In order to study the strength forming mechanism and influencing factors of half-warm mix asphalt (HWMA), the stability of Marshall samples is tested under different test conditions such as gradations, asphalt quantities, forming methods, number of compaction passes, maintenance period, and forms of maintenance. The results show that (1) the suspension dense gradation is satisfactory for early strength of HWMA, and its strength varies with asphalt quantity; (2) the number of compaction passes and maintenance period are two major external factors influencing strength forming, and the increase in strength reduces significantly when the number of compaction passes on both sides increases above 130. (The Marshall samples acquire final strength in 49 days of maintenance.); and (3) both loading and maintenance time significantly affect the strength forming process. Moreover, the cohesion of the material and internal friction increase, and the Marshall samples gain strength more rapidly with both the factors. Loading and maintenance time affect the internal friction and cohesion of the material, respectively. The results of this study provide guidance for design and construction of HWMA.
为了评估无粘性土路基强夯加固效果,结合现场试验成果,采用FLAC3D有限差分软件进行了数值模拟,重点针对夯击能2 000 kN·m时动应力衰减规律进行了对比分析。研究结果表明:强夯对无黏性土路基填料的加固效果明显,强夯竖向影响深度大于径向影响范围,径向动应力衰减速度较竖向要快;针对该类填料得出有效加固深度约6.0 m,径向加固宽度约6.04 m,以及强夯加固Menard公式修正系数α值。同时,还研究了强夯设计参数(锤重、落距、锤径等)对强夯加固效果的影响,并对相同夯击能下,几种不同锤重-落距组合形式的加固效果进行了探讨,得出夯锤重量及落距是影响加固无粘性土效果的主要因素,而夯锤面积、夯锤-落距组合形式仅影响表层约3 m内土体加固效果。
Compared with flat slope sections of asphalt pavement, the loading time of low-speed vehicle load to uphill sections with long and large longitudinal slope is much longer, under the comprehensive combination of heavy load and high temperature. Developing and forming speed of rutting on uphill sections with long and large longitudinal slope is faster. Rutting factor and dynamic modulus of asphalt and asphalt mixture under different loading time will be calculated and analyzed in this paper. The results show that rutting factor and dynamic modulus were substantially reduced. Using the new rutting test equipments with the changing wheel speed and load to simulate the influences of overload and temperature (loading time) on asphalt mixture, the results show that dynamic stability is rapidly declined with the decrease of wheel speed. The loading time has vital influence on the high temperature stability of asphalt mixture. Increasing load time is equivalent to raising the experimental temperature, and using the temperature conditions in specification to verify the high temperature stability of asphalt mixture for uphill sections with long and large longitudinal slope is unreasonable.
为了科学、合理地提高南方湿热多雨地区公路雨季施工建设效率,针对南方湿热多雨地区因长期持续降雨严重延缓公路路基施工进度,确定了路基施工受降雨气候影响最关键工序-填料翻晒。按照填料翻晒所需气候条件,结合降雨规律提出了路基择时施工方法新理念。运用回归分析建立了路基择时施工时段与对应频率之间的相关关系,从而推导了路基择时施工时段的分布规律和概率计算公式,并运用假设检验方法验证了合理性及适用性。通过现场翻晒试验,计算和对比分析多雨地区5种典型路基填料可施工时段相应频数及可行概率,从择时施工可行概率的角度提出了适用于多雨地区路基填料分级新方法。结合工程实例,运用路基择时施工分布规律对路基填筑整个施工组织过程进行了优化,论证其可靠性及实现性。
掌握红砂岩填料路基动态模量的现场变化规律,通过现场便携式落锤式弯沉仪(PFWD)试验、室内粉晶X射线衍射(XRD)试验和现场压实度试验,分析了不同黏土矿物含量、含水率和压实度对红砂岩填料路基动弹性弹模量的影响。结合现场检测数据,建立了动态模量随压实度和含水率变化以及动态模量随黏土矿物含量、含水率和压实度变化的试验回归模型。研究表明:现场的红砂岩填料路基动态模量与压实度具有良好的正相关回归关系。成型路基的含水率普遍比施工时高。红砂岩填料路基的动态模量随含水率增大而减小,二者具有良好的回归关系。XRD试验显示:动态模量随黏土矿物含量的增大而减小,二者也具有良好的回归关系。此外,不但动态模量与压实度、稠度这2个指标具有良好的回归关系,而且动态模量与压实度、稠度、黏土矿物含量3个指标也均具有良好的回归关系。
