Calculation Method Of Strength Research Articles

Interfacial interaction mechanism and theoretical bond strength model between UHPC-CA and steel bar

The bond property is the basis of the bear collectively load between the steel bar and Ultra-High Performance Concrete with Coarse Aggregate (UHPC-CA). In this paper, the theoretical calculation method of bond strength between UHPC-CA and high-strength steel bar is studied. The chemical adhesion strength, friction coefficient, and mechanical interlock process of the two were investigated respectively through the refined bond property tests. The failure model is established from the interlock failure characteristics, and the bond strength is obtained theoretically. Results show that the chemical adhesion strength and friction coefficient between UHPC-CA and steel bars are 0.07 MPa and 0.5, respectively. The friction coefficient between UHPC-CA is 1.15. The interlock failure process of UHPC-CA and steel bars can be divided into three stages: uncracked stage, crack development stage, and split stage. The crack develops at an angle of 52° to the steel bar's axis and tends to stagnate at a height of 4.5 times the rib. A theoretical bond strength model is established and it is proved that the model is applicable not only to UHPC-CA but also to UHPC. This study can provide a theoretical basis for determining the anchorage length of steel bars in the design of UHPC-CA/UHPC structure, and can also provide a reference for the formulation of relevant standards.

Failure mechanism analysis and support strength determination of deep coal mine roadways – A case study

In order to solve the problems related to deformations, failures, and difficulties in support controls of deep coal mine roadways, the typical failure forms and characteristics of deep coal mine roadways were investigated and analyzed in this study. The distribution laws of plastic zones of circular roadways under different lateral pressure coefficients were expounded using a theoretical analysis method, and the influence of plastic zone scopes on the failure forms of roadways was explained. In addition, considering the distribution characteristics of plastic zones, a calculation method of the required support strength based on the plastic zone scopes was proposed. The primary and secondary factors affecting the support strength were then determined. A numerical simulation method was applied in order to analyze the distribution characteristics of the displacements and plastic zones of deep mine circular roadways under the conditions of no support scheme, an existing support scheme, and a support scheme determined by the proposed support strength calculation method (referred to in this study as the optimized support scheme), respectively. The simulation results showed that the support effects of the optimized support scheme were superior to those of the existing support scheme, and thereby more conducive to maintaining roadway stability. In addition, an on-site engineering test method was used to identify support schemes for bolting and shotcrete with wire mesh + concrete-filled steel tubular supports based on the plastic zone scopes and the support strength of roadways in order to determine the support parameters. As indicated by the field monitoring results, the proposed support strength calculation method and optimized support scheme had shown the ability to effectively control the large deformations of the tested roadway, and thereby guarantee its overall stability.

Research on simulation calculation method of local strength of swath ship stabilizing fins based on sub-model method

Abstract At present, there is little research on the strength simulation calculation method of local steel structure at the joint between the fin stabilizer and hull of SWATH at home and abroad. Aiming at the problems of high-stress levels and difficult local strength of the local structure at the joint of SWATH submersible and stable fin, this paper, based on APDL language, takes a SWATH ship as an example, establishes a whole ship simulation model, analyses and studies the modeling scope, modeling requirements, boundary conditions, and loading methods of the local calculation model of stable fin, and puts forward an efficient simulation calculation and analysis method, namely sub-model method, which is suitable for the local strength calculation of stable fin, and provides guidance for the structural design method of the stable fin of SWATH catamaran.

Strength calculation method and numerical simulation of slender concrete shear walls with CFRP grid-steel reinforcement

A series of experimental research has demonstrated superior hysteretic behavior, damage mitigation, and self-centering properties of concrete shear walls incorporating CFRP grid-steel reinforcement. Developing comprehensive theoretical and numerical models becomes crucial to assess the performance of these novel walls for structural design and application purposes. Based on the preliminary experimental investigation, a strength calculation method and numerical model for slender concrete shear walls with CFRP grid-steel reinforcement were proposed in this study. The calculation method provided a stable estimation for the loading capacity and ultimate compressive strain of edge concrete for the slender CFRP grid shear wall. The fracture strain of outermost longitudinal CFRP grid and ultimate compressive strain of edge concrete were suggested for design. The numerical model integrated hybrid reinforcements and utilized MVLEM to simulate the nonlinear hysteretic behavior of CFRP grid shear walls, effectively considering specimen failure mechanisms. The model can well capture the hysteretic behavior of the specimen, involving the peak loading, envelope curve, residual deformation, and stiffness degradation. Finally, the parametric analysis was conducted to further investigate the effects of axial compressive ratio and aspect ratio on shear walls with CFRP grid-steel reinforcement.

