受静冰压力的水工闸门构造静力模拟

应用Solid works和ANSYS workbench工程模拟软件,分别采用模拟计算及试验分析的方式,对受静冰压力影响的松原哈达山水利枢纽泄洪表孔弧形闸门构造静力学进行分析,并比较了该水工建筑物在静冰压力下静力学承力及工学状态,分析过程及结论均可作为寒区水工建筑物防冻害设计及稳定运行的依据。

湿润大气中锋生的非流体静力模拟

1.引言在过去二十年间,大量观测已揭示出伴随锋面系统的带状降水结构.这些研究强调指出,千差万别的天气现象是发生在锋面系统内包含的不同时空尺度上.因此对降水带的理解和预报,是一项困难的工作.半地转理论(Hoskins和Bretherton,1972)是当今全面阐述锋生过程的最合适的基本构想.为改进对锋面的描述,通过显式模拟对流和大尺度气流,用非流体静力云模式(Redelsperger和Sommeria,1986)对由切变引起的锋生,进行二维高分辨率(5km)模拟.

玻璃纤维复材约束纤维复材筋混凝土墩柱的拟静力数值模拟及恢复力模型

为研究由玻璃纤维增强复合材料(GFRP)布、碳纤维增强复合材料(CFRP)箍筋、GFRP纵筋与混凝土组成的新型组合墩柱,纤维增强复材(FRP)约束FRP筋增强混凝土(FCFRC)墩柱的抗震性能,基于OpenSees有限元软件开发FCFRC墩柱单调及往复水平荷载作用下的数值模拟模型,在此基础上以轴压比、剪跨比、纵筋配筋率、CFRP箍筋和GFRP布约束水平、混凝土强度和截面尺寸为变量进行5 184个FCFRC墩柱的单调静力弹塑性分析(Pushover分析),获得上述影响变量对屈服承载力、峰值承载力、弹性刚度、弹塑性刚度以及极限位移角等建立三折线恢复力模型的关键参数的影响规律;结果表明:提高轴压比、纵筋配筋率、混凝土强度和截面尺寸均能提高屈服承载力和极限承载力,箍筋和FRP布约束水平的影响相对较小。基于参数分析结果,获得了恢复力模型骨架曲线关键参数的计算式;此外还提出了FCFRC水平力-位移加卸载滞回规则,结合骨架曲线和滞回规则提出了FCFRC水平力-位移恢复力模型,通过与试验结果比较验证了恢复力模型的适用性。

双层钢桁架梁桥静力模型试验研究

随着我国经济的发展,大跨度钢桁梁桥在我国铁路中得到广泛应用,我国很多学者对其进行了大量的研究并取得了一定的成果。普通的连续钢桁架桥静力分析经过多年的理论分析以及实际经验的研究,相关问题已然基本解决,但是对于公铁两用连续钢桁架桥静力分析的相关资料却不多见,特别对于公铁同面的连续钢桁架大桥,其静力特性研究相对较少。基于此,文章通过对模型试验的分析,充分掌握该主桁结构的静动力性能,而后在全面了解变高度双层钢桁结合梁这一创新结构形式的力学机理,为今后同类型的结构设计与施工提供理论依据。

新型十字加劲波纹钢板剪力墙滞回性能探究

已有研究发现:作为抗侧体系,波纹钢板剪力墙在抗侧刚度、承载能力和耗能能力方面均优于平钢板剪力墙。其缺点是由于在加载后期,波纹钢板应力分布不均匀而使其平面外变形较大,导致结构承载力和刚度严重退化。利用有限元软件ABAQUS建立全壳单元模型,提出了新型十字加劲波纹钢板剪力墙结构,并进行拟静力模拟试验。通过对比未加劲波纹钢板剪力墙,十字加劲波纹钢板剪力墙在屈服荷载、峰值荷载和耗能能力方面均得到有效提高;十字加劲肋的存在有效约束了内嵌波纹钢板平面外变形,缓减了后期结构承载力和刚度的严重退化。