To investigate the moisture equilibrium of expansive soil embankments, a series of stress-dependent soil-water characteristic curve (SWCC) tests, one-year field monitoring on a trial covered expansive soil embankment, and numerical simulations of the process of moisture equilibrium of a covered expansive soil embankment under atmospheric effects over a period of ten years are conducted. The results show that (1) The effect of the stress state on the equilibrium moisture of expansive soil is clearly in the suction range of 0-3 MPa;(2) In the first year of service, the moisture content of the core of an expansive soil embankment increases gradually, the extent of moisture content fluctuation increases with increasing proximity to the slope side, and the differential settlement of the embankment is observed; (3) The moisture content of the core reaches a steady state, i.e., the moisture equilibrium state, on the sixth year of service; (4) The optimum moisture content of an expansive soil compacted in accordance with wet heavy compaction standard is close to the equilibrium moisture content, and it is better to use this standard to control field compaction of an expansive soil embankment in moist and hot areas in southern China.
为研究循环荷载作用下风积土累积塑性变形特性,以哈大高铁苏家屯试验段风积土为研究对象,通过一系列固结不排水动三轴试验,研究不同含水率、振动频率、压实系数的土样在不同动应力水平下的累积塑性变形规律。试验结果表明循环荷载作用下,风积土的εp-lg N曲线呈稳定型、破坏型和临界型3种类型。极差分析结果表明动应力幅值σdmax是影响风积土累积塑性应变εP的最重要因素,其次为含水率ω和压实系数kc,振动频率f对εP几乎无影响。基于动三轴试验结果和已往模型研究,提出了改进的Monismith数学模型,建立了模型参数a和b与上述4个因素之间的多元线性回归公式。利用所建模型计算了不同工况时风积土的εp-lg N曲线,其值与试验结果吻合较好,验证了模型的有效性。
This study presents a test method to evaluate the durability of the anti-skid performance of asphalt concrete. In this work, the influence of mixture gradation, asphalt-aggregate ratio, and temperature on the texture depth is discussed for the asphalt mixture that is commonly used forth in overlays. This mixture has a nominal maximum particle size of 9.5 mm. The durability test method is used to realize the deterioration of texture depth at different wheel load times, light intensities, and water-aging damages. Experimental results show that the test method can effectively evaluate the difference in texture depths between different gradations. Texture depth is found to increase with increasing coarse aggregate content but decrease with increasing asphalt-aggregate ratio and testing temperature. Meanwhile, the residual ratio of texture depth varies with changing laws and under different aging conditions and wheel load times.
为研究标准马歇尔击实成型方法和旋转压实成型方法对沥青混合料空隙分布的影响规律,在实验室分别采用SYM-457自控马歇尔击实仪和HTHY-XY150旋转压实仪制作SMA-13和AC-10的沥青混合料试件,并对上述2种沥青混合料路面进行现场取芯;将上述试件按3 mm间隔进行CT扫描,然后用Matlab对图像进行处理,采用统计学方法计算其空隙参数,分析在2种压实方法下不同混合料类型的沥青混合料空隙数量、空隙率、空隙等效直径的变化规律,并将室内2种成型方法的试件与现场取芯试件进行对比。结果表明:相对于标准马歇尔击实成型方法,采用旋转压实成型方法获得的沥青混合料试件均匀性较好,且与现场取芯试件的空隙参数更接近,与工程实际情况更相符。
Taking Edong Yangtze River Bridge as the research subject, the influence of error of unstressed cable length on the geometric shape and internal force of super-span hybrid girder cable-stayed bridge during completion is studied on the basis of the geometry control method with full consideration of the structural nonlinear geometrical effect. Moreover, the mechanical behaviors of the center and side spans of the bridge and their control strategies are discussed. The analysis shows that structural differences between the center and side spans exerted an influence on the geometric shape and internal force. The influence of unstressed cable length error on the geometric shape in the center span of the completed bridge is greater than that of the side span, whereas the impact on internal force in the side span is greater than that in the center span. The mechanical behavior is relatively independent between span types. In addition, the percentage change of the girder stress reaches the maximum level in the steel/concrete composite segment, in which the mechanical behavior is highly complicated. Therefore, its design and construction require close attention. Moreover, the difference in stiffness between the center and side spans has a remarkable impact on cable force redistribution in the completion stage, and the changes in cable force differ between the span types.
