Development of a Mechanistic Method to Obtain Load Position Strain in Instrumented Pavement

To study the in-situ response and performance of asphalt pavement, instrumenting pavement with a variety of sensors has become one of the most important tools in the field or accelerated load facilities. In the dynamic response collection process, engineers are more concerned with the load position strain of the pavement structure due to wheel wander. This paper proposes a method to obtain the load position and the strain at the load position when there is no lateral-axis positioning system based on multilayer elastic theory. The test section was paved in the field with installed strain sensors to verify and apply the proposed method. The verification results showed that both the calculated load position and load position strain matched the measured values with an absolute difference range of 5–60 mm, 0.5–2.5 με, respectively. The application results showed that the strain at the load position calculated by the proposed method had a good correlation with the temperature, as expected.

Improving the algorithm of choosing spacing and number of stiff supports against a concentrated force in steel-concrete beams

A steel-concrete beam was taken as the study object. The algorithm of selecting the number of stiff supports for the steel-concrete beam loaded with a concentrated lateral force in the middle of the span has been refined. Stiff supports served to join the steel strip with concrete to ensure their joint performance. The algorithm was refined based on the condition of equality of the longitudinal force in the steel strip from the action of the calculated load and the maximum longitudinal force obtained after setting the supports. In this case, the longitudinal forces in all stiff supports, as well as the spacing of the stiff supports should be the same. A disadvantage of the known algorithm consists in the complexity of determining the coefficient φb2 taking into account the effect of long-term concrete creep on the element deformation without cracks. This coefficient fluctuates widely and depends on many factors. Besides, it is also insufficiently studied. Calculations for determining the number and spacing of stiff supports in a steel-concrete beam were conducted according to the proposed algorithm and in the Lira software package. The forces acting on the supports and spacing of the supports were the same. The force acting in the support was 8941.5 N. When selecting characteristics of the steel-concrete beam, maximum longitudinal force in the steel strip was obtained. The longitudinal force amounted to 35726 N. The same longitudinal force was obtained from the diagram of longitudinal forces obtained after setting the supports. This study was aimed at improving the design of steel-concrete beams. A rational number and placement of stiff supports ensure savings: the required amount of building materials is reduced and their cost is reduced due to cutting labor costs for their manufacture and operation

Relationship between mains costs and voltage switches

The article deals with the issues of interconnection of network costs and power quality, in particular voltage deviations. The graphs of the distribution of voltage deviations for electrical receivers are given for two calculated load modes - the highest (100%) and the lowest (25%), corresponding to the choice of wires of 10 and 0.38 kV overhead lines for economic loads and voltage stabilization on 10 kV buses of 35/10 kV RTP at the level of + 5%.

Load Ratios Carried by Each Constituent for Some Problems of a Particulate Composite Modeled as a Mixture of Two Linear Elastic Solids

ABSTRACTThe basic constitutive equations of theory of mixtures obtained for a mixture of two linear elastic solids can be used as an alternative way to describe the mechanical behavior of binary composite materials. Determining the load ratios carried by each constituent solid of a binary composite is one of challenges of this theory. In this study, the results of directly calculating the ratios of external load carried by each constituent solid for the case of perfectly bonded interface between binary mixture constituents are discussed. Thus, the effects of loading type and volume fraction of the constituent solids to the load ratios carried by each constituent solid are investigated by using three different loading cases and three different volume fractions. Finally, displacement, stress and diffusive force results of two constituent solids using the calculated load ratios are given.

Contact grouting taken into account when calculating arched frame supports

One of the current trends in the technology of supporting capital and preparatory workings is the use of contact grouting. The contact grouting is designed to increase the bearing capacity of the frame supports. The paper considers a method for calculating the support pressure and the displacement of the support crown. The calculation method is based on the interaction of the system of blocks “support – filling layer - broken rock layer - undisturbed rock”. The following factors were taken into account in the method of calculating the frame arch support: depth of the roadway development, mine working cross-section, the support section, the width of the filling layer and its deformation characteristics, as well as the deformation and strength characteristics of the rock mass. Checking of the support strength state is done by comparing the calculated load versus the rated bearing capacity of the support. The developed technique allows making the choice of support in various mining conditions of the application.

