High Bearing Capacity Research Articles

Experimental investigation on flexural performance of concrete beams strengthened with SMA-GFRP-ECC smart composite materials

The structural performance improvement of concrete members is by far a crucial theoretical issue for engineers, and the development of modern smart and composite materials makes it possible to gradually enhance the durability design of the concrete structure. In this study, six beams of the same size and reinforcement ratio, the proposed composite beam (SMA-GFRP-ECC) and five comparative beams (RC, R-ECC, SS-ECC, GFRP-ECC, SMA-ECC), were designed and tested under low-cycle unidirectional cyclic loading and unloading conditions. The energy dissipation capacity, displacement ductility, residual deformation, and self-repairing performance of each concrete beam were evaluated. Afterward, a concise calculation model for the studied composite beam is deduced and developed based on the existing relevant constitutive models and concrete assumptions. The test results indicate that compared with RC beams, the composite reinforced ECC beams show obvious multi-cracking and smaller crack width during the loading process and have good bending ductility. The innovative SMA-GFRP-ECC beam is capable of a high bearing capacity, ductility, and damage self-repairing. The new proposed beam has more than 80% of the maximum crack width recovery capacity during unloading. Hence, the proposed SMA-GFRP-ECC beam is a rather good first attempt of strengthened beams, combining the advantages of SMA, GFRP, and ECC.

Macroscale Ultradurable Anti‐wear Achieved on Graphene‐based Films via Multiphase Combination

Excellent anti‐wear performance, high bearing capacity, and long service life are essential prerequisites for the reliability and durability of Si‐based micro/nano device operation. To improve the anti‐wear property and prolong service life of Si‐based micro/nano devices under high loads, graphene oxide (GO) nanosheets, graphene quantum dots (GQDs) and ionic liquid‐capped GQDs (IL‐GQDs) were used to create three kinds of multilayer films as solid lubricant, that is, single‐component (GO)5, (GO/GQDs)5 and (GO/IL‐GQDs)5 multilayer films. The results showed that (GO/IL‐GQDs)5 composite multilayer possessed excellent wear resistance under a high load of 4 N with the wear rate of 4.9×10‐7 mm3·N‐1·m‐1. The superior anti‐wear performance of (GO/IL‐GQDs)5 composite film is mainly due to the unique 3D structure composed of GO nanosheets alternating with IL‐GQDs. The rigid GO nanosheets play the role in load‐carrying capacity, and the IL‐GQDs could delay the time of structure transformation and reduce the loss rate of transfer film, thereby effectively extending the service life of (GO/IL‐GQDs)5 composite multilayer. Such multilayers are expected to be good solid lubricating films suitable for Si‐based micro/nano devices.This article is protected by copyright. All rights reserved.

Numerical analysis on seismic behavior of a novel steel-timber composite frame column

Steel-timber composite structures are a novel hybrid structural system that combines the advantages of both steel and wood structures, holding great promise for various applications. In this paper, the seismic behaviors of steel- timber composite columns are investigated based on finite element analysis. The reliability of the finite element model is validated by quasi-static test results. Numerical analysis results indicate that the proposed steel- timber composite systems is with high ultimate bearing capacity, full hysteresis loops, and strong displacement ductility, demonstrating excellent seismic performance. The axial compression ratio, steel tube thickness, and flexural point height significantly influence the seismic resistance of the structure.

Mechanical characteristics of auxetic composite honeycomb sandwich structure under bending

Auxetic honeycomb sandwich structures (AHS) composed of a single material generally exhibit comparatively lower energy absorption (EA) and platform stress, as compared to traditional non-auxetic sandwich structures (TNS). To address this limitation, the present study examines the use of aluminum foam (AF) as a filling material in the re-entrant honeycomb sandwich structure (RS). Filling the AHS with AF greatly enhances both the EA and platform stress in comparison to filling the TNS with AF, while the auxetic composite honeycomb sandwich structure effectively addresses interface delamination observed in traditional non-auxetic composite sandwich structures. Subsequently, the positive–negative Poisson’s ratio coupling designs are proposed to strengthen the mechanical features of a single honeycomb sandwich structure. The analysis results show that the coupling structure optimizes the mechanical properties by leveraging the high bearing capacity of the hexagonal honeycomb and the great interaction between the re-entrant honeycomb and the filling material. In contrast with traditional non-auxetic sandwich structures, the proposed auxetic composite honeycomb sandwich structures demonstrate superior EA and platform stress performance, suggesting their immense potential for utilization in protective engineering.

