Mechanical Failure Modes Research Articles

Uniaxial Compression Failure and Size Effect of Recycled Aggregate Concrete Based on Meso-Simulation Analysis.

Recycled aggregate concrete (RAC) is a kind of five-phase composite material at the meso-level. It has a more complex interfacial transition zone (ITZ) than ordinary aggregate concrete (NAC), which is an important factor affecting the meso-failure of RAC. In addition, the maximum aggregate size plays an important role in the nonlinear mechanical behavior of concrete, which is closely related to the size effect. In this paper, a 2D random aggregate model of RAC is established based on meso-mechanics. The mechanical properties and failure modes of RAC under uniaxial compression are simulated using a plastic damage constitutive model. Through variable parameter analysis, the effects of the properties and thickness of ITZ on the elastic modulus and peak stress of RAC are studied, and the effect of the maximum aggregate size on the size effect of the compressive strength of RAC is discussed. The results show that the ITZ strength has a positive linear correlation with the peak stress and elastic modulus of RAC, while the ITZ thickness has a negative linear correlation with the peak stress and elastic modulus of RAC. Under the same specimen size (D = 100 mm, 150 mm, 200 mm, 300 mm), with an increase in the maximum aggregate size (dmax =20 mm, 25 mm, 30 mm, 35 mm), the nominal compressive strength of RAC increases by 6–10%, and the size effect is gradually weakened. When the maximum aggregate size reaches 30 mm, a decrease in the size effect tends to slow down compared with the maximum aggregate size of 20 mm. The classical Bažant size effect law is applicable to describe the compressive properties of RAC under different maximum aggregate sizes, and has a certain guiding significance for the prediction of the size effect of RAC in practical engineering.

Mechanical performance of additively manufactured cobalt-chromium-molybdenum auxetic meta-biomaterial bone scaffolds

Auxetic meta-biomaterials offer unconventional strain behaviour owing to their negative Poisson's ratio (−υ) leading to deformation modes and mechanical properties different to traditional cellular biomaterials. This can lead to favourable outcomes for load-bearing tissue engineering constructs such as bone scaffolds. Emerging early-stage studies have shown the potential of auxetic architecture in increasing cell proliferation and tissue reintegration owing to their −υ. However, research on the development of CoCrMo auxetic meta-biomaterials including bone scaffolds or implants is yet to be reported. In this regard, this paper proposes a potential framework for the development of auxetic meta-biomaterials that can be printed on demand while featuring porosity requirements suitable for load-bearing bone scaffolds. Overall, the performance of five CoCrMo auxetic meta-biomaterial scaffolds characterised under two scenarios for their potential to offer near-zero and high negative Poisson's ratio is demonstrated. Ashby's criterion followed by prototype testing was employed to evaluate the mechanical performance and failure modes of the auxetic meta-biomaterial scaffolds under uniaxial compression. The best performing scaffold architectures are identified through a multi-criteria decision-making procedure combining ‘analytic hierarchy process’ (AHP) and ‘technique for order of preference by similarity to ideal solution’ (TOPSIS). The results found the Poisson's ratio for the meta-biomaterial architectures to be in the range of −0.1 to −0.24 at a porosity range of 73–82%. It was found that the meta-biomaterial scaffold (AX1) that offered the highest auxeticity also showed the highest elastic modulus, yield, and ultimate strength of 1.66 GPa, 56 MPa and 158 MPa, respectively. The study demonstrates that the elastic modulus, yield stress, and Poisson's ratio of auxetic meta-biomaterials are primarily influenced by the underlying meta-cellular architecture followed by relative density offering a secondary influence.

Bio-inspired self-stitching discontinuous fiber reinforced composites with enhanced ductility and energy absorption

This paper innovatively proposed a biomimetic self-stitching carbon fiber reinforced polymer (CFRP) with a unique microstructure of inter-laminar overlapping region inspired by the overlapping feature of ironclad beetle and brick-and-mortar feature of nacre. To investigate the effectiveness of self-stitching microstructure, two baseline configurations of continuous unidirectional CFRP and discontinuous staggered CFRP were designed. Three-point bending tests showed that the self-stitching microstructure can significantly enhance the pseudo-ductility of CFRP composite by inhibiting crack propagation through additional fiber bridging. In addition, varying the overlap length can also result in different mechanical responses and failure modes. Compared to unidirectional CFRP, the self-stitching CFRP with a well-designed discontinuity at the ply level can improve failure strain and energy absorption by more than 228% and 85%, respectively.

