Reliability coefficients for nonlinear models of load-bearing capacity of beams with flexible web

Abstract

Introduction. A special class of thin-walled steel elements can be singled out, for which characteristic failure forms are accompanied by loss of local web stability with subsequent development of the post-critical stage, the so-called beams with flexible web. The effectiveness of application, including practical approbation at pilot sites, of such types of structures was confirmed as early as the 1970s. However, the widespread dissemination is constrained by the complexity and uncertainty of the calculated dependences. The development of analytical and empirical resistance models is considerably complicated because of the stage process of deformation and the change in the compartment operation scheme. Due to the development of a more universal approach for determining the bearing capacity based on numerical models, in which conservatism of the results is practically eliminated, the format of checking the safety of elements with pronounced nonlinear behavior becomes critical. To verify the safety of rafter structures, as a rule, the method of limit states in the formulation of the method of reliability factors is used. However, the methods for determining and calibrating reliability coefficient values are focused and most developed for linear models.
 
 Materials and methods. The paper presents proposals on the development of the method of reliability factors on the basis of analytical dependence with justification of required quantile for calculated values of load-carrying capacity on the basis of first-order reliability theory methods with subsequent verification by means of simulation methods.
 
 Results. The paper presents probabilistic models of the bearing capacity of a beam with a flexible web and substantiates probabilistic models of basic variables. The values of reliability factors for calculating the calculated values of bearing capa-city have been obtained.
 
 Conclusions. The analytical dependence for determining design values for the regulated level of reliability has been substantiated. Numerical values of coefficients of variation of bearing capacity for beams with flexible wall for different kinds of failure have been obtained.