Coupling Effect Of Load Research Articles

The impact of seepage effect on repaired interface failure in steel bridge deck pavement: A case of pothole distress

The repeated failure of repaired interface in steel bridge deck pavement (SBDP) under complex service environment makes SBDP maintenance challenging. The primary objective of this paper was to figure out the impact of seepage on repaired interface failure, addressing the secondary damage on SBDP after distresses maintenance. A uni-body bi-material structure (UBS) specimen was fabricated to simulate the repaired interface. Besides, a simulation experimental device of hydrodynamic scouring action was put forward to evaluate the effect of cycle numbers on failure behavior of repaired interface during an indirect tensile test. In addition, numerical simulation analysis was conducted to determine the tensile stress characteristics of repaired interface under load-seepage coupling effect. Findings revealed that the failure state of repaired interface may change from brittle fracture to large deformation damage under seepage effect. The longer the duration of hydrodynamic scouring action, the more serious damage of the repaired interface, with 540 cycles resulting in an approximately 25 % reduction in interface strength. Furthermore, the stress condition of repaired interface is significantly worse when consider the coupling effect of load and seepage, approximately 40 % greater than that of a single load action. And it is closely related to its relative position with the orthotropic steel bridge deck and the actual stress conditions. The research findings presented in this paper can serve as a theoretical foundation for SBDP maintenance.

Simulation study of the rupture mechanism of through-cracking under freeze–thaw load coupling effect

Simulation study of the rupture mechanism of through-cracking under freeze–thaw load coupling effect

Application of Mode Superposition Method in the Recoil Response of Deepwater Drilling Risers after Emergency Disconnection

Summary How to effectively control the recoil response after an emergency disconnection is one of the core technical problems in ensuring the safe and reliable operation of a deepwater drilling riser. Currently, the theoretical analysis is based on a discretization model or numerical simulation, which ignores the continuity of the riser system and the coupling effects of load acting on the riser. To address this problem further, in this paper, we establish a mechanical model and control equation with infinite degree of freedom for riser recoil response, where the heave motion of the floating drilling platform, seawater damping, and the viscous resistance of drilling fluid discharge were taken into account. In addition, the correctness of the model and solving approach are verified against the Orcaflex software. On this basis, the influence of wave period, wave height, initial phase angle, and tension coefficient on the recoil characteristics are discussed. The success of riser emergency disconnection is related to the clearance between the lower marine riser package (LMRP) and the blowout preventer (BOP) and the axial force distribution of the riser. The influence of the above-mentioned factors on the riser recoil response is also complicated. On the basis of the assumptions put forward and the model established, some quantitative conclusions are drawn. This study is of reference significance for safety control of riser emergency disconnection operation.

Structural layer applicability of semi-flexible material for rutting resistance: A coupled temperature-mechanical approach.

Semi-flexible material (SFM) is produced by pouring cement grouting material into the asphalt concrete skeleton. It exhibits both characteristics of cement and asphalt, increasing structural stiffness and reducing rutting. Extensive studies have shown that the temperature load coupling effect is one of the leading causes of road rutting. However, few researchers focused on the anti-rutting impact and structural layer applicability of SFM under this effect. Thus, a coupled temperature-mechanical approach was developed based on the finite element (FE) method to simulate the rutting of SFM at different pavement layers and times of the day. During simulation, both standard load and overload were applied to the FE model of pavement. Asphalt mixture and SFM specimens were prepared for essential road performance and dynamic modulus testing. The mechanical properties of SFM and asphalt mixtures at different temperatures were obtained based on the measured data. The structural layer applicability of SFM was revealed by simulating the response of the pavement structure under the combined action of temperature and load. An accelerated pavement test (APT) based validation indicated that the simulation results were accurate. The results show that traditional asphalt pavement and pavement with SFM at the surface and bottom layers tend to exhibit dilative heave adjacent to the wheel load. Using SFM at the middle layer shows a compacted rutting mode, and the pavement has a minimum rise of 51% in rutting depth under the double overloading compared with the pavements with SFM in other layers. It implies that using SFM in the middle layer gives optimal resistance to overload. Considering the depth, form, and resistance of rutting, the SFM in the middle layer of pavement can functionally exert its anti-rutting characteristic.

