均匀来流下尾翼型抑振装置效果试验研究

基于控制尾流,阻止立管尾流漩涡脱落转换路径的涡激振动抑制机理,设计三角形尾翼、片状尾翼及交错尾翼等三种抑振装置。三种抑振装置分别安装于立管模型表面,立管模型采用外径为18 mm的透明有机玻璃管。通过在均匀流场中进行安装有该抑振装置的立管模型涡激振动试验,研究三种抑振装置对立管涡激振动的抑制效率,并通过与配重裸管的涡激振动数据对比,分析抑振装置对立管动力响应的影响规律。研究结果表明,三种抑振装置均取得了明显的抑振效果,与配重裸管相比,安装片状尾翼及交错尾翼的立管模型抑制效率可达90%以上,安装三角形尾翼后立管模型振动频率略有减小,而安装片状尾翼及交错尾翼的立管模型没有明显的主导频率。     

Stress Wave Propagation Analysis on Vortex-Induced Vibration of Marine Risers

To analyze the stress wave propagation associated with the vortex-induced vibration (VIV) of a marine riser, this paper employed a multi-signal complex exponential method. This method is an extension of the classical Prony''s method which decomposes a complicated signal into a number of complex exponential components. Because the proposed method processes multiple signals simultaneously, it can estimate the "global" dominating frequencies (poles) shared by those signals. The complex amplitude (residues) corresponding to the estimated frequencies for those signals is also obtained in the process. As the signals were collected at different locations along the axial direction of a marine riser, the phenomena of the stress wave propagation could be analyzed through the obtained residues of those signals. The Norwegian Deepwater Program (NDP) high mode test data were utilized in the numerical studies, including data sets in both the in-line (IL) and cross-flow (CF) directions. It was found that the most dominant component in the IL direction has its stress wave propagation along the riser being dominated by a standing wave, while that in the CF direction dominated by a traveling wave.     

钻柱恶性振动识别与抑制技术研究进展

钻柱振动问题在钻井实践中普遍存在,钻柱恶性振动是造成钻头、钻柱失效的重要原因,其会降低钻井时效,增加钻井成本。如何有效识别钻柱恶性振动并加以抑制是一个重要的课题,国内外对其开展了大量的攻关研究和工程实践。本文详细阐述了钻柱耦合振动的理论研究现状及最新发展趋势,对钻柱振动室内实验研究进行了总结,介绍了国内外井下振动监测装置、钻柱振动抑制工具研发与应用的最新进展;最后提出理论研究与室内试验相结合,研发钻柱动力学分析软件及井下振动识别监测工具,配套合适的抑制、减振工具是解决钻柱恶性振动问题的主要方法;同时建议开展振动抑制一体化解决技术的研究。     

采矿爆破振动波在岩溶区的传播影响因素分析

为研究不同情况下爆破振动强度衰变规律和振动对岩溶塌陷的影响,为当地矿山合理开采及减少地面塌陷灾害的发生提供可靠依据,对湖南水口山铅锌矿区进行现场爆破振动测试,并利用古丹铅锌矿实测数据作对比分析;试验矿区共布设4条测线,接收8组爆破振动数据。采用萨道夫斯基修正公式对采集的数据进行计算,以爆破产生的振动波频率及振动速度作为测试指标,对实测数据进行提取、处理,确定爆破振动波的频率及其在介质中的传播速度及地震波引发的质点振动峰值振速。试验结果表明:采矿活动是岩溶地面塌陷的主要影响因素;爆破振动波的频率衰减强度与其在岩土体中的传播距离和断层有关,振动波的传播速度受到岩土体性质、岩层结构特征、岩层走向等因素的影响。      

Forced vibration test of a building with semi‐active damper system

The authors developed a semi‐active hydraulic damper (SHD) and installed it in an actual building in 1998. This was the first application of a semi‐active structural control system that can control a building's response in a large earthquake by continuously changing the device's damping coefficient. A forced vibration test was carried out by an exciter with a maximum force of 100 kN to investigate the building's vibration characteristics and to determine the system's performance. As a result, the primary resonance frequency and the damping ratio of a building that the SHDs were not jointed to, decreased as the exciting force increased due to the influence of non‐linear members such as PC curtain walls. The equivalent damping ratio was estimated by approximating the resonance curves using the steady‐state response of the SDOF bilinear hysteretic system. After the eight SHDs were jointed to the building, the system's performance was identified by a response control test for steady‐state vibration. The elements that composed the semi‐active damper system demonstrated the specified performance and the whole system operated well. Copyright © 2000 John Wiley & Sons, Ltd.     

基于实测动冰力时程的海洋平台结构冰振反应分析

冰激平台结构振动是影响渤海石油钻采平台冬季正常生产和安全的主要因素。本文采用实测冰压力时程,对渤海辽东湾北部的ＪＺ２０－２ＭＵＱ平台结构进行了冰振反应分析,计算了不同设计冰厚、不同冰作用方向和标高及平台桩腿有无正倒锥体（一种破冰装置）的结构反应,探讨了正倒锥体对减轻冰力和结构反应的作用,发现了结构冰激振动的一些特征,为在该平台上实施振动控制方案提供了依据     

Horizontal impedance of square foundation in layered soil

This paper presents an extensive investigation into the influence of key mechanical and geometrical parameters on horizontal impedance of square foundations resting on or embedded in a two-layer soil deposit. The parameters investigated are the ratio of shear-wave velocities, the thickness of the top layer, the depth of embedment and the degree of contact between the footing-sidewall with backfill-soil. The results are presented in the form of simple and versatile dimensionless graphs, which should prove to be useful in understanding the steady-state harmonic response of square foundations in layered soils due to horizontal excitation. The investigation was conducted using a rigorous boundary element algorithm incorporating isoparametric boundary elements. Higher order quadratic elements were used since they can model the wavy nature of the dynamic problem investigated more accurately.     

上海打桩振害监测与分析

分析研究了打桩振害机理、振动理论计算、打桩监测设备和技术方法、振害判断依据、振害防治等,并结合工程实例探讨了上海地区打桩振动的特性。     

Effect of fault jogs on frictional behavior: An experimental study

Studying the effect of geometrically irregular bodies on the mechanical behavior of fault activity is of significance in understanding the seismic activity along a fault zone. By using rock mechanics ex- periment with medium-scale samples, we have studied the effect of fault jogs, the most common irregularity along fault zones, on frictional behavior. The research indicates that extensional fault jog can be easily fractured because of its low strength and the fractured jog has no obvious resistance to fault sliding, and the micro-fractures occurring in the jog are indicative of stick-slip along the faults. The fault zone containing extensional jogs is characterized by velocity weakening and can be described by rate and state friction law. Compressional fault jog makes fault sliding more difficult because of its high fracturing strength, but the micro-fractures occurring in the tensile areas around fault ends at higher stress level can provide necessary condition for occurrence of stick-slip along the faults before the jog is fractured and thus act as precursors of fault instability. Compression jog can be taken as a stable indicator of fault segmentation until the jog is completely fractured and two faults are linked.     

国家体育馆屋盖模型二维地震反应试验研究

国家体育馆双向张弦屋盖模型模拟地震振动台试验是国内外首次进行的如此大尺寸空间结构的试验,作者进行了竖向和水平的二维地震动输入的振动台试验,通过对试验得到的结构在二维地震动作用下的加速度、应变、内力响应的分析,为评价国家体育馆屋盖结构在二维地震作用下的抗震性能及今后同类结构的抗震设计提供了试验数据,同时结果表明双向张弦结构具有良好的抗震性能,是一种具有良好应用前景的新型大跨度结构体系。