Rigid Elements Research Articles

ПРЕДПОСЫЛКИ ФОРМИРОВАНИЯ АРХИТЕКТУРЫ ВРЕМЕННЫХ ЖИЛИЩ ДЛЯ ЗОН ЧРЕЗВЫЧАЙНЫХ СИТУАЦИЙ РОССИЙСКОЙ ФЕДЕРАЦИИ

The article examines the role of temporary shelters in recovery programs for emergency zones of the Russian Federation. The frequency of natural disasters and emergencies is analyzed, as well as a number of problems associated with the need to resettle the affected population in the existing housing stock of settlements located in territories adjacent to the emergency zone or resettlement of the affected to other regions.
 The features of the use of temporary accommodation centers, both stationary and mobile, the possible duration of their use are considered, the provision of the regions of the Russian Federation with them is analyzed. A review of existing research works and developed solutions for mobile housing for temporary stay is carried out on the example of domestic and foreign works.
 The relevance of further research in the issue of determining common problems, patterns and technical solutions in the formation of temporary dwellings for emergency zones of the Russian Federation in the context of further development of principles is substantiated. Goals, boundaries, novelty, tasks of further research are highlighted. For the first time, the question of the possibility of using transforming mobile buildings from rigid elements as temporary housing for emergency zones in the Russian Federation is raised as part of a general study on the formation of principles.

Collision Simulation of a Floating Offshore Wind Turbine Considering Ductile Fracture and Hydrodynamics Using Hydrodynamic Plug-in HydroQus

This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

Simplifying Raupach's model of shear‐stress partitioning by clarifying the relationship between β and σ and quantifying the shear‐stress probability density based on numerical simulation

AbstractWe used computational fluid dynamics to simplify Raupach's model by clarifying the relationship between the parameter β (the ratio of element to surface drag coefficients) and the roughness‐element shape parameter σ using a k‐ω shear‐stress transport (SST) turbulence model with rigid cylindrical roughness elements. Results showed that β ranged between 102 and 242 and the parameter m (a relationship between the average and the peak surface shear stresses) ranged between 0.15 and 0.32 for partitioning of surface shear stress. β decreased with increasing σ, and the relationship followed a power law. We confirmed this relationship by comparing wind tunnel and field measurements for different types of roughness element (blocks, hemispheres, trapezoids and plants based on the results from previous studies). However, the model has some limitations due to the characteristics such as streamline and porosity of plants. The peak mean stress ratio (a) ranged between 2.09 and 3.61. We also confirmed that the probability‐density function for the surface shear stress proposed by Zou et al. (2022) described the distribution of the surface shear stress among roughness elements well, which is essential to accurately estimate surface erosion by wind.

A Partitioned Rigid-Element and Interface-Element Method for Rock-Slope-Stability Analysis

The stability analysis of rock slopes has been a prominent topic in the field of rock mechanics, primarily due to the widespread occurrence of discontinuous structural planes in rock masses. Based on this complex characteristic of rock slopes, this paper proposes a novel numerical method, the Partitioned-Rigid-Element and Interface-Element (PRE-IE) method. In the PRE-IE method, the structure is modeled as several rigid bodies and discontinuous structural planes, which are, respectively, divided into partitioned rigid elements and interface elements. Taking the contact force of node pairs and the displacement of the rigid body centroid as mixed variables, according to the principle of minimum potential energy, the governing equations of PRE-IE can be established using the Lagrange multiplier method and then solved using the nonlinear contact iterative method and the incremental method. A classic case study demonstrates that using the failure of all contact node pairs as the criterion for slope failure is appropriate. This criterion is objective and avoids the potential impact of personal bias on safety factor calculations. Two numerical examples of differently shaped slopes are provided to verify the correctness and validity of the PRE-IE method. By comparing the safety factor calculated using the PRE-IE method with those obtained from other different methods, as well as comparing the computational time, it is shown that the PRE-IE method, in combination with the SRM, can accurately and efficiently analyze the stability problems of rock slopes.

