基于三维Copula函数的蚀坑预测模型

通过盐雾腐蚀试验研究了钢绞线在不同应力幅作用下的腐蚀规律,并且观测了钢绞线的腐蚀形态.从概率角度出发,得到了钢绞线蚀坑长度、宽度和深度的独立分布形式,然后基于三维Copula函数得到三者之间的联合分布规律,提出了三维蚀坑预测模型,并通过显著性检验对该模型进行了验证.结果 表明:Clayton Copula函数对于模拟蚀坑三维联合分布具有较高的精度;蚀坑使得钢绞线的抗拉强度和延伸率急剧下降,是钢绞线疲劳寿命下降的主要原因;三维蚀坑预测模型的提出,可以为预测钢绞线的腐蚀疲劳寿命提供参考.     

The discovery of the synovial lymphatic stomata and lymphatic reabsorption in knee effusion

To illustrate the mechanism of lymphatic reabsorption in knee joint effusion. The current investigation employed transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques to reveal the ultrastructure of the knee synovial membrane in New Zealand rabbits and human. Ultrastructural changes of the synovial lymphatic stomata were observed by using trypan blue absorption and sodium hydroxide (NaOH) digestion methods, and the animal models of synovitis. New Zealand rabbits and human synovial membranes were composed of two types of synovial cells: type A and type B. No lymphatic stomata were found among type A synovial cells, whereas lymphatic stomata with the diameters ranging 0.74–3.26 µm were found in type B synovial cells, and some stomata were closed. After the NaOH digestion, a number of sieve pores, similar to lymphatic stomata in size and shape, were observed in the dense fibrous connective tissue underneath the type B synovial cells. After injecting trypan blue into the rabbit knee joint cavity, absorption of trypan blue through the lymphatic stomata was observed, suggesting the absorption function of the synovial lymphatic stomata. In the rabbit knee joint synovitis models, the synovial lymphatic stomata diameter enlarged. Some macrophages migrated from the lymphatic stomata, indicating that the synovial lymphatic stomata were involved in the joint effusion absorption and inflammatory response. Our study is the first to report the existence of synovial lymphatic stomata in the New Zealand rabbits and human knee joints. Lymphatic stomata may have an important role in the reabsorption of joint effusion. Microsc. Res. Tech. 78:479–484, 2015. © 2015 Wiley Periodicals, Inc.     

钢管柱-H形梁内加劲铸钢模块节点抗震性能试验研究

介绍了钢管柱-H形梁连接内加劲铸钢模块节点的概念设计方法,对该节点进行了循环往复加载试验研究,考虑了不同轴压比对节点抗震性能的影响。试验结果表明：提出的铸钢模块节点具有良好的延性、较好的耗能能力、较高的承载力,可充分发挥节点域的剪切塑性耗能;铸钢模块节点的延性和耗能能力随着轴压比的增大略有降低。现行美国钢结构规范中的节点受剪承载力公式经修正后可适用于铸钢模块节点,且偏于安全;通过控制梁与节点域的相对强弱,可实现对节点屈服顺序的控制。     

胶合木网壳半刚性节点受力性能试验研究

针对凯威特六型胶合木网壳节点,设计并制作了12个足尺节点试件。进行了在胶合木构件轴压力为0、100、200 kN和300 kN共4种工况下节点的受弯承载性能试验,对节点抗弯刚度和受力性能进行分析,研究节点的弯矩-转角关系、节点域破坏模式及其与构件轴压力的关系。结果表明：节点域破坏模式可分为胶合木构件受压破坏、受拉破坏和界限破坏。节点域胶合木构件受拉破坏的节点受弯承载力随木构件轴压力的增大而增加。随着胶合木构件轴压力的增加,节点的初始抗弯刚度增大。发生节点域胶合木构件受压破坏的节点,其刚度较木构件受拉破坏的节点有较大提高。试验测得了节点的荷载-位移曲线和弯矩 转角曲线,并拟合得到了弯矩-转角关系方程,结果表明适度的木构件轴压力有助于提高节点连接的延性。     

扩大十字形截面型钢混凝土柱-SRC梁节点抗震承载力试验研究

提出了内置扩大正、斜向十字形截面型钢混凝土柱-工字钢型钢混凝土（SRC）梁节点的构造方式。通过对4个内置扩大正十字形和斜向十字形截面的型钢混凝土柱-SRC梁节点试件和1个内置普通十字形截面型钢混凝土柱-SRC梁节点试件的低周反复荷载试验,研究了试件的破坏特征、滞回曲线、骨架曲线、剪切变形和钢材应变,分析了配钢形式、加载角度和构造措施（直接焊接、竖向隔板连接）对节点受力性能的影响,并在此基础上对节点核心区受剪承载力进行了计算。试验结果表明：上述两种新型截面型钢混凝土梁柱节点均发生节点区剪切破坏,达到极限状态时,节点区箍筋及型钢腹板应力均达到屈服强度,试件型钢及翼缘框内混凝土仍能承担较大荷载,并趋于稳定;新型SRC梁柱节点核心区剪力-剪切角滞回曲线饱满,无捏缩现象,其受剪承载力比相同破坏模式的普通型钢混凝土梁柱节点试件大;柱内采用斜向布置十字型钢以及梁柱正交时,节点试件的剪切承载力更大,所提出的两种构造措施对节点承载能力影响不大。     

