Technologies for Asphalt Pavement Surface Testing in Road and Bridge Construction

Asphalt pavement is currently one of the main components in the construction of roads and bridges.However,from a practical point of view,various quality problems are prone to occur in the surface layer of asphalt pavement,which will lead to the poor overall quality of road and bridge projects.Therefore,it should be applied reasonably.Advanced testing technologies are used to test the mixture quality,compaction,segregation,thickness,and other aspects of the asphalt pavement surface layer,so as to improve the quality of the asphalt pavement surface layer,and then improve the overall quality of road and bridge construction.Therefore,this paper mainly analyzes the technologies for asphalt pavement surface layer testing in road and bridge engineering construction.

Effects of polar cortical cytoskeleton and unbalanced cortical surface tension on intercellular bridge thinning during cytokinesis

To probe the contributions of polar cortical cytoskeleton and the surface tension of daughter cells to intercellular bridge thinning dynamics during cytokinesis,we applied cytochalasin D（CD） or colchicine（COLC） in a highly localized manner to polar regions of dividing normal rat kidney（NRK） cells.We observed cellular morphological changes and analyzed the intercellular bridge thinning trajectories of dividing cells with different polar cortical characteristics.Global blebbistatin（BS） application was used to obtain cells losing active contractile force groups.Our results show that locally released CD or colchicine at the polar region caused inhibition of cytokinesis before ingression.Similar treatment at phases after ingression allowed completion of cytokinesis but dramatically influenced the trajectories of intercellular bridge thinning.Disturbing single polar cortical actin induced transformation of the intercellular bridge thinning process,and polar cortical tension controlled deformation time of intercellular bridges.Our study provides a feasible framework to induce and analyze the effects of local changes in mechanical properties of cellular components on single cellular cytokinesis.

Nonlinear beam formulation incorporating surface energy and size effect:application in nano-bridges

A nonlinear beam formulation is presented based on the Gurtin-Murdoch surface elasticity and the modified couple stress theory. The developed model theoretically takes into account coupled effects of the energy of surface layer and microstructures size- dependency. The mid-plane stretching of a beam is incorporated using von-Karman nonlinear strains. Hamilton＇s principle is used to determine the nonlinear governing equation of motion and the corresponding boundary conditions. As a case study, pull-in instability of an electromechanical nano-bridge structure is studied using the proposed formulation. The nonlinear governing equation is solved by the analytical reduced order method （ROM） as well as the numerical solution. Effects of various parameters including surface layer, size dependency, dispersion forces, and structural damping on the pull- in parameters of the nano-bridges are discussed. Comparison of the results with the literature reveals capability of the present model in demonstrating the impact of nano- scale phenomena on the pull-in threshold of the nano-bridges.

Surface Tension and Electrostriction in a Suspended Bridge of Dielectric Liquid

The mechanism of the formation of a surprisingly long suspended liquid bridge subjected to a dc electric field has been intensively studied in the past few decades. However, the role of electrostriction and quantitative evaluation of surface tension in the bridge have not been evaluated. We present combined theoretical and experimental studies on this issue. Electrostriction is pointed out to be the driving force that pushes liquid upward against gravity and into the gap between two containers and forms the suspended bridge, which is within the framework of the Maxwell pressure tensor. Through a comparison between experiment and theory, the surface tension is found to play an important role in holding the long suspended bridge. Ignorance of the surface tension leads to much smaller bridge length than the experimental values. The dynamic stability of the bridge with respect to its diameter, length and conductance is also discussed.

基于Surface Evolver模拟液桥断裂距离

目的研究面间液桥断裂距离随着液桥体积、球面半径和固-液接触角的变化规律。方法利用SurfaceEvolver程序模拟介于球形表面和平面间一定体积液桥的拉伸、断裂的演变过程,从模拟结果中得到给定液桥体积、球面半径以及固体表面润湿性质这些参数下的液桥的断裂距离。结果以Lian等和Willett等所给出公式为基础得到液桥断裂距离关于参数液体体积、球面半径和接触角的理论公式,模拟结果与理论预测结果比较,发现当固体表面为亲水性质时,模拟结果与理论结果整体上吻合很好(偏差<4.3%);当固体表面为疏水性质时,模拟结果随着疏水性质的增加与理论估计的偏差会增大。结论 Surface Evolver可以很好地模拟液桥准静态拉伸和断裂过程,从而得到液桥断裂距离。Lian等和Willett等所给出的理论公式是由亲水表面数据拟合出来的,这也是在疏水性质表面上本文所给液桥断裂距离的理论公式预测结果与模拟结果偏差增大的原因。

Influence of the NAO on Wintertime Surface Air Temperature over East Asia:Multidecadal Variability and Decadal Prediction

In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.