Seismic behavior analysis of the kindergarten projects designed as an alternative to the type project examples in Turkey

Pre-school education buildings are very important places in the physical and psychological development of children. These buildings have to meet certain needs. In Turkey, which is located on active faults in the Alpine-Himalayan seismic belt, one of the most important of these needs is earthquake resistance. According to the Turkish Building Earthquake Code, kindergartens are among the buildings with the highest building importance coefficient. The design and construction process of kindergartens in Turkey is carried out by the Turkish Ministry of National Education. In order to provide a standardization in the design process, “Type Project” has been applied since the 1970s. Type projects are standard projects built in different parts of the country and usually consist of rectangular forms. Although rectangular forms offer a useful solution in providing sufficient strength, sufficient ductility and sufficient rigidity elements, it is thought that different geometries can be used in the design of kindergarten buildings that consist of at most 2 floors and need a very small floor area.In this study, kindergarten buildings are discussed in terms of earthquake resistance. The type project example developed by the Ministry of National Education and the circular form project developed as an alternative to this were modeled using the finite element method. With these modeled projects, the differences of dynamic behavior between the rectangular form and the circular form determined during the kindergarten design process were compared. The structural system of the designed kindergarten buildings has been analyzed as 1st and 4th degree earthquake zone and local ground class Z4 by the response spectrum method.As a result, it has been observed that the different forms chosen in buildings with small spatial needs such as kindergartens can respond to the spatial requirements and the required earthquake resistance.

Hügelschäffer Egg Curves as Transition Curves in Road Design

Roads and railways, as the main parts of traffic infrastructure, represent geometrically rigid elements which are hard to adapt to certain kinds of landscapes without making large changes to the terrain itself. Today, thanks to modern technology and a large number of software tools, it is possible to define new geometric curves which are easily adaptable for use as transition curves when designing roads or railways. These transition curves can be formed in such a way to make them fit in with the surrounding landscape or urban environment better, which can improve the aesthetics of the transport system. Furthermore, transition curves provide a smooth and gradual change of curvature, reducing the risk of sudden curvature changes, which can cause discomfort to passengers and create an unsafe situation, such as a loss of vehicle control or a train derailment. Accordingly, in this paper, we define the parameters for generating Hügelschäffer curves as new transition curves between two circular road segments.

Modified ultimate bearing capacity formula of strip footing on sandy soils considering strength non-linearity depending on stress level

Most of the contemporary ultimate bearing capacity (UBC) formulas assume a linear yield function in shear stress-normal stress space. However, experimental investigations have corroborated the non-linearity in the failure envelopes of sandy soils. This study focused on the assessment of the stress level effect on the UBC of surface strip footings ascribed to the soil unit weight (γ), footing size (B), and uniform surcharge load (q). The rigid plastic finite element method (RPFEM) was employed for the analysis. The analysis method was validated against the centrifuge test results from the published references in the case of various sandy soils with different relative densities. The RPFEM, using the mean confining stress dependence property of Toyoura sand, is utilized in non-linear finite element analysis of model sandy soil. The normalized ground failure domains in the case of the non-linear shear strength model are gleaned smaller than those in the case of the linear shear strength one. The numerical results are compared with the guidelines of the Architectural Institute of Japan (AIJ) and the Japan Road Association (JRA). The modification coefficients are ascertained for the frictional bearing capacity factor (Nγ) and surcharge bearing capacity factor (Nq), and a modified UBC formula is proposed. The performance of the proposed UBC formula is examined against the analysis results and various prevailing UBC guidelines.

