Reduction Of Bearing Capacity Research Articles

Experimental Study on Bearing Capacity Reduction of the Steel Wire-Rings in Flexible Barriers Due to Corrosion

Flexible barriers mitigate geological hazards, relying crucially on wire-ring nets to intercept rockfalls and debris. However, constant exposure to natural environments renders their metal components susceptible to corrosion, affecting the protective efficacy. To investigate the changes in mechanical properties of wire-ring nets resulting from corrosion, the neutral salt spray tests followed by quasi-static tests on uncoated, Zinc-coated, and Galfan-coated high-strength steel wires and wire-rings were conducted. These tests established the correlation between the steel wire's breaking force and its weight loss rate, ultimately facilitating the creation of a pertinent mathematical model. The decline in the breaking force of various types of wire-rings due to corrosion was compared, indicating the influence of corrosion duration, number of winding turns, winding techniques, and coating types on the wire-ring's mechanical performance. Subsequently, the formula for calculating the breaking force of wire-rings in relation to the weight loss rate of the steel wire was derived. Finally, based on the linear relationship between the capacity of single wire-rings and wire-ring nets, a formula was established to estimate the puncturing force of wire-ring nets under different atmospheric corrosion periods. This predictive model provides a basis for the durability design of flexible barrier with different anti-corrosion measures under various atmospheric conditions, and also offers specific insights into maintenance strategy for the existing flexible barriers.

Fire resistance and stability of non-uniformly heated steel plate girders with slender section

The results of experimental tests and computer simulations pertaining to the bearing capacity of unevenly heated girders made of slender thin walled class 4 sections are presented in this paper. It has been shown, that for the analyzed group of elements the value of lateral-torsional buckling coefficient depends on the initial load level applied to the considered element and the cross section bearing capacity reduction level under fire conditions. It has been determined as well that the influence of steel grade used on the value of buckling coefficient is negligible. Based on the research conducted, a new proposal for calculation of the lateral-torsional buckling coefficient for considered group of elements has been prepared. A simplified method to determine the bearing capacity of non-uniformly heated class 4 sections is proposed in this paper as well. It has been shown that both proposed methods exhibit sufficient convergence of results with the results of computer simulations, and satisfy appropriate acceptance criteria as well.

Methodology for calculating load capacity reduction and slip relationship of clustered group nail connectors

Clustered group nail connectors are key connecting components for the full lifecycle construction and safe operation of steel–concrete composite structural bridges. To thoroughly investigate the stress mechanism of clustered group nail connectors in steel–concrete composite structures, this paper conducts a detailed numerical analysis on 100 sets of such connectors. It analyzes the stress mechanism of individual nail connectors and quantitatively calculates the group nail effect under the coupled action of multiple factors (nail spacing between layers, number of nail layers, concrete strength). Based on clarifying the force transmission patterns of nails and concrete in different layers during the loading process, this paper proposes a method for calculating the average bearing capacity reduction coefficient and the load-slip curve of single nails in clustered group nail connectors under the coupled action of multiple factors, which has been validated by experimental data. This research provides a theoretical basis for the design and calculation of group nail connectors in steel–concrete composite structural bridges.

Investigation of the Influence of Local Low Strength Concrete on the Bearing Capacity of Bending Reinforced Concrete Beams

Reinforced concrete beams can experience local low concrete strength under certain conditions, for example, poor construction practices can cause problems such as concrete voids, surface cavities, block cracking, surface sinks and create areas of low concrete strength. This study presents the response of flexural hinge-supported reinforced concrete beams with different local areas of low concrete strength along the span. Modified models are adopted to describe the concrete properties and an ideal elastic-plastic model is adopted for the steel properties. The beam was divided into three main parts: one sensitive to bending moment, the second sensitive to shear, and the third sensitive to bond. The variables included two types of concrete strength and one reinforcement diameter. The results show that the most critical region with low concrete strength along the span of the beam is the confluence zone near the supports, which is reflected in the ductility of the load-deflection curves. A new generalized empirical model is developed to predict the effect of bearing capacity reduction from local low-strength concrete.

