STUDIES ON STRESS TRANSFERENCE MECHANISM OF STEEL FIBRE REINFORCED CONCRETE

The stress transfer mechanism of steel fibre reinforced concrete is studied. The solutions for the stress and displacement were regarded as the superposition of ' the elementary solutions' and ' the improved solutions'. The elementary solutions were found by using two-dimensional elastic theory and the improved solutions were found by using the Love displacement function method. The calculated results indicate that the solutions possess good convergence. By comparing the three-dimensional solutions with the shear-lag solutions, evident difference may be found.

Stress response characteristics of BFRP anchors on loess mudstone slope under rainfall conditions

To investigate the stress response characteristics and shear stress transfer mechanism of BFRP(basalt fiber reinforced plastics)anchors under rainfall conditions and to explore the reinforcement effect of BFRP anchors,a comparative indoor physical model test was conducted in this study using loess mudstone slope as a typical case,and multi-attribute response data,such as slope displacement,BFRP anchor strain and axial force,were obtained.Based on the variation law of slope displacement,it can be concluded that the deformation displacement of the slope on the side reinforced by BFRP anchors is smaller than that of slopes reinforced with steel anchors;the bearing capacity of BFRP anchor is given priority in time,and the anchoring effect of BFRP anchor at the top of the slope is given priority,and the axial force value of anchor is characterized by a surface amplification effect in space;the axial force is higher around the anchor head and tends to decay as a negative exponential function as the anchor extends in the direction of the interior of the slope;the shear stress of BFRP anchor and anchorage body are unevenly distributed along the axial direction,with the maximum value occurring in the free section near the slope surface and decreases as the BFRP anchor extends towards the interior of the slope.These results can provide a theoretical basis for the optimal design of BFRP anchors.

On stress-forecasting strategy of earthquakes from stress buildup,stress shadow and stress transfer(SSS) based on numerical approach

Global Positioning System （GPS） and Interferometric Synthetic Aperture Radar （InSAR）, used for monitoring crust deformation, are found to be very promising in earthquake prediction subject to stress-forecasting. However, it is recognized that unless we can give reasonable explanations of these curious precursory phenomena that continue to be serendipitously observed from time to time, such high technology of GPS or InSAR is difficult to be efficiently used. Therefore, a proper model revealing the relation between earthquake evolution and stress variation, such as the phenomena of stress buildup, stress shadow and stress transfer （SSS）, is crucial to the GPS or InSAR based earthquake prediction. Here we address this question through a numerical approach of earthquake development using an intuitive physical model with a map-like configuration of discontinuous fault system. The simulation provides a physical basis for the principle of stress-forecasting of earthquakes based on SSS and for the application of GPS or InSAR in earthquake prediction. The observed SSS associated phenomena with images of stress distribution during the failure process can be continuously simulated. It is shown that the SSS are better indicators of earthquake precursors than that of seismic foreshocks, suggesting a predictability of earthquakes based on stress-forecasting strategy.

Interfacial stress transfer behavior in a specially-shaped fiber/matrix pullout test

Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber＇s embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.

Investigation of Coulomb stress changes in south Tibet(central Himalayas) due to the 25th April 2015 M_W 7.8 Nepal earthquake using a Coulomb stress transfer model

After Mw 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the 25th April event using models of regional faults designed according to south Tibet-Nepal structure, and show that some indicative significant stress increases. We calculate static stress changes caused by the displacement of a fault on which dislocations happen and an earthquake occurs. A Mw 7.3 earthquake broke on 12 May at a distance of - 130 km SEE of the Mw 7.8 earthquake, whose focus roughly located on high Coulomb stress change （CSC） site. Aftershocks （first 15 days after the mainshock） are associated with stress increase zone caused by the main rupture. We set receiver faults with specified strikes, dips, and rakes, on which the stresses imparted by the source fault are resolved. Four group normal faults to the north of the Nepal earthquake seismogenic fault were set as receiver faults and variant results followed. We provide a discussion on Coulomb stress transfer for the seismogenic fault, which is useful to identify potential future rupture zones.

Stress Transfer and the Impact of the India-Eurasia Collision and the Western Pacific Subduction on the Geodynamics of the Asian Continent

The interaction between the India-Eurasia collision and the Western Pacific subduction and their contribution to recent geodynamics of the Asian continent are discussed. We perform a comparative analysis of the data available from world literature and new data on the slow strain and earthquake migration from the India-Eurasia collision and the Western Pacific subduction zones. Based on the concepts of wave dynamics of the deformation processes, a localization scheme is constructed illustrating the migration of slow strain fronts in central and eastern Asia, and the wave geodynamic impact of collision and subduction on the Asian continent is shown.

