Kinds Of Structural Models Research Articles

Comparison of wind turbine blade structural models of different levels of complexity against experimental data

As the design process of a wind turbine blade is highly iterative, one needs to perform the same calculations several times. During that process, the kind of structural model that should be used must be chosen carefully, trying to obtain a good compromise between precision and model setup and computational time. This paper compares four different blade structural models having different levels of complexity. These models are compared to each other and also with experimental results with respect to their abilities to analyze blade cross-sectional properties, natural frequencies, deflection, strains, buckling strength, and composite strength. This comparison shows that even if the 3D shell finite element model is the more precise and is the only one that can manage the regions of the blade where the cross-sectional shape changes quickly, the strength of material based models gives accurate results. Even the simpler model, based on blade shape simplification, gives conservative and accurate results at a very low computational cost.

Shaking table test and numerical simulation of shallow foundation structures in seasonal frozen soil regions

Frozen soil layers can induce the formation of double or multilayers on the ground. Such formations change the dynamic characteristics and dominant period of soil, directly influencing the stability and safety of upper buildings. In this paper, the frozen soil-structure interaction system in cold region was taken as the research object. The frozen soil model was made artificially, and two kinds of structure models with different natural frequencies were designed. Through a series of shaking table tests and finite element numerical analysis, the influence of structural natural frequency, soil frozen depth and seismic load on the seismic response of structure were studied. The test results indicate that ground freezing could weaken the soil–structure interaction effect and the nonlinear development of the soil structure. The effect of peak acceleration amplification of the ground is significant close to the surface. The acceleration amplification coefficient of the ground surface decreased as the freezing depth increased, which indicates that the freezing of the ground suppressed the acceleration response of the ground surface. If the peak frequency of a seismic wave is close to the natural frequency of the structure, it can significantly amplify the seismic response of the structure. Owing to the interaction between the soil and the structure, the degree of liquefaction of the ground varied with different structures. Subsequently, a nonlinear finite element program was used to establish the dynamic calculation model of frozen soil-structure interaction system considering the gradient change of stiffness of frozen soil and the dependence of frozen soil on temperature. On the basis of validating the numerical model rationality, the seismic response of frozen soil-structure interaction system under horizontal seismic excitation was further explored. The analysis results show that the seismic response of the structure increased significantly with amplitude excitation; the greater was the freezing depth, the greater was the seismic response of the structure, The influence of the frozen ground on the seismic response of structures in the design of structures in frozen soil areas should be considered. In summary, the dominant period of the ground, the dynamic characteristics of a structure, the type of seismic wave, and the degree of liquefaction of the ground have a significant influence on the seismic response of the structure. Therefore, considerable attention should be paid to the influence of frozen soil on the dynamic characteristics of a structure in frozen soil regions.

Dynamic response of multi-story buckling-restrained braced steel frames with different β values

The average shear-bearing ratio (β) of buckling restrained brace (BRB) is a key parameter, affecting the seismic performance of buckling restrained braced steel frames (BRBF). In order to determine the dynamic response of multi-story BRBF with different β values, two kinds of structural models are established, one is with the rigid connection of beam-column joints, and the other model has both hinged and rigid joints. The nonlinear time-history analysis of multi-story BRBF structures are carried out by selecting the seismic waves with predominant period close to the first mode period of each research model, and the seismic waves that are significantly different from it. The influence of β on the shear displacement, bending displacement and vibration mode of the structure are revealed: when β ≤ 30%, the story drift of multi-story BRBF structure is mainly shear deformation and the first vibration mode is predominant. When β increases, the bending deformation of the story drift increases. The second vibration mode of the structure is predominant when β ≈ 90%. It is suggested that the equivalent seismic force of multi-story BRBF structure with β > 30% should not be calculated by the base shear force method.

Nanoindentation and Hierarchy Structure of the Bovine Hoof Wall.