Effects of In-Plane Damage of infill Walls on Their Out-of-Plane Bearing Capacity Reduction Factors

Effects of In-Plane Damage of infill Walls on Their Out-of-Plane Bearing Capacity Reduction Factors

Fracture Disaster Assessment of Model Concrete Piles in Loess Slope Engineering under Non-Uniform Lateral Loading

Existing model tests for reinforcing loess slopes with stabilizing piles are often challenged by simulation inaccuracies in lateral loading modes and scaling. Addressing these concerns, this study conducts model tests and numerical simulations to scrutinize the damage characteristics of concrete piles in two varying loess slope conditions under non-uniform lateral loading. The tests were designed to strictly maintain the similarity ratio of the concrete piles. The results reveal a no table 20% reduction in lateral bearing capacity due to the penetration of a potential sliding surface, exacerbating the stress on the piles. Furthermore, compared to uniform loess slopes, the presence of a sliding surface leads to a 38.4% increase in the height of the stress concentration point, resulting in earlier crack formation in the piles. These findings offer substantial theoretical and practical insights, highlighting the critical need for accurate model simulation in slope stabilization research and providing a basis for improving engineering practices.

Effect of Twin Circular Underground Voids on Bearing Capacity of Strip Foundations

Underground voids can significantly alter the stress and strain conditions of the surrounding soil mass, consequently affecting the stability of buildings located on the surface. Numerous numerical and experimental methods have been employed to investigate the effects of voids on nearby structures. In this research, a mixed lower bound-finite element method is utilized to study the stability of strip foundations situated above twin continuous voids. The soil behavior is modeled using the Mohr-Coulomb yield function along with an associated flow rule. Three-noded triangular stress elements are used to mesh the stress field, considering stress discontinuities at the common edges of adjacent elements. The study assumes that the two voids are identical in terms of radius, distance from the footing centerline, and depth from the ground level. The primary geometrical parameters considered in the analysis are the location and radius of the voids, as well as the strength parameters of the soil. By investigating the changes in bearing capacity concerning these factors, practical charts are proposed to aid in understanding the stability of the foundation. The results of the current study reveal the existence of an unsafe zone beneath the foundations, where the impact of the twin voids on bearing capacity reduction can be significant. Understanding these effects is crucial for design and construction of structures in areas prone to underground voids and also to decide where to bore infrastructure tunnels in order to have minimum effect on stability of the above buildings.

The influence of the void shape in the bearing capacity of rock mass with a superficial void

In this study is proposed a chart that allow estimating the reduction of bearing capacity due to the existence of a superficial void in a rock mass. It is contemplated the influence of different shapes and size of the void in relation to the foundation. The reduction of the bearing capacity is analyzed through the Finite Difference Method. In the numerical model, six possible cavity shapes are considered, with three different sizes and depths. Calculations are made considering eighteen types of rock masses, modelled by the H&B failure criterion. The results demonstrate that the critical depth where the cavity no longer influences the bearing capacity varies considerably depending on the geometric variables (size, shape and location of the void). In addition, it is observed that the relation between the bearing capacity obtained considering the rock mass with and without void is not affected by the geotechnical parameters of the H&B failure criterion. According to the results analyzed and graphic output, the variation in the stress distribution in the rock mass and the change of the failure mechanism under the different hypotheses studied can be observed. The results are presented in chart that facilitate to directly estimate the reduction of the bearing capacity of a rock mass with void based on geometric parameters.

Gait analysis: An effective tool to mechanically monitor the bone regeneration of critical-sized defects in tissue engineering applications.

