非线性动力特性的仿真分析

研究非线性动力特性可视化计算的仿真问题，建立了以时域微分方程描述的数学模型，探讨了该系统运动轨迹及其演变规律的可视化表示方式。     

单自由度齿轮系统的周期运动和混沌运动

建立了综合考虑齿侧间隙、时变啮合刚度、综合啮合误差等因素下的定轴直齿圆柱轮副的单自由度非线性动力学模型,利用变步长Runge-Kutta法对单自由度运动微分方程进行数值求解.结合系统的分岔图、相图和Poincaré映射图,对系统随频率变化时的动力学特性进行分析.结果表明:齿轮啮合频率的变化导致系统发生连续倍周期分岔,从而产生混沌运动.另外,由于齿轮间隙非线性的影响,系统还存在擦切分岔等非光滑分岔现象.     

半B-（p，r）-预不变凸函数与非线性规划问题

定义了一类重要的非凸函数——半B-（p,r）-预不变凸函数,它是半预不变凸函数的真推广．首先用例子说明了此类函数的存在性,并说明它是B一不变凸函数、半预不变凸函数和B-（p,r）-预不变凸函数的推广;然后,讨论了半B-（p,r）-预不变凸函数的基本性质与集合刻画,并给出了半B-（p,r）-预不变凸规划问题的非可微最优性条件,其结论具有一般性,推广了涉及不变凸函数、半预不变凸函数和B-（p,r）-预不变凸函数的一些结论．     

Nonlinear Creep Damage Model of Water Bearing Carbonaceous Slate and Its Application

Triaxial compression rheological experiments on carbonaceous slate specimens of deep buried tunnel were carried out on the rock rheology testing machine. Along with the increase of loading stress level and the improvement of moisture conditions, the initial attenuation creep phase, the stabilization creep phase, and the speedup creep phase were produced. By connecting Burgers model and the nonlinear viscoplastic body consisted of nonlinear viscous component η(n,t) parallel connected with the plastic component in series, the improved model could describe the speedup creep phase. Using this model to fit and analyze the rheological parameters of different moisture conditions, it is shown that η〖KG0.005mm〗 M、E M、E K and η〖KG0.005mm〗 Kwill decrease with negative exponential trend. Then water damage D(w) was introduced, and through deriving damage evolution equation, the nonlinear viscoelasticplastic model with water damage effect was established. Finally, the time effect deformation of surrounding rock under different times and different moisture conditions was studied by numerical simulation, and the results show that primary support should close in 168 h, and the best construction time for secondary lining is 360 h after the primary support is closed.     

Application of Pushover Method to Seismic Performance Evaluation of Tall Piers for Bridge

For bridge with tall piers, the influence of higher modes on structural responses becomes more evident. Modified MPA method(MMPA) which is based on MPA theory and the concept of “equivalent mode height” is presented. To verify the effectiveness and the degree of accuracy of this method, several Pushover methods including MPA and MMPA methods were adopted to analyze tall piers for bridge, and then compares the results with that in dynamic time-history analysis. It is shown that MPA and MMPA methods can improve computational accuracy comparing with other normal Pushover methods when seismic intensity is lower, whereas the computational accuracy for MMPA methods is superior to that in MPA analysis with the seismic intensity becoming larger.     

非线性算法在近红外预测木材密度中的应用研究

研究基于近红外光谱技术的木材密度预测。运用基于高斯核变换的非线性偏最小二乘法建立密度预测模型,并且对所建模型的评价参数进行了对比分析。结果表明该方法建立的预测模型能对样品的密度进行有效预测。研究表明样品近红外光谱信息与样品的实际密度值之间不是单纯的线性关系,非线性模型可以更好地表征二者之间的关系。     

根—土复合体强度及其非线性特性试验研究

[目的]研究根—土复合体的非线性破坏准则,并结合不同含根量(G=0.12%,0.24%,0.36%)、不同含水率(w=13.22%,16.22%,19.22%)条件下根—土复合体强度,开展根—土复合体非线性特性研究,为生态水土防治工作提供科学参考。[方法]采用GDS三轴仪开展了根—土复合体的固结不排水三轴试验,获得根—土复合体应力—应变曲线及抗剪强度指标。[结果]素土与根—土复合体应力—应变关系曲线为硬化型。含根量与根—土复合体峰值强度成正比关系,但含水率对其峰值强度的影响表现出反比关系。当G=0.36%时,根—土复合体峰值强度的最大增幅为70.1%;当w=13.22%时,根—土复合体峰值强度最大增幅为86.7%。根—土复合体非线性破坏准则在正应力低于临界应力时呈非线性,在正应力高于临界应力时呈线性。c,k为根—土复合体非线性破坏准则中描述根系作用的关键参数,其中c与含根量和含水率均成正比关系,c越大,根系对根—土复合体强度的贡献程度越大;k与含根量成反比,与含水率成正比,k越小,根—土复合体强度包线的非线性化特征越明显。[结论]含根量(G)和含水率(w)对根—土复合体强度有显著影响。...     

Seismic Response Analysis of Transmission Tower-line System under Multi-component Ground Motion Excitations

Seismic responses of power transmission tower-line system under multi-component excitations were analyzed by numerical simulation. A three-dimensional finite element model of transmission tower-line coupled system considering the geometric nonlinearity of transmission line was established. Twelve seismic records of different soil types were selected based on Code for Design of Seismic of Electrical Installations. Seismic responses of power transmission tower-line system under single component, two horizontal component and multi-component excitations were investigated using nonlinear time history analysis method, respectively. The results show that the responses of transmission tower-line system under multi-component excitations are significantly larger than those under single component excitation only, especially for considering vertical ground motion excitation only, and neglecting multiple nature of ground motion in analysis will underestimate the responses of the structure. To obtain an accurate seismic response and a better seismic design of transmission tower-line system, multi-component ground motion inputs need to be considered. The results provide reference for seismic design of transmission line practical engineering.     

Modeling and Its Application of Reinforced Concrete Columns Considering Nonlinear Shear Effects

A fiber beam-column element in conjunction with zero-length elements attached to its ends was proposed to simulate the flexural and shear mechanism respectively. Based on the Limit State Material model and the Shear Limit Curve model provided by OpenSees, the nonlinear shear effect of reinforced concrete column and its coupling with the flexural effect were defined. The reliability of the proposed model was validated by means of comparisons with existing test results. Finally, a plane frame from in-situ pushover test was simulated. It is shown that the proposed method, by taking the nonlinear shear effect into account, produces satisfactory results for frame columns with shear strength and stiffness degradation, while the conventional fiber beam-column element can hardly simulate actual flexure-shear failure mechanism for columns characterized by insufficient transverse reinforcement. The proposed method is applicable for nonlinear analysis of reinforced concrete frame structures with shear deficiencies.     

我国杉木通用性立木生物量模型研究

以我国南方地区的最重要针叶树种杉木为研究对象,综合利用非线性混合模型、哑变量模型和误差变量联立方程组方法,建立了适合杉木不同生长区域（总体）应用的一体化一元和二元地上生物量方程及根茎比函数.结果表明：不同总体的地上生物量模型之间存在显著差异,总体（一）的估计值要大于总体（二）,而地下生物量则差异不明显;地上和地下生物量方程的平均预估误差分别在5％和10％以内,可应用于不同区域的杉木林生物量估计.