The bovine hoof wall with an α-keratin structure protects the bovine foot from impact loads when the cattle are running. Reduced modulus, hardness and creep behavior of the bovine hoof wall have been investigated by a nanoindentation technique. The average reduced modulus of the Transverse Direction (TD) specimens from the outside to inside wall is 3.76 and 2.05 GPa, respectively, while the average reduced modulus of the Longitudinal Direction (LD) specimens from the outside to inside wall is 4.54 and 3.22 GPa, respectively. Obviously, the orientation and the position of the bovine hoof wall have a significant influence on its mechanical properties. The use of the generalized Voigt–Kelvin model can make a good prediction of creep stage. Mechanical properties of the LD specimens are stronger than those of the TD specimens. The bovine hoof wall has a layered structure, which can effectively absorb the energy released by the crack propagation and passivate the crack tip. Therefore, a kind of structural model was designed and fabricated by three-dimensional printing technology, which has a 55% performance improvement on fracture toughness. It is believed that the reported results can be useful in the design of new bionic structure materials which may be used in motorcycle helmets and athletes’ protective equipment to achieve light weight and improved strength at the same time.

A high toughness and light weight armor structure bioinspired design based on a bovine hoof wall

Mechanical properties and microstructure of the bovine hoof wall have been studied. The reduced modulus and hardness of the transverse and the longitudinal specimens decrease from the outside to the inside, and reach a peak of 4.69 GPa and 0.15 GPa, respectively. The further work reveals that the enhancement mechanism is the lamellar structure and fiber-refined mode. In addition, a kind of structural model is designed and fabricated by three-dimensional printing technology, whose performance is improved by 55%. We hope this work can provide ideas for a new high-toughness and light-weight armor design.

Roof Strata Behavior and Support Resistance Determination for Ultra-Thick Longwall Top Coal Caving Panel: A Case Study of the Tashan Coal Mine

The Longwall Top Coal Caving (LTCC) method has greatly improved the production of ultra-thick underground coal resources. However, face fall and support closure have been becoming highly frequent accidents at the working face, and seriously threaten the safety of miners. The key to avoiding these problems is to reveal the structural evolution of the roof strata and then choose a reasonable working resistance for the hydraulic supports. According to physical modeling, theoretical analysis and field observation of the LTCC panel, four kinds of structural models can be found and defined, in consideration of the coincident movement of key strata (KS) and the mining activities of upper face in overburden strata. The KS are performed as cantilever structures, hinged structures and voussoir beam structures at three different positions in roof strata. The structural characteristics of the KS and its movement laws are shown in the four structural modes. The loads acting on the support in the four typical structural models are also analyzed. The structural instability of the broken roof strata on the upper caving panel caused by the lower ultra-thick coal seam mining is considered to be the main reason for its face’s falls and support failures. Consequently, a method is proposed for calculating the working resistance of the support in the LTCC face, which is verified by the mining pressure monitoring in practice.

A Radical Economic Model of Crime with an Empirical Test in Non-city Zip Codes

This article addresses three main issues. First, the structural explanation of crime rates across zip codes within a US county outside of that county’s major city’s limits. Second, this article addresses whether the traditional social disorganization argument which links measures of disorganized neighborhoods and in particularly deficiencies in informal social control to race, income inequality and poverty provides an adequate explanation of variations in non-city zip code crime rates. Third, this article also examines a radical critique of the kind of structural model posed by social disorganization, and tests an alternative radical economic model of crime at the zip code level. The empirical evidence illustrates the weakness of social disorganization explanations of crime at the zip code level. In contrast to those results, the empirical results for the proposed radical economic model of crime support its use for explaining crime across county zip codes. This type of empirical evidence demonstrates that radical models of crime have utility in explaining how economic structures influence the distribution of crime independently of variable identified in orthodox criminology.