Tissue engineering has emerged as an innovative approach to treat critical-size bone defects using biocompatible scaffolds, thus avoiding complex distraction surgeries or limited stock grafts. Continuous regeneration monitoring is essential in critical-size cases due to the frequent appearance of non-unions. This work evaluates the potential clinical use of gait analysis for the mechanical assessment of a tissue engineering regeneration as an alternative to the traditional and hardly conclusive manual or radiological follow-up. The 15-mm metatarsal fragment of eight female merino sheep was surgically replaced by a bioceramic scaffold stabilized with an external fixator. Gait tests were performed weekly by making the sheep walk on an instrumented gangway. The evolution of different kinematic and dynamic parameters was analyzed for all the animal's limbs, as well as asymmetries between limbs. Finally, potential correlation in the recovery of the gait parameters was evaluated through the linear regression models. After surgery, the operated limb has an altered way of carrying body weight while walking. Its loading capacity was significantly reduced as the stance phases were shorter and less impulsive. The non-operated limbs compensated for this mobility deficit. All parameters were normalizing during the consolidation phase while the bone callus was simultaneously mineralizing. The results also showed high levels of asymmetry between the operated limb and its contralateral, which exceeded 150% when analyzing the impulse after surgery. Gait recovery significantly correlated between symmetrical limbs. Gait analysis was presented as an effective, low-cost tool capable of mechanically predicting the regeneration of critical-size defects treated by tissue engineering, as comparing regeneration processes or novel scaffolds. Despite the progressive normalization as the callus mineralized, the bearing capacity reduction and the asymmetry of the operated limb were more significant than in other orthopedic alternatives.

A modal-based method for blast-induced damage assessment of reinforced concrete columns: Numerical and experimental validation

Reinforced concrete (RC) columns play a crucial role in the overall performance of modern RC frame buildings under blast loading. The RC columns under blast loads might experience various irreversible consequences such as concrete cracks, crushing and spalling, changing the status of both modal properties and load-carrying capacity. In this paper, the blast-induced damage assessment of the RC columns involving the measurement of modal parameters was introduced and validated. Firstly, a modal-based method for blast-induced damage assessment of RC columns was proposed, in which the damage is characterized as the reduction of axial bearing capacity and further expressed as the explicit function of the vibration frequencies and the mass-normalized displacement mode shapes. Then, the finite-element analysis program LS-DYNA was employed to establish the numerical model of RC columns under axial compression loads and lateral blast loads. The residual load-bearing capacities and modal properties of the RC columns were illustrated. By using the numerical results collected in the present study, the validity of the proposed damage assessment method was discussed and proved numerically. Further, field explosion tests and experimental modal tests were conducted, and the results showed that the modal-based damage assessment method exhibited remarkable agreement with the blast damage determined by residual bearing capacities. Based on the numerical and experimental results, the proposed modal-based damage assessment method is applicable for the non-destructive evaluation of blast-induced damage of RC columns.

Investigation on the properties of compacted silty clay subjected to electro-osmosis using bender element

The moisture content of subgrade soil in seasonally frozen regions is often higher than its optimum value, leading to a decline in mechanical properties and a reduction in subgrade bearing capacity. Electro-osmosis has shown promise as a technology for controlling subgrade moisture, but significant heterogeneity has also been observed in treated soil. This study investigates the impact of electro-osmosis on soil stiffness through a series of bender element tests of compacted clay. The effects of dry density and supply voltage on the performance of electro-osmosis treatment and the layered structure and anisotropy of the soil were analyzed. The results show that electro-osmosis treatment increased the shear wave velocity of the soil by 140% compared to untreated saturated soil and by 70% compared to soil with optimum water content. It has also been found that layered compaction of soil resulted in a layered structure, with electro-osmosis having a more prominent impact on soil near the cathode, resulting in a more pronounced layered structure. Besides, electro-osmosis was found to enhance soil anisotropy, particularly near the anode. Increasing the dry density and voltage levels can help improve soil uniformity. These findings provide insights into the potential use of electro-osmosis in improving soil stiffness, which could benefit various engineering applications.

