With the increasing depletion of forest resources in buildings of normal and reduced class of responsibility for wooden structures belonging to the 2nd and 3rd classes of functional purpose, the possibility of using round timber and sawn timber from soft deciduous species such as aspen and poplar should be considered. since aspen ranks second in terms of area of growth among deciduous species and is found almost throughout the entire territory of the Russian Federation. An assessment of the properties of soft deciduous wood is carried out for use in building structures that perceive power effects. The data on the percentage of lignin and cellulose in coniferous and soft deciduous wood are given. The main physical and mechanical characteristics of soft deciduous wood, the calculated resistance of soft deciduous wood for the main types of stress state are presented. The results of a comparative calculation of interfloor structures made of coniferous and soft deciduous wood are presented. It is shown that the use of soft hardwood for building structures will contribute to the expansion of the range of wooden elements against the background of the development of expensive and labor-intensive in the manufacture of glued wooden structures.
Keywords: round timber, sawn timber, soft deciduous wood, physical and mechanical characteristics of wood, design resistance, flexural modulus
In the joints of wooden elements, obliquely screwed rods are installed in pre-drilled holes. In the absence of glue, the bearing capacity of the joint depends on the design resistance of the wood to chipping along the surface of contact with the thread of an obliquely screwed in rod. The purpose of this work is to assess the change in the bearing capacity and deformability of the joints of wooden elements on inclined screwed rods when glue is added. Samples of joints were tested on screwed-in rods, made with glue and without glue, three samples for each type of connection. It was found that the use of EPTs-1 glue increases the bearing capacity of joints on inclined screwed rods by the criterion of the breaking load by 1.33 times, by the criterion of the upper boundary of the elastic work area of the joint by 1.5 times, at the level of reaching the ultimate deformation Dult = 2 mm - 1.8 times. Full deformations Dp at the same load within the elastic work of the joints are reduced by more than 3 times. Compared to joints on glued-in rods made of periodic profile reinforcement, the consumption of glue is reduced by 6.8 times.
Keywords: connections on inclined screwed rods, glued in rods, wooden elements of composite cross-section, maximum bearing capacity, upper boundary of the elastic work area of joints, deformation of joints
The results of testing a series of 18 samples of joints for chipping along wood fibers are considered. The samples are made of glued wooden beam, intended for use as a supporting structure of the floor. To assess the strength of the adhesive joint in accordance with standard 33120-2014 “Wooden glued structures. Methods for determining the strength of joints”, statistical processing of test results was carried out, temporary shear resistance, coefficient of variation, range of variation series and the minimum probabilistic value of tensile strength were determined. Indicators are given to standard wood moisture content W = 12%. It was determined that the strength of the adhesive joint is less than the value established by current standards, by 18.5%.
Keywords: glued wood, wooden glued beams, adhesive strength, temporary chipping resistance, tensile strength, minimum probabilistic value of tensile strength, coefficient of variation, chipping during bending, standard wood wetness
The results of tests of a series of single-shear samples of joints of wooden elements on inclined metal rods (IMR), in which plain washers transmit the force between the rod and wood, are considered. The intended bearing capacity of the NMS-connection is determined by taking into account changes in SP 64.13330.2017. Theoretically and based on experimental data, the stress-strain state of an IMR connection and the stress state of inclined steel rods are considered. The prevailing factors in the stress state of inclined rods are established. The estimation of the bearing capacity of IMR-connections on the rods with plain washers performed.
Keywords: Wooden structures, ductile connectionions, NMS-connection, inclined metal rods, intended bearing capacity, shearing load, tensile stress, ultimate breaking load, bearing strain under washers, safety factor