Аnalysis of methods of calculating road structures based by shear resistance in the soil

Introduction. Checking the soil of the subgrade and the layers of road pavement made of loosely cohesive materials by shear resistance is one of the three mandatory conditions for calculating road clothing according to strength criteria. The methodology for checking the soil of the subgrade and the sandy layers of the road pavement is constantly being modified, which is why changes concerning certain calculation details appear in each new version of the regulatory document. The purpose of this work is to analyze the advantages of the classical solution of A.M. Krivissky and to reveal the essence of the errors made in subsequent modifications of this calculation.Materials and methods. The analysis of solutions is carried out from the standpoint of compliance with the basics of mechanics. It is shown that the calculation of the total shear stress in the classical solution of A.M. Krivissky is performed in accordance with the principle of force superposition, which consists in calculating the components of the stress tensor from each force (time load and the own weight of the layer materials) separately, followed by summing the corresponding components. In this case, the active shear stresses from the temporary load and the own weight of the materials are calculated as the equivalent stress of the Mohr-Coulomb criterion. The calculation of these two components of the total shear stress is performed at the same value of the internal friction angle. Since the angle of inclination of the sliding surface to the main axes is determined by the sum or difference of 45 degrees and half of the internal friction angle, the tangential and normal stresses, which are components of the active shear stress, both from the temporary load and the own weight of the materials, are determined for the same shear surface rotated to the main axes at the same angle. In the current normative calculations, the active shear stresses from the temporary load and the own weight of the materials are determined at different angles of internal friction. This means that the active shear stresses from the temporary load and the own weight of the materials act on two different shear surface rotated to the main axes at different angles. Such stresses cannot be summed up or compared with each other. In addition to this error of the normative calculation methods, their other disadvantages are given.Results. As a result of a detailed analysis of the known modifications of the classical solution, obvious contradictions to the principles of continuum mechanics are established. As an alternative to modern calculation criteria for shear resistance, the article presents criteria for soil strength in which the shear stress exceeds the equivalent stress in the Mohr-Coulomb criterion. The principle of deducing formulas for calculating the first critical load and the total shear stress from the strength criteria under consideration is shown.Conclusion. Conclusions are drawn about the need to return to the classical solution obtained by specialists of the Leningrad School of the USSR, or to develop a fundamentally new solution based on a new plasticity condition in which the total shear stress exceeds the similar characteristic of the stress state of the original Mohr - Coulomb criterion.

Brachial and carotid hemodynamic response to hot water immersion in men and women

This study sought to compare the brachial and carotid hemodynamic response to hot water immersion (HWI) between healthy young men and women. Ten women (W) and 11 men (M) (24±4 y) completed a 60 min HWI session immersed to the level of the sternum in 40°C water. Brachial and carotid artery hemodynamics (Doppler ultrasound) were measured at baseline (seated rest) and every 15 min throughout HWI. Within the brachial artery, total shear rate was elevated to a greater extent in women (+479 [+364, +594] sec-1 than men (+292 [+222, +361] sec-1) during HWI (P = 0.005). As shear rate is inversely proportional to blood vessel diameter and directly proportional to blood flow velocity, the sex difference in brachial shear response to HWI was the result of a smaller brachial diameter among women at baseline (P < 0.0001) and throughout HWI (main effect of sex: P < 0.0001) and a greater increase in brachial velocity seen in women (+48 [+36, +61] cm/sec) compared to men (+35 [+27, +43] cm/sec) with HWI (P = 0.047) which allowed for a similar increase in brachial blood flow between sexes (M: +369 [+287, +451] mL/min, W: +364 [+243, +486] mL/min, P = 0.943). In contrast, no differences were seen between sexes in carotid total shear rate, flow, velocity, or diameter at baseline or throughout HWI. These data indicate the presence of an artery-specific sex difference in the hemodynamic response to a single bout of HWI.

Highly localized upper mantle deformation during plate boundary initiation near the Alpine fault, New Zealand

Peridotite xenoliths entrained in magmas near the Alpine fault (New Zealand) provide the first direct evidence of deformation associated with the propagation of the Australian-Pacific plate boundary through the region at ca. 25–20 Ma. Two of 11 sampled xenolith localities contain fine-grained (40–150 mm) rocks, indicating that deformation in the upper mantle was focused in highly sheared zones. To constrain the nature and conditions of deformation, we combine a flow law with a model linking recrystallized fraction to strain. Temperatures calculated from this new approach (625–970 °C) indicate that the observed deformation occurred at depths of 25–50 km. Calculated shear strains were between 1 and 100, which, given known plate offset rates (10–20 mm/yr) and an estimated interval during which deformation likely occurred (&lt;1.8 m.y.), translate to a total shear zone width in the range 0.2–32 km. This narrow width and the position of mylonite-bearing localities amid mylonite-free sites suggest that early plate boundary deformation was distributed across at least ~60 km but localized in multiple fault strands. Such upper mantle deformation is best described by relatively rigid, plate-like domains separated by rapidly formed, narrow mylonite zones.