Experimental study on the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh

This study aims to investigate the flexural behaviors of ECC-reinforced masonry beams with GFRP mesh under various interface treatment methods. Eleven sets of ECC-reinforced masonry beams with GFRP mesh were fabricated and subjected to a four-point bending test. The effects of the fibre volume fraction and thickness of ECC, interface treatment methods, GFRP mesh strength and layers on the flexural behavior of masonry beams were investigated and analyzed, including the failure mode, crack distribution, flexural strength, and load-deflection curves. The test results revealed that a transition in the failure mode of masonry beams from brittle failure to interfacial stripping failure or ductile failure after reinforcement. Increasing the number of GFRP mesh layers, the fibre volume fraction and thickness of ECC improved the flexural performance of the masonry beams, while increasing the GFRP mesh strength had the opposite effect. Among the variables, the interface treatment method exerted the greatest influence on the flexural performance of the masonry beams. The masonry beams treated with a bolt interface exhibited the best flexural performance, with flexural toughness and ultimate deflection increasing by 1.69 times and 0.32 times, respectively. Furthermore, the flexural performance of the masonry beams reinforced with a 15 mm thick ECC and single-layer GFRP mesh demonstrated similar reinforcement effects to the masonry beams reinforced with a 20 mm thick ECC, while reducing costs by 23 %. Based on the existing codes governing the calculation method of flexural strength and considering the influence of various factors, a calculation model for the flexural strength of ECC-reinforced masonry beams with GFRP mesh was established.

Theoretical study on 3D elastic response and first layer failure strength of composite cylinders subjected to axisymmetric loadings

The traditional Lekhnitskii 3D elastic theory can obtain the exact stress and strain response of the composite cylinder under the axially symmetric loadings. However, when the cylinder contains 0° winding layers or isotropic layers, some calculation parameters corresponding to the two kinds of special layers will become singular. By analyzing the continuity of singular parameters and calculating their limits, the problem of singular parameters can be effectively solved and the Lekhnitskii theory can be extended to composite thick-walled cylinders with arbitrary winding angles. Furthermore, based on the Chang-Chang strength criterion of composite layers and the ideal elastic-plastic assumption of isotropic metal layers, the theoretical calculation method of first layer failure strength and the corresponding failure modes of the composite cylinders subjected to axisymmetric loadings was proposed. Then, the composite cylinder with metal liner was fabricated by fiber winding process. The experimental blasting pressure of the cylinder was 52.8 MPa with a major failure mode of fiber tensile fracture. Based on the proposed theoretical method, the cylinder's first layer failure strength of internal pressure was 44.1 MPa, and the initial failure mode was also fiber tensile fracture. The predicted result of the first layer failure strength was lower than the experimental results. The result proved the safety and economy of the proposed theoretical method for the initial design of the composite cylinder.

Seismic performance and flexural strength prediction of high-strength bar reinforced UHPFRC walls under high axial load ratio

