Compressive Failure Research Articles

Spatio-Temporal Compressive Behaviors of River Pebble Concrete and Sea Pebble Concrete in Island Offshore Engineering

Obtaining river or sea pebbles from local resources for concrete production is considered an economical and eco-friendly alternative, particularly in marine and island-offshore engineering. However, the resulting changes in the mechanical properties of these concrete have attracted attention. This study investigates the compressive behavior of concretes where river or sea pebbles partially (i.e., 33% and 67%) or fully (i.e., 100%) replace traditional gravel as coarse aggregate, using a noncontact full-field deformation measurement system based on digital image correlation (DIC). Compared to the traditional gravel concrete (GC), compressive strengths of the river pebble concrete (RPC) at constitution rates of 33%, 67%, and 100% decreased by 6.5%, 29.8%, and 38.9% while those values of the sea pebble concrete (SPC) decreased by 13.1%, 32.7%, and 44.3%, respectively. Meanwhile, SPC exhibited slightly lower compressive strength than RPC. The peak strains of both SPC and RPC decreased at lower substitution rates, although their stress-strain curves resembled those of GC. In contrast, RPC and SPC at higher substitution rates exhibited a noticeable stage of load hardening. Full-field deformation data and interfacial characteristics indicated that the compressive failure modes of both RPC and SPC showed significant interfacial slipping between pebbles and mortar with increasing coarse aggregate substitution rates. In comparison, fractures in coarse aggregate and mortar were observed in damaged GC. The study demonstrated that the spatio-temporal compressive deformation response and failure modes of SPC and RPC were distinct due to the introduction of pebbles, providing insights for engineering applications of river/sea pebble concrete in practical offshore or island construction projects.

Experimental study and finite element analysis on shear performance of high strength steel reinforced ultra-high performance concrete beam

This paper investigates the shear performance of high strength steel reinforced ultra-high (HSSUHPC). Test were carried out on seven beam specimens with the different parameters of web steel ratio, shear-to-span ratio, and steel fibres content in volume. The failure patterns and load-displacement curves were obtained. The bearing capacity, deformation capacity and strain variation laws of UHPC, steel web, stirrups, tensile longitudinal reinforcement and tensile flange of steel were analyzed. The experimental study established the finite element model of the shear performance of HSSRUHPC beams. The results of finite element fit well with the experimental results. Then parametric analysis was carried out. The results showed two shear failure patterns for the HSSRUHPC beam: shear diagonal compression failure and shear-compression failure. The mechanical process of the HSSRUHPC beam could be divided into four stages: the elastic stage, cracking stage, strengthening stage, and failure stage. There were two peak loads for the load-displacement curves. As the steel ratio of the steel web and yield strength of steel increased, the bearing capacity and deformation capacity of the HSSRUHPC beam increased. The shear-to-span ratio had a significant influence on the failure pattern of HSSRUHPC beam, and with the increase of the shear-to-span ratio, the bearing capacity of the HSSRUHPC beam decreased, but the deformation capacity increased. As fibre content increased, the crack resistance and deformation capacity of the HSSRUHPC beam were improved. With the increasing width ratio between the steel flange and beam, the bearing capacity of HSSRUHPC beam increased, but the change range decreased, so it is suggested that the width ratio between the steel flange and beam should not be larger than 0.6. As the stirrup ratio increased, the bearing capacity of the HSSRUHPC beam increased, but the availability of stirrups decreased, so it is suggested the stirrup ratio should not be over 3 %.