Experimental Investigation on Particle Breakage Behavior of Marine Silica Sand under High-Stress Triaxial Shear

There is often obvious particle breakage for silica sand under high-stress, which will lead to the bearing capacity reduction and excessive settlement of the foundation. This paper focuses on the particle breakage characteristics of marine silica sand from the East China Sea under high-stress conditions. A series of conventional triaxial tests for silica sand, including consolidated drained (CD) and consolidated undrained (CU) shear tests, were conducted under the confining pressures in the range of 2–8 MPa to investigate the breakage rule during the shearing process. The developments of particle breakage index Br with axial strain ε1 and volumetric strain εv present hyperbolic and linear trends, respectively. A hyperbolic model was adopted to describe the relationship of Br and ε1 and the corresponding model parameters were obtained. The particle breakage index also has a good correlation with the input work per unit volume under various average stresses, regardless of the stress history. Furthermore, the relationship between the fractal dimension and the particle breakage was studied based on the particle size distribution curve. It is concluded that the fractal dimension increases in an up–convex hyperbolic trend with the increase of particle breakage index. The dividing radius for whether the silica sand particles exhibit the fractal features is determined as approximately 0.4 mm. This is anticipated to provide reference and supplementary test data for analyzing sand constitutive models/environments regarding particle crushing.

Evaluation Model of Hard Limestone Reformation and Strength Weakening Based on Acidic Effect

The typical thick-hard limestone roof with high failure pressure and easy fracture closure under in situ stress is extremely prone to induce disasters, which seriously threatens the safe production of coal mines. The modification of carbonate minerals by acidic effects can effectively realize the weakening control of hard limestone strata. In this study, a multi-factor orthogonal experiment was designed for limestone acidification reactions, and the evaluation model for the reformation and strength weakening of hard limestone based on the acidic effect was established accordingly. The results showed that there is an order in the influence of various factors on the reaction parameters and strength indices of acidified limestone, and the improvement of rock properties by the level difference of acid concentration is significantly better than that of acid type and acidification time. Through numerical analysis, the evaluation model of limestone reformation and strength weakening considering the acid reaction parameters is given. The reliability of the model passed the credibility test and experimental verification, which can effectively reflect the strength response characteristics of acidified limestone. The simulated annealing (SA) algorithm is introduced to derive the optimal acidification system suitable for limestone weakening. Combined with the model, the control mechanism of the acidic effect on hard limestone strata was analyzed. The acidic effect can not only induce the rapid generation and expansion of micro-cracks at mineral-containing crystal defects, but also make the cracks remain relatively open under in situ stress due to the differential interaction on mineral components, which is conducive to the bearing capacity reduction and structural damage of limestone rock mass. The research results provide theoretical guidance for the acidification control of hard limestone strata in underground mines.

Research on dynamic p-y curves in liquefied sand under cyclic loading conditions

Under dynamic cyclic loads, the pore water pressure in saturated sand rises continuously, which leads to the reduction of horizontal bearing capacity or the damage of the pile foundation. Under dynamic cyclic loads, the existing calculations methods of horizontal bearing capacity of pile foundations were obtained by proposing a reduction factor for the static p-y curve model mostly. Compared with the test results, the soil resistance around the pile obtained by this method is often overvalued and the pile-soil relative displacement has a relative underestimation. As a result, this method is not suitable for pile foundation design. Therefore, the variations of soil resistance around the pile and the pile-soil relative displacement are obtained by analyzing the effect of pore pressure ratio on soil strength around the pile in saturated sand in this paper. The theoretical formulas related to the cyclic vibration times and pore pressure ratio are proposed. The proposed formulas are introduced into the dynamic p-y curve model to obtain the dynamic p-y backbone curve in the process of sand liquefaction. The research results show that the variations of the soil resistance around the pile and the pile-soil relative displacement are related to the pore pressure ratio and the cyclic vibration times during the sand liquefaction. As the cyclic vibration times increases, the pore pressure increases, the soil resistance around the pile decreases and the pile-soil relative displacement increases.

