Rigid Base Research Articles

Theoretical optimization of functional graded micropillars for strong and durable bioinspired dry adhesion

Inspired by the prominent adhesion capability of gecko foot-hair, micro/nano-pillar array has been fabricated and widely explored as biomimetic dry adhesives. Pillars with graded material along their length have been proved to have great advantage in simultaneously raising adhesion and reducing clusterisation, yet the design of the graded micropillars lacks theoretical and quantitative guides. In this work, we first derived the theoretical expressions of critical aspect ratio and effective elastic modulus for graded micropillars composed of rigid bases and soft tips. Then, a Cohesive Zone Model (CZM) was constructed to simulate the lateral collapse of the two-step-graded micropillars with epoxy resin and polyurethane (typical materials adopted in the reported experiments) as the base and tip materials, respectively. Combining the numerical results and the theoretical ones, we found that when the length ratio of the rigid base to the micropillar increases, the ability of the pillars to resist structural collapse enhances (i.e., the critical aspect ratio raises), while the adhesion strength reduces (i.e., the effective elastic modulus increases). Considering the tradeoff between the structural stability and the adhesion strength, we found an optimum value of ∼0.65 for the length ratio of the rigid base to the whole micropillar. Our study establishes theoretical models for the critical aspect ratio and effective elastic modulus for the graded micropillars and provides quantitative guides to the design and optimization of bioinspired dry adhesives.

Analysis of G+5 Storeys Building With and Without Floating Column

In current period, several structures are being planned and built with structural complicatedness like building with floating columns on different floors and spaces. The buildings accompanying floating columns are extremely detrimental that is constructed in earthquake-prone regions. The current study analyses and compare the buildings with and without of floating column. The columns which are directly supported by a beam without any rigid base are known as floating columns. Various buildings have been constructed with floating columns in India. Typically, it is required to provide larger spacing between the columns to entertain the requirements of parking or reception lobbies. Some of the functional requirements of a building might be satisfied by providing the floating columns but the structural behaviour of the building changes abruptly. The beams that supported the floating columns require more flexure and shear demand than the surrounding beams. In addition, it leads to stiffness unevenness at a specific joint. Columns are the main structural elements that resist the lateral load in a rigid frame and have the importance in the performance of the building under earthquake load The storey’s stuffiness below the floating column is normally reduced. Therefore, an attempt has been made to analyse the performance of a G+5 storey building with and without floating columns and compare structural parameters such as horizontal displacement, storey drift and storey shear under seismic excitation using (ETABS) Software.

Study of the Distribution and Change Law of Stress in Subgrade Immersed in Water in the Hetao Irrigation Area

Abstract The Bayan Nur Section of the Jing-Xin Expressway is located in the Hetao irrigation area. In this area, open river flooding is employed to irrigate the farmland, which causes seasonal subgrade immersion. With the fluctuation in the water levels, the water content of the subgrade soil increases, and the soil strength decreases due to water infiltration and capillary action. Thus, a field test section is built for long-term monitoring of the earth pressure, pore pressure, and settlement, and gravel cushion and reinforcement materials are utilized to reinforce the foundation in the test section. The test results show that the tidal variation in the groundwater level is obvious during the irrigation season, with the maximum increase in the pore pressure being 147.7 %, and the highest water level being 0.9 m above the ground. The change of subgrade soil moisture content and subgrade buoyancy results in the change of subgrade base pressure direction. The pressure distribution of the subgrade base after the reinforcement of the sand-gravel cushion and geotechnical materials presents an inverted bell type, which is similar to the pressure distribution of the rigid foundation base. The restraint and tension film effect of the cushion and reinforcement materials helps in improving the rigidity of the subgrade base.

