Twin-shear Strength Criterion Research Articles

Tensile behaviour of transverse reinforcement with different connection methods in single steel-plate concrete composite structures

Transverse reinforcement is key to the single steel-plate concrete composite (SSC) structure when subjected to out-of-plane shear and impact load. This research focuses on the tensile behaviour of two connection methods between transverse reinforcement and steel plate in SSC structure, namely the tie bar interlocked with the J-hook connector (TBIJC) and the tie bar overlapped with the headed stud (TBOHS), which are much more convenient in construction compared to direct welding connection. Pull-out tests are carried out on 10 groups of specimens with different detail parameters to verify their reliable performance. Various types of failure modes and corresponding experimental phenomena are observed and recorded. The interfacial slip between the tie bar and concrete was measured to reflect the load–deflection characteristics. Parametric studies are carried out on the tensile performance considering connector shape and dimensions, end-anchor form of the tie bar and concrete strength. Plastic limit analysis is performed based on twin shear strength criterion for concrete, and an analytical model is developed to predict the ultimate tensile resistance. The accuracy of the proposed model is validated against the test results. Finally, based on the test results, design suggestions are proposed for the tie bar connection details considering both mechanical performance and construction efficiency.

The Analysis of Anchoring Mechanism of Rock Slope in Two Layers Based on the Nonlinear Twin-Shear Strength Criterion

The nonlinear strength criterion is introduced into the paper firstly, and then the geometric anchoring characteristic model of rock slope separated from two layers according to rock type with the fracture surface of log-spiral curve considering nonlinear twin-shear criterion subjected to seismic loads is established. Finally, some correlated influential parameters are analyzed, and the conclusions are drawn, showing that the intermediate principal stress has great influence on the total anchoring force of bolt P, so when different criteria are selected, the influence of intermediate principal stress should not be omitted. The effects of thickness ratio h1/h2 on total anchoring force increase gradually with the increase of inclination angle ϕ . The total anchoring force P decreases gradually with the increase of inclination angle ϕ and surcharge load q. The total anchoring force increases gradually with the increase of horizontal seismic acceleration coefficients kh and geometric coefficients mi and GSI.

Elastoplastic Assessment of Limiting Internal Pressure in Thick-Walled Cylinders with Different Tension-Compressive Response

Elastoplastic calculation and stress distributions of limiting internal pressure in thick-walled cylinders are examined based on the twin-shear strength criterion. The calculations are especially versatile for quantitative evaluating the intermediate principal stress, different tensile-compression strength, and tension-compression modulus. The calculation results are verified by comparing with other data taken form the literature. Parametric studies were carried out to assess the influence of the strength parameter, radius ratio, tensile-compression strength ratio and tension-compression modulus. The proper choice of determining parameters is shown to be vital for the design of such components. It makes full use of the strength potentialities for thick-walled cylinders due to considering the intermediate principal stress. Limiting internal pressure variations with the radius ratio provide reference for selecting a reasonable wall thickness. The calculations have an important practical value for the optimum design and engineering application of thick-walled cylinders.

3D numerical simulation of initiation, propagation and coalescence of cracks using the extended non-ordinary state-based peridynamics

An extended non-ordinary state-based peridynamics is proposed to investigate the initiation, propagation and coalescence of 3D pre-existing flaws in PMMA specimen subjected to uniaxial compressive loads. The maximum principal stress criterion and twin-shear strength criterion are introduced to the extended non-ordinary state-based peridynamics. A program code is compiled to demonstrate the validity of the extended non-ordinary state-based peridynamics. In the present study, the numerical specimens of PMMA containing different types of three-dimensional pre-existing flaws under uniaxial compression are simulated to prove the ability of the proposed numerical method to model the propagation and coalescence of 3D cracks. The axial stress versus axial strain curves are obtained using the proposed numerical method as well as the ultimate failure mode and crack coalescence process. The present numerical results are in good agreement with the previous experimental data.

Mechanism-based strength criterion for 3D needled C/C–SiC composites under in-plane biaxial compression

ABSTRACTBiaxial compressive experiments for 3D needled C/C–SiC composites parallel to the nonwoven cloth were conducted. The failure mechanisms and mechanical properties of the composites were greatly related to the biaxial compressive stress confinement ratio, R. It was found that out-of-plane shear failure controlled the failure of the composites. The failure shear plane was aligned with one of the major loading axes for R (0:1 or 1:3), while the failure shear plane occurred along both loading axes for R (1:2 or 1:1). Compared with uniaxial strength, the biaxial compressive strength increased obviously, which also significantly depended on the value of R. Based on the failure modes, a modified twin-shear strength criterion was established to predict the failure surface of 3D needled C/C–SiC composites under biaxial compressive loading.

Seismic bearing capacity of shallow foundations resting on rock masses subjected to seismic loads

This paper analyzes the bearing capacity of shallow foundations resting on rock masses subjected to seismic loads based on limit analysis theory. The non-linear twin shear strength criterion is used to consider the effects of intermediate principal stress on the bearing capacity of shallow foundations. The pseudo-dynamic approach is applied to account for the effects of seismic loads on the bearing capacity of shallow foundations. Both the horizontal and vertical seismic acceleration coefficients and the effects of an amplification factor on the upper bound evaluations of the foundation's bearing capacity are investigated. The ?-functions are then applied to derive the upper bound solution of the load-bearing capacity. A numerical computation is performed and indicates that the seismic acceleration coefficients, amplification factor and the intermediate principal stress parameter significantly affect the bearing capacity of shallow foundations.

