虚拟层合单元与杆单元在桥梁预应力混凝土结构分析中的合成方法

对预应力混凝土的计算方法和研究现状做出了评价,提出针对预应力混凝土结构分析的单元形式。通过自由度变换,把空间杆单元的节点自由度用空间虚拟层合单元的节点自由度来表示,即杆单元的节点无需固定在体单元节点上,共同模拟了预应力混凝土结构。在单元内采用选择性积分的方法计算单元刚度矩阵,用较少的单元模拟出了复杂的断面形式;并采用单独的空间杆单元模拟预应力束,能直接求解预应力对结构产生的变形和内力。经实例验证分析,使用该单元进行预应力混凝土结构分析,在网格划分比较稀疏的情况下,仍然获得较为精确的结果,较传统的预应力计算方法更为简单、更为准确。     

钢渣粉煤灰路面基层试验性能分析

钢渣与粉煤灰按一定配合比制备的路面基层材料的无侧限抗压强度、劈裂抗拉强度、回弹模量等常用性能良好,通过试验比较,证明钢渣与粉煤灰组合可以作为道路基层使用。     

沥青路面微波加热养护施工工艺

微波加热热再生是指在施工现场用微波加热路面,使可再次利用的旧沥青混合料与新添加的冷新料升温至合适的施工温度,再将乳化沥青喷洒到料里,搅拌均匀,最后摊铺碾压完成养护工作的一种施工工艺。微波加热热再生可根据现场情况决定是否喷洒乳化沥青并确定加入乳化沥青的量等,以便于现场施工控制。可利用的旧料现场再生利用,不可利用的旧料用新料代替。     

电针肾俞穴家兔心率变异性的谱分析

目的 用心率变异性的谱分析方法,探讨电针肾俞穴对自主神经功能的调整作用。方法 将９只新西兰家兔静脉麻醉,用疏密波电针肾俞穴２０ｍｉｎ。将电针前后的呼吸节律与心电波ＲＲ间期同步输入微机,和自回归模型进行谱分析。实验数据用配对ｔ检验法处理。结果 电针对家兔的心率减慢（Ｐ〈０．００１）,心率变异性增大（Ｐ〈０．０５）、低频峰面积增加（Ｐ〈０．０１）、高频峰面积减少（Ｐ〉０．０５）、两峰面积比增大（Ｐ〈     

强夯补强在高速公路填土路基中的应用

介绍了强夯的作用机理,通过分析夯沉量和压实度检测实验数据,说明强夯有效地提高了路基压实度,对防止工后沉降有重要作用。     

400 000 DWT矿砂船直接波浪载荷与全船有限元强度分析

超大型矿砂船由于船体结构的特殊性和船体本身的超大型化,船体强度用常规规范中的梁理论方法或舱段有限元计算校核很难涵盖船体的所有构件.以400 000 DWT超大型矿砂船为例,简单介绍了进行全船有限元分析过程中波浪载荷的选取、模型的建立以及加载、分析的全过程,对正确进行超大型矿砂船全船结构强度直接计算具有积极指导作用.     

原油管道结蜡预测模型研究

利用灰色GM(1,1)模型的全息信息特性,在不需要多因素分析的情况下,建立了输油管道的结蜡速度和结蜡厚度的灰色GM(1,1)模型,实现了部分信息情况下的原油管道结蜡预测。实际计算表明:该模型误差在±2%以内,完全满足工程实际需要。     

Effect of Gr Content and Hot Extrusion on Tensile Properties of （Nano-SiCp~-Gr）/Cu Composites Fabricated by Powder Metallurgy

Novel hybrid Cu matrix composites reinforced by graphite (Gr) particle with volume fraction of 5%?C15% and nano-SiC particle (nano-SiCp) with volume fraction of 3% have been prepared by powder metallurgy. The results show that Gr and nano-SiCp distribute uniformly in the Cu matrix. With increasing the volume fraction of Gr, the tensile strength of the composites decreases from 114 to 51MPa and the elastic modulus decreases from 75 to 60GPa. Compared with the sintered composites, the tensile properties including elastic modulus, tensile strength, yield strength and tensile elongation of the hot-extruded (nano-SiCp+Gr)/Cu composites are improved greatly due to higher relative density of the composites and more uniform distribution of Gr and nano-SiCp, in addition to finer grain size of the matrix as a result of dynamic recovery and recrystallization which occur during hot extrusion process.     

Formation of nanometer coherent structures during spinodal decomposition and ordering coexistence phase transformation in Fe-24Al alloys

The nanometer coherent structure evolution of spinodal decomposition and ordering coexistence phase transformation in Fe-24Al alloys is investigated by the microscopic phase field kinetic model. The results show that the concentration and long-range order parameters all continuously change towards to their equilibrium values during phase transformation. With the increase of elastic interaction energy, the anisotropy along [01] or [10] elastic soft direction is more obvious and the time reaching equilibrium state is also shortened. According to the results, the formation of nanometer coherent structures during phase transformation is composed of the initial decreasing stage of order degree stage, the incubation stage, the continuous increasing stage of concentration order parameter and long-range order parameter, and the later stable stage. The spinodal decomposition and ordering is interaction; the initial ordering stage is a necessary condition of the coexistence phase transformation. The nanometer coherent structures are not found to grow during the whole phase transformation. The simulation results are in accordance with the results in experiment obtained by the aging treatment in Fe-24Al alloys.     

基于改进直接刚度法的桥梁损伤定量评估

目前桥梁损伤评估主要采用基于可靠度理论、层析分析法、模糊理论、神经网络以及专家系统等的整体评估,桥梁局部损伤还仅限于定性评估阶段。本文研究改进了基于直接刚度理论的桥梁损伤评估方法,直接研究桥梁动力特性参数的变化值与其损伤程度大小之间的函数关系,从宏观角度定量评估桥梁损伤程度,并与曲率模态振型幅值法评估结果进行比较分析,检验该方法的应用效果。以云南大保高速K442+665特大桥为研究背景,建立空间有限元模型,对该桥的损伤进行模拟分析。研究表明其评估结果具有较好的准确性、有效性和适用性。对进一步研究混凝土桥梁损伤识别理论具有一定的推动作用。