为了研究不同矿料级配对温拌橡胶沥青混合料性能的影响规律,通过对SMA中各粒径集料含量进行调整,选择5种具有代表性级配对比AC级配进行大量室内试验,分析不同级配对温拌橡胶沥青混合料体积指标及路用性能影响。试验结果表明,达到相同性能指标时,温拌橡胶沥青混合料击实温度较热拌橡胶沥青混合料可降低30℃左右,不同级配混合料对马歇尔体积指标有较大的影响。为满足形成SMA结构条件,要求关键筛孔通过率不能超过28.2%,采用SMA间断级配温拌橡胶沥青混合料较AC连续级配具有更好的高、低温稳定性能和水稳定性能,并且在SMA结构类型中适当增加粗集料含量对混合料性能有较大的改善。建议选择较粗间断级配作为温拌橡胶沥青混合料设计级配。
Application of nonlinear behavior laws is relatively complicated and difficult to master because of the unique configurations of special-shaped arch bridges. In this study, a self-compiled program is used to analyze the nonlinear behavior laws of five special-shaped arch bridges with distinct characteristics. Essentially, the beam-column effect is determined to be the most influential factor for arch-beam composite butterfly-shaped arch bridges, the large displacement effect has the greatest influence for flying swallow-type tied arch bridges, and the cable sag effect is the main factor for arch-tower cable-stayed bridges. For thrust crescent-shaped arch bridges, however, the influence of all nonlinear factors is rather little and can be neglected. In addition, the cable sag effect of inclined cables is more noticeable than that of vertical cables, and all nonlinear factors significantly influence the cable forces. Therefore, the cable sag effect should be considered, and the tension of inclined cables must be calculated by nonlinear methods. Moreover, because the deck slabs and crossbeams only carry load sand are not subject to force as a part of the entire structure, the nonlinear influence on their inner forces is negligible.Therefore, linear methods are appropriate; however, the large displacement effect should be considered when the displacement is calculated.
玻璃沥青混凝土路面是一种环保绿色路面,本文试验研究分析了玻璃沥青混凝土的反光性能评价方法和路用性能(高温稳定性、低温抗裂性和水稳定性)。认为应以定量评价作为主要评价方法,进行了室内反光性能评价,开发了新的路面材料反光性能测试装置。随着玻璃掺量的增大,玻璃沥青混凝土反光性能越好,路用性能以15%玻璃掺量为拐点,在少于等于15%玻璃掺量时,与普通沥青混凝土差别不大,满足道路使用要求。综合路用性能与反光性能这2个方面,给出了玻璃沥青混凝土推荐配合比:沥青含量4.2%,15%玻璃掺量替代集料,消石灰用量2%。
Equi-amplitude fatigue loading experiments on five reinforced concrete T-beams were conducted to observe the fatigue damage development. Three stages of fatigue damage were seen in the experiments. The damage rapidly developed early and late periods of the experiment but was relatively stable in between. The beam failed because of the brittle failure of the steel bars. The number of cracks, and the width and height also follow three stages: rapid development, stable development, and failure. The growth of almost all of the cracks stopped at the time of beam failure, except one or two main cracks that continued to grow. The deflection of the test beam and strain of the steel bars and concrete increased rapidly early in the fatigue cycles, with increasing fatigue cycles, whereas they were relatively stable in the middle stage but increased rapidly near the failure point. Finally, the S-N curve of the reinforced concrete T-beam was obtained.