Studying the Behavior of Asphalt Stabilized Gepseous Soil for Earth Embankment Model

The study presents the test results of stabilizing gypseous soil embankment obtained fromAl- Faluja university Campus at Al-Ramady province. The laboratory investigation was dividedinto three phases, The physical and chemical properties, the optimum liquid asphalt (emulsion)requirements (which are manufactured in Iraq) were determined by using one dimensionalunconfined compression strength test.in the first phase , The optimum fluid content was 11%(6% of emulsion with 5% water content).. At phase two, the effect of Aeration technique wasinvestigated using both direct shear and permeability test. At phase three for the case of staticload , the pure soil embankment model under dry test condition was investigated, The testingprogram included the determination of the unconfined compressive strength, direct shearstrength, constant head permeability test, and one dimensional consolidation test for pure andasphalt stabilized gypseous soil. Testing was carried out in dry and absorbed conditions, themaximum pressure that can be supported before failure (ultimate sustained pressure) is 0.76MPa with vertical settlement (0.21 mm) . However, For the pure soil embankment model underabsorbed condition it was found that the maximum pressure before failure (ultimate sustainedpressure) is 0.3 MPa with vertical settlement (12 mm), Which reflects the reduction in bearingcapacity by (61%). Compression was made for absorbed stabilized soil and un-absorbed soiltested under hydraulic conductivity test for seven days, the results showed that a very lowmargin deffeneces in maximum pressure resistance and settlement were obtained (4.38 MPa ,0.11mm ) and (4.11MPa , 0.12mm).

Research on the resilience model of a new prefabricated shear wall structure

Based on high-strength bolts, steel plates and other components to achieve the advantages of prefabricated shear wall assembly connection “dry connection” operation advantages, a new type of assembled shear wall with friction energy consumption function was proposed. Using a combination of model tests and numerical simulations, three shear wall specimens with a scaling ratio of 1:1.54 were designed and the corresponding seismic performance tests were carried out. The effects of axial compression ratio and longitudinal reinforcement rate of edge members on the damage mode, hysteresis performance, load carrying capacity, deformation performance, stiffness degradation and energy dissipation capacity of specimens are systematically analyzed. The test results showed that the final failure modes of the three specimens were similar, which was the bending-shear failure from the development of the oblique cracks in the wall to the concrete spalling in the compression zone; The reduction of the axial compression ratio or the reinforcement rate of the longitudinal reinforcement of the edge members will lead to the reduction of the bearing capacity of the shear wall and the increase of the ultimate displacement has a negative impact on the seismic performance of the new assembled shear wall, which is manifested by the weakening of the hysteresis performance and the reduction of the ultimate bearing capacity. Combined with the finite element simulation results, the five-fold skeleton model and restoring force model of the new assembled shear wall were established, and then the calculation formulae of unloading stiffness and loading stiffness of the hysteresis curve were obtained by regression fitting. The restoring force model proposed in this paper is in good agreement with the test results, which can provide a reference for the elastic–plastic seismic response analysis of the new fabricated shear wall structure.

Stability bearing capacity of concrete filled steel tubular columns subjected to long-term load

Concrete-filled steel tube (CFST) are commonly used in modern building and bridge applications. Despite their popularity, studies on the investigation of the influence of long-term load on the stability bearing capacity of such elements are scarce. This study investigates how the key parameters including slenderness ratio (λ), axial load ratio (m), and eccentricity ratio (e/r) affect the stability bearing capacity of a CFST column under sustained load. Twenty three CFST columns were fabricated to investigate the effect of long-term load on the stability bearing capacity. Fourteen specimens were subjected to constant compressive loading for 462 days and then tested for failure. The remaining 9 were companion load-free specimens. A three-stage finite element method was used to predict the stability bearing capacity after creep. The results indicate that the stability bearing capacity of CFST columns decrease after being subjected to long-term load. Both the experimental and numerical results indicated that the load of steel tube for long-term load specimens reaching up to the elastic–plastic and plastic process was lower than that of the load-free specimens. Moreover, the corresponding strain of the creep specimens was greater than that of the load-free specimens when the member reached the maximum load. Benchmarking analyses have shown that the creep reduction coefficient (kcr) proposed for CFST columns can be used to predict the reduction of stability bearing capacity after creep. Furthermore, a collected database comprising 49 CFST specimens subjected to long-term load was used to investigate the proposed formulae for kcr. The results show that the formulae were consistent with the experiment results.