Seismic evaluation of a self-centering retrofit solution for modular steel structure connections

In this study, a novel plug-in modular steel structure (MSS) connection is proposed, in which the connector, cover plates, and bolts form a complete connecting system. To improve the seismic performance and post-earthquake functional recoverability of the MSS connection, a retrofit solution with diagonal self-centering (SC) haunch braces is introduced, and the self-centering modular steel structure (SC-MSS) connection is developed. Theoretical analysis of the mechanical properties of the MSS and SC-MSS connections are conducted, and the calculation formulas for the initial stiffness and bending bearing capacity are derived. A comparative experimental study of one MSS connection and five SC-MSS connections under cyclic loading was carried out to evaluate their seismic performance, and to explore the influences of the main haunch parameters on the behavior of the SC-MSS connection. The results demonstrate that the plug-in connector, cover plate, and bolts can realize reliable continuity and integrity between modules. The SC haunch braces have good collaborative work with the modules and provide sufficient restoring force, and the damage in all the SC-MSS connections was found to be effectively controlled and delayed as compared with the MSS connection. The MSS connection displays a full shuttle-shaped hysteretic response with adequate plastic development, while the SC-MSS connections successfully exhibit expected flag-shaped hysteretic responses with higher bearing capacity and lower residual displacement. The adjustment of the post-activation stiffness and pre-pressed force of the haunch brace is found to improve the connection performance, and a reasonable selection of the installation scheme could achieve optimal self-centering efficiency. The experimental results also verify the feasibility and correctness of the proposed theoretical formulas and mechanical assumptions.

Cat paw-inspired magnetorheological elastomer embedded mechanical metamaterials with active sensing and switching stiffness for vibration isolator

Real-time vibration monitoring, assessment, and isolation play critical roles in the safety and maintenance of engineering industries and traffic facilities. Recently, magnetorheological elastomers (MRE) with tunable stiffness have been considered promising solutions for vibration isolation. However, for some heavy-load conditions, such as motors or machine tools, MRE vibration isolators are insufficient for realizing vibration sensing and high bearing capacity. Therefore, it is critical to design a novel MRE isolator system that enables real-time vibration monitoring, isolation, and bearing capacity. Herein, we propose a cat's paw-inspired oct-MRE vibration isolator coupled with a soft MRE for energy buffering embedded in octet metamaterials to support the load. For vibration sensing, a sliding triboelectric nanogenerator (TENG) was constructed using polytetrafluoroethylene (PTFE) and a copper foil around the oct-MRE inside a vibration isolator to monitor and evaluate the vibration state in real-time. Experimental tests show that our all-in-one vibration isolator can monitor motor vibration accurately and actively modulate it under resonant conditions, the vibration acceleration can be reduced from 17.0 m/s2 to 12.9 m/s2. This study provides an ideal solution for intelligent health monitoring of motors and other autonomous, smart, and long-term engineering tasks.

Experimental Study on Mechanical Behavior of Skirt–Pile Foundations in Saturated Clay under Horizontal Load

Skirt–pile foundations have gained widespread attention in the field of offshore engineering due to their ease of installation and high bearing capacity. In this study, the ultimate bearing capacity, pile bending moment distribution and development, cumulative deformation characteristics, and cyclic stiffness development of skirt–pile foundations were investigated using physical model tests. The experimental results indicate that the ultimate bearing capacity and deformation resistance of the foundation can effectively be improved by increasing the skirt diameter. The cumulative deformation of the skirt–piles exhibited rapid development during the initial stages of cyclic loading, eventually stabilizing. Under long-term cyclic loading, the existence of the skirt can share the bending moment, which then affects the internal force distribution of the pile foundation along the axis. The pile foundation’s cyclic stiffness reduces as the loading cycles increase and increases as the skirt diameter and length grow. Meanwhile, the horizontal cyclic stiffness decreases as the number of cycles increases, stabilizing after 3000 cycles. This study can not only deepen the understanding of the deformation laws of skirt–pile foundations in clay soil but also offers some references for the design of offshore pile foundations.

Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site

Abstract Progress in jet grouting technology has been focused on the cutting-edge observer of jets, which aims to generate large columns of jet grouting and increase the activity of construction sites. Since jet grouting techniques vary from conventional grouting methods to modern techniques, they can be used in a variety of soil types and their application areas are expanding quickly. So, grouting methods have become very popular methods for subsoil strengthening. This article includes finding the physical and mechanical properties of the soil of the AL-Rashdia site, using a single-jet grouting machine and a steel model to test concrete piles and jet piles, and a double-jet grouting machine to compare the results obtained from laboratory model of one-dimensional jet grouting column pile with those of a one-dimensional concrete pile. The comparison showed that the settlement of the jet pile was smaller than that of the concrete pile and the bearing load was higher with jet columns giving a high bearing capacity comparable with the concrete pile. Shen’s method is more adequate to find the ultimate bearing load and the settlement for this load. Also, the ultimate pile ratio was 115.63% for the jet column, and the ultimate pile ratio for the concrete column was 123.49%. The compressive strength of the core sample of jet columns was large which improved the bearing capacity of the foundation.

Model Test Study on the Vertical Uplift Bearing Characteristics of Soil Continuous Solidified Pile Group Foundations

To solve the problem of the high bearing capacity of structures in deep and weak soil layers, we invented a new type of pile group foundation in which the soil was continuously solidified between piles (hereinafter referred to as the SCS pile group foundation). Considering the two key factors of pile spacing and CSM depth, the antipulling load characteristics of SCS pile group foundations in dry sand were studied via indoor half-model tests and numerical simulations. The results showed that the ultimate uplift capacity of the SCS pile group foundation with a 2D–6D CSM depth was about 2–3 times that of the traditional pile group. When the stiffness of the CSM is so large that its effect can be ignored, the greater the pile spacing is, the greater the ultimate uplift capacity is. For the same pile spacing, the greater the depth of the CSM is, the greater the ultimate uplift bearing capacity is. When the CSM depth is greater than 10D, the uplift effect of the CSM can be effectively exerted, and the antipulling advantage of the SCS pile group foundation can be fully utilized. This study provided a reference for the antipulling design of SCS pile foundations.

Macro modeling of composite shear wall with stiffened steel plates and infilled concrete

In high-rise buildings, traditional concrete shear walls have many limitations. This paper proposes a composite shear wall with stiffened steel plates and infilled concrete (CWSC), offering high bearing capacity, significant deformation capacity, and energy dissipation ability. The ductility coefficient ranges from 2.75 to 3.56, with an average ultimate drift ratio of 1/30, surpassing the 1/80 limit specified in the shear wall code. This paper also presents a macro model for CWSC based on experimental results. Studying the strain gauges in the steel plate reveals the stress mechanism in the composite shear wall, where the central region experiences shear forces while the corner regions undergo tension and compression. A comparison between the results of the macro model and existing experimental data demonstrates the ability of the model to accurately predict the hysteresis curve and seismic performance of CWSC. Likewise, a comparison of the macro model with hysteresis and skeleton curves from 15 different literature sources on composite shear walls shows that the macro model can effectively simulate the seismic performance of composite shear walls reported in previous studies. This confirms the applicability of the macro model.

