低剂量水稳基层防治薄面层沥青路面反射裂缝研究

采用低剂量水泥稳定碎石基层作为防治薄面层沥青路面反射裂缝的主要方案,利用室内试验和试验路工程分别得到不同剂量水泥稳定碎石基层的收缩特性以及强度发展规律。力学分析和观测结果都证明该方法可以有效防治薄面层沥青路面反射裂缝。     

石灰土中石灰活性衰减规律研究

通过试验的方法研究松散石灰土在常温和低温开放状态、常温密封状态条件下石灰活性衰减的规律，推定出不同状态条件下石灰活性衰减率公式，以确定石灰土合理的闷料时间，减少不必要的石灰活性衰减和未消解石灰对路面基层的破坏，为石灰土路面基层质量问题的界定提供依据。     

Wheel-rail contact models for vehicle system dynamics including multi-point contact

Advanced modelling of rail vehicle dynamics requires realistic solutions of contact problems for wheels and rails that are able to describe contact singularities, encountered for wheels and rails. The basic singularities demonstrate themselves as double and multiple contact patches. The solutions of the contact problems have to be known practically in each step of the numerical integration of the differential equations of the model. The existing fast, approximate methods of solution to achieve this goal have been outlined. One way to do this is to replace a multi-point contact by a set of ellipses. The other methods are based on so-called virtual penetration. They allow calculating the non-elliptical, multiple contact patches and creep forces online, during integration of the model. This allows nearly real-time simulations. The methods are valid and applicable for so-called quasi-Hertzian cases, when the contact conditions do not deviate much from the assumptions of the Hertz theory. It is believed that it is worthwhile to use them in other cases too.     

水泥混凝土路面质量病害问题探讨

根据目前水泥混凝土路面建设比较普遍的情况,针对施工中出现比较多的质量病害进行了分析,分别从水泥混凝土路面的裂缝产生的过程,材料、配合比、水灰比、施工操作等对质量的影响,以及产生外观质量缺陷的原因进行了评述.     

沥青路面填封裂缝和修补坑槽再破损原因分析

为了检验沥青路面裂缝填封和坑槽修补的效果,对填封裂缝和修补坑槽较常出现的再破损形式进行了归纳,并深入地分析了已填封裂缝和已修补坑槽再次出现破损的原因.     

Simulation on progressive collapse behaviour of whole ship model under extreme waves using idealized structural unit method

To ensure the safety of navigating ship, working loads and structural load-carrying capacity are two important aspects. In the present paper, a total simulation system combing load calculation and structural collapse analysis is applied to simulate progressive collapse behaviour of a single-hull Kamsarmax type bulk carrier. A three dimensional singularity distribution method is adopted to calculate pressure distribution with time history. A mixed structural model, collapse part simulated by ISUM elements and remaining part by elastic FEM elements with relative coarse mesh, is proposed for collapse analysis. Progressive collapse behaviour obtained by ISUM is good agreement with that by nonlinear software package, MARC. However, the calculation time of ISUM analysis is about 1/70 of MARC analysis. The applicability to structure system, high accuracy and sufficient efficiency of ISUM had been demonstrated.     

Probabilistic fatigue analysis of marine structures using the univariate dimension-reduction method

Probabilistic fatigue analysis of offshore structures requires the numerical simulation of a huge number of loading cases to compute the long-term multi-dimensional integral associated to the fatigue damage assessment. This paper proposes the implementation of the univariate dimension-reduction method developed by Rahman and Xu [1] in order to compute the long-term fatigue damage more efficiently. This method is particularly attractive because it reduces significantly the number of simulations by decomposing the N-dimensional integral associated to expected long-term fatigue damage assessment into the sum of N one-dimensional integrals. In addition, this paper compares the univariate-dimension reduction method with the brute force direct integration methodology and other methods based on Taylor expansions, such as perturbation approach and asymptotic expansion method discussed by Low and Cheung [2]. Two comprehensive examples are included to show the effectiveness of the method. At first, the performance of the univariate dimension-reduction method is evaluated by assessing the fatigue damage of a theoretical structure represented by a single stress response amplitude operator (RAO). Then, in order to show a case of practical application, the fatigue damage is evaluated for a Steel Lazy Wave Riser (SLWR) connected to an FPSO in a water depth of 2200 m.     

Experimental investigation of evaporation rate and exhaust emissions of diesel engine fuelled with cotton seed methyl ester and its blend with petro-diesel

An experimental study to measure the evaporation rates, engine performance and emission characteristics of cotton seed biodiesel (cotton seed oil methyl ester) and its blends in different volumetric proportions with diesel is presented. The thermo-physical properties of all the fuel blends have been measured and presented. Evaporation rates of neat cotton seed biodiesel, neat diesel and their bends have been measured under slow convective environment of air flowing with a constant temperature. Evaporation constants have been determined by using the droplet regression rate data. The neat fuels and fuel blends have been utilized in a test engine with different load conditions to evaluate the performance, combustion and emission characteristics of the fuels. The specific fuel consumption values of the two blends, viz. B25 and B75 are found to be same. At the highest load, B0 records the lowest CO volume followed by B100. From the observed evaporation, performance and emissions characteristics, it is suggested that a blend of B50 and B75 can be optimally used in standard diesel engine settings.     

桥梁模板施工技术应用性研究

桥梁模板是桥梁施工中的重要工具。通过搜集国内外桥梁模板资料,研究总结并提出解决模板工程在桥梁施工中存在各种问题的办法,将对提高工程质量、加快施工速度、提高劳动生产率、降低工程成本和实现桥梁工程的文明施工起到一定的推动作用。     

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。