Monitoring of soil water content using spherical smart aggregates based on electromechanical impedance (EMI) technique

Real-time monitoring of soil water content is of great significance to prevent many engineering accidents, such as landslide, water seepage of foundation dam, and reduction of foundation bearing capacity. Electromechanical impedance (EMI) technique based smart aggregates (SAs) have showed excellent monitoring capability in various engineering applications. However, there are limited reports on the application of EMI based SAs in the monitoring of the soil water content. In this paper, the EMI based spherical SAs (SSAs) were investigated in the monitoring of soil water content. Firstly, the SSAs were designed and fabricated using the monolithic concrete encapsulation method, and their stable performance in air were evaluated, and confirmed by testing and analyzing the impedance spectrum. Then, the fabricated SSAs were immersed in the water environment for 28 d to ensure the stability under the working conditions, such as the soil with high water content and the hydration process of early-age concrete. Secondly, the monitoring experiments of soil water content were carried out based on the SSAs and the traditional SAs using the EMI technique. The measured impedance signatures under different water contents in soil were quantified by three types of statistical indexes, including root mean square deviation, mean absolute percentage deviation, and correlation coefficient deviation. The experimental results show that compared with the traditional SAs, the SSAs are more sensitive and stable to monitor the soil water content. Finally, the effect of temperature on the performance of SSA based on the EMI technique were conducted experimentally. The results demonstrate that temperature has influence on the monitoring results of the SSAs based on the EMI technique.

Experimental Study on the Wear Characteristics of Textured Joint Surfaces under Bionic Lubrication

Ti15Mo7Zr15Ta1.00Si titanium alloy contained higher concentration of silicon and better elastic properties, excellent biocompatibility and lower processing cost. To investigate the influence of texture shapes and parameters of joint surfaces on the friction and wear properties under bionic lubrication conditions, three types of texture morphologies (circular, elliptical, and equal-width grating) with the same pit depth and surface coating rate were processed on a Ti15Mo7Zr15Ta1.00Si titanium alloy using a picosecond laser processing system in this study. Then, the "ceramic–metal" friction and wear tests of textured and smooth samples under lubrication with bovine serum protein were performed using a UMT-3 multifunctional friction and wear testing machine. The results showed that the surface micro-texture morphology could improve the anti-friction properties of titanium alloy artificial joint materials. The wear resistance of the circular micro-dimples improved with an increase in the circular diameter. In the elliptical micro-dimple texture morphology, the vertical arrangement of the ellipses could provide the maximum bearing capacity and best friction reduction effect, followed by the elliptical morphology and the transverse ellipse arrangement. The denser the arrangement of the equal-width bars, the better the friction reduction effect was.

Analytical model of skin friction for bored pile socketed into weak rocks in ice-rich permafrost regions

Bored piles constructed in permafrost regions often need to be socketed into weak and weathered rock strata, such as marl stratum. When these strata are ice-rich, the meltwater caused by construction will form an ice film at the pile-rock interface during refreezing, leading to a reduction in pile bearing capacity. By analyzing the shear mechanism of pile-rock interface with ice film, an interface shear model was proposed in this paper. Based on this model, the load transfer analytical method of rock-socketed bored piles was improved. Finally, the effects of pile-rock interface roughness, ice filling degree, and residual friction angle on skin friction were analyzed. The results show that the shear stress-displacement curve of the ice-containing interface unit exhibits two peaks and can be divided into four stages: ice film shear stage, ice film extrusion stage, concrete-rock relative sliding stage, and interface residual sliding stage. Increasing either the dilation angle or half-wavelength can improve the interface's shear resistance when only one variable is altered. Furthermore, the peak shear strength of the interface decreases as the filling degree increases. The interface residual shear stress is positively correlated with both the residual friction angle of weak rock (ϕu−r) and ice (ϕi−r), and increasing the proportion of ice in the residual sliding surface will lead to the reduction of residual shear stress.