阶梯形变截面梁的弯曲变形

提出了计算阶梯形变截面梁弯曲变形的一种新方法．算例表明，本文方法和结果对静定和超静定梁均适用，并且计算简捷，便于应用．     

粘弹阻尼材料迟滞非线性特性的试验研究

粘弹阻尼材料是具有良好减振和降噪作用的一种新材料，本文通过试验证明了阻尼材料确定存在迟滞非线性特性。     

行波效应对张弦梁结构地震响应的影响分析

以广州国际会展中心单向空间张弦梁结构这一典型张弦梁结构为计算分析算例,应用大型有限元软件ANSYS对张弦梁结构的地震响应进行了空间非线性时程反应分析。通过考虑地震波以不同速度传播引起的行波效应,研究了大跨度张弦梁结构在此类情况下的地震响应,分析了大跨空间张弦梁结构在横向、竖向和纵向3向地震联合作用下考虑非一致输入条件的地震响应变化规律的关系。研究结果表明,行波效应的影响与波有关,不同地震波作用下结构的响应有很大的差异,视波速越小对结构的地震响应越明显。     

非线性梁静力学问题的小波有限元方法研究

针对小应变适度挠度的非线性梁,采用变分法和小波有限元离散了其微分方程,推导了其对称和不对称刚度矩阵,结合复数步进法生成切线刚度矩阵,求解了梁中点的位移。结果表明：采用不对称刚度矩阵以及复数步进法生成切线刚度矩阵,与传统有限元对比,小波有限元迭代次数少,数值收敛快,而切线刚度矩阵的显式表达式并不能使迭代收敛。小波有限元数值结果精确可靠,且在两端可移铰接和两端简支边界条件下,其迭代收敛所花时间大幅减少。     

具强阻尼项非线性梁方程的扰动问题的整体解

在考虑强阻尼效应的情形下,研究了一类轴向载荷作用下的弹性梁方程的扰动问题的整体解的性态.利用Gronwall不等式证明了该扰动问题在线性边界条件下弱解的存在唯一性.     

随机参数梁弯曲振动时的动力特性分析方法

对结构参数具有随机性的梁结构受到弯曲振动时的动力特性进行了分析讨论,提出了研究梁弯曲时其结构参数的随机性对其动力特性的影响的一种新方法,从概率分析的观点出发推导出了随机参数梁弯曲振动时的动力特性数字特征的表达式,从而表明了随机参数梁结构在弯曲振动时动力特性随机性的影响因素.     

非线弹性梁的几何非线性幅频响应分析

针对非线弹性梁的几何非线性振动方程,采用林滋泰德一庞加莱法将非线弹性控制方程摄动展开成几个线性控制方程,略去线性控制方程中的小参数项并对其无量纲化。针对不同边界条件粱取试函数,同时运用Galerkin原理,分离出时域函数简化方程,对简化方程进行首次积分得到其混合非线性自由振动频率解析解,并对材料参数B对频率响应的影响进行了讨论。从计算结果上看,不考虑B对频率响应的影响时,文中解析解与理论解吻合较好;考虑B对频率响应的影响后,随着材料参数B的增大,非线性振动的响应频率呈现出下降的趋势,B对非线性振动频率和位移响应的影响变得明显,此时B对非线性振动的响应频率的影响将不可忽略。     

梁的非线性振动问题的拟小波精细积分方法

建立了求解梁的非线性振动问题的拟小波-精细时程积分法,利用拟Shannon小波对空间域进行离散,将问题转化为常微分方程组,然后用精细时程积分法对其求解,得到了梁的非线性振动问题的有效离散格式。     

均布载荷作用下悬臂不可压饱和多孔梁的非线性变形

Nonlinear bending of cantilever incompressible poroelastic beams subjected to a uniform load is investigated with the constraint that fluid flow is only in the axial direction. The governing equations for large deflection of the poroelastic beam are derived from theory of incompressible saturated porous media. Then, nonlinear responses of a cantilever beam with impermeable fixed end and permeable free end are examined with the Galerkin truncation method. The deflections and bending moments of the poroelastie beam and the equivalent couples of the pore fluid pressures are shown in figures. The differences of the results between the large deflection and the small deflection theories are analyzed. It is shown that the results of the large deflection theory are smaller than those of the small deflection theory, and the time needed to approach their stationary states for the large deflection theory is shorter than that for the small deflection theory.     

Dynamical Behavior of Nonlinear Viscoelastic Timoshenko Beams with Damage on a Viscoelastic Foundation

Based on convolution-type constitutive equations for linear viscoelastic materials with damage and the hypotheses of Timoshenko beams with large deflections, the nonlinear equations governing dynamical behavior of Timoshenko beams with damage on viscoelastic foundation were firstly derived. By using the Galerkin method in spatial domain, the nonlinear integro-partial differential equations were transformed into a set of integro-ordinary differential equations. The numerical methods in nonlinear dynamical systems, such as the phase-trajectory diagram, Poincare section and bifurcation figure, were used to solve the simplified systems of equations. It could be seen that simplified dynamical systems possess the plenty of nonlinear dynamical properties. The influence of load and material parameters on the dynamic behavior of nonlinear system were investigated in detail.     

