蝴蝶拱桥稳定性多参数影响研究

以某蝴蝶拱桥为工程背景,建立该桥的空间有限元计算模型,分4个工况计算了该桥的稳定安全系数。通过改变拱肋外倾角度、拱肋刚度、端横梁刚度以及吊杆布置形式计算了不同设计参数下结构在恒载工况以及恒载+活载工况的失稳特征值。结果表明,拱肋的刚度对稳定性起着决定性作用;吊杆的布置形式只改变拱肋的面内刚度,对于面外刚度没有影响。     

离散元法在贵阳某层状岩质边坡稳定性分析中的应用

以实际工程为背景,介绍了贵阳某层状岩质边坡的特点,分析了边坡的破坏机理及破坏模式,采用二维离散元法对该边坡进行了稳定性分析,指出了在前缘临空情况下,边坡容易发生滑移-拉裂破坏。模拟计算结果与理论分析相符,说明用离散元法分析层状岩质边坡的稳定性是可行的。     

系泊系统耦合动力分析不同解法的比较研究

Newmark-β迭代法和Adams-Moulton法是系泊系统耦合动力分析中广泛使用的两种求解方法.文中运用这两种方法对系泊线进行动力分析,在验证了算法可靠性基础上,分析了两种方法在计算稳定性和效率方面的差异.结果发现:对系泊系统这两种算法拥有相似的计算精度,其中Newmark-β迭代法能适应较大的时间步长,稳定性更好;而Adams-Moulton法的计算效率随时间步长的增大提高很快,但增大步长Newmark-β迭代法的计算效率影响不大.     

赤山大桥基桩竖向承载力试验研究

介绍了应用自平衡法测试基桩竖向承载力的原理、应用程序及测试结果,并对测试结果进行了分析,探讨了基桩竖向承载的机理及承载特性。     

Solving the K-shortest paths problem in timetable-based public transportation systems

Finding the K-shortest paths in timetable-based public transportation systems is an important problem in practice. It has three typical variants: the K-earliest arrival problem (K-EAP), the K-shortest travel time problem (K-STTP), and the K-minimum number of transfers problem (K-MNTP). In this article we show that these problems can be solved efficiently by first modeling the timetable information with the time-expanded approach, then applying the Martins and Santos (MS) algorithm. Then we model the timetable information with the time-dependent approach and propose a modified version of the MS algorithm for solving the K-EAP. Experimental results on real-world data show that for K smaller than 100, which is enough for most applications, the execution times of the MS algorithm for the problems in the time-expanded model are less than 100 ms on a server with a 1.86-GHz central processing unit (CPU) and 4 GB of memory. For solving the K-EAP the modified MS algorithm in the time-dependent model is even more efficient (about three times faster for K ≤ 100) than the original algorithm in the time-expanded model. Our results imply the great potential of the MS algorithms in practical transportation service systems.     

Investigation of Occupant Lower Extremity Injures under Various Overlap Frontal Crashes

Objective

With widely usage of restraint system, fatal injuries to occupants have been largely limited while non-fatal lower extremity injuries have not been effectively improved. The present study aims to investigate occupant lower extremity injuries under realistic impact environments.

Methods

A biofidelic lower extremity model, a dummy model and a car cab model were combined to set up a realistic impact environment. Three typical frontal impact groups were simulated. Occupant global lower kinematics, long bone axial force and bending moment were presented to in-depth investigate lower extremity injury mechanism and tolerance.

Results

Various overlap frontal impacts cause totally different lower extremity kinematics in the combination of structural invasion and restraint system effects. The femur fracture occurred at a small axial force of 7.57 kN combing a substantial bending moment peak of 172 Nm. Ankle joint injuries were found in 100 % and 25 % overlap impacts that present large tibial axial force and joint rotation angle.

Conclusions

Overall results indicate that a coupling threshold of femur axial force and bending moment is of rationality to predict global femur fracture. The ankle joint injury occurrence is significantly related to the coupling effects of tibia axial force and excessive self-kinematics.

     

大跨度钢管混凝土拱桥拱肋吊装过程仿真分析

大跨度钢管混凝土拱桥的拱肋吊装是一个复杂的过程 ,为了保证最终的成桥线形和受力状态满足设计要求 ,需要采用施工控制仿真计算。本文给出了仿真计算的具体步骤 ,提出了基于迭代理论的前进分析方法 ,并通过实例验证了此方法的可行性     

船舶防污染机电一体化仿真系统

本文介绍了新开发的船舶防污仿真系统.该系统按照机电一体化的仿真思路,将电气控制界面和机械管路界面相结合,涵盖了船舶防污系统中主要的机械设备和电气设备控制电路,对于培养机电一体的新型船舶管理人员和航海类专业学生有重要意义.该系统已经应用在教学和船员培训中,并取得了良好的效果.     

城市轨道交通混凝土高架桥的耐久性设计

对我国城市轨道交通混凝土高架桥耐久性破坏的主要形态和破坏机理进行了分析,讨论了混凝土结构耐久性极限状态和设计使用年限,并从环境分类,混凝土的要求、最小保护层厚度、最大裂缝宽度限值、构造措施等方面提出了具有实用性的混凝土桥梁耐久性设计方法.     

质心侧偏角和横摆角速度对车辆稳定性的影响研究

通过对车辆稳定性控制理论研究,得出车辆的质心侧偏角和横摆角速度是稳定性控制的重要控制变量。并基于建立的二自由度整车仿真模型,进一步分析了它们对车辆稳定性的影响。