A new-type shear wall built with high-strength reinforcement and ultra-high performance fiber reinforced concrete (UHPFRC) is proposed in this paper, aiming to solve the problem of too large cross-section size of bottom shear wall members of high-rise and super high-rise buildings. Four UHPFRC wall specimens built with high-strength reinforcement were tested under cyclic loading to examine the influence of the parameters of fiber volume fractions (0 vs. 1.5% vs. 2.5%) and the spaces of horizontal distribution reinforcing bars (150 mm vs. 300 mm) on the seismic performance. In addition, a calculation method of flexural strength of UHPFRC shear wall is established. The research results show that: the UHPC wall specimen without fibers failed in the axial compression brittle mode, and the UHPFRC wall specimens with fibers failed in flexure-dominated ductile mode. The bridging effect of steel fibers at the cracks kept the integrity of the UHPFRC. The drift ratio capacities of the UHPFRC wall specimens under high axial compression ratio of 0.5 were 3.56%. Increasing the fiber volume fractions can improve the strength, initial stiffness, and cumulative energy consumption of the wall specimens, reduce the damage degree of the UHPFRC at the toes of the wall specimens, and can also reduce the reinforcement ratio of horizontal reinforcement without influence on the seismic performance. The proposed method of flexural strength of UHPFC walls shows reasonable prediction accuracy.

Implementation of the split-beam function to Mills cross multibeam echo sounder for target strength measurements

Abstract Modern challenges in the increasing exploitation of aquatic ecosystems require efficient, reliable, and noninvasive technologies to acquire biomass information on a large scale. For the past 40 years, hydroacoustics has been an essential tool to analyse fish populations and their relationship with the environment. Currently, split-beam echo sounders are standard tools used to reliably and accurately record data in oceans, estuaries, and lakes. To maximize the coverage volume and to increase target detection, and therefore data quality, the use of multi-beam echo sounders is a real asset. We propose here an innovative method for target strength (TS) calculation based on the signal from a reversible Mills cross multi-beam sonar, SeapiX (Exail), which also includes the analytical capability of a split-beam echo sounder. This innovative approach provides new original information when using a multi-beam sonar. The case study in Lake Bourget was based on a comparison of the simultaneous recordings of SeapiX and EK80 (SIMRAD) to prove the validity of this multi split-beam processing, as well as to estimate the in situ TS of fish.

Early mechanical properties and strength calculation method of slag-based alkali activated concrete

The use of slag-based alkali-activated concrete (AAC) could effectively address the issues of resource extraction and carbon emissions caused by traditional Portland cement. In this study, the effects of the fly ash content, water–binder ratio, and alkali activation modulus on the early mechanical properties of AAC were investigated. A total of 105 cube specimens (35 sets) were designed and subjected to compressive strength tests, scanning electron microscope tests, and x-ray diffraction composition analysis. The results indicated that excellent early strength was observed in AAC, with a compressive strength reaching ∼90% of the 28th day strength before 14 days. An increase in the fly ash content and a decrease in the water–binder ratio significantly improved the compressive strength within the same age period. The impact of a lower alkaline activation modulus on strength was found to be insignificant. Based on the experimental results, a calculation method and a constitutive model for early strength were proposed, and the theoretical values exhibited a high level of agreement with the measured values.

Analysis and modeling of radio propagation fading characteristics in tunnel construction

With the development of underground rail transit, the concept of intelligent tunnel construction has been proposed and promoted. High-quality networking during tunnel construction is a prerequisite for this, making it highly urgent to establish networking during tunnel construction. When studying intra-tunnel networking, it is necessary to consider the propagation characteristics of radio waves in the tunnel. In this paper, according to the actual needs of engineering in tunnel construction and the characteristics of tunnel scenes, an improved ray tracing method is proposed, which considers the type and installation position of antennas, transceiver frequency band and power in channel modeling, and proposes a field strength calculation method under different coordinate systems according to the characteristics of straight and curved segments during tunnel construction. In addition, the propagation characteristics of radio waves in dynamic tunnel construction scenarios are quantitatively analyzed. In this paper, by establishing antenna diagram, two-dimensional and three-dimensional models of tunnels, the computer simulation method is applied to compare with the improved algorithm, and the results have good consistency, in addition, the improved algorithm does not require a lot of modeling work in the early stage, and has high applicability and portability. Not only that, this paper also makes actual measurements of the subway under construction in Zhengzhou, China in different scenarios, and verifies the effectiveness of the method.

