Redistribution Of Forces Research Articles

The influence of profiled sheeting layout on purlin on redistribution of truss elements forces

The article is devoted to the analysis of the influence of profiled sheeting layout, taking into account its continuous behaviour on redistribution of truss elements forces. Trusses of the Molodechno type with a span of 30 m from bent-welded box-section profiles were taken as an object of study. Depending on the roof configuration, 7 design cases were formed. In each case, the sections of the truss elements are first selected without taking into account the operation of the profiled sheet, and then a check is made taking into account the location of the profiled sheeting on the purlin. Comparison of numerical experiments’ results, in particular nodal loads and section utilization factors, was performed. The above mention data allow to conclude necessarity of taking into account the operation of profiled sheeting when calculating the elements of the coating.

ГЕНДЕРНАЯ ПРОФЕССИОНАЛЬНАЯ СЕГРЕГАЦИЯ И УРОВЕНЬ ОБЩЕЙ БЕЗРАБОТИЦЫ МУЖЧИН И ЖЕНЩИН

The subject of the study is gender professional segregation by type of economic activity. The purpose of the paper is to attempt to assess the contribution of gender segregation of employees by type of economic activity to the formation of differences in the level of general unemployment of women and men. The relevance of the study is determined by the need to improve the quality and efficiency of women’s professional employment. The scientific novelty lies in the disclosure of new factors in the formation of differences in the level of general unemployment of women and men. The research methods are logical analysis, mathematical statistics, and mathematical modeling. The level of gender segregation by type of economic activity was determined using the Duncan index. The main calculations were made based on data from 2017–2019. The following research results were obtained: a large-scale reduction in gender segregation by type of economic activity in order to reduce the gap between the wage levels of women and men, carried out only as a redistribution of women to male professions and activities, without organizing a counter redistribution of male labor forces, may create a threat of increasing the level of general unemployment among women and increasing personnel shortages in highly feminized public sectors. The author concludes that it is necessary to develop alternative ways to reduce the gap between the wage levels of women and men in the economy, for example, increasing the prestige and wages in highly feminized public sectors such as education, healthcare, and science.

Foundation capacity rating in karst area conditions

The article provides a calculation on the influence of the formation of a karst hole, or sinkhole, beneath the monolithic foundation slab of the building. It follows from the calculation, that monolithic reinforced concrete structures are capable of bearing the load action and ensuring the safe operation of the structure in conditions of the eventual formation of a designed karst funnel. Calculation of the foundation of the building under consideration for an emergency event of a soil caving with a diameter of 3 m and a depth of 10 m, demonstrated, that displacements, greater in value than the original ones, do not occur as a result of the redistribution of forces during normal operation of the building structure.

Consideration of external reinforcement based on carbon fibers for the redistribution of bending moments in slabs

Girderless monolithic floors represent the main constructive technique primarily for residential buildings – an important component is the saving of space in contrast to girder structures. In addition, these structures are typical for other buildings. The issue of punching in monolithic girderless ceilings is one of the most important issues. At the same time, as a rule, only one task is solved – reinforcement from punching and the issue of the stress-strain state of the structure as a whole is completely ignored. This fact leads to an uncharacteristic redistribution of forces in the structure, which ultimately leads to destruction. This article discusses specific examples of calculations and objects with an analysis of the redistribution of moments and the final convergence of the calculation results. In conclusion, the key conclusions are made

Обоснование необходимости реинжиниринга бизнес-процессов на предприятиях российского ТЭК

The article considers the application of the process approach in the management of enterprises of the fuel and energy complex. In conditions when the fuel and energy sector plays a key role in the economy of a country like Russia, with increased uncertainty and complexity of forecasting changes in the external environment, it is necessary to develop new approaches to managing business processes in this area. The rapid transformation of the global balance in the energy market, the redistribution of forces and gravity points taking place at the moment, set new development goals for the entire industry as a whole and for individual companies. We should not lose sight of the sanctions pressure caused by the escalated political confrontation between Russia and Western countries.
 It is proposed to identify key business processes at fuel and energy complex enterprises and to justify methodological approaches to their reengineering, taking into account the specifics of the industry and the need for a qualitative change in the behavior model of fuel and energy complex enterprises in new macroeconomic conditions.