Experimental Evaluation of Vibrational Stability of SOPs in Aerospace Industry Using PCB Strain Effectiveness of a PCB-Strain-Based Design Methodology

Steinberg’s theory, which is based on the fatigue failure theory, has been widely used for predicting the structural safety of solder joints in aerospace electronic units under vibration during launches. However, theoretical limitations are encountered when evaluating the structural safety of highly integrated electronic packages mounted on printed circuit boards (PCBs) under various boundary conditions. Therefore, in our previous study, a PCB-strain-based methodology was proposed to overcome the technical limitations of the conventional Steinberg theory, and its effectiveness was validated by conducting fatigue life tests on various types of specimens, such as the ball grid array, column grid array, and quad flat package. In this study, the aim was to increase its completeness and reliability by targeting small outline packages (SOPs) that have not yet been considered. The finite element (FE) model of the SOP was proposed to guarantee the reliable prediction of the structural safety of the solder joints used in the PCB-strain-based methodology. The proposed modeling technique contributes to enable the rapid construction of an FE model for the electronic unit because it was greatly simplified into a zero-dimensional lumped mass and rigid link element to simulate the package mass and solder joint, respectively. The effectiveness of the methodology was validated by performing fatigue life tests on PCB specimens under various boundary conditions. Those experimental and analytical results indicated that the proposed methodology was much more effective in predicting the structural safety of a solder joint for various cases of tested specimens compared with the Steinberg’s theory. The simplified FE model of SOP with the rigid link element connected to six points on the package mounting area of the PCB was effective for estimating margin of safety of solder joint. The results of this study would contribute to increase the availability of the proposed methodology for rapid mechanical design of electronic units in aerospace industries.

3D numerical investigation of flow behavior in an open channel with uniform and layered vegetation patches under varying submergence conditions

Staggered vegetation patches (central and outer) in an open channel have a significant effect on flow structure and river geomorphology. Although investigation on vegetation patches has been done in the past, however none of the past studies was carried out for varying submergence conditions from outer to central patches or for layered staggered patches with varying submergence. This knowledge gap has been attempted to bridge in this study. In this research work, a numerical technique has been used to analyze the flow behavior in a riverine flow by modeling central and outer vegetation patches as rigid elements in a rectangular channel. The influence of various vegetation patch configurations and submergence conditions were studied on flow characteristics. Computational fluid dynamics (CFD) package FLUENT was used for simulation purposes. Results showed that the flow in the central region of the channel was highly non-uniform, having a longitudinal distribution of velocities with alternating peaks and troughs throughout the central portion of the channel. However, in the outer regions, the velocity pattern acquired sawtooth distribution inside the patch regions (PR) but stabilized in the free regions (FR). Outer FR has 9% less velocities as compared to central FR. Moreover, the inflection point in velocity profiles and the bulge in contour plots was observed which triggered the shear layer at the top of submerged vegetation and at the interface of outer FR and central PR or vice versa. A complex pattern of secondary flow was also observed due to the turbulence anisotropy in the channel and its magnitude ranged from 0.1 to 3.7% of average velocity U. The results also showed that the state of submergence has a notable effect on the flow blockage and percentage of discharge passing through various regions.

(Ex)Change of Routines: An Action-Based Microfoundation

Change necessitates companies to alter their established routines. But how flexible are routines, and how can they be changed? Research has given very different answers to this question. While some researchers see routines as rigid and opposed to change, others see them as flexible and a source of change. The problem is not only that these positions are unrelated, but that there is no foundation that conceptually encompasses and connects both elements of routines, rigidity and changeability, which is why these two facets currently present as opposites. Current research tends towards the second position, neglecting the rigidity of routines. This paper offers an action-based microfoundation of routine change expanding Feldman and Pentland’s ostensive-performative approach beyond feedback processes. The focus of the theoretical conceptualization of routines is on action-specific knowledge acquired and applied through repetition. This action-based microfoundation allows the contradictory views of previous research to be positioned in a larger context. Routines are flexible, but only incrementally; they exhibit rigidity towards radical change. Building on this theoretical conceptualization, this paper distinguishes four types of routine changes: routinization/expansion, adaptation, problem fixing, and deliberate routine exchange. This distinction can contribute significantly to the focus of research and thus make it more rigorous. It also allows the rigidities of routines to be taken into account more strongly than before, thereby significantly increasing the relevance of routine research.