Effects of Matrix Features on Stress Transfer of Short Fiber Composites

By employing the elastic and elastic plastic finite element method(FEM), the effects of matrix feature on the stress transfer mechanisms of short fiber composites are studied. In the calculation, the variations in matrix modulus, yield strength and hardening modulus are considered. It is concluded that large deformation of matrix is harmful to the improvement of the mechanical performances of the composites.

Some Further Considerations about the Theory of Elastic Stress Transfer from Partially Embedded Axially Loaded Fiber to Matrix

In this paper the elastic stress transfer from the fiber to the matrix is analysed for fiber-reinforced composites when the fiber is loaded axially.The dependence of the elastic stress transfer on the as- pect ratio of the fiber,the volume fraction of the fiber,the fiber-to-matrix elastic modulus ratio and the Poisson's ratio of the fiber and the matrix has been shown in detail.

The Effects of Interfaces on Stress Transfer in Short Fiber Reinforced Metal Matrix Composites

In this paper, the effects of interface properties on the stress transfer between matrix and fiber in short fiber reinforced metal matrix composites (SFRMMCs) is studied with the method of the elasto plastic finite element. The interface properties include Young’s modulus, thickness and elasto plastic performances. In the calculation an interfacial layer with given thickness is introduced into the single fiber model. It is shown that, for a soft interface, the variation in interfacial properties influences the stress transfer greatly.

中高速条件下不同翼尖小翼的数值模拟分析

为研究不同翼尖小翼的减阻特性,选取4种翼尖小翼和翼尖延伸作为研究对象,在相同展长翼尖与中高速飞行条件下(Ma=0.6),利用k-ω剪切应力运输(SST,shear stress transfer)两方程模型对5种不同翼尖装置进行数值模拟。研究5种翼尖装置情况下机翼表面的压力特征和翼尖流场,对比分析了不同翼尖的减阻特性,并对诱导阻力变化原理进行了分析。研究结果表明:不同翼尖小翼气流引导方向不同,改变了机翼表面流场,影响了翼尖压力分布;在中高速条件下,相同展长的融合式和斜削式翼尖小翼相比翼尖延伸减阻效果明显,双羽式翼尖小翼能有效分散翼尖涡。

A STUDY OF INTERFACES OF COMPOSITES BY MEANS OF OPTICAL FIBRE SENSING TECHNTIQUE

Fibre stress of glass fibre reinforced polymeric copmosites on load is determined by using optical fibre as model fiber and by means of laser interference method. In addition, the origination of fibre stress during moulding process of composites and the relation between fiber stress of loaded composites and external stress are examined. The experiments show that fibre stress is related to molecular structure of inter facial materials and structure of inter facial layers. When stress is transferred from matrix to fibre, each inter facial layer has different stress gradient and deformability. This property can be characterized by introducing an inter facial stress transfer coefficient k to the two-phase model.

Source of the 2019 M_(W)6.9 Banten Intraslab earthquake modelled with GPS data inversion

The 2019 M_(W)6.9 Banten Intraslab earthquake occurred at~100 km to the northeast of the Sunda Trench with two nodal plane models estimated by the Global Centroid-Moment-Tensor(GCMT)Project with a strike of 200°and a dip of 65°.Continuous GPS data from 11 GPS sites were used to model the source of the earthquake in three-components.The coseismic displacements and its uncertainties are obtained from the coordinates of these GPS sites from 7 days before to 7 days after the earthquake.The coseismic slip is the inversion result of those displacements based on the best fit in an elastic half-space.The maximum displacement is~5 cm with a large uncertainty that is comparable to the amplitude of displacement.A seismic moment of the best model(strike of 65°and dip of 54°)is 2.79×10^(19) Nm or equivalent to M_(W)6.89.The fault model of the earthquake is highly presumed as a continuation of Sumatran Fault Zone.

CONCEPTS OF MECHANICAL PARAMETERS TRANSFER IN SOLID MEDIUM AND ITS APPLICATION IN ENGINEERINGS

Based on investigation into four aspects of qualitative mechanical analysis, principle model experiments, engineering dynamic load tests and numerical calculation, it was discussed that the transfer of stresses and accelerations in stratum medium have a close relation with its relative rigidity. The concepts of stresses and accelerations transfer in solid medium and its corresponding generalized, composite structure system are presented. The survivability of underground engineerings and protective engineering will be greatly increased if these concepts are correctly used in construction.

