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21.
替换阻尼杆件的双层柱面网壳被动控制振动台试验研究 总被引:6,自引:0,他引:6
本文在拟动力装置上对自行设计的孔隙式粘滞阻尼杆件进行了性能测试,并用其替换双层柱面网壳的部分下弦杆进行了被动减震控制的振动台试验,输人了多种能级的不同地震动,针对替换不同位置和数量的阻尼杆件进行了多种工况下的试验研究。试验结果表明减震效果明显,与理论分析结果吻合较好。 相似文献
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中国南方网纹红土是在季风气候条件下形成的一种特殊地层,对重建南方第四纪气候环境具有特殊重要的意义,但长期以来对网纹化过程的物化特点缺乏足够的认识。对江西九江、彭泽与湖南岳阳3个剖面的黏土质网纹红土中白色网纹和红色基质分离后进行了地球化学元素、游离铁含量等测试,结果表明:(1)白色网纹中,发生了Fe、Mn、Th、Ga、Cu、Zn、Co、Ni、Cr、 V等元素的显著亏损,SiO2、Zr、Hf及轻稀土元素的显著富集,游离铁含量较低;红色基质中则完全相反;(2)网纹中Fe2+含量较高,基质中含量较低,揭示了网纹倾向于还原环境,基质倾向于氧化环境。研究认为网纹和基质这种氧化还原差异,是Fe、Mn、Co、Ni、Cr、V、Zn、Th、Ga、Cu等元素在网纹中游离淋失,并在基质中的沉淀富集,造成Zr、SiO2及轻稀土等在网纹中的相对富集、在基质中“稀释”而呈现亏损的主要原因。 相似文献
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This paper is focused on the research of seismic performance of cylindrical latticed-intersected-three-dimensional-beam-system (LITDBS) reticulated mega-structure with single-layer latticed-intersected-cylindrical-shell (LICS) substructures by time history method accounting for geometrical nonlinearity. The distribution laws of the dynamic internal forces and those of the ratios of the dynamic to static internal forces of members in this innovative structure are first studied. The behaviors of the structure under different multi-component seismic actions are analyzed, and the reasonable components of the seismic action that should be considered in design are thus obtained. Then taking the maximum dynamic internal force of the structure as the index, a series of parametric analyses are carried out, and the suitable values of several key form parameters are recommended. Additionally, the results by the response spectrum method with those by the time history method are compared, which indicates that the former is not on the safe side. Therefore, the mode-superposition response spectrum method can only be used to do preliminary seismic design of this kind of structure, and the results must be checked by the time history method at the end. 相似文献
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Auzende Jean Marie Van de Beuque Sabrina Dickens Gerald François Caroline Lavoy Yves Voutay Olivier Exon Neville 《Marine Geophysical Researches》2000,21(6):579-587
A recent swath-bathymetry and geophysical survey of the R/V L'Atalante in the Fairway Basin between Australia and New Caledonia allowed to confirm the Cretaceous age of the creation of the basin by continental stretching. This first stage of opening of the Fairway Basin is associated with the deposition of a continuous salt/mud layer feeding today numerous diapirs, some of them piercing the 3 to 4 km thick sedimentary cover and reaching the seafloor. In close link with this salt/mud layer a Bottom Simulating Reflector indicator of gas hydrates level occupies a 70000 km2 surface at about 500 to 600 m-depth beneath the sea floor. The coexistence of both BSR and diapirs suggests a thermogenic better than biogenic origin for the gas hydrates horizon. 相似文献
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Stephen J. Matthews Moyra C. Gardeweg R. Stephen J. Sparks 《Bulletin of Volcanology》1997,59(1):72-82
Lascar Volcano (5592 m; 23°22'S, 67°44'W) entered a new period of vigorous activity in 1984, culminating in a major explosive
eruption in April 1993. Activity since 1984 has been characterised by cyclic behaviour with recognition of four cycles up
to the end of 1993. In each cycle a lava dome is extruded in the active crater, accompanied by vigorous degassing through
high-temperature, high-velocity fumaroles distributed on and around the dome. The fumaroles are the source of a sustained
steam plume above the volcano. The dome then subsides back into the conduit. During the subsidence phase the velocity and
gas output of the fumaroles decrease, and the cycle is completed by violent explosive activity. Subsidence of both the dome
and the crater floor is accommodated by movement on concentric, cylindrical or inward-dipping conical fractures. The observations
are consistent with a model in which gas loss from the dome is progressively inhibited during a cycle and gas pressure increases
within and below the lava dome, triggering a large explosive eruption. Factors that can lead to a decrease in gas loss include
a decrease in magma permeability by foam collapse, reduction in permeability due to precipitation of hydrothermal minerals
in the pores and fractures within the dome and in country rock surrounding the conduit, and closure of open fractures during
subsidence of the dome and crater floor. Dome subsidence may be a consequence of reduction in magma porosity (foam collapse)
as degassing occurs and pressurisation develops as the permeability of the dome and conduit system decreases. Superimposed
upon this activity are small explosive events of shallow origin. These we interpret as subsidence events on the concentric
fractures leading to short-term pressure increases just below the crater floor.
Received: 12 December 1996 / Accepted: 6 May 1997 相似文献
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