Longitudinal-transverse bending of physically nonlinear reinforced concrete beams

В работе рассматриваются экспериментальные диаграммы деформирования бетонов марок B10, B30, B50. Методом наименьших квадратов приведены аппроксимации диаграмм деформирования полиномами второго и третьего порядка. Указанные расчеты выполнены как для случая одинаковых коэффициентов для зон растяжения и сжатия, так и различных. Приведен алгоритм решения задачи продольно-поперечного изгиба балки в случае использованных данных аппроксимаций диаграмм. The paper considers experimental deformation diagrams of concrete grades B10, B30, B50. The approximation of the deformation diagrams by polynomials of the second and third order is given by the least squares method. The calculations were performed both for the case of the same coefficients for the zones of tension and compression, and different ones. An algorithm for solving the problem of longitudinal-transverse bending of a beam in the case of the used data of approximations of diagrams is given.

NAVAL ARCHITECTURAL CONSIDERATIONS IN THE DESIGN OF FLOATING DOCK

A brief introduction about floating docks, its advantages and types have been described. The naval architectural considerations which play a significant role in the design of floating dock have been explained. Typical ratios of L/B and L/D as a function of Dock’s lifting capacity have been presented. Empirical formulation for the same have also been indicated wherever applicable. Intact stability and its criterion as applicable for a floating dock have been described. Critical positions during evolution of docking operation and important considerations while performing stability calculations have been highlighted. Attention has also been drawn to the damage stability of floating dock. Aspects of longitudinal and transverse bending moment, which are the governing aspects in the scantling calculations have been described. Also typical methods for securing and mooring of floating dock, without compromising on flexibility for docking operations have been described. Methodology and consideration which has to be kept in mind while using design software (such as NAPA) have been indicated. Simple size optimization techniques which result in steel / ballast volume reduction have also been explained.

Determination of changes in the mechanical properties of polymer composites with the addition of agglomerates of WC nanopowder

Recently, there has been a growing interest in the development of new composite materials with improved characteristics. The article presents the results of tests of composite specimens based on aramid fabrics modified with WC nanopowder agglomerates obtained from carbide manufacturing waste. The following mechanical characteristics were investigated: transverse bending resistance, fracture resistance and energy absorption during contact with a physical body at high speed. According to the results, the transverse bending resistance increased by 35% at a WC concentration of 5%. When 3% WC powder was added to the matrix composition, the total crack length after impact was almost halved. The largest increase in energy absorption of the samples was about 30% at 1% additive concentration. The significant increase in the investigated parameters can be explained by the complex morphology of the embedded particles. In further investigations it is planned to study in detail the mechanism of distribution of nanodispersed WC powder additive in the volume of the modified material.

Identification of Modal Parameters for Reinforcement of Walls in Earthen Ruins

The protection of earthen sites plays an important role in the context of preservation of cultural heritage, especially in the inheritance and promotion of history and culture. The aim of the paper is to present the essential results of an ongoing research on a reinforced rammed earthen wall in Suoyang City (Guazhou, China). The wall vibrations caused by ambient actions were analyzed using the stochastic subspace algorithm to estimate the modal parameters of the wall. The frequencies of the first three orders are 3.566 Hz, 5.003 Hz, and 6.250 Hz, and the corresponding modes are first-order transverse bending, second-order left and right torsion, and third-order vertical bending, respectively. Then, according to the data of elastic modulus obtained in the lab, the finite element calculation is carried out, and referring to the results of field measurement, the revised elastic modulus value is 205.90 MPa. It is worth mentioning that the revised value is significantly improved from the original laboratory value, and it is also indicated that the seismic performance of the reinforced wall has been significantly improved. The present work is expected to provide a theoretical basis for reinforcement, protection, and seismic control of earthen ruins.

Method of Experimental Research of New Construction of Beams from Glued Wood with Combined Reinforcement

Structures of glued wood have significant advantages in comparison with structures made of metal or reinforced concrete (less mass, better resistance to the action of chemically aggressive environments, high fire resistance, aesthetic attractiveness, eco-friendliness). However, at the same time, scientists are looking for new ways to improve the characteristics of such wood. We also proposed a new construction of combined reinforcement of glued beams in which the steel bar reinforcement of the periodic profile was arranged in the grooves of the compressed zone, and in the stretched zone reinforcement was carried out with the external composite tape made of carbon fiber. This combination increases both rigidity and bearing capacity of the elements that we are testing from glued wood for work on transverse bending. The method of experimental research on the transverse bend of a new construction of glued beam beams with combined reinforcement was developed. The proposed method fully allows us to examine and experimentally investigate the stress-strain state under load of glued beams from combined reinforcement at different stages of their work.