Experimental Study on Seismic Instability of Pile-Supported Structure Considering Different Ground Conditions

The stability of pile-supported structures under earthquake loads involves complex dynamic soil–structure interaction (SSI). A series of large-scale shaking table experiments was performed to investigate the seismic performance and SSI of pile-supported structures considering different ground conditions. Lateral soil resistance and dynamic displacements of superstructures located in nonliquefiable and liquefiable sites as well as a rigid foundation were measured during shaking tests. The measured responses were analyzed to investigate the P-Δ effect on structural stability. It was observed that the soil lateral resistance to the pile cap at the nonliquefiable site was large and represented the main component of the lateral bearing capacity resisting structure overturning. On the other hand, the lateral resistance of liquefied soil on piles was insignificant and the lateral bearing capacity was derived primarily from soil resistance to pile cap. The analysis of the measured dynamic displacements demonstrated that the seismic instability of the structure was mainly due to the P-Δ effect caused by the rotation of the foundation, especially in liquefied sites. In addition, comparison with the results of base shears and bending moments with the rigid base assumption allows for an in-depth discussion of the effect of SSI on structural seismic design.

Biomass-derived dynamic covalent epoxy thermoset with robust mechanical properties and facile malleability

Biomass-derived dynamic covalent thermoset has been considered as a promising solution to the high dependence on fossil resources and the difficulty in recyclability after curing of conventional bisphenol A epoxy resins. However, the design and preparation of a dynamic covalent biobased epoxy thermoset with both comparable thermal and mechanical performances to bisphenol A epoxy resins and reprocessibility remains a significant challenge. Herein, based on imine chemistry, a novel Schiff base-containing dynamic covalent epoxy thermoset was facilely fabricated from biobased protocatechualdehyde and synthetic siloxane diamine. Due to the more reactive epoxides in the epoxy monomer than in bisphenol A epoxy oligomer, the thermoset exhibited a high cross-linking density, resulting in high thermal stability and glass transition temperature. The rigid aromatic Schiff base moieties endowed the thermoset with excellent mechanical properties: Thanks to the plasticization of the flexible siloxane, the thermoset displayed high impact strength. Meanwhile, owing to the high segmental mobility, the fast exchange of imine bonds was guaranteed; and the thermoset was able to be recycled through reprocessing. Taking these features, this work provided great potential for designing and preparing sustainable substitutes for bisphenol A epoxy resins in the high-performance applications.

To Solution of Contact Problem for Elastic Half-Strip

Contact problems for elastic stripes have been well studied and published in domestic scientific literature. This is partly due to the fact that normative documents on the foundation structure it is recommended to use this elastic foundation model for simulation of a “structure – foundation – soil foundation” system. Two variants of boundary conditions at the contact between a half-strip and a rigid non-deformable base are usually considered. The first boundary condition nullifies the vertical displacements and tangential stresses, the second one nullifies vertical and horizontal displacements. Contact problems for an elastic half-strip are much less investigated. The paper considers this contact problem when the first boundary condition for zeroing of vertical displacements and tangential stresses at the contact of a half-strip with a rigid, nondeformable base. When performing calculations in the traditional formulation without taking into account tangential stresses in the contact zone, the Zhemochkin method has been used, which reduces the solution of the contact problem of solid mechanics to the solution of a statically indeterminate problem by the mixed method of structural mechanics. Therefore, at first, we have found the displacements of the upper edge of the half-strip from the unit load uniformly distributed over the edge section. The resulting expression is used to compose a system of equations for the Zhemochkin method. The case of translational displacement of the die has been considered, and the graph of contact stress distribution under the die's sole has been given in the paper.

Deciphering the mechanical properties of B‐DNA duplex

AbstractStructure and deformability of the DNA double helix play a key role in protein and small ligand binding, in genome regulation via looping, or in nanotechnology applications. Here we review some of the recent developments in modeling mechanical properties of DNA in its most common B‐form. We proceed from atomic‐resolution molecular dynamics (MD) simulations through rigid base and base‐pair models, both harmonic and multistate, to rod‐like descriptions in terms of persistence length and elastic constants. The reviewed models are illustrated and critically examined using MD data for which the two current Amber force fields, bsc1 and OL15, were employed.This article is categorized under: Structure and Mechanism > Molecular Structures Structure and Mechanism > Computational Biochemistry and Biophysics Molecular and Statistical Mechanics > Molecular Dynamics and Monte‐Carlo Methods

Rutting prediction models for asphalt pavements with different base types based on RIOHTrack full-scale track