Study and Monitoring of Driving Forces that Arise at the Contact Point Between the Wheel Border and the Rail during the Motion of the Rail Vehicle on a Curved Path of the Railway Line

One of the most acute problems faced today by Railway Transport Companies is the rapid wear of locomotive wheel borders in the freight transport. Hence, the purpose of this article is to find ways to reduce the forces acting on the wheels of railway vehicles, generally during their movement in small radius turns. For means of simplification has been assumed that the train is moving at uniform speed during a curved path. Analyzing the scheme of action of forces on the pair of wheels, we see that one of the ways to reduce this consumption phenomenon is to reduce the parasitic moment of frictional forces. With reference to the practice of roller-contact studies, we modeled mathematically the redistribution of frictional forces at the point of contact of the wheel – rail pair and realized two computer models for two variants of wheel profiles: conical and curved.
 
 Received: 23 September 2022 / Accepted: 28 November 2022 / Published: 20 December 2022

Effect of creep on the strength of high strength concrete-filled steel tubes

High strength concrete filled steel tubes (HSCFSTs) are being increasingly used as columns in tall buildings, bridges, and other critical infrastructure and complex structural systems. Very little research has been done to study the performance of these columns under long-term sustained loads where creep effects take place, and no study exists on the long-term performance of these columns under eccentric sustained loads at the large scale. Six large scale (2700 mm height) HSCFSTs were tested in this paper under sustained eccentric compression for a period of five months. After that, the columns were tested to failure and their performance was compared to another six companion HSCFSTs that were kept unloaded for the same time period. A decrease of about 13% in the load carrying capacity was observed after creep. It was also observed that creep significantly changed the force distribution between steel and concrete. A study of the force redistribution showed that the force carried by the steel increased by >50% of its initial value.

Deformation approach to the calculation of compression resistance of reinforced stone elements

Introduction. When calculating stone and reinforced stone elements, only the limiting stage before destruction is considered, the nonlinearity of deformation of materials and, accordingly, the redistribution of forces between masonry and longitudinal reinforcement in cross sections are not taken into account. A deformation approach to the calculation of compression resistance of reinforced stone elements is considered. It allows us to take into account the physical nonlinearity of deformation of materials of reinforced stone elements.
 
 Materials and methods. Accounting for physical nonlinearity is based on using deformation diagrams under “compression – tension”. Approximations of diagrams are given. A sample of experimental studies of the most characteristic armoured stone elements has been compiled according to the data of studies published in open sources.
 
 Results. The prerequisites for using a deformation approach to the calculation of reinforced stone elements are formulated. As a criterion for calculating the compression resistance at the ultimate strength stage, it is proposed to take the maximum force calculated from the condition of compatibility of deformations of masonry and longitudinal steel reinforcement. Algorithms for calculating the compression resistance and parameters of the stress-strain state of reinforced stone elements at any level of loading are compiled.
 
 Conclusions. The proposed calculation method makes it possible to obtain the parameters of the stress-strain state of elements of arbitrary cross-section shape with any reinforcement parameters and various eccentricities of longitudinal force application at all loading levels. A calculation criterion is proposed to take into account the redistribution of forces in the cross-section of armoured stone elements. Verification of the calculation method was performed on a sample of experimental data, which showed good convergence of theoretical and experimental values of load-bearing capacity and deformability.

Proposal of concept for structural modelling of hybrid beams

Abstract Investigation on the behaviour of a hybrid beam is presented. Hybrid beam stands for an element with hybrid cross sections. This means sections that consist of steel and concrete parts, connected together with composite dowels, and both are considered for shear flow analysis. In practice, a more general solution may be used for bridges in the form of a beam in which the span sections are hybrid and the support sections are concrete. Recently such a solution has been introduced for bridge engineering in Poland and a new problem with performing a global analysis of hybrid beams was identified. The solution is new itself and requires also a new approach for internal forces determination. Discussion of this problem is made in the paper. Influences of (1) concrete cracking, (2) rheology of concrete and (3) methods of modelling on the redistribution of internal forces are highlighted. On an example of one of the real bridge girder (being currently under design) analysis is made to show how the abovementioned factors are affecting obtained results. Results are analysed and conclusions are presented. As a final step, a new concept of hybrid beam design is proposed. The proposed solution enables a quick and easy engineering approach to perform a static calculation of the considered structure.

