system at the first half-cycle of oscillations after sudden removal of vertical load-bearing element [19,37]. In accordance with the energy-based method a complete nonlinear quasi-static response of the damaged structural system is required for calculation of this response.…”