Creep and strength characteristics of cemented gangue backfill under coupling effect of load and acid corrosion.

Cemented gangue backfill technology is beneficial to the reuse of solid waste and sustainable economic development. However, mine water has a great impact on the strength and deformation of cemented gangue backfill (CGB). In this study, the CGB specimens under load were placed in simulated acid mine water (H2SO4 solution). The changes in deformation, resistivity, and ultrasonic pulse velocity (UPV) of CGB were monitored. On the 360th day, the stress-strain curve and acoustic emission (AE) energy of the specimen during loading were recorded. The degradation mechanism of CGB was discussed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the deformation of CGB increased with time. The effect of H2SO4 solution concentration on the deformation was different in the early and late stages. Applying an 80% stress-strength ratio (SSR) reduced the strength and increased the deformation. The UPV and resistivity had different characteristics at different corrosion ages, which could be used for long-term stability monitoring of CGB. The CGB showed the strongest AE energy characteristics near the peak stress. The AE energy decreased with the increase of pH value in the pore compaction stage, and the AE activity of the CGB under 80% SSR was much greater than that of the CGB under 40% SSR. The erosion of the H2SO4 solution on the CGB was inhibited by applying a small load. Excessive load aggravated the erosion deterioration of CGB due to initial plastic damage. The research results can provide a reference for the durability design of CGB.

Experimental study of the coupling effect on segmental shield tunnel lining under surcharge loading and excavation unloading

Surcharge loading and excavation unloading are two common engineering disturbances affecting the adjacent tunnel in congested urban areas. The coupling effect on segmental shield tunnel lining under loading and unloading conditions is still unclear. In this paper, physical model tests conducted in 1-g plane strain conditions were designed and performed to study the coupling effect of loading and unloading on shield tunnel. The results show that the response of segmental shield tunnel linings will be significantly amplified under the coupling conditions compared with the individual disturbance. A coupling effect index was proposed to evaluate the coupling degree of different disturbances. The classification was also presented, divided into favourable, zero, and unfavourable coupling effects. The tunnel response has a more significant coupling effect in the case of loading first and unloading later. There is a coupling amplification effect of 128% and 144% for the tunnel horizontal convergence and the springline near the excavation.

Evolution characteristics and mechanism of concrete performance under water pressure environment: A comprehensive review

AbstractCompared with the ground service environment, the evolution of concrete performance under a water pressure service environment is quite complex with variable conditions. Because of the coupling effect of load and pressure, water has a special impact on the strength and deformation of concrete. Meanwhile, harmful ions usually react with the cement matrix as pressure water seepages into concrete, resulting in the reduction of concrete durability. Based on this, this study provides a comprehensive review of the strength, deformation, and durability of concrete under water pressure environment. It is found that microcracks in concrete tend to propagate and connect after exposure to water pressure, leading to a decrease in strength and deformation performance. The average loss rate of strength and elastic modulus increased by 12.15% and 10.97%, respectively, when water pressure increased by 1 MPa. However, the loading process of water‐confining pressure makes concrete more compact, where the static and dynamic mechanical performance can be improved. Besides, due to the enhancement of excess pore water pressure, concrete strength under a high strain rate increases by 61.79% compared to static load. The effect of water pressure increases the ability of the liquid to penetrate concrete, and corrosive ions trapped within the liquid and freeze–thaw caused by external temperature changes would further reduce the concrete durability. This study points out that static and dynamic loading characteristics and durability of concrete under multi‐factor coupling in a water pressure environment will be the future research direction. The summarized contents can provide guidance for construction and research of concrete engineering under a water pressure environment.