新型钢管混凝土柱节点开孔后抗压性能研究

进行了4组共9根钢管混凝土柱的轴心受压承载力的试验研究,一组作为对比试件,节点处不开孔,其余柱在节点处开孔,RC梁的钢筋穿过节点.观测了各柱工作性能和破坏形态,对比了钢管混凝土柱开孔和不开孔时的承载力,确定加强环和加强肋的效果.试验研究表明,由于加强环和加强肋的存在,管壁开孔对管柱的承载力影响不大,破坏模式均为在试件端部和靠加强环处钢管局部的鼓曲,在这些部位有应力集中现象;柱达到破坏荷载时管壁钢材均屈服,而加劲肋依然处于弹性.采用有限元软件ABAQUS对试验进行了模拟计算分析,有限元分析与试验现象一致,计算结果与试验值及设计理论计算结果符合较好.在上述研究基础上提出了实用的钢筋穿过钢管混凝土柱的构造要求.     

冷弯超薄壁C型钢墙梁节点抗震性能试验研究

对3个冷弯超薄壁C型钢组合墙体与组合楼盖连接的墙梁节点足尺试件进行拟静力试验,讨论不同墙架柱截面、不同轴压比对墙梁节点承载力、耗能能力的影响,得到了各节点的破坏特征、承载力特征值、延性和耗能系数。结果表明:墙架柱截面对冷弯超薄壁C型钢墙梁节点的抗震性能影响较大,C160mm×40mm×10mm×1mm截面试件的承载力是C89mm×44.5mm×12mm×1mm截面试件的1.5倍,延性系数约1.1倍。轴压比对冷弯超薄壁C型钢墙梁节点的抗震性能影响明显,0.4的轴压比下C160mm×40mm×10mm×1mm截面试件的承载力是0.2的轴压比时的2/3,延性系数约1/2。     

砂卵石地层过既有线的地铁暗挖施工技术

以成都地铁某车站穿越既有线设计施工为例,介绍了该施工方案的处理思路与施工步骤,并总结了地铁换乘节点施工技术及经验,经监测表明该施工方案安全可行,对类似工程具有一定的参考价值。     

Effects of openings on the punching shear strength of RC flat‐plate slabs without shear reinforcement

Openings in RC flat‐plate slabs are one of the critical factors that influence the punching shear strength of the slab and determine its thickness in the vicinity of the slab‐column joint. This study experimentally investigates the effects of openings on the punching shear strength of flat‐plate slabs without shear reinforcement. Tests were performed on eight flat‐plate slab specimens considering the layout and number of openings as test variables. The failure characteristics of each specimen are examined, and the effects of the test variables on the punching shear strengths of the test specimens are investigated. The measured punching shear strengths of the test specimens are compared with the predictions of several concrete design codes, including the American Concrete Institute (ACI), Comité Euro‐International du Béton and Fédération Internationale de la Précontrainte (CEB‐FIP) model and fédération internationale du béton (fib) model codes. This indicates that the reductions in punching shear strength due to the existence of openings are generally proportional to the loss of effective critical sections, and an L‐shaped opening layout around the corner of the column may further reduce the punching shear strength and may contribute to the loss of effective critical sections due to the existence of openings. Copyright © 2015 John Wiley & Sons, Ltd.     

节理倾角对岩石隧道掘进机破岩特性影响的数值研究

为研究节理特征对岩石隧道掘进机（TBM）盘形滚刀破岩特性的影响,采用颗粒离散元法（PFC）建立了不同节理倾角下双滚刀破岩模型并进行数值仿真,研究不同节理倾角对应的岩石破碎模式、裂纹数目和破岩比能。结果表明:（1）倾斜节理的存在改变了裂纹扩展规律,裂纹呈现不对称性扩展模式。节理的存在改变了裂纹的延伸方向,限制主裂纹向下扩展。节理倾角越大,对主裂纹的萌生与扩展起到的阻碍作用越明显。节理倾角较小时,裂纹沿节理倾向延伸,有利于双滚刀间裂隙的贯通,有利于岩石碎屑的剥落;（2）节理倾角对剪切裂纹的影响较小,主要影响拉裂纹数目。总裂纹数随节理倾角的增大先增大后减小,当节理倾角为30°时达到最大。从滚刀破岩效率来看,节理岩体存在一个最优节理倾角。当节理倾角在30°附近时,破岩比能最小,破岩效率最高。基于颗粒离散元法PFC2D可以较好地模拟节理岩体双滚刀破岩过程,弥补室内试验无法进行细观特性研究的缺陷。