CLOVER Robot: A Minimally Actuated Jumping Robotic Platform

Robots have been critical instruments to exploration of extreme environments by providing access to environments beyond human limitations. Jumping robot concepts are attractive solutions to negotiate complex and cluttered terrain. However, among the engineering challenges that need to be addressed to enable sustained operation of jumping robot concepts in extreme environments, the reduction of mechanical failure modes is one of the most fundamental. This study sets out to develop a jumping robot design, with a focus on a minimal actuation to support reduced mechanism maintenance and thus limit the number of mechanical failure modes. We present the synthesis of a Sarrus-style linkage to constrain the system to a single translational degree of freedom thus removing the need for synchronising gears, which exhibit high failure rates in dusty environments. We have restricted the present research to vertical solid jumps to assess the performance of the fundamental main-drive linkage. A laboratory demonstrator assists the transfer of theoretical concepts and approaches to practical implementation. The laboratory demonstrator performs jumps with 63% potential-to-kinetic energy conversion efficiency, with a theoretical maximum of 73%. Satisfactory operation opens up design optimisation and directional jump capability towards the development of a jumping robotic platform for extreme environments exploration.

Effects of material and piston diameter on the fatigue behavior, failure mode, and stress distribution of feldspathic ceramic simplified restorations

This study evaluated the influence of the piston material (glass fiber-reinforced epoxy resin or stainless steel) and the piston tip diameter (6 or 40 mm) on the fatigue mechanical behavior, failure mode, and stress distribution of feldspathic ceramic simplified restorations. Pistons were machined in glass fiber-reinforced epoxy resin (ER) and in stainless steel (SS), with active tips simulating the curvature radius of 6- or 40-mm diameter spheres. A total of sixty (N= 60) feldspathic ceramic discs (Ø= 10 mm; thickness= 1.0 mm) were adhesively luted onto supporting substrate discs (Ø= 10 mm; thickness= 2.5 mm) and allocated into 4 groups (n= 15) according to the piston used for fatigue testing: ER_6, ER_40, SS_6, SS_40. Afterwards, the specimens were submitted to the cyclic fatigue test (20 Hz frequency; initial load= 100 N; step= 50 N; 10,000 cycles/step, upon specimen failure detection). The collected data were analyzed by two-way ANOVA (α= 0.05) to verify differences by considering ‘piston material’ and ‘piston diameter’ as factors, and their association. In addition, a survival analysis (Kaplan Meier with Mantel-Cox log-rank post-hoc tests) was conducted (α= 0.05). Fractographic and finite element (FEA) analyzes were also performed. ‘Piston material’ (p= 0.040, F= 4.43) and ‘piston diameter’ (p < 0.000, F= 563.21) had a significant influence on the fatigue failure load (FFL) and the number of cycles for failure (CFF) values. Feldspathic restorations showed higher FFL and CFF (p < 0.05) when tested with a 40 mm diameter piston compared to a 6 mm diameter piston (ER_40 and SS_40 > ER_6 > SS_6). In relation to the piston material, ER and SS pistons with 40 mm diameter promoted similar fatigue performance (ER_40: 946.67 N/179,333 cycles = SS_40: 936.67 N/177,333 cycles), while 6 mm diameter groups presented different fatigue performance (ER_6: 440 N; 78,000 cycles > SS_6: 353.3 N; 60,667 cycles). Hertzian cone crack failures were only observed in the groups tested with 6 mm pistons, regardless of piston material. Higher stress concentration on the ceramic surface was observed when using 6 mm diameter pistons, whereas the SS_6 group showed a slight increase in stress concentration in comparison to the ER_6 group. The piston diameter showed an influence on the fatigue behavior, failure mode, and stress distribution of feldspathic ceramic simplified restorations. However, the influence of piston material is only observed when 6 mm diameter pistons are used. The 40 mm diameter pistons led to radial crack, being more appropriate for fatigue test of simplified feldspathic ceramic restorations with a thickness ≤ 1 mm. Whilst the 6 mm diameter pistons should be avoided, once tend to induce Hertzian cone crack failures and to underestimate fatigue performance.

