Uniform Load Research Articles

Dynamic instability of reinforced hollow cylinders in a confined underwater environment

An experimental investigation was conducted to understand the collapse mechanisms of internally ring stiffened aluminum cylinders under uniform hydrostatic loading in a confined underwater environment. The implosion of ring stiffened cylinders was studied using a combination of high-speed photography and 3D Digital Image Correlation (DIC). The results show that as stiffener thickness is decreased, the collapse of the structure transitions from two segments collapsing in mode III with the stiffener serving as boundary separating the segments to one uniform mode II collapse where the ring stiffener collapses with the structure. Furthermore, in the cases with two collapses, the behavior of the structure can be described as approaching that of two cylinders divided by a simply-supported boundary condition at the location of the stiffener. The ring thickness also affects the collapse pressure of the cylinder, radial velocity during collapse at the location of the ring stiffener, and dwell time between the collapse of two sections in cases with two collapses.

Laser-induced manganese oxide/graphene composite electrodes with commercial-level mass loading towards high-performance supercapacitors

Combining of graphene with pseudocapacitance metal oxide is effective to construct supercapacitor electrode with high energy storage capacity. However, balancing the contradiction between high load of metal oxide and high stability of electrode is still challenging. Herein, a novel supercapacitor electrode composed of 3D graphene and manganese oxide is in-situ fabricated by laser carbonization of polyimide (PI) foam loaded with manganese acetate precursor. Due to the rich porous structure and super hygroscopicity of PI foam, high content manganese acetate is uniformly loaded into the network of PI foam. Under laser irradiation, PI foam is carbonized to form 3D porous graphene, while the generation of MnO-Mn3O4 and its uniform loading on graphene is achieved synchronously. The obtained composite electrode exhibits a commercial-level mass loading up to 8 mg cm−2, with a 48.6% weight ratio of MnO-Mn3O4. As a result, an ultra-high specific capacitance of 1525 mF cm−2 can be obtained for the composite electrode at the optimal doping concentration of 0.3 mol L− 1. Notably, the composite electrode also exhibits excellent cycling stability of 94.75% retention rate after 6000 cycles. The maximum area specific capacitance of the micro supercapacitor with PVA/LiCl gel electrolyte is 410.19 mF cm−2, the maximum energy density and power density are 82.04 μWh cm−2 and 400 μW cm−2, respectively.

Numerical Modeling and Application of Horizontal-Axis Wind Turbine Arrays in Large Wind Farms

The global supply of energy is still tight, even with the rise of renewable energy utilization and abundant wind energy. More and more large wind farms have been installed globally. As of 2020, China’s total installed capacity accounted for 38.8%, far ahead of other countries. The layout of horizontal-axis wind turbine (HAWT) arrays in large wind farms poses three main issues: (1) How to select a site. (2) How to arrange the HAWT arrays to achieve greater power extraction at a specific wind farm. (3) How to reduce the noise generated by HAWTs. The numerical simulation of a HAWT wake field generally includes the analytical method (AM), vortex-lattice or vortex particle method (VM), panel method (PM), blade element momentum method (BEM), generalized actuator method (GAM), and direct modeling method (DM). Considering the computational cost, this paper combines DMs and mainly adopts the BEM-CFD coupling method, including uniform and non-uniform loading of axial force. Forty specially designed numerical experiments were carried out, which show that: (1) the BEM-CFD method greatly improves the calculation speed within the accuracy range of a thrust coefficient less than 2.5%, making it very suitable for the calculation of large wind farm HAWT arrays; (2) for regular HAWT arrays, it is reasonable to choose a 6D spacing in the wind direction and a 4D spacing in the crosswind direction for simplicity in practice.