从工程稳定逆可靠度设计思路出发,解析了基于一次逆可靠度的工程结构稳定性分析程序;将该分析程序与常用的边坡稳定毕肖普法分析模式相融合,推导出基于逆可靠度的边坡稳定安全系数及相关参数计算公式,构造出基于逆可靠度的边坡稳定分析方法,利用该方法求解出的边坡稳定安全系数既可以考虑边坡参数不确定性对其的影响,又能满足边坡设计的目标可靠度水平;最后通过工程实例,阐述该方法的具体实施过程,分析了相关因素对边坡稳定的影响程度,并论证该方法的合理性与可行性。
By establishing a finite element (FE) model of reinforced concrete (RC) columns strengthened with steel wire mesh, the mechanical properties under low-cyclic loading are analyzed, and the correctness of the FE model is verified. Hysteretic curves, skeleton curves, strain curves, and changes in stiffness and ductility of the strengthened RC columns under various strengthening conditions are calculated in this study by using the FE model to examine the effects of axial compression ratio, longitudinal reinforcement ratio, concrete strength, steel wire quantity, and eccentric compression on the seismic behavior of the strengthened columns. The results show that an increase in axial compression ratio results in an improvement in the ultimate bearing capacity of the strengthened columns by 9%-17% and a reduction in ductility by 9%-15%. In addition, increases in the stirrup ratio, longitudinal reinforcement ratio, concrete strength, and steel wire quantity result in improvement in ultimate bearing capacity, and ductility of the strengthened columns can be improved by 2%-28%. Moreover, an increase in vertical pressure results in rapid development of eccentric, stirrup, and steel wire strains in the strengthened columns, which causes reductions in ultimate bearing capacity in the columns by 2%-13%, energy consumption by 35%, and additional reductions in stiffness and ductility.
针对Mononobe-Okabe理论的不足,从滑动楔体处于极限状态时力的平衡条件出发,结合拟静力法与闭合力矢量多边形法,推导了考虑滑裂面上填土的黏聚力、墙土间黏着力、均布超载、填土开裂及地震荷载作用等条件下的黏性土主被动土压力计算式,并通过图解法给出了临界破裂角的显式解答。在相应简化条件下Mononobe-Okabe理论计算式为该公式的特例。研究表明:不考虑地震荷载对均布超载的影响,得到主动土压力偏小而被动土压力偏大;地震条件下的主动与被动土压力随水平地震系数的递增分别增大与减小,随竖向地震系数递增均减小;当水平地震系数取值较大时,将出现随竖向地震系数递增主动土压力先减小后增大的特殊情况。
A numerical method is proposed to study load and the environment couple effect during the service of a concrete bridge. By studying the corrosion process of reinforcement bars, the strain of the bars is decomposed into two parts, elastic strain and corrosion strain, and their ratio is defined as the corrosion factor. The time-dependent constitution of corrosion of the steel bar is obtained by introducing a nominal elastic module. According to the virtual work principle, the finite element formulation of the reinforcement concrete element is derived, and the computation sequence determined using the time history method is illustrated. The nonlinear finite element program is realized by the Fortran program to numerically solve the problem, which is verified by testing a model of three reinforced concrete beams. The results show that both stiffness matrix and the additional nodal load of the reinforcement concrete element should be considered in the couple effect analysis. The proposed method can be used to predict long-term mechanical properties of concrete bridges.
