DEVELOPMENT OF RANKING OF CRANE LOADS ON BUILDING STRUCTURES

Abstract

Ensuring the reliability and safety of buildings and structures largely depends on a proper understanding of the nature and quantitative description and rationing of loads on building structures, including crane loads. Loads from cranes can be significant; they have a variable dynamic nature and have a significant force on the structure of industrial buildings. These features are to some extent reflected in the sections of design codes of building structures that contain standards for crane load. Most of the parameters of the crane load codes are probabilistic nature and require the use of statistical methods to substantiate them. These methods are constantly changing and evolving together with the regular revision of building design codes. Analysis of the evolution of domestic codes of crane load together with their statistical substantiation is an urgent task, which is the purpose of this article. The beginning of domestic standardization of crane loads was laid in 1930, when the «Uniform codes of construction design» were introduced. They separately normalized vertical, horizontal longitudinal and horizontal transverse crane loads. This division is preserved in all subsequent versions of the load codes from bridge and overhead cranes. Since the late 1930s, leading construction research institutes and universities have conducted research on crane loads, the results of which have been consistently incorporated into design codes. These studies are time consuming and complex, as they are performed in existing production facilities and require the development of specific methods and equipment for measuring loads from operating bridge cranes. For 90 years, load codes have been constantly changing, taking into account the experience of operation and trends in construction science. The 50s of the last century were marked by the transition of structural calculations from the method of allowable stresses to the method of limit states, which led to a radical revision of the codes of crane loads. In the 60's and 80's, statistical studies of crane loads were intensified, the results of which opened up the possibility of reducing overload coefficients and introducing additional combination coefficients for crane loads. There were constant discussions about the assessment and consideration in the codes of horizontal transverse loads - braking and lateral forces from the skew of the moving cranes. This question still remains open for further research. It is also important to clarify the coefficients of load combination from several bridge cranes. With the collapse of the USSR, the new states had the opportunity to move away from the rough Soviet rationing and develop their own, more adequate codes for crane loads. Further development of crane codes in the CIS was realized in the form of national codes of individual states. Ukrainian specialists, in contrast to Russian standards developers, have prepared the State Standards of Ukraine DBN B.1.2: 2006 «Loads and impacts», conceptually different from SNiP in terms of crane loads. The publication of these codes was preceded by the systematization of the results of many years of work in the field of crane loads. Giving an overall assessment of Ukrainian standards of crane loads, it should be emphasized that they are compiled on a modern methodological basis, close to European standards Eurocode, based on representative statistics, more differentiated and have a scientific probabilistic rationale, more deeply developed than in codes of previous years.