大跨连续梁桥减隔震方案对比分析

以1座(90+170+90)m城市大跨度连续梁桥为研究对象,提出并比较分析两种减隔震设计方案。采用弹性反应谱法及非线性时程反应分析方法研究E1及E2地震作用下结构的地震反应,针对两种方案比较摩擦摆支座的力学参数取值及结构地震反应的差异。结果表明:(1)对于大跨连续梁桥,由于纵桥向一联内仅设置一个制动墩,地震内力分布极不均匀;但横桥向结构内力分布较均匀,各墩联合共同受力;(2)采用摩擦摆支座,E2作用下各墩墩底截面纵、横向内力减震效果显著且各墩的内力分布趋于均匀,分布更加合理;(3)采用摩擦摆支座,E2作用下减隔震后的墩底内力通常小于E1作用下弹性反应分析结果。E1作用下摩擦摆支座是否允许滑动,对结构的地震反应影响显著。在实际设计中应认真加以分析对比。     

城市道路平面交叉口改进方案评价方法的研究

针对城市道路平面交叉口改进方案评价的复杂性,建立了交叉口改进方案的综合评价指标体系,提出了基于层次分析法(AHP)的评价模型与方法,采用定量与定性相结合的方法确定了各项评价指标及其分级标准。并对北京市交大东路和学院南路平面交叉口的改进优选方案进行了实例分析, 并采用 VISSIM 微观动态仿真软件,对该改进优选方案进行了模拟仿真评价验证。     

长联公铁两用钢桁梁桥采用速度锁定器装置减震性能研究

长联公铁两用钢桁梁桥固定墩地震响应大,抗震设计困难。通过设置速度锁定装置,并对各种速度锁定器布置方案进行比选分析,研究该类桥梁桥墩采用速度锁定器装置后的减震性能。由于设置速度锁定器装置的活动墩的分担,各方案整体减震率可达到20.5%～47.1%。如锁定墩(设置速度锁定器装置的活动墩)墩高相比固定墩和其他锁定墩墩高矮很多,或者锁定墩一侧未采用速度锁定器装置的活动墩较多,则该锁定墩的地震响应可能超过原固定墩。该类桥梁确定锁定器布置方案时应综合考虑内力和位移的减震效果、锁定力大小,并同时兼顾公路层和铁路层梁-墩相对位移的大小等因素的影响。对长联公铁两用钢桁梁桥,采用速度锁定器装置并优化其布置方案后,可取得较好的减震效果。     

Characterising group-cycling journeys using interactive graphics

The group-cycling behaviours of over 16,000 members of the London Cycle Hire Scheme (LCHS), a large public bikeshare system, are identified and analysed. Group journeys are defined as trips made by two or more cyclists together in space and time. Detailed insights into group-cycling behaviour are generated using specifically designed visualization software. We find that in many respects group-cycle journeys fit an expected pattern of discretionary activity: group journeys are more likely at weekends, late evenings and lunchtimes; they generally take place within more pleasant parts of the city; and between individuals apparently known to each other. A separate set of group activity is found, however, that coincides with commuting peaks and that appears to be imposed onto LCHS users by the scheme’s design. Studying the characteristics of individuals making group journeys, we identify a group of less experienced LCHS cyclists that appear to make more spatially extensive journeys than they would do normally while cycling with others; and that female cyclists are more likely to make late evening journeys when cycling in groups. For 20% of group cyclists, the first journey ever made through the LCHS was a group journey; this is particularly surprising since just 9% of all group cyclists’ journeys are group journeys. Moreover, we find that women are very significantly (p < 0.001) overrepresented amongst these ‘first time group cyclists’. Studying the bikeshare cyclists, or bike share ‘friends’, that individuals make ‘first time group journeys’ with, we find a significantly high incidence (p < 0.001) of group journeys being made with friends of the opposite gender, and for a very large proportion (55%) of members these first ever journeys are made with a friend that shares the same postcode. A substantial insight, then, is that group cycling appears to be a means through which early LCHS usage is initiated.     