Insights into the adsorption performance and mechanism of hydrated Ca ion on talc(001) basal surface from DFT calculation

The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported.Thus,the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC on talc depression.In this paper,mechanism insights into hydrated Ca ion adsorption on talc(001) basal surface were creatively provided using DFT calculation.[Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) were determined as the effective hydrate components for Ca ion adsorption,and the top O site was the most favorable position for their adsorptions on talc surface.Furthermore,the adsorption mechanisms of [Ca(H_(2)O)_6]^(2+) and [Ca(OH)(H_(2)O)_(3)]^(+) on talc surface were found to be not the Ca-O chemical bond,but the hydrogen bonding formed by the H atom of the H_(2)O ligand and the surface O atom.H_(2)O acted like a bridge to connect them to the talc surface.Moreover,the hydrogen bonding was formed due to the hybridization of H 1s orbital with the O 2s,O 2p orbitals.Simultaneously,electrons transferred between the H atom and the surface O atom.This work provides theoretical insights into the Ca ion adsorption on talc surface,which can help deeply understand the talc flotation using CMC as depression.

Micromechanical tunable vertical-cavity surface-emitting lasers

We report the study on a short wavelength-tunable vertical-cavity surface-emitting laser utilizing a monolithically integrated bridge tuning microelectromechanical system. A deformable-bridge top mirror suspended above an active region is utilized. Applied bridge-substrate bias produces an electrostatic force which reduces the spacing of air-gap and tunes the resonant wavelength toward a shorter wavelength （blue-shift）, Good laser characteristics are obtained： such as continuous tuning ranges over 11 nm near 940 nm for 0-9 V tuning bias, the peak output power near 1 mW and the full-width-half-maximum limited to approximately 3.2-6.8 rim. A detailed simulation of the micromechanical and optical characteristics of these devices is performed, and the ratio of bridge displacement to wavelength shift has been found to be 3：1.

Effects of Surface Defects on Adsorption of CO and Methyl Groups on Rutile TiO_(2)(110)

The interaction of reactants with catalysts has always been an important subject for catalytic reactions.As a promising catalyst with versatile applications,titania has been intensively studied for decades.In this work we have investigated the role of bridge bonded oxygen vacancy(O_(v))in methyl groups and carbon monoxide(CO)adsorption on rutile TiO_(2)(110)(R-TiO_(2)(110))with the temperature programmed desorption technique.The results show a clear different tendency of the desorption of methyl groups adsorbed on bridge bonded oxygen(O_(b)),and CO molecules on the five coordinate Ti^(4+)sites(Ti_(5c))as the Ovconcentration changes,suggesting that the surface defects may have crucial influence on the absorption of species on different sites of R-TiO_(2)(110).

抢险车对92m跨度复合材料桁架桥动态响应的影响

为研究大跨径桁架式纤维增强复合材料(FRP)应急抢修桥梁成桥后的动力性能,基于导梁推送施工92 m跨度的FRP桁架桥模型,编制FRP桁架桥的车桥耦合算法,研究抢险车辆的车速、质量及路面不平顺对FRP桁架桥的跨中竖向位移、竖向加速度和关键杆件轴向应力等指标的影响.结果表明:路面越不平顺,车辆对桥梁结构的冲击作用越大,且路面等级对竖向位移的影响大于对关键杆件轴向应力的影响;车速为20~50 km/h时,车速变化对冲击系数影响较小,但车速超过50 km/h时,车速的影响逐渐增大;车辆质量对桥梁各项指标动力响应的峰值曲线呈线性增大趋势.当车辆质量为2.80×10^(4)kg,车速30 km/h时,最大跨中竖向位移为167 mm,未超过抢修桥梁位移限值(L/120),表明该桥梁的设计可以满足抢险的通行要求.

