Dynamic response of objects with shock-absorbers to seismic loads

The paper outlines a mathematical model describing the vibrations of buildings and engineering structures with general-type passive shock-absorbers, rigid bodies, and ideal constraints. Two modifications of systems with passive shock absorbers are considered assuming constancy of their structure. These systems are studied numerically; the dynamic processes excited in them are compared __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 12, pp. 127–137, December 2007.     

无砟轨道约束对高速铁路列车-桥梁系统地震响应的影响

建立了38自由度高速列车（动车/拖车）空间振动模型,基于非线性Hertz接触理论和Kalker线性蠕滑理论,引进PEER-NGA强震记录,建立地震作用下的高速铁路列车-无砟轨道/钢轨-桥梁-支座-桥墩-桩土系统精细计算模型,考虑支座刚度和桩土作用及近场地震效应的影响,以高速铁路32 m跨简支箱梁桥和CRTSⅡ板式无砟轨道为研究对象,编制了MATLAB程序,计算了有/无砟轨道约束下高速列车-桥梁时系统的地震响应。计算结果表明,不考虑三层无砟轨道时列车-桥梁系统模型由于桥梁刚度过大,列车-无砟轨道-桥梁系统的各项地震响应较列车-钢轨-桥梁系统有较大增加;对于有/无地震作用时,采用无砟轨道均可有效改进列车走行性能,近断层地震脉冲效应对有/无砟轨道约束系统动力响应及列车走行安全指标影响均较大。     

非线性子结构方法中实现对结构抗震措施阻尼器的数值模拟

应用子结构理论,对设置伸缩横缝的小湾高拱坝结构,分别就正常高水位常遇低水位两种水位工况,考虑坝体伸缩横缝在地震交变荷载作用下反复开合引起的缝面问滑移．接触等效应的影响,坝体一库水的相互作用而产生的动水压力的影响,对坝体的抗震性能进行了地震反应分析。对伸缩缝问设置阻尼器这一新的设计思想进行了可行性的研究,论证推导了阻尼器的计算模型,探讨了阻尼器对坝体结构抗震性能的影响。     

Design and mechanical characteristics analysis of a new viscous damper for piping system

In this paper, the design of a new viscous damper is presented and its mechanical characteristics are investigated experimentally. The motion equation of a system consisting of a drop machine and the damper is set up. By numerically simulating this equation, the curve of the damper cavity generatrix is obtained on the assumption that the resisting force is constant. Then the new damper with big capacity and high-energy dissipation rate is designed. Drop tests using this damper and a Pro225-damper bought in the market are performed, respectively. On one hand, the experimental resisting forces of the new damper approximate constants, which illustrates that the simulation is viable. On the other hand, some advantages of the new damper over the Pro225-damper are found.     

Differential equations of motion for a variable-mass holonomic system with a uniformly rotating constraint

In this paper, the differential equations of motion will be established for variable-mass holonomic mechanical systems constrained to the uniform rotation, including the equations in Lagrange form. Nielsen form and Appell form. The application of these new equations is illustrated with an example.     

硬岩中地下爆炸震源函数的数值模拟

利用一维球对称有限差分数值计算源程序模拟了硬岩中地下强爆炸的震源函数,给出了弹性半径处的位移、径向压力波形,得到了地下爆炸的折合位移势及其源频谱。相关计算结果与已有文献给出的结果一致。同时,对介质剪切强度与地下爆炸震源强度之间的关系进行了数值分析。研究结果可为硬岩中地下强爆炸地震耦合效应的计算提供参考。     

On aspects of damping for a vertical beam with a tuned mass damper at the top

In this paper, the wind-induced, horizontal vibrations of a vertical Euler–Bernoulli beam will be considered. At the top of the beam, a tuned mass damper (TMD) has been installed. The horizontal vibrations can be described by an initial-boundary value problem. Perturbation methods will be applied to construct approximations of the solutions of the initial-boundary value problem, and it will be shown that the TMD uniformly damps the oscillation modes of the beam. In the analysis, it will be assumed that damping, wind-force, and gravity effects are small but not negligible.     

Lyapunov stable penalty methods for imposing holonomic constraints in multibody system dynamics

This paper presents stability and convergence results on a novel approach for imposing holonomic constraints for a class of multibody system dynamics. As opposed to some recent techniques that employ a penalty functional to approximate the Lagrange multipliers, the method herein defines a penalized dynamical system using penalty-augmented kinetic and potential energies, as well as a penalty dependent constraint violation dissipation function. In as much as the governing equations are not typically cocreive, the usual convergence criteria for linear variational boundary value problems are not directly applicable. Still numerical simulations by various researchers suggest that the method is convergent and stable. Despite the fact that the governing equations are nonlinear, the theoretical convergence of the formulation is guaranteed if the multibody system is natural and conservative. Likewise, stability and asymptotic stability results for the penalty formulation are derived from well-known stability results available from classical mechanics. Unfortunately, the convergence theorem is not directly applicable to dissipative multibody systems, such as those encountered in control applications. However, it is shown that the approximate solutions of a typical dissipative system converge to a nearby collection of trajectories that can be characterized precisely using a Lyapunov/Invariance Principle analysis. In short, the approach has many advantages as an alternative to other computational techniques:

