独柱墩连续曲线箱梁桥抗倾覆性能评估与加固

为了提升独柱墩连续曲线箱梁桥的抗倾覆能力,确保重载车辆作用下桥梁结构安全,根据现行桥梁设计规范和行业管理部门的技术要求,分析重载车辆下独柱墩连续曲线箱梁桥倾覆破坏的机理,归纳该类桥梁抗倾覆性能评估的内容、要点和加固方法。结合工程实例中桥梁的空间布置和结构受力特点,提出为独柱墩增设盖梁和支承或将独柱墩改为多柱墩的加固方案,并采用梁单元建立了加固前后独柱墩连续曲线箱梁桥抗倾覆评估模型,对各加固方案下桥梁的抗倾覆性能进行了对比分析。结果表明：将独柱墩改为多柱墩的加固方案,能够更有效地提升桥梁的抗倾覆稳定性,加固后桥梁两侧偏载下的抗倾覆稳定系数为加固前的1.73与1.48倍。     

城市独柱墩桥梁抗倾覆加固改造设计探讨

独柱墩桥梁具有结构轻巧、占地少等优点,被广泛应用在城市立交和高架上,近年来,随着独柱墩桥梁倾覆事故频繁发生,独柱墩桥梁结构的稳定性问题越来越受到桥梁管理者的重视。本文结合南京市独柱墩桥梁抗倾覆加固改造的工程实践,对不同桥型进行加固改造方案比选,优化抗倾覆加固设计。     

墩梁固结独柱墩桥梁抗倾覆分析及加固设计

由于独柱墩桥梁采用的是单支点支撑,在汽车偏载的影响下,结构的横向抗倾覆稳定受到极为不利的影响。文中总结独柱墩桥梁倾覆事故的经验,以具体的工程为实例,分析了桥坍塌时桥面荷载的大小以及布载的方式。同时,还根据荷载的大小和布载方式,对独柱墩桥梁的抗倾覆能力进行了分析,介绍了相关的验算方法,并提出了加固设计措施。     

独柱墩弯桥抗倾覆稳定性分析

箱梁独柱墩桥梁是目前我国桥梁结构中运用较为广泛的形式之一。其具有优美的外观,抗扭强度高,整体性能好,视线通透等特点。但是由于独柱墩桥梁抗倾覆能力较差,给桥梁的安全性造成一定程度的影响,因此,在独柱墩桥梁设计过程中,必须对桥梁的抗倾覆进行验算。本文以省道宋长线长岭段改建工程为例分析了现浇箱梁独柱墩弯桥抗倾覆稳定性,并分析具体存在安全问题的原因及解决措施。     

独柱墩连续弯桥抗倾覆性能研究

近年来,因车辆超载和偏载导致独柱墩连续弯桥垮塌事故频发,针对该类问题,对既有独柱墩桥进行安全评估与加固成为研究热点.以某城市立交匝道桥为例,采用Midas Civil有限元软件,对独柱墩连续弯桥抗倾覆稳定性进行验算分析,并结合桥梁结构特点,提出桥梁抗倾覆能力加固措施,以提高独柱墩弯桥的抗倾覆稳定性能,确保桥梁运营安全.     

增设钢牛腿在连续独柱墩桥梁抗倾覆加固设计中的应用

基于独柱墩桥梁的独特优点,在高速公路及市政工程设计建设过程中应用较为广泛,但频发的独柱墩桥梁倾覆事故,亦引发社会各界的广泛关注。以广东某3×20m连续独柱墩匝道桥抗倾覆加固设计为例,通过稳定性验算分析,提出了桥墩增设钢牛腿、改单支座支撑为三支座支撑的加固设计方案。加固效果验算分析表明,三点支撑可有效提高独柱墩桥梁的抗倾覆稳定性。     

超载作用下独柱墩桥梁抗倾覆稳定性分析与加固研究

在重型车辆通过独柱墩桥梁时,易引起箱梁上构横向倾覆。针对广东某高速公路1年内超载车辆分析,确定该段内桥梁汽车荷载效应,划分切合实际的荷载组合,分析验算超载下独柱墩桥梁整体横向抗倾覆性能,并根据验算结果及实际情况,研究独柱墩连续箱梁桥增设支撑体系、设置抗拔销的可行性与合理性,对该类桥的抗倾覆设计提出加固方案。     