Study on Peeling Performance of T-Type Brazing Joints Based on Energy Method

Brazing technology is widely used in modern industrial systems as an important connection method. The brazing joints are the weakest zone in the whole structure and directly determine the working efficiency and life of the entire system. However, the research on the connection mechanism and fracture behavior of brazing joints is still unclear. In this study, the peeling force and displacement curves during the peeling process are tested by using T-type specimens. Based on the cohesive zone model, the peeling energy of each part during the whole peeling process is calculated and analyzed. The results show that the whole peeling process can be divided into three stages, including the initial stage, crack propagation stage, and stable peeling stage. The peeling energy of each stage can be calculated experimentally. The larger the peeling energy, the better the joint performance. Then, a simplified calculation method for peeling energy is developed for T-type joints and is verified as accurate using experimental data. It is also observed that the increase in the base material thickness can effectively improve the peeling performance of the joints. This provides a feasible and effective method for peel strength calculation and evaluation in brazing joints.

Study on the interaction between hydraulic fracture and natural fracture under high stress

The existence of natural fractures in the reservoir has a great influence on the formation of complex fracture network, but the interaction between hydraulic fractures and natural fractures under high stress was rarely studied. Through laboratory tests, the law and characteristics of the interaction between hydraulic fractures and natural fractures under high stress were studied from the aspects of natural fractures angle, size, quantity, production method and ground stress in this study. Based on these interaction characteristics, a complex fracture network formation method of deep reservoir was proposed, which provided reference for engineering practice. The criterion of interaction between hydraulic fracture and natural fracture was improved, and the calculation method of rock tensile strength in three-dimensional state was proposed, which was applied to the criterion of fracture opening and fracture expansion. Combined with laboratory tests, a special interaction mode of hydraulic fracture passing through a certain position from the direction to end A (F-Type crossing mode) under high stress was proposed, and the criterion of this interaction mode were obtained. The three-dimensional finite discrete element model (FDEM) was used to investigate the effects of natural fracture strength and fracturing fluid viscosity on hydraulic fracture propagation under high stress. The results showed that the natural crack strength has great influence on the width, volume and shape of hydraulic crack. Small difference of fracturing fluid viscosity has little influence on fracture propagation, but high viscosity fracturing fluid has a greater influence on fracture propagation. This study provided reference for hydraulic fracturing engineering.

Graphical analysis-based calculation method of concrete strength

This study established a three-dimensional random spherical aggregate model of concrete. Models with various volume contents of coarse aggregate were sliced, and slice areas were statistically analyzed. To study the effects of the coarse aggregate volume content and the interfacial transition zone (ITZ) strength on concrete’s compressive strength, a concrete strength calculation method based on graphical analysis was proposed. The ratio of crown area B to sectional area A of the spherical aggregate model was found to be close to 1.5. At the ITZ strength below 70% of the mortar strength, the increased volume content of coarse aggregate reduced the compressive strength of concrete, with the opposite trend observed at the ITZ strength exceeding 70% of the mortar strength.

Eccentric load-carrying capacity calculation of L-Shaped Columns with recycled aggregate concrete-filled tubes

A composite L-shaped column made of square steel tubes filled with concrete is well-suited for residential steel structures because it effectively prevents the beams and columns from protruding from the walls, thus maximizing the usable space within a room. Recycled aggregate concrete (RAC), a sustainable material, can efficiently recycle construction waste and reduce energy consumption. However, compared to natural concrete, RAC has lower elastic modulus and compressive strength. When RAC is filled into steel tubes, it effectively restrains the RAC and allows it to support the internal buckling of the steel tubes. This study investigates L-shaped columns of recycled aggregate concrete-filled steel tubes (L-RACFST) through eccentric compression tests and numerical validation. By applying the superposition principle, the study evaluates the eccentric compression strength calculation method of L-RACFST columns and plots the N-M relationship curve. Comparing the results of the tests and numerical studies, it is evident that the derived formula is reliable for predicting the eccentric compression bearing capacity of L-RACFST columns. Furthermore, the N-M relationship curve drawn from the formula provides a more accurate prediction of safety. This paper delves into the stress mechanisms of L-RACFST columns under eccentric compression loads. The calculation formula can be used to determine the bearing capacity of L-RACFST columns under eccentric compression loads, and the N-M relationship curve can be employed to predict the safety performance of L-RACFST columns under such loads.