Mechanical and microstructural characterization of one-part binder incorporated with alkali-thermal activated red mud

The traditional production of silicate cement is associated with substantial carbon emissions and environmental degradation. In contrast, cementless alkali-activated binders, derived from solid waste and industrial byproducts, have garnered significant interest for their reduced material costs, energy efficiency, and environmental benefits. This research investigates the application potential of an advanced mixture of anhydrous sodium silicate and red mud in one-part alkali-activated binders. It is assessed through various analytical techniques, including compressive strength, X-ray diffraction, fourier transform infrared, thermogravimetric analysis, digital image correlation, and scanning electron microscopy with energy dispersive spectroscopy. Findings demonstrate that the synergy between red mud and anhydrous sodium silicate markedly enhances the early strength of one-part alkali-activated binders incorporated with alkali-thermal activation. The increment in sodium silicate content is pivotal for bolstering binder performance. A 40 % red mud admixture results in a compressive strength of 40 MPa, achieving an optimal carbon-to-strength ratio. The inclusion of polypropylene fiber significantly influences the mode of compression failure in alkali-activated binders. Alkali-thermal activation of red mud elevates the levels of active silicon and aluminum, markedly augmenting the reactive silica and aluminum content. This modification fosters the disintegration and reorganization of Si-O and Al-O bonds in silica-aluminum materials, culminating in a denser structure. This structure is characterized by the generation of amorphous ((N, C)-A-S-H) gels, contributing to the material's enhanced properties.

Optical-acoustic responses in uniaxial compression failure progress of fibre-reinforced cemented bodies

ABSTRACT Incorporation of fibers in the cemented body material can obviously improve its mechanical properties. Digital image correlation (DIC) and acoustic emission (AE) techniques were used to monitor the “optical-acoustic” response in uniaxial compression failure progress of the fiber-free and glass fiber-reinforced cemented bodies, and the response characteristics of the two methods in the stability monitoring of the cemented body as a support structure were discussed. The results show that the glass fiber-reinforced cemented body showed a failure to the internal structure after the peak strength, but the specimen remained intact without spalling and still maintained a long ductile deformation. The transverse displacement changes curve of the fiber-free cemented body appeared a “positive-negative turning point”. The transverse displacement of the glass fiber-reinforced cemented body is negatively correlated with the DIC time. The full-field strain information obtained by the DIC technique can be used to quantify the degree of damage on the surface of the cemented bodies, and the AE ringing count and energy signal response are more sensitive to the internal friction and impact of the cemented bodies. The results of the study can provide a reference for determining the stability monitoring method of the cemented body as a support structure.

Bearing Capacity of Hybrid (Steel and GFRP) Reinforced Columns under Eccentric Loading: Theory and Experiment

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results.

Design and mechanical performance analysis of T-BCC lattice structures

The Body-Centered Cubic (BCC) lattice structure is commonly used in high-end equipment fields, such as aerospace, due to its superior mechanical properties, lightweight characteristics, and ease of processing. However, there is a need to improve the performance-to-weight ratio of the traditional BCC lattice structure. This study utilizes topology optimization to design a T-BCC lattice structure based on the BCC unit cell, with the aim of maximizing stiffness. A model proposing the characterization of the Young's modulus of BCC lattice structures is presented. The model is based on calculations of cell porosity and beam stress analysis, assuming a large cell. This approach indirectly enables the calculation of the Young's modulus of T-BCC lattice arrays in multiple dimensions. Simulation and experimental comparison were used to analyze the compressive performance and load-bearing modes of T-BCC lattice structures, revealing the mechanisms of compressive deformation and failure modes. The accuracy of the characterization model for Young's modulus was found to be 93.1%. Compared to BCC lattice structures designed by traditional methods, T-BCC lattice structures designed via topology optimization can increase the Young's modulus by up to 36% and yield strength by 37.2%. This suggests that T-BCC lattice structures are a more lightweight and efficient solution for designing components in high-end equipment fields.

Evaluation of the seismic response of reinforced concrete buildings in the light of lessons learned from the February 6, 2023, Kahramanmaraş, Türkiye earthquake sequences