Study on the Static Performance of Steel Truss Structure

This paper aims to experimentally study static responses of bridge longitudinal truss, and the distribution rules of the structural and local stresses were analyzed. The results of the analyses on experimental data show that the typical details in the longitudinal truss concentrate to a limited area on the toe of a dominate weld at the intersection among the upper chord or bottom chord, diagonal and the gusset plates; with boundary conditions being strengthened, stress distribution of the tested specimen became flat and the monolithic tress level decreased relatively. Based on obtained test information, the results are used for updating and validating this kind of structural model, and determining the parameters of finite element model.

Shaking Table Test of RC Frame-Shear Wall Structures with Partial Columns Sliding at Upper Ends

A new kind of RC frame-shear wall structures with partial columns sliding at upper ends is proposed in this paper. A shaking table test of this new kind of structure model (Model B) and a conventional frame shear-wall structure Model (Model A) were carried out, and the plan layout and the member size of the two models are nearly identical. The two models are 3-story and 2-bay by 2-bay, and the second story of either structure is weak story. The test results showed that: (1) under the same intense earthquake, the damage of Model B is slighter than that of Model A; and (2) under the same intense earthquake, the interstory drift angle, the acceleration and the shear force of weak story of Model B are reduced remarkably in comparison to Model A.

Exact stochastic solution of beams subjected to delta-correlated loads

The bending problem of Euler-Bernoulli discontinuous beams is dealt with, in which the discontinuities are due to the loads and eventually to essential constrains applied along the beam axis. In particular, the loads are modelled as random delta-correlated processes acting along the beam axis, while the ulterior eventual discontinuities are produced by the presence of external rollers applied along the beam axis. This kind of structural model can be considered in the static study of bridge beams. In the present work the exact expression of the response quantities are given in terms of means and variances, thanks to the use of the stochastic analysis rules and to the use of the generalized functions. The knowledge of the means and the variances of the internal forces implies the possibility of applying the reliability B-method for verifying the beam.

Structural characteristics of key strata and strata behaviour of a fully mechanized longwall face with 7.0 m height chocks

Strata behaviour during the operation of super great mining height (SGMH) longwall face is different from that of normal mining height due to the extra large boundary of caved roof strata. The key to control the strata behaviour is to understand the structural characteristics of key strata (KS) and its movement law. Through field observation, physical model simulation and theoretical analysis on the first longwall face with 7.0m mining height in the world, three kinds of structural model, which are affected by the relative position of KS in the overburden, are found and defined. Model A is defined as when the stable voussoir beam structure can be developed in the overlying KS and the strata behaviour is gentle. Model B is defined as when the cantilever structure is developed in the first KS while voussoir beam structure is developed in other overlying KS, and the continuous distance of periodic weighting (CDPW) is typically longer compared with that of normal mining height face. As to Model C, the structure of KS is the same as that in Model B, but the first KS will be forced to break in advance due to the break of the second adjacent overlying KS, which will present the weighting step and strata behaviour severity with a periodic alternating between long/gentle and short/strong. With respect to the three kinds of structural models, a method which is suitable for the calculation of working resistance for 7.0m height chocks was proposed. The suitable working resistance for the 7.0m height chocks of LW22303 face in Bulianta coal mine was determined to be 17,612kN.

구조의 절점 형식에 따른 형상 형성의 거동 특성

This paper concerned with the behaviour of shaping formation and the erection for SCST structure by cable-tensioning for three kinds of structure models. The joint types of experimental models are ball type joints, bolt type joints with gusset plates, and bolt type joints. The feasibility of the proposed shaping method and the reliability of the established geometric model were confirmed with a nonlinear finite element analysis and an experimental investigation for full size scaled pyramid test model and three kinds of SCST structure models. The characteristic of the behaviour of each joint type is shown in the shaping test for practical design purposes. As a results, the behaviour characteristics of joints is very significant in shaping analysis of space structures. So the joint type should be considered in the design and analysis of the shape formation for space structures. Also, in the special field condition, it could be a fast and economical method for constructing the space structure.

