R/S分析法在盾构下穿机场过程中的地表变形规律研究

为保证机场的正常运营,在盾构下穿机场的施工过程中,对地表沉降变形控制的要求较高,因此对穿越过程中的施工控制和变形规律研究具有重要意义。首先,基于盾构下穿机场的工程条件,分析盾构下穿过程中的风险,并提出相应的控制措施;同时,根据现场监测数据,分析盾构下穿机场过程中的地表沉降变形规律,并利用R/S分析法对地表沉降的发展趋势进行研究。结果表明:盾构施工引起的机场地表变形均在控制值范围以内,且各监测点在不同序列条件下的Hurst指数均大于0.5,具有沉降持续减弱的趋势,验证下穿过程中风险控制措施的有效性,为类似下穿机场的盾构施工提供一定的实践经验,也为盾构施工引起的地表沉降变形规律研究提供参考。     

船舶低硫柴油系统设计的分析与优化

就新辟航线首制船“汉亚直达”集装箱船的低硫柴油系统,叙述了船舶低硫柴油系统的设计经验,从当前国内外对船用燃油硫含量的要求、应对方案到船舶低硫柴油冷却方式选择、低硫柴油冷却系统设计、高/低硫柴油转换、使用低硫柴油风险分析及处理等方面进行详细叙述,为业内同行提供参考。     

Tyre/road noise damping characteristics using nomographs and fundamental vibroacoustical relationships

Several studies have successfully developed laboratory and field measurement techniques to estimate tyre/road noise damping characteristics. However, laboratory–field noise correlations of pavement types in the form of nomographs is essential to cognize the pavements’ acoustical properties from a practical perspective. A toolkit that readily provides field tyre/road noise intensity of different pavement materials is needed. Thus, the main objective of this study was to develop nomographs with relationships for tyre/road noise versus pavement materials’ viscoelastic–vibroacoustical properties. Isothermal and isochronal nomographs of phase angle–tyre/road noise as toolkits were developed based upon well-established phase angle and noise intensities typical of mixtures, making the nomograph correlations very authentic, realistic, and novel along with benefit to predict tyre/road noise at any desired temperature and traffic speed (or frequency) combination. This study is envisaged to benefit in the discernment of road materials’ damping capabilities from vibroacoustical and field noise–viscoelastic relation aspects.     

船舶推进同步电机PTI/PTO模式研究

PTI/PTO推进是最近发展起来的一种新型船舶推进方式,兼具传统柴油机推进和电力推进优点,可实现多种船舶工作模式,具有操控性好、安全、经济等特点,将是未来船舶推进方式发展方向之一.本文介绍了PTI/PTO推进模式理论和工作模式,便于理解该推进方式,希望有助于船舶推进技术的发展.     

Centrifuge modelling of pipe-soil interaction in clay with crust layer

Seabed in regions, such as the Gulf of Guinea and North West Shelf of Australia, may exhibit a crust layer where the undrained shear strength can be an order of magnitude higher than that of the immediately underlying sediment. This can complicate design of steel catenary risers, where fatigue depends on the cyclic vertical stiffness of the pipe-soil interaction. Potential punch-through of the riser into the underlying soft soil may invalidate design assumptions based on the pipe-soil stiffness within the crust layer. The long-term evolution of pipe-soil stiffness within the crust layer, which exhibits similar properties to an over-consolidated soil, is also poorly understood. This paper describes centrifuge model tests undertaken in a clay sample with a crust layer, simulating the punch-through process of a pipe under load control and investigating the pipe-soil stiffness during long-term cyclic loading tests under displacement control. Results confirm that the potential for punching-through the crust layer depends strongly on the relative ratio of pipe diameter to crust layer thickness. The long-term evolution of pipe-soil stiffness showed a steady increase after an initial remoulding stage in contractile soils (normally consolidated and lightly over-consolidated), but a steady reduction in the heavily over-consolidated, more dilatant, crust. The magnitude of pipe-soil stiffness changes (during both remoulding and reconsolidation) is governed by the over-consolidation ratio of the soil and the amplitude of the cyclic displacements. This study provides insights on the relevant cyclic stiffness to consider when assessing SCR fatigue life in over-consolidated soils and soils exhibiting a superficial crust layer.     

STAAD/CHINA在搭架设计及强度校核中的应用

搭架作业是船舶修造日常工作中比较普通、常见的工程,合理、快速地设计和校验脚手架的强度,直接影响生产施工的安全性、经济性和效率。文章介绍了如何使用有限元软件STAAD/CHINA对搭架方案进行建模计算及校验,计算结果接近实际,提高了强度校验的效率。     

Assessment of fatigue strength of steel butt-welded joints in as-welded condition – Alternative approaches for curve fitting and mean stress effect analysis

Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading (secondary bending included) were analyzed using the nominal stress system and the notch stress system. Two approaches were used; a standard fitting procedure and minimization of the sum of squared perpendicular distances from a line with a fixed and free slope. In all cases, the latter method gave better agreement between the experimental and predicted fatigue life and fatigue strength. The analyses showed both with all broken specimen data included and with reduced data that the FAT225 curve, as recommended by IIW, might be too optimistic for the notch stress approach in the case of butt-welded joints in as-welded condition. It was also found that use of the local stress ratio instead of the applied stress ratio might explain many issues concerning current observations and apparent inconsistencies in reported literature.     

Dynamic demand estimation and prediction for traffic urban networks adopting new data sources

Nowadays, new mobility information can be derived from advanced traffic surveillance systems that collect updated traffic measurements, both in fixed locations and over specific corridors or paths. Such recent technological developments point to challenging and promising opportunities that academics and practitioners have only partially explored so far.The paper looks at some of these opportunities within the Dynamic Demand Estimation problem (DDEP). At first, data heterogeneity, accounting for different sets of data providing a wide spatial coverage, has been investigated for the benefit of off-line demand estimation. In an attempt to mimic the current urban networks monitoring, examples of complex real case applications are being reported where route travel times and route choice probabilities from probe vehicles are exploited together with common link traffic measurements.Subsequently, on-line detection of non-recurrent conditions is being recorded, adopting a sequential approach based on an extension of the Kalman Filter theory called Local Ensemble Transformed Kalman Filter (LETKF).Both the off-line and the on-line investigations adopt a simulation approach capable of capturing the highly nonlinear dependence between the travel demand and the traffic measurements through the use of dynamic traffic assignment models. Consequently, the possibility of using collected traffic information is enhanced, thus overcoming most of the limitations of current DDEP approaches found in the literature.     

混凝土在路桥桩基施工中的作用及技术

路桥桩基混凝土施工中，为了保障灌注桩混凝土的质量，必须加强对准备工作及施工工艺的重视。通过对混凝土及其施工质量要求进行分析，探讨了混凝土在路桥桩基施工中的配合比、泵送等，并阐述了路桥桩基施工技术。