拼装接头对预制综合管廊受力性能影响研究

以预制混凝土综合管廊拼装接头为研究背景,使用有限元分析软件ABAQUS对管廊段中的管节进行了单调静力模拟试验,对比含有拼装接头的管节和不含拼装接头的管节的分析结果,结果表明,在相同荷载作用下,有拼装接头时,管节顶板下部的拉应力极值比整体管节顶板下部拉应力极值大,在管节角部的两侧都出现了拉应力,含有拼装接头在角部附近出现的拉应力值比整体管节的该处拉应力值大;在位移方面,两者在顶板中部的位移值无明显区别,含有拼装接头的管节上下部分的侧板出现相对错动的趋势。

Dynamics simulation of tertiary amines adsorbing on kaolinite(001) plane

The collecting power of tertiary amines（DRN,DEN and DPN） on kaolinite follows the order of DENDPNDRN.After reacting with DRN,DEN and DPN,the surface potentials of kaolinite increase remarkably,and the recruitments caused by collectors also follow the order of DENDPNDRN.The results of dynamics simulation show that the geometries of substituent groups bonding to N are deflected and twisted,and some of bond angles are changed when tertiary amines cations adsorb on kaolinite（001） surface.Based on the results of dynamics simulations and quantum chemistry calculations,the electrostatic forces between three tertiary amines cations and 4×4×3（001） plane of kaolinite are 1.38×10？7 N（DRN12H＋）,1.44×10-6 N（DEN12H＋）,1.383×10-6 N（DPN12H＋）,respectively.

中心锥体筒仓锥体预制板吊装施工数值分析

中心锥体筒仓因其良好的工艺性能,现已广泛应用于水泥库等工业领域。文章通过ANSYS有限元软件对中心锥体预制板吊装阶段进行静力模拟,得到吊装各阶段内力云图,从而找到预制板危险截面,为工程结构设计提供理论依据。

FRP拉索静力及蠕变性能的多尺度预测

合理而高效的纤维增强复合材料(FRP)拉索性能预测方法可有效解决拉索足尺试验难度大、耗时长等问题。为此,以剪切滞后模型的理念为基础,提出以浸胶纱为基本单元的FRP浸胶纱-单筋-拉索多尺度短期静力与长期蠕变预测模型。相比将纤维单丝作为基本单元的一般模型,该模型具有较高的计算效率,尤其适用于大尺寸FRP拉索的足尺建模分析。以37根4 mm直径单筋的玄武岩纤维增强复合材料(BFRP)拉索作为算例,详细阐述了该模型的建立方法和求解流程,并对静力和蠕变模拟结果进行了分析。其中,模型着重考虑了浸胶纱单元拉伸强度和树脂单元剪切强度的双参数威布尔随机分布、树脂屈服后的界面残余剪应力、浸胶纱单元蠕变断裂寿命模型和树脂基体的长期松弛效应。结果表明:BFRP单筋和拉索静力极限承载力的预测值与试验结果误差均在4%以内,而采用单元平均强度直接换算得到的结果较单筋和拉索预测值分别偏高18.3%和11.3%。在此基础上,模型进一步揭示了由FRP浸胶纱、单筋到拉索的多尺度强度退化规律和拉索内部的短长期损伤演化机理,可为后续拉索性能优化和设计提供支撑。在高应力水平下,较弱单元的提前破坏将直接导致拉索整体过早的失效,进而显著削减整体蠕变寿命;而在低应力水平下,拉索整体的蠕变断裂寿命趋近于浸胶纱单元自身的蠕变寿命。

Reliability analysis for seismic stability of tunnel faces in soft rock masses based on a 3D stochastic collapse model

A new horn failure mechanism was constructed for tunnel faces in the soft rock mass by means of the logarithmic spiral curve. The seismic action was incorporated into the horn failure mechanism using the pseudo-static method. Considering the randomness of rock mass parameters and loads, a three-dimensional (3D) stochastic collapse model was established. Reliability analysis of seismic stability of tunnel faces was presented via the kinematical approach and the response surface method. The results show that, the reliability of tunnel faces is significantly affected by the supporting pressure, geological strength index, uniaxial compressive strength, rock bulk density and seismic forces. It is worth noting that, if the effect of seismic force was not considered, the stability of tunnel faces would be obviously overestimated. However, the correlation between horizontal and vertical seismic forces can be ignored under the condition of low calculation accuracy.

