RASPOPOV I. Strength and rigidity of nodal connections with glued-in steel rods in the laminated veneer lumber elements

The dissertation is devoted to solving the scientific problem of assessing the strength and deformability of the developed nodal connection on glued rods in veneer or LVL elements under axial loading of the rods. The introduction substantiates the relevance of the work, its novelty and indicates the importance of issues requiring detailed consideration, the practical value of the work and presents its general characteristics. In Capter 1 provides a review of the literature on the state of the art in the use of LVL in modern construction, as a high-tech material based on veneer with strength indicators exceeding the strength of glued laminated timber and solid wood. The analysis of existing methods for calculating joints with glued-in rods was also carried out in accordance with the regulatory documents of various countries. In Capter 2 analyzes the prerequisites for considering LVL as an orthotropic wood-based material with a structure similar to plywood and other wood plastics. Approaches are considered that allow assessing the strength and deformability of LVL based on an elementary layer based on technological prerequisites, where a veneer layer impregnated with glue, taking into account the technology of its peeling, is considered as a structural unit of material with a different number of layers. Analytical methods for taking into account plastic deformations of the adhesive layer in joints on glued-in rods, where the thickness of the adhesive layer reaches 3 mm, are also presented. In Capter 3 presents the results of complex laboratory tests of single and double glued-in rods in elements of LVL bar under axial pull-out loading, and also presents the results of the strength of LVL bar under compression at various angles and tests of three types of specimens for chipping, since the mechanism of destruction of glued rods is realized by chipping the wood around the glued-in rod. Actual strength values of LVL with unidirectional veneer and its elastic characteristics were determined for use in a computational model using volumetric finite elements. In Capter 4 presents an analytical analysis of the strength and deformability of a LVL beam with a node in the form of a metal insert on glued-in steel rods is carried out in the ANSYS computational software package by modeling the studied node with volumetric finite elements. The elastic characteristics of the LVL bar were used, obtained in experimental studies, taking into account the results of the work of others. The deformability values and the nature of the stress distribution, as well as the effect of the nut tension on the nodal joint compliance were obtained. In Capter 5 proposes a method for determining the pull-out strength of gluedin rods under axial loading, installed along the grains in LVL elements with unidirectional veneer orientation. Rules for the design of nodal connections have been developed, indicating the minimum distances between the rods and from the rod to the faces of the cross-section. Methods of helical transverse reinforcement of joints on glued-in rods are proposed.