采用改进多目标粒子群算法的斜拉桥阻尼器参数优化

为克服大跨度斜拉桥黏滞阻尼器优化设计效率低、多个相互制约的减震控制目标的问题难以权衡,基于遗传算法的“变异”方法,提出了改进多目标粒子群算法来进行阻尼器参数优化设计。建立大跨度斜拉桥的有限元模型,开展了全桥地震响应分析,根据抗震需求在桥梁纵向设置黏滞阻尼器;分别建立了塔底弯矩、阻尼力和梁端位移的减震响应与阻尼器参数之间的响应面数学模型;以减震响应面模型为研究对象,通过该算法进行阻尼器参数全局自动寻优分析,确定了阻尼器的最优参数,并与采用参数敏感性分析方法确定的一组阻尼参数进行对比分析。研究结果表明:该优化方法具有计算精度好、优化效率高和更好地权衡多个相互制约的减震控制目标的优点;通过优化算法获得的阻尼器参数组合相比采用参数敏感性分析方法获得的阻尼参数组合的减震响应,塔底弯矩增大1.73%,阻尼力减小5.97%,梁端位移减小1.66%;在无需多次有限元试算的基础上确定了更高精度的阻尼器优化参数组合,在提高减震效果的同时大大提升了计算效率。

关于采空区地表变形对桥梁影响的研究

目的 以二龙山1号高架桥为研究背景,研究既有采空区所引起的地表沉降以及沉降对已建桥梁的影响。方法 结合数值模拟分析,拟定不同的采空区情况(采空区半径、采空区空洞高度、采空区顶板埋深、顶板弹性模量),分析在自重及附加桥梁荷载作用下,地表沉降规律以及地表沉降对已建桥梁的影响。结果 地表沉降最大值与采空区半径大小、采空区空洞高度呈正相关;地表沉降最大值与采空区顶板埋深、采空区顶板岩层弹性模量呈负相关;结合相邻墩台最大沉降差的要求,在实际工程中,采空区半径小于60 m、采空区埋深大于55 m、采空区空洞高度小于1 m、桥梁正下方岩层弹性模量大于2 000 MPa,理论上可以不进行处治。结论 采空区半径越小,顶板埋深越大,空洞高度越小,顶板岩层弹性模量越大,采空区地表变形越小,对已修建桥梁影响越小。

基于融合WM算法的Mamdani型模糊推理的板桥损伤定量分析

为对板桥局部位置的损伤程度进行定量分析,提出1种基于融合WM算法的Mamdani型模糊推理板桥损伤定量分析方法,探讨影响面指标和损伤程度之间的独特联系,并通过MIDAS及Python模拟计算并分析板的损伤程度。研究结果表明:模糊逻辑系统具有较为出色的记忆能力。当融合WM算法到模糊逻辑系统中时,不论是单点损伤还是多点损伤,都能对板桥的损伤程度进行准确识别;当未融合WM算法时,由于其模糊规则没有进行置信度计算,将错误的规则也计算在内,最终导致定量结果精度下降。研究结果可为板桥结构的损伤评估和维护策略提供较为科学准确的参考。

基于响应面法的钢管混凝土系杆拱桥有限元模型修正

为探讨将钢管混凝土系杆拱桥有限元模型修正方法应用于实际工程性能评估的有效性,以某80 m单拱面钢管混凝土系杆拱桥为工程背景,采用Midas Civil与ANSYS有限元软件分别建立全桥梁格模型与拱脚精细化数值模型,基于径向基函数网络的响应面法对此多尺度模型进行修正。首先根据结构特点和实桥试验选取修正参数与目标函数,以中心复合试验设计构造不同修正水平下的修正参数样本,通过桥梁有限元模型计算得到对应的目标函数样本,并利用F检验法对修正参数的显著性水平进行判断;然后,以修正参数样本与目标函数样本分别作为响应面的输入输出,对径向基函数网络进行拟合训练;最后在修正范围内随机生成修正参数样本,并利用训练好的径向基网络预测对应的目标函数,采用期望度函数D进行优化处理以完成有限元模型的修正。研究结果表明:对于单拱面钢管混凝土系杆拱桥的有限元模型,可以通过径向基函数网络的响应面法进行修正,对比实测数据,修正后的模型误差有明显下降,可作为结构再分析的基准模型;对于使用不同程序建立的多尺度桥梁有限元模型,模型修正方法依旧有效,修正后的参数具有明确的物理意义,其误差可降到工程实践接受范围之内。研究结果为建立与修正钢管混凝土系杆拱桥的有限元模型提供参考。