为研究高速公路桥梁的实际车辆疲劳荷载谱,选取了京沪高速(G2)沂淮段新沂河大桥,基于动态称重系统(WIM)的监测信息,统计分析京沪高速沂淮段通行车辆的车重、车间距、轴重等特征参数;依据每月所得车辆数据,基于Miner线性积伤率和等效疲劳损伤原理,建立了新沂河大桥包含9类代表车型的实际运行车辆疲劳荷载谱,并对其疲劳损伤贡献值进行了研究。结果表明:各车道车重服从典型的三峰分布规律,车间距服从Weibull分布;六轴2类代表车,第1、2轴重服从典型Gauss分布,而第3~6轴重服从混合Gauss分布;车辆疲劳荷载谱值与疲劳损伤贡献值都以六轴2类车最大,其次为六轴车1类,可知该高速公路上以六轴重车为主,同时,对于疲劳损伤的贡献,六轴车占90%以上。
To study the effect of shear lag on a composite girder with steel truss webs, a three-dimensional finite element (FE) model, using the ANSYS FE software, and a corresponding FE model of composite girder with corrugated steel webs is established to perform a comparative analysis. The shear lag effect and distribution of shear lag coefficients along the cross section of the composite girder with steel truss webs are investigated under concentrated and uniform loads. The results show that (1) under concentrated and uniform loads, the shear lag effect is evident on the top and bottom plates of the composite girder with steel truss webs; (2) for the composite girder with steel truss webs, the shear lag effect is more pronounced under concentrated loads than under uniform loads; (3) under the same load, the normal stresses of the top and bottom plates of the composite girder with steel truss webs are less than those of composite girder with corrugated steel webs; and (4) the shear lag coefficient distributions of the top and bottom plates along the cross section are almost similar for the two types of composite girders.
以某斜拉桥为试验对象,介绍了预应力混凝土斜拉桥承载力的评定方法。通过静载和动载试验,获得了桥梁控制截面的应变、挠度等随加载变化的情况;通过理论值与试验值的对比分析,对桥梁的承载能力和安全性能进行了研究,以检验桥梁结构在试验荷载作用下的实际受力状况是否满足设计及规范要求。结果表明:各测点应变、挠度、索塔偏位和索力测试校验系数均满足规范关于校验系数的规定;桥梁结构的实际刚度能满足公路Ⅰ级荷载使用要求,且有一定的安全储备;试验结构实测残余挠度均不大于20%,表明结构在试验荷载作用下尚处于弹性工作状态;以动载试验和测量数据建立的模型分析可知桥梁振动正常,实测结构阻尼反映其阻尼系数较小,说明桥梁结构振动衰减正常,无明显结构损伤缺陷,试验桥梁符合规范要求。
Based on the LS-DYNA program, a vehicle's wheel is simulated by linear elastic material rubber and steel, and internal pressure in all tires is defined. Rotation of vehicle wheel 3D models is simulated through appropriate rotation and cylinder-shape constraints. The dynamic characteristics of the vehicle suspension system are simulated by using spring damper elements combined with dynamic characteristics of the vehicle suspension system. The theoretical quality distribution is well matched with practical systems by adjusting unit size and distribution. A fine finite vehicle element model is established to research the vibration response of vehicle-bridge coupling dynamic response based on a 3-axle heavy vehicle. Comparison of simulated and measured values of vehicle axle load applying natural frequency FEM is performed to verify the validity of the model. Taking a simply supported beam bridge as an example, LS-DYNA finite element software and MATLAB are used to simulate and analyze the mass-spring-damping vibration system, and the bridge vibration response subjected to vehicle load at constant speed is researched comparatively. The results show the feasibility of using a LS-DYNA fine model to analyze vehicle-bridge coupling vibration, but the computational workload is very high for this model.
系杆拱桥是拱肋、吊杆、系杆等组合共同受力的,针对这一受力特性,由能量变分原理推导出系杆拱拱肋的弯矩增大系数实用计算公式,以工程实例将所推公式与现行桥规中偏心距增大系数的简化公式计算结果进行对比。结果表明,推导出的实用计算公式的计算结果与现行桥规按照裸拱简化为当量长度的直杆的计算结果相差12.9%~24.3%,所推公式在简化前后计算结果相差在1%左右,显示出简化后的计算公式有一定的经济实用性。所推公式中,系杆拱桥拱肋的弯矩增大系数随轴力增大而略显增大,且与约束条件及荷载形式相关,拱式结构中拱肋的偏心距增大系数与偏心受压直杆的偏心距增大系数有较大差别。
For scientific and reasonable decision making regarding the through scheme of arterial highways in city areas, the grey correlation is commonly used to measure the closeness between an alternative scheme and an ideal scheme. In this paper, a grey lattice order decision-making method is proposed, and using the proposed method, the through schemes of arterial highway G204 in Yancheng City are compared. The analysis indicates that from the aspects of economic and environmental impacts, the through model that bypasses the city is the best through scheme despite an increase in detour distance of the vehicles using the route. The application results show that the grey lattice order method combines the advantages of the grey correlation and lattice order methods to better reflect the relative relationships of the pros and cons between alternatives.
