The article is devoted to the study of the short-term and long-term deformations of the lightweight concrete which has found ever-growing use in various fields of construction. The main direction of the lightweight concrete usage is its application in the load-bearing and enclosing structures of buildings and structures. The lightweight concrete has fundamental differences from heavy weight concrete and this is primarily due to the special characteristics of the porous aggregates in their composition. Concretes with such aggregates as expanded clay, expanded perlite and agloportite with strength from 10 to 60 mPas, whose deformative properties are represented by the stress – strain diagram in fig.1, have been investigated in this work. The dependence of the diagrams completeness on the type of aggregate at various concrete strength indexes is given in Table 1. The ascending branches of the diagram for the whole range of the strength has ended when a deformation has reached 2,2·103. The concrete stress corresponding to the limiting compressive strain of all types of concrete has been 85% of the maximum value. All the diagrams intersect at one point, the descending branches diverge at a stress level of 0.75 and the deformations have been 2,9…3,7·103. The data obtained as a result of the investigation can be used to calculate the normal sections of bending and eccentrically compressed elements with allowance made to the properties of the lightweight concrete that significantly expand its promising applicable scope in areas with complex geological conditions and in seismic areas.
For the composite structures based on wood, that include reinforced wooden structures, allowance for the influence of wood specific features as a building material allows us to evaluate its structural design as accurately as possible and ensure the required reliability and durability. Creep that causes wood deformations evolving in time can be referred to the specific properties of wood to a greater extent affecting the operation of the reinforced wooden structures. Taking into account the state of the issue to determine the effect of the long-acting loads on the stress-strain state of the reinforced glued wooden structures, the article considers the application of the theory of elastic heredity as the most applicable to assess the deformability of wooden structures in time. The conducted experimental and theoretical investigations and the reinforced glued wooden structures observations during the operational process have shown that their stress-strain state changes significantly under the load over time. Glue compositions used to connect reinforcement with wood ensure their reliable joint operation, however, as the result of the wood creep where wood is the basic material, the redistribution of forces between the reinforcement and wood occurs there on and off. At the same time normal stresses in the reinforcement and the glue joint “reinforcement - wood” increase in the calculated cross sections while they decrease in the wood, which is caused by a change (decrease) in the wood elastic modulus. Allowance for the wood creep in the design of the reinforced wooden structures will allow to determine the stress - strain state of the structure in the design more precisely. Therefore, when developing the reinforced wooden structures design standards, this factor must be taken into account.
This paper proposes a method of restoration of wooden structures by impregnating polymer composition based on epoxy resin, locally weakened destruction. Objective - research and development of technology for site remediation of wooden structures with areas of locally de-graded wood. We analyzed the causes of the destruction of wooden building structures. The pa-per sets out the methodology and the engineering based on the example of a wooden beam, the destruction of locally weakened in the core zone. Engineering calculations were confirmed by numerical experiments carried out in the program complex "Lira 9.6".
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