A Simplified Method for the Stress Analysis of Underground Transfer Structures Crossing Multiple Subway Tunnels

According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.

Generalized response displacement methods for seismic analysis of underground structures with complex cross section

The response displacement method(RDM)is recommended for the seismic analysis of underground structures in the transverse direction for many codes,including bases for design of structures-seismic actions for designing geotechnical works(ISO 23469)and code for seismic design of urban rail transit structures(GB 50909-2014).However,there are some obvious limitations in the application of RDM.Springs and the shear stress of the soil could be approximately evaluated for the structures having a simple cross section,such as rectangular and circular structures.It is necessary to propose simplified seismic analysis methods for structures with complex cross sections.This paper refers to the idea of RDM and proposes three generalized response displacement methods(GRDM).In GRDM1,a part of the soil surrounding a structure is selected to generate a generalized underground structure with a rectangular cross section,and the same analysis model as RDM is applied to analyze the responses of the structure.In GRDM2,a hollow soil model without a generalized structure is used to compute the equivalent load caused by the relative displacement of the soil,and the soil-structure interaction model is applied to calculate the responses of the structure.In GRDM3,a continuous soil model is applied to compute the equivalent load caused by the relative displacement and shear stress of the soil,and the soil-structure interaction model is applied to analyze the responses of the structure,which is the same as the model used in GRDM2.The time-history analysis method(THAM)is used to evaluate the accuracy of the proposed simplified methods.Results show that the error of GRDM1 is about 20%,while the error is only 5%for GRDM2 and GRDM3.Among the three proposed methods,GRDM3 has obvious advantages regarding calculation efficiency and accuracy.Therefore,it is recommended to use GRDM3 for the seismic response analysis of underground structures that have conventional simple or complex cross sections.

Cross-cultural Comparison of Cognitive Structure and Behavior of Waterfront Landscape between Subjects of China,Japan and Britain

In order to explore the cultural value of waterfront in urban landscape,from the perspective of cross-cultural comparison psychology,the subjects from Britain,Japan and China have been surveyed to obtain their cognitive structure and behavior on waterfront landscape.Based on the comparison of quantitative statistic results of life value,cognitive structure of waterfront space,and water-loving,a quantitative analysis has been conducted on the relevance between each factor by using Quantification Theory III.Then,it has analyzed the types and purpose of behavior in waterfront space,and the influence brought by cultural value difference.

Frequency Domain Fatigue Evaluation on SCR Girth-Weld Based on Structural Stress

The Steel Catenary Riser(SCR)is a vital component for transporting oil and gas from the seabed to the floating platform.The harsh environmental conditions and complex platform motion make the SCR’s girth-weld prone to fatigue failure.The structural stress fatigue theory and Master S-N curve method provide accurate predictions for the fatigue damage on the welded joints,which demonstrate significant potential and compatibility in multi-axial and random fatigue evaluation.Here,we propose a new frequency fatigue model subjected to welded joints of SCR under multiaxial stress,which fully integrates the mesh-insensitive structural stress and frequency domain random process and transforms the conventional welding fatigue technique of SCR into a spectrum analysis technique utilizing structural stress.Besides,a full-scale FE model of SCR with welds is established to obtain the modal structural stress of the girth weld and the frequency response function(FRF)of modal coordinate,and a biaxial fatigue evaluation about the girth weld of the SCR can be achieved by taking the effects of multi-load correlation and pipe-soil interaction into account.The research results indicate that the frequency-domain fatigue results are aligned with the time-domain results,meeting the fatigue evaluation requirements of the SCR.

Nonplanar flow-induced vibrations of a cantilevered PIP structure system concurrently subjected to internal and cross flows

Pipe-in-pipe(PIP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PIP structure system usually consists of two concentric pipes and one softer layer for thermal insulation consideration.The total response of the system is related to the dynamics of both pipes and the interactions between these two concentric pipes.In the current work,a theoretical model for flow-induced vibrations of a PIP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross flow.The interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe length.The unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake oscillators.The nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential equations.These ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration algorithm.Phase portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight trajectory.The PIP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.