Asphalt mixture is a typical viscoelastic-plastic material and rutting deformation is very common in asphalt pavement. Considerable empirical and mechanistic-empirical (M−E) rutting prediction models are established to evaluate rutting performance. However, these models lack reliable database, and the mode applicability to different asphalt pavement structures is still not clear. Based on the field data from RIOHTrack full-scale track, this paper aims to establish more accurate and suitable empirical or M−E models for different asphalt pavement structures. Firstly, main influence factors were analyzed and the field database was determined; then, model frameworks and parameters were constructed; next, prediction models using empirical and M−E methods were established respectively; lastly, the model applicability was clarified, and the mechanism of base type influence on rutting performance was also analyzed. Results show that the proposed M−E model is suitable for semi-rigid or rigid base asphalt pavement (SBAP or RBAP), while the exponential-empirical (E-E) model is appropriate for flexible base asphalt pavement (FBAP). The base type has great influence on rutting performance and deformation mechanism. The model development and selection process could be used to find a suitable rutting prediction model for different asphalt pavement structures in other area. These findings also contribute to clarifying the rutting deformation mechanism and pavement maintenance.

MP10-15 EXAMINING THE IMPACT OF DIFFERENT PROPERTIES OF URETERAL ACCESS SHEATHS IN REDUCING INSERTION FORCE DURING RETROGRADE INTRARENAL SURGERY: AN IN VITRO STUDY

You have accessJournal of UrologySurgical Technology & Simulation: Instrumentation & Technology I (MP10)1 Sep 2021MP10-15 EXAMINING THE IMPACT OF DIFFERENT PROPERTIES OF URETERAL ACCESS SHEATHS IN REDUCING INSERTION FORCE DURING RETROGRADE INTRARENAL SURGERY: AN IN VITRO STUDY Shinji Fukui, Takashi Yoshida, Kazuyoshi Nakao, Taiji Abe, Hidefumi Kinoshita, and Tadashi Matsuda Shinji FukuiShinji Fukui More articles by this author , Takashi YoshidaTakashi Yoshida More articles by this author , Kazuyoshi NakaoKazuyoshi Nakao More articles by this author , Taiji AbeTaiji Abe More articles by this author , Hidefumi KinoshitaHidefumi Kinoshita More articles by this author , and Tadashi MatsudaTadashi Matsuda More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000001983.15AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: This study aimed to evaluate the characteristics of ureteral access sheaths (UASs) that can reduce the insertion force while accessing the upper urinary tract. METHODS: Six different types of 12/14-Fr UASs were used. We evaluated the properties of UASs such as the diameter of the outer sheath, length of the inner dilator tip exposed from the outer sheath, sheath flexibility (assessed in terms of bending force of the tip or base), flexibility ratio (i.e., bending force value of tip-to-base ratio), and frictional force of the outer sheath surface. We measured the force required for inserting the UAS into an artificial ureteral model and examined the correlation between the relevant characteristics and insertion force for each UAS. RESULTS: Overall, a lower tip-to-base flexibility ratio (r=0.66) and a lower frictional force (r=0.50) were inversely correlated with insertion force. The force of insertion into the bifurcation was associated with the flexibility of the base (r=-0.64), flexibility ratio (r=0.79), and frictional force (r=0.66). Moreover, a shorter dilator tip (r=0.52), lower flexibility ratio (r=0.52), and lower frictional force (r=0.50) were correlated with a lower insertion force at the proximal ureter. CONCLUSIONS: A UAS with a rigid base and flexible tip parts, a smoother surface, and a shorter dilator tip would be preferable for reducing the insertion force. These findings may be crucial for selecting or developing an ideal UAS that can decrease the risk of ureteral injury. Source of Funding: Not applicable © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e174-e174 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information Shinji Fukui More articles by this author Takashi Yoshida More articles by this author Kazuyoshi Nakao More articles by this author Taiji Abe More articles by this author Hidefumi Kinoshita More articles by this author Tadashi Matsuda More articles by this author Expand All Advertisement Loading ...

Simulation of New Multilayer Waveguides by Explosion Welding

The possibility of obtaining multilayer cylindrical waveguides by explosion welding is investigated. The fact that the technological welding scheme has a significant impact on the shaping of workpieces and the value of edge effects was established. The studies demonstrated that the nature of wave formation during the manufacture of multilayer cylindrical waveguides from a homogeneous material by explosion welding using a central rod is identical to the wave formation when welding flat multilayer compositions on a rigid base.