Tropical Cyclone Resistance to Strong Environmental Shear

It is widely known that strong vertical wind shear (exceeding 10 m s−1) often weakens tropical cyclones (TCs). However, in some circumstances, a TC is able to resist this strong shear and even restrengthen. To better understand this phenomenon, a series of idealized simulations are conducted, followed by a statistical investigation of 40 years of Northern Hemisphere TCs. In the idealized simulations, a TC is embedded within a time-varying point-downscaling framework, which is used to gradually increase the environmental vertical wind shear to 14 m s−1 and then hold it constant. This controlled framework also allows for the separation of the TC-induced flow from the prescribed environmental flow. The TC-induced outflow is found to withstand the strong upper-tropospheric environmental flow, and this is manifested in the TC-induced shear difference (TCSD) vector. The TCSD vector, together with the environmental shear vector, defines an azimuthal range within which most of the asymmetric convection is located. The statistical analysis confirms the findings from the idealized simulations, and the results are not strongly sensitive to the TC intensity or basin. Moreover, compared with total shear, the inclusion of TCSD information creates a slightly better correlation with TC intensity change. Overall, the TCSD vector serves as a diagnostic to explain the ability of a TC to resist strong environmental shear through its outflow, and it could potentially be used as a parameter to predict future intensity change.

Shear Resistance Contribution of Constituent Elements Consisting RCS Joint

In this study, constituent elements affecting the shear strength of RCS joints were investigated through experiment and analysis study. A series of five interior RCS beam-column joint specimens, which were classified as JH-type and CP-type, was tested to investigate the contribution of each shear resisting element such as JH (Joint Hoop), CP (Cover Plate), FBP (Face Bearing Plate), E-FBP (Extended Face Bearing Plate), TB (Transverse Beam), and BP (Band Plate). Comparison between experiment and analysis results showed that the stiffness and strength of the RCS joint were reasonably assessed from the analysis. As a result of the analysis, it was found that TB, E-FBP, and CP increased the shear strength by about 15%, 14%, and 26%, respectively. For the JH-type specimen, 70% of the shear strength of the RCS joint is supported by the inner element and 30% of the shear strength is supported by the outer element. Shear strength contribution ratio of the outer element of CP-type specimen is larger than that of the JH-type specimen. For all specimens except for SNI-1, around 10% of total shear strength is supported by FBP. The shear strength equation of the RCS joint proposed by ASCE underestimates the contribution of the outer element, while that of M-Kanno tends to overestimate it.

Calculation of seismic qualities of the damper and vibration transducer with the possibility of their use in aircraft

The aim of the work. The article aims to determine the most effective seismic protection devices, as well as their degree of reliability in different conditions. The method of comparative calculation for determining the quality of seismic protection devices is given. An example of calculation for the damper and vibration transducer is carried out. Calculations show that the use of seismic protection devices reduces the coefficient of K 3 more than twice. Seismic protection is an urgent problem not only in construction, but also in all branches of the technosphere. The option of using seismic protection devices in aircraft is also considered. Methods. A comparative calculation of the behavior of dampers and vibration transducer taking into account the friction coefficients f tr, the sum of vertical loads ∑ Qkd , the total shear seismic force ∑ Sdc is considered. The diagram of the location of seismic protection devices (damper and vibration transducer) under the building is presented, as well as the options for installation in aircraft are given. Comparative calculations are carried out with the presence of seismic protection installations and without them. Results. The total result is given taking into account the change in the value of horizontal seismic loads Sik , which has changed in the range of 2.26-2.46 times. This circumstance allows to conclude that the proposed damping device reduces the seismic load, which falls on the protected structure, by 1-2 points, with almost the same efficiency as the vibration transducers (difference of 0.3 times).

Comprehensive shear stress analysis of turbulent boundary layer profiles

Motivated by the need for accurate determination of wall shear stress from profile measurements in turbulent boundary layer flows, the total shear stress balance is analysed and reformulated using several well-established semi-empirical relations. The analysis highlights the significant effect that small pressure gradients can have on parameters deduced from data even in nominally zero pressure gradient boundary layers. Using the comprehensive shear stress balance together with the log-law equation, it is shown that friction velocity, roughness length and zero-plane displacement can be determined with only velocity and turbulent shear stress profile measurements at a single streamwise location for nominally zero pressure gradient turbulent boundary layers. Application of the proposed analysis to turbulent smooth- and rough-wall experimental data shows that the friction velocity is determined with accuracy comparable to force balances (approximately 1 %–4 %). Additionally, application to boundary layer data from previous studies provides clear evidence that the often cited discrepancy between directly measured friction velocities (e.g. using force balances) and those derived from traditional total shear stress methods is likely due to the small favourable pressure gradient imposed by a fixed cross-section facility. The proposed comprehensive shear stress analysis can account for these small pressure gradients and allows more accurate boundary layer wall shear stress or friction velocity determination using commonly available mean velocity and shear stress profile data from a single streamwise location.