Results Of Static Tests Research Articles

Shear behavior at the interface of rough surfaces and cohesive soils under axial loading

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens’ preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

Study on construction technology and bearing mechanism of pressure cast-in-situ pile with spray-expanded frustum

The pressure cast-in-situ pile with spray-expanded frustum (PCPSF) is a new type of pile developed by the last author, which is composed of pile body, ribbed plate and expanded body with double-frustum. This paper presents the equipment used to produce the PCPSF and the spray-expansion extrusion vibration and pressure method used for construction of the PCPSF. The PCPSF model of cement soil transition layer around pile is built with finite element software. The accuracy of the numerical calculations is verified through a comparison with the results of static load tests conducted on PCPSF. Furthermore, the impact of the expanding ratio, expanded body location, and ribbed plate length on the response of the PCPSF is investigated. The results show that: (1) the ultimate bearing capacity (UBC) of PCPSF single pile is proportional to the diameter expanding ratio and the length of the ribbed plate; (2) the improvement of the bearing capacity of single cubic concrete of PCPSF decreases with the increase of expanding ratio; (3) the bearing capacity of expanded body can be activated ahead of time as it advances up in position, and there is a trend toward a steady increase in the combined bearing capacity of the expanded body and pile end; (4) as the expanded body moves up, the vertical stress of the soil below pile tip decreases, the rate of decay of additional stress is accelerated; (5) under the identical circumstances, the PCPSF's bearing capacity is 1.5 times greater than the traditional cast-in-place pile's, and the presence of cement soil transition layer contributes 15 % of the lateral resistance of the PCPSF.

Effects of electron beam and atomic oxygen irradiation on hypervelocity - Impact tested / polyimide coated carbon fiber-reinforced plates

In a low-Earth orbit, space debris orbit at approximately the first cosmic velocity. When space debris strike a spacecraft, ejecta (fragments) from the spacecraft are widely scattered. The reduction in the number of ejecta (fragments caused by impact) must also be considered when selecting spacecraft materials. The authors’ group has previously examined the size of ejecta (fragments) and reduction in the number of ejecta. In general, the mechanical properties of polymer materials and CFRP plates may be damaged by space environments, such as radiation (gamma rays and electron beams (EBs)), atomic oxygen (AO), ultraviolet rays, temperature, and thermal cycling. The authors suggested an anti-AO coating/polyimide CFRP as a material resistant to space environments. The effects of EB and AO irradiation on the fracture behavior and ejecta of anti-AO coating/polyimide CFRP were examined for hypervelocity impacts. The results of static three-point flexural tests were compared with the fracture behavior and ejecta. A two-stage light-gas gun was used for the impact tests. Spherical projectiles formed of aluminum alloy 2017-T4 with a diameter of 1.6 mm were used. Photographs of the ejecta scattered in front of each polyimide CFRP plate were captured from the side using a high-speed video camera. The number and weight of the ejecta on the front side and perforation holes were examined.

Salt-freeze resistance and life prediction of geopolymer recycled concrete mixed with rice husk ash and modified rubber particles

Rice husk ash (RHA) and Span-40 modified waste rubber particles (WRP) were mixed into geopolymer recycled concrete (GRC) to improve its frost resistance in normal and chlorine environment. The freeze-thaw and static loading test results show that GRC has the best freeze-resistance when 5 %RHA and 10 %WRP are added. The strength loss rate of GRC after 200 freeze-thaw cycles in normal environment and chlorine salt environment is 8.3 % and 8.8 % lower than that of GRC without RHA and modified WRP, respectively. Based on the test results, the material damage model and strength loss model of GRC doped with RHA and modified WRP were established. The failure probability and service life of GRC were predicted. The results showed that the failure probability of GRC mixed with 5 %RHA and 10 %WRP was reduced by more than 10 % compared with that of GRC mixed with no RHA and modified WRP at 200 freeze-thaw cycles under normal environment and chlorine salt environment, and the failure probability decreased with the increase of cycle times. The life prediction results showed that the service life of GRC mixed with 5 %RHA and 10 %WRP increased by 17.9 % and 21.6 %, respectively, compared with that of GRC mixed with no RHA and modified WRP under the freeze-thaw cycle of normal environment and chlorine salt environment.

