Mechanical Failure Criteria Research Articles

Characterising mechanical properties and failure criteria of steel slag aggregate concrete under multiaxial stress states

To advance the application of steel slag aggregate concrete (SAC) in civil engineering, this study introduces a comprehensive experimental program to explore the failure mode, strength, deformation, and failure criteria of SAC under multiaxial stress conditions. In this investigation, SAC specimens containing 50% stabilised steel slag as a coarse aggregate were examined for mechanical behaviour (e.g. stress–strain relationships) under diverse loading scenarios, including uniaxial tensile and compressive loadings, biaxial compression, and true triaxial compression loadings. Subsequently, three distinct failure criteria (i.e. the Ottosen criterion [1], William–Warnke criterion [2], and Guo criterion [3]) for SAC were formulated and authenticated based on the experimental outcomes. The results showed varied failure modes in the SAC, such as prism type, splitting tensile, sheet-like tensile, and oblique shear, which depended on the stress state of the specimen during failure. A significant elevation in the ultimate strength and deformation of SAC specimens was observed, with an increment in the first-to-third principal stress ratio (σ1/σ3). Furthermore, the failure criterion introduced by Guo was validated as adept at reproducing all geometric characteristics of the concrete failure surface and precisely forecasting SAC’s ultimate strength of the SAC. Overall, this investigation proposed a reliable failure criterion based on true triaxial test data that can not only describe the multiaxial strength characteristics of SAC but also provide design advice for the applications of SAC in engineering structures.

Assessment of mechanical behavior and failure criteria under varied confining pressures in treated calcareous sand

Ensuring project safety for maritime geotechnical structures primarily composed of calcareous sand is crucial. Cement-based reinforcement is a promising strategy to enhance integrity and deformability, especially for overlying infrastructures in high-pressure ocean engineering. Firstly, the specimens are created by blending Portland cement and Gypsum into calcareous sand at contents of 16% and 22% and then subjected to curing periods of 7 and 3 days to explore their resistance to loading. Secondly, a triaxial consolidated drained test is conducted, applying different confining pressures ranging from 100 to 1200 kPa. This test aims to assess the mechanical behavior, strength parameters, failure criteria, and stress dilatancy behaviors of treated specimen. The results illustrating the peak shear strength points of all treated specimens display a concave nonlinear shape sloping downwards. An equation is presented to modify the mean effective stress and accommodate the influence of bonding strength. Finally, A revised criterion is formulated by integrating this equation into the failure criterion. Significantly, this refined failure criterion accurately defines the failure envelopes. An equation was established to reveal the relationship between the brittleness index and confining pressure. Additionally, two stress ratio parameters are defined based on the brittleness index to describe bonding degradation comprehensively.

Compression-shear performance of steel fiber reinforced rubber concrete

Rubber powder can be produced from waste tires through processing and its inclusion in concrete, either with steel fiber or alone, has been shown to improve impact and shear toughness and reduce environmental pollution. However, the mechanical behaviors and failure criteria of steel fiber reinforced rubber concrete (SFRRC) under combined compression-shear loading, which is essential for structural application, is lacking. This study investigates the compression-shear properties of SFRRC, considering steel fiber and rubber powder content, and compressive stress ratio. The effects of these parameters on shear strength, shear peak displacement, and shear toughness were analyzed. Results indicate that as the compressive stress ratio increases, SFRRC's failure pattern changes from tensile failure to compression-shear failure when k ≥ 0.4, exhibiting ductile failure. The equivalent initial energy density increases with rubber powder content, while equivalent shear residual toughness increases after the peak value, but shear strength and peak displacement decrease. With the addition of steel fiber, initial shear strength, peak displacement, and equivalent residual strength increase. A calculation criterion for compression-shear strength was proposed, with theoretical values matching well with experimental values.

Triaxial compression failure criterion and constitutive relation of concrete containing multiple solid wastes

This study analyzed the mechanical properties and failure criterion of full-solid waste concrete (SCT) made with slag, fly ash, carbide slag, soda residue, and iron tailings aggregate. SCT showed a higher strength growth rate (25.5–57.7%) compared to natural sand and gravel as aggregate (SCN) (20.7–47.5%), but lower than cement + natural sand and gravel (PCN) (32.0–86.1%), due to the latter's susceptibility to microcracks. The study proposed a parabolic pressure meridian failure criterion equation and an improved power function formulation of the Mohr-Coulomb failure criterion for SCT. The findings suggest that SCT can be used in engineering applications.

