The developed method for assessing fi re resistance relates to the fi eld of fi re safety of buildings and structures and can be used to classify a reinforced concrete column of circular cross-section according to fi re resistance indicators. The essence of the proposed solution is to assess the design limit of fi re resistance of a reinforced concrete column of circular cross-section for the loss of bearing capacity under fi re conditions according to a set of single quality indicators without direct testing. The description of the process of resistance of a reinforced concrete column to fi re impact is presented by a mathematical relationship that takes into account the dimensions of the cross-section of the column, the degree of reinforcement, the intensity of force stresses, the normative strength of concrete to the resistance to axial compression and the rate of thermal diff usion of concrete. To determine the fi re resistance limit of a reinforced concrete column with a circular cross-section, an analytical expression that combines all the described indicators is proposed. The proposed method for determining fi re resistance refers to a thermal strength problem, which makes it possible to determine the fi re resistance of a reinforced concrete column of circular cross-section without full-scale fi re exposure, and reduces economic costs.
The infl uence of transverse reinforcement, including indirect reinforcement, on the strength of compressed reinforced concrete elements is analyzed. This question arose in connection with the possibility of increasing the strength of short reinforced concrete elements loaded with a longitudinal force with small eccentricities within the section of the element. For such elements, the cage eff ect may appear, associated with the coeffi cient of transverse deformations, the magnitude of which is a direct factor in the destruction of the concrete sample, and the limitation of these directly aff ects the bearing capacity of the sample in the direction of increase. The infl uence of transverse reinforcement in the form of stirrups located with diff erent spacing, as well as indirect reinforcement in the form of meshes with a classical rectangular cell and meshes of the “zigzag” type is considered.
The article presents a brief overview of the life path of the Swiss mathematician and mechanic Leonard Euler, considers the history of the emergence of the formula for calculating stability, shows options for taking into account the fl exibility of an element in the calculations of reinforced concrete structures, the disadvantages of the Euler curve and the features of its application in relation to structures made of high-strength concrete and concrete hardening under pressure. An example of the result of using a non-linear deformation model in the calculations of eccentrically compressed reinforced concrete elements with the introduction into the algorithm for calculating a coeffi cient that takes into account the eff ect of buckling (defl ection) of an element on its bearing capacity is given.
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