A Novel Calculation Method of Process Load for Extra-Large Section Tunnels

The calculation of load and surrounding rock pressure of extra-large-section tunnels serves as an important premise for the design and construction of tunnel projects with extra-large sections. Based on the large-span section of the Shenzhen Liantang Tunnel (China), which is the largest highway tunnel in the world to date, this paper discusses the challenges existing in the calculation method of state load and surrounding rock pressure for extra-large-section tunnels and puts forward a novel calculation method for process load, which is suitable for extra-large-section highway tunnels. In the current work, we derived the related application correlations and improved the specific application steps, methods, and project models of the proposed calculation method. Both the rationality and feasibility of the calculation method were verified from a practical perspective by comparing the on-site data of surrounding rock pressure at the Liantang Tunnel with the calculated load, which provides a fundamental basis for the process design of tunnels.

EXPRESS ESTIMATION OF THE ENERGY EFFICIENCY OF A CENTRIFUGAL PUMP WITHOUT EXPERIMENTAL DETERMINATION OF ITS EXPENSES

Using a mathematical model, created on the basis of the electrohydraulic analogy method, a methodology for express estimation of the energy efficiency of a centrifugal pump was developed. The design load angle for analyzing the efficiency of operating modes of hydraulic machines is determined. The dependence of the power-driven engine shaft and the total efficiency of the centrifugal pump on its calculated load angle is established. The relationship between load angle and speed coefficient, which is a prototype of an electromagnetic load angle which characterizes the synchronous machine operating mode, is determined. It is established the dependence of the main pump head on the calculated load angle and the differential pressure created by the centrifugal pump. The developed methodology makes it possible to avoid significant technical and financial difficulties, since flow meters have a high cost and certain requirements for installation, while manometers are established by the standard requirements of the technological process. The estimated value of the load angle of the centrifugal pump through its catalog parameters is determined. The operating characteristics for the main centrifugal pump of type НМ-7000-210 were calculated and built without experimental determination of its head. Such approach showed a good coincidence of calculated and experimental characteristics. Relative error of energy characteristics does not exceed ten percents. The proposed methodology can be used for express estimation of the efficiency of energy transformations of the whole electric drive pump unit. Express-analysis is a key to successful management of the energy economy through timely detection of inefficient modes of operation of electric-driven pump units and makes energy research cheaper.

Some Comments on Designing of Steel Structures According to European Standards

Critical comments on the European standards for designing steel structures including welded and bolted joints have been given on the basis of application experience and executed analysis. Comments are presented in comparison with similar regulatory documents which are in effect in Belarus. European standards concerning loads (determination of calculated load values and drawing up of design load combination) have been also analyzed. Particular attention has been paid to the analysis of European standard requirements to steel and welding materials and their comparison with mechanical characteristics of similar materials used for manufacture of steel structures in Belarus. The paper gives notice to the rules which are accepted in the European norms and the rules being compared with the similar rules used in Construction rules and regulations (SNiP) lead to a significant increase in material consumption of steel structures. First of all, it concerns assignment of partial load factors and classification of sections for ensuring local stability of compressed and partially compressed elements. The paper pays a special notice to the rules of Eurocodes that do not meet requirements of State standards and technical specifications operating in the Republic of Belarus. Significant limitations of some European rules regarding calculation of centrally and eccentrically compressed elements, absence of rules for testing overall stability of through and step columns which are widely used while implementing projects Belarus have been described in the paper. Conclusions have been made on the basis of the analysis results and according to them application of European standards for designing steel structures has significant limitations on the territory of the Republic of Belarus.

Nonlinear deformation analysis for precast pre-stressed concrete beam systems

The structural systems such as road bridge beam systems (span superstructure) or beam systems used in high-rise buildings with precast pre-stressed reinforced concrete might be subjected to the load higher than the calculated load of the design process. In the process of operation the internal forces of the beams reach to a certain value, the section stiffness in elements will be changed. The change in section stiffness will lead to redistribution of internal forces in the whole system. However, that has not been included in the design process. The paper presents nonlinear deformation analysis of precast pre-stressed beam system used in road bridge span superstructure or high-rise buildings using nonlinear model of materials according to Russian construction codes to build the relationship between internal forces and section stiffness. From the calculation results, some comments will be recommended about increased load capacity in comparison with the results obtained from analysis using linear model of material.