Modelling 3D dynamics of offshore lattice jib cranes by means of the rigid finite element method

Offshore cranes require particularly careful design due to the difficult environmental conditions in which they work. This paper presents a 3D model of the dynamics of an offshore crane with a truss jib formulated by means of the rigid finite element method. The inertial features of the truss members are assigned to nodes whose rotational and translational displacements are degrees of freedom. Flexible features of the truss members are modelled by massless and dimensionless spring–damping elements (sde). The computer programme developed on the basis of the model is verified and validated, and good correspondence of the authors’ own results with those obtained using commercial FEM package is achieved. Computer simulations are carried out for the light crane used on the wind platforms. The influence of the base movements (sea waves) on the system are also investigated. Lifting a load from a supply vessel and the load on the system during rotational movement of the crane are simulated too. Finally, conclusions concerning the influence of the movement conditions on the overload coefficient and deflections of the crane boom are formulated.

Study of Strain-rate Effect in Two-dimensional Biaxial Test on Granular Material using Discrete Element Method

Numerical study to investigate the effect of various strain rates on global friction angle in the sand has been performed. Granular material behavior is influenced by several factors, among others: pack configuration, grain macro and micro roughness, confinement pressure, loading rate, etc. Sand is a granular material composed of discrete particles that the most refined microscopic techniques are needed to study its mechanical properties. In Indonesia, research related to the Discrete Element Method is still very limited. The two-dimensional discrete element method is capable to calculate the motion and interparticle contacts of large number of small particles, and each particle is modeled as a rigid circular element. The study started with the validation of the DEM model using YADE. Particles with a local friction angle of 35° are arranged in a closed rectangular box (frictionless wall). The number of particles used in this model validation simulation is 1000 sphere-type particles with monodisperse particle gradations. The simulation was done by a drained biaxial test with confinement stress of 100 kPa, thereafter varying strain rate are applied. Based on the deviatoric stress–axial strain curve from YADE, the result can be depicted on the Mohr circle to obtain the value of the global friction angle. It is found that the different value of strain rate affects its global friction angle. Increasing the value of the strain rate can increase the material global friction angle, which increases the strain rate from 1% to 5%, 10%, 25%, and 50% will increase its global friction angle by 5%, 5%, 14%, and 18%, respectively.

Development and Optimization of 3D-Printed Flexible Electronic Coatings: A New Generation of Smart Heating Fabrics for Automobile Applications.

Textile-based Joule heaters in combination with multifunctional materials, fabrication tactics, and optimized designs have changed the paradigm of futuristic intelligent clothing systems, particularly in the automobile field. In the design of heating systems integrated into a car seat, conductive coatings via 3D printing are expected to have further benefits over conventional rigid electrical elements such as a tailored shape and increased comfort, feasibility, stretchability, and compactness. In this regard, we report on a novel heating technique for car seat fabrics based on the use of smart conductive coatings. For easier processes and integration, an extrusion 3D printer is employed to achieve multilayered thin films coated on the surface of the fabric substrate. The developed heater device consists of two principal copper electrodes (so-called power buses) and three identical heating resistors made of carbon composites. Connections between the copper power bus and the carbon resistors are made by means of sub-divide the electrodes, which is critical for electrical-thermal coupling. Finite element models (FEM) are developed to predict the heating behavior of the tested substrates under different designs. It is pointed out that the most optimized design solves important drawbacks of the initial design in terms of temperature regularity and overheating. Full characterizations of the electrical and thermal properties, together with morphological analyses via SEM images, are conducted on different coated samples, making it possible to identify the relevant physical parameters of the materials as well as confirm the printing quality. It is discovered through a combination of FEM and experimental evaluations that the printed coating patterns have a crucial impact on the energy conversion and heating performance. Our first prototype, thanks to many design optimizations, entirely meets the specifications required by the automobile industry. Accordingly, multifunctional materials together with printing technology could offer an efficient heating method for the smart textile industry with significantly improved comfort for both the designer and user.