3D printed concrete with recycled sand: Pore structures and triaxial compression properties

The mechanical properties and failure criteria of 3D printed concrete under triaxial compression are the basis of calculations for structural design. Incorporating recycled sand into 3D printed concrete can promote early structural formation and has significant environmental benefits. In this study, the pore structures of 3D printed recycled mortar (3DPRM) were characterized by MIP and X-CT tests. The triaxial mechanical properties in the Z-direction were measured at confining pressures of 0, 5, 10, and 15 MPa. The results showed that the incorporation of recycled sand increased the porosity and pore diameter of 3DPRM specimens in various diameter ranges but did not significantly change the sphericity and orientation of the pores. The crack development direction of 3DPRM specimens under triaxial compression depended on both the principal stress direction and the pore structure. The confining pressure increased the strength and compressive toughness of the 3DPRM specimens, and the sensitivity of the 3DPRM specimens to the confining pressure increased with increasing replacement rate. By analyzing the influence mechanism of recycled sand incorporation on 3DPRM strength, a dual deterioration hypothesis based on the pore structure and interface transition zone of 3DPRM was proposed, and the corresponding strength model was established.

Investigation on mechanical properties and failure criterion of multi-recycled aggregate concrete under triaxial compression

This paper presents a pioneering experimental investigation on the effects of lateral confining pressure and recycling cycles on the mechanical properties of natural aggregate concrete (NAC) and 3 generations of multi-recycled concrete (Multi-RAC) subjected to triaxial compression. The results indicate that both lateral confining pressure and recycling cycles have a significant influence on the triaxial mechanical characteristics of Multi-RAC specimens. The peak stress and peak strain increase with the increase of lateral confining pressure. Although the strength of Multi-RAC is inferior to NAC, the 2nd and 3rd generations present a relatively smaller downward trend compared to the 1st generation. The deformation ability of Multi-RAC is larger than NAC, especially for the 1st and 2nd generations. The elastic modulus of the 1st and 2nd generations are smaller than the counterparts of NAC and the 3rd generation. Based on experimental data, a failure criterion is proposed for Multi-RAC with proper consideration of the effects of the lateral confining ratio and the number of recycling cycles. The related outcomes are expected to provide the reference for safe engineering design and facilitate the structural application of Multi-RAC.

Mechanical properties of multi-recycled aggregate concrete under combined compression-shear loading

The mechanical properties and strength failure criteria of multi-recycled aggregate concrete (multi-RAC) under combined compression and shear loading states are investigated in this paper. The peak shear strength, peak shear displacement, and failure patterns are compared under different regeneration cycles and normal compressive stress ratios. The results reveal that both the peak shear strength and peak shear displacement increase with the increased normal stress ratio. The shear failure pattern with higher severity corresponds to more spalling powder and debris deposited on the shear fracture surface. When the regeneration cycles of coarse aggregate increase, the peak shear strength decreases and the descending trend become more evident with the higher vertical compressive stress ratio. Under the normal compressive stress, contact friction strength is the dominant component of peak shear strength among the cohesive strength, contact friction strength, and shear dilation strength. Based on different stress expressions, three compression-shear failure criterion models considering the regeneration cycles of coarse aggregate under planar stress state were established for RAC. The stress invariance failure criterion model and octahedral stress failure criterion model in quadratic parabolic functional form can provide high prediction accuracies.

Mechanical properties and failure criteria of coral concrete under true triaxial compression

Mechanical properties and failure criteria of coral concrete under true triaxial compression

Compression-shear performance and failure criteria of seawater sea-sand engineered cementitious composites with polyethylene fibers

• Tests on the compression-shear performance of seawater sea-sand ECC were performed. • Seawater sea-sand ECC under the combined loading shows ductility failure mode and high shear strength. • Failure law is reflected by the criterion based on octahedral stress or stress invariant. • The failure criterion of seawater sea-sand ECC could be applied in future structural analysis. Seawater sea-sand engineered cementitious composites (SS-ECC) with polyethylene (PE) fibers holds wide application prospects. However, the understanding on its mechanical behaviors and failure criteria under combined compression-shear loading, which is essential for structural application, is lacking. The object of this research is to obtain the mechanical performance and establish the corresponding failure criteria of SS-ECC under combined loading. The influences of fiber content and normal stress ratio on failure modes, shear strength, peak shear displacement and shear strength components were analyzed. SS-ECC under combined loading exhibited ductile failure mode. Shear strength increased significantly with the increasing normal stress ratio, while increased slightly with higher fiber content. The effects of fiber content and normal stress ratio on the combined compression-shear behaviors were clarified. Further, the failure criteria based on octahedral stress and stress invariant were proposed for describing the failure law of SS-ECC under combined loading. This research lays the groundwork for understanding the mechanical performance of SS-ECC under combined compression-shear loading and preparing its application in structural members.