An area-variant type MEMS capacitive sensor based on a novel bionic swallow structure for high sensitive nano-indentation measurement

In this paper, a high sensitive area-variant type MEMS capacitive sensor was proposed for nano-indentation measurement. The proposed bionic swallow structure processed a high mechanical sensitivity without influences from the load coupling effect. Six comb arrays were optimized and integrated into the proposed sensor with a novel comb sensing configuration for eliminating electrostatic interferences resulting from multiple combs and maintaining compact chip size. Based on the proposed micro-machined process, comb arrays have been fabricated with great consistency, which exhibited a static differential output of 0.0554 pF. The fabricated sensor has been characterized with rigid glass cube and AFM cantilevers, and the measured force sensitivity can reach 98.54 aF/nN for a larger measurement range of 142 µN with a linearity of 0.9996. The fabricated sensor also exhibited a high resolution of 0.9819 nN, indicating its great feasibility in nano-indentation measurement at the sub-nano-Newton level.

Load–Temperature Coupling Effect on the Base Plate End of the Whole Tram Road

Although trams have been widely recognized, systematic and comprehensive research on their design and construction is lacking. Based on the ABAQUS finite element software, we constructed a three-dimensional finite element analysis model of the overall track bed of the tram. Taking the most unfavorable working condition of load and temperature coupling as the research object, that is from 5:30 to 6:00 a.m., the load was applied to the plate end position. The simulation experiments were carried out by selecting different thicknesses of the track bed slab, support layer thickness, contact conditions between the track bed slab and the support layer, the modulus of the track bed slab, the modulus of the support layer and the soil foundation strength, and the stress and deflection of the subgrade were calculated. The most unfavorable load–temperature coupling condition was taken as the research object, that is, applying a load of 5.5–6 points on the plate end. Different track bed slab thicknesses, support layer thicknesses, contact conditions between track bed slab and support layer, track bed slab moduli, support layer moduli, and foundation strengths were utilized to conduct simulation tests for calculating the stress and deflection of the subgrade. Under the coupling effect of load on the end of the slab and the effect of temperature, changing the thickness of the track bed slab and the coefficient of friction between layers can improve the lateral force and deflection of the track bed slab. The effect of deflection is small. Changing the thickness of the support layer has an insignificant effect on the stress on the top surface of the soil foundation and the deflection of the top surface of the subgrade. The modulus of the track bed slab can affect the lateral force and deflection of the track bed slab, but it only slightly affects the longitudinal force and deflection of the track bed slab and the longitudinal and lateral force and deflection of the soil foundation. The modulus of the supporting layer only slightly affects the vertical and horizontal force and deflection of the track bed slab and soil foundation. The soil foundation modulus has the greatest influence on the vertical and horizontal forces and deflection of the track bed slab and soil foundation.

Fracture analysis on periodic radial cracks emanating from a nano-hole with surface effects in magnetoelectroelastic materials

In this paper, the fracture behavior of multiple radial cracks with periodic and uniform distribution around a nanoscale circular hole in a magnetoelectroelastic (MEE) solid is studied under anti-plane mechanical load, in-plane electric displacement load and magnetic induction load. Based on the surface elasticity theory, the analytical solutions of the MEE fields distribution and the MEE fields intensity factors at the crack tip are obtained by using the conformal mapping method, the boundary value theory of analytic function and the basic theory of MEE elastic solid. Considering that the defects are piezomagnetic phase or piezoelectric phase, size effects of the defects, cracks number, geometric parameters and applied MEE loads on the MEE fields intensity factors at crack tip are discussed. The size effect, interference effect and multi-fields load coupling effect of the MEE tip fields are studied in detail.