Performance evaluation of grouted porous asphalt concrete

Abstract Semiflexible pavement (SFP) is considered a composite mixture, as it consists mainly of a porous asphalt mixture with high air voids grouted with highly flowed cementitious grout. Numerous benefits have been attributed to this technology, including exceptional slip resistance, a high static bearing capacity, and rutting resistance. In this study, two different types of semiflexible paving mix were produced by using two different types of grouting materials (GMs). There is a discrepancy between the compressive strengths of the two GMs used, as the compressive strength of the first mixture, which consisted of 96% cement and 4% silica fume (SF), was approximately twice the compressive strength of the second mixture, which consisted of 75% cement and 25% sand. The mechanical and durable properties of the two SFPs were studied, in addition to the effect of variation in the compressive strengths of the two GMs and their effect on the final performance of the pavement. The results of Marshall and rutting tests show that the SFP material exhibits good high-temperature stability. The effect of the variation in the compressive strength of the two mixtures was evident in the results of the tests compared with the sand mixture at a strength of 20.8 MPa, the SF at a strength of 48.1 MPa witnessed a 39.54% increase in the Marshall stability at 28-day curing age. Also, the composite material (CM) showed better rutting performance than traditional asphalt mixtures, which did not exceed 2 mm. The results of the indirect tensile strength (ITS) test showed a discrepancy between the two types of CM, as the ITS value of the grouting material of SF (GMSF) mixture increased by 14.91% compared with the grouting material of sand (GMSN) for the curing age of 28 days for unconditioned samples and by 20.22% for the conditioned samples for the same curing age, while the durability of two types of CM was measured by Cantabro abrasion loss and tensile strength ratio. The results were acceptable and within the specification limits. With a variation for the two types of CM, the GMSF mixture showed an increase in the value of Cantabro loss by 11.52% over the GMSN mixture for ageing samples and 6.59% for non-aging samples of 28 days of curing age.

Research on mechanical properties of concrete by nano-TiC-BF-fly ash.

Ultra-high-rise buildings require high concrete bearing capacity. Ordinary concrete often fails to meet the project requirements. Admixture of admixtures in concrete is a means of solution. Currently, studies on the incorporation of basalt fiber (BF) and fly ash (FA) in concrete are relatively mature. However, research on incorporating nano-Titanium Carbide (nano-TiC) in concrete is still relatively scarce, which has a lot of room for development. To further improve the mechanical properties of concrete, BF, and FA synergized with nano-TiC were incorporated into concrete to produce TBF concrete in this study. And Response Surface Methodology (RSM) was used to optimize the mechanical properties of concrete. The collapse and compressive deformation damage characteristics of concrete were analyzed. The microstructure of the cement matrix was analyzed by the SEM (Scanning Electron Microscope). An optimization model of the TBF concrete craving function was developed. Optimized ratios with compressive, split tensile, and flexural strengths as response objectives were obtained, and the accuracy of the optimized ratios was investigated using the same experimental conditions. The results of the study showed that FA increased the collapse of concrete, while nano-TiC and BF decreased the collapse of concrete. Under uniaxial compression, nano-TiC, FA, and BF together incorporated into concrete can improve its compressive damage state. Moderate amounts of nano-TiC, BF, and FA could improve the mechanical properties of concrete. Their optimal mixing ratio admixtures were 0.88%, 0.24%, and 5.49%, respectively. And the measured values under the same conditions were compared with the predicted values. The maximum difference in compressive strength was 6.09%. The maximum difference in split tensile strength was 7.14%. The maximum difference in flexural strength was 8.45%. This indicated that the accuracy of the RSM optimization model was good. A moderate amount of nano-TiC, FA, and BF could improve the densification of concrete.

A Review of The Flexural Mechanical Properties Of ECC-Fiber Reinforced Composite Composite Reinforced Beams

Engineering fiber-reinforced cementitious composite (ECC) has good ductility and crack control ability, and fiber-reinforced polymer (FRP) has high bearing capacity. Combining the two can effectively enhance the flexural mechanical properties of reinforced concrete beams. This paper introduces ECC and fiber-reinforced composite materials, and the effects of this reinforcement method on cracks, deflection, and bearing capacity of reinforced concrete beams are reviewed.