AbstractOn 6 February 2023, two significant seismic events occurred in the southeastern region of Türkiye. The seismic activity, which was perceptible in numerous countries beyond Türkiye, resulted in a considerable number of fatalities. A considerable number of individuals lost their lives and were rendered homeless as a result of the disaster. Two of the most significant factors contributing to the occurrence of these tragedies are the magnitude of the earthquake and structural deficiencies. The present study is concerned with a detailed analysis of these two factors. This study initially considers the seismicity of the region where the earthquakes that occurred on 6 February 2023 took place, as well as the seismic characteristics of these earthquakes. Subsequently, the findings of the field studies conducted in Hatay, Adıyaman, Kahramanmaraş and Malatya, the cities where the earthquakes caused the most destruction, are presented. The objective of the field study is to ascertain the collapse patterns, structural damages and the factors influencing these damages in reinforced concrete structures in the region. The primary causes of damage to structures can be attributed to several factors, including the presence of a strong beam-weak column mechanism, the soft story-weak story mechanism, the pounding effect, the short column damage, the long cantilever and overhangs, the short beam damage, the buckling damage, the torsion effect, the quality of the materials, the insufficient transverse reinforcement, the compressive failure due to over-reinforcement, the corrosion effect, the damage to reinforced concrete shear walls, the infill wall damage, and the damage caused by the soil and foundation system. These causes have been evaluated and recommendations have been formulated to prevent structural damage.

Study on the influence mechanism of interfacial inclination angle on the mechanical behavior of coal and concrete specimens

In recent years, the proposed distributed underground reservoir technology has attracted a lot of attention from experts and scholars in the field of engineering. This technology not only avoids the waste of mine water resources, but also realizes the rational utilization of coal mine underground space, and promotes the green and sustainable development of coal mining. As a storage facility of the underground reservoir, the stability of the coal-concrete composite structure will directly affect the long-term safe operation of the underground reservoir. In light of this situation, this study conducted uniaxial compression and acoustic emission experiments on coal-concrete specimens with interface inclinations of 0°, 15°, 30°, 45°, 60°, 75°, and 90° to investigate the impact of interface inclination on coal-concrete specimen stability. The test results show that the stress-strain curve passes through three stages: compression, elastic deformation, and deformation failure. The peak stress, peak strain, and elastic modulus exhibit a “U”-shaped distribution with varying angles, reaching a minimum at 60°. Crack analysis using RA-AF reveals that tension cracks predominate at 0°-30°, while shear cracks predominate at 45°-90°. The application of the Mohr-Coulomb criterion to coal-concrete specimens is discussed, and a derivation of the formula for calculating the ultimate principal stress is provided. The research in this paper provides a theoretical reference for the structural design and parameter selection of underground reservoir dams in coal mines.

Compressive Failure Characteristics of 3D Four-Directional Braided Composites with Prefabricated Holes.

The low delamination tendency and high damage tolerance of three-dimensional (3D) braided composites highlight their significant potential in handling defects. To enhance the engineering potential of three-dimensional four-directional (3D4d) braided composites and assess the failure mode of hole defects, this study introduces a series of 3D4d braided composites with prefabricated holes, studying their compressive properties and failure mechanisms through experimental and finite element methods. Digital image correlation (DIC) was used to monitor the compressive strain on the surface of materials. Scanning acoustic microscope (SAM) and scanning electron microscopy (SEM) were used to characterize the longitudinal compression failure mode inside the material. A macroscopic model is established, and the porous materials are predicted by using the general braided composite material prediction theory. While reducing the forecast cost, the error is also controlled within 21%. The analysis of failure mechanisms elucidates the damage extension mode, and the porous damage tolerance ability aligns closely with the bearing mode of braided material structure. Different braiding angles will lead to different bearing modes of materials. Under longitudinal compression, the average strength loss of 15° specimens is 38.21%, and that of 30° specimens is 8.1%. The larger the braided angle, the stronger the porous damage tolerance. Different types of prefabricated holes will also affect their mechanical properties and damage tolerance.

CDPM2F: A damage-plasticity approach for modelling the failure of strain hardening cementitious composites

For the use of micro-mechanics based constitutive models for fibre reinforced strain hardening cementitious composites in finite element simulations of structural components, it is required to link the crack opening at the scale of fibres to the cracking strain at the scale of structural components. We aim to establish this link by incorporating a micro-mechanics based fibre bridging stress crack opening law into a macroscopic damage-plasticity approach, which we call CDPM2F. The model is implemented in the open-source finite element program OOFEM. The model produces mesh-insensitive results and its response agrees well with experimental results for failure in tension, shear and compression reported in the literature.

Effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite for engineered barrier system

This study aims to investigate the effects of specimen size and loading rate on the mechanical property of Bentonil-WRK bentonite buffer material for engineered barrier system. Highly instrumented unconfined compressive strength tests were performed on cylindrical specimens prepared using cold isostatic pressing (CIP) technique at varying testing conditions: (a) CIP pressures of 29.43 MPa, 39.24 MPa, and 58.86 MPa, (b) specimen sizes of 30 × 60mm, 40 × 80mm, and 50 × 100mm, and (c) loading rates of 0.5 %/min, 1.0 %/min, and 1.5 %/min. As CIP pressure increases, the unconfined compressive strength (qu), failure strain (εf), and elastic modulus (E) of Bentonil-WRK increase similar to Gyeongju compacted bentonite (KJ-II). Increase in diameter results in a decrease in qu and εf, and increase in E. Minimal effect of loading rate was observed on qu and εf. However, increasing loading rate tends to increase E. In addition, decrease in diameter increases the elastic threshold axial strain (εe,th). Increase in diameter and loading rate slightly increases Poisson's ratio. Prediction models are provided for assessing the effects of specimen diameter on qu and εf. Furthermore, correlation models of qu to ρd and E are proposed for Bentonil-WRK bentonite buffer material.

Compression test and size effect study of defective wood

ABSTRACT Wood, as a natural material, inevitably contains initial defects such as knots, cracks, and decay, which are important factors affecting its mechanical properties and cannot be ignored. In order to investigate the influence of initial defects on the compressive mechanical properties of wood, Norway spruce was selected as the research object. Wood specimens without and with initial defects were prepared, and uniaxial compression tests were conducted. Combined with Digital Image Correlation (DIC) and finite element analysis, the compressive mechanical properties of defective wood were studied. The results showed that compared to defect-free specimens, specimens with defects exhibited a shortened elastic stage in the load-displacement curve, and the rate of decrease in load after reaching the peak was lower than that of defect-free specimens. For specimens of the same size, the compressive strength of specimens with defects was lower than that of defect-free specimens. The established finite element model could effectively simulate the compressive failure process of wood with initial defects, validating the effectiveness of numerical simulation. Bažant's size effect theory can be used for size effect analysis of the compressive strength of wood with initial defects in the longitudinal direction.

Study on the influence of temperature on the damage evolution of hot dry rock in the development of geothermal resources

In order to more accurately understand the rock mechanics properties of hot dry rock (HDR) reservoirs under high-temperature conditions and further guide the drilling and construction of HDR wells, conducting research on rock damage evolution under high-temperature conditions plays a guiding role in the efficient development of geothermal resources. To reveal the evolution law of fracture damage of HDR under temperature influence, taking marble as an example, the thermo-mechanical damage and failure mechanism under the conditions of 30 °C, 60 °C, 90 °C, 120 °C and 150 °C were studied using a rock high-temperature rheometer and an acoustic emission (AE) testing system. The numerical simulation results were compared with the indoor experimental results by combining the particulate flow program Particle Flow Code 3D (PFC3D) to verify the effectiveness of the simulation analysis model of thermo-coupled particulate flow at the micro scale. The results show that under high temperature, the marble three-axis compression failure passes through the compaction and elastic deformation stage, plastic deformation stage, ductile failure stage and instability failure stage, and the peak strength and elastic modulus of the marble decrease with the increase of temperature, and the acoustic emission b-value of the sample can judge the damage evolution process of the marble. At the micro scale, high temperature accelerates the force chain transmission between particles, the contact force between marble particles gradually decreases during the heating process, and the number of particle bonding failures increases steadily; the bearing capacity and elastic modulus attenuation of the rock are the result of microcrack evolution, and the force chain void zone and particle displacement field inside the sample are consistent with its macroscopic failure form. The development of microcracks in marble under different test loading conditions is different, and with the increase of test temperature, the total number of cracks inside the sample increases, but the proportion of shear cracks decreases, the activity of particle displacement increases, and the “plastic extension” characteristic of marble becomes more significant. The thermal damage evolution of marble was quantitatively analyzed based on the elastic modulus method and the peak stress method, and the damage evolution law of marble under different temperatures was obtained.