The effect of thermal consolidation on bearing characteristics of static drilling rooted energy pile

Static drilling rooted energy pile is a new type of energy pile technology recently developed and promoted in soft soil areas. This technology has the advantages of green, low-carbon and good heat exchange effect. But its related basic theoretical research is still lacking. Therefore, the physical model of the static drilling rooted energy pile is deduced. The thermal consolidation settlement process of the soil around the pile is analyzed firstly based on one-dimensional thermal consolidation theory. And, the load transfer method is combined to derive the pile circumference under the coupling effect of load and temperature variation. The governing equations for frictional resistance and pile deformation are deduced and solved with numerical programs. Then an actual engineering case with static drilling rooted energy pile in soft soil area is calculated and analyzed. The results show that the temperature increase of the surrounding soil increases the relative displacement of pile and soil, which resulting in a decrease in the upper side friction resistance and an increase in the lower side friction resistance; and this effect will be enlarged during the cooling stage. The maximum axial addition stress caused by the temperature variation reaches 75.4% of the stress by load, so the influence of temperature changes on the bearing capacity of the pile foundation cannot be ignored. The research laid a theoretical foundation for the analysis and popularization of the static drilling rooted energy pile in coastal soft area.

Primary and secondary consolidation compression for saturated soil considering coupling effect of loading and heating

Primary and secondary consolidation compression for saturated soil considering coupling effect of loading and heating

Investigation into the gas adsorption-loading coupling damage constitutive model of coal rock

Coal and gas outburst is the result of comprehensive action of in situ stress, gas and mechanical properties of coal rock. The coupling effect of loading and gas adsorption eventually leads to the coal rock failure. Based on the principle of strain equivalence and considering the coupling effect of gas adsorption and stress loading, an adsorption-loading coupling damage model is established which breaks through the bottleneck of only considering a single influencing factor. Taking briquette samples with controllable properties as the research object, uniaxial compression tests of coal rock at different gas adsorption pressures are carried out and the model is verified based on the test results. The results of model calculation and tests show that the meso-damage stage of the coal body can well correspond to the macroscopic deterioration phenomenon and it is in good agreement with the stress–strain curve. It is proved that the model has good applicability and can accurately describe the damage and failure process of coal rock.

Insight Into the Strengthening Mechanism of the Al-Induced Cross-Linked Calcium Aluminosilicate Hydrate Gel: A Molecular Dynamics Study

Understanding and controlling the mechanical properties of calcium aluminosilicate hydrate (C-A-S-H) gel is essential to the performance improvement of cementing materials. This study characterizes the mechanical properties and failure mechanism of cross-linked C-A-S-H that have Al/Si ratios ranging from 0 to 0.20 by employing the reactive molecular dynamics simulation. In these constructed C-A-S-H models, the Al-induced cross-linking effect on the aluminosilicate chains is well reproduced. With the incorporation of aluminate species, layered C-S-H structure gradually transforms into three-dimensional C-A-S-H. The uniaxial tensile tests show that Al-induced cross-links significantly increase the cohesive force and stiffness of C-A-S-H along both y- and z-directions. In the C-A-S-H model with the Al/Si ratio equal to 0.2, in which all the bridging sites are cross-linked, the toughness along y-direction significantly improves the interlayer mechanical properties compared to those within the layers. The deformation mechanism of the C-A-S-H structure is also studied. Results show that the depolymerization of the calcium aluminosilicate skeleton is the main route to uptake the loading energy. Both the increase of y- and z-directional strength of the structure can be related to the increasing polymerization of aluminosilicate chains along that direction. This demonstrates the important role of aluminosilicate chains in resisting the external tensile loading. Besides, during the failure process in C-A-S-H elongation, the hydrolysis reactions of calcium silicate skeleton are caused by the coupling effect of loading and interlayer water “attack.” While the Al-O-Si bond breakage results from the protonation of bridging oxygen atom, the hydrolytic reaction of Si-O-Si is initiated by five-coordinate silicon formation. Both pathways weaken the bridging bond and thus result in the breakage of T-O-Si, where T is Al or Si.