Composite wave-absorbing structure combining thin plasma and metasurface

In order to solve the thickness dependence of plasma absorption of electromagnetic waves and further reduce the backward radar scattering cross section(RCS)of the target,we designed a novel composite structure of a metasurface and plasma.A metasurface with three absorption peaks is designed by means of an equivalent circuit based on an electromagnetic resonance type metamaterial absorber.The reflection and absorption of the composite structure are numerically and experimentally verified.The finite integration method was used to simulate a composite structure of finite size to obtain the RCS.The experimental measurements of electromagnetic wave reflection were conducted by a vector network analyzer(Keysight N5234A)and horn antennas,etc.The research showed that the absorption capacity of this composite structure was substantially improved compared to either the plasma or the metasurface,and it is more convenient for application due to its low plasma thickness requirement and easy fabrication.

Application of CFD and FEA Coupling to Predict Structural Dynamic Responses of A Trimaran in Uni-and Bi-Directional Waves

To predict the wave loads of a flexible trimaran in different wave fields,a one-way interaction numerical simulation method is proposed by integrating the fluid solver(Star-CCM+)and structural solver(Abaqus).Differing from the existing coupled CFD-FEA method for monohull ships in head waves,the presented method equates the mass and stiffness of the whole ship to the hull shell so that any transverse and longitudinal section stress of the hull in oblique waves can be obtained.Firstly,verification study and sensitivity analysis are carried out by comparing the trimaran motions using different mesh sizes and time step schemes.Discussion on the wave elevation of uni-and bi-directional waves is also carried out.Then a comprehensive analysis on the structural responses of the trimaran in different uni-directional regular wave and bi-directional cross sea conditions is carried out,respectively.Finally,the differences in structural response characteristics of trimaran in different wave fields are studied.The results show that the present method can reduce the computational burden of the two-way fluid-structure interaction simulations.

Study on the Structure of Peroxide Cross-Linked Polyethylene Pipes with Several Stabilizers

Cross-linked polyethylene (PEX) pipes used in hot water supply are required for high mechanical strength and high creep resistance at high temperature. Especially PEX-a pipes which are made by peroxide cross-linking have better performance, such as creep resistance and thermal shock resistance than the pipes made by the other cross-linking method. Because the PEX-a pipes indicate the higher cross-link degree as compared with the other PEX pipes. In this study, the PEX-a pipes which were mixed with several stabilizers were tested to evaluate the effects on cross-link degree and the oxygen induction time. And also they are evaluated with the chlorine aqueous solution by the performance of the long-term hydrostatic pressure test and the long-term hydro dynamic pressure test. As a result, it was found that the combination of antioxidants for PEX-a pipes plays an important role to prolong the oxygen induction time without inhibiting the cross-linking. From the results of the 1H pulsed NMR measurement over the melting point of polyethylene, it was found that each peroxide PEX pipe with different antioxidant combinations indicated the different proportion and crosslink density of cross-linked region, in addition, that these pipes had the effective structure of cross-linking for the hydrostatic and hydrodynamic pressure test with the chlorine aqueous solution. Therefore, it was considered to be useful results for studies of the stricture of cross-linking of polyethylene.

Vertical Structure of Interannual Variability in Cross-Equatorial Flows over the Maritime Continent and Indian Ocean in Boreal Summer

This study investigates the vertical structure of variability in the cross-equatorial flows(CEFs)over the Maritime Continent and Indian Ocean in boreal summer,based on three reanalysis datasets:ERA-Interim,JRA-55 and NCEP-2.The results show a high consistency in the interannual variability among the reanalysis datasets,especially between ERAInterim and JRA-55,while great uncertainty exists in the decadal or long-term changes of CEFs.Further analyses on the interannual variability in CEFs indicate that there is a significant negative relationship between the upper-and lower-level CEFs over the Maritime Continent—that is,the northerlies at the upper level and southerlies at the lower level are both enhanced or weakened.This seesaw pattern is also significantly related to the CEFs over the Indian Ocean at the upper level and lower level(i.e.,the Somali jet).This close relationship between the upper-and lower-level CEFs and between the Maritime Continent and Indian Ocean is manifested as the leading mode of equatorial meridional winds in the vertical-zonal section over the Maritime Continent and Indian Ocean.Finally,it is found that ENSO is closely related to the vertical leading mode,and to all the CEFs at the upper and lower levels over the Maritime Continent and Indian Ocean.

