Theoretical Study Into Efficiency of the Improved Longitudinal Profile of Frogs at Railroad Switches

We have developed a comprehensive method to prolong the time of operation of frogs at railroad switches, based on the consideration of a longitudinal profile of the frog, the magnitude of dynamic forces and normal stresses.We have improved a longitudinal profile of the frog, brand 1/11, project 1740, by the method of surfacing under field operation conditions. The slopes of a trajectory after the passage of an average statistical wheel over the proposed profile amount to 3.7 ‰ instead of 10 ‰ for a standard profile of the frog.It was established that increasing a load on the frog to 60 % at the expense of a deflection under the frog beam leads to the accelerated disarrangement of the frog, as a result of fatigue defects at the rolling surface, while the cost of frog operation in this case increases by five times.We modeled a dynamic interaction between the rolling stock and a standard, as well as the proposed, longitudinal profiles of frogs. Calculation of dynamic processes of the nonlinear interaction between the rolling stock and a standard profile of the frog and the profile restored by surfacing, showed that the magnitude of forces for the proposed frog at the motion speed of 150 km/h is 50 % lower compared with a standard longitudinal profile. At linear simulation of dynamic additions of forces, the magnitude of forces decreases for the proposed profile to 30 %.We employed a graphical method to calculate the magnitudes of axial inertia moments and the moments of resistance in the characteristic cross sections of the frog. The estimation of the stressed-strained state of the frog was performed using equations of five moments for a continuous beam on elastic point supports. It was established that stresses at the static calculation of the frog are low and are much less than the maximum permissible magnitude of stresses for a given grade of steel. Therefore, we can argue that the frog works under a load at the expense of existing reserve of strength

Procedure for Determining the Thermoelastic State of A Reinforced Concrete Bridge Beam Strengthened with Methyl Methacrylate

This paper reports the analysis of methods for determining temperature stresses and deformations in bridge structures under the influence of climatic temperature changes in the environment. A one-dimensional model has been applied to determine the temperature field and thermoelastic state in order to practically estimate the temperature fields and stresses of strengthened beams taking into consideration temperature changes in the environment. The temperature field distribution has been determined in the vertical direction of a reinforced concrete beam depending on the thickness of the structural reinforcement with methyl methacrylate. It was established that there is a change in the temperature gradient in a contact between the reinforced concrete beam and reinforcement. The distribution of temperature stresses in the vertical direction of a strengthened reinforced concrete beam has been defined, taking into consideration the thickness of the reinforcement with methyl methacrylate and the value of its elasticity module. It was established that the thickness of the reinforcement does not have a significant impact on increasing stresses while increasing the elasticity module of the structural reinforcement leads to an increase in temperature stresses. The difference in the derived stress values for a beam with methyl methacrylate reinforcement with a thickness of 10 mm and 20 mm, at elasticity module E=15,000 MPa, is up to 3 % at positive and negative temperatures. It has been found that there is a change in the nature of the distribution of temperature stresses across the height of the beam at the contact surface of the reinforced concrete beam and methyl methacrylate reinforcement. The value of temperature stresses in the beam with methyl methacrylate reinforcement and exposed to the positive and negative ambient temperatures increases by three times. It was established that the value of temperature stresses is affected by a difference in the temperature of the reinforced concrete beam and reinforcement, as well as the physical and mechanical parameters of the investigated structural materials of the beam and the structural reinforcement with methyl methacrylat