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The single tie (sleeper) push test (STPT) is a common method to evaluate the lateral resistance of a railway track sleeper. This methodology evaluates the lateral resistance phenomenon in a static manner despite the fact that the majority of the exerted loads on a railway track have a dynamic nature. For this reason, a mass–spring–damper numerical model was created to investigate the dynamic lateral interaction between an isolated sleeper and ballast layer in the presence of various lateral impact loads. On the basis of the model outputs, a pendulum loading test device (PLTD) was designed and developed in the laboratory. In this regard, a cylindrical hammer with modifiable mass and triggering angle was installed on a steel frame for imposing lateral impact load on an instrumented concrete sleeper. The graphs of the sleeper–ballast interaction force versus the sleeper lateral displacement were extracted for different masses and triggering angles of the hammer. Considering a same condition for sleeper, the maximum value of this interaction force was called the dynamic lateral resistance (DLR) and static lateral resistance (SLR) respect to the dynamic and static states of lateral loading. Comparing the values of the sleeper DLRs and SLR indicated that unlike the constant SLR of 6.5 kN, the DLR was in the range 2–10.2 kN in the impact load domain of 3–40 kN. However, as a key finding, the average slopes of the DLR and SLR graphs were equivalent in the dynamic and static tests. 相似文献
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By using the digital observations of the pendulum tiltmeter, water tube tiltmeter,extensometer and volumetric strainmeter at Huzhou station and with the power spectrum density estimation method,we acquired the_0S_5-_0S_50 fundamental sphere free oscillations caused by the Japan earthquake on March 11,2011,then compared it with the PREM model. The relative errors are mostly bigger than 1.2‰. The extensometer and volume strainmeter can clearly detect _0S_2,_0S_3and_0S_4,which are closely related to the deep structure and earth's interior. 相似文献
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本文详细讨论了利用井下和地面观测直达波到时资料联合确定震源位置,发震时刻及区域平均波速的最优化方法,该方法对震源深度及波速的确定给予特别的重视与处理。理论检验和实际算例表明,用该方法编制的程序定位精度高,计算速度快,可以在地层差异小的地区推广应用。 相似文献
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This paper extends the scope of seismic isolation by introducing an innovative uplift‐restraining Friction Pendulum system. Termed the XY‐FP isolator, the new isolation device consists of two orthogonal opposing concave beams interconnected through a sliding mechanism that permits tension to develop in the bearing, thereby preventing uplift. Owing to its distinct configuration, the XY‐FP isolator possesses unique properties for a seismic isolator, including uplift restraint, decoupling of the bi‐directional motion along two orthogonal directions, and capability of providing independent stiffness and energy dissipation along the principal horizontal directions of the bearing. The study concentrates on introducing the concept and establishing the underlying principles of operation of the new XY‐FP isolator, formulating the mathematical model for the XY‐FP isolator, and presenting its mechanical behaviour through a displacement‐control testing program on a single XY‐FP isolator. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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为使仿人机器人能够稳定地行走,基于三维倒立摆模型,采用了可变ZMP(Zero-Moment Point)来进行仿人机器人的步态规划.在单脚支撑期依据可变ZMP来规划COG(Center of Gravity)的轨迹,在双脚支撑期内则让ZMP保持低速匀速运动,由此来规划此时间段的COG轨迹.仿真结果验证了规划的合理性,保证了更强的稳定性,并且使得采用此规划的仿人机器人的行走和人类的行走更加相似. 相似文献
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高层建筑利用悬吊质量摆的减震研究 总被引:12,自引:0,他引:12
本文研究了高层建筑利用悬吊质量摆的减振作用,首次提出了利用摆减小高层建筑多个振型反应的方法。文中给出了具有不同悬吊方式的摆-高层建筑结构体系的力学模型及振动方程,利用数值分析方法探讨了摆的不同悬吊方式及摆与结构的质量比等因素对结构地震反应的影响,给出了对于实际工程应用具有参考意义的结果。 相似文献
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Response of pendulums to complex input ground motion 总被引:1,自引:0,他引:1
Dynamic response of most seismological instruments and many engineering structures to ground shaking can be represented via response of a pendulum (single-degree-of-freedom oscillator). In most studies, pendulum response is simplified by considering the input from uni-axial translational motion alone. Complete ground motion however, includes not only translational components but also rotations (tilt and torsion). In this paper, complete equations of motion for three following types of pendulum are described: (i) conventional (mass-on-rod), (ii) mass-on-spring type, and (iii) inverted (astatic), then their response sensitivities to each component of complex ground motion are examined. The results of this study show that a horizontal pendulum similar to an accelerometer used in strong motion measurements is practically sensitive to translational motion and tilt only, while inverted pendulum commonly utilized to idealize multi-degree-of-freedom systems is sensitive not only to translational components, but also to angular accelerations and tilt. For better understanding of the inverted pendulum's dynamic behavior under complex ground excitation, relative contribution of each component of motion on response variants is carefully isolated. The systematically applied loading protocols indicate that vertical component of motion may create time-dependent variations on pendulum's oscillation period; yet most dramatic impact on response is produced by the tilting (rocking) component. 相似文献
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This paper describes an experimental program to examine the force–displacement behavior of a class of multi‐spherical sliding bearings. The primary goal of the experiments is to test the validity of the theory developed in a companion paper that describes the behavior of these devices. Experimental work consisted of testing the three primary variations of these bearings in several configurations of different friction and displacement capacities. Most tests were carried out at slow speeds; however, some testing was also conducted at high speed (up to approximately 400 mm/s) to examine the behavior under dynamic conditions. The results of experimental testing were generally found to be in very good agreement with the analytical results. It is shown that the forces and displacements at which transitions in stiffness occur are predictable and therefore controllable in design. Furthermore, the underlying principles of operation were confirmed by the fact that starting and stopping of sliding on the different surfaces occurred as expected from theory. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献