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Cross laminated timber panels (CLT) are promising building structures that are actively used in the construction of buildings around the world. In Russia the construction is rarely used, despite the existing factories for their manufacturing. In regulatory documents there are no specific data on the elastic modulus for these structures. As a method for determining this calculated characteristic, a numerical experiment in the SCAD Office software package is proposed. During the experiment, panels of various thickness and different numbers of layers are considered. Based on the obtained displacements from the action of the applied load, the values of the elastic modules are determined and summarized in the table. According to the results of the calculation, graphs of dependences of the reduced elastic modules on the thicknesses and the number of layers are constructed and analyzed.

The results of a bending test of wood composite beams connected by gang nail are presented in this paper. Two types of wood composite beams fracture were observed: brittle and ductile. In addition, a numerical model of wood composite beams was produced and the results of the numerical investigations were analyzed. Compliance of connection ..gang nail - wood... was considered by means of input elements with a reduced modulus of elasticity in the numerical model. Then the theoretical and experimental results of stress and strain state of a composite beam with gang nail were compared. The conclusion was made about the efficiency of gang nail application for increased shear resistance of wood composite structures not only for reinforcement but also for production of new beam structures. (ProQuest: ... denotes formulae/symbols omitted.)

Reinforced wooden beam structures under the influence of critical loads are subject to brittle fracture, which is dangerous when operating beams in buildings. To solve this problem, reinforcement of wooden beams for civil and industrial buildings was invented using steel rope as a reinforcing element. The rope is located in the stretched area of the beams along the original S-shaped trajectory. Numerical studies of the deformation of the reinforcement model using the LIRA program are performed. Based on numerical studies, samples were made for testing for pulling S-shaped anchoring elements from solid wood. The analysis of deformation - strength characteristics based on the results of tests on a tensile testing machine glued curved rods. A triple increase in the ductility of the deformation of the paste in the zone of destructive loads was revealed. The main problems of this type of reinforcement are the appearance of stress concentrators in areas with a small radius of curvature of the reinforcement. As a result of the study, the optimal trajectory of the reinforcement insert was determined with the aim of obtaining higher strength and deformation characteristics - with a reduced oscillation amplitude. The possibility of using structures in the form of safety elements has been established, which allows to increase the destruction time of beam systems when exceeding the permissible load.

Wood composite plate-ribbed structures working under the conditions of lateral bending in coverings and floors in buildings of various purposes are considered. The results of studies of the influence of various parameters on the stability of the upper compressed sheathing of wood composite panels with bonded joints of sheathings and ribs (type of connections, coefficient of stiffness of the bonded joints, span size, width of panels and material of anisotropic sheathing) are presented. To implement the task, the Lekhnitsky theory of calculating the stability of anisotropic plates is used, in particular, the energy method for determining the critical force for a flat anisotropic plate loaded along the edges by tangential efforts. For describing the distribution function of tangential efforts on the edges of the sheathings, the Rzhanitsyn theory of calculating composite rods is applied. As a result of numerical studies, the coefficients of longitudinal bending, which can be used in the engineering calculation of wood composite panels with mechanical and glued joints are obtained.

Wood-composite plate-ribbed bend structures with plywood and oriented strand board as covers with splices are considered. An overview of studies devoted to the study and increasing of the efficiency of such structures is presented. The theory of calculation of composite rods by A R Rzhanitsyn is taken for compilind a mathematical model for calculations of the the stress-strain state of these structures, taking into account the splices in the cover and the flexibility of mechanical joints of the covers and ribs. The graphs of the dependence of the maximum tensile stresses in the ribs in the criterion cross section and the maximum vertical displacements from the shear bond stiffness coefficient and the location of the splices in the cover are presented. The values of the coefficients for the engineering calculation of plates, taking into account the decrease in the strength and deformation characteristics of the composite section of panels with splices in the cover, compared to panels without splices in the cover, are proposed. Conclusions and recommendations are formulated based on the results of the research, which can be used in the design of wood-composite plate-ribbed structures.