Longitudinal-transverse bending of multilayer concrete rods reinforced with steel reinforcement under the influence of mass forces

В работе рассматриваются многослойные бетонные стержни постоянного поперечного сечения армированные стальной арматурой. Предполагается, что в стержне имеет место одноосное напряженное состояние. На примере армирования сталями марок А240, А400, А800 показано влияние степени армирования на несущую способность стержня. Рассматриваются случаи армирования как только одного из слоев стержня, так и армирование всех слоев одновременно. The paper deals with multilayer concrete rods of constant cross-section reinforced with steel reinforcement. It is assumed that there is a uniaxial stress state in the bar. Using the example of reinforcement with steels of grades A240, A400, A800, the influence of the degree of reinforcement on the bearing capacity of the bar is shown. Cases of reinforcement of both only one of the layers of the bar and reinforcement of all layers at the same time are considered

Research on Nonlinear Deformation and Stability of an Aircraft Fuselage Composite Section under Transverse Bending

Currently, there is a lack of studies on the strength and stability of reinforced composite shells, taking into account the momentness and nonlinearity of the initial stress-strain state. Most of the known solutions to the shells stability problems are obtained by analytical and numerical methods, as a rule, in the linear approximation, i.e. in the classical formulation. A developed technique is proposed implementing the finite element method for solving the problems of strength and stability of discrete-reinforced cylindrical shells made of the composite material, taking into account the momentness and nonlinearity of their subcritical stress-strain state. The transverse bending stability of the reinforced aircraft fuselage compartment made of composite material has been investigated. The effect of deformation nonlinearity, stiffness of stringer set, shell thickness on critical loads of the shell instability has been determined.

FEATURES OF MECHANICAL TESTS OF OSTEOSYNTHESIS SYSTEMS

Various methods of measuring the characteristics of stiffness and strength of systems "bone with a fracture - a means of fixation" are considered. Methods for measuring deformations of osteosynthesis systems are systematized, which take into account the nature of the action of external loads and allow to compare different systems of osteosynthesis. The rational arrangement of drugs at tests taking into account features of a structure of bones and the real loadings arising at functioning of musculoskeletal system is recommended. It is proposed to use the stiffness characteristics of the systems "bone - means of fixation" under the action of axial compression, transverse bending and torsion, including in cyclic modes; considered systems of osteosynthesis with the most common methods of fixing fractures to select the optimal in terms of quality methods of fixing fragments in fractures. It is established that the stability indicators of osteosynthesis systems, measured in the process of cyclic tests, are more sensitive to the type of fixing means and can be used to rank these systems according to the degree of mechanical reliability. The results of research obtained using these methods are implemented in surgical practice in the selection of optimal designs of fixation devices and the rational location of fixing elements.

Influence of the chemical composition of the matrix on the structure and properties of monolithic SHS composites

Introduction. The development of new wear-resistant materials obtained by the method of self-propagating high-temperature synthesis (SHS) is an urgent problem in materials science. The SHS method is most widely used in the field of creating new powder materials. Much less attention has been paid to the production of monolithic non-porous composites. For monolithic composites, it is very important to identify the role of the metal matrix and phase transformations in the process of secondary structure formation after the completion of the synthesis process when the obtained material is cooled. The aim of this work was to carry out a comparative analysis of the structure and properties of SHS composites of the Fe-Ti-C-B, Fe-Ni-Ti-C-B, Fe-Ni-Cr-Ti-C-B, and Cu-TiC-B systems. Materials and research methods. Composites were obtained from powder mixtures consisting of thermoreactive components Ti, C, and B, as well as matrix Fe, Fe-Ni, Fe-Ni-Cr, and Cu. The initial powders were thoroughly mixed, loaded into a steel tube container, and the powder mixture was preliminary compacted. Then, the workpieces were heated in an electric furnace to the temperature of the onset of autoignition. After completion of the SHS, the workpieces were deformed with a force of 250 MPa in a hydraulic press at a temperature not lower than 1000 ° C. Samples were cut from the obtained sandwich plates for microstructural studies, density determination, hardness measurements, transverse bending tests and abrasive wear resistance tests. Results and discussion. All investigated composites were characterized by an uneven distribution of strengthening particles TiC and TiB2 over the volume. The use of the Fe-Ni matrix led to the formation of regions with the γ-Fe + Fe2B eutectic structure in the composite and an additional strengthening phase Ni3Ti. The use of Fe-Ni-Cr metal-matrix components led to the formation of two solid solutions in the matrix - austenite and ferrite, and Cr23C6 particles were formed along the boundaries of austenite grains. The maximum transverse bending strength was shown by SHS composites of the Fe-Ti-C-B and Cu-Ti-C-B systems with a matrix of FCC solid solutions. All composites had a hardness of 66 -72 HRC and showed the same abrasion resistance.