Extraction of Structure Function and Gluon Distribution Function at Low-x from Cross Section Derivative by Regge Behavior

An approximation method based on Regge behavior is presented. This new methodrelates the reduced cross section derivative and the structure function Regge behavior at low x.With the use of this approximation method, the C and λ parameters are calcuiated from the HERAreduced cross section data taken at low-x. Also, we calculate the structure functions F_2(x, Q~2)even for low-x values, which have not been investigated. To test the validity of calculatedstructure functions, we find the gluon distribution function in the Leading order approximationbased on Regge behaviour of structure function and compare to the NLO QCD fit to H1 data and NLOparton distribution function.

Lepton Scattering Cross Section and Nuclear Structure Function of ⁴He and ¹²C Nuclei

This paper is an effort to extract the structure function, the EMC ratio, and the lepton scattering cross section in the convolution nuclear theory framework for 4He and 12C nuclei. We suppose that, in conventional approach, based on harmonic oscillator model, one could consider for a nucleus shell different hw?parameters which are associated with the square root of the mean radius of the nucleus shells. We use GRV free nucleon structure function, which has good agreement with the proton and neutron structure function, extracted from experimental results. In addition, the lepton scattering cross sections of 4He and 12C nuclei are calculated in energy higher than 1 GeV. The extracted results show good agreement with experimental data.

Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures. The results demonstrated that the Raman scattering cross section （RSCS） of short-chain polymer all-trans-β-carotene is extremely high in liquid. Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions. Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure. All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties, which lead to large RSCS in the solvent with large density and low concentration at low temperature.

Inclined-cross Microstructure of Conch Shell

The microstructures of conch shell were observed with scanning electronic microscope （SEM）, and a kind of inclined-cross microstructure of aragonite sheets was found. The maximal pull-out force of the inclined-cross microstructure was analyzed based on its representative model and compared with that of a conventional 0 °- structure. The experimental result indicates that the maximal pull-out force of the inclined-cross microstructure is markedly larger than that of the 0°- structure.

The Influence of Thrust Fault Structure on Cross-fault Short-leveling Survey

Aiming at different variation patterns of cross-fault short-leveling before earthquakes,the paper establishes the 2-D finite-element models with different crustal stratification and fault occurrence perpendicular to Longmenshan fault zone. By contact analysis and viscoelastic finite element method,the influence of fault structure on cross-fault short-leveling is obtained under the same constraint conditions,the results show that:with the increase of the horizontal projection distance of fault,the cumulative displacements of surface increase gradually in the models with fixed dip angles of the fault plane(model 1). However,when the horizontal projection distance exceeds 20 km,the influence of fault?s dip angle on the cumulative displacements of surface short-leveling will decrease significantly,and the cumulative displacements are maintained at about 1. 5 m. However,in the listric fault models(model 2),when the projection distance is less than 20 km,the listric fault structure impedes the sliding of fault. The short-leveling variation rate is only half of model 1;as a result,the ability to reflect the regional stress enhancement by cross-fault short-leveling is further weakened. But when the horizontal projection distance exceeds25 km,the cumulative displacements significantly increase,with the maximum displacement reaching 1. 75 m. The results of equivalent stress show that the listric fault structure causes a sudden increasement in equivalent stress when the horizontal projection distance is 10 km,higher equivalent stress values are accumulated between the projection distance of 5-20 km,and then high-low stress difference zones are formed at the bottom of the fault plane and near the transition zone of low-high dip angle.

3D Woven Structures and Their Weave Design with Changing Cross-section on Warp and Weft Direction

With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.

Vegetation Formation in Estuarine Tidal Flats: Influences of Basin Scale and River-Crossing Structures of the Eight Rivers of Ise Bay in Mie and Aichi Prefectures, Japan

