考虑制动力影响的大型客车舒适性分析

利用有限元法和动力平衡原理,建立了具有层间接触的沥青路面和13个自由度的大型客车人体三维模型。以不平顺作为激励,随机模拟车流分布,在不同制动情况下,从时域和频域两方面分析人-车-路耦合振动下车辆和人体的动力响应。时域分析采用客观评价标准和主观烦恼率相结合的方法,频域分析考虑人体共振、人的心理和生理因素。结果表明:随着制动力增大,人体的竖向加速度幅值不变,俯仰、侧倾加速度幅值都增大,但是俯仰加速度增幅远大于侧倾加速度的情况,人的舒适性变差,烦恼率增高;在紧急制动时,主频段对人体共振、心理和生理产生的影响很小,但是次主频段与人体某些器官固有频段重合,对人体共振、心理和生理产生的影响是不容忽视的。     

飞机－道面－土基动力耦合系统有限元分析

本文将飞机－道面－土基作为一个相互作用的动力系统，对飞机滑行情况下，弹性半空间地基上刚性道面板的动响应，采用有限元法进行了计算分析。结果表明，本文计算结果与现场实测值吻合很好。由于考虑了飞机和道面之间的耦合作用，避免了实测飞机对道面作用荷载的繁琐工作，因此本文方法具有明显的实用意义。     

Elastodynamic analysis of a thin layer bonded on a visco-elastic medium under combined in-plane and lateral pulse loads

An analytic solution of a thin layer bonded on a visco-elastic medium under the action of in-plane and lateral pulse loads is presented. The analysis is based on double integral transforms with respect to space and time. Representative examples are studied and discussed to determine the influence of the (a) damping and elastic coefficients of visco-elastic medium, and (b) in-plane compression and stretching of the thin layer on wave propagation.     

基于动量原理的大坡度沥青路面动水压力计算及影响因素分析Calculation and influence factors analysis for hydrodynamic pressure of asphalt pavement with large slope based on momentum theorem

在多雨地区长大纵坡沥青路面是雨天事故多发区域。应用动量定理,建立了沥青路面动水压力的力学计算模型,并系统分析了车辆荷载、行车速度和道路纵坡对动水压力的影响。结果表明,当水膜厚度＜3 mm时,动水压力随车速及车辆荷载的增大而增大,上坡时,动水压力随着纵坡坡度的增大而增大,下坡时,动水压力随着纵坡坡度的增大而减小。当水膜厚度＞3 mm时,动水压力随车速、车辆荷载增大而增大,上坡时,动水压力随着纵坡坡度的增大而增大,下坡时,动水压力随着纵坡坡度的增大呈先缓慢增加然后又缓慢减小的变化趋势;无论是上坡还是下坡,动水压力都随着车轮半径的增大而增大。本研究成果为多雨地区长大纵坡沥青路面重载交通高速行车易发生交通事故提供了理论分析依据。     

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基于结构动力学基本理论,系统地分析了路面材料阻尼系数的求解方法,以 及材料阻尼效应对路表动态弯沉的影响规律. 结果表明：利用第1,第2主振型的固有频率 计算阻尼系数的方法,能克服传统简化计算阻尼系数而带来的结果偏差;黏性阻尼系数几乎 对路表弯沉时程变化没有影响;土基阻尼效应是影响路表动态弯沉时程变化的关键因素,而 其它层材料的阻尼特征影响甚微. 研究结果为进行路面结构动力学分析时,材料阻尼参数的 计算以及合理取值提供了理论与实践依据.     

Research on nonlinear constitutive relationship of permanent deformation in asphalt pavements

To predict correctly the rut depths in asphalt pavements, a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pavements is presented. The model combines a generalized Maxwell model with an elastoplastic one. Then from the creep theory, the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement, the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP, and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model, which is presented in this paper for the rutting of the asphalt pavement, is effective. The properties, such as nonlinear elasticity, plasticity, viscoelasticity and nonlinear viscoelasticity, which affect the rutting of an asphalt pavement, can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.     

Traffic noise reduction due to the porous road surface

Porous road surfaces reduce road traffic noise. A new method of noise reduction assessment is proposed. The noise generated by a few vehicles was measured two times: on an old surface with the dense asphalt and on a new surface with the porous asphalt. Subjective assessments of drive-by noise suggest that the sound exposure and the road surface coefficient can be used as the acoustical characteristics of a road surface. Their average values, with the average number of vehicles passing the receiver during a day or night, makes it possible to predict the equivalent continuous A-weighted sound pressure level for the new road surface. This is the main objective of this paper.     

An application of vertex packing to data analysis in the evaluation of pavement deterioration

The analysis of data concerning the deterioration of pavement over time yielded a problem of aggregating the data in a manner that preserved independence of the aggregated data points and maximized the number of points. We show that this problem can be modeled as a maximum cardinality vertex packing problem on a proper internal graph and thus can be solved very efficiently by a greedy algorithm.     

Considerations for building knowledge-based expert systems in highway maintenance planning

Genuine, nontrivial planning problems in pavement and bridge maintenance are generally beyond the capabilities of expert systems. However, the diagnostic, interpretive and predictive features of such systems can be combined with algorithmic planning tools to produce comprehensive maintenance planning and management systems.After a discussion of the relevant issues, this paper addresses the potential application areas for knowledgebased expert systems in highway maintenance planning. The foxus is on how and where expert systems can interface with optimization models to yield meaningful results.     

现场实测结构温度对半刚性沥青路面性能的影响

针对中国特色的半刚性基层沥青路面,在广韶高速公路瓮城段进行为期一个月高温期的现场温度观测。运用三维有限元方法,结合现场实测温度,分析了半刚性沥青路面结构的最大拉应力、最大剪应力和最大路表弯沉在荷载和荷载耦合作用下的变化情况。结果表明,随着路面深度增加,温度波动的幅度逐渐减小;路面内的最高温度相对大气和路表温度滞后约1小时;沥青路面内部温度高于表面温度;大气、路表和路面内部温度变化基本同步,温度波峰与波谷的出现频率相同;在温度和荷载综合作用下,路表以下2cm深度范围内易出现因拉应力不足造成的开裂破坏;路表以下10cm深度范围内,较易出现剪切破坏;高温温度场的存在虽不会明显增大路面结构各层的拉应力与剪应力,但会明显增大路表弯沉,故易产生车辙破坏。