System approach to modeling of liver glucose metabolism with physiologically interpreted model parameters outgoing from [18F]FDG concentrations measured by PET

New mathematical models from physiologically interpreted parameters capable of evaluating glucose metabolism within the liver and/or the whole body were developed.The group of pigs in a fasting state and the group of pigs with euglycemic supraphysiological hyperinsulinemia were scanned by positron emission tomography after a single dose of [18F]FDG tracer. Simultaneously frequent sampling of the dynamic data of [18F]FDG plasma concentration in artery, portal vein and hepatic vein was obtained. A system approach to the liver and/or the whole-body system by the tools of linear dynamic sysztem theory was used.Three kinds of structural models, single input and single output or multiple outputs and multiple inputs and single output, were identified. Differences between the group of fasting pigs and the group of pigs in euglycemic supraphysiological hyperinsulinemia were identified by estimated parameters of the structural models.The suitability of the structural mathematical models for the estimation of physiologically interpreted parameters from PET was validated.

A Study on 3D Isolation Effect on High-Rise Building Subjected to Near-Field Ground Motions

Isolation technology is widely applied in civil engineering nowadays, while it is indicated by seismic damage investigations that the effect of vertical motion on buildings under earthquake couldn’t be ignored. In order to study the 3D isolation effect on high-rise buildings subjected to near-field ground motions, the finite element analysis of an 11-story reinforced concrete frame-shear wall building is conducted, three ground motions are selected, three kinds of structural model are calculated, which are without isolation, with horizontal isolation and with three-dimensional isolation. By analyzing and comparing the seismic response results of models, the 3D isolation effect is studied, and some conclusions are obtained.

Establishment of Gun Blast Wave Model and StructuralAnalysis for Blast Load

The muzzle of a gun mounted on an airplane emits repetitive gun blast waves during the firing. These blast waves expand in open space and they are reflected on the airplane surface adjacent to the gun. The vibration resulting from the reflected waves can cause adverse effects to the airplane. Therefore, it is very important to establish an accurate blast wave model for the prediction of the vibration level. In the present study, the blast wave model is established using a scaling approach and CFD calculation, and this model is then verified with experimental data. The established blast wave model is applied to two kinds of structural models. Firstly, to investigate the effect of the muzzle distance from the surface, the responses of a graphite epoxy composite panel exposed to the blast wave are analyzed for various muzzle distances. Secondly, the transient response analyses of a left wing model are carried out for several repeated fires. From the results, it can be shown that the assumption of uniform blast wave is not applicable in the near muzzle distance, and the vibration resulting from the repetitive blast waves can cause high frequency damage to the structure and equipments mounted in the aircraft. The blast wave model can be applicable not only to the prediction of the vibration but also to a blast resistant structural design.

RHEED Rocking Curve Analysis of Si(111).RAD.3*.RAD.3-Ag Surface Phase Transition at Low Temperature

Si(111)√3×√3-Ag surface structural phase transition from honeycomb chained triangles (HCT) structure to inequivalent triangles (IET) structure is investigated using reflection high-energy electron diffraction (RHEED) rocking curves. Rocking curves are measured during spontaneous heating process of a cooled (∼120K) sample up to room temperature. The rocking curves were analyzed using many-beam dynamical RHEED calculations with three kinds of structural models, HCT (Ag triangle stays at mirror symmetry position), IET (Ag triangle rotates by 6 degrees) and rotating-HCT (r-HCT; Ag atoms are randomly rotating between ±6° which maintains the mirror symmetry) structures. At room and low temperatures, r-HCT and IET structures give the best results respectively. Rocking curves between room and low temperatures are also reproduced by mixing of r-HCT and IET structures and the mixing ratio changes almost linearly with substrate temperature. It is obtained that r-HCT coverage is almost 100 % at room temperature and IET coverage is about 60 % at 120 K. It is also found that mixing ratio of IET/r-HCT structure meets 0.5 at about 150 K which is known as a transition temperature in previous reports. [DOI: 10.1380/ejssnt.2006.414]