针对已有钢管混凝土拱非线性有限元模型精度和效率不高的问题,基于动坐标迭代法及全量平衡建立了高效钢管混凝土拱平面非线性有限元模型。首先,在局部坐标系下根据应变与单元去掉刚体平动和转动后的纯变形呈线性关系的特点导出截面切线刚度矩阵,利用虚功原理得到单元切线刚度矩阵;再通过动坐标迭代法来考虑几何非线性及基于全量平衡来计算不平衡力,最终建立了钢管混凝土拱考虑几何与材料双重非线性的平面有限元模型。基于该非线性单元模型研制了相应的程序,对只考虑几何非线性的算例及考虑几何与材料双非线性的算例进行了分析,与其他文献对比分析表明:该文算法能够显著减少计算量并提高计算精度。研究结果可为实际钢管混凝土拱桥几何及材料非线性分析提供新方法。
The typical U.S. Bureau of Public Roads (BPR) volume-delay function is modified to construct the more suitable model to China's road traffic situation. Factors influencing road traffic impedance, such as the number of lanes,speed limit, intersection density, bus stop density, saturation and congestion are considered. On the basis of actual data collected from different main roads in Dalian city, traffic impedance functions for different road types (expressway, trunk road, secondary trunk road and slip road) are calculated using SPSS software. The results analysis of the traditional and improved BPR volume-delay functions is compared to certify the useful improved BPR volume-delay function.To apply road traffic impedance to the traditional four-step model,we calculate the daily conversion coefficients. These reflect the relationship between hourly traffic impedance and daily impedance function and suggest the suitable usage of daily conversion coefficients in further research.
针对预应力混凝土梁动力特性退化的问题,选取预应力混凝土简支梁,通过模型进行了单调加载和重复超载作用下梁的加载试验,并测试构件竖向、横向及纵向3个方向的振动参数,从而得到各种荷载状态下构件的动力参数、自振频率和振型;研究分析了预应力混凝土简支梁频率的变化及动刚度随荷载增加而退化的规律。结果表明:梁在荷载损伤之后,其各阶频率随着荷载等级的提高而降低,梁达到屈服荷载,频率下降较为明显;重复超载次数对部分预应力混凝土梁频率退化的影响并不明显,动刚度随着荷载的增加降低也不明显;不同配箍率对纵向和横向基频没有明显影响。
To cope with the capacity limitations of enterprise's own transport fleet for container transport and the increasing competitive pressure, considering the operating costs and the demand uncertainty, an outsourcing decision-making problem for truck fleet with quantity discounts for continuous working shifts is presented. From the perspective of competition and social-effects analysis, we suggest an extended vehicle routing problem with time windows (VRPTW) vehicle scheduling model. The model minimizes costs and provides an evaluation system with minimal mileage and carbon emissions. By adjusting quantity-discount rules and task time windows, our model can be used to provide outsourcing solutions for different combinations of continuous working shifts. We also discuss the influence of other parameter settings on the decision schemes. Finally, we verify both the model and the algorithm using a simulation experiment. The experimental results show that using quantity discounts for fleet outsourcing decisions for different combinations of continuous working shifts improves both vehicle utilization and social benefits. We also highlight new research opportunities based on these results.