Interfacial, tensile and bending properties of a novel wide-angle woven fabric/EPDM composite

Off-axis woven flexible composites have attracted attention because of its excellent deformability. However, the current traditional method is to cut orthogonal woven fabrics into the diagonal lines, in which the central axis of above-mentioned diagonal fabrics is consistent with the length of synchronous belt. Obviously, this technique is inefficient and costly. This paper presents the interfacial, tensile and bending properties of a novel wide-angle woven fabric/ethylene propylene diene monomer (EPDM) composites. 60°/120° wide-angle fabrics are prepared by an improved rapier loom. For comparisons, 0°/90° orthogonal fabrics are also braided. Then these two kinds of the fabric/EPDM composites are fabricated by a hot pressing mechanism. Subsequently, the interface, tensile and bending tests are carried out. The mechanical behaviors and failure mode are analyzed. The results show that the tensile strength and modulus of 60°/120° wide-angle fabric/EPDM composites are 11.11 MPa and 61.43 MPa, which are 22% (9.14 MPa) and 65% (37.04 MPa) higher than those of 0°/90° orthogonal fabric/EPDM composites, respectively. Moreover, the bending strength (5.86 MPa) of 0°/90° orthogonal fabric/EPDM composites is similar to that (6.62 MPa) of 60°/120° wide-angle fabric/EPDM composites, whereas the bending modulus (206.31 MPa) of the former is 30% lower than that (293.83 MPa) of the later ones.

Mechanical behaviors and failure modes of additive manufactured Ti6Al4V lattice structures under compressive load

The additive manufacturing technology facilitates the formation of complex lattice structures that are difficult to be fabricated by the traditional manufacturing technologies. In order to investigate the mechanical behaviors and failure modes of Ti6Al4V lattice structures manufactured by laser powder bed fusion (L-PBF), five cell topologies such as face centered cubic with vertical struts (FCCZ), body centered cubic with vertical struts (BCCZ), face and body centered cubic with vertical struts (FBCCZ), diamond and rhombic dodecahedron (RD) were chosen. The compressive tests were performed. The deformation behaviors and failure modes of these five kinds of lattice samples were studied and compared. And stress–strain curves, the compressive strength, the elastic modulus, the specific compressive strength, and the specific energy absorption were calculated and compared. It is shown that the FBCCZ sample has the best performance on the elastic modulus and the compressive strength among these five topologies. The specific compressive strength and the specific energy absorption of the FCCZ sample are the highest, which are 131% and 116% higher than those of the diamond sample respectively. It is also found that the shear failure is the main failure mode of the FCCZ, BCCZ, FBCCZ, and RD samples. While, the diamond sample collapses layer by layer from the bottom layer to the top layer. Finite element analysis was performed and the numerical results can explain the damage evolution of all samples.

Mechanical Behaviour of Magnesium Alloy Based - Fiber Metal Laminates after Fabrication Using Different Metal Surface Treatments

This paper presents an experimental investigation of the mechanical response and failure mode of magnesium alloy-based Fibre Metal Laminates (FMLs) having different surface pretreatments under axial compression loading conditions. To improve the interfacial bonding strength between the metal and composite layers, three categories of samples were fabricated by hot pressing using sandblasted, annealed and both sandblasted and annealed AZ31B magnesium alloy sheets. To evaluate the bonding strength along the shear and normal directions, single lap shear tests and T-peel tests were conducted. It was found that the combination of sandblasting and annealing can greatly enhance the shear and normal interfacial bonding strength compared with only sandblasting and annealing, separately. To assess the effect of the interfacial bonding strength on the FML compressive performance, quasi-static buckling tests were performed at varying surface treatments of the magnesium alloy sheets. The analysis of the load-stroke curves and failure modes indicates that delamination can significantly reduce the buckling capability and structural stability, and that the improvement of interfacial bonding strength can dramatically strengthen the FML compressive capability.

Research on uniaxial compression strength and failure properties of stratified rock mass

Stratified rock mass usually exists in sedimentary formation, composed of at least two lithological units with different mechanical properties, which may cause numerous disasters to engineering protection and construction. Investigation of mechanical properties and failure modes of stratified rock mass helps solve these problems. This study investigated the uniaxial compressive strength of stratified rock mass with different strength ratios of the original materials. The experimental results reveal the relationship between the strength difference of lithological units, the percentage of soft rock and uniaxial compressive strength in the soft and hard rocks alternate-layered rock mass. In addition, the failure modes were investigated by using simulated specimens under compressive loads. The experimental results indicate that the dip angles of the bedding plane and the mechanical properties of original materials in stratified rock can directly affect crack initiation and propagation behavior and eventually result in different failure modes. The crack distribution characteristics were also investigated in this study to provide more references to further decisions on the cracking problem.