Mechanical Properties, Constitutive Behaviors and Failure Criteria of Al-PTFE-W Reactive Materials with Broad Density.

Quasi-static tension tests, quasi-static compression tests and dynamic compression tests were conducted to investigate the mechanical properties, constitutive behaviors and failure criteria of aluminum-polytetrafluoroethylene-tungsten (Al-PTFE-W) reactive materials with W content from 20% to 80%. The analysis of the quasi-static test results indicated that the strength of the materials may be independent of the stress state and W content. However, the compression plasticity of the materials is significantly superior to its tension plasticity. W content has no obvious influence on the compression plasticity, while tension plasticity is extremely sensitive to W content. Dynamic compression test results demonstrated the strain rate strengthening effect and the thermal softening effect of the materials, yet the dynamic compression strengths and the strain rate sensitivities of the materials with different W content show no obvious difference. Based on the experimental results and numerical iteration, the Johnson–Cook constitutive (A, B, n, C and m) and failure parameters (D1~D5) were well determined. The research results will be useful for the numerical studies, design and application of reactive materials.

Mechanical behaviors and failure criteria of seawater sea-sand engineered cementitious composites under combined tension and shear

Seawater sea-sand engineered cementitious composites (SS-ECC) is promising for alleviating both the shortage of freshwater and river sand and the brittleness caused by replacing steel bars with fiber reinforced plastic/polymer (FRP) bars. However, the mechanical properties of SS-ECC at complicated stress state are not systemically investigated, and the corresponding failure criteria are not established. This study experimentally investigated the mechanical properties of SS-ECC under various combined tension-shear loads by a specially designed test fixture. The results showed that SS-ECC under combined tension and shear presents multiple cracking and micro-cracks with the crack width of no more than 0.24 mm. The load-displacement curves of SS-ECC are divided into elastic stage, steady cracking stage and failure stage. When loading angle increases from 10° to 70°, crack number and maximum resultant force decrease due to increasing number of fiber rupture. Compared with control group, SS-ECC under combined tension and shear exhibits excellent strength and ductility. Finally, through analysis based on the generalized twin shear stress strength theory, the failure law of SS-ECC under the combined loading is well described.

Experimental investigation of dynamic shear mechanical properties and failure criterion of ice at high strain rates

The failure of ice is dominated by shear failure mode at certain specific stress states. The dynamic shear mechanical properties of ice are investigated using reinforced hat-shaped specimens and SHPB experiments at shear strain rates ranging from 17,000 /s to 61,000 /s. The experimental results show that the mechanical properties of ice on dynamic shear are sensitive to shear strain rate. And the relationship between dynamic shear strengths and shear strain rates is linear. The Mohr-Coulomb criterion is employed to determine the failure of ice at complex stress states. The internal friction angle of the Mohr-Coulomb criterion for ice is a constant (34.31°) which is insensitive to the shear strain rate, but the cohesion of the Mohr-Coulomb criterion for ice is sensitive to the shear strain rate. These results could provide experimental technique and theoretical basis for improving the dynamic constitutive model of ice to describe the integrated failure mode of ice with complex stress states accurately.

Determination of Mohr–Coulomb failure envelope, mechanical properties and UPV of commercial cement-lime mortar

Mortar in masonry structures can be subjected to both uniaxial and triaxial loading. Determining the mechanical properties and/or failure criteria of the commonly used mortar is necessary for the structural performance assessment of new and existing masonry buildings using non-destructive testing and/or finite element modelling methods. In this paper, the stress–strain behaviour of a commercially available cement-lime mortar is investigated under uniaxial and triaxial loading. The axial compressive strength, modulus of elasticity, Mohr–Coulomb failure envelopes of the mortar are determined over a range of conditions. Mortar specimens were prepared with a water to cementitious material ratio (w/cm) of 0.6–0.7 and were tested at curing ages of 3, 7, 14, and 28 days, under confining pressures of 0, 100, 250, 500 and 750 kPa. Ultrasonic pulse velocity (UPV) of the specimens were measured before the destructive testing. The results indicate that the influence of curing age and confining pressure on the axial compressive strength of the mortar can be predicted using proposed linear correlations between (i) The confining pressure and the axial compressive strength and (ii) The UPV and the axial compressive strength. From the test results, the strength parameters of the Mohr–Coulomb failure criterion were also determined. It is observed that cohesion is more sensitive to changes in curing age and w/cm than the friction angle, which varied between 32 and 33 degrees.