桥梁加固分析

通过北票牤牛河大桥加固实例分析危(险)桥的成因及如何确定加固方案.     

歼侦机执行侦察任务前挂载方案预先选取

歼击型侦察机可挂载多种型号的侦察吊舱。在执行侦察任务前，首先要根据任务类型选取最佳的挂载方案。对歼侦机可执行的任务进行深入分析，归纳为高空“普查”和低空“详查”两大类；采用 AHP 和 PROMET HEE 相结合的方法对可选挂载方案进行对比评优，以选择最佳的挂载方案；在两种任务下分别选取三种型号的吊舱进行仿真分析，计算结果与实际情况一致，表明了该方法的有效性。     

Stated choices and benefit estimates in the context of traffic calming schemes: Utility maximization,regret minimization,or both?

This paper proposes a discrete mixture model which assigns individuals, up to a probability, to either a class of random utility (RU) maximizers or a class of random regret (RR) minimizers, on the basis of their sequence of observed choices. Our proposed model advances the state of the art of RU–RR mixture models by (i) adding and simultaneously estimating a membership model which predicts the probability of belonging to a RU or RR class; (ii) adding a layer of random taste heterogeneity within each behavioural class; and (iii) deriving a welfare measure associated with the RU–RR mixture model and consistent with referendum-voting, which is the adequate mechanism of provision for such local public goods. The context of our empirical application is a stated choice experiment concerning traffic calming schemes. We find that the random parameter RU–RR mixture model not only outperforms its fixed coefficient counterpart in terms of fit—as expected—but also in terms of plausibility of membership determinants of behavioural class. In line with psychological theories of regret, we find that, compared to respondents who are familiar with the choice context (i.e. the traffic calming scheme), unfamiliar respondents are more likely to be regret minimizers than utility maximizers.     

High-resolution numerical relaxation approximations to second-order macroscopic traffic flow models

A novel numerical approach for the approximation of several, widely applied, macroscopic traffic flow models is presented. A relaxation-type approximation of second-order non-equilibrium models, written in conservation or balance law form, is considered. Using the relaxation approximation, the nonlinear equations are transformed to a semi-linear diagonilizable problem with linear characteristic variables and stiff source terms. To discretize the resulting relaxation system, low- and high-resolution reconstructions in space and implicit–explicit Runge–Kutta time integration schemes are considered. The family of spatial discretizations includes a second-order MUSCL scheme and a fifth-order WENO scheme, and a detailed formulation of the scheme is presented. Emphasis is given on the WENO scheme and its performance for solving the different traffic models. To demonstrate the effectiveness of the proposed approach, extensive numerical tests are performed for the different models. The computations reported here demonstrate the simplicity and versatility of relaxation schemes as solvers for macroscopic traffic flow models.     

南海深水油气开发海洋工程方案选择策略探讨

深水油气开发的关键是基于油藏数据进行海洋工程方案的选择和确定,建立油藏、流体特性和海洋工程方案关键参数之间的联系是解决油藏和油气井的特性参数的不确定性的良好对策。深水油气开发海洋工程方案要素包括油藏地质和分布、油藏流体属性、钻完井及修井特性和场址特征等。海洋工程方案选择策略是确立功能需求、评价技术约束条件、进行生命周期的经济价值的风险比较和确定作业者的战略主导和其他决策的基本策略。南海深水油气开发海洋工程方案选择策略可借鉴美国墨西哥湾等深水开发经验,选择适合南海海域的浮式平台和外输方案。     

某高速公路隧道仰拱底鼓原因分析及处治方案数值模拟

针对某高速公路隧道仰拱底鼓破坏等病害,从地质因素、支护设计等方面综合分析仰拱底鼓等病害的原因。提出了全面疏通排水设施,采用注浆+锁脚+锚杆加固措施,并运用有限元软件对加固施工过程进行数值模拟,评价处治方案的可行性,为隧道加固提供依据。