Wood as a material with sharply expressed anisotropic properties fully transfers them to glued wood. Depending on the force vector under tension along, across and at an angle to the fibers, it differ tenfold. The results of studies of laminated wood tensile at different angles to the orientation of the fibers are given. The results of calculations are determined with testing of standard samples fordesign strength according to the method of ALTI-CNIISK. It is established that the angle between fiber orientation and vector of the applied force αis influenced a lot bythe tensile strength and depends on the sort of wood. The value of tensile strength is decreased when the angle vary from 0 to 90°. Experimental values are compared with theoretical results which are given in current standards -Rules and Norms 64.13330.2017 \"Wooden structures\". The difference between theoretical and standard results is 4 ... 70%. More accurate approximating expressions of experiments are presented, which can be used in practice instead of formula (6) from Rules and Norms.

Wood as a structural material differs from other materials used in construction and industry, high variability of its properties. This is due, among other things, to the action of various variable factors - moisture content, temperature, inclination of fibers and others. The influence of wood moisture is especially strong - as a result of moistening the strength of wood considerably decreases in comparison with durability in absolutely dry condition. In addition, wood is a significantly nonlinear structural material. Non-linearity is manifested both in short-term and prolonged loading. Research of wood in time can be divided into two directions: longterm durability of wood and creep of wood. Modern models of wood creep are based on linear theories. Analysis of experimental data of various researchers on wood creep, has shown that the area of linear creep is observed at rather low levels of loading. At medium and high levels of experimental loading the existing models of linear wood creep theory do not correspond to experimental data. All this points to the actuality of the development of methods of calculating wooden structures for creep (linear and nonlinear), taking into account the wood moisture.

Modern structural analysis standards for wooden and glued laminated building structures of civil and industrial buildings, bridges, electric power facilities, communications, etc., on the one hand, have differences, and on the other hand, general design principles (SP). However, the design resistances values are given only for the force vector acting along and across the fibers. The designer has to get the intermediate design resistances values according to the formulas of the 30s, very approximately, and sometimes incorrectly. For example, for cross laminated timber (CLT). Based on previously performed experimental researches and the results of calculations, general patterns of the resistance to local crushing changes were obtained for samples taken from glued laminated timber structures elements (glulam). General approaches have been developed to assess the strength of glulam (σcr,a) and its design resistances to local crushing (Rcr,a) with varying static geometrical parameters of the hard stamp (ψ = d/l) depending on the external forces vector direction with respect to the wood fibers - lamellas (α). All this makes the research present-day and focused on improving reference documents.

The results of a study of the shear stability of single-slice joints on screws of wooden ribs and wood-composite covers of structural plywood (SP) and oriented-strend boards (OSB) are presented. The plastic behavior of the destructure of the joint is established, the coefficient of safety during plastic fracture is determined, the bearing capacity and stiffness coefficient are calculated. A plan for a 2-factor experiment with varying factors at 3 levels has been compiled, regression equations have been obtained that made it possible to calculate the stiffness coefficient of screw joints as a function of the diameter of the screw and its embedment in the rib, and response graphshave beendrawn. The scientific conclusions and recommendations based on the performed experimental studies are formulated. It can be used in design of plate-ribbed structures of floors and walls with covers from wood-composite materials.

Currently, various composite structures made of wood, steel and concrete are used in construction. Some studies are aimed at developing the direction of wood-concrete slab-ribbed structures. Analyzing the methods of joining wood-concrete structures, it was found that the stiffness at the \"edge-slab\" border has a significant effect on the stress-strain state of the whole structure, and rigid joints allow using the positive properties of concrete and wood materials more rationally, taking into account structural, rheological and physical properties. To increase the shear resistance at the border of joining, a new combined joint based on the unilateral gear plate \"Bulldog\" and a screw nog is proposed. A numerical model has been made to calculate the joint deformation due to the action of a single shear force, which is based on the law of deformation of linearly elastic materials and the Winkler model. It describes the deformation of a nog lying on an elastically deformable base. Empirical formulae were used to take into account the nonlinearity of deformations during the long-term impact of force on the joint in conjunction with the anisotropy of wood. The dependence curves of the joint stiffness coefficient on the diameter of nog, gear plate and the restraint value of nog in the wood are constructed for dowel and combined joints. It was shown that reinforcement of the joints (up to 6-7 times) could be achieved by increasing the diameter of the nog, and combined compounds based on a gear plate allows to increase this indicator by 2...4 times. The use of screws is recommended as cross-links, the presence of concrete in the head and thread in the wood will reduce the negative effect of warping of wood during shrinkage on the operation of the proposed compounds.