Modeling Approaches for the Assessment of Seismic Vulnerability of Masonry Structures: The E-PUSH Program

The assessment of seismic performance of existing masonry structures is a key aspect for the risk mitigation strategies of existing buildings and preservation of historical heritage. The increasing availability of modelling approaches for the assessment of seismic response of masonry structures calls for the need of verifying their reliability and correct use. In fact, these procedures are very sensitive to modelling hypotheses, so that the results of the assessment could vary in a wide interval depending on the adopted software and on the user’s skill. Aiming at enhancing the classical software packages for the structural analysis of masonry buildings, especially in terms of easiness of use, simplicity of modelling and limited computational demand, the authors developed a reliable and sound push-over program, called E-PUSH, which allows a quick and nearly user-independent assessment of the seismic risk index. In the paper, available commercial codes for the seismic assessment of unreinforced masonry buildings are illustrated and discussed, in comparison with the E-PUSH program, highlighting the differences in terms of modelling assumptions, choice of masonry mechanical parameters and failure criteria, focusing on the impact of the assumptions adopted for the estimation of capacity curves and seismic risk index of a simple benchmark structure. Then, a relevant case study, consisting in the assessment of the “Niccolò Machiavelli” masonry school in Florence, is investigated adopting two different software packages, the original E-PUSH and a commercial one, discussing the sensitivity of the results on the assumptions made by the user in the modelling phase.

Strength criterion of recycled aggregate concrete under triaxial Compression: Model calibration

Utilization of recycled aggregate concrete (RAC) can promote the development of green building materials since it can make full use of waste concrete. The mechanical properties and failure criterion of RAC under triaxial compression is the computational basis for design of RAC structural members. However, an explicit and unified approach for assessing the failure surface of RAC under both traditional triaxial compression and true triaxial compression condition is extremely limited. Aiming to provide a solution to figure out the above-mentioned technical bottleneck, firstly this study evaluated the applicability of existing failure criterion developed based on natural aggregate concrete using an experimental database including 123 cylindrical RAC specimens; and then an equation of compressive meridian (i.e., Lode angel is 60°) in octahedral stress space was proposed with the help of this database. Further, the formula for tensile meridian of RAC (i.e., Lode angel is 0°) was established based on 24 cubic RAC specimens collected from available literature. The influence of high temperature was also considered in both compressive meridian and tensile meridian formula. A complete failure surface of arbitrary stress condition (i.e., the Lode angle ranges from 0° to 60°) was determined. Finally, the proposed equations for failure surface of RAC in the cases of room temperature and high temperatures were validated with reference to experimental results.

Evaluation of the Mechanical Failure Criterion to Consider the Triple Base Propellant Safety Life: Application of Sustainable Renewables for Environmental Hazards

Implementation of clean energy and renewables is essential for the consideration of environmental impact because it can be implemented in supply chain networks and sustainable management procedures for safety. In order to study the safety life failure criterion of a triple base propellant under the failure mode of mechanical properties, an accelerated aging test, an evaluation method for the launch safety test of gun propellant charge, and a compressive strength test were used. The failure criterion of mechanical properties was obtained by researching the correlation between launch safety change and mechanical property change of samples. Berthelot’s equation was used to predict the safety life of the triple base propellant. The results show that the mechanical failure criterion is “27% reduction of maximum compressive strength.” The safety life at 25°C and 75% humidity is 13.77 years.

Analysis of Biaxial Mechanical Properties and Failure Criterion of Self-Compacting Concrete