Dynamic Viscosity Standard of High Viscosity Modified Asphalt Considering Temperature and Load Coupling Effect

The anti-ravelling and anti-rutting performances of porous asphalt pavement are significantly affected by dynamic viscosity of high viscosity modified asphalt. Climatic and traffic conditions vary greatly due to the vast territory of China, and dynamic viscosity standard has not been recommended up to now aiming at different temperature and load conditions. The influence of high viscosity additive dosage on key property indexes was firstly analysed for asphalt and asphalt mixture, and appropriate dosage was recommended. The dynamic stability changing law of porous asphalt mixture was revealed under different temperature, load and their coupling conditions. Multiple regression relation of them was established. Finally dynamic viscosity standard was proposed considering temperature/load coupling effect. The research results show that when high viscosity additive dosage exceeds 10% for 70# base asphalt, the increasing trend of dynamic viscosity becomes slowing down. Semi-logarithmic relations of dynamic stability with ravelling loss, Marshall stability were respectively found, and double-logarithmic relation of that with dynamic viscosity was found. The appropriate dosage of high viscosity additive is recommended as 12%. Based on multiple regression formula of dynamic stability with dynamic viscosity, temperature and load, the lower limit of 60°C dynamic viscosity is recommended as 50000Pa•s for normal region, 100000Pa•s for heavy-load region, 200000Pa•s for high-temperature region, and 400000Pa•s for heavy-load & high-temperature region.

Effect of inclusion defect on fatigue failure of FGH96 superalloy at 600°C

High cycle fatigue experiments were conducted at 600°C to study the effect of manufacture defect on crack initiation behaviour of FGH96. The experiments were performed at different stress levels to considering the coupling effect of loading and defect. The stress ratio was selected at 0.05. The results revealed that the fatigue life behaviour are much different in different loading levels. In order to examine the crack initiation mechanism, Scanning electron microscopy (SEM) method was used to analyze the failure surfaces. Different failure modes including surface cracking, sub surface cracking as well as internal crack initiation were found. The tested fatigue lives were found to have a strong relation with the mode of the crack initiation.

Life-cycle based analytical theory of concrete-filled steel tubular structures and its applications

<p indent=0mm>Concrete-filled steel tube (CFST) is a composite structure consisting of a steel tube filled with concrete. The steel tube and its concrete core work together to carry external loads applied to the structure. Due to the interaction between the two kinds of materials, i.e., the confinement effect of steel tube on the core concrete, CFST structures can effectively delay/avoid the local buckling of the steel tube and the brittle failure of the concrete core. The superior structural properties of CFST include high strength and stiffness, good ductility, excellent seismic and fire performances, and easy construction. Therefore, CFST structures have been extensively used in large-scale constructions including industrial plants, subway stations, transmission towers, high-rise buildings, and bridges, etc. CFST structures have also offered substantial benefits on architectural appearance and engineering economy. The confinement effect in CFST throughout its service-life essentially contributes to the structural advantages, whilst it has, at the same time, brought about enormous complexities in the corresponding load-resisting mechanisms. Firstly, an in-depth understanding and accurate characterization of the confinement effect, and the development of some feasible constitutive models for the core concrete that facilitate the analysis and design of major infrastructures, becomes the key issue to be addressed. The salient loading factors in the service-life of CFST structures need to be considered in the constitutive models, such as long-term sustained load, low-cycle cyclic load and full-range fire. Secondly, the establishment of damage mechanism analysis and strength prediction models for CFST structures considering long-term sustained load, complex loading conditions, earthquake and fire becomes another key issue that needs to be resolved for the safety design of major CFST constructions. Life-cycle based damage mechanism and analytical theory of concrete-filled steel tubular structures have been investigated and established based on nearly <sc>20 years</sc> of persistent and systematic study. The design methods for the ultimate loading capacity of CFST structures were further proposed. The major research outcomes can be summarized in the following three aspects: (1) The interaction between the steel tube and its core concrete as well as the passive confinement mechanism in CFST were revealed. A general constitutive model for the confined core concrete under various stress/action conditions was established with the “confinement factor” as an essential variable. The considered actions include long-term sustained stress, cyclic load and elevated temperature. (2) Theoretical models were established to account for the damage mechanism of CFST structures under long-term sustained load and complex loading conditions. The ultimate strength of CFST members under various loading conditions was analysed, including compression, tension, bending, shear, torsion, and the combinations of different loads and load paths. The creep and shrinkage of concrete as well as the deformation of CFST under long-term sustained load were accurately simulated. (3) Theoretical models were established to simulate the damage mechanism of CFST under earthquake and full-range fire. The hysteretic properties and ductility of CFST members under low-cycle cyclic loading were revealed. The model for calculating the fire resistance of CFST columns was proposed, in which the coupling effects of loads and full-range fire were taken into account. This paper briefly reviews the development of CFST structures and outlines the life-cycle based analytical theory for CFST structures. Finally, the potential development trends of the CFST structures are discussed.

