特殊地形条件下大跨度预制T梁架设施工技术

杭千高速千岛湖1号桥工程实践证明,在场地有限的山区,采用横移、纵移、侧面提升等工艺可以有效地解决大跨度T梁架设问题.     

强夯置换处理不良地质路基加固效果研究

结合实际工程地质特点,采用强夯置换对不良地质路基进行加同,处理前后载荷试验结果表明：强夯置换处理此类建筑垃圾填埋场能够起到良好的加固效果,路基土体承载力能提高2倍左有;施工过程孔隙水压力与水平位移监测数据表明,强夯置换置换体对路基土体的挤密作用是土体承载力提高的主要原因。     

对公路工程中特殊分包的探讨

对特殊分包从特殊分包人概念,与FIDIC条款中指定分包人的关系,特殊分包合同成立条件、成立过程,特殊分包的优缺点,对特殊分包的体会等方面,并结合东大桥工程实际进行了探讨。     

北京火车站接驳问题及对策

北京火车站是北京市的主要客站之一,在京津冀协同发展的背景下,区域经济发展和运输化的需求客观上需要实现各种交通方式的有效衔接,以保证客流及时、高效的疏散。针对北京站乘客换乘不便的问题,论述北京站客流节点的交通特征,以及区域交通接驳条件、问题症结,尤其是铁路与轨道交通的接驳问题。交通节点的问题放大到区域交通背景的研究,突显了北京站外围道路通达性不高、交通供给能力有限且无增容空间等问题,但是轨道交通2号线线网的剩余能力相对充裕,且客流到发晚高峰与通勤晚高峰不重叠。通过客流节点特征分析、区域对外接驳条件量化分析,为北京站交通接驳问题提出解决思路与对策,即充分利用轨道交通的运载能力,提高其接驳比例,释放区域更多的道路资源,避免对外交通与城市内各种交通方式无法实现有效的衔接。     

哈达山枢纽调水对扶余下游河段航运影响初步研究

利用拟合平面二维水流数学模型 ,分析研究了哈达山水利枢纽建成后 ,下泄 2 5 0m3 /s流量方案对扶余至三岔河口河段通航条件的影响 ,并提出了初步治理措施     

Development of distress condition index of asphalt pavements using LTPP data through structural equation modeling

Traditional pavement distress index such as the Pavement Condition Index (PCI) developed by U.S. Army Corps of Engineers determines coefficients of distresses based on subjective ratings. This study proposed an asphalt pavement distress condition index based on various types of distress data collected from the Long-Term Pavement Performance (LTPP) database through Structural Equation Modeling (SEM). The SEM method treated the overall distress index as a latent variable while various distresses were treated as endogenous and other influence factors such as age, layer thickness, material type, weather, environment and traffic, were exogenous observed variables. The SEM method modeled the contributions of various distresses as well as the influence of other factors on the overall pavement distress condition. Influences of age, layer thickness, material type, environment and traffic on the latent distress condition were in accordance with previous studies. Compared with previous attempts to model latent pavement condition index utilizing SEM method, more pavement condition measurements and influencing factors were included. Specifically, this study adopted the robust maximum likelihood estimator (MLR) to estimate parameters for non-normally distributed data and derived the explicit expression of latent variables with intercepts. A multiple regression prediction model was built to calculate an overall condition index utilizing those measured distress data. The established pavement distress index prediction model provided a rational estimation of weighting coefficients for each distress type. The prediction model showed that alligator cracking, longitudinal cracking in wheel path, non-wheel path longitudinal cracking, transverse cracking, block cracking, edge cracking, patch and bleeding were significant for the latent pavement distress index.     

Research of highway runway clearance rules

Aiming at the problems in the highway runway clearance condition evaluation, according to the improved obstruction requirement of highway runway, the inner transitional surface (ITS) and outer transitional surface (OTS) range are calculated and analyzed in detail, the shape range of the ITS and OTS is pointed out, the methods of calculating the intersecting line and the key various points among ITS, runway strip (RS), inner horizontal surface (IHS) in terminal clearance zone (TCZ), including among OTS, IHS and outer horizontal surface (OHS) in side clearance zone (SCZ) are put forward. Furthermore, obstruction requirement when aircraft are placed on apron of the near highway sections is considered, then the corresponding steps of evaluation are proposed. The procedural design of highway runway clearance condition evaluation is realized by means of software to program. The superelevation condition of the obstacle in the clearance of the highway runway is calculated and analyzed by actual examples. All these have provided a theoretical basis for exactly determining the position, altitude and the superelevation value of the obstacle in the highway runway clearance zone.     

Characteristics of gaseous and particulate pollutants exhaust from logistics transportation vehicle on real-world conditions

On-road vehicle tests of three heavy duty diesel trucks were conducted by a portable emission measurement system (PEMS) in Chengdu, China. SEMTECH-ECOSTAR provided by Sensors Inc. was employed to detect gaseous emissions and MI2, an emissions measuring instrument powered by the Pegasor Particulate Sensor (PPS) was used to detect particulate emissions during the tests. The impacts of speed, acceleration and engine load on emissions were analyzed. The average nitrogen oxides (NOx) emission factors of the heavy duty diesel truck (HDDT), medium-duty diesel truck (MDDT), light duty diesel truck (LDDT) were 7.29, 5.29 and 5.53 g/km. The particulate emission factors were 0.60, 0.30 and 0.14 g/km respectively, higher than the similar reported in the previous studies. Both gaseous and particulate emission exhibit significant correlations with the change in vehicle speed, acceleration and power demand. The highest emission was generally in high VSPs and higher loads. High engine load caused by aggressive driving was the main factor of high emissions for the vehicles on real-world conditions.     

不同土壤条件下水平板对平面铲刀工作阻力的影响

在砂土和级配土确定的3种土壤条件下,给定90°和60°2种作业倾角,选择作业深度为90 mm,以水平板长度(0,30和60 mm)不同的L型铲刀为作业工具开展土壤推运试验,并对相同土壤条件和相同作业倾角下的试验结果进行对比分析。研究结果表明:L型铲刀在一定作业条件下可以有效改善推运工作阻力,但土壤条件是影响L型铲刀改善工作阻力的前提,即土壤抗剪强度较大时,L型铲刀对工作阻力的有益影响更为显著;当土壤条件相同时,L型铲刀对工作阻力的有益影响程度与作业倾角关系密切;当土壤条件和作业倾角都确定时,L型铲刀对工作阻力的有益影响程度与水平板长度有关,且该水平板长度存在一个最优值使L型铲刀在相同作业条件下的工作阻力最小。     

转向架撒砂装置随机振动疲劳分析与状态监测研究

转向架撒砂装置在服役过程中承受来自轮轨的随机振动激扰,其与轴箱体螺纹连接的部位可能出现松脱甚至断裂。文章一方面通过结合模态计算与模态试验对标研究,校验有限元模型,获得模态参数,并综合随机响应分析和疲劳应力评估的Dirlik模型,研究基于模态分析的随机振动疲劳分析方法;另一方面,为增加撒砂装置服役安全,研究了一种基于光纤光栅的状态监测技术,并在台架试验上进行了验证,在设计上保障了撒砂装置的服役安全。