Analysis on the Bonding Failure Mechanism of High Modulus Carbon Fiber Composites

In order to explore the bonding failure mechanism of high modulus carbon fiber composite materials,the tensile experiment and finite element numerical simulation for single-lap and bevel-lap joints of unidirectional laminates are carried out,and the stress distributions,the failure modes,and the damage contours are analyzed. The analysis shows that the main reason for the failure of the single-lap joint is that the stress concentration of the ply adjacent to the adhesive layer is serious owing to the modulus difference,and the stress cannot be effectively transmitted along the thickness direction of the laminate. When the tensile stress of the ply exceeds its ultimate strength in the loading process,the surface fiber will fail. Compared with the single-lap joint,the bevel-lap joint optimizes the stress transfer path along the thickness direction,allows each layer of the laminate to share the load,avoids the stress concentration of the surface layer,and improves the bearing capacity of the bevel-lap joint. The improved bearing capacity of the bevellap joint is twice as much as that of the single-lap joint. The research in this paper provides a new idea for the subsequent study of mechanical properties of adhesively bonded composite materials.

半球头体多孔逆向射流的减阻性能

采用基于shear stress transfer(SST)k-ω双方程湍流模型的数值方法研究了等面积多孔逆向射流对超声速来流条件下半球头体减阻性能的影响。基于等射流面积设计原则,在半球头体驻点附近进行多孔逆向射流喷注,通过改变射流总压比、射流孔数量,分析各变量对减阻性能的影响,并探讨多孔逆向射流间的相互影响。仿真发现:逆向射流能有效减小半球头体受到的阻力,随着总压比的增大,多孔逆向射流回流区增大,射流减阻性能提高;随着射流孔数的增多,射流减阻性能先提高再降低。在研究范围中,双孔逆向射流取得最优的减阻效果,其减阻比高达29%,双孔逆向射流间的相互影响是其取得良好减阻性能的关键。多孔逆向射流展现了取得优良减阻性能的可能性。

Investigation on the Effect of the Multilayered Porous Structure of Sea Urchin Skeleton on Its Mechanical Behavior

In this paper,the effect of stereom structure on the mechanical behavior of the Sea Urchin Inorganic Skeleton(SUIS)has been studied.The stereom microstructure of both Anthocidaris crassispina and Tripnenstes gratilla was characterized by Scanning Electron Microscopy(SEM).Results indicate that a three-layer porous structure consisting of a growth,a support,and a resorption(GSR)layer is a common denominator for both species.The effect of GSR layer order on the mechanical behavior of the SUIS was studied by a finite element method.The results show that the GSR model could effectively reduce the maximum tensile stress on its meridional sutures under unidirectional pressure,hydrostatic pressure,and self-weight situation.For a fabricated three-layered ceramic test strips with different layer orders,the mechanical properties have a completely opposite performance compared with the compressive properties of the calculated SUIS-Iike models.This indicates that the GSR structure can effectively improve the mechanical properties of the SUIS,but it cannot be applied to bionics without considering its synergistic effect with the macro-structure of the SUIS.This is a typical example of bionic invalidation by single structure,where multi-level structure bionics may be an effective solution.

Performance of fixed beam without interacting bars

Increasing the bending capacity of reinforced concrete(RC)elements is one of important topics in structure engineering.The goal of this study is to develop a transferred stress system(TSS)on longitudinal reinforcement bars for increasing the bending capacity of RC frames.The study is divided into two parts,i.e.,experimental tests and nonlinear FE analysis.The experiments were carried out to determine the load-deflection curves and crack patterns of the ordinary and TSS fixed frame.The FE models were developed for simulating the fixed frames.The obtained load-deflection results and the observed cracks from the FE analysis and experimental tests are compared to evaluate the validation of the FE nonlinear models.Based on the validated FE models,the stress distribution on the ordinary and TSS bars were evaluated.We found the load carrying capacity and ductility of TSS fixed beam are 29.39%and 23.69%higher compared to those of the ordinary fixed beams.The crack expansion occurs on the ordinary fixed beam,although there are several crack openings at mid-span of the TSS fixed beam.The crack distribution was changed in the TSS fixed frame.The TSS fixed beam is proposed to employ in RC frame instead of ordinary RC beam for improving the performance of RC frame.