Optimization of Bolted Joints: A Literature Review

Bolted joints are widely used in the aerospace and automotive industries due to their ease of assembly, disassembly and design flexibility. Optimizing threaded fasteners is essential to achieve uniform load distribution and minimize the number of bolts required, thereby reducing system cost and weight. This review paper aims at summarizing the five optimization techniques available in the literature, including bolt layout, tightening strategies, tightening sequences, bolt size, and stresses. The purpose is to emphasize the importance of optimizing bolted joints via the proper selection of materials, geometry, patterns, and bolt sizes, to obtain efficient joints with low assembly time while maintaining strength.

Study on multi-level progressive optimization of planetary roller screw mechanism

This paper establishes a multi-level progressive optimization model of planetary roller screw mechanism (PRSM) to achieve a more uniform load distribution, lower contact stress considering rolling-sliding friction and reduced axial clearance. By integrating the Halton sequence and Kriging model into the design of experiment (DOE), the sensitivity of various parameters to the optimization objectives is studied, thereby determining the optimization flow. Based on the proposed geometric constraints, a combination strategy employing the AMGA2 and Hooke-Jeeves algorithm is implemented to efficiently obtain optimization results, with the optimized parameters from previous levels serving as design constants for the subsequent level of optimization. Further comparisons demonstrate a notable enhancement in the comprehensive performance of the optimized PRSM, which is ultimately validated through FEM.

Engineering Significance of Annular Raft Foundations over Solid Raft FoundationsJ

Abstract: Raft foundations play a pivotal role in distributing structural loads to the underlying soil, thereby ensuring the stability and integrity of various civil engineering structures. The choice between different types of raft foundations, such as solid and annular rafts, significantly impacts the overall performance and durability of a structure. This paper explores the engineering significance of annular raft foundations in comparison to solid raft foundations. The traditional solid raft foundation offers uniform load distribution and settlement control; however, it often encounters challenges when dealing with non-uniform soil profiles, differential settlements, and expansive soils. Annular raft foundations, a relatively innovative approach, address these challenges by featuring a central void within the raft. This void introduces a controlled differential settlement mechanism, enabling the foundation to accommodate non-uniform soil conditions effectively. Moreover, annular rafts offer improved structural performance in regions prone to ground movements, as the central void allows the foundation to adjust to soil displacements more flexibly than a solid raft. The engineering significance of annular rafts extends to their enhanced loadbearing capacity and reduction in material usage compared to solid rafts. The design of annular rafts takes advantage of the arching effect within the void, which enables the foundation to support heavier loads while minimizing the amount of concrete and reinforcement required. This not only contributes to cost savings but also aligns with sustainable construction practices by reducing the environmental impact associated with excessive material consumption.

Experimental and Design Parametric Study of a Novel Grouted Square Steel Tube Upper Chord–Concrete Composite Floor

A novel composite floor consisting of an upper chord of a grouted square steel tube truss and a lower chord of a reinforced concrete slab is proposed to address existing problems with precast composite floors, such as a complex construction process, high cost, significant resource consumption, and severe environmental pollution. Sixteen-point loading tests were carried out on five simply supported one-way slabs to simulate the stress state of the floor under a uniform load and to investigate the stiffness, cracking moment, load-carrying capacity, and failure mode of the composite floor system. The results showed that the composite floor system exhibited ductile failure, with cracks uniformly distributed at the bottom of the slab; additionally, the grouted steel tube did not experience uplift or out-of-plane buckling, and the truss welds did not fracture, indicating that the composite floor system still had further deformation capacity and load-carrying capacity with satisfactory stress conditions. After unloading, the residual deformation of the composite floor accounted for 28% to 36% of the maximum deflection, demonstrating good deformation recovery ability. The bottom slab thickness and truss height are key parameters that influence the new composite floor, and increasing the two parameters enhances the cracking load, deformation resistance, and flexural capacity of the composite floor, with a significant improvement achieved by increasing the truss height. The floor slab should have a minimum thickness of 60 mm, as required by China’s Code for Design of Concrete Structures, and the truss height-to-span ratio should be 1:30, which meets the deformation and load-carrying requirements of the floor and conforms to the design concept of green buildings.