Biaxial compression-compression, biaxial tension-compression and compression-shear tests were carried out on self-compacting concrete (SCC) using the rock true triaxial machine and compression-shear hydraulic servo machine to explore the biaxial mechanical properties of SCC. The failure modes and stress-strain curves of SCC under different loading conditions were obtained through experiment. Based on the comparison with the biaxial loading test data of ordinary concrete, the following conclusions are drawn: the failure modes and failure mechanisms under biaxial compression-compression and biaxial tension-compression are similar between SCC and ordinary concrete. Under compression-shear loading, the oblique cracks formed on the lateral surface of the specimen parallel to the shear direction gradually increased and the friction marks on the shear failure section were gradually deepened with the increase of axial compression ratio. The development trend of the stress-strain curve in the principal stress direction was not related to the lateral stress. Under the influence of lateral compressive stress, the principal compressive stress of SCC was increased by 55.78% on average; under biaxial tension-compression, the principal tensile stress of SCC had a maximum reduction of 62.79%; and under the compression-shear action, the shear stress of SCC had a maximum increase of 3.35 times. Compared with the biaxial stress test data of ordinary concrete, it can be seen that the lateral compressive stress had a more significant effect on the principal stress of SCC under biaxial loading. Subsequently, the strength criterion equations of SCC under biaxial loading were proposed based on the principal stress space and octahedral space stress respectively, which have shown good applicability in practice.

Optical method for identification and quantification of full-field stress distributions and evolution in assembled lining structures based on additively printed models and phase-shifting methods

The accurate knowledge and characterization of the full-field stress distributions and evolution in assembled lining structures underlie the design, construction, and maintenance of tunnel linings. However, it is challenging for traditional field monitoring and laboratory experiments to identify directly and quantify accurately such distributions and evolution. Numerical simulations, as alternative solutions, are limited, as their results are significantly dependent on the accuracy of mechanical parameters, constitutive laws, failure criteria, mesh optimization, and boundary conditions, which are difficult to determine experimentally. In this study, a plane-stress-model-based photoelastic testing method was developed for the direct observation and quantification of the full-field stress distribution and evolution in an assembled lining structure based on additive manufacturing or three-dimensional printing technology and phase shifting methods. Three-dimensional printing techniques and stress- sensitive photopolymers were employed to fabricate transparent assembled models based on the information of real lining structures. The model split-merge technique, phase-shifting method, and unwrapping algorithm were combined to determine the full-field distribution of the principal stress difference and shear stress within the assembled segments. The proposed method was verified based on a comparison of the calculated and measured fringe orders at different loading stages. The experimental results indicated that the largest stress concentration was around the joint that connected the adjacent Segment L1 and basic Segment B1, which formed the potential critical failure zone of the assembled structure. An approximate X-shaped shear band was also identified. Comparisons of the results verified that the boundary and contact conditions, which are difficult to simulate, can lead to significantly different simulation results with respect to the distribution and evolution of the principal stress difference and shear stress. This study shows that the proposed method can effectively and quantitatively characterize the full-field stress distributions and evolution within complex assembled lining structures.

Modelling adhesively-bonded T-joints by a meshless method

Bonding of non-parallel substrates has many applications in the transport industry. Adhesively-bonded T-joints are employed for that purpose. However, geometrical dimensions, substrates’ shape and material choices are broad. The effect that varying upper substrate thickness has on the joint strength (P max ) was investigated in this work through numerical analyses. The numerical analysis was performed using a meshless method, the natural neighbour radial point interpolation method (NNRPIM), which has been proven accurate and robust in another adhesive joint configuration. Materials were considered elastic-plastic. A yield criterion developed for rubber-like materials, the Exponent Drucker-Prager, was used for the adhesive layer, while the metallic substrates were analysed with the von Mises yield criterion. P max was determined numerically using a strain-based continuum mechanics failure criterion. Normalised peel and shear stress distributions along the bond-line are presented. Effective strains, both elastic and plastic, were also obtained. The estimated P max was compared with experimental data; a good agreement was found. The stress distribution along the bond line becomes asymmetric in joints with unbalanced substrate thicknesses. At P max , from 10 to 25% of the bond-line has entered into plastic regime. The results indicate that the proposed methodology is suitable to analyse adhesively-bonded joints under different load solicitations.

Mechanical performance and failure criterion of coral concrete under combined compression-shear stresses

The mechanical performance of coral concrete under combined compression-shear stresses was investigated using the multifunctional true triaxial testing machine. The shear load–displacement curves, normal displacement-shear displacement curves, and shear failure modes were obtained. Based on the test results, the shear failure modes, deformation proprieties, peak shear strength, and shear strength components were analyzed. The results show that almost all coral aggregates on the shear failure surface are broken. With the normal stress ratio increasing, the fiction traces and tiny concrete debris on the shear failure surface increase, and the peak shear strength and corresponding shear displacement also increase. The shear strength components include cohesion strength, contact friction strength, and shear dilation strength, where the contact friction strength dominates the shear strength with the existence of normal stress. Based on different stress expressions, five failure criterion models are proposed, where the one based on stress invariant achieves the highest prediction accuracy.