为更全面地了解模数式桥梁伸缩缝动态响应,以ZL480模数式桥梁伸缩缝为研究对象,应用ANSYS软件建立其参数化模型,分析改变横梁间距BHK、中梁支撑刚度K2和缝宽B等参数对其固有频率和灵敏度的影响。研究结果表明:当横梁间距BHK从1 m增加到2 m,间距增加100%,第1阶固有频率ω1减小了32.6%;中梁支撑刚度K2从40 000 N/mm增加到100 000 N/mm,刚度增加了150%,第1阶固有频率ω1增加了24%;随横梁间距BHK的减小、横梁下支撑刚度K4、中梁支撑刚度K2、中梁刚度K1的增大,模数式桥梁伸缩缝固有频率逐渐增大,且灵敏度依次降低;缝宽B及横梁刚度K3的改变对其固有频率影响不大。
This study aims to satisfy the energy management contract (EMC) work schedule of the Ministry of Transport (MOT). The paper first defines EMC together with its connotations to clarify its specific demands for the market environment, economic policy, law, and technology policy. Using New Structural Economics theory, this study investigates specific actions that would enable the MOT to popularize EMCs. EMC development goes hand in hand with the development of a market-oriented economy; therefore, proposing commercial behavior in the transport market becomes a priority. Industry management should therefore guide private enterprises' EMC development in the light of its general trends. In terms of advancing the legal environment, we suggest implementation of a policy of "not-banned that in" and a diversified interest settlement mechanism to resolve interest disputes. In technical policy, we suggest drawing up "energy-saving projects verification and test guide for the transportation industry" and "energy-saving effects: Guidance for the transportation industry" to establish technological standards.
以Hoek-Brown弹塑性模型及应变软化模型为基础,采用FLAC3D数值模拟软件,构建三维数值模型,计算深埋隧道不同开挖方式下的围岩特征曲线,并对隧道围岩及支护结构稳定性进行评价。研究结果表明:采用Hoek-Brown弹塑性模型计算所得的隧道围岩安全系数要低于应变软化模型所计算得到的安全系数,表明采用弹塑性模型进行支护结构设计时,支护结构安全性较低,设计中可能会导致支护材料费用的增加,而考虑应变软化条件下的围岩安全系数更加接近工程实际;采用不同开挖形式所获得的隧道围岩安全系数并不相同,采用全断面法开挖所获得的安全系数要明显低于七步开挖法,采用收敛约束法计算隧道围岩稳定性更加直观。
针对黄土隧道施工过程中遇到的软弱地质带问题开展了研究。首先,分析了黄土软弱地质带的形成机理。其次,依据黄土软弱地质带的形成机理,采用有限差分数值分析方法分析了黄土隧道穿越软弱地质带隧道可能的破坏形式。最后,根据该破坏形式提出了黄土隧道穿越软弱地质带的超前加固处理措施,并分析了处理后的效果。分析结果表明:黄土软弱地质带形成原因主要有水流下浸、水流上浸和土岩交界面3种形式;如果采用合理的超前加固措施,在黄土隧道穿越软弱地质带的施工过程中能实现成功的穿越。