Influence of sustained loading on resistance and deformation capacity of reinforced concrete members in compression

AbstractAs acknowledged explicitly or implicitly in most of current design codes, a high level of sustained loading has a detrimental effect on the concrete compressive strength. However, its beneficial effect in terms of deformation capacity is neglected in most cases. This latter topic and its practical consequences are addressed in the present paper on the basis of an experimental and theoretical investigation. In particular, the development of nonlinear creep strains in structural concrete members is investigated, clarifying the internal redistribution of forces between concrete and the reinforcement. The results of an experimental program with refined measurements are presented to better understand the phenomenon and to verify the predictions of a mechanical model developed by the authors on the time‐dependent response of concrete. The experimental program consists of 14 prismatic specimens with different reinforcement ratios tested under a wide range of uniaxial stress rates. The results allow clarifying the material response and validating the mechanical model, both in terms of strength reduction and enhancement of deformation capacity. Finally, the results of parametric analyses, performed considering different concrete ages, reinforcement ratios, and materials properties are presented to evaluate the practical implications of the findings.

The Influence of Flexural Reinforcement Yielding on the Shear Strength of Reinforced Concrete Beams with and without Shear Reinforcement

Statically indeterminate structures such as continuous beams allow redistribution of internal forces. For increasing loads after yielding of the flexural reinforcement, shear forces may increase, making it possible to reach shear failures after the full flexural capacity of the structure is developed.
 An extensive experimental programme consisting of 30 shear tests (15 cantilever tests and 15 continuous beam tests) was carried out to assess the shear strength of reinforced concrete beams with and without shear reinforcement. Some of the tests were designed to fail in shear after yielding of the flexural reinforcement. The main objective of this experimental study was analysing the influence of large flexural strains on shear strength.
 The tests were instrumented by means of surface measurements using Digital Image Correlation (DIC). These measurements allowed controlling the evolution of strains at concrete surface to obtain the rotation of the plastic hinges and tracking the development and kinematics of the critical shear crack to obtain, by accounting for suitable constitutive models, the contribution of the various shear-transfer actions.
 The analysis of the test results confirmed the reduction of shear strength provided by concrete with increasing flexural rotation both in tests with and without shear reinforcement. Moreover, this shear strength component weakened for increasing shear reinforcement ratios. The test results were compared with the shear strength values predicted by different design codes, showing that these formulations did not properly capture the loss of shear strength caused by plastic deformation. The proposed simplified method to calculate the shear strength of the plastic hinges accounting for the plastic rotation demand shows consistent agreement for the experimental results.

Redistribution of internal forces from the span to the support

AbstractThis paper presents the results of evaluations on the redistribution of internal forces from the span to the support area using nonlinear finite element calculations. The motivation is the internalization of bridges, particularly the reconstruction of single‐span beams arranged in a row to a continuous beam system. When integralizing a bridge, it can be assumed that the existing bridge is designed according to standards, which are no longer valid. If the integralized bridge is loaded and designed according to the new standard, the problem may be that the existing structure has insufficient reinforcement. For single‐span bridges, the flexural reinforcement in the span may be considered critical. The degree of reinforcement in the support area can then be adjusted individually, which offers the possibility of transferring internal forces from the span to the support area if they cannot be fully absorbed by the existing reinforcement.