An automatic constraint violation stabilization method for differential/ algebraic equations of motion in multibody system dynamics

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｄｙｎａｍｉｃｅｑｕａｔｉｏｎｓｏｆｍｏｔｉｏｎｏｆｍｕｌｔｉｂｏｄｙｓｙｓｔｅｍｓｗｉｔｈｃｏｎｓｔｒａｉｎｔｓａｒｅｔｈｅｆｏｌｌｏｗｉｎｇｄｉｆｆｅｒｅｎｔｉａｌ／ａｌｇｅｂｒａｉｃｅｑｕａｔｉｏｎｓ,ｉ．ｅ．,Ｅ...     

大跨度桥梁多模态耦合颤振DTMD控制研究

DTMD是一种具有双频率的调谐质量阻尼器,与普通TMD相比,可以同时实现对主梁竖向和扭转运动的控制,具有较高的控制效率。本文基于多模态耦合颠振理论,导出带有DTMD的桥梁颠振系统运动微分方程,采用PK—F法求解系统颠振运动微分方程,并编制了多模态耦合颠振DTMD控制和参效分析程序,以崖门斜拉桥为算例,分析了DTMD对桥梁颤振控制的有效性并与普通TMD进行了对比,计算结果表明与传统TMD相比,DTMD对桥梁颠振具有更高的控制效率。     

Nonlinear One-Dimensional Seismodynamic Model of a Solid with Shock Absorbing Supports

A generalized method for constructing a nonlinear one-dimensional mathematical model of a solid on massive shock-absorbing supports of five different types is justified. The periods of small oscillations of the solid about the equilibrium position are determined. The equations of motion of the solid-support system with broken frictional bond are set up__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 3, pp. 135–144, March 2005.     

Numerical modeling of sloshing motion in a tuned liquid damper outfitted with a submerged slat screen

Tuned liquid dampers (TLDs) are among the most economical and effective passive damping devices. They have been increasingly used to reduce dynamic response and protect structures from failure due to external dynamic excitations. Slat screens are one of the most effective devices used to increase the inherent damping of a TLD, and to reduce the non‐linearity of the free surface motion. A numerical algorithm has been developed to solve the complete non‐linear, moving boundary flow problem in a TLD outfitted with slat screens. The model has been developed to handle conditions leading from small to large interfacial deformations without imposing any linearization assumptions. The numerical algorithm is based on the finite‐difference method. The free surface has been determined using the volume‐of‐fluid method and the donor–acceptor algorithm. The effect of the slat screens has been modeled explicitly by using the partial‐cell treatment method. The present algorithm has been validated against experimental data. The results indicated that the present algorithm is capable of providing accurate details of the flow field inside the TLD and through the screens. These details are essential to improve our understanding of the important parameters governing the performance of a TLD, and hence, to enhance our ability to design better TLDs. Copyright © 2010 John Wiley & Sons, Ltd.     

The bouncing motion appearing in a robotic system with unilateral constraint

The hopping or bouncing motion can be observed when robotic manipulators are sliding on a rough surface. Making clear the reason of generating such phenomenon is important for the control and dynamical analysis for mechanical systems. In particular, such phenomenon may be related to the problem of Painlevé paradox. By using LCP theory, a general criterion for identifying the bouncing motion appearing in a planar multibody system subject to single unilateral constraint is established, and found its application to a two-link robotic manipulator that comes in contact with a rough constantly moving belt. The admissible set in state space that can assure the manipulator keeping contact with the rough surface is investigated, and found which is influenced by the value of the friction coefficient and the configuration of the system. Painlevé paradox can cause either multiple solutions or non-existence of solutions in calculating contact force. Developing some methods to fill in the flaw is also important for perfecting the theory of rigid-body dynamics. The properties of the tangential impact relating to the inconsistent case of Painlevé paradox have been discovered in this paper, and a jump rule for determining the post-states after the tangential impact finishes is developed. Finally, the comprehensively numerical simulation for the two-link robotic manipulator is carried out, and its dynamical behaviors such as stick-slip, the bouncing motion due to the tangential impact at contact point or the external forces, are exhibited.     

