Stress analysis and applicability analysis of the elliptical head

As the main pressure components of pressure vessels, the mechanical performance of cylinders and heads affects the normal operation of pressure vessels. At present, no unified theoretical formula exists for the connection region between an elliptical head and the cylinder. Therefore, the authors consider the standard elliptical head as the research object. First, the theoretical stress calculation formula is deduced according to the deformation continuity equation. Second, the stress is experimentally measured using an internal-pressure thin-walled-vessel stress measurement device, and the theoretical and experimental stress values in the discontinuous region between the elliptical head and cylinder are analysed and compared to verify the accuracy and applicability of the theoretical stress calculation formula. The results show that the theoretical stress calculation formula in the discontinuous region between the elliptical head and cylinder is valid. By comparing and analysing the theoretical and experimental stress values, the accuracy and applicability of the theoretical stress calculation formula in the discontinuous region are verified. The findings can provide guidance for the stress measurement of internal-pressure vessels.

Stress Analysis And Applicability Analysis of Elliptical Head

In view of the phenomenon that there is no uniform theoretical formula for the connection area between the elliptical head and the cylinder, the author takes the standard elliptical head as the research object. Firstly, the theoretical stress calculation formula of the elliptical head and the discontinuous area of the cylinder is derived according to the deformation continuity equation. Secondly, the experimental stress is measured by means of the internal pressure thin-walled vessel stress measuring apparatus, The theoretical stress and experimental stress in discontinuous region are analyzed and compared to verify the accuracy and applicability of the formula for calculating the theoretical stress of the elliptical head and the cylinder discontinuity region. The results show that the theoretical stress calculation formula of discontinuous region of elliptical head is obtained according to the equation of deformation continuity, edge force and edge moment, internal force and internal moment; The internal pressure load is kept unchanged, and for the theoretical longitudinal stress, the constant stress is greater than 0, which is the tensile stress, and decreases gradually from the vertex to the equator; For the theoretical circumferential stress, the change trend is more complex, which can be divided into three stages, and there is pressure stress. At the vertex, the magnitude of the meridional stress and the circumferential stress is approximately equal; The change of the change from point 8 to point 10 is affected by discontinuous stress, and the change trend is abrupt; The theoretical stress and experimental stress in discontinuous region of elliptical head are analyzed and compared, and the accuracy and applicability of the formula are verified. The results are of great significance for the stress measurement of internal pressure vessels.

Simulation Analysis and Experimental Study on the Working State of Sinking Headframe in the Large Underground Shaft

Based on the newly developed sinking headframe for the deep and large shaft, the finite element model of the full-scale headframe was established by using SAP2000. Through the calculation, the theoretical stress of the headframe at sinking depths of 40 m, 143 m, 223 m, 518 m, 762 m, 1000 m, 1250 m, and 1503 m was obtained and then compared with the field measured stress. The results show that with the increase of shaft sinking depth, the theoretical stress of finite element simulation and the field measured stress of each member of the sheave wheel platform and the headframe increase linearly, and for the maximum member stress in the upper, middle, and lower layers of the headframe, the numerical simulation value is greater than the field measured value and less than the designed steel strength. In other words, under normal working conditions, headframe members are in the elastic stress stage and meet the design requirements, and instability failure of headframe members will not occur. The end-restraint mode of the supporting bars has a great influence on the force of the top member. The reasonable selection of the restraint mode in the simulation is the key to the accuracy of the calculation results. The simulation results well reflect the actual stress of the headframe and provide a reliable guarantee for the follow-up work of the project.

Experimental and analytical evaluation of stress-strain behavior of basalt fibred concrete

The aim of this study is to determine the stress-strain behavior of basalt fibred concrete experimentally. Cylinders of standard size 150 x 300 mm are cast with with and without basalt fibres and tested in uni-axial compression under strain control as per IS: 516-1999 to understand the stress-strain behavior of basalt fibred concrete. After developing empirical equations for stress-strain curves of basalt fibred concrete, theoretical values of stresses are calculated at different values of strains in concrete based on the developed empirical equations as given above and theoretical stress-strain curves are plotted. These theoretical stress-strain curves are compared with experimental stress-strain curves and found that, theoretical stress-strain curves have shown good correlation with experimental stress-strain curves for all concrete mixes.

TRESSING FACTORS IN WORK AFFECTING THE EFFICIENCY OF WORK OF TAX INDUSTRY

The purpose of this study is the study of stress at work and work efficiency of the tax service officials. Based on the theoretical stress at work and qualitative research the author has identified four factors of stress at work are likely to have a relationship with the results of the work of public servants‟ tax service in the city HCM, including stress from customers (taxpayers), do the job in the role conflict, work overload, stress in relationships with colleagues and superiors Research methodology is performed in two steps - qualitative research and quantitative research. The study results also showed that when the stress is moderate, the result of work and overload of work are correlated in the same direction, but when the level of high stress work results and overloaded at work correlate counterclockwise.Finally, the author presents research implications for managers and the next research direction.

RESULTS OF EXPERIMENTAL RESEARCH OF THE REINFORCED CONCRETE SHELL-SLAB

Introducton. The paper demonstrates the results of experimental research of the reinforced concrete shell-slab under the action of vertical uniformly distributed load. The authors also present the comparison of such research results with the results of stress-strain state evaluation performed in the “Lira” software package.Materials and methods. The authors tested the reinforced concrete model representing physically similar copy with the 1:5 scale coefficients by general size, and by separate details. The load was applied in 10–15% doze of the theoretical bearing capacity of the plate.Results. The authors calculated the experimental transverse stress σх,3,exp, which was in full-scale construction and in the 3 central sphere. The authors also made the comparison of such transverse stress with theoretical transverse stresses σх,3,teor and the comparison was performed in the “Lira” program complex. The diagrams of the above stresses were well matched by outlines and values.Discussion and conclusions. As a result, the experimental (σx, 3,exp.) and theoretical (σx,3,theor.) stresses are compressive near the shell-slab center. Its maximum stress values (σx, 3, exp) reach x/b=0,5 at a point with a relative coordinate, and the stress (σx,3,theor.) – x/b ≈ 0,45.The zero voltage values σx,3,exp. reach a quarter of the shelf width, theoretical stress –with x/b ≈ 0,3 mm ratio.Maximum values of experimental and theoretical tensile stresses σx, 3 reach x/b ≈ 0,15 ratio. Therefore, the values are close to each other, and do not exceed the standard concrete tensile resistance Rbt, ser.The practical significance of the study is to obtain experimental evidence of the abandoning possibility of the horizontal transverse reinforcement of the shelf, which would reduce the complexity and cost of the investigated structures production.The prospects conclude in:research of the shell-slab operation at the stage of ultimate equilibrium;research of the shell-slab crack resistance and stiffness at all stages of its operation;research of the shell-slab operation taking into account the fixation in the transverse direction of its longitudinal contour edges along entire length.