不同地震激励方向下隔震曲线梁桥易损性分析

为进一步评估隔震曲线梁桥在地震激励下的抗震性能,从地震易损性角度出发并兼顾考虑地震激励方向对其易损性的影响。利用APDL建立采用板式橡胶支座的隔震曲线梁桥有限元模型,从PEER中选取同一地震事件中的近断层地震动,按规范规定比例输入水平双向地震动进行非线性动力时程分析,结合地震响应与损伤指标计算得到各构件地震易损性曲线;考虑地震激励方向的变化,通过MATLAB编程绘制得到桥梁结构构件(桥墩与支座)以及整体系统的地震易损性曲面,分析探讨地震激励方向对隔震曲线梁桥易损性的影响。结果表明:不同极限状态下各桥墩切向损伤条件概率明显大于其径向,各支座的切向与径向易损性相差不大,但仍是各支座的切向易损性略大于径向易损性;桥梁各构件(桥墩与支座)切向易损性对地震激励方向均表现出很强依赖性,而径向易损性对其的依赖性相对较弱,且伴随损伤等级的提高,构件易损性对地震激励方向更加敏感;桥梁整体系统易损性对地震激励方向的变化不太敏感,且因各构件响应之间的相关性较高,其系统易损性更接近于易损性最大的构件——易损性下限;当进行隔震曲线梁桥抗震性能评估时,应考虑不同地震激励方向对其地震易损性的影响,从而使得易损性分析结果更加合理,能够更加真实地反映隔震曲线梁桥的实际损伤状态。

基于改进Faster R-CNN与U-Net算法的桥梁病害识别与量化方法

为实现桥梁病害检测的自动化,对基于图像处理技术的混凝土桥梁表观病害的智能识别和尺寸确定方法展开研究.提出基于改进Faster R-CNN算法的病害识别方法,利用K均值聚类和遗传算法对区域候选网络锚框进行优化设计;以裂缝预测区域为基础,提出ResNet34结合U-Net的裂缝形态提取方法,并结合裂缝形态学研究了裂缝像素宽度和长度的确定方法.结果表明:锚框优化设计可改进Faster R-CNN算法的表观病害识别效果,5类常见病害的预测准确率、召回率、平均精确率分别由68.40%、69.87%、74.64%提升到85.40%、83.59%、83.72%;利用病害预测框,结合改进U-Net算法的裂缝像素尺寸计算,可实现裂缝病害尺寸的自动测量;基于改进Faster R-CNN和改进U-Net的方法可实现混凝土桥梁常见病害的智能识别和尺寸量化,从而提高桥梁病害检测效率并促进桥梁技术状况评定的智能化.

Interfacial behaviors of epoxy asphalt surfacing on steel decks

A model for predicting the interface behavior of epoxy asphalt and steel composite beam under negative bending is developed incorporating partial interaction theory. Interfacial slips between the steel deck and the epoxy asphalt surfacing are included in the model with a new parameter of membrane stiffness. A series of analytical equations based on this model are derived to calculate slip and strain at the interface. Also, a numerical procedure for calculating the load responses of simply supported composite beams with concentrated force at the mid-span is established and verified with two samples. Characters of slip and strain at the interface, sensitivities of tensile stress and interface shear stress with material parameters are studied. It can be concluded that interfacial effects decrease the bending stiffness of the composite; hard and stiff bonding material is better for asphalt surfacing layer working at normal to low temperatures, and the damage of the asphalt surfacing layer will be accelerated with the damage accumulation of the bonding coat.

压电双轴驱动柔顺微夹钳设计与控制

提出了一种压电双轴驱动对称结构的柔顺微夹钳。该微夹钳由2个对称分布的桥式放大器组成,每个桥式放大器分别连接到一个杠杆机构来放大输出位移。利用虚功原理和拉格朗日方程建立运动学和动力学模型。考虑到各参数对机械结构的影响,分析机构的静力学和动力学特性,同时采用有限元方法对建立的模型进行评估和验证。为了进一步揭示所设计的微夹钳的性能,利用线切割方法加工出了微夹钳样机。采用动态面控制算法对系统进行了一系列控制实验来说明微夹持器的运动特性。结果表明:微夹持器的左、右放大器的放大倍率分别为11.25和11.67,其位移跟踪性能好,通过夹持纸片,检测了末端微夹持力的大小,验证了前面设计分析的正确性和可行性。

道路桥梁工程路基路面振荡压实施工技术研究

为解决道路桥梁工程路基路面压实度过低的问题,以某省级干线公路工程为例,进行路基路面振荡压实施工技术研究。首先,采用振荡压路机,对路基路面进行振动压实。其次,结合工程实际情况,确定压实速度与碾压作业段长度。最后,针对纵向接缝构造和横向接缝构造进行碾压,实现对路基路面的压实,促进压实度提升,提高道路桥梁工程施工质量。