Assessment of robustness of hinged-bar systems

Typically in structural design, foreseeable loads are assumed in a dimensioning exercise. Structures can, however, be exposed to largely unforeseeable events such as intense environmental phenomena, accidents, malicious acts, and planning or execution errors. This circumstance determines the interest in the problem of structural robustness, which has been the subject of many recent works.
 This paper focuses on methods for assessing the robustness of hinged bar systems, considering truss structures as an example. They are the simplest in terms of computation, but make it possible to fully illustrate the proposed approach.
 First, the differences between progressive collapse (description of the process) and the disproportionate propagation of local failures (description of the state) are analyzed. The generalizing nature of the concept of robustness and its differences from the concept of invulnerability are pointed out.
 The paper considers the problem of measuring robustness. The known quantitative estimates of robustness are analyzed focusing on estimates that are invariant with respect to the stress state, as more general ones. The paper considers estimates that use such properties of the stiffness matrix as the condition number, or based on a comparison of the determinants of the original and changed stiffness matrices. It is pointed out that the degree of static indeterminacy can serve only as a necessary, but insufficient measure of robustness.
 The paper considers a well-known method of robustness assessment using a redundancy matrix determined by the forces that must be applied to assemble the system from elements with the length different from the design one. This method is opposed to the use of a projection matrix, the main diagonal elements of which indicate the degree of participation of the bars in ensuring robustness. The main properties of the idempotent projection matrix are considered. The paper illustrates the possibility of recalculating the projection matrix for the changed system with the help of the Jordan elimination step. A simple example demonstrates assembling and changing the projection matrix.
 In addition to the failure of the bar, the case of its damage (partial failure) is also considered, it is shown how it affects the change in the projector and the redistribution of internal forces.

Investigation on Load Path of a Latticed Shell Structure under Localized Fire Based on Member Sensitivity

Thermal expansion of a member can affect structural bearing capacity when one or more members are subjected to fire. To explore the developmental rule of member internal force in latticed shell structure, a computation method of member sensitivity is presented based on the alternate path method. Taking a K8 single-layer latticed shell structure as the analysis object, finite element models are established by ANSYS, applying temperature loads on radial and circumferent ribs, calculating the sensitivity of each member during heating, and exploring the rule of member sensitivity at different temperatures. It is revealed from the numerical results that when one member is in fire, member sensitivity is proportional to temperature and inversely proportional to the distance from the member subjected to fire. Taking the member sensitivity coefficient as an index, the internal force will be transmitted along the member with high sensitivity, the rule of load path and internal force redistribution is given when the latticed shell structure is under elevated temperature.

Numerical investigation of dry bulk cargo load during ship vertical motion

The accurate estimation of cargo load is important for designing double bottom structures. However, dry bulk cargo load due to ship acceleration has rarely been investigated in detail. In this study, DEM (Discrete Element Method)-FEM (Finite Element Method) coupling analyses with simplified vessel models were used to evaluate the dry bulk cargo load acting on the bottom plate; the dry bulk cargo and deformation of the bottom plate were expressed by discrete and finite elements, respectively. The analyses for the first time showed the occurrence of a large force near the edge of the bottom plate and small force around the center when the bottom plate was elastic. These forces resulted in the reduction of the bending stress on the bottom plate compared to a condition assuming uniform distribution of the dry bulk cargo load. This result firstly explained that the reduction of the bottom plate bending stress in previous measurements of double bottom strain of a bulk carrier during ocean going. Above non-uniformity of the force distribution was not observed when the bottom plate was rigid. This change in the distribution was caused by the arching effect, which occurred due to interlocking between discrete elements. The amplitude of force redistribution depended on the ratio of the width of the vessels to the height of the aggregate of the discrete elements. The DEM-FEM coupling analyses also showed that an appropriate design of the hopper plate can support the inertia of the discrete element aggregate located above the flat bottom plate, and thereby reduce the force acting on the flat bottom plate.

Research on the Behavior of Stiffening Walls in Single-Storey Buildings Made of Autoclaved Aerated Concrete (AAC) Masonry Units.

Experimental identification of stiffening walls is often limited to studying single-wall models. However, these samples do not reflect many additional effects—torsion of the building and redistribution of internal forces. This paper presents the results of two full-scale buildings made of autoclaved aerated concrete (AAC) masonry elements. The primary purpose of the work was to determine the changes in the stiffness of the shear walls and to attempt the empirical distribution of loads on the stiffening walls. The intermediate goals were: a description of the crack morphology and the mechanism of failure, the designation of the stiffening walls’ behavior. It was shown that the first crack formed in the tensile corner of the door opening, and the subsequent cracks formed in the wall without a hole. Based on the changes in the value of the shear deformation angles, the phases of work of the stiffening walls were determined. The presented research results are only a part of an extensive study of stiffening walls in masonry buildings conducted at the Silesian University of Technology.