Mechanical Behaviour and Failure Mode Analysis of Penetrated Mortise–Tenon Joint with Neighbouring Gaps Based on Full-Scale Experiments

The penetrated mortise–tenon joint (PMT) connecting column and beam in traditional timber structures often has neighbouring gaps between connected structural members due to initial manufacture errors and damage accumulated over years. Influences of the neighbouring gaps on the mechanical properties of the PMT joint have been analysed based on a full-scale experimental study. Four typical gap values are determined according to the probability analysis of on-site survey results of a Chinese traditional timber structure. Four full-scale models of PMT joints with varied gap values have been established. Failure modes and deformation characteristics have been studied by quasi-static tests. Results show that the failure modes are the tearing of wood fiber along the grain at variable cross-sections. The loose penetrated mortise–tenon (LPMT) joints all have high deformability. The slip distance of tenon grows as the gap value increases. Limit angles of the loose joints lag with the increasing degree of loosening. The bending bearing capacity and rotational stiffness of LPMT joints decrease as the gap value increases, and the limitation value of the gap is analysed. The resisting capacities of LJ-2, LJ-3 and LJ-4 are much lower than that of LJ-1. The changing ratios are 18.5%, 55.4% and 70.4%, respectively. A three-parameter power function model of the mortise–tenon joint with consideration of the neighboring gap is presented. Research results provide important references on the condition assessments of the existing traditional timber structures.

Mechanical properties and failure modes of CRCB specimen under impact loading

To explore the dynamic mechanical characteristics of CRCB specimens, a separated Hopkinson pressure bar (SHPB) test device combined with ultra-high-speed camera system was used to carry out the impact compression test on CRCB specimens. The stress wave propagation, dynamic stress–strain relationship, dynamic evolution of cracks, energy dissipation law and failure characteristics of the coal–rock combined body in the case of stress waves entering coal from rock were compared and analyzed. The influence of the difference between the rock and the incident bar on the propagation of stress wave gradually weakens with the increase of the impact velocity. The strength stress and peak strain of the CRCB specimens have obvious strain-rate effects. Besides, with increased impact velocity, the incident energy increases linearly, the reflected energy proportion decreases linearly and the absorbed energy proportion change approximately as a power function. Under the same stress wave, as the strength of the rock increases, the failure degree of coal gradually increases, the broken particles gradually transition from massive to powder and the rock mode changes from splitting failure to shear failure. As a result, the average particle size of broken coal blocks decreases, and the fractal dimension of CRCB specimens increases gradually. The research results provide basic research for the control of surrounding rock of roadway under dynamic pressure.

Micro-Mechanism of Uniaxial Compression Damage of Layered Cemented Backfill in Underground Mine.

Layering of filling body is common in large-scale filling areas. In this paper, the cement–sand ratio of 1:8 is based on the configuration of 68%, 70%, 72% and 74%; four concentrations; and filling layers of one-, two-, three- and four-layered cemented filling samples. Combined with a uniaxial compression test and two-dimensional particle flow software (PFC2D), the mechanical properties and failure modes were explored. The results show that the concentration can strengthen the uniaxial compressive strength of the filling body while increasing the filling times weakens its power; therefore, the constitutive damage model was constructed. It was found that the initial layered damage existed in the layered filling, and the total damage showed an upward trend of first fast and then slow; the main failure modes of one-layer and two-layer backfills showed prominent shear failure characteristics, and the three-layer and four-layer fillings were closer to tensile failure. From the crack generation to the specimen failure, there is a mutual conversion between different energies.

An Experimental Study on Enhancing Progressive Collapse Resistance Using a Steel Fiber–Reinforced Concrete Frame

This paper aims to investigate the inclusion efficiency of straight microsteel fibers to improve the structural ductility and deformability of reinforced concrete frames to achieve progressive collapse resistance. Four RC frames’ behavior has been tested at one-third scale in the removal scenario of the middle column. To compare, two frames without steel fiber were prepared to be the control samples. Frames of 0.5% steel fiber fraction volume were also prepared. The study aims to analyze mechanical properties, crack pattern, failure mode, structural ductility, and load-displacement behavior of the frames of normal concrete (NC), together with steel fiber–reinforced concrete (SFC). Based on the findings, an enhancement was observed in the structural ductility (the increase ratio reached up to 26%), stimulated by incorporating steel fiber in the normal concrete. The frames of SFC demonstrated more deflection by 19% compared with NC frames. Steel fiber, therefore, can be utilized to enhance RC elements’ ductility as an innovative design strategy in inhibiting progressive collapse.