Delamination propagation manipulation of composite laminates under low-velocity impact and residual compressive strength evaluation

The poor delamination resistance of laminated composites is always regarded as a potential threat to the service safety of the primary load-bearing structure. However, delamination is inevitable during low-velocity impact (LVI) events, as a result, the residual compressive strength of laminates is significantly reduced. Discrete interleaving is a novel strategy to enhance the damage tolerance of these composites, yet the damage mechanism of laminates modified by this method is more complicated. In this paper, we investigated the delamination failure mechanism of quasi-isotropic laminates through thermal deply experiment, and proposed a discrete interleaving scheme based on its damage characteristics. Accordingly, a series of LVI and compression-after-impact (CAI) tests were conducted to validate the design philosophy. Besides, the damage constitutive relation and evolution model applicable to discrete interleaved laminates were explored in detail, a numerical model embedded strain-rate-dependent progressive damage criterion and modified cohesive zone model was established to further study the damage mechanism. Experimental and numerical results exhibit excellent alignment. The results demonstrate that the CAI strength is enhanced by 16.48 % according to the proposed discrete interleaving method. The main reason is attributed to the employed method can manipulate the delamination propagation during the low-velocity impact loading, and then maneuver the compressive failure mode of laminates to achieve a favorable benign failure (implying higher CAI strength).

Compressive strength and failure mechanism of high-modulus carbon fibers produced from polyacrylonitrile and mesophase pitch

Compressive strength and failure mechanism of high-modulus carbon fibers produced from polyacrylonitrile and mesophase pitch

Simulation Study on Quasi-Static Compressive Mechanical Properties of Honeycomb Structures with Negative Poisson’s Ratio

Negative Poisson’s ratio structures are widely used in military, aerospace, vehicles, air-dropped packages, and medical devices due to their high strength, stiffness, energy absorption, and impact resistance, but their mechanical properties are significantly affected by geometric parameters. In this paper, for the compression energy-absorbing mechanism of the re-entrant hexagonal honeycomb structure, numerical simulations are used to study the effects of wall thickness and angular gradient on its compression failure mode and energy-absorbing performance. The results show that the wall thickness has little impact on the compression failure mode, while the angular gradient has a significant impact on the compression failure mode. The wall thickness has a significant effect on the energy-absorbing performance, and the larger the wall thickness is, the better the energy-absorbing property is; the energy-absorbing performance of the symmetric negative gradient structure is significantly better than that of the other three angular gradients, and all the four kinds of angular gradient structures have better energy-absorbing performance than that of the conventional re-entrant honeycomb. The results obtained provide a reference for improving the energy absorption performance of negative Poisson’s ratio honeycomb structures under quasi-static compression.

Study on microstructure of cemented paste backfill with initial defects under uniaxial compression failure

In order to fully understand the micro and fine structural characteristics of the cemented paste backfill (CPB) with initial defects, this paper carries out uniaxial compression test on the CPB and real-time monitoring with DIC technology, analyses the crack extension and deformation characteristics on the surface of the specimen, carries out SEM test on the damaged specimen, binarizes the SEM images, and performs microscopic pore analysis on the processed binarized images using PCAS software. Then some parameters such as porosity, probability entropy, probability distribution index, fractal dimension, form factor, etc. of the specimens with different initial defects are discussed. The study shows that the damage form of CPB under uniaxial compression is mainly tensile damage, and gradually changes from tensile damage to shear damage when the specimen reaches the peak strength. The overall displacement and strain of each monitoring point on the specimen increases rapidly after entering the plastic deformation stage. There are many small microcracks and pores in the CPB, and there are a large number of aciculate ettringite and C-S-H gel hydration products, which are generated in the sample unevenly. With the addition of air-entraining agent (AEA), within a certain range, the number of pores inside the CPB increases. Many small pores also form large pores because of the connectivity between the pores, the porosity of the specimen increases, and the morphology and structure of the pores are relatively more regular. However, the direction of the pore development still does not have good directionality, and the initial defects become increasingly obvious.

