THE DETERMINATION OF THE RESIDUAL LIFE OF BUILDING STEEL STRUCTURES BY THE RELIABILITY INDEX INDICATORS

Abstract

 In order to assess the operational safety of steel constructions, the paper analyzes the 
principles  of  calculating  the  safety  of  structural  steel  constructions  with  consideration  for  the 
reliability  index  β  at  all  phases  of  constructions  operation  and  the  design  fundamentals  of  the 
reliability index β for both new constructions (at the design stage) and structural steel constructions 
in the conditions of the long-term operation. 
The task of safety and reliability calculations, first of all, consists in assigning normalized safety 
parameter values, i.e. normalizing the reliability index, the value of which should be strictly related 
to the consequence classes (CC), which are determining for setting the reliability coefficients for 
further calculations while designing the constructions. 
The article considers the calculation values β of the reliability index for constructions operated 
beyond  the  time  limit  for  operation,  with  accumulated  defects  and  damages.  To  improve  the 
mechanism  for  calculating  the  reliability  index  value  for  the  constructions  operated  beyond  the 
maximum operating limit, with accumulated defects and damages, several tasks were set to determine 
such values β of the reliability index below which the construction is no longer considered to be 
operational and to define the reliability index values β for possible performance of renovation works 
(reconstruction, refurbishment) to strengthen and extend the remaining structural lifetime. 
Thus, emphasizing all of the aforementioned, the main conclusions to the article should be 
specified: at the stage of solving the issue of calculating the reliability index for structures being 
operated over the projected service life, with damages and initial defects accumulated during the 
operation period, it is required to perform their review and determine two main criteria for solving 
the issue of determining the reliability index, namely: to set such values of the reliability index below 
which the structure will be no longer operational, to define and set such values of the reliability index 
at which it is possible to carry out renovation works on steel structures, their reconstruction or repair.  
Considering the possibility of changing the reliability index compared to a new structure, given 
that the residual service life may be shorter than the design one, taking into account the economic 
factors and factors of probability of losing a person’s life, setting of such reliability index values is 
necessary for further possibility of the service life extension of a structure and determination of its 
residual life.