Dry-whip phenomenon in on-board rotordynamics: Modeling and experimentation

This paper addresses rotor–stator contact issues, especially the dry-whip phenomenon, as caused by base excitations. So far, this particular instability in the case of direct rub between shaft and stator was only shown by experiments to occur in response to mass unbalance excitation during run-up or run-down and/or to external disturbance such as direct impact applied to the rotor. The present paper aims to demonstrate that it can also be triggered by external forces coming from the rigid base motion. To this end, both numerical and experimental approaches are employed. A rotor finite element model combining on-board motions with shaft-stator rub impact is first proposed. This model is validated with a rotor test-rig supported by hydrodynamic bearings and mounted on a multi-axial hydraulic shaker and subject to a harmonic base motion. The dry-whip is then shown experimentally by using a base shock excitation consisting of two transverse translations, which is later confirmed numerically. The influence of important parameters on the dynamic behavior of the system is also assessed, such as the hydrodynamic bearing nonlinearities, the amplitude and direction of the base translations and the dry friction coefficient.

2-Pyridinecarboxaldehyde-based Schiff base as an effective corrosion inhibitor for mild steel in HCl medium: Experimental and computational studies

A new rigid double Schiff base of N,N′-(1,3-phenylene)bis(1-(pyridin-2-yl)methanimine) (PBPM) as a novel corrosion inhibitor was successfully synthesized and characterized in this work. The corrosion inhibition performance of PBPM for mild steel in 1.0 mol L−1 HCl medium was evaluated via weight loss measurements, electrochemical methods, scanning electron microscopy, contact angle measurements and quantum chemical calculations. The inhibition efficiency of PBPM is dependent on the concentration of PBPM and the test temperature. The highest inhibition efficiencies obtained by potentiodynamic and weight loss measurements in the presence of 800 mg L−1 PBPM at 30 °C were 93.93% and 94.04%, respectively. Potentiodynamic polarization tests showed that PBPM acts as an effective mixed-type corrosion inhibitor. The adsorption of PBPM on the surfaces of mild steel was found to obey Langmuir adsorption isotherm, with both physisorption and chemisorption. Scanning electron microscopy analyses affirmed the formation of a protective film on mild steel surfaces. Contact angle measurements revealed the hydrophobic nature of the surface modified by PBPM molecules applied in acidic corrosive solution. Furthermore, the influence of the molecular configuration of PBPM on the corrosion inhibition behaviour was investigated by DFT calculations and Fukui functions, and the protonated behaviour of PBPM in acidic system was also analysed.

Examining the Impact of Different Properties of Ureteral Access Sheaths in Reducing Insertion Force During Retrograde Intrarenal Surgery: An In Vitro Study

Background and Purpose: This study aimed to evaluate the characteristics of ureteral access sheaths (UASs) that can reduce the insertion force while accessing the upper urinary tract. Materials and Methods: Six different types of 12/14F UASs were used. We evaluated the properties of UASs such as the diameter of the outer sheath, length of the inner dilator tip exposed from the outer sheath, sheath flexibility (assessed in terms of bending force of the tip or base), flexibility ratio (i.e., bending force value of tip-to-base ratio), and frictional force of the outer sheath surface. We measured the force required for inserting the UAS into an artificial ureteral model and examined the correlation between the relevant characteristics and insertion force for each UAS. Results: Overall, a lower tip-to-base flexibility ratio (r = 0.66) and a lower frictional force (r = 0.50) were inversely correlated with insertion force. The force of insertion into the bifurcation was associated with the flexibility of the base (r = -0.64), flexibility ratio (r = 0.79), and frictional force (r = 0.66). Moreover, a shorter dilator tip (r = 0.52), lower flexibility ratio (r = 0.52), and lower frictional force (r = 0.50) were correlated with a lower insertion force at the proximal ureter. Conclusion: A UAS with a rigid base and flexible tip parts, a smoother surface, and a shorter dilator tip would be preferable for reducing the insertion force. These findings may be crucial for selecting or developing an ideal UAS that can decrease the risk of ureteral injury.

