This article presents the results of experimental research on the non-stationary management of the internal climate of buildings with a non-constant stay of people. During the absence of people, a significant drop in air temperature and corresponding energy conservation in heating is possible. The effectiveness of porous building materials is shown, provided that the appropriate characteristics are selected. Daily fluctuations in the outside temperature are completely extinguished by a layer of foam polystyrene insulation. The absence of channel porosity in the structural material of the wall is a guarantee of the stability of its thermal and humidity regime. This, in turn, prevents the development of mold and mildew.
The article describes the use of two-parameter distributions for assessing the residual resource of engineering systems and building structures of buildings and structures. To estimate the residual resource, the authors propose using the Weibull distribution, beta distribution, gamma distribution, and student distribution. Scopes of each distribution are shown. In particular cases, these distributions turn into normal or exponential distributions, which are widely used to estimate the residual resource of building structures and engineering systems of buildings and structures. The authors proposed an algorithm for using two-parameter distributions for a joint assessment of the residual resource of building structures and engineering systems of buildings and structures. In this algorithm, the authors present the parameters by which it is necessary to choose one or another two-parametric distribution. Further, the authors determined how to estimate the element failure rate in the presence and absence of data on the number of failures. The authors also proposed a procedure for assigning the final value of the residual resource when using several distributions at once. The advantages and disadvantages of using two-parameter distributions for a joint assessment of the residual resource of building structures and engineering systems of buildings and structures are given. The authors also proposed ways to further improve it.
Test methods for reinforcing steel is not suitable for fiber reinforced polymer (FRP) rebars because it can cause destruction of the edge zones of the samples. The polymer matrix and fibers are not able to resist compression across the fibers. Existing test methods for FRP rebars do not contain information about the equipment and composition of the adhesive composition. The purpose of the study is to clarify the adhesive composition and design of the FRP specimen anchor. Methods. There were experimental studies of fiberglass reinforcement polymer rebars samples carried out. The following factors varied: the proportion of the components of the adhesive composition; the area of the adhesive contact of the FRP specimen anchor. Results and Discussion. The proportion of epoxy glue and quartz sand providing the test of automatic transmission is determined. The influence of the thread on the inner surface of the FRP specimen anchor on the adhesive strength in the contact zone «adhesive composition-steel» is estimated. A universal three-dimensional model of the centering plug for manufacturing using additive technologies has been developed. Conclusions. The results of the investigation can be used to upgrade the FRP rebars test methods.
Introduction: Based on an analysis of issues related to the anchorage and active adhesion between deformed reinforcement and concrete, it is possible to identify major problems of concrete-to-steel bond breaking during the operation of bearing building structures. Purpose of the study: The authors seek to determine the mechanism of interaction between concrete and steel in the adhesion contact area, establish a relationship between external force action and crack development in the contact area. Methods: The authors suggest some dependencies to evaluate various test methods when determining the area where two materials, differing in physical characteristics, interact. Approximation to the actual phenomena related to the interaction between concrete and reinforcement, starting from the moment when through and non-through internal cracks form in the contact area and ending with destruction, is a general problem of models describing the adhesion of materials. Results: The theoretical results were compared with the experimental data and recommendations of modern regulatory documents, and it was found that they are in a satisfactory agreement. It was established that the difference of axial deformations of the bar and the surrounding concrete goes into the difference of bending displacements, which explains uneven load distribution across the protrusions. Discussion: Using the suggested dependencies, it is possible to predict crack development in the contact area of the reinforcement and cement binder as well as in the slip area in an extreme case. The concrete tensile strength in particular reinforcedconcrete elements in supporting cross-sections and with anchorage in tensile concrete represents a factor affecting the strength of the concrete-to-steel bond.
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