기총 폭발 하중에 대한 모델 수립과 구조 해석에 관한 연구

총구로부터 방출되는 폭발파에 대한 수학적 모델(GUNBLAST)을 수립하였으며, 폭발 하중에 대한 구조 응답 해석을 수행하였다. 폭발파는 자유영역 폭발파와 반사 폭발파로 구분되어질 수 있다. 본 연구에서는 스케일 기법을 이용하여 자유영역 폭발파 모델을 수립하였으며, 경사 충격파 이론과 전산유체역학(Computational Fluid Dynamics) 계산을 통하여 반사 충격파를 계산하였다. GUNBLAST는 두 가지의 구조 모델에 적용되었으며 구조 표면으로부터의 총구거리 변화에 따른 폭발파 특성을 파악하기 위하여 평판에 대한 적용을 통하여 균일하중조건과의 비교를 수행하였다. 또한 MSC/NASTRAN을 이용하여 12.7mm 기총을 장착한 비행기 날개 모델의 과도 응답 해석을 수행하였다. 결과적으로 이러한 폭발파는 랜덤진동과 항공기에 탑재된 장비에 고주파의 손상을 일으킬 수 있음을 확인하였다. A mathematical model, GUNBLAST, of blast waves emitted from a gun muzzle is established, and structural response analyses for the blast load are performed. The blast wave can be divided into two kinds of waves, free field and reflected blast waves. In this research, the free field blast wave model is established by the use of a scaling approach, and the reflected blast wave is calculated by using the oblique shock theory and computational fluid dynamic calculation. GUNBLAST is applied to two kinds of structural models. To investigate the effect of the muzzle distance from a structural surface, the blast waves on a plate for various muzzle distances are compared to uniform loads. Moreover, the transient response analysis of an aircraft wing model with a 12.7mm gun is carried out by using MSC/NASTRAN. From the results, it can be shown that the blast wave can cause broad random vibration and high frequency damage to equipments mounted in the aircraft.

An experimental study on variation of b value during deformation of rock samples with different structural models

A preliminary study of b value of rocks with two kinds of structural models has been made on the base of a new acoustic emission recording system. It shows that b value of the sample decreases obviously when the sample with compressive en echelon faults changes into a tensile one after interchange occurs between stress axis σ1 and σ2. A similar experiment is observed when the sample with tensile en echelon faults changes into that with a bend fault after two segments of the en echelon fault linking up. These facts indicate that the variation of b value may contain the information of the regional dominant structural model. Therefore, b-value analyses could be a new method for studying regional dominant structural models.

TED Study of Si(113) Surfaces

A TED study of Si(113) surfaces was carried out. Reflections from the 3 × 2 reconstruction were seen at room temperature, while half-order reflections were very faint. The surface showed the phase transition between the 3 × 1 and the disordered (rough) structures at about 930°C. The (113) surface structure at room temperature was analyzed using TED intensity. Four kinds of structure models proposed previously, including both the 3 × 1 and the 3 × 2 reconstructed structures, were examined. The R-factors calculated using the energy-optimized atomic coordinates are not sufficiently small. After minimization of the R-factors, Dabrowski's 3 × 2 structure model is most agreeable, while Ranke's 3 × 1 and 3 × 2 structure models are not to be excluded. STM observation showed that the surface is composed of small domains of the 3 × 2 structure.

粉砕を伴う連続式回転円錐型容器による複合微細造粒粒子の生成とその特性

In order to produce small composite granules having binary components of CaCO3 and SiC powders, experiments were carried out by the simultaneous operation of granulation, grinding and separation in a single continuous rotating conical vessel with a grinding media. To characterize these composite granules, SiC agglomerates included in a granule were separated by chemical methods, and the size distributions of granules and these SiC agglomerates were measured by an image analyzer through a microscope.The structure in a composite granule was characterized by comparing the size of a composite granule with that of SiC agglomerates in the granule.As a result, it was found that composite structures in each granule could be classified broadly into six kinds of structure models, and that the composite structure depended on the size of the granules and the volume fraction of the SiC component in the granule.