Numerical simulation of dynamic fracture properties of rocks under different static stress conditions

When underground cavities are subjected to explosive stress waves,a uniquely damaged zone may appear due to the combined effect of dynamic loading and static pre-load stress.In this study,a rate-dependent two-dimensional rock dynamic constitutive model was established to investigate the dynamic fractures of rocks under different static stress conditions.The effects of the loading rate and peak amplitude of the blasting wave under different confining pressures and the vertical compressive coefficient(K_(0))were considered.The numerical simulated results reproduced the initiation and further propagation of primary radial crack fractures,which were in agreement with the experimental results.The dynamic loading rate,peak amplitude,static vertical compressive coefficient(K_(0))and confining pressure affected the evolution of fractures around the borehole.The heterogeneity parameter(m)plays an important role in the evolution of fractures around the borehole.The crack propagation path became more discontinuous and rougher in a smallerheterogeneity parameter case.

A new approach for time effect analysis of settlement for single pile based on virtual soil-pile model

A new approach is proposed to analyze the settlement behavior for single pile embedded in layered soils. Firstly, soil layers surrounding pile shaft are simulated by using distributed Voigt model, and finite soil layers under the pile end are assumed to be virtual soil-pile whose cross-section area is the same as that of the pile shaft. Then, by means of Laplace transform and impedance function transfer method to solve the static equilibrium equation of pile, the analytical solution of the displacement impedance fimction at the pile head is derived. Furthermore, the analytical solution of the settlement at the head of single pile is theoretically derived by virtue of convolution theorem. Based on these solutions, the influences of parameters of soil-pile system on the settlement behavior for single pile are analyzed. Also, comparison of the load-settlement response for two well-instrumented field tests in multilayered soils is given to demonstrate the effectiveness and accuracy of the proposed approach. It can be noted that the presented solution can be used to calculate the settlement of single pile for the preliminary design of pile foundation.

Ab initio Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulation of CO in the Heme Distal Pocket of Myoglobin

Myoglobin has important biological functions in storing and transporting small diatomic molecules in human body. Two possible orientations of carbon monoxide （CO） in the heme distal pocket （named as BI and B2 states） of myoglobin have been experimentally indicated. In this study, ab initio quantum mechanics/molecular mechanics （QM/MM） molecular dynamics simulation of CO in myoglobin was carried out to investigate the two possible B states. Our results demonstrate that the B1 and B2 states correspond to Fe... CO （with carbon atom closer to iron center of heme） and Fe... OC （with oxygen atom closer to Fe）, by comparing with the experimental infrared spectrum. QM electrostatic polarization effect on CO brought from the protein and solvent environment is the main driving force, which anchors CO in two distinctive orientations and hinders its rotation. The calculated vibrational frequency shift between the state B1 and B2 is 13.1 cm-1, which is in good agreement with experimental value of 11.5 cm-1. This study also shows that the electric field produced by the solvent plays an important role in assisting protein functions by exerting directional electric field at the active site of the protein, From residue-based electric field decomposition, several residues were found to have most contributions to the total electric field at the CO center, including a few charged residues and three adjacent uncharged polar residues （namely, HIS64, ILE107, and PHE43）. This study provides new physical insights on rational design of enzyme with higher electric field at the active site.

Energetics and temporal variability of internal tides in Luzon Strait:a nonhydrostatic numerical simulation

A fully nonlinear,three-dimensional nonhydrostatic model driven by four principal tidal constituents(M2,S2,K1,and O1) is used to investigate the spatial-temporal characteristics and energetics of internal tides in Luzon Strait(LS).The model results show that,during spring(neap) tides,about 64(47) GW(1 GW=109 W) of barotropic tidal energy is consumed in LS,of which 59.0%(50.5%) is converted to baroclinic tides.About 22(11) GW of the derived baroclinic energy flux subsequently passes from LS,among which 50.9%(54.3%) flows westward into the South China Sea(SCS) and 45.0%(39.7%) eastward into the Pacific Ocean,and the remaining 16(13) GW is lost locally owing to dissipation and convection.It is revealed that generation areas of internal tides vary with the spring and neap tide,indicating different source areas for internal solitary waves in the northern SCS.The region around the Batan Islands is the most important generation region of internal tides during both spring and neap tides.In addition,the baroclinic tidal energy has pronounced seasonal variability.Both the total energy transferred from barotropic tides to baroclinic tides and the baroclinic energy flux flowing out of LS are the highest in summer and lowest in winter.