FLEXURAL STRENGTHENING OF THERMALLY MODIFIED RUBBERWOOD GLULAM BEAMS WITH FRP UNDER STATIC AND CYCLIC LOADS

The purpose of this research is to investigate the flexural properties and cyclic response of strengthened with fiber reinforced polymer (FRP) of glulam beam made from thermally modified rubberwood. The efficiency of three different FRP was assessed based on the bonding properties. The experimental results demonstrated that the glass fiber-reinforced polymer (GFRP) showed the strongest adhesion. Static and cyclic flexural tests were also carried out to study the behavior of glulam beams. The static test results indicated that double sides strengthened glulam beam enhanced their flexural strength. The strengthened glulam beams under static load demonstrated a reduced deformation rate due to increased modulus of rupture compared to non-strengthening glulam beam. The cyclic load test showed the strengthening effect on improving energy dissipation and ductility, while the impairment of strength did not affect.

Research on the Vibration Fatigue Characteristics of Ancient Building Wood Materials

In this study, we selected ancient building timber as the research object. A series of static load tests were conducted to analyze the different performances of timber under tensile and compressive loads. After that, vibration fatigue tests on ancient timber samples were carried out under different upper limit stress ratios. Finally, a dynamic constitutive model of ancient timber was established based on the Ramberg–Osgood model. The static load test results show that the tensile strength was approximately 80% of the compressive strength. Meanwhile, the samples that failed under compressive pressure had obvious residual strength, and their failure strains were also much larger than those under tensile stress. In the vibration fatigue tests, the stress–strain curves were analyzed and the results showed that the curves displayed a trend moving to sparse from dense during the loading process. Meanwhile, the curves moved right with the increase in the upper limit stress ratios. The relationship between axial strain and the number of cycles appeared to be characterized by a three-stage form, i.e., damage occurrence, damage expansion, and damage penetration, and this relationship was formulated by a nonlinear function model. Finally, a dynamic constitutive model with high accuracy in describing the vibration fatigue characteristics of ancient timber was established by converting constant parameters to the variable parameters of the Ramberg–Osgood model.

Graph-Analytical Method for Calculating Settlement of a Single Pile Taking into Account Soil Slippage

Most of the existing methods of pile settlement calculation, including normative methods, do not fully take into account the processes occurring in the soil when loads are transferred to them and the changes in the properties of the contact zone soils. This leads to underutilisation of the bearing capacity of the soil, and the calculated settlement value may differ several times from the real values. In this paper, a graph-analytical solution to the problem of interaction of a single pile with a three-layer soil foundation is proposed to determine the settlement, taking into account the complex nature of the pile operation and the processes occurring in the soil when loads are transferred to them. The proposed method allows to use the non-linear behaviour of the soil on the lateral surface and under the tip of the pile, the possibility of its detachment and slippage after reaching the ultimate strength of the soil, changes in the properties of the contact zone soils, and the load distribution on the pile between its lateral surface and the tip. To verify the proposed graph-analytical solution, a comparative analysis was performed with the numerical method in the Plaxis 2d software (version 21.00.01.7) and with the results of static tests of piles at the construction site. To determine the strength reduction factor at the contact of soils with concrete, laboratory tests were carried out on a direct shear apparatus. Based on the results of the performed calculations, graphs of the dependence of settlements on loads were plotted, conclusions were drawn about the possibility of using the graph-analytical method, and prospects for further development and improvement of the graph-analytical method were proposed.

Installation of a Pit Fence in Cramped Conditions

The construction of buildings and structures in cramped conditions requires a special approach from hydraulic engineers and builders, requiring the preservation of the surrounding development in a working condition. This circumstance requires a geotechnical forecast of deformations of objects falling into the zone of geotechnical influence of the construction of a building under construction at the design stage and then the organization and implementation of geotechnical monitoring of deformations as a result of construction and installation work. It should be noted that the objects of the surrounding development can be in different categories of technical condition. According this circumstance the permissible deformations may be different. In any geotechnical case, there is an urgent need to install excavation fences that perform a dual task: both ensuring the stability of the soil walls, and reducing the impact of the new construction object on existing buildings. The determination of the bearing capacity of the enclosing structures of the excavation, especially the retaining soil anchors themselves, is of great importance in modern geotechnical construction. The engineering method used in this article to determine the bearing capacity of drilling-injection anchors with sufficient accuracy for technical calculations showed the convergence of calculated and real values based on the results of static tests.