Разработка методики перераспределения вагонопотоков (на примере Северо-Западного полигона)

Purpose: To increase economic efficiency of the process of finding and moving loaded and empty cars on the basis of improving the dynamic model of loading the infrastructure of JSC “Russian Railways” during the implementation of the process of approving applications for cargo transportation and notification requests for the transportation of empty wagons. Methods: Systematic approach and the theory of algorithms have been used to find out the reasons for the accumulation of cars on railways, an analysis has been made of the current distribution of car traffic in the North-Western Polygon to identify systemic patterns that encourage an increase in economic costs. Results: A method of stage-by-stage progress of car traffic has been developed, which allows to synchronize the capabilities and needs of participants of the transport services market in order to obtain a positive economic effect; the conditions for the uniform loading of infrastructure elements are determined, which make it possible to exclude overloading of critically important sections. Practical significance: The method allows us to balance the capacity of the infrastructure and the processing capacity of the consignee, which increases the economic efficiency of the transportation process. Consignees will have access to a tool that allows them to influence the progress of goods to their address, and the carrier will reduce operating costs by eliminating the occupation of infrastructure at the approaches to destination stations.

A Study on the Contact Characteristics of Tires-Roads Based on Pressure-Sensitive Film Technology.

Tire-road characteristics are a critical focus of research in the automotive and transportation industries. On the one hand, the research can help optimize tires' structural design; on the other hand, it can analyze the mechanical response of the pavement structure under the vehicle load. In addition, the non-uniformity distribution of the tire ground stress will also have a direct impact on the skid resistance, which determines the driving safety. Due to the limitation of testing technology, the measurement of tire ground pressure was mainly carried out on a flat test platform, ignoring the roughness of the actual pavement surface texture. The tire-road contact characteristics research on the macro-texture and micro-texture of asphalt pavement needs to be broken through. A high-precision pressure-sensitive film measurement system is utilized to examine the actual contact characteristics between two types of automobile tires and three types of asphalt pavement in this paper. The influence law of pavement texture and patterned tires on the contact area and stress was explored, and the concentration effect of tire-road contact stress was evaluated. The results indicate that the contact area of grounding tires exhibits a nearly linear relationship with tire inflation pressure and load. Notably, the change in load has a more significant influence on the contact area than tire inflation pressure. On asphalt pavement, the contact reduction rate decreases by approximately 5-10% for block pattern tires and 10-15% for longitudinal pattern tires. Furthermore, as the texture depth of the pavement increases, the contact area between tires and the pavement texture decreases. The actual tire-road interface experiences significant stress concentration due to the embedding and meshing effects between the tire and road surface. Even on a flat steel surface, the peak stress at the edge of the tread block exceeds the 0.7 MPa design load, which is about 2.5-3 times higher than the design uniform load. The peak stress between the tire and asphalt pavement reaches 4-10 times the design uniform load, with a rising trend as the pavement texture depth increases. This study can provide relevant experimental technical support for tire design and functional design of asphalt pavement.

Carbon thermal shock assisted activated carbon for lead carbon batteries: Uniform loading of lead nanoparticles and pore regulation

Activated carbon is currently recognized as one of the most promising additives for lead carbon batteries, but how to suppress intense hydrogen evolution and sulfation of lead carbon anode remains a challenge. Herein, we innovatively use programmable carbon thermal shock to achieve uniform dispersion and anchoring of lead nanoparticles on the surface of activated carbon, as well as selective removal of a portion of micropores. Owing to the synergistic mechanism of uniform dispersion of lead nanoparticles and pore regulation, the composites have extremely low hydrogen evolution rate, ultra-fast catalytic Pb2+ reduction rate, and can facilitate the growth of stable lead carbon interphase. The collaboration of multiple functions of composites increases the cycling life of simulated anode under high rate partial state of charge (HRPSoC) from 5449 cycles to 18,139 cycles, and the capacity retention rate under partial state of charge (PSoC) from 49 % to 82 % after 150 cycles. Furthermore, the as-fabricated lead carbon battery (12 V-12 Ah) exhibits an ultra-long cycle life of 32,107 cycles under HRPSoC and excellent rate discharge performance.

