Methodology of field testing and analytical assessment of the residual load-bearing capacity of reinforced concrete structures after fire
DOI:
https://doi.org/10.33271/crpnmu/86.217Keywords:
reinforced concrete structures, fire, residual load-bearing capacity, non-destructive testing, deflection, crack resistance, reinforcement-to-concrete bond, damage assessmentAbstract
Purpose. To develop and substantiate a methodology for assessing the technical condition and residual load-bearing capacity of reinforced concrete structures after fire exposure based on the comprehensive application of in-situ inspection, non-destructive testing, and laboratory testing.
Methods. The methodology is based on the results of sampling damaged structural elements, measurements of deflections and cracks, determination of residual strength and stiffness, as well as safety requirements for testing. The methodology was further developed with consideration of current international practices and provisions of fib, Eurocodes, ISO, and ACI. A multilevel diagnostic framework is proposed.
Results. Analytical relationships for the coefficients characterizing the residual physical and mechanical properties are presented. The necessity of determining the temperature profile across the cross-section is substantiated. It is demonstrated that assessing concrete strength alone is insufficient for a reliable evaluation of the post-fire condition of reinforced concrete structures. A diagnostic sequence is proposed: “fire scenario – damage map – NDT – laboratory testing – structural analysis – in-situ load testing – integrated assessment.”
Originality. Analytical relationships have been established for the quantitative assessment of the principal residual physical and mechanical properties of reinforced concrete structures after fire exposure. A system of coefficients, namely (kfc), (kE), (kM), (kcr), and (kb), is proposed to characterize the degree of preservation of the corresponding structural properties after fire exposure. The post-fire assessment methodology has been improved by integrating the results of visual inspection, non-destructive and laboratory testing, in-situ load testing, and the finite element method into a unified system for the quantitative assessment of the technical condition and residual load-bearing capacity.
Practical Significance. The practical outcome is an algorithm for selecting an appropriate course of action, including continued operation, repair, strengthening, or demolition. The proposed integrated criterion is intended to provide a transparent basis for comparing the results obtained from different diagnostic methods. The methodology is applicable to real structures for which the thermal history and material properties are only partially known; therefore, it provides for the calibration of indirect assessment methods using reference specimens, thereby increasing the reliability of engineering conclusions and ensuring structural safety.
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