In this study, we examined the influences of the differences in basin scale and river-crossing structures of 8 rivers of Ise Bay in Mie and Aichi Prefectures, Japan on the vegetation in the estuarine tidal flats of these rivers. The dominant plant communities of the estuarine tidal flats formed from rivers of large-scale river basins (exceeding 300 km2) were determined. In the Miya River, the dominant plant community was the Suaeda maritima and Artemisia fukudo community. In the Kushida River, the dominant plant community was composed of Phacelurus latifolius, Artemisia fukudo, Phragmites australis, and bamboo. In the Kumozu River, the dominant community was composed of the coastal plants Calystegia soldanella, Lathyrus japonicus, and Carex pumila and the exotic plant of Lolium multiflorum. The plant community of Suzuka River was dominated by the exotic plant of Eragrostis curvula. Among the estuarine tidal flats influenced by a small-scale river basin (50 km2 or less), the plant community of Shinbori River (Fukue tidal flat) was dominated by Suaeda maritima, and the plant communities of the Shio and Harai Rivers were dominated by Phragmites australis. The plant community of Tanaka River was dominated by Phragmites australis and coastal plants. Regarding the relationship between the vegetation and the river environment for each study site, we hypothesised that in a large basin area with few structures crossing the river, the river water catchment in the estuary after heavy rains caused large areas of disturbance and formed bare land, providing suitable habitat for an annual salt marsh plant community. In contrast, in cases with many structures crossing the river, a stable channel, an excavated riverbed and the suppression of runoff and the resulting disturbance of the estuary, flooding did not occur during high tide. Moreover, we hypothesised that in a small basin with many structures crossing the river, disturbance to the estuary was not likely, and the perennial salt marsh plant community of Phragmites australis would be widely distributed, except for a river type such as the Shinbori River, in which tide and river flow were managed by a final closure.

交叉型消像散Czerny-Turner结构光谱仪设计

以相对孔径为1∶8,工作波段为780～1 014 nm为初始光学参数,首次推导出交叉型Czerny-Turner(C-T)结构光谱仪的一阶消像散条件,搭建了交叉型消像散C-T结构和交叉型消彗差C-T结构。利用ZEMAX软件对两种初始结构进行了优化和比较。结果表明:交叉型消像散C-T结构具有更优越的光学性能,其均方根半径仅是消彗差C-T结构的12%～52%。消像散C-T结构不仅在沿狭缝方向上能量更为集中,利于设计大聚光能力的分光系统,而且在沿垂直于狭缝方向上点斑更小,具有更高的光谱分辨率。

基于交叉式Czerny-Turner结构的光纤光栅解调光路设计及像差校正

为满足光纤光栅传感系统的解调仪器高分辨力、微型化的需求,针对光纤光栅传感1 550 nm波段设计了光谱成像法光纤光栅解调系统的分光光路系统.成像系统形式采用交叉式Czerny-Turner结构,分析了使用超环面镜代替球面镜、在结构中加入额外的柱面透镜或柱面反射镜以及使衍射光栅工作在发散光条件下的3种校正像散方法的特点,最终选用使衍射光栅工作在发散光条件下的校正像散方法,实现在不加入附加光学元件条件下的像散校正,同时采用小角度入射的方法减小系统彗差.通过Zemax对成像系统进行了参数优化与光线追迹分析,优化结果证明了上述像差校正方法适用于光纤光栅解调.在解调光谱范围内,可明显分开波长间隔为1 nm的光斑,满足光纤光栅解调的分辨力需求.

Principal axes of M-DOF structures Part I:Static loading

This paper is the first in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and control modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended control devices/systems, and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects - of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading. This first paper deals with quantitative definitions of principal axes and “cross effects” of three-dimensional structures under static load by using linear algebra. It shows theoretically that, for three-dimensional structures, such principal axes rarely exist. Under static loading conditions, the cross effect is typically small and negligible from the viewpoint of engineering applications. However, it provides the theoretical base for subsequent quantification of the response couplings under dynamic loads, which is reported in part II of this series.

Inverse Load Identification in Stiffened Plate Structure Based on in situ Strain Measurement

For practical engineering structures,it is usually difficult to measure external load distribution in a direct manner,which makes inverse load identification important.Specifically,load identification is a typical inverse problem,for which the models(e.g.,response matrix)are often ill-posed,resulting in degraded accuracy and impaired noise immunity of load identification.This study aims at identifying external loads in a stiffened plate structure,through comparing the effectiveness of different methods for parameter selection in regulation problems,including the Generalized Cross Validation(GCV)method,the Ordinary Cross Validation method and the truncated singular value decomposition method.With demonstrated high accuracy,the GCV method is used to identify concentrated loads in three different directions(e.g.,vertical,lateral and longitudinal)exerted on a stiffened plate.The results show that the GCV method is able to effectively identify multi-source static loads,with relative errors less than 5%.Moreover,under the situation of swept frequency excitation,when the excitation frequency is near the natural frequency of the structure,the GCV method can achieve much higher accuracy compared with direct inversion.At other excitation frequencies,the average recognition error of the GCV method load identification less than 10%.