Investigation of Anisotropic Behavior and Statistical Evolution of Acoustic Emission Energy during the Deformation of Layered Sandstone

To further understand the anisotropic behavior of layered rock and the precursor characteristics of rock mass instability, a series of uniaxial compression experiments using a loading system and an acoustic emission system was conducted on sandstone specimens. The influence of bedding on the mechanical parameters and failure modes and the statistical evolution of the acoustic emission energy were successively discussed. The results of axial stress-strain curves and crack propagation modes showed that the existence of a bedding plane increased the anisotropy of the rocks, and the magnitude of the bedding inclination also exerted certain influence on this anisotropy. Furthermore, we used the least squares method and the maximum likelihood method to analyze the b value and power-law exponent, respectively. The results of statistical evolution of acoustic emission energy showed that the b value, the effective power-law exponent, and the optimal exponent could be used as monitoring indexes for the rock mass stability. With the progress of the experiment, the following phenomena pertaining to acoustic emission activities occurred, which may indicate imminent danger of collapse: (1) the crackling noises increased significantly; (2) the variation of the b value exhibited a significant downward trend; and (3) the effective power-law exponent and the optimal exponent changed in different stages and gradually decreased as the final failure was approached. The findings in this paper may provide a theoretical basis for predicting the collapse and instability of rock mass structures.

A unified fracture criterion considering stress state dependent transition of failure mechanisms in bcc steels at –196 °C

The fracture properties of a high-strength steel with a body-centered cubic (bcc) crystal structure have been characterized at –196 °C by performing tensile tests with different specimen geometries, three-point bending tests using Charpy specimens, and fracture mechanics tests, covering a broad range of stress states under quasi-static conditions. Both strength and ductility of the bcc steel are significantly increased when the temperature is decreased from room temperature to –196 °C. Enormous plasticity occurs in the material during tensile tests using various specimens at –196 °C, while macroscopic brittle fracture takes place in high triaxiality scenarios. A stress state dependence of ductile to brittle transition properties is observed, as the failure mechanisms at –196 °C change from cleavage fracture to shear failure with decreasing stress triaxiality. A unified stress-state-dependent fracture criterion, which considers the transition of failure mechanisms, is proposed to describe the fracture properties of similar bcc materials at cryogenic temperatures. The threshold triaxiality at which the transition of failure mechanisms takes place is a material property that is determined by the strain hardening capacity and fracture strength. In addition, a probabilistic formulation relying on the extreme value distribution has been incorporated into the model to render the statistical nature of cleavage fracture.

Discrete element simulation on failure mechanical behavior of transversely isotropic shale under two kinds of unloading paths

Based on the discrete element method, a two-dimensional numerical model of shale with different bedding inclinations was established. Using this model, the macro-and meso-mechanical properties of bedded shale under different unloading paths and bedding inclination were studied. In this study, the damage mechanism of bedded shale during the unloading process is revealed. The simulation uses the displacement-controlled loading method, with a loading speed of 0.05 m∙s−1. The results indicate that the bedding inclination of the shale has a significant impact on both mechanical parameters and failure modes under unloading. The peak strength and the ultimate bearing capacity show a “U” shape trend under both unloading paths. Observations of maximum values are observed at β = 0° or β = 90° while observing the minimum values at β = 30°or β = 45°. The failure mode of shale specimens with β = 0° at lower initial confining pressure, the failure mode is splitting damage along the multiple bedding plans, which gradually changes to shear damage with increasing initial confining pressures crossing the weak surface. The failure mode of the specimens with β = 15–45° at different initial confining pressure is shear-slip damage along the bedding planes. And shale at β = 60–90° failure modes are all conjugate shear damage intersecting with the weak surface. The damage to the specimen caused by unloading and increasing the axial stress is greater than that caused by the unloading and constant axial strain. The effects of β = 0° and 90° on microcracking and stress distribution within the specimen are significantly smaller than for the other bedding inclinations.