Highly selective and efficient hydrogenation of fatty acids to alcohols using NiMo@C catalyst

Selective hydrodeoxygenation is the central challenge in converting bio-derived fatty acids into fatty alcohols under mild conditions. Herein, an effective and highly selective carbon-supported NiMo catalyst (NiMo@C) was developed by the thermolysis Ni-based metal–organic frameworks (MOF) impregnated Mo species. At a low temperature of 160 °C, the stearic acid can be efficiently converted into corresponding stearic alcohols over the NiMo@C with about 97% selectivity at 100% reactant conversion, which is superior to the most reported catalysts containing noble catalysts. The excellent catalytic performance of NiMo@C catalyst was mainly attributed to the ordered arrangement of Ni in the MOF and the uniform loading of molybdenum salt, which leads to an ideal distribution of Ni and Mo after pyrolysis of the MOF. The carbon support also prevents the aggregation of metal particles, which promotes the dissociation of hydrogen and enhances the synergy between Ni and Mo sites. More importantly, the synthesized NiMo@C catalyst showed excellent reusability with no loss of activity after 15 consecutive runs due to the stability of the catalyst structure. This provides a useful and simple method for synthesizing highly efficiency and stable NiMo@C bimetallic catalysts, which can facilely and selectively hydrogenate the bio-derived fatty acids to corresponding alcohols under mild conditions.

Dynamic plastic response of sandwich structures with graded polyurethane foam cores and metallic face sheets exposed to uniform blast loading: experimental study and numerical simulation

Dynamic plastic response of sandwich structures with graded polyurethane foam cores and metallic face sheets exposed to uniform blast loading: experimental study and numerical simulation

Nonlinear in-plane thermomechanical stability of shallow sandwich micro-arches including strain gradient tensors

The microstructural-dependent nonlinear in-plane stability characteristics of functionally graded (FG) sandwich shallow micro-arches subjected to a uniformly distributed lateral load in conjunction with a temperature rise are investigated in the current study. In this regard, the third-order shear flexible arch formulations are established within the framework of the modified strain gradient continuum mechanics. The considered sandwich micro-arches are made of nanocomposites reinforced with graphene nanofillers based upon various FG lamination patterns. The Chebyshev–Gauss–Lobatto type of gridding scheme together with the pseudo arc-length continuation technique are employed to employ a numerical solution strategy for tracing the size-dependent lateral load–deflection and lateral load–axial load nonlinear stability plots. It is observed that by adding a rise in the temperature to the applied uniform lateral load, the first bifurcation lateral load enhances, while the second one reduces. Also, it is dedicated that there is a unique value of the applied uniform lateral load corresponding to which the axial resultant load as well as the induced lateral deflection in the micro-arch are the same for all values of the temperature rise. Moreover, it is revealed that by increasing the value of the rise in the temperature, the size dependency in the value of the upper limit lateral load becomes less prominent, while it enhances in the value of the lower limit lateral load.

Harmonic And Neutral Spherical Elastic Inhomogeneities with A Functionally Graded Interphase Layer

Summary We study the elastic field in a three-phase composite composed of an internal spherical homogeneous elastic inhomogeneity, an intermediate functionally graded interphase layer and an outer unbounded homogeneous elastic matrix subjected to an arbitrary uniform remote loading. The shear modulus of the interphase layer obeys a power law distribution along the radial direction. We accomplish the design of harmonic and neutral spherical elastic inhomogeneities. Specifically, the shear modulus of the matrix can be judiciously chosen in such a way that the insertion of the harmonic spherical inhomogeneity does not disturb the original constant mean stress in the surrounding matrix. The shear modulus of the matrix and relative thickness of the interphase can also be suitably chosen such that the insertion of the neutral spherical inhomogeneity does not disturb the original uniform deviatoric stresses in the surrounding matrix.

