P-M-φ分析对RC高墩的转动变形能力计算的适用性研究

为了研究RC高墩的抗震性能和试验方法,通过对4根RC高墩模型进行了拟静力试验,观察到墩底附近在加载后期均出现剪切斜裂缝,随着保护层混凝土逐渐脱落,主筋在断裂前发生明显的屈曲现象。这些现象说明RC高墩的实际破坏形态、破坏机理与P-M-φ分析的前提假设是不一致的。试件的实测极限曲率值,比P-M-φ分析计算值,小约50%,本文结论是P-M-φ分析会严重高估RC高墩的曲率能力,偏于不安全。

Interaction of Methane with Single-Walled Carbon Nanotubes: Role of Defects,Curvature and Nanotubes Type

We investigate the interaction of single-walled carbon nanotubes （SWCNTs） and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs in comparison with the semiconducting CNTs. The obtained results for the zig zag nanotubes with various diameters reveal that the adsorption energy is higher for nanotubes with larger diameters. For defected tubes the adsorption energies are calculated for various configurations such as methane molecule approaching to the defect sites pentagon, hexagon, and heptagon in the tube surface. The results show that the introduce defects have an important contribution to the adsorption mechanism of the methane on SWNTs.

高速公路隧道曲线路段视线诱导设施有效性试验

分析了高速公路隧道不同半径曲线路段的反光环数目对驾驶人曲率感知能力的影响规律;针对线形诱导标识和反光环2种典型视线诱导方案,应用驾驶模拟器进行室内仿真试验,通过测量驾驶人的弯道错觉程度和反应时间来衡量驾驶人的曲率感知能力,利用Origin软件分析了试验数据。研究结果表明:改善前,驾驶人对半径的高估程度大于35%,反应时间不小于5.46 s;采用3个线形诱导标识时,不同半径下弯道错觉程度和反应时间有小幅度降低,在半径为400 m的情况下曲率诱导效果较好,弯道错觉程度为6.12%,说明线形诱导标识可提高驾驶人的曲率感知能力,但提升效果不显著;采用3个可见反光环时,不同半径下弯道错觉程度均小于5%,且反应时间较改善前降幅大于37%,说明3个反光环能有效提高驾驶人的曲率感知能力,同时将反应时间控制在合理范围;基于Logistic函数拟合分析发现,不同半径下驾驶人的弯道错觉程度与反光环数目拟合曲线拐点接近3,且拐点处弯道错觉程度最低,同时,不同半径下反应时间与反光环数目成负相关,且当反光环数目大于4个时,反应时间呈现收敛趋势,说明增加可见反光环数目对降低反应时间作用有限,因此,推荐使用3个反光环进行高速公路隧道曲线路段视线诱导。