软土场地基础隔震建筑减震性能研究

本文研究土与结构相互作用(SSI)对多层及中高层基础隔震建筑地震需求及隔震效率的影响规律,隔震层采用LRB铅芯橡胶与LNR普通橡胶隔震支座组合,就我国现行《建筑抗震设计规范》(GB50011-2010)中软土场地设置隔震层问题做探讨。提出土与基础隔震结构相互作用的简化计算模型,对不同场地及隔震设计目标下的多层及中高层基础隔震结构进行时程分析。研究表明:软土场地基础隔震建筑隔震层的有效隔震效率相对于硬土场地有所下降,必须通过设置具有一定规格的LRB支座来满足隔震目标。本文给出了铅芯橡胶支座极限变形需求随建筑层高及隔震目标变化的规律。     

H/V谱比方法在强震记录应用中几个影响因素的初步研究

随着我国强震记录的积累,利用强震记录进行工程场地抗震设防研究成为必然。使用滇西南地区2007—2011年间强震台网记录到的强震动记录数据,研究使用水平/垂直谱比法(H/V)处理强震数据时的几个影响因素。通过研究发现:在使用H/V谱比法进行场地地震效应研究时,强震记录和地脉动记录存在较大的不同;使用强震记录可以获得更多的震源和台站场地参数信息,但这同时也相应增加了强震数据使用时的难度。比较国内外学者使用强震数据进行场地地震效应的研究成果,分析在使用强震数据时存在的问题,最终给出使用强震记录研究场地效应的建议。     

非对称单侧混合梁斜拉桥多点激励地震响应分析

以一座主跨为820 m的双塔非对称单侧混合梁斜拉桥为研究对象,对其进行动力特性分析。运用相对运动法进行多点激励地震响应计算,分析行波效应对塔顶、主梁、塔底等关键位置动力响应的影响,同时对比分析入射角方向（即斜拉桥两侧相对方向）对其动力响应的影响。结果表明：与一致激励分析结果相比,多点激励使得主塔内力结果偏小,而使得主梁内力结果偏大;不同入射角地震激励对非对称大跨度斜拉桥的内力也会产生较大影响,内力变化可达20%。因此,在进行该类型非对称混合梁斜拉桥设计中,应考虑非一致激励效应和地震动输入方向的影响因素。     

A comparative study of the hopanoid hydrocarbons in sediments of two lakes (Fuxian and Changdang) with contrasting environments

Biologically configured ββ-hopanes, geologically configured αβ-hopanes and the biogenic hopenes were determined in dated sediment cores from Lake Fuxian in SW China and Lake Changdang in Eastern China in order to investigate anthropogenic influences on the abundance, composition and provenance of hopanoid hydrocarbons in lake sediments. Based on the results, hopenes were prevalent, with maximum values reaching 148.9 μg g⁻¹ TOC in sediments of Lake Fuxian, an oligotrophic deep lake (average depth 89.6 m), where the long water column provided ample potential for the growth of hopene-producing bacteria especially the cyanobacteria. Sediment hopenes have diminished in abundance to values of 13.4–78.5 μg g⁻¹ TOC in Lake Changdang, a eutrophic shallow (average 0.8–1.2 m) body, reflecting comparatively reduced importance of nutrient level on hopene production. Historical trends in hopenes input to the sediments of each lake are strongly dependent on nutrient status. During the last few decades, human-induced eutrophication has greatly boosted bacterial production, enhancing the accumulation of hopenes in sediments. Inputs of petroleum-derived αβ-hopanes were exceptionally high (average 71.2 μg g⁻¹ TOC) in post-1968 sediments from Lake Changdang, their increase coinciding with the advent and acceleration of petroleum product use around the lake, in particular by fishing boats. Lake Fuxian on the other hand, has undergone slower economic development and the appearance of petroleum-derived αβ-hopanes in sediments was delayed to 1990 since when the average value has been 27.1 μg g⁻¹ TOC. The abundance of αβ-hopanes in Lake Changdang has created a marked decrease in the relative contribution of hopenes to total hopanoids since 1968. Conversely, the amounts of αβ-hopanes introduced to Lake Fuxian since 1990 has yet to yield a clear change in the overall proportion of hopenes, but the abundance of ββ-hopanes has declined relative to total hopanoid levels for the period.     

Equilibrium thallium isotope fractionation and its constraint on Earth’s late veneer

Equilibrium isotope fractionation of thallium(Tl) includes the traditional mass-dependent isotope fractionation effect and the nuclear volume effect(NVE). The NVE dominates the overall isotope fractionation, especially at high temperatures. Heavy Tl isotopes tend to be enriched in oxidized Tl^3+-bearing species. Our NVE fractionation results of oxidizing Tl^+ to Tl^3+ can explain the positive enrichments observed in ferromanganese sediments. Experimental results indicate that there could be0.2–0.3 e-unit fractionation between sulfides and silicates at 1650 ℃. It is consistent with our calculation results,which are in the range of 0.17–0.38 e-unit. Importantly,Tl’s concentration in the bulk silicate Earth(BSE) can be used to constrain the amount of materials delivered to Earth during the late veneer accretion stage. Because the Tl concentration in BSE is very low and its Tl isotope composition is similar with that of chondrites, suggesting either no Tl isotope fractionation occurred during numerous evaporation events, or the Tl in current BSE was totally delivered by late veneer. If it is the latter, the Tl-contentbased estimation could challenge the magnitude of late veneer which had been constrained by the amount of highly siderophile elements in BSE. Our results show that the lateaccreted mass is at least five-times larger than the previously suggested magnitude, i.e., 0.5 wt% of current Earth’s mass. The slightly lighter 205 Tl composition of BSE relative to chondrites is probable a sign of occurrence of Tlbearing sulfides, which probably were removed from the mantle in the last accretion stage of the Earth.     