中小跨径独柱墩连续梁抗倾覆稳定性分析研究

中小跨径独柱墩梁桥以其简洁经济的优点在中国得到了广泛应用。然而,近年来独柱墩曲线梁桥倾覆倒塌的事故时有发生。基于独柱墩曲线梁桥横向倾覆的机理,根据《上海地区梁桥横向稳定性验算指南》咨询报告的规定,分别从支座反力、抗倾覆稳定系数、梁体转角、下部结构承载能力极限状态四个方面对上海某立交进行抗倾覆稳定验算分析,为上海地区已有的独柱墩桥梁抗倾覆验算提供参考。     

独柱墩直线梁与曲线梁抗倾覆稳定性对比分析

对独柱墩桥梁横向失稳倾覆机理进行分析,综述目前国内外规范针对桥梁上部结构抗倾覆稳定性计算的有关规定。结合某高架桥工程,选取桥梁位于直线段和曲线段的3跨1联（3×30m）,分别对支座反力、支座底部混凝土强度和桥梁抗倾覆稳定系数进行验算,并对计算结果进行对比分析,所得结论对桥梁独柱墩设计具有一定的参考价值。     

独柱墩桥梁纵向单车过桥限载研究

独柱墩连续梁桥在我国城市桥梁中广泛存在。其桥下视野广阔,结构整体性好。但是由于其较差的抗倾覆性能,造成了一定的安全隐患。而随着我国日益严重的超载现象,对于独柱墩桥梁限载计算仍然相对滞后。本文分析了在正常使用极限状态和承载能力极限状态下,独柱墩桥梁纵向单车过桥最大承重,并以略阳互通立交匝道桥为例,具体分析了单车过桥限载,并回顾过去独柱墩桥梁倾覆案例,验证了计算方法的有效性。     

互通式立交出口设计技术问题探讨

针对互通式立交出口可能出现的多种情况,结合工程实践,探讨其设计技术问题,提出设计思路及技术对策,并在技术分析中强调融入“安全至上”“动态设计”“灵活性设计”“宽容性设计”等设计新理念,使出口设计安全、合理.     

水泥混凝土安全护栏

通过水泥混凝土安全护栏在道路交通中的实际应用，对其结构形式和主要参数以及具体的施工方法进行了较为详实的叙述，并对比介绍了水泥混凝土安全护栏的使用效果。     

预应力曲线箱梁和异形箱梁的研究

近年来 ,国内外学者对曲线箱梁和异形箱梁的静力分析理论和计算方法作过大量的研究 ,但这些理论和方法在某种程度上都存在着一定的局限性 ,特别是在实际设计工作中 ,运用起来不能得心应手。为此本文在综合前人已取得经验下 ,针对桥梁结构设计中分析曲线箱梁、异形箱梁 ,经常遇到的难题进行了研究 ,建立一个较为完善的理论和方法 ,编制了等参元空间分析程序。在实际工程中进行实桥试验 ,验证了本文理论和方法的正确性。本文的研究工作更准确描述了箱梁的荷载响应 ,为设计人员提供直观的设计依据。对曲线箱梁和异形箱梁受力特性有了更一步的理解 ,并提出了新的见解     

A model of driver steering control incorporating the driver's sensing of steering torque

Steering feel, or steering torque feedback, is widely regarded as an important aspect of the handling quality of a vehicle. Despite this, there is little theoretical understanding of its role. This paper describes an initial attempt to model the role of steering torque feedback arising from lateral tyre forces. The path-following control of a nonlinear vehicle model is implemented using a time-varying model predictive controller. A series of Kalman filters are used to represent the driver's ability to generate estimates of the system states from noisy sensory measurements, including the steering torque. It is found that under constant road friction conditions, the steering torque feedback reduces path-following errors provided the friction is sufficiently high to prevent frequent saturation of the tyres. When the driver model is extended to allow identification of, and adaptation to, a varying friction condition, it is found that the steering torque assists in the accurate identification of the friction condition. The simulation results give insight into the role of steering torque feedback arising from lateral tyre forces. The paper concludes with recommendations for further work.     

