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排序方式: 共有264条查询结果,搜索用时 15 毫秒
1.
桥梁结构的动力特性(振型、频率和阻尼)是桥梁承载力评定的重要参数,同时也是识别桥梁结构工作性能和桥梁抗震分析的重要参数,本文通过昆明东风路立交桥的动载试验,分析桥梁在不同工况下动应变、动挠度、频率和阻尼以及影响实测冲击系数的原因。对全面地评价桥梁结构有重要意义。 相似文献
2.
This paper presents the design and results for field tests regarding the environmental benefits in stop-and-go traffic of an algorithmic green driving strategy based on inter-vehicle communication (IVC), which was proposed in Yang and Jin (2014). The green driving strategy dynamically calculates advisory speed limits for vehicles equipped with IVC devices so as to smooth their speed profiles and reduce their emissions and fuel consumption. For the field tests, we develop a smartphone-based IVC system, in which vehicles’ speeds and locations are collected by GPS and accelerometer sensors embedded in smartphones, and communications among vehicles are enabled by specially designed smartphone applications, a central server, and 4G cellular networks. Six field tests are carried out on an uninterrupted ring road under slow or fast stop-and-go traffic conditions. We compare the performances of three alternatives: no green driving, heuristic green driving, and the IVC-based algorithmic green driving. Results show that heuristic green driving has better smoothing and environmental effects than no green driving, but the IVC-based algorithmic green driving outperforms both. In the future, we are interested in field tests under more realistic traffic conditions. 相似文献
3.
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. 相似文献
4.
结合工程实例,分析了连续刚构组合体系桥梁在活载作用下的静动力响应,所得结论对同类桥梁的建设及运营管理具有参考价值。 相似文献
5.
Characteristics of the built environment (BE) have been associated with walk, transit, and bicycle travel. These BE characteristics can be used by transportation researchers to oversample households from areas where walk, transit, or bicycle travel is more likely, resulting in more observations of these uncommon travel behaviors. Little guidance, however, is available on the effectiveness of such built environment oversampling strategies. This article presents measures that can be used to assess the effectiveness of BE oversampling strategies and inform future efforts to oversample households with uncommon travel behaviors. The measures are sensitivity and specificity, positive likelihood ratio (LR+), and positive predictive value (PPV). To illustrate these measures, they were calculated for 10 BE-defined oversampling strata applied post-hoc to a Seattle area household travel survey. Strata with an average block size of <10 acres within a ¼ mile of household residences held the single greatest potential for oversampling households that walk, use transit, and/or bicycle. 相似文献
6.
7.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(4):305-325
This paper presents the results of an experimental and numerical investigation on the derailment of a railway wheelset with solid axle. Tests were carried out under quasi-steady-state conditions, on a full-scale roller rig, and allowed to point out the effect of different parameters like the wheelset's angle of attack and the ratio between the vertical loads acting on the flanging and non-flanging wheels. On the basis of the test results, some existing derailment criteria are analysed in this paper and two new criteria are proposed. A model of wheel–rail contact is proposed for the mathematical modelling of the flange climb process, and numerical vs. experimental comparisons are used to obtain model validation. 相似文献
8.
Alexander H. Day David Clelland Lawrence J. Doctors 《Journal of Marine Science and Technology》2009,14(3):387-397
This paper covers an extension of the study of Doctors et al. (J Ship Res 52(4):263–273, 2008) on oscillations in wave resistance during the constant-velocity phase of a towing-tank resistance test on a ship model to
the case of relatively shallow water. We demonstrate here that the unsteady effects are very prominent and that it is essentially
impossible to achieve a steady-state resistance curve in a towing tank of typical proportions for a water-depth-to-model-length
ratio of 0.25. This statement is particularly true in the speed region near a depth Froude number of unity. However, on the
positive side, we show here that an application of unsteady linearized wave-resistance theory provides an excellent prediction
of the measured total resistance, when one accounts for the form factor in the usual manner. Finally, a simple application
of the results to the planning and analysis of towing-tank tests is presented. 相似文献
9.
Jungyong Wang Ayhan Akinturk Neil Bose Stephen J. Jones Yun Young Song Ho Hwan Chun Moon Chan Kim 《Journal of Marine Science and Technology》2008,13(3):244-255
The objective of this study was to investigate the performance of a model azimuthing podded propulsor in ice-covered water.
Model tests were carried out with two different depths of cut into the ice (15 and 35 mm), two different ice conditions (presawn
and pack ice conditions), and four different azimuthing angles. The depth of cut is the maximum penetration depth of the propeller
blade into the ice block. The 0.3-m-diameter model propeller was operated in a continuous ice milling condition. Ice loads
were measured by several sensors which were installed in various positions on the model. Six one-axis pancake-style load cells
on the top of the model measured the global loads and two six-component dynamometers were installed on the shaft to measure
the shaft loads. One six-component dynamometer was attached to the one of the propeller blades inside the hub to measure the
blade loads. The pod unit and propeller performance in ice are presented. Ice-related loads, which were obtained when the
blade was inside the ice block, are introduced and discussed. During the propeller–ice interaction, a blade can experience
the path generated by the previous blade, which is called the shadowing effect. The effects of shadowing, depth of cut, azimuthing
angle, and advance coefficient on propulsor performance are presented and discussed. 相似文献
10.
Modelling navigation in muddy areas through captive model tests 总被引:2,自引:2,他引:0
Guillaume Delefortrie Marc Vantorre Katrien Eloot 《Journal of Marine Science and Technology》2005,10(4):188-202
Many access channels and harbours suffer from sedimentation and formation of mud layers. To keep navigation safe and economic,
extensive maintenance dredging is needed. Until now, the required level of dredging has always been determined by making use
of the physical characteristics of the mud layer, which does not necessarily result in efficient dredging. Ship behaviour
also matters, and knowledge of ship manoeuvrability can help to redefine the level of dredging required. A mathematical model
of manoeuvring for simulation purposes, based on a comprehensive series of captive model tests, is presented, along with a
selection of results. 相似文献