Object of research is build-up compressed–bent and eccentrically compressed columns on yielding nonlinear – deformable shear bracings. Purpose of the research is development of a numerical method for calculation of columns, allowing to take in account the influence of deflection of elastic axis of bar on the increment of the bending moment from the action of longitudinal compressive force and the nonlinear dependence between the forces and deformations in the shear bracings. Problem-solving method consists in dividing the column into separate sections, a system of equations is compiled from the condition of equality of the increment of concentrated shears. The loading process is divided into a set number of stages, at each forces in the shear bracings, the stresses in the branches, and the buckling function of the elastic axis of the element are determined. The obtained values of forces in the shear bracings and buckling are used to specify stiffness of the bracings and component of the bending moment arising due to eccentric application of the longitudinal compressive force when longitudinal axis of the element is deflecting. To obtain the resulting values, the obtained forces, deflections and stresses in the branches at each calculation stage are summed up.
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.
1 Северный (Арктический) Федеральный Университет им. М.В. Ломоносова, г. Архангельск, Россия 2 Поволжский государственный технологический университет», г. Йошкар−Ола, Россия Аннотация. Древесина находит все большее применение в жилищном строительстве в России и мировой практике. Особый интерес представляет модульное домостроение, при котором большая часть работ по изготовлению конструкций, отделке, инженерного оборудования выполняется на заводе−изготовителе. В основном высота таких зданий ограничивается 2…3 этажами, реже − до 5 этажей. Однако зарубежный опыт показывает, что этажность таких домов может быть повышена до 7−ми этажей. Конструкции на деревянном каркасе могут соответствовать 3−й степени огнестойкости и классу пожарной опасности С0. В России при этих показателях допускается строить здания высотой до 5−ти этажей с разделением их на пожарные отсеки. Определяющим фактором этажности таких домов является прочность и устойчивость основных несущих элементов деревянного каркаса. Как показывают исследования, добиться значительного увеличения прочности и устойчивости деревянных стоек каркаса можно включением в работу обшивок, в том числе за счет применения сдвигоустойчивых механических связей. В работе приводится методика и результаты исследования критической силы для деревянных ребер, работающих в составе стеновых панелей или объемных модулей совместно с обшивками. Для реализации поставленной задачи используется теория составных стержей А.Р. Ржаницына. Ключевые слова: модульное домостроение, деревянный каркас, механические соединения, прочность, устойчивость, жесткость, податливость.Abstracts. Employment of wood in housing construction constantly increases. Special interes is observed in modulus housing, in which the most part of construction production, finishing and engineering equipment is performed on factory. Basically, the height of such buildings is limited to 2...3 floors, but sometimes can be up to 5 floors. Foreign experience showes that the number of storeys of such houses can be increased to 7 floors. Structures on a wooden frame can be corresponded to the third degree of fire resistance and C0 fire class. These indicators allowes to build buildings up to 5 floors in height in Russia with their division into fire compartments. The determining factor of number of floors in frame houses is strength and stability of main bearing elements of wooden frame. Significant increase of strength and stability of the wooden racks of the frame achieving with including claddings by shear-resistant mechanical connectors using is shows in studies. The article presents the methodology and results of the study of the critical force for wood ribs, working with claddings in wall panels or bulk modules. To accomplish the task, the composite rods theory of A.R. Rzhanitsyn is used.
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