A practical approach of partial striking technique in high-rise buildings

PurposeThis research proposes a viable method of slab and shore load computation for the partial striking technique utilized in high-rise construction projects to optimize the use of horizontal formwork. The proposed Partial Striking Simplified Method (PSSM) is designed to be utilized by industry practitioners to schedule the construction operations of casting floors in order to control the formwork costs incurred throughout the completion of a project.Design/methodology/approachThe article presents the PSSM for calculating slab and shore loads in multi-story building construction. It introduces the concept of “clearing before striking,” where shore supports are partially removed after a few days of pouring fresh concrete. The PSSM procedure is validated through numerical analysis and compared to other simplified approaches. Additionally, a user-friendly Python program based on the PSSM procedure is developed to explore the capability of the PSSM procedure and is used to study the variations in slab load, shoring level, concrete grade and cycle time.FindingsThe study successfully developed a more efficient and reliable method for estimating the loads on shores and slabs using partial striking techniques for multi-story building construction. Compared to other simplified approaches, the PSSM procedure is simpler and more precise, as demonstrated through numerical analysis. The mean of shore and slab load ratios are 1.08 and 1.07, respectively, which seems to have a slight standard deviation of 0.29 and 0.21 with 3D numerical analysis. The Python program developed for load estimation is effective in exploring the capability of the proposed PSSM procedure. The Python program's ability to identify the floor under maximum load and determine the specific construction stage provides valuable insights for multi-story construction, enabling informed decision-making and optimization of construction methods.Practical implicationsHigh-rise construction in Indian cities is booming, though this trend is not shared by all the country's major metropolitan areas. The growing construction sector in urban cities demands rapid construction for efficient utilization of formwork to control the construction costs of project. The proposed procedure is the best option to optimize the formwork construction cost, construction cycle time, the suitable formwork system with optimum cost, concrete grade for the adopted level of shoring in partaking and many more.Originality/valueThe proposed PSSM reduces the calculation complexity of the existing simplified method. This is done by considering the identical slab stiffness and identical shore layout for uniform load distribution throughout the structure. This procedure utilizes a two-step load distribution calculation for clearing phase. Initially, the 66% prop load of highest floor level is distributed uniformly over the lower interconnected slabs. In the second step, the total prop load is removed equally from all slabs below it. This makes the load distribution user-friendly for the industry expert.

Experimental evaluation of flexural behavior of UHPFRC slabs utilizing local constituents

New ultra-high performance fiber reinforced concretes (UHPFRCs) are being developed throughout the world using locally-sourced materials to reduce financial and logistical burdens. Understanding force protection capabilities of these new materials requires experimental data that are useful for validating constitutive models or fast-running computational tools. Flexural performance of two UHPFRCs from different regions of the world are compared via one-way slabs subjected to uniform quasi-static loads. Results are also compared to a normal-strength concrete and two high-strength concretes from different regions. Results showed increased unconfined compressive strength of concrete leads to increased flexural resistance and stiffness. Furthermore, fiber reinforcement greatly increases flexural capacity in slabs but can cause brittle failure when combined with high reinforcement ratios of conventional reinforcement. While the UHPFRCs had different mechanical properties, both increased the maximum flexural capacity and showed potential for significantly improved performance for force protection applications.

Green synthesis of gold nanoparticles by engineered Escherichia coli for photodegradation of p-nitrophenol

Gold nanoparticles (AuNPs) are widely employed in the environmental, energy, and biomedical fields. The green synthesis of AuNPs is significant for reducing the hazardous chemicals and toxic byproducts of traditional synthesis procedures. In this study, engineered Escherichia coli (E. coli-GolR) capable of heterologous production of the gold-reducing protein (GolR) were constructed. Uniform and stable loading of AuNPs on E. coli-GolR were demonstrated by characterization. Experiments using live-dead cell labeling showed that E. coli-GolR was able to withstand the toxicity of AuIII. Within 5 min, 3 mM of 4-nitrophenol (4-NP) could be totally broken down by the acquired AuNPs@E. coli-GolR. More importantly, the AuNPs@E. coli-GolR could be recycled at least ten times, significantly decreasing the cost of their application. This work broadens the possibilities for using AuNPs by offering fresh insights into the microbial production of AuNPs.