Assessment of Bearing Capacity and Settlement Characteristics of Organic Soil Reinforced by Dune Sand and Sodium Silicate Columns: A Numerical Study

Organic soil is problematic soils in geotechnical engineering due to its properties, as it is characterized by high compressibility and low bearing capacity. Therefore, several geotechnical techniques tried to stabilize and improve this soil type. In this study, sodium silicate was used to stabilize sand dune columns. The best sodium silicate concentration (9%) was used, and the stabilized sand dune columns were cured for seven days. The results for this soil were extracted using a numerical analysis program (Plaxis 3D, 2020).In the case of studying the effect of (L/D) (where ‘’L” and ‘’D’’ length and diameter of sand dune columns) of a single column of sand dunes stabilized with sodium silicate with a different diameter, the results showed that the best effect was for L/D of (4) with D equal to (0.7m) in the end bearing columns type. In the case of studying a group of columns, the percentage of improvement in soil bearing ratio increased with increasing the number of columns in both floating and end bearing types. When using (8-columns) with a square distribution pattern, the optimum improvement was at the end bearing and at the ratio L/D of (6), where the improvement percentage was (666%) compared to the unimproved soil.

Study on the Influence of Water Erosion on the Bearing Capacity and Function of the High Pile Foundation of the Wharf

High-pile foundation is a common form of deep foundation commonly used in ocean environments, such as docks and bridge sites. Aiming at the problem of bearing capacity of high pile foundations, this paper proposes the calculation of bearing capacity and the analysis of scour depth of high pile foundations under the action of scour based on the modified p-y curve. In this paper, three kinds of scour mechanisms—natural evolution scour, general scour, and local scour—are described; and the calculation methods of scour widely used at present are compared and analyzed. The solution of the vertical stress of soil around the pile under local scour is solved and applied to the β method to solve the lateral resistance of the pile under local scour. The local erosion is equivalent to the whole erosion, and the expression of the ultimate soil resistance before and after the equivalent is calculated, respectively, according to the principle that the ultimate soil resistance at a certain point above the equivalent pile end remains unchanged. The distance from the equivalent soil surface to the pile end can be obtained simultaneously, and then the equivalent erosion depth, p-y curve of sand at different depths, and high pile bearing capacity can be obtained. Finally, it is found that the bending moment of a single pile body varies along the pile body in the form of a parabola, and the maximum bending moment of the pile body is below the mud surface and increases with the increase in horizontal load. When the scouring depth is 30 m, the horizontal load is 25 KN, and the maximum bending moment of the pile body is about 150 N·m. The data with a relative error greater than 10% accounted for only 16.6% of the total data, and the error between the calculated value and the measured value was small. The formula can predict the erosion depth more accurately.

Complete Kinematics/Dynamics Modeling and Performance Analysis of a Novel SCARA Parallel Manipulator Based on Screw Theory

Abstract In this paper, a novel Selective Compliance Assembly Robot Arm (SCARA) high-speed parallel manipulator that can realize three-translation and one-rotation motion is proposed, and an accurate dynamic modeling methodology is investigated. The mechanism is composed of four limbs with a double parallelogram structure and a single moving platform. The high bearing capacity and high dynamic response of the novel mechanism make it a viable alternative choice for this kind of automation equipment. The degree-of-freedom (DOF) of the mechanism is analyzed by the screw theory. At the same time, the velocity mapping model of the mechanism is established by the twist screw and the actuated Jacobian matrix. Then, the acceleration mapping model of the mechanism, including the generalized kinematic pairs, is established by reduced acceleration state, the modified Lie screw, and the acceleration Hessian matrix. On this basis, the complete dynamic model with a compact form of the mechanism is deduced by the combination of screw theory and virtual work principle, and the correctness of the developed model is verified by multibody simulation software. Finally, considering the inertial characteristics of the mechanism, the dynamic performance distribution in the reachable workspace of the mechanism is analyzed by the Joint-Reflected Inertia (JRI) index and Coefficient of Variation of joint-space Inertia (CVI) index, and some areas are selected as the task workspace using the above index to guarantee good dynamic performance.