Opening to the Outside World and Income Gap between Urban and Rural Areas Based on Panel Data of 30 Provinces and Cities

Opening to the outside world has an impact on Income gap between urban and rural areas. From the perspective of internal transmission mechanism, opening to the outside world has promoted the redistribution of labor force between urban and rural areas and the increase of rural residents' wages while adjusting the industrial structure. From the perspective of external transmission mechanism, trade openness has a significant impact on Income gap between urban and rural areas through the regulation of transportation infrastructure. Based on the above analysis, this paper explores the specific impact mechanism of opening to the outside world on income gap between urban and rural areas. Using Theil index to construct an index to measure the income gap between urban and rural areas, this paper empirically explores the impact of opening to the outside world on Income gap between urban and rural areas through adjustment effect test and mediation effect test, and further explores the impact of various influencing factors on income gap between urban and rural areas and the specific transmission mechanism.

Effects of biaxial loading path on seismic behavior of T-shaped RC walls

T-shaped RC walls are commonly used to resist horizontal seismic excitations in multiple directions. The differences in the intensity and spectrum characteristics of two translational components of ground motion cause the wall to experience complex biaxial displacement trajectories, resulting in a different seismic response compared to the behavior derived from conventional uniaxial cyclic tests. Thus, to investigate the seismic behavior and coupling mechanism of T-shaped walls subjected to different magnitudes of loading in two orthogonal directions, this study examined five identical T-shaped walls under uniaxial loading along two principal axes and biaxial loading with three represented loading paths. The test results showed that the mechanical behavior in one direction was significantly affected by the loading in the orthogonal direction owing to internal force redistribution and additional stress caused by the biaxial coupling bending, resulting in vertical variation and intersection of their hysteretic curves. Further, the biaxial loading primarily aggravated the cracking and damage of the flange, which accelerated the performance degradation in the flange direction and reduced the effective flange width involved in resisting web direction load. In addition, the biaxial coupling effect was found to be proportional to the area enclosed by the loading path. Thus, the most severe damage and performance degradation were observed under a square path, followed by an eight-shaped path, with the cruciform path exhibiting the least effect. Consequently, based on the results, recommendations for the design of T-shaped walls subjected to biaxial earthquake actions were proposed.

Static Deflection Difference-Based Damage Identification of Hanger in Arch Bridges

As the most critical force transmitting and bearing components of arch bridges, the hanger is also the weakest link of the bridge. Damage to the hanger leads to a redistribution of the internal forces and potentially even the collapse of the bridge. Therefore, this paper proposes a new damage detection method for hangers. Based on the principle of superposition, the relationship between the static deflection change and cable force is studied. Then, a new index is proposed for identifying the damage to arch bridge hangers. Numerical and laboratory investigations demonstrate that this method can successfully locate damage regardless of its location; moreover, the degree of damage can be relatively quantified. In addition, the method is easy to operate and suitable for practical engineering applications.

Damage evolution of concrete under tensile load using discrete element modeling

The objective of this study is to investigate the damage evolution process in the flattened Brazilian test of concrete, and assess the effect of the maximum aggregate size on the tensile strength of concrete using the discrete element method considering the heterogeneity of concrete. Random irregular coarse aggregates were generated in each gradation according to the theoretical content. Based on this, a series of discrete element numerical models of flattened Brazilian disks with aggregates of different gradations were established, including 5–10, 5–16, and 5–20 mm, and numerical simulations of flattened Brazilian tests were conducted. Before the peak load, the compressive force was concentrated near the flat loading ends, which can be considered as the driving force for the initiation of shear microcracks, and the tensile force distributed away from the loading ends induced the appearance of tensile microcracks in the mortar and the interface transition zones (ITZs). Tortuous macroscopic cracks formed owing to the accumulation of tensile microcracks at the center of the specimen when the peak load was reached. After the peak load, secondary cracks initiated and extended gradually, and shear failure began to occur in the mortar and the ITZs owing to the redistribution of the compressive force. The failure mechanism was correlated with the displacement trends of the particles. Tensile microcracks could be associated with the tensile displacement trend of the particles. Shear and tensile microcracks co-existed in the zones where the particles moved in a mixed-mode displacement trend. The tensile strength of the concrete decreased slightly with an increase in the maximum aggregate size in the flattened Brazilian tests, and the tensile strength of the concrete was overestimated by the flattened Brazilian tests.