Catalyst-Substrate Helical Character Matching Determines the Enantioselectivity in the Ishihara-Type Iodoarenes Catalyzed Asymmetric Kita-Dearomative Spirolactonization.

Catalyst design has traditionally focused on rigid structural elements to prevent conformational flexibility. Ishihara's elegant design of conformationally flexible C2-symmetric iodoarenes, a new class of privileged organocatalysts, for the catalytic asymmetric dearomatization (CADA) of naphthols is a notable exception. Despite the widespread use of the Ishihara catalysts for CADAs, the reaction mechanism remains the subject of debate, and the mode of asymmetric induction has not been well established. Here, we report an in-depth computational investigation of three possible mechanisms in the literature. Our results, however, reveal that this reaction is best rationalized by a fourth mechanism called "proton-transfer-coupled-dearomatization (PTCD)", which is predicted to be strongly favored over other competing pathways. The PTCD mechanism is consistent with a control experiment and further validated by applying it to rationalize the enantioselectivities. Oxidation of the flexible I(I) catalyst to catalytic active I(III) species induces a defined C2-symmetric helical chiral environment with a delicate balance between flexibility and rigidity. A match/mismatch effect between the active catalyst and the substrate's helical shape in the dearomatization transition states was observed. The helical shape match allows the active catalyst to adapt its conformation to maximize attractive noncovalent interactions, including I(III)···O halogen bond, N-H···O hydrogen bond, and π···π stacking, to stabilize the favored transition state. A stereochemical model capable of rationalizing the effect of catalyst structural variation on the enantioselectivities is developed. The present study enriches our understanding of how flexible catalysts achieve high stereoinduction and may serve as an inspiration for the future exploration of conformational flexibility for new catalyst designs.

Soft Deployable Structures via Core-Shell Inflatables.

Deployable structures capable of significant geometric reconfigurations are ubiquitous in nature. While engineering contraptions typically comprise articulated rigid elements, soft structures that experience material growth for deployment mostly remain the handiwork of biology, e.g., when winged insects deploy their wings during metamorphosis. Here we perform experiments and develop formal models to rationalize the previously unexplored physics of soft deployable structures using core-shell inflatables. We first derive a Maxwell construction to model the expansion of a hyperelastic cylindrical core constrained by a rigid shell. Based on these results, we identify a strategy to obtain synchronized deployment in soft networks. We then show that a single actuated element behaves as an elastic beam with a pressure-dependent bending stiffness which allows us to model complex deployed networks and demonstrate the ability to reconfigure their final shape. Finally, we generalize our results to obtain three-dimensional elastic gridshells, demonstrating our approach's applicability to assemble complex structures using core-shell inflatables as building blocks. Our results leverage material and geometric nonlinearities to create a low-energy pathway to growth and reconfiguration for soft deployable structures.

Explicit approach for the in-plane cyclic behaviors of unreinforced masonry structures using finite particle method

Masonry structures, especially historical ones, are vulnerable to earthquakes. Their structural performance subjected to cyclic loadings such as earthquakes should be fully understood before retrofitting. This study proposes an explicit approach for analysis of the in-plane cyclic behavior of masonry structures, combining the finite particle method and an elaborated mesoscale model. The proposed approach is intrinsically dynamic, and it can deal with both quasi-static and dynamic problems in the same framework. Specifically, kinetic damping and static convergence criteria are incorporated to accelerate quasi-static analysis. In the modeling, the rigid element is proposed for bricks based on rigid-body motion assumption. The zero-thickness interface element for mortar joints is derived, and the plastic behaviors in the tension regime, shear regime, and composite regime are developed. Specifically, the strength softening, residual plastic displacement, and stiffness degradation during cyclic loadings are fully considered. A single-story masonry wall subjected to quasi-static loads is analyzed, and the crack lines and horizontal force – rotation curve agree well with those in the experiment. The behavior of a two-story masonry wall subjected to seismic loads is then investigated, and the crack pattern and the first-order frequencies before and after cracking agree well with those in the shaking table test. The results indicate a decrease of the natural frequencies as well as story stiffnesses due to fracture in the mortar joints.