应变率效应对600 MPa级高强钢筋混凝土框架结构抗震性能影响研究

为了更真实地进行钢筋混凝土结构抗震性能评估,应该考虑材料的应变率效应影响。600 MPa级高强钢筋作为新一代建筑钢材,尚无考虑应变率效应影响的600 MPa级高强钢筋混凝土框架结构抗震性能研究。首先进行了不同应变率下600 MPa级高强钢筋拉伸力学性能试验,利用试验数据拟合得到600 MPa级高强钢筋在不同应变率下的强度提高系数表达式,并利用OpenSees软件进行了配置600 MPa级高强钢筋混凝土框架结构抗震性能模拟分析,研究了应变率效应对框架结构抗震性能的影响。研究结果表明:随着应变率的增大,钢筋的屈服强度和极限强度均得到提高,屈服强度最大提高11.5%,极限强度最大提高8.9%;随着所考虑的材料应变率增加,配置600 MPa级高强钢筋框架结构最大顶点位移总体上呈减小趋势,地震波强度越强,应变率效应影响越大,而层间位移角减小幅值相差不大。研究成果可作为600MPa级高强钢筋混凝土框架结构抗震评估的依据。     

几种大型海藻对赤潮异弯藻生长抑制效应的初步研究

利用共存培养系统研究了大型海藻缘管浒苔、刚毛藻、石花菜、鸭毛藻、扇形拟伊藻、蜈蚣藻、海黍子、脆江蓠对赤潮异弯藻(Heterosigma akashiwo)生长的抑制效应并和孔石莼的作用进行比较。实验指出：孔石莼和缘管浒苔对赤潮异弯藻的抑制效应最强,石花菜次之;扇形拟伊藻、蜈蚣藻、刚毛藻、脆江蓠、海黍子虽表现出抑制作用但较差;鸭毛藻的抑制效应最弱。     

典型地貌景观指数的多尺度效应分析 ——以山西省运城市为例

 景观指数作为定量描述景观特征的指数,具有明显的尺度效应。进行景观指数的尺度效应研究,对进一步理解格局与尺度之间的关系具有重要意义。本文以TM影像为基础,选择山西省运城市平原、丘陵、山地及综合地貌4种不同地貌类型,对7个常用景观指数进行了多尺度效应分析。结果表明:不同地形上斑块密度(PD)、景观形状指数(LSI)、结合度(COHESION)3个指数有明显的粒度效应,随粒度的增加呈现逐渐减少的变化趋势;最大斑块指数(LPI)、周长面积比分维数(PAFRAC)、景观聚集度(CONTAG)和Shannon多样性指数(SHDI)4个指数随粒度的增加几乎不发生变化。不同地貌的景观指数随幅度的变化规律比较复杂,景观形状指数(LSI)随幅度的增加呈现逐渐增加的趋势,其余6个指数在较小幅度范围内变化比较复杂,但随着幅度的增大有逐渐趋于平稳的趋势。针对研究区不同地貌类型,其景观指数在不同粒度和幅度下有较大区别,可以根据景观指数值的大小来区分地貌的复杂程度。     

三峡水库坝区蓄水前水体对水库周边气温的影响

对三峡水库蓄水前位于坝区长江左、右两岸的3组气温观测资料进行对比分析,结果表明：①水体对水库周边气温有白天降温、夜间增温效应,可抑制极端最高气温,抬升极端最低气温;②总体上增温幅度比降温幅度大,增温幅度夏季大于冬季,春秋季居中,在20：00夏半年多大于冬半年,在08：00冬半年多大于夏半年,20：00、08：00增温幅度0．2～1．0℃的日数分别占总日数的46％、55％以上;③增温效应与降水季节性变化趋势基本一致,降水多的月份增温明显,降水少的月份增温幅度则较小;④降温幅度为春夏季小于秋冬季;⑤逐时气温分析显示,远水区较近水区各时次气温在10：00～15：00高0．1～0．4℃,其它时间尤其是夜间低0．1～0．7℃。     

鲜水河断裂带形变累积率及其效能评价

对沿鲜水河断裂带布设的跨断层形变测点水平形变和垂直形变累积率进行了计算,根据结果分析了该断裂带及其附近区域发生中强地震前的变化特征并对其进行效能评价.其结果表明：在鲜水河断裂带上每次地震前震源体附近断层都有一个形变累积率绝对值减小过程;沿鲜水河断裂带如果形变累积率出现低值异常,则未来1～1.5年左右的时间内其附近区域100～300 km范围内将有5.0级以上地震发生的可能;且垂直形变累积率预报效能优于水平形变。