United composite strength calculation method for special-shaped CFST columns with multiple cavities

The present study investigates the method of calculating the composite strength of special-shaped concrete-filled steel tube (CFST) members with multiple cavities. Based on the research findings of CFST unified theory and some tests, a quantitative method to evaluate the concrete constraint effect is proposed for cross-sectional shapes ranging from regular triangles, squares…regular octagons to circles. The cross-sectional composite strength of regular polygonal CFST members is determined by the way dividing the concrete into effective and ineffective constraint regions, discounting constraint coefficients, and applying unified formulas. Additionally, a regression analysis is conducted to establish the relationship between interior angles and constraint effects. Subsequently, using quadrangle CFSTs as an example, this study investigates the relationship between cross-sectional regularity and constraint effect, and proposes a composite strength calculation method related to it. Finally, the special-shaped multi cavity cross section is separated into several simple polygonal cross sections, taking into account shape efficiency and regularity, to calculate the composite strength of each cavity CFST member and summarize them for determining the total axial compressive bearing capacity. The research findings indicate that a linear relationship exists between the interior angle of the cross section and the initial tangent line angle of the second-degree curve, which serves as the boundary between effective and ineffective constraint regions in regular polygonal steel tube confined concrete. The proposed unified composite strength calculation method, specifically designed for special-shaped CFST columns with multiple cavities, can accurately predict their actual strength.

Design oriented shear strength prediction model of UHPFRC beams

The application of Ultra-high performance fiber reinforced concrete (UHPFRC) to beams can effectively improve their strength and ductility properties. At present, there are more shear test studies on UHPFRC beams, but few theoretical studies on their strength calculation method. The fibers in UHPFRC can inhance the strength of the beams, and how to quantify the fibers’ contribution to the total strength is a research difficulty. Firstly, the shear strength database including 197 UHPFRC beam specimens is created. The key characteristics determining the shear strength, namely fiber volume fraction, stirrup configuration, and shear-span ratio, are determined by evaluating the test results. Then, considering the effects of the factors above, a truss-arch model is developed. The arch shear strength is determined by utilizing the shear deformation coordination of the arch compression structs and truss compression structs. Superimposing the shear strengths of the arch and truss models yields the shear strength of UHPFRC beams. Finally, the accuracy and reliability of the proposed method are assessed using the test database and compared to existing shear strength calculations. The study findings demonstrate that the mean value of the calculated to observed shear strength ratios produced by the suggested technique is 1.10, with a coefficient of variation of 0.28, indicating that the proposed method has superior calculation accuracy and reliability than existing methods.

Seismic performance of concrete-encased CFST column to RC beam joints: A practical model

This study proposed a practical model of the concrete-encased concrete-filled steel tubular (CFST) column to reinforced concrete (RC) beam joints based on the experimental and analytical investigations in companion publications. The analytical work was conducted to figure out the load transfer mechanism in the panel zone with considerations of the geometric features, material strengths and the axial load level. The strength calculation method was proposed according to the mechanical principle and parametric study for the beam, column and panel zone, respectively. The strength calculation method was proved to be consistent with the measured results and could reflect the actual failure mode. Then, a hysteretic model for the panel zone was developed that considered the stiffness degradation, which was verified by test results and FEA simulations. Finally, the practical model was proposed, which could simulate the failure mode, the strength and the cyclic behaviour of the composite joint. The predicted results of the proposed practical model coincided nicely with the test results of both composite members and joints, which indicated that the practical model could be used in the seismic analysis of the specified frame structures.

Lamina Influences on Tensile Strength of Shallow Marine Shales from Upper Ordovician, Western Ordos Basin.

