河南电视塔体形系数CFD数值模拟及随机风振响应数值分析(II)

建立电视塔的风振内力响应计算有限元模型,基于谐波合成法数值生成电视塔各分段的风波时程,采用ANSYS结构分析程序数值计算各风偏角下结构的动力响应,确定该电视塔不同高度上的风致振动位移响应、内力响应,给出了基于位移等效的动力放大系数与基于内力等效的动力放大系数。     

河南电视塔体形系数CFD数值模拟及随机风振响应数值分析(I)

采用CFD技术数值模拟了电视塔各分段上的绕流流场,获取了各分段上的体形系数、速度场及表面压力分布。各分段的绕流迹线显示各分段存在严重的流动分离;各分段上的体形系数的计算值与各相应的刚体模型风洞试验值比较显示,两者吻合得很好,进一步说明在类似具有复杂外形的高耸建筑物抗风初步设计阶段采用CFD技术进行流场计算以获取结构设计用的抗风参数是可行的。     

水平单调载荷作用下的桩基桥墩滞回特性

为研究桩基桥墩-地基系统的非线性性能,根据模型与原型的物理相似关系制作1∶5比例的桩基桥墩模型. 采用力-位移混合控制加载的拟静力试验方法,通过在墩顶施加水平单调增加载荷,得到墩顶水平载荷下桩基桥墩的载荷-位移滞回曲线、骨架曲线和滞回特性. 用非线性弹簧单元模拟土体、用梁单元模拟桩和桥墩,建立模型桥墩的计算模型. 计算模型的骨架曲线与试验模型的骨架曲线吻合较好,表明采用非线性弹簧单元和梁单元分别模拟土体和桩是可行的,可以为考虑土-结构相互作用时的桥梁抗震分析提供参考依据.     

The effect of temperatures on hybrid composite laminates under impact loading

The present experimental investigation deals with the impact responses of hybrid composites (carbon–glass fiber/epoxy) under various temperatures. A number of samples were subjected to increasing impact energy at the temperature range of ?20 to 60 °C until complete perforation of samples. With this use of increasing impact energies, it was possible to examine the impact response and failure mechanisms of hybrid composites until perforation of sample. An Energy Profiling Diagram (EPD) was used to obtain the penetration and perforation thresholds of hybrid composites. Besides, the temperature effects on impact characteristics such as load, contact time and permanent deflection were also presented in figures. Test results showed that temperature variations affect the impact characteristics of hybrid composites and they get their maximum values at ?20 °C or 60 °C.     

车辆荷载作用下混凝土箱梁桥桥面板局部振动分析

研究车-桥耦合振动条件下,混凝土箱梁桥桥面板局部振动规律.推导车-桥耦合动力平衡方程,用板单元建立简支箱梁桥有限元模型,采用3维7自由度车辆模型,由路面功率谱密度函数模拟得到等级分别为"理想"、"好"和"差"的路面不平度函数.通过数值模拟计算桥面板不同位置的竖向位移、纵向弯矩和横向弯矩的动力放大系数(DAF).分别对车道位置、路面等级、车速和桥梁阻尼进行了参数分析.结果表明,车辆荷载作用下,桥面板不同位置的局部DAF值、同一位置由不同响应量得到的DAF值之间均存在很大差异,采用统一的DAF来计算车辆对桥面板的冲击作用不甚合理.路面不平度是影响桥面板车致振动最为重要的因素;而车速次之,且很难找到明确的函数关系用于描述车速对箱梁桥面板的局部动力放大系数的影响.     

Temporal Thermal Behavior and Damage Simulations of FRP Deck

The finite-element method (FEM) has been employed to study the structural behavior of the fiber-reinforced polymer (FRP) bridge deck. The numerical results were verified with the field-test results provided by New York State Department of Transportation. Fully coupled thermal-stress analyses were conducted using the FEM to predict the failure mechanisms and the “fire resistance limit” of the superstructure under extreme thermal loading conditions. Furthermore, damage simulations of the FRP deck as a result of snow and ice plowing process were performed to investigate any possibility of bridge failure after damage occurs. Thermal simulations showed that FRP bridge decks are highly sensitive to the effect of elevated temperatures. The FRP deck approached the fire resistance limit at early stages of the fire incident under all cases of fire scenarios. The damage simulations due to the snow plowing showed minimal possibility of bridge failure to take place under the worst-case damage scenario when the top 5 mm of the FRP deck surface was removed. The results of both phases of simulations provide an insight into the safety and the reliability of the FRP systems after the stipulated damage scenarios were considered. Moreover, this paper provides discussions concerning the recommended immediate actions necessary to repair the damaged region of FRP deck panels and possible use of the bridge after the damage incident.