以港珠澳沉管隧道天然地基段某一横断面为研究对象,对垫层厚度1 m及1.5 m的工况分别进行了模拟整个施工过程的离心模型试验及有限元计算研究,揭示了不同垫层厚度地基回弹再压缩应力应变特性、沉管结构的应变特征,为沉管隧道的施工及地基处理方案设计提供依据。结果表明,开挖卸荷基底产生拱形回弹;回填后基底应力及沉管底板应变均呈马鞍形分布;随时间及回淤增加,仅基底中部应力增大。垫层薄,基底应力分布匀化效果差,再压缩量及工后沉降增大。
为了解决不同属性用户路径选择相互影响的混合交通均衡分配问题,利用变分不等式描述了混合网络中用户平衡UE、系统最优SO、古诺-纳什均衡CN这3类用户的路径选择行为。分别采用基于路段的对角化算法和基于路径的双重投影算法对混合网络均衡模型进行求解,以Sioux Falls网络为例,从计算效率、收敛精度2个方面对其进行对比分析。分析结果表明:对角化算法前期收敛较快,但拖尾严重,很难通过多次迭代达到较高的精度;双重投影算法即使经过上千次迭代,精度仍可提高。在多种混合比例下,SO、CN用户控制流量比越大,系统总阻抗越小,而SO用户流量比低于0.5时,系统总阻抗下降很快,随着流量比增大,下降速度随之变缓。
城市道路路侧冗余信息对指路标志视认的干扰对行车安全极为不利。设计了不同信息量的城市道路指路标志牌,并与典型的路侧冗余信息组合设置;然后在大量室内模拟试验基础上,利用稳健估计理论与方法,分有目标路名、无目标路名2种情况,对单块指路标志、道路景观标志组合、小汽车标志组合、女明星标志组合、路名(地名)指路标志组合的视认时间、视认反应时间进行了对比研究,得到不同类型路侧冗余信息对指路标志的影响程度。结论:路侧冗余信息影响程度从大到小顺序为路名(地名)标志、女明星广告、小汽车广告、道路景观。其中路名(地名)辅助信息、女明星广告干扰十分显著,在城市交通中应尽量避免;小汽车广告、道路景观干扰较小,可适当设置。
以城市路外停车出入口影响区作为研究对象,将拟停放车辆从最右侧车道右转驶离主路进入停车场的过程对于上游运行车辆的影响区长度表述为停放车辆减速进入停车场距离和跟驰运行车辆的交通波传播距离2个部分。通过理论分析并结合调查数据建立了基于不同驶入时间及不同饱和度下影响区动态长度的计算模型,确定了停车影响时间、速度变化系数等主要参数的适用条件。通过实例并采用VISSIM5.3软件对模型进行了仿真对比验证,主要结论有:(1)当驶入时间在4~8 s时,饱和度与影响区长度呈现反比关系;驶入时间大于8 s时,饱和度与影响区长度呈现正比关系;(2)当饱和度在[0.46~0.5]驶入时间在4~15 s时车辆驶入对主路上游车辆没有影响;(3)当饱和度大于0.6,驶入时间大于9 s时,车辆驶入对主路上游车辆的影响长度增幅明显。
在传统元胞自动机模型的基础上,增加了对交通事件状态下驾驶员行为的特征分析,提出了基于速度的换道规则以改进传统的STCA模型,构建了适用于模拟交通事件状态下交通流的元胞自动机仿真模型。利用改进的模型和传统的STCA模型进行了双车道高速路一条车道关闭交通事件交通流仿真试验。试验结果表明,就车辆在关闭位置上游处分布和换道行为的空间分布而言,该模型能够比传统STCA模型更加真实地模拟交通事件状态下的交通流状态。
针对重大突发事件应急运输需求的特征,分析了情景应对约束下应急车辆联合运输独立决策和集体决策2种运输模式,分别给出了其基于运输效率最大化的数学模型。考虑突发事件情景需求的不确定性、调运成本结构的不同,以及独立决策下不同运输应急服务点有Pareto优化的余地,分析了应急车辆联合运输中2个应急服务点之间的协调关系,构建了基于情景应对机制约束下的协调模型,并针对不同情景对模型进一步分析,得到一些重要的结论。最后通过算例计算分析验证了这些结论的正确性和有效性。通过合理情景应对机制的设定,使得运输效率最大化的同时,2个应急服务点运输得到协调,达到情景应对运输决策优化,及时有效地降低突发事件带来的灾害的目的。
对电动汽车电液复合制动系统的结构和工作原理进行了简单的概述。在分析基于传统摩擦制动系统的再生制动控制策略的基础上,重点讨论了电液制动系统对电动汽车制动能量回收能力的影响。结合电液复合制动系统能够对电动汽车制动过程进行精确控制的特点进行的理论分析表明,将摩擦制动力矩尽量分配到汽车非驱动轴能够使制动能量回收最大化。根据上述结论设计了基于电液复合制动系统的再生制动控制策略,在ADVISOR2002中进行了仿真研究,验证了该再生制动控制策略的有效性。结果表明,该再生制动控制策略相较于传统的并行制动分配控制策略,能够提高电动汽车的制动能量回收率和整车有效能量回收率。
针对再生制动时能量回收效果的评价缺少有针对性的标准循环工况,构建了一种基于多元统计学概率分布理论的标准循环工况。提出了城市再生制动标准循环工况的构建方法,对采集的北京和天津道路工况数据进行了统计分析与处理。结合马尔可夫分析,构建了大型城市再生制动标准循环工况。对比试验结果表明,大型城市再生制动标准循环工况是有效的,对于其他城市再生制动标准循环工况的制订具有实用价值。