A comparative study of self pierceing riveting and mechanical clinch of DP590-Al5754 high-strength steel and aluminum alloys

This paper presents a comparative study of two joining processes, self piercing riveting (SPR) and mechanical clinch, used to join DP590 high-strength steel and Al5754 aluminum alloy. A comparative study of microhardness, tensile shear properties, fatigue properties, and economics of joints from both processes was conducted. The findings indicate that the highest hardness levels are observed in the rivet leg region for SPR joints and in the neck region for mechanical clinch joints. The maximum failure load and energy absorption values of SPR joints were found to be 1.46 and 9.07 times higher, respectively, than those of mechanical clinch joints. The static tensile test results demonstrate that the strength and hardness of SPR joints in aluminum sheets subjected to cold work hardening are significantly lower than those of steel sheets. Therefore, the failure of SPR joints is primarily attributed to the deformation and fracture of the lower aluminum sheet. Mechanical clinch joints fail by neck fracture because the steel sheet neck becomes brittle by cold work hardening and the neck thickness is small. The fatigue behavior of SPR joints was observed to be superior to that of mechanical clinch joints. The findings of the scanning electron microscopy and energy spectrum analysis suggest that fretting wear between the upper and lower sheets results in fatigue fracture of the lower sheet in the joints. When joining the same material on a large scale, the selection of mechanical clinch over SPR can prove an effective method of reducing costs. Furthermore, the selection of a set of dies with an extended life can contribute to the reduction of joining costs.

Influence of gate cutoff effect on flow mode conversion and energy dissipation during power-off of prototype tubular pump system

Understanding the cutoff effect of gates is essential for enhancing the overall quality of the pump system's power-off process, minimizing energy losses, and reducing potential risks associated with hydraulic transients. In this study, both numerical simulations and experimental investigations were conducted on the power-off process of a tubular pump system, considering scenarios with and without gate functionality. The simulations utilized a dynamic mesh method to model gate movement, incorporated the torque balance equation to determine the real-time impeller speed, and applied the 3D-VOF method for free surface modeling in reservoirs. Power-off experiments were performed on a model pump system and a prototype pump system to validate the numerical simulation results. To elucidate the mechanism of the gate's cutoff effect, flow modes during the power-off process were categorized based on the four-quadrant static test results of the pump, revealing the deviations between transient and static characteristics. By comparing the transient flow structures of the pump system under different gate operating states, specific energy dissipation behaviors during gate cutoff were analyzed. The research findings enhance the understanding of hydraulic transients, which is essential for developing more sustainable and resilient energy systems.

Parameter determination of Johnson–Holmquist–Cook constitutive model and calibration for Indiana Limestone

In this study, a comprehensive parameter determination procedure for the Johnson–Holmquist–Cook (JHC) constitutive model is introduced, including calibration and validation processes for Indiana Limestone rocks. The procedure is conducted utilizing the existing physical and mechanical properties of Indiana Limestone. To obtain an accurate set of parameters for the JHC model for Indiana Limestone, an extensive dataset comprising mechanical and physical properties of Indiana Limestone rocks was initially compiled. The static mechanical tests incorporated uniaxial compression, triaxial compression, direct tensile, and uniaxial strain data, while the dynamic mechanical test data was primarily derived from the Split Hopkinson Pressure Bar experiments. Subsequently, the JHC constitutive model parameters were determined using existing literature data, employing statistical analysis, theoretical derivation, and numerical back analysis techniques. One of the damage parameters was determined through numerical post-peak behavior calibration of triaxial compression strength test results on experimental data. Finally, the accuracy of the determined parameters was validated by comparing the numerical and experimental results of both static and dynamic tests. This study effectively addresses the challenges associated with the numerical method using the JHC material model, such as the complex parameter determination process and the costly required tests, thereby preserving the efficiency and applicability of the numerical method.

Research on the vertical compressive bearing characteristics of offshore wind power steel pipe piles

In the absence of a comparison of static load test results for large-diameter steel pipe piles at home and abroad, optimize the design parameters based on the test pile results to guide later construction. This paper is based on the pile foundation design calculation method of API specification, as well as the relationship between the t-z, Q-z, p-y curve modes suggested by this specification, vertical ultimate bearing capacity, and stratum parameters. The conclusions and results obtained are limited to pile foundation calculations using API specifications. Analyze and back-analyze the results of static load tests on large-diameter steel pipe piles, and verify the pile foundation parameters. Combined with the data obtained from the test pile tests, analyze the stratum parameters to guide the optimization design of pile foundations in the construction drawing design stage of the offshore wind farm expansion project.