Effects of dynamic soil-structure interaction on seismic behaviour of high-rise buildings

It is conventional to assume that the role of the soil-structure interaction (SSI) is beneficial to the buildings under seismic loading. However, lessons learned from recent earthquakes revealed that this assumption could be misleading, and SSI may have different effects on the seismic response of different structural systems. In this study, an enhanced soil-structure numerical model is developed and verified using ABAQUS software to assess the impact of SSI on high-rise frame-core tube structures. The seismic responses of 20, 30, and 40-storey buildings constructed on soil class Ee (according to Australian Standards) under four earthquake acceleration records have been studied. The results in terms of maximum lateral deflections, foundation rocking, inter-storey drifts and storey shear forces for the rigid base and flexible base frame-core tube structures have been discussed and compared. Generally, SSI has a remarkable impact on the seismic behaviour of high-rise frame-core tube structures since it can increase the lateral deflections and inter-storey drifts and decrease storey shear forces of structures. However, It is worth noting that the seismic responses of soil-structure systems under near and far field earthquakes are considerably different.

Ensuring adhesion between the asphalt-concrete road surface and rigid base at the roadbed design stage

Arranging asphalt-concrete layers on a rigid base in the form of cement-concrete slabs can significantly improve the transporting and operational performance of the road surface. Such a structural solution is appropriate in almost all countries of the world since cement-concrete slabs retain high strength for a long time. To prevent the rapid destruction of an asphalt-concrete road surface on a rigid base, it is necessary to ensure reliable adhesion between the layers' contacts and, at the design stage, to test the adhesion strength by estimation. This paper has substantiated a criterion of adhesion strength in the contact between an asphalt-concrete road surface and the rigid base. The calculation involves comparing the active tangent stresses in the contact between layers dependent on the effect of the vertical and horizontal components of the transport load with the magnitude of permissible tangent shear stresses in the contact of layers. The parameters for an estimation model have been established; the stressed-strained state of the roadbed structure has been simulated using a finite element method. When modeling the stressed-strained state and calculating based on the strength criterion, different vehicle traffic conditions have been considered, as well as the effect of temperature on the strength parameters of the asphalt-concrete layer and the tar layer. The conditions for vehicle movement, taken into consideration when designing, correspond to the conditions of movement along the road, along the curves in the plan and profiles, and notion conditions at car emergency braking. Practical recommendations have been compiled for assigning the minimum permissible thickness of an asphalt-concrete layer on a rigid base, which must be followed at the design stage due to the condition for ensuring reliable adhesion between the layers' contacts. The minimum permissible thickness ranges from 2 cm to 10 cm, depending on the conditions of movement, temperature, and the type of tar.

Elastodynamic Solutions of a Finite Soil Layer under Interior Distributed Actions

Through a method of displacement potentials, Fourier series, and Hankel integral transformation, the generalized solutions of an elastic layer resting on a rigid base under arbitrary, distributed, buried, and time-harmonic loads are developed in this study. With the proposed solution, the specific results for two kinds of uniform distributions as a kind of fundamental solutions in the interaction analysis of media and inclusions by the method of boundary integral equations are included as illustrations. Finally, numerical examples involving surface and buried patch loads are presented to validate the solutions and examine the effects of the thickness of the elastic layer. The results show that the proposed solution can cover the classical half-space solution by taking enough large thickness of the elastic layer (e.g., the ratio of the layer thickness beneath the load to the load radius ≥ 50 ) and the surface load solution by setting the load depth to zero; the underlying rigid base has significant and complex influence on the dynamic response of the thin layer due to wave reflections, which needs to be considered in the design and practice of related engineering.

Concrete Modular Pavement Structures with Optimized Thickness Based on Characteristics of High Performance Concrete Mixtures with Fibers and Silica Fume.