Study on the axial compression behavior of masonry columns strengthened with engineered cementitious composite splints and fiber-reinforced polymer strips

This paper presents experimental and analytical studies on the axial compressive properties and failure mechanics of 19 strengthened masonry columns. The masonry column was strengthened singly and compositely by applying engineered cementitious composite (ECC) splints and wrapping discontinuous fiber-reinforced polymer (FRP) strips around the sides of the masonry column. The effects of the type of strengthening material (ECC splints or FRP strips), the thickness of the ECC splint, and the FRP strip strengthening area ratio on the failure mode, peak load, strain behavior, and energy dissipation of the specimens were analyzed and discussed in this experimental study. Under the appropriate parameters, the best strengthening effect was observed for the compositely strengthened masonry columns. In particular, the ductility, bearing capacity, and energy dissipation of masonry columns can be significantly improved by utilizing FRP with lower tensile strength, a higher FRP strip strengthening area ratio and a thicker ECC splint. Based on the existing computational models and code calculation methods for masonry columns strengthened with ECC splints and FRP strips, a formula for calculating the compressive bearing capacity of strengthened masonry columns was derived. The error between all the calculated and the measured results was less than 7.1%.

Investigation of the freeze-thaw deterioration behavior of hydraulic concrete under various curing temperatures

To address the issue of damage and deterioration of hydraulic concrete materials in cold regions, experiments were conducted to investigate the microstructural and mechanical properties of concrete under the combined effects of various curing temperatures and freeze-thaw (F‒T) cycles. The results indicate that as the curing temperature decreases, the peak compressive strength of concrete decreases, while the peak strain increases and the elastic modulus decreases. These trends become more pronounced with the progression of F‒T cycles. Additionally, during the compression failure process of concrete, the amplitude of the acoustic emission exhibits a more significant and rapid increase as it approaches the critical state, indicating a stronger brittle characteristic of concrete after F‒T damage. Microscopic test results demonstrate that the influence of curing temperature on the pore structure of concrete after F‒T primarily manifests in the mesopores and large pores. Moreover, the reduction in curing temperature increases internal defects in concrete, deteriorates the crystallinity of hydration products, and leads to the aggregation of unhydrated cement particles. Insufficient curing temperatures slow the hydration rate of cementitious materials, affecting the density and overall performance of concrete. Finally, damage prediction models based on the Weibull distribution were established, using the relative dynamic modulus of elasticity, compressive strength loss rate, and mass loss rate as damage factors. The model based on the relative dynamic modulus of elasticity was more sensitive to the number of F‒T cycles. All models exhibited a goodness of fit exceeding 0.89, indicating that they accurately reflect variations in the observed data and can be used to predict the service life of concrete under F‒T cycles. This provides theoretical references for the degradation and damage of hydraulic concrete in cold regions.

Compressive failure and fragmentation of fused silica glass under quasi-static loading

This paper investigates the failure and post-failure fragmentation processes of fused silica glass cylinders under quasi-static compression, addressing the effects of surface finish on apparent strength. The compressive strengths of cylinders with side-polished sides under dry friction conditions (PSG-D) or lubricated conditions (PSG-L) were 2.52 GPa and 2.32 GPa, respectively. In situ observations showed that these specimens fractured from either the top or bottom contact surfaces, and that friction between the specimen and the loading anvil delayed the development of surface cracks. The unpolished rough side specimens (RSG-D) under dry friction conditions failed at a much lower level of 1.54 GPa, initiated by defects in the side surfaces. Specimens "explosively" fragmented upon failure. The propagation speed of the failure front ranged from 1800 to 2800 m/s. The average sizes and distributions of the fragments were determined through statistical analysis, with results showing reasonably close agreement with theoretical estimations.