Speciation of Chromium in Artificially Contaminated Soil Reference Material GSJ JSO-2 Using XANES and Chemical Extraction Methods

The oxidation states of chromium in GSJ JSO-2 (artificially contaminated soil) and three other geochemical reference materials (GSJ JSO-1, JLS-1 and JMS-1) were observed using X-ray near edge structure (XANES). For comparison, other artificially contaminated soil materials (mimic-JSO-2) were prepared by adding Cr(VI) into JSO-1. Their oxidation states of chromium were determined using XANES. The chromium contents were 1118 μg g^-1 for JSO-2, 1352 μg g^-1 for mimic-JSO-2 and 69-113 μg g^-1 for the other reference materials. Most chromium was present as hexavalent in mimic-JSO-2. No hexavalent species were detected in other samples. These results for chromium oxidation state in JSO-2 and mimic-JSO-2 obtained with XANES resembled those obtained from a chemical extraction method. The present JSO-2 has no trace of Cr(VI), although Cr(VI) was added as a major species during preparation. On the other hand, the content of Cr(VI) obtained in mimic-JSO-2 agreed with the original Cr(VI) content. A time-elapse study showed that Cr(VI) contents in mimic-JSO-2 decreased gradually to 70% of the original abundance during 240-day preservation in dry conditions. Moreover, the abundance of Cr(VI) decreased markedly to 15% after 240 days in the wet mimic-JSO-2 containing 20% m/m of water. These experiments suggested that soil humidity enhanced the reduction of Cr(VI) and that Cr(VI) was reduced even in dry conditions. Consequently, it is reasonable to infer that Cr(VI) doped into JSO-2 was completely reduced to Cr(III) during the preservation period of 5 years. The certification of the long-term stability of the chemical form in reference materials will be much more important in future.     

Shaking table tests of steel frame with superelastic Cu–Al–Mn SMA tension braces

Shaking table tests are performed on a one‐bay one‐story steel frame with superelastic Cu–Al–Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate‐independent piecewise‐linear constitutive model calibrated to the quasi‐static component tests of the SMA braces. This suggests that the loading rate dependence of Cu–Al–Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near‐fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near‐fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self‐centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi‐static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.     

空间半刚性连接钢框架有限元分析和研究

对带双腹板顶底角钢连接以及外伸端板连接空间钢框架进行了非线性有限元分析，研究了空间钢框架的静力承载性能与节点刚度的关系，得到了不同节点刚度对空间钢框架位移和内力的影响结果，对工程应用具有一定的参考价值。     

昆明人民胜利堂结构抗震改造设计研究

昆明人民胜利堂为钢筋混凝土、砖砌体及木结构混合而成的结构型式，其抗震改造设计较为复杂。简述了该结构抗震改造设计施工中的若干问题，以及解决这些问题所采取的相应措施。     

腹板摩擦式钢框架节点震后可更换性能的试验研究

主要针对梁腹板带有摩擦耗能螺栓的自复位钢框架节点结构进行抗震性能和可更换性能的试验研究,探讨该类节点在往复荷载作用下的滞回性能以及节点域的变形特征。在参数选型的基础上,对5组钢框架节点试件进行了低周反复荷载作用下的拟静力试验,其中:4组试件具有自复位能力,分析了各试件的承载力、刚度、耗能性能和滞回特性等性能。综合研究结果表明:所提出的拼接节点能够利用摩擦螺栓的滑移提高节点的耗能能力,有效减少梁和柱主体构件的损伤,同时预应力筋提供了结构的自复位能力。试验结果表明:在地震作用之后,通过更换腹板及摩擦螺栓可以使结构的承载能力和耗能性能与震前基本一致,从而实现结构功能的快速恢复。     

尼泊尔地震中樟木镇自建框架地震灾变机理研究

2015年尼泊尔遭受了4次7级以上大地震灾害,对我国西藏局部地区产生了重大影响。由于我国樟木镇是中尼两国的重要通商口岸,在此区域建造了大量尼泊尔式自建RC框架结构。通过对这些自建框架结构的震害调查,结合其独特的建造方式和结构特点,分析其抗震受灾能力,研究在地震作用下该类框架结构的地震破坏规律和致灾机理。研究结果表明:该类自建框架结构的构件承载能力利用率高,经济效益好,但安全储备小;地震破坏模式主要以框架柱失效和填充墙开裂为主;房屋建造层数对其地震致灾影响较大,该类房屋宜为1~7层;该类建筑结构抗震性能优越,适合在我国低烈度地区推广应用。研究成果对指导我国乡镇自建房屋的抗震规划及建设具有重要意义。     

弹塑性连接梁在双薄壁高墩连续刚构桥中的应用

针对罕遇地震中弹塑性杆件塑性变形而耗能的现象,探讨了在双薄壁高墩连续刚构桥中设置弹塑性连接梁的减震方案。分别计算了是否设置弹塑性连接梁的两个桥式,比较了在大震作用下墩柱的弯矩、剪力、位移变化情况。结果显示若设置连接梁,墩柱弯矩幅值在强震中下降幅度较大,剪力有所增加而位移幅值变化不明显。     

钢框架结构的非线性静力抗震可靠性分析：I有限元反应及其灵敏度

作为一种随机有限元方法，有限元可靠度方法通过有限元反应灵敏度分析将结构可靠度分析的近似解析方法与结构确定性分析的有限元方法结合起来，可以有效地处理结构反应是基本随机变量的隐式函数这一难题，因此成为大型复杂结构可靠度分析的有效工具。采用基于位移的非线性纤维梁柱单元对钢框架结构进行有限元建模，推导了单元与截面的基本方程。针对基于位移的纤维梁柱单元，采用逐级递进方式，分别推导了整体级、单元级、截面级和材料级的有限元反应灵敏度直接微分表达式。研究结果可为采用FORM或SORM等近似解析法进行钢框架结构的非线性静力有限元可靠性分析提供算法支持和编程依据。     

Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the water framework directive

A new assessment system for macrophytes and phytobenthos in German rivers meeting the requirements of the Water Framework Directive (WFD) of the European Community is described. Biocoenotic types based on biological, chemical and hydromorphological data from over 200 river sites covering the main ecoregions, hydromorphological stream types and degradation forms have been defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into three components: macrophytes, benthic diatoms and remaining phytobenthos. For macrophytes seven types including one subtype, for benthic diatoms 14 types including three subtypes and for the remaining phytobenthos five river types were identified. The benthic vegetation at reference condition was described for most of the river types. Degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For some of the described river types additional investigations are necessary before a classification system can be developed.     

Performance evaluation of satellite-based approaches for the estimation of daily air temperature and reference evapotranspiration

Different satellite-based radiation (Makkink) and temperature (Hargreaves-Samani, Penman-Monteith temperature, PMT) reference evapotranspiration (ET_o) models were compared with the FAO56-PM method over the Cauvery basin, India. Maximum air temperature (T_max) required in the ET_o models was estimated using the temperature–vegetation index (TVX) and an advanced statistical approach (ASA), and evaluated with observed T_max obtained from automatic weather stations. Minimum air temperature (T_min) was estimated using ASA. Land surface temperature was employed in the ET_o models in place of air temperature (T_a) to check the potency of its applicability. The results suggest that the PMT model with T_a as input performed better than the other ET_o models, with correlation coefficient (r), averaged root mean square error (RMSE) and mean bias error (MBE) of 0.77, 0.80 mm d^?1 and ?0.69 for all land cover classes. The ASA yielded better T_max and T_min values (r and RMSE of 0.87 and 2.17°C, and 0.87 and 2.27°C, respectively).