Usually, C30/37 strength class concrete is used to construct concrete pavements on a rigid, semi-rigid or flexible base. Concrete with such a strength delivers essential design characteristics: flexural strength and tensile splitting strength are between 4.5–5.4 MPa and 2.8–3.7 MPa, respectively. Design characteristics can be significantly increased by densifying the concrete mixture, i.e., adding silica fume, steel or polypropylene macro fibers. As high-performance concrete characteristics are 20–60% higher than those for standard concrete (C30/37), new possibilities to reduce the thickness of concrete pavement slabs appear. The theoretical analysis of concrete pavement structures with high-performance concrete mixtures (C40/50, C45/55 and C50/60) showed that slab thickness could be reduced by 6–39% compared to a standard concrete pavement structure depending on the concrete properties and design method. From all those pavement structures, three concrete mixtures were determined as the most rational ones in terms of PCP thickness reduction and total pavement cost: (i) with 49.5 kg/m3 of steel fibers and 25.2 kg/m3 of silica fume; (ii) with 10.0 kg/m3 of polypropylene fibers (type A); (iii) with 49.5 kg/m3 of steel fibers.

A hybrid piezoelectric device combining a tri-stable energy harvester with an elastic base for low-orbit vibration energy harvesting enhancement

How to efficiently harvest the low-orbit vibration energy over a wide frequency range is one main challenge of the piezoelectric energy harvester. In this paper, combining the advantages of elastic base (EB) and the interaction of coupled elastic system, a hybrid piezoelectric device combining a tri-stable piezoelectric energy harvester (TPEH) with an EB is presented to enhance the harvesting ability of the low-orbit vibration energy. The EB composed of a mass and spring can amplify the low-orbit vibration and provide the TPEH enough kinetic energy to overcome the potential barrier and jump to the high-orbit oscillation, resulting in an even better operating bandwidth and higher power generation. The nonlinear electromechanical model describing the dynamic responses of the presented harvester is derived. The effects of the mass ratio and stiffness ratio on the dynamic performances of the hybrid energy harvester are numerically investigated with dynamic bifurcation diagrams method. The results show that the presented harvester has wider frequency bandwidth and higher power generation than those of the TPEH with rigid base by properly selecting the mass ratio and stiffness ratio, and it can more easily snap-through from low-orbit oscillation to high-orbit oscillation to reach larger dynamic response at lower excitation levels. Experiments are conducted to validate the simulations, and the experimental results are in good agreement with the theoretical results. Finally, fluencies of the load resistance on the power generation are also experimentally studied, and an optimum load resistance to achieve the peak power is obtained.

An effective method for the frictional thermoelastic contact of a cylindrical punch on a piezoelectric layer

In this study, the plane steady state thermoelastic frictional contact problem between a rigid cylindrical punch and a homogenous piezoelectric layer bonded to the rigid base is considered. The punch is assumed to be a perfect electric conductor and thermal insulator and slides over the piezoelectric layer with a small constant speed and heat flux is generated due to the friction. The general stress, displacement, and electrical expressions for the thermoelastic piezoelectric contact problem are derived using the theory of thermoelasticity and Fourier integral transform technique. Applying the boundary conditions, the present problem is reduced to Cauchy-type singular integral equations of the second kind in which the contact stress, the electrical displacement, and the contact width are unknown. The singular integral equations are solved numerically using Gauss–Jacobi and Gauss–Chebyshev integration formula with a developed effective method. The effect of moving velocity, friction coefficient, external load, electric charge, punch radius, and layer height on the contact stress, in-plane stress, electric displacement, and generated temperature are discussed in detail. This work is the first study that investigates a cylindrical punch on a thermoelastic contact of a piezoelectric layer.

About Earthquakes in Subduction Zones with the Potential to Cause a Tsunami

The problem of occurrence of starting earthquakes in subduction zones is considered. Subduction is the phenomenon of movement of the oceanic lithospheric plate under the continental one. The oceanic lithospheric plate at a certain depth melts from below and can slide. The paper considers the occurrence of starting earthquakes under the assumption that lithospheric plates have different contact conditions, being on a rigid base in the subduction zone. A molten lithospheric plate has no tangential contact stresses, while the other, oceanic, is rigidly connected to the base. The block element method is used to study the occurrence of the starting earthquake and the peculiarity of its consequences. The conditions to generate of tsunamis as a result of such earthquakes are being studied. Solutions to boundary value problems that are constructed precisely, rather than approximatively, allow us to reveal the mechanisms of destruction of the environment that were not previously known. In particular, the results obtained allowed us to detect a new type of crack that was not previously described. They destroy the environment in a different way than Griffiths cracks, which is demonstrated in this paper and is important in engineering practice.