考虑半覆水圆弧相变场地特征的地下多点地震动模拟方法与程序开发

建立了同时引入土壤介质相变和半覆水圆弧地形因素的场地模型,并给出了地下多点地震动模拟的理论框架,开发了依据本文理论的程序并予以可靠性验证。首先,基于探明的波场分布得到了SV波入射半覆水圆弧相变场地的频域解;其次,获得依据频域解的场地传递函数并求解出地下自功率谱,建立了基于所得到的地下相干函数的地下互功率谱,由此构建出地下功率谱矩阵;最后,实现频域模型向时域信号转化（即多点地震动时程曲线）,进而基于上述理论进行可视化程序开发。通过数值算例进一步阐明了本研究的意义,结果表明,（1）地下与地表多点地震动在能量分布上存在显著差异,说明了研究的必要性;（2）生成地震动的拟合功率谱和拟合相干函数与理论值吻合较好,表明了结果的合理性;（3）可视化程序界面简洁,参数输入及调整方便,后处理结果显示清晰,反映出程序的便捷及适用性。     

粉质黏土层预埋承插式混凝土管道对爆破振动的动力响应

为合理评价临近爆破施工振动作用对预埋在粉质黏土层承插式混凝土管道的影响,通过现场预埋多管节全尺寸管道的爆破试验,结合DH5956动态应变及TC-4850爆破振动等测试系统,研究了爆破振动作用下承插式混凝土管道动力响应特征,分析了管道管身及承插口动应变及振动速度空间分布规律;基于承插口允许转角规范及管身动态拉应变破坏准则,提出了承插式混凝土管道爆破振动速度安全判据。研究结果表明：爆破振动作用下管道管身及承插口之间存在不协调响应特征;爆破振动作用下管道承插口为管道最薄弱位置,爆破振动对承插式混凝土管道的影响应重点考虑承插口的失效;承插式混凝土管道爆破振动速度控制阈值为5 cm/s,结果可对类似地层中承插式埋地混凝土管道的保护起指导作用。

     

半覆水相变V形峡谷场地P波入射下的空间地震动散射频域理论解、验证及特征

克服介质相变、峡谷分层且局部地形覆水导致的固有边界值难题,首次推导并得到了半覆水相变V形峡谷场地对P波激励下的散射理论解,验证理论解的正确性,探究了相变界面的有无、入射波频率和入射角对地表位移的显著影响,突出并重点强调了覆水因素对结果影响的不可忽视性。分析结果表明,(1)以经典算例为标准,对比验证了本文理论解的正确性,解释并澄清了峡谷局部可预测性的微小偏差的来源。(2)与未覆水部位相比,峡谷覆水部位表面位移显著增大;与峡谷满水状态相比,相变面的存在使位移增大的初始位置向峡谷中间移动;不同的入射波频率和入射角下,地面运动情况存在显著差异,随着入射角的增大,水平方向的位移逐渐增大,竖直方向的位移逐渐减小。本文研究可为覆水V形峡谷的长大结构多点地震动的合理输入提供基础性研究依据,兼有理论意义与应用价值。     

高冲击载荷作用下弹载记录仪防护系统动力学响应特性

为了给弹载记录仪的防护设计提供依据,从机械振动的角度揭示了高冲击载荷作用下弹载记录仪防护系统的动力学响应机理。在分析弹载记录仪内部载荷传递关系的基础上,基于双自由度弹簧-质量-阻尼系统建立了一种简化的防护系统动力学响应模型,并开展了数值模拟,通过脉冲响应分析和谐响应分析辨识了模型参数。理论计算与数值模拟的对比分析结果表明：建立的动力学响应模型能较准确地预测高冲击载荷作用下弹载记录仪防护系统的动力学响应特性。在此基础上,以模型的幅频响应特性为依据,分析了防护系统动力学响应特性随各种参数的变化规律。研究结果可为更有效地指导弹载记录仪的防护设计提供依据。

     

变质量、变阻尼、变刚度结构系统的动力响应

本文首次提出了变质量、变阻尼、变刚度结构系统的动力响应问题,并根据抓斗卸船机的工作过程导出了结构系统的动力方程及解法。最后给出了工程实际算例。     

Parameter identifications for a rotor system based on its finite element model and with varying speeds

In order to achieve prediction for vibration of rotating machinery, an accurate finite element （FE） model and an efficient parameter identification method of the rotor system are required. In this research, a test rig is used as a prototype of a rotor system to validate a novel parameter identification technique based on an FE model. Rotor shaft vibration at varying operating speeds is measured and correlated with the FE results. Firstly, the theories of the FE modelling and identification technique are introduced. Then disk unbalance parameter, stiffness and damping coefficients of the bearing supports on the test rig are identified. The calculated responses of the FE model with identified parameters are studied in comparison with the experimental results.     

Navier solution for the elastic equilibrium problems of rectangular thin plates with variable thickness in linear and nonlinear theories

This paper discusses the elastic equilibrium problems of rectangular thin plates of varying thickness and simply supported on all four sides by linear and nonlinear theory. using the Navier method to seek an approach to the problem, and illustrates the solution with two examples. In conclusion, mention in made of scope of application and the convergency of the solution.