To investigate the influence of the lamina effect on the tensile strength of shallow marine shales and improve the shortcomings of the existing Brazilian standard disc splitting method, the Lamina shale of the Upper Ordovician Wulalik Fm in the western margin of the Ordos Basin was selected as the experimental object. Based on the radial wave velocity anisotropy test, the direction of crustal stress was determined, and standard cores were drilled. The Brazilian standard disc splitting experiment on Lamina shale with different loading angles was designed and carried out. The influence of lamina on the tensile strength of shale was summarized, and an improved calculation method of tensile strength was proposed. The experimental results indicate that the presence of lamina makes the tensile strength of shallow marine shale exhibit significant anisotropy, and the fracture surface morphology of standard discs under different loading angles varies greatly. The overall failure characteristics can be classified into two types: linear and curved. When the loading angle is 0° or 90°, the fracture surface of the disc belongs to tensile failure (linear type), and the traditional splitting method has good applicability. When the loading angle is greater than 0° and less than 90°, the fracture surface of the disc belongs to tensile shear failure (curve type), and traditional splitting methods are not applicable. There is a difference in tensile strength between vertical and horizontal wells, and vertical wells should consider the comprehensive tensile strength of the rock matrix and lamina at a 90° loading angle. Horizontal wells should consider the tensile strength of the weak lamina plane with a loading angle of 0°. The improved Brazilian splitting method solves the problem of the traditional method, calculating lower tensile strength values when the loading angle is greater than 0° and less than 90°. This provides important basic data support for wellbore stability evaluation and reservoir stimulation transformation.

ПОВЫШЕНИЕ НАГРУЗОЧНОЙ СПОСОБНОСТИ МЕЛКОМОДУЛЬНОЙ ЧЕРВЯЧНОЙ ПЕРЕДАЧИ

The study objective is to analyze possible ways to increase the load capacity and develop a worm gear that meets the following requirements and working conditions: minimum weight, high reliability, maintenance-free, short-term operation mode, limited lubrication conditions, the ability to work at low temperatures. The task to which the paper is devoted is to increase the load capacity and the wear resistance of worm gears. The load capacity is defined as the possibility of transmitting the greatest torques with the smallest overall dimensions. The research methods are based on the theory of strength, theory of elasticity, mechanics of contact interaction. The novelty of the work is in finding effective design and technological ways to increase the load capacity, developing a modification of the worm gear and testing the method for calculating the strength of the transmission with a globoidal worm.
 Research results: a review and analysis of the results of studies concerning the modification of gear, working conditions, lubrication, manufacturing technology, wear; possible methods of increasing the bearing capacity of a small-module worm gear are considered; a modification of the gear with a globoidal worm is developed; a method of strength calculation is tested.
 Conclusions: the method of strength calculation and the method of modification of the globoidal gear allow improving the quality characteristics of worm gears – weight and size characteristics, reliability, resource, ease of operation.

Research on the calculation method of concrete compressive strength based on volume content of recycled coarse aggregate and fine aggregate

ABSTRACT In order to study the influence of physical properties and volume content of coarse aggregate on concrete strength, the effective water absorption, apparent density and crushing index of different types of coarse aggregate were tested; the contribution strength coefficient and reinforcement coefficient of coarse and fine aggregate were proposed according to the mechanics of composite materials, the optimal range of the volume content of coarse and fine aggregate was determined, the calculation equation of concrete compressive strength based on the properties of coarse aggregate and the volume content of coarse and fine aggregate was established. The results show that: the effective water absorption of recycled brick aggregate (RBA) is 8.18% and that of natural aggregate (NA) is 0.32%; the apparent density of NA is 2713 kg/m3 and that of RBA is 2100 kg/m3; the crushing index of NA is 18.07% and that of RBA is 30.59%; furthermore, the crushing value of RBA is close to that of cement mortar with water cement ratio of 0.46; NA has a greater range of strengthening the compressive strength of concrete than RBA; when sand cement ratio is between 0.3 and 2.5, both Ks’ and Ks are greater than 1; when sand cement ratio is about 0.5, Ks’ reach the maximum value; when sand cement ratio is about 0.75, Ks reach the maximum value; the calculation equation of concrete compressive strength established in this paper has a good prediction effect, which provides a new idea for the calculation method of concrete compressive strength.