Engineering assessment method of reliability indexes of steel trusses bars
Journal Title: Вісник Одеської державної академії будівництва та архітектури - Year 2017, Vol 1, Issue 66
Abstract
The simplest methods of evaluating reliability indicators of building structures elements based on the representation of the strength characteristics and stress in the form of random variables do not take into account the lifetime of the structure. Submission of variable loads in the form of quasi-stationary random processes with actual distributions ordinates requires a fairly complex computational procedures. The offered method of evaluating probabilities of failure of steel roof trusses rods is based on the representation of the characteristics of strength of the material and constant load in the form of normally distributed random variables and snow load ‒ in the form of a sequence of annual maximums described by Gumbel distribution law. Such approach allows for a fairly simple formula to estimate reliability indexes considering design service life by switching from annual heights of the distribution of variable load to the maximum allocation for the entire service life. The developed method is illustrated by an example of calculation of steel roof trusses rods in various combinations of permanent and snow load. The farms with parallel chords span of 24 meters are examined. Dependences of the level of reliability of rods in Bell (logarithm of the probability of failure with the sign «minus») on the level and structure of bars loads are analyzed. The level of reliability decreases with increasing utilization of the bearing capacity of rods and with the growth of variation coefficient of the reserve of load capacity. Despite the simplicity, the developed method can adequately take into account the characteristics of loads, design features and service life in the assessment of the reliability of farms rods.
Authors and Affiliations
Victor Pashinsky
Keywords
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