Total stress model of clay considering small strain characteristics

Saturated soft clay has the characteristics of high compressibility, low strength, and high structural sensitivity. Its small strain characteristics have a significant impact on the deformation development and long-term bearing capacity of ocean engineering foundations. A total stress model for undrained cyclic loading of clay considering small strain characteristics was created based on the Overlay model. The proposed model was used to simulate the static or dynamic triaxial test results of over consolidated Chicago clay, remoulded normally consolidated Georgia kaolin, and normally consolidated clay Malaysia kaolin, respectively. The results verified that the model can simulate the static shear characteristics of clay. The model can also simulate the weakening of soil strength and strain accumulation under cyclic loading, and is suitable for analyzing the response of ocean engineering foundations under long-term cyclic loading.

Pile–Soil Interaction during Static Load Test

Abstract This study highlights the possibility of determining the shear stress distribution along the skin of a pile, which represents skin resistance. Geotechnical engineering is plagued by the challenge of designing appropriate piles as a sufficient foundation construction while being economically justified solution. Static load testing facilitates verification if the pile satisfies these requirements. In most cases, the pile skin resistance is undervalued. This study first introduces the general approach based on static load test results using an appropriate mathematical approach in the presence of linear, vertical shear stress distribution boundary conditions as well as phenomena such as pile shortening and Kirchhoff's principle. Moreover, a scientific approach for pile compression and shear stress distribution is presented. Further, the study expands upon previous work by applying mathematical calculus to displacement piles. The promising results indicate that further work on greater number of piles may lead to a better understanding of pile–soil interaction and a more accurate design process.

A highly efficient molecularly imprinted fluorescence sensor for selective and sensitive detection of tetracycline antibiotic residues in pork

Tetracyclines (TCs) residues in animal-based foods may cause consumer poisoning or allergic reactions, as well as resistance of pathogenic microorganisms. Therefore, a method to accurately monitor TCs is urgently needed. Here, a sensitive and greenificated molecularly imprinted fluorescent sensor (CDs@MIP) for detecting TCs residues using non-covalent imprinting binding method has been synthesized in a simple and safe manner. The sensor was demonstrated to contain specific adsorption sites and high adsorption capacity by static adsorption test results and Freundlich and Langmuir model analyses, and the maximum adsorption capacity was 45.8 mg/g. Moreover, the sensor exhibited intense blue-green fluorescence under UV light, and the fluorescence was gradually quenched as TCs was adsorbed to achieve the detection. The fluorescent spectrum experiment demonstrated that the prepared sensor has good recognition and detection performance for TCs with a linear range of 0.02–50 mg/L and a detection limit of 0.18 μg/L. Furthermore, This sensor is recyclable and can be used to determine TCs content in pork with a recovery rate of 98 %–108 %. Therefore, the constructed sensor provides a new convenient strategy for detecting TCs residues.

Assessment of Liquefaction Potential by Comparing Semi-Empirical Methods Based on the CPT Test

Abstract Liquefaction is a dangerous and temporary phenomenon whereby water-saturated soil loses all or part of its strength. Undrained conditions associated with cyclic loading increase water pressure in soil pores, thereby reducing effective stress. The aim of this study is, on the one hand, to report on the phenomenon of liquefaction of sand, clay and silt deposits in more or less water-saturated zones in the section located at the heart of the central alluvial plain of the Oued Sebou in the mio-plioquaternary Gharb basin and, on the other hand, to study the ability of semi-empirical methods to correctly assess liquefaction potential, while specifying the most appropriate method for the area studied. The study is based on data from experimental results of static penetrometer tests between the Mnasra - Ouelad Salama zone in the Oued Sebou alluvial plain of Morocco's mio-plio-quaternary Gharb basin, made up of sandy, sandy-clay, sandy-silt and silty-sandy formations, which are more sensitive to liquefaction due to their saturation and grain size. We present and discuss the results of Olsen's method, Juang's method and Robertson's method, which are based on the CPT static penetrometer test, as well as looking at the impact of dynamic loading and soil structure on liquefaction probability index values.

Influence of precast microbial reinforcement on lateral responses of monopiles

Microbially Induced Calcium Carbonate Precipitation (MICP) provides an environmentally friendly solution for reinforcing large diameter monopiles for offshore wind turbines (OWTs). This study presents an investigation into the lateral responses of monopiles with precast microbial reinforcement using a low-pH one-phase method. Both static and cyclic loading tests were carried out. The results of static loading tests show that the failure mode of the bio-reinforced monopile was an overall overturn failure. The lateral bearing capacity was increased by 50% and the bending moment was reduced by about 25% with the bio-reinforcement. Further investigation was conducted on the secant stiffness, damping ratio, and accumulated deformation of the bio-reinforced monopile under various cyclic loadings. With the bio-reinforcement, the accumulated deformation under one-way cyclic loading can be reduced by 30%–60%. The influences of cyclic loading parameters and loading sequence on pile stiffness were clarified. The growth ratio of pile stiffness due to bio-reinforcement under one-way loading was between 1.65 and 2.82, and decreased with increasing load amplitude. The ratio was smaller under two-way loading. Three competing factors on pile stiffness were identified: cyclic compaction of the unreinforced sandy soil, weakening of the bio-reinforced soil and soil subsidence around the bio-reinforced soil.

