Wooden-composite plate-ribbed bent panels with structural plywood and oriented strand board sheathing with breaks are considered. An overview of studies researching and improving the effectiveness of different types of panels is presented. On the basis of the theory of calculation of composite rods by A.R. Rzha- nitsyn, a mathematical model has been compiled, which makes it possible to calculate the stress-strain state of these structures, taking into account the pre- sence of breaks in the sheathing and the flexibility of the mechanical fasteners of the sheathing and ribs. An equation for finding the coordinates of the most dangerous section of wooden ribs in the presence of breaks in the sheathing, which may not match with the middle of the span, is obtained. Panels with sheathing in a compressed zone with different locations of joints, symmetrically relative to the middle of the panel span are considered. Panels without joints in the skin are considered to compare the results. The graphs of the dependence of the maximum tensile stresses in the ribs in the most dangerous section and the maximum vertical displacements from the stiffness coefficient of the shear ties and the location of the breaks in the sheathing are presented. The values of the coefficients for the engineering design of panels, taking into account the decrease in the strength and deformation characteristics of the composite section of panels with breaks in the sheathing, as compared to panels with a solid sheathing, are obtained. The conclusions and recommendations, based on the results of the investigations, which can be used in the design of wooden-composite plate-ribbed structures, are formulated.
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.
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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