Bolt stripping failure and ductility of end plate beam-column connections at ambient and elevated temperatures

PurposeThe effect of bolt stripping failure on the ductility of steel end plate beam-column connections has received relatively little investigation to date. The objective with the present work is to establish a validated numerical model of end plate connections at elevated temperatures, which predicts the mechanical behaviour and failure modes observed in the experimental tests including the bolt stripping failure. Furthermore, the validated FE model was used to investigate the effect of stripping failure on both the rotational and load-bearing capacity of end plate connection.Design/methodology/approachThe analysis was conducted on a validated numerical model of end plate connections at elevated temperatures, which predicts the mechanical behaviour and failure modes observed in the experimental tests including the bolt stripping failure. The material was modelled considering ductile damage initiation and evolution featured in ABAQUS/Standard.FindingsThis study demonstrates that thick end plates can prevent stripping failure which significantly improves the rotational capacity of the connection. This failure mode can develop readily with thin end plates; however the effect is often unrealistically mitigated through idealised experimental tests. The rotational capacity of a connection can be 5.0 times higher if stripping failure is avoided, particularly at elevated temperatures. Eurocode 3 part 1.8 does not consider the possibility of stripping failure when discussing the requirements for plastic analysis. It is concluded in the present study that by allowing for the possibility of bolt stripping, the mode of failure can often shift from end plate failure to bolt stripping, this in turn significantly reduces the connection rotational capacity.Originality/valueThe effect of bolt stripping failure on the ductility of steel end plate beam-column connections has received relatively little investigation to date.

Investigation on the mechanical behavior, permeability and failure modes of limestone rock under stress-seepage coupling

Limestone rock widely exists in various rock engineering, its mechanical behavior and permeability evolution have a great influence on the safety and stability of related engineering projects. To study the mechanical behavior, permeability and failure modes of limestone rock under stress-seepage coupling, triaxial compression coupled with permeability tests were carried out. Experimental results reveal that the failure of limestone still conforms to the Mohr-Coulomb criterion under stress-seepage coupling, and effective confining pressure σ3eff can indicate the effect of gas pressure PG and confining pressure σ3 on the deformation parameters of limestone samples. Peak stress σP and residual stress σR increase with the enhancement of confining pressure and decrease with the ascent of gas pressure. Permeability evolution of limestone under different gas pressures and confining pressures is generally similar, and the trend of initial permeability kI, peak permeability kP and residual permeability kR decreasing with effective confining pressure σ3eff can be expressed by the exponential function. The increase of confining pressure and decrease of gas pressure will retard the acoustic emission (AE) response and inhibit the propagation of microcracks. More importantly, limestone samples always show composite failure modes dominated by tensile cracks under low confining pressure, while under high confining pressure, the limestone samples show shear failure modes. The difference is limestone samples are composed of tensile microcracks on the microscale under stress-seepage coupling, and the proportion of shear microcracks grows as gas pressure PG and confining pressure σ3 increases. This research can provide a basic reference for relevant engineering applications.

Mechanical Performance and Failure Mode Research on the Braced Frame Joint of Tower Cranes in High-Rise Building Construction

The collapsing number of tower cranes has increased with the development of the building industry. The safety of tower cranes has the potential to improve practices of building and outcomes in construction. The mechanical performance and failure mode of braced frame joints are analyzed in this research. Firstly, a mechanical model of a braced frame joint (BFJ) is established, and the experiment is designed. The destruction process and failure mode are researched by experiment. Then finite element model is established by ABAQUS. Moreover, working conditions with different concrete strength grades (CSG) and tension direction are researched. The results prove that braced frame joint cracks seriously with ultimate bearing capacity, simultaneously, the pre-embedded steel component (PESC) is pulled out. The failure mode is tensile and bending failure of BFJ in the test. The ultimate bearing capacity of failure is controlled by concrete strength grades. The tensile strength increases with the CSG, and the ultimate capacity of BFJ improves equally. The brittle fracture characteristic is more obvious in the ultimate state. The failure mode changes from crushing failure to tensile and bending failure with increasing tension angle. The research results could provide a better understanding of the working mechanism and performance evaluation of the BFJ of the tower crane.

Experimental investigation on mechanical performance and failure modes of shale interbedded with sandstone under triaxial compression

Experimental investigation on mechanical performance and failure modes of shale interbedded with sandstone under triaxial compression