Simulation of pressure effects on hot isostatic pressing of stainless steel powder

To investigate the effects of pressure on the hot isostatic pressing(HIP) process of a stainless steel powder,density distribution and deformation of the powder at four different applied pressure levels were predicted and compared by using finite element method(FEM).Constitutive relations of porous compacts during HIP process were derived based on the yield criterion of porous metal materials.Thermo-mechanical coupling calculations were carried out by the MSC.Marc.Densification mechanisms were studied through evolutions of relative density,equivalent plastic strain and equivalent viscoplastic strain rate for compacts.The simulation results were also compared with experimental data.The results show that the densification rate and final density of compacts increase dramatically with the increase in the applied pressure level when it is below 100 MPa during HIP process,and the creep for compacts evolves into steady stage with the improvement of density.

Compressive Strength of Hydrostatic-Stress-Sensitive Materials at High Strain-Rates

Many engineering materials demonstrate dynamic enhancement of their compressive strength with the increase of strain-rate, which have been included in material models to improve the reliability of numerical simulations of the material and structural responses under impact and blast loads. The strain-rate effects on the dynamic compressive strength of a range of engineering materials which behave in hydrostatic-stress-sensitive manner were investigated. It is concluded that the dynamic enhancement of the compressive strength of a hydrostatic-stress-sensitive material may include inertia-induced lateral confinement effects, which, as a non-strain-rate factor, may greatly enhance the compressive strength of these materials. Some empirical formulae based on the dynamic stress-strain measurements over-predict the strain-rate effects on the compressive strength of these hydrostatic-stress-sensitive materials, and thus may over-estimate the structural resistance to impact and blast loads, leading to non-conservative design of protective structures.

Optimal Design of Electromagnetic Acoustic Transducer

This paper considers the design of EMAT （Electro-Magnetic Acoustic Transducer） based on numerical simulation. The EMAT consists of an exiting coil and two permanent magnets, which transmits the ultrasonic wave by the Lorentz force between the eddy current and the static magnetic field by the magnets. From the experimental result on self-prepared EMATs, the intensity and the directivity of the transmitted wave depend on the widths of the coil and the magnets. By means of EEM analysis the authors attempt to determine the optimal values of the above widths such that both the intensity and the directivity achieve the maximum or allowable performance.

大底盘多塔楼结构抗震设计要点初探

本文以框筒高层塔楼模型和多层框架裙房模型为研究对象,通过对单体计算结果与大底盘多塔计算结果的比较,研究分析大底盘多塔楼结构地震响应特点及构件内力分布规律。分析表明,在现有技术条件下,大底盘多塔楼的设计是可行的。该种结构形式不仅可以明显改善建筑的使用性能,在一定的条件下还能获得很明显的经济性。本文进一步总结出多塔楼大底盘设计的设计要点,供同类项目参考。

Effects of the radial force on the static contact properties and sealing performance of a radial lip seal

The radial force is a critical factor to determine the sealing performance of radial lip seals.The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments.Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used.Radial force,contact width,temperature in the sealing zone,the reverse pumping rate and friction torque are measured.A critical value of interference for a cost-effectively designed radial lip seal is found.Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance.The quantitative results gotten in this study could provide guide for the seal design and improvement.

Quasi-hydrostatic Primitive Equations for Ocean Global Circulation Models

Global existence of weak and strong solutions to the quasi-hydrostatic primitive equations is studied in this paper. This model, that derives from the full non-hydrostatic model for geophysical fluid dynamics in the zero-limit of the aspect ratio, is more realistic than the classical hydrostatic model, since the traditional approximation that consists in neglecting a part of the Coriolis force is relaxed. After justifying the derivation of the model, the authors provide a rigorous proof of global existence of weak solutions, and well-posedness for strong solutions in dimension three.