Research and propose suitable foundation solutions for some types of ground structures in Hai Duong city area

According to the urban planning up to 2030, Hai Duong City is expanding in both area and scale. In particular, the high-rise building density is planned to increase. However, the soils at Hai Duong city are unfavorable for high-rise building construction because the high-bearing capacity soils are distributed at a great depth, with soft soils above. Therefore, the pile foundation is a feasible solution for high buildings. With the pile foundation, the selection of the load-bearing soil layer, the effective depth of pile tip placement, pile diameter, the number of piles as well as the estimated pile-bearing capacity in accordance with the ground structure are of decisive importance to the effectiveness of the solution. The article uses the Pile and Pile Group modules in the Geo5 Software Suite combined with experimental research results to determine the load-bearing capacity of piles according to different options in three types of ground structures in Hai Duong City area. On that basis, evaluate the reasonableness of pile foundation options for buildings of different sizes based on technical and economic factors (number of piles, settlement, and stability). The results indicated that the effective depths of pile tip are varied from 33 m to 35 m for ground structure types I and II, and are greater than 40 m for ground structure type III. Reasonable pile foundation solutions for each group of buildings and ground structure type are also proposed.

Design of a Passenger Ship Launch Using an Air Bag System

Ship launching is one of the stages of ship production before the ship is handed over to the owner, which marks the beginning of the ship's life. With the development of technology at this time, various launching methods have been developed, one of which is the launching method using an air bag system. Launching using air bags has many advantages compared to conventional launching methods that have been used so far. Pre-launch calculations are performed to avoid risks during the launch. Launching using air bags begins with calculating the weight plan of the ship launch and the preparation of the air bag layout. Using CB/T 3837:1998 Technological Requirements for Ship Upgrading or Launching Relying on Air Bags, Shipbuilding Industry Standard, and ISO 14409:2011 ships and marine technology-ship launching air bags, the number of air bag requirements and layout can be determined to support the ship launching process. The passenger ship, with an length overall of 62.80 metres, is planned to have a launch weight of 1058.881 tons. By using the QG6 high-bearing capacity air bag model with 6 layers of cord fabric with a diametre of one metre and a contact length between the air bag and the ship's body of ten metres, a total of 11 air bags are required in a linear arrangement to support the launch of a passenger ship. The distance between air bags is 2.07 metres to 5.736 metres, the longer the distance between air bags, the greater the load supported by each air bag.

A self-recoverable negative stiffness metamaterial with enhanced bearing and energy dissipation capacity

Because of their desirable properties, mechanical metamaterials have drawn increasing attention. Negative stiffness (NS) metamaterials can be used as reusable energy dissipation devices, but they usually have low bearing capacity. In this study, a self-recoverable NS structure with enhanced bearing and energy dissipation capacity was proposed. It breaks free from the size limitations of curved beams or thin rods, and can have high bearing and energy dissipation capacity through the mutual extrusion and friction between the snap plug and the layered snap groove. The mechanical properties of the proposed NS structure were studied by finite element analysis and experiments. The reusability of the structure was verified by cyclic loading experiments. The results show that compared with the traditional curved beam NS structure and the previously self-recoverable NS structure, the bearing and energy dissipation capacity of the proposed structure have been greatly improved.

An asymmetric stabilizer layer structure of REBCO superconducting tapes for resistive superconducting fault current limiters

Used in resistive superconducting fault current limiters (R-SFCLs), REBCO tapes are required to have both large current limiting resistance and high over-current bearing capacity. The contradiction between high resistance and large over-current is the main difficulty in the design of REBCO-tape structure for R-SFCLs. In this paper, an asymmetric stabilizer layer structure of REBCO tapes has been proposed, fabricated and tested for R-SFCLs. Comparing to traditional tapes with a symmetric stabilizer structure, the REBCO tape with new structure showed a 59 % improvement in over-current bearing capacity: the peak current increased from 1020 A to 1620 A while keeping the same total resistance. Simulation calculation on the current distributions in every layer showed that the asymmetric structure is superior to the symmetric structure.