Effect of corrosion on bond behavior and bending strength of reinforced concrete beams

There is growing concern for corrosion damage in reinforced concrete structures with several decades’ service. Pullout tests and beam tests were carried out to study the effect of reinforcement corrosion on the bond behavior and bending strength of reinforced concrete beams. The bond strength of plain bars and concrete initially increases with increasing corrosion, then declines. The turning point depends on the cracking of the concrete cover. The bond strength of deformed bars and concrete increases with corrosion up to a certain amount, but with progressive increase in corrosion, the bond strength decreases, and the cracking of the concrete cover seems to have no effect on the bond strength. On the basis of test data, the bond strength coefficient recommended here, which, together with the bond strength of uncorroded steel bars and concrete, can be used to easily calculate the bond strength of corroded steel bars and concrete. The bond strength coefficient proposed in this paper can be used to study the bond stress-slip relationship of corroded steel bars and concrete. The bending strength of corroded reinforced concrete beams declines with increasing reinforcement corrosion. Decreased bending strength of corroded RC beam is due to reduction in steel bar cross section, reduction of yield strength of steel bar, and reduction of bond capacity between steel bar and concrete. Project supported by Cao Guanbiao Key Technology Development Founding of Zhejiang University and Construction Ministry of China.     

Galerkin截断方法在轴向运动梁问题中的应用

研究了Galerkin截断方法在不同支承条件下轴向运动梁振动问题中的应用．利用离散化后的微分方程在u-vf平面上的失稳区域随离散维数的变化情况，验证了两端铰支的轴向运动梁取正弦函数做Galerkin截断方法时所得结果的正确性，对于两端固支的轴向运动梁，选取不同的特征函数，分别应用Galerkin截断方法并比较所得结果，最后得到适用于此种支承条件下的离散方法．     

Fully Discrete Nonlinear Galerkin Methods for Kuramoto-Sivashinsky Equation and Their Error Estimates

WeconsidertheKuramoto-Sivashinsky(K-S)equationinonespacedimensionwithperiodicboundaryconditionalldzero1lleantwhere110(x)isl-periodicandofzero"lean.TheK-Sequationmodelspatternformationsindifferentphysicalcontexts["3"landisaparadignloflowdimensionalbehaviou…     

Numerical simulation on dynamic bending strength of three-graded concrete beam based on meso-mechanics

To study the bending strength of mass concrete under dynamic loading, the pure bending zone of three-graded concrete beam is considered as a three-phase composite composed of matrix, aggregate and interface between them on meso-level. Dynamic constitutive model considering strain-rate strengthening effect and damage softening effect is adopted to describe the cocrete and meso-element's damage. The failure mechanisms of beam under impact loading, triagle wave load, dynamic load coupling with initial static loading were simulated by using displacement-controlled FEM. Furthermore, stress-strain curve of the specimens and their dynamic bending strength were obtained. The results obtained from numerical simulation agreed well with experimental data.     

轴向扩散下不可压饱和多孔简支弹性杆的弯曲

Based on the mathematical model of the bending of the incompressible saturated poroelastic beam with axialdiffusion, the quasi-static bendings of the simply supported poroelastic beam subjected to a suddenly applied constant loadwere investigated, and the analytical solutions were obtained for different diffusion conditions of the pore fluid at the beamends. The deflections, the bending moments of the solid skeleton and the equivalent couples of the pore pressures werepresented in figures. It is also shown that the behavior of the saturated poroelastic beams depends closely on the diffusionconditions at the beam ends, especially for the equivalent couples of the pore pressures. It is found that the Mandel-Cryereffect also exists in the bending of the saturated poroelastic beams under specific diffusion conditions at the beam ends.     

Numerical Solutions for Nonlinear Fredholm Integral Equations of the Second Kind and Their Superconvergence

lintroductionThispaperdiscussesthenonlinearFredholm-integralequationsofthesecondkindx(l)--Aj:'F(t,);,x(y))dy=f'(l),aStSb,(l)wherej'andFareknownfunctions,x(l)isthefunctiontobedetelillinedandAisaconstant.Thiskindofintegralequationsemergeinmanyappliedresearc…     

Finite Element Method Based on Equivalent Magnetic Energy Method for Computation of 2D Nonlinear Eddy Current Field

lintroductionInrecent20years,owingtotilerapiddevelopnlentofco.nputertechnology,tiletiniteelenlent1netnodforstndyingelectronlagneticfieldwasdevelopedti.onltheoreticalconlputationtoconnnercialsoftwarepackageinvestigation,towardstiledirectionofCAD,andgradnan…     

多约束非线性背包问题的一种有效算法

1IntroductionWe consider the following multi-di mensional nonlin-ear knapsack problem(MNKP)maxf(x)=∑nj=1fj(xj)s.t.gi(x)=∑nj=1gij(xj)≤bi,i=1,…,m,x∈X={x|lj≤xj≤uj,xjinteger,j=1,…,n},where allfjand allgijare nondecreasing functions ofxjon[lj,uj]forj=1,…,n,i=1,…,m,andljandujare integer lower and upper bounds forxj,re-spectively,j=1,…,n.It has been proved that0-1linear knapsack problemis NP-hard[1].Nonlinear knapsack problems have numerous appli-cations in various fields,for example,ca…     

求解非线性约束优化问题的一个数值延拓算法

1　IntroductionThenonlinearconstrainedoptimizationproblemisaveryimportantmathematicalprogrammingprob lem .Ithasbeenstudiedextensively ,andmanyalgo rithmsforsolvingthis problemhasbeen pro posed[1,2 ] .Mostalgorithmsforsolvingthenonlinearcon strainedoptimization problemislocallyconvergent ,suchastheNewtonmethod ,theBFGSmethodandtheSQPmethod ,etc .Toovercomethisdrawback ,manyextendediterativemethodshavebeendevel oped .Forexample ,theNewtonmethodincorporatedwiththelinesearch[1] andhomotopymeth…