Utilizing wave propagation techniques to determine the influences of the type and size of coarse aggregates on the elastic properties of concrete

The results in the literature are not conclusive regarding the relationships between the strength of concrete and the particle size and type of coarse aggregates used in concrete production. Furthermore, few studies have used wave propagation to analyse these relationships. Therefore, this research used ultrasonic and static compression tests to evaluate the influences of these factors on the elastic parameters of 81 concrete test specimens produced with two maximum sizes of conventional coarse aggregates (9.5 mm and 12.5 mm) and lightweight aggregates (expanded clay). The ultrasonic testing results showed that the elastic parameters (longitudinal elastic modulus (E) and transverse elastic modulus (G)) were influenced by the type and size of the coarse aggregates; these influences were not detected in the static compression testing results. The results of the ultrasonic and static compression tests showed that the Poisson ratio was not influenced by the type or size of the coarse aggregates.

Mitigation of Effect Modification by Psychological Status in Patients With Hearing Loss

Although patient-reported outcomes provide valuable insights, these subjective data may not align with objective test results. Hearing loss is a pervasive problem, such that concordance between subjective perceptions of hearing ability and objective audiogram assessments would be beneficial. To determine (1) whether psychological status is an effect modifier of the association between subjective patient reports of hearing ability and objective audiometry results, and (2) whether any effect modification observed in standard static questionnaires would be either mitigated or exacerbated by adaptive testing based on Item Response Theory analyses. This diagnostic study at a tertiary care center and community-based practice included consecutive adults who presented with queries related to hearing loss. Participants were recruited and enrolled and data analyses occurred from 2022 to 2024. Participants prospectively reported their hearing-specific abilities through either a standard static or adaptive version of the Inner Effectiveness of Auditory Rehabilitation (EAR) scale, alongside validated measures of their mental health and audiometry. Word recognition scores (WRS) and pure tone averages (PTA) were used to analyze audiometric testing. The association between subjective Inner EAR results and audiometry was evaluated. Stratified analyses were used to assess for effect modification by psychological status. The results of standard static and adaptive testing were compared. In this study of 395 patients (mean [range] age, 55.9 [18-89] years; 210 [53.2%] female), standard static Inner EAR mean scores were appropriately higher in patients with higher (better) WRS (50.7, 95% CI, 46.4-54.9), compared with patients with lower (worse) WRS (34.7, 95% CI, 24.3-45.1). However, among patients with worse mental health, there was no association between standard static Inner EAR scores and WRS. In contrast, adaptive Inner EAR mean scores were significantly higher for those with better WRS, regardless of mental health status. Thus, effect modification was observed in standard static assessments, whereas adaptive testing remained durably associated with audiometry, regardless of mental health. Psychological status was an effect modifier of the association between standard Inner EAR scale scores and audiometry, with a positive association observed only in those with better mental health. Adaptive testing scores, however, remained significantly associated with audiometry, even when mental status was worse. Adaptive testing may stabilize the association between subjective and objective hearing outcomes.

О НЕОБХОДИМОСТИ УТОЧНЕНИЯ РАСЧЕТНОЙ МЕТОДИКИ ОЦЕНКИ ПРЕДЕЛОВ ОГНЕСТОЙКОСТИ МЕТАЛЛИЧЕСКИХ КОНСТРУКЦИЙ С УЧЕТОМ ПРОДОЛЖИТЕЛЬНОСТИ ИХ ЭКСПЛУАТАЦИИ

The paper discusses the issue of estimating the fire resistance limits of metal structures taking into account the duration of their operation. The results of the study of the influence of the duration of operation on the mechanical characteristics of steel structures, such as the ultimate strength, the yield strength and the relative elongation are presented. The study was conducted on a steel structure with a service life of more than 80 years. The results of static tensile mechanical tests showed that the ultimate tensile strength for the steel specimens in question is at a minimum level (a decrease in ultimate strength of 10–15 % or more). The conceptual opinion about the necessity of taking into account the change of strength and yield strength when assessing the fire resistance limits of steel structures of different service life has been expressed.