The bricycle: a bicycle in zero gravity can be balanced or steered but not both

A bicycle or inverted pendulum can be balanced, that is kept nearly upright, by accelerating the base. This balance is achieved by steering on a bicycle. Simultaneously one can also control the lateral position of the base: changing of the track line of a bike or the position of hand under a balanced stick. We show here with theory and experiment that if the balance problem is removed, by making the system neutrally stable for balance, one cannot simultaneously maintain balance and control the position of the base. We made a bricycle, essentially a bicycle with springy training wheels. The stiffness of the training wheel suspension can be varied from near infinite, making the bricycle into a tricycle, to zero, making it effectively a bicycle. The springy training wheels effectively reduce or even negate gravity, at least for balance purposes. One might expect a smooth transition from tricycle to bicycle as the stiffness is varied, in terms of handling, balance and feel. Not so. At an intermediate stiffness, when gravity is effectively zeroed, riders can balance easily but no longer turn. Small turns cause an intolerable leaning. Thus there is a qualitative difference between bicycles and tricycles, a difference that cannot be met halfway.     

盾构隧道施工风险与规避对策

归纳地铁安全事故的类型及特点,介绍目前国内外盾构隧道情况,尤其是北京盾构隧道情况,分析盾构隧道施工的优点和不足之处,论述盾构隧道施工风险研究的必要性。重点分析盾构隧道施工的11种主要风险,即：地质预报准确性、盾构机适应性和可靠性、盾构进出洞施工、开挖面失稳、盾尾密封失效、软硬不均且差异性较大地层施工、较大的地层损失及不均匀沉降、开挖面有障碍物、隧道上浮、联络通道施工、明挖基础失稳等,并一一提出切实的规避对策。同时对国内外盾构隧道施工事故典型案例的情况及原因进行详细介绍和剖析。可为今后盾构隧道施工风险的分析、预测、防范及规避提供指导。     

混凝土施工中裂缝的防治措施及处理办法

混凝土的推广使用已有一个世纪,目前在现代工程建设中仍占有重要的地位。而在今天,混凝土的裂缝较为普遍,在桥梁工程中裂缝几乎无所不在,尽管我们在施工中采取各种各样的措施,但收效甚微,裂缝仍然时有出现。该文指出,究其原因,人们对混凝土温度变化所产生的应力注意不够是其中之一,尤其是大体积混凝土。对此,温度应力与温度控制具有重要的意义。     

Analysis of the capabilities of a two-stage turbocharging system to fulfil the US2007 anti-pollution directive for heavy duty diesel engines

This article presents a two-stage turbocharged heavy-duty diesel (HDD) engine designed to fulfil the US2007 anti-pollution directive. This directive imposes very restrictive limits on the NOx and particle emissions of HDD engines. In this work, the possibility of combining particle traps in the exhaust line to reduce soot emissions with very high EGR rates to reduce NOx emissions is considered. This new generation engine implements two-stage turbocharging in order to improve the bsfc when the engine is working on steady conditions as well as to optimize the engine transient response. After carrying out the tests, the results were analyzed and the engine settings were adjusted to maximise its behaviour and minimise pollutant emissions. NOx and soot emission peaks were also analyzed at engine transient conditions in order to keep them under certain levels, and thus maintain the overall pollutant emissions to a level that is as low as possible. In summary, a double-stage turbocharging configuration can greatly improve engine driveability (between 23% and 36% depending on engine speed), while reducing NOx emissions during transient evolution without increasing opacity peaks beyond the stated limits.     

高速公路车辙与裂缝解决过程中的误区及对策

目前国内为了片面地提高路面强度来解决抗车辙能力,在沥青混合料原材料选用和组成设计中存在着误区,出现了其它质量问题。通过误区的提出和解决对策的探讨,期望能对公路设计者、建设者和养护者们提供一些参考,减少公路病害,降低养护成本,提高公路使用质量。     

汽车悬架板簧变形运动分析

分析板簧垂直跳动的变形运动轨迹和纵扭变形运动轨迹,为转向拉杆布置提供参考,从而减少制动跑偏。