An improved numerical model for locomotive tensegrity systems based on vector form intrinsic finite element

Locomotive robot based on tensegrity has recently drawn much attention due to its lightweight and flexibility. This article presents an improved numerical model for locomotive tensegrities. The previously used bar element for struts is replaced by beam element, and rigid joint element is used to consider more details of the tendon–strut connections. The vector form intrinsic finite element (VFIFE) method is adopted to formulate the numerical model and carry out the simulation. The improvement of the proposed model on the prediction of feasible rolling gaits is quantitatively verified by experiments on a six-strut locomotive tensegrity. Mann–Whitney U test is adopted, and the p value between the experimental success rates of the gait primitives generated by the improved model and the rates of the gait primitives generated by the previous model is [Formula: see text]. It is shown that the improved model is more consistent with the experiment by considering the details of the tendon–strut connection.

An improved DEM-based mesoscale modeling of bimrocks with high-volume fraction

Block-in-matrix rocks (bimrocks), a typical heterogeneous and discrete geomaterial, are widely found in nature and may cause problems in the design and construction of projects. The generation of mesoscale bimrocks with a high volumetric block proportion (VBP) is still a challenge. This paper proposes a novel mesoscale method that can generate bimrocks models with high VBPs and can generate high-quality mesh using the finite element method (FEM). The Rigid Block discrete element method was then applied to simulate uniaxial compression tests based on the FEM mesh. The agreement between the numerical and experimental results demonstrates that the method is reasonable and effective. In addition, the effect of VBP, strength of the block-matrix interface, and friction coefficient of rock blocks on the uniaxial compressive strength of bimrocks was also investigated.

In situ construction of PVA/LiF composite artificial protective layer to assist dendrite-free Li metal anode

Lithium (Li), with superior specific capacity and lowest standards electrode potential, has been touted as the “Holy Grail” among various anode materials. However, in the process of repeated lithium plating/stripping, the uncontrollable lithium dendrite growth and unstable interface inevitably affect the application of lithium metal batteries. Here, an ingeniously designed artificial protective layer consisting of polyvinyl alcohol polymer and lithium fluoride was coated on a Cu current collector to overcome the obstacles above. High Young’s modulus and favourable ionic conductivity are ensured through the synergistic interaction between soft and rigid structural elements evenly distributed in the layer. Dense Li deposition with no dendrite, conspicuously reduced interfacial resistance, and dramatically prolonged cycle life were achieved, ascribing to the interface stabilization by the artificial protective layer. This work shed light on the artificial protective layer design strategy and the energetic chemistry and mechanics of anodes in working batteries.

Adjacent interacting masonry structures: shake table test blind prediction discrete element method simulation

This study presents the numerical simulation of a shake table experimental earthquake campaign of a building aggregate composed of two adjacent unreinforced rubble stone masonry buildings. The experimental testing was performed with the purpose of studying the interaction between a single-storey and a two-storey building connected with a dry joint consisting of a smooth mortared surface. Before performing the experimental testing, various research teams were sent the construction details to participate in a blind prediction competition using different prediction strategies. The approach reported herein to simulate the shake table tests is the discrete element method (DEM) with rigid elements and damage and deformation lumped in inter-block joints that represent the mortar interfaces governed by a non-linear Mohr–Coulomb constitutive laws. The material properties implemented in the model after calibrating using piers shear tests was observed unrealistically stiff. Hence, it was reduced based on the outcome of pushover and eigenvalue analyses. A sequence of earthquakes with incremental acceleration was input to the real and numerical models. Numerical overestimation of damage and displacement was observed probably due to underestimating the damping ratio. Unexpected sliding of the single-storey building occurred at early stages of the simulation. However, the overall behaviour in terms of base shear force, building displacement and damage progression was well captured in the DEM model. The in-plane flexural and rocking mechanism in the two-storey building was correctly simulated. Damage at the interface between the two buildings with separation and pounding was also reasonably well predicted.