Experimental investigation of moving contact pattern in helical planetary gearboxes

Planetary gear sets combine the characteristics of high-power density and compact design which are beneficial for a wide range of high-performance applications. Embedded in the efforts for resource efficiency and cost reduction, new challenges arise regarding a lightweight design. An accurate prediction of the load sharing on the individual planetary gears and especially of the load distribution of the meshing gears is of major importance. A uniform load distribution enables the design of the individual tooth meshes without load increases and oversizing. However, a varying load distribution has been observed in planetary gearboxes with respect to the rotation of the carrier which is caused by misaligned central shafts of the gearbox. This behavior is influenced by several factors, such as manufacturing and assembly deviations, the rigidity of shafts, housing and bearings, the number of planets, the quality of the gear wheels and the operating conditions. To determine the exact load distribution, detailed simulations or extensive experimental prototype tests are required. In an early design phase, these detailed boundary conditions are not yet defined and their effect on a moving contact pattern therefore cannot be reliably considered.Thus, in this paper an experimental investigation of the influencing factors on a varying load distribution with regard to the carrier rotation is presented. Based on experimental data recommendations for the design of planetary gearboxes are derived.

Analytical Solution for Bearing Capacity of Reinforced Strip Footings on Unsaturated Soils under Steady Flow

The study of analytical solutions for the bearing capacity of reinforced soil foundations is a very important topic in engineering mathematics. Existing evaluations of the foundation-bearing capacity on reinforced soils are based on dry conditions, while many foundations are located on unsaturated soils in real engineering. In this paper, a new formula for the bearing capacity of reinforced strip footings on unsaturated soils is presented. Two sliding failure mechanisms are constructed based on the position of the reinforcement layer relative to the sliding surface. The distribution of apparent cohesion in the depth direction is calculated by considering the effect of matrix suction. By additionally considering the work conducted by the reinforcement and the contribution of the apparent cohesion, the bearing capacity formula is obtained using the upper bound theorem of limit analysis. The bearing capacity solution is obtained by adopting the sequential quadratic programming (SQP) algorithm. Comparing the results under two failure mechanisms, the optimal bearing capacity and the optimal embedment depth of reinforcement are obtained. The results of this paper are consistent with those of the existing literature. Finally, the effects of reinforcement embedment depth, effective internal friction angle, uniform load, and unsaturated soil parameters on the optimal bearing capacity are investigated through parametric analysis. This paper provides useful recommendations for the engineering application of reinforced strip footings on unsaturated soils.

Transfer-Matrix Method for Calculus of Long Cylinder Tube with Industrial Applications

The Transfer-Matrix Method (TMM) is an original and relatively simple mathematical approach for the calculus of thin-walled cylindrical tubes presented in this work. Calculation with TMM is much less used than calculation with the Finite Elements Method (FEM), even though it is much easier to apply in different fields. That is why it was considered imperative to present this original study. The calculus is based on Dirac’s and Heaviside’s functions and operators and on matrix calculation. The state vectors, the transfer-matrix, and the vector corresponding to the external efforts were defined, which were then used in the calculations. A matrix relation can be written, which gives the state vector of the last section depending on the state vector of the first section, a relation in which the conditions of the two end supports can be set. As an application, a heat exchanger was studied, with a large cylinder subjected to a uniformly distributed internal load, and from the inner cylinder bundle, a cylinder subjected to both uniform internal and external loads was considered. For the second cylinder, two possibilities of action for the external forces were considered, a successive action and a simultaneous action, achieving the same results in both situations. The TMM is intended to be used for iterative calculus in optimization problems where rapid successive results are required. In the future, we want to expand this method to other applications, and we want to develop related programs. This is an original theoretical study and is a complement to the research in the field on thin-walled cylinder tubes and their applications in heat exchangers.