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An engineering method of computation, which takes into account the development of zones of plastic deformation and corresponding nonlinearity of the settlement-load curve by the introduction of generalized coefficients, treated as deformation characteristics of the layer, and which make it possible to design foundations on the basis of preassigned settlements or their differences, is proposed.Proceeding from limitation and equalization of pressure beneath the lower surface, a method for the design of foundations, which is specified by modern Standards, will create premises for the development of nonuniform settlement [1], which is one of the reasons for failure of building superstructures.A method for the design of foundations, which limits the absolute settlements s i or relative differences in settlements Asi/L (calculation on the basis of deformations) with simultaneous confirmation of the bed's bearing capacity, is one of the alternative means 9 This method for the calculation of foundations on the basis of two limiting states is possible only in the case when the bed's performance is determined in both the linearly deformable, and elastoplastic stages.When a rigid foundation is loaded, regions of plastic deformations develop and spread virtually immediately in its bed. For an engineering solution to similar problems, it is expedient to use a certain function characterizing the properties of a certain volume (layer) of soil that changes with each externaMoad step.Changes in the shape and volume of the zones (regions) of plastic deformation as the bed is loaded are investigated in sufficient detail in works by Bugrov [2], Fadeev [3], and Pilyagin [4]. The stages of deformation of a plastic zone, which were obtained during an FEM calculation performed in accordance with the "Geotekhnika" program [3] for the case of the loading of a bed by a rigid plate, are shown, for example, in Fig. 1.The "V-P" curve ( Fig. 2) can be represented by the relationship V = V(P), which is constructed proceeding from the following assumptions.1. When the limiting pressure Plim is attained on a bed, the volume V also attains the limiting value Vii m (point M in the diagram) with allowance for the change of position of the zones of plastic deformations.2. Results of numerous calculations for foundation beds, which implement the solution of elastoplastic (mixed) problems, enable us to assume the "V-P" curve to be linear when Pi -< R (R is the computed strength of the soil, as determined in accordance with Construction Rule and Regulation 2.02.01-83), and convex in the direction of the P axis when Pi > R (point 2 in Fig. 2).If point E, which corresponds to the average pressure value in the interval AP i = Pi -Pi-1 is connected to point M, and the perpendicular is restored from the end of the interval or the point corresponding to Pi, its intersection with the designated trajectory defines the ordinate V i in first approximation. Connecting the successively defined vertices (Pi, Vi), we obtain the computed trajectory of the volume chang...

The implementation of projects for the construction of high-speed railways actualizes the search of effective approaches to accounting the influence of soil strata heterogeneity along the course of the track on differential foundation settlements of overpasses. Russian special technical conditions prescribe sufficiently stringent regulation limits of absolute values of overpasses' foundation soil settlements (20 mm for ballastless track) and angles of break in profile (the differential foundation soil settlement), which should not exceed 1 ‰ for ballastless track. These requirements make it necessary to develop the calculation method, which is based on the criterion of deformation. To ensure compliance of design solutions to the specified regulations it is appropriate to use the method of the predefined equated soil settlements for design of shallow foundations of overpasses for high-speed railways. Several features of application of this method are presented in this article.

The authors carried out a research of the stress - strain state of the hinge unit of light spatial grid framings of regular structure. The solid model of the hinge unit was created previously and numerical simulation was performed. Calculation identified, that the weak point of the hinge unit is connecting disk. Plastic deformation can arise in the disk during loading. The experimental research was required for verification of results of a pilot study. The test of disk was executed with application of a specially designed installation on universal tensile testing machine in the laboratory of the University. Mechanical characteristics of steel, from which the disk was made, were identified by a certified laboratory destructive control methods in accordance with the GOST. The experimental results are compared with the simulation results. The authors give recommendations for optimizing the design of the hinge unit.