Diffusion Behavior of Chloride Ions in Concrete Box Girder under the Influence of Load and Carbonation.

In order to study the durability degradation characteristics of concrete box girder under load and carbonation and chloride ion erosion, a scale model of concrete box girder was made for experimental research. According to the test results, the diffusion characteristics of chloride ions in the concrete box girder under the coupling effect of load and carbon dioxide were analyzed. By revising the calculation formula of the existing chloride ion concentration considering multiple factors, a calculation model of chloride ion concentration considering the influence of carbonation was proposed, and the test results were verified. The results show that the chloride concentration of the box girder on the same cross section is non-uniformly distributed due to the shear lag effect and the spatial structure. After considering the effect of carbonation, the difference rate of the improved model proposed in this paper is generally within 10%. Compared with the original model, the difference rate is reduced by a maximum of 19%.

A study on mechanical properties and damage model of rock subjected to freeze-thaw cycles and confining pressure

red sandstone was tested in the freeze-thaw cycle under open and saturated conditions, and the mechanical properties of samples after different freeze-thaw cycles (0, 5, 10, 20, and 40 freeze-thaw cycles) were tested under the four kinds of confining pressures (0 MPa, 2 MPa, 4 MPa, 6 MPa). The whole process characteristics of deformation and failure of red sandstone were analyzed, and the effects of freeze-thaw cycles and confining pressure on red sandstone mechanical properties were studied. According to the characteristics of rock material non-uniformity and randomness, the effect of freeze-thaw and load coupling effect on the total damage was quantitatively expressed, and established a damage model can reflect the whole process of rock deformation. The theoretical expression of model parameters were derived by using the multivariate function to obtain total differential method, and the damage mechanical properties of rock were analyzed. The results has shown that: With the increase of the freeze-thaw cycles and confining pressure, the compressibility of rock is continuously enhanced, the peak strain is gradually increasing, the plastic yielding section is becoming more and more obvious, the post-peak stress reduction rate slows down, and the failure mode is transformed from brittleness to ductility. Meanwhile, the elastic modulus, peak stress and residual strength increase with the increase of confining pressure, and decrease with the increase of freeze-thaw cycles. The damage model reflects the process of deformation and failure of frozen-thawed rock under the action of load, especially the characteristics of post-peak strain softening and residual strength. The rock total damage evolution path reflects that the meso-mechanical response was consistent with the macro-deformation and failure characteristics, and the nonlinear influence characteristics of freeze-thaw and load on the rock total damage propagation are described. Furtherly, the deformation failure of rock is revealed by the mechanical damage mechanism.

Dynamic Mechanical Properties of Coals Subject to the Low Temperature-Impact Load Coupling Effect

The effects of low temperature gradient on dynamic mechanical properties of coal were examined through Split-Hopkinson Pressure Bar (SHPB) Dynamic Impact Experiment, the law of dynamic mechanical parameters of coal specimen changing from room temperature to negative temperature (25 °C, −5 °C, −10 °C, −15 °C, −20 °C, −30 °C, −40 °C) was analyzed, and the coal-rock stress-strain curve characteristics subject to the low temperature-impact load coupling effect was discussed. The law of the effects of different strain rates on the rock strength properties and the compressive deformation and failure was analyzed by studying the coal specimen at −15 °C. Moreover, the mechanical properties of coal specimen in saturated and dry conditions were compared, and the effects of water and water-ice phase transition on the strength properties of the corresponding coal specimen were analyzed.