Non-Linear FEM Analysis for the Layered Rock-Mass Tunnel Based on the Twin Shear Strength Criterion

According to the geotechnical conditions, A FEM model has been established to analyse the mechanical characteristics of the highway tunnel in the layered rock mass. In this model the layered rock mass and the soften joint are simulated by the transversal isotropic material, the interfaces between layers are simulated by the element of rotational Goodman interface, but the interface between the lining structure and surrounding mass is proposed to simulate by an interface element with thickness, and the supporting of tunnel is simulated by the straight beam element. In the meantime, based on the twin shear strength criterion, the mechanical characteristics of rock, the stiff matrix of element for the layered rock mass, soften joint and interface have been discussed. The analytical model has been demonstrated by comparing the results of layered surrounding rock-mass FEM with the test data in situ.

The effect of the intermediate principal stress on the ultimate bearing capacity of a foundation on rock masses

In this paper, the strength envelope of rock masses is considered to follow a non-linear unified strength criterion that considers the effect of the intermediate principal stress. A unified slip line method for resolving the differential equation system that governs the stress field is established to research the ultimate bearing capacity, which can be adapted for a wide variety of rock masses. Through this new theory, a suitable characteristic method for rock masses of interest can be obtained, and the relationships between different types of characteristic methods are revealed. The characteristic methods are based on different strength criteria, such as the Hoek–Brown criterion, modified Hoek–Brown criterion, or non-linear twin-shear strength criterion; each of these criteria is a special case of the proposed theory. Moreover, a series of new characteristic methods can be easily derived from it. In terms of the proposed theory, the ultimate bearing capacity with the Hoek–Brown criterion forms the lower bound; the ultimate bearing capacity with a non-linear twin-shear strength criterion forms the upper bound; and a series of the ultimate bearing capacities ranging between these two bounds may be derived from a non-linear unified strength criterion. A comparison is made between existing numerical analyses and non-linear finite element analysis solutions with the Drucker–Prager strength criterion. It is shown that the present results are in good agreement with existing numerical analyses and non-linear finite element analysis solutions with the Drucker–Prager strength criterion.

Finite Element Analysis of Dongjusi Railway Tunnel within Hard Rock Mass Based on the Unified Rock Mass Strength Criterion

The twin shear strength criterion has been proposed to consider the intermediate principal stress effect on the rock mass strength. The unified rock mass strength criterion could consider the intermediate principal stress effect on the rock mass strength. The unified rock mass elasto-plastic material model is implemented in ABAQUS user interface. As a case for study, the stability analysis of Dongjusi railway tunnel within hard rock mass is studied using the unified rock mass strength material. For comparison, the Hoek-Brown empirical strength criterion is also chosen for the rock mass material modeling. The computation results show that the plastic zone calculated using the unified rock mass strength criterion is smaller than that using the Hoek-Brown empirical strength criterion. The railway tunnel lining structure is designed according to the unified rock mass strength criterion and greatly makes use of the rock mass potential strength, which decreases engineering cost.

Unified Solutions to the Limit Load of Thick-Walled Vessels

Unified solutions to the elastoplastic limit load of thick-walled cylindrical and spherical vessels under internal pressure are obtained in terms of the unified strength theory (UST) and the unified slip-line field theory (USLFT). The UST and the USLFT include or approximate an existing strength criterion or slip-line field theory by adopting a parameter b, which varies from 0 to 1. The theories can be used on pressure-sensitive materials, which have the strength difference (SD) effect. The solutions, based on the Tresca criterion, the von Mises criterion, the Mohr–Coulomb criterion, and the twin shear strength criterion, are special cases of the present unified solutions. The results based on the Mohr–Coulomb criterion (b=0) give the lower bound of the plastic limit load, while those according to the twin shear strength criterion (b=1) are the upper bound. The solution of the von Mises criterion is approximated by the linear function of the UST with a specific parameter (b≈0.5). Plastic limit solutions with respect to different yield criteria are illustrated and compared. The influences of the yield criterion as well as the ratio of the tensile strength to the compressive strength on the plastic limit loads are discussed.

A Unified Strength criterion for rock material

A non-linear Unified Strength criterion for rock material is presented. It is the development of the Unified Strength Theory (in: M. Jono, T. Inoue (Eds.), Mechanical Behaviour of Materials-VI (ICM-6), Pergamon, Oxford, 1991, pp. 841–846) and the modification of the Hoek–Brown strength criterion (Underground Excavations in Rock, The Institution of Mining and Metallurgy , London, 1980). The effect of intermediate principal stress on rock strength is considered in the non-linear Unified Strength criterion. The Hoek–Brown criterion is a single-shear strength criterion that forms the lower bound, and the non-linear twin-shear strength criterion forms the upper bound in the deviatoric plane . All the failure criteria ranging from the Hoek–Brown criterion (lower bound) and the non-linear twin-shear criterion (upper bound) and a series of criteria ranging between these two bounds may be introduced by the non-linear Unified Strength criterion. The theory can also be generalized to rock mass strength .