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This paper investigates the dynamic behavior and the seismic effectiveness of a non‐conventional Tuned Mass Damper (TMD) with large mass ratio. Compared with conventional TMD, the device mass is increased up to be comparable with the mass of the structure to be protected, aiming at a better control performance. In order to avoid the introduction of an excessive additional weight, masses already present on the structure are converted into tuned masses, retaining structural or architectural functions beyond the mere control function. A reduced order model is introduced for design purposes and the optimal design of a large mass ratio TMD for seismic applications is then formulated. The design method is specifically developed to implement High‐Damping Rubber Bearings (HDRB) to connect the device mass to the main structure, taking advantage of combining stiffness and noticeable damping characteristics. Ground acceleration is modeled as a Gaussian random process with white noise power spectral density. A numerical searching technique is used to obtain the optimal design parameter, the frequency ratio alpha, which minimizes the root‐mean‐square displacement response of the main structure. The study finally comprises shaking table tests on a 1:5 scale model under a wide selection of accelerograms, both artificial and natural, to assess the seismic effectiveness of the proposed large mass ratio TMD. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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本研究运用DSP高速数字信号处理器的实时信号处理与控制技术,研究了基于速度控制法、OS数值积分法和相应的实验误差控制法的子结构拟动力实验系统。该试验系统对动力加载装置采用速度控制,在加载过程中考虑了加载速率对实验结果的影响,使隔震橡胶支座的速度相关性能在试验中得到充分体现,同时采用OS数值积分法,充分地减少了试验的时滞误差,提高了试验精度。并通过不同加载速率的子结构拟动力实验研究了天然橡胶支座、高阻尼橡胶隔震支座和超高阻尼橡胶隔震支座对桥梁的隔震效果,在对实验结果进行分析对比后,定量地研究了不同的加载速率对隔震桥梁子结构拟动力实验结果的影响。 相似文献
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利用1981—2010年历史气象数据和2031—2060年（RCP2.6和RCP8.5）气候情景数据,根据橡胶寒害等级指标,结合插值分析、提取分析和地图代数等空间分析方法,研究在未来气候情景下我国橡胶树寒害事件的变化特征。结果表明：(1) RCP2.6和RCP8.5气候情景下2031—2060年我国橡胶种植适宜区基本呈现寒害发生降低的趋势,其中次适宜区（III）和局部可植区（IV）的降低幅度较为明显,有向高一等级适宜区转化的趋势。(2)我国橡胶树寒害中心的纬度,由1981—2010年的22.5°~23.5°N向北移动至2031—2060年RCP2.6情景下的24.0°~24.5°N和RCP8.5情景下的23.5°~24.0°N。(3) 2种气候情景下,2031—2060年我国海南、广西、广东、福建等植胶区橡胶树寒害发生概率（较基准时段1981—2010年）主要呈现降低趋势,云南植胶区在2种气候情景下有明显的差异,表现为RCP2.6情景下,轻度和特重寒害呈现降低趋势,中度和重度寒害呈现增加趋势;RCP8.5情景下,轻度和重度寒害呈现降低趋势,中度和特重寒害呈现增加趋势。(4)对比2种气候情景较基准时段的变化情况,RCP2.6情景对橡胶树轻度和特重寒害影响较大,RCP8.5情景对橡胶树中度和重度寒害影响较大。 相似文献
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对于近断层处高烈度区高层剪力墙结构，传统设计难以解决墙体太厚、配筋太大等难题。为研究在考虑近断层影响下高烈度区剪力墙住宅采用隔震设计的技术可行性，采用隔震设计对某剪力墙结构工程进行全面分析。对比分析常规剪力墙结构方案及增设橡胶隔震支座的隔震方案，分析结果表明，隔震方案较常规方案前3阶结构自振周期延长约3倍，从而有效减小了上部结构的地震作用；在设防烈度地震作用下，结构水平向减震系数为0.281，上部结构所受水平地震作用和抗震措施可按降低一度进行设计；罕遇地震作用下隔震支座性能稳定，上部结构基本处于弹性工作状态。研究结论可为隔震支座设计和进一步研究提供参考。 相似文献
5.
计算机上的橡皮膜技术 总被引：11，自引：1，他引：11
由于构制和修改任意形三维物体在技术上有一定的难度，三维物探人机联作反演长期未能得到实际应用。本文提出一种技术，称之为橡皮膜技术，可以灵活地构制任意形三维物体。其特点是：用鼠标器交替地移动设置在一个闭合曲面周围的若干控制点，控制点带动其附近的曲面变形，形成所期望的复杂形态的物体模型；还可按需要多次增加控制点的数目，对模型做更为精细地调节。文章详细介绍了该技术的核心－磨光算法。通过多次磨光，将一个由为 相似文献
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青藏高原对我国热带气候及橡胶树种植的影响 总被引：3，自引：0，他引：3
影响我国橡胶树存活以及产胶量的主要自然因素为寒潮低温与台风的强风.这些都与青藏高原的动力和热力作用有关:1.高原促进并加强寒潮爆发南下,使得我国热带冬季低温比同纬度地区较低.2.高原对于我国热带西部起着屏障寒潮减缓降温,而对于热带东部则起着漏斗狭管效应而加剧了降温.3.冬季高原的动力作用,在热带东部形成上升气流,在热带西部形成下沉气流,因而东部多阴雨天而西部多睛天.4.夏季的季风雨保证了橡胶树生长的需要,而冬季少雨尤其是西部少雨而多日照,有利于橡胶树的越冬,并有利于抑制某些病害.5.滇中、滇东的横断山脉可 相似文献
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Swidden (also called shifting cultivation) has long been the dominant farming system in Montane Mainland Southeast Asia (MMSEA). Today the ecological bounty of this region is threatened by the expansion of settled agriculture, including the proliferation of rubber plantations. In the current conception of REDD+, landscapes involving swidden qualify almost automatically for replacement by other land-use systems because swiddens are perceived to be degraded and inefficient with regard to carbon sequestration. However, swiddening in some cases may be carbon-neutral or even carbon positive, compared with some other types of land-use systems. In this paper we describe how agricultural policies and institutions have affected land use in the region over the last several decades and the impact these policies have had on the livelihoods of swiddeners and other smallholders. We also explore whether incentivizing transitions away from swiddening to the cultivation of rubber will directly or reliably produce carbon gains. We argue that because government policies affect how land is used, they also influence carbon emissions, farmer livelihoods, environmental services, and a host of other variables. A deeper and more systematic analysis of the multiple consequences of these policies is consequently necessary for the design of successful REDD+ policies in MMSEA, and other areas of the developing world. REDD+ policies should be structured not so much to ‘hold the forest boundary’ but to influence the types of land-use changes that are occurring so that they support both sustainable livelihoods and environmental services, including (but not limited to) carbon. 相似文献
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《地震研究进展（英文）》2023,3(1):100180
The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province, China. They include base-isolated buildings, multi-story reinforced concrete (RC) frame buildings, and masonry buildings. The near-field region is known to be tectonically highly active, and the local intensity level is the highest, that is, 0.4g peak ground acceleration (PGA) for the design basis earthquake, in the Chinese zonation of seismic ground motion parameters. The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy. The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings. It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement. Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field. However, careful forensic analyses are needed before any conclusive judgment can be made. 相似文献
10.
Grain Cadmium and Zinc Concentrations in Maize Influenced by Genotypic Variations and Zinc Fertilization 总被引：2，自引：0，他引：2 
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