Influence of concrete differential aging time on the construction phases analysis of the Fenghua River Bridge

The Fenghua River Bridge is a major structure on the highway between Hengzhang and Guojiachi, which is to be built with a four-span prestress concrete (PC) box girder and symmetrical cantilever castings. In this paper, a finite element method (FEM) model is set up to study the effects of concrete differential aging time on the construction phases of the Fenghua River Bridge by calculating the vertical displacement of the folding segment of the middle span and the longitudinal bending moment of Pier 12#. In the model, the girders are classified into 150 changing sections based on the desgn scheme, and their construction is to be carried in 16 phases respectively to build 12 blocks connected by a side folding segment and a middle folding segment, covered with a second dead load and in completion for 20 years. It is found that the internal forces and deformations of the concrete structures at the aging time of 60 d are quite different from those of 0 d aging time while the behaviors of the structures of 120 d aging time is nearly the same as those of 60 d aging time― the differences are so small that can be neglected, suggesting that the creep develops obviously about one month after the cement is hardened and the development fades later on.

Simulation Analysis on Navigation Indexes of Wanzhou Yangtze River Highway Bridge after the Anti-Collision Device Construction by Ship Model Test

After the anti-collision facility construction of Wanzhou Yangtze River Highway Bridge, the conditions of navigation in bridge area are complex. In order to study the navigation conditions of the reach and layout optimization measures, ensuring the safety of the ship navigation test has been carried out on the ship model navigation in the bridge area. According to the requirements of the maximum safety limit of the ship model test, the paper puts forward the best route, the control method and the difficulty of navigation through the analysis of the test results, and finally gives the recommendations and suggestions.

HY-1C Coastal Zone Imager observations of the suspended sediment content distribution details in the sea area near Hong Kong-Zhuhai-Macao Bridge in China

The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coastal Zone Imager(CZI)and Chinese Ocean Color and Temperature Scanner on it.A new SSC inversion model was established based on the relationship between in-situ SSC and the remote sensing reflectance in red and near-infrared bands of CZI image.HY-1C satellite data obtained from October to December 2019 were applied to retrieve SSC in the Zhujiang River Estuary.The results show that SSC around the HKZMB is ranging from 20 mg/L to 95 mg/L.SSC change obviously on two sides of the bridge.During flooding and ebbing period,SSC increases obviously downstream of the bridge.SSC difference between upstream and downstream is ranging from 5 mg/L to 20 mg/L.Currents flowing across the HKZMB,the change trend of SSC in most places upstream and downstream is almost the same that SSC downstream of the bridge is higher than SSC upstream.The tidal currents interact with bridge piers,inducing vortexes downstream,leading the sediment to re-suspend downstream of the bridge piers.Other factors,including seafloor topography and wind,can also contribute to the distribution of SSC in the Zhujiang River Estuary.

Design of steel box girder for Taizhou Yangtze River Highway Bridge

Taizhou Yangtze River Highway Bridge is the first three-pylon two-span suspension bridge in China. The main girder adopts flat steamline steel closed box girder which has well wind-resistant capability and is technically mature besides beautiful appearance. Straight web plates of the steel box girder in longitudinal direction are proposed in order to ensure the integrity of the steel box girder, and to keep the stress of the steel box girder continuous in the middle pylon, as well as to reduce the gradient of the middle pylon columns. The cross section of the box girder has one box with three cells. Solid-web diaphragm plate with good integrity and high torsional stiffness is adopted. The lifting lugs are utilized in the anchors of suspender cable. In this paper, selection of the cross section of the steel box girder, the general structure design, local structure design and main structure calculation results of Taizhou Yangtze River Bridge are introduced emphatically.

THE BLACK RIVER BRIDGE BRINGING PROSPERITY TO LOCALS

'In the past, people always crossed the river by boat and would risk their lives doing it,' says Norbu Tashi, a villager from Xia in the town of Nenwa, Zoige County, as he observes the new Nenwa-Xiaman Bridge.'People have benefited a lot from this new bridge. It’s more convenient for cows, sheep, horses, and people to cross over, and it saves us trouble and worry while we’re busy going about our daily lives.'

Key Technologies for Design of Changqing Yellow River Super-long Bridge of Zhengzhou Ji'nan HSR

Changqing Yellow River Super-long Bridge of Zhengzhou-Ji'nan HSR is a partial cable-stayed bridge with concrete main girder and a unit length of 1,080 m.Studies are carried out on the key technologies of bridge design,and the main conclusions are as follows:The whole unit adopts the supporting system of tower pier consolidation and tower-beam separation,and each pier is provided with seismic mitigation and isolation bearing;shaped-steel reinforced concrete bridge tower is adopted to bring into full play the tensile performance of steel and the compressive performance of concrete,and avoid the construction challenges of setting up multi-layer and multi-stirrup reinforcement while improving the bearing capacity of section;a new type of double-side and bi-directional anti-skid anchorage device is adopted for the cable saddle of wire divider pipe in order to withstand the unbalanced cable force,and verify the reliability of the anti-skid anchorage device by solid model test;and large-segment cantilever pouring design is adopted for the main girder with a maximum segment length of 8 m to effectively shorten the construction period of the bridge.

Structural safety monitoring for Nanjing Yangtze River Bridge

In order to evaluate objectively and accurately the integrity, safety and operating conditions in real time for the Nanjing Yangtze River Bridge, a large structural safety monitoring system was described. The monitoring system is composed of three parts: sensor system, signal sampling and processing system, and safety monitoring and assessment system. Combining theoretical analysis with measured data analysis, main monitoring contents and layout of measuring points were determined. The vibration response monitoring was significantly investigated. The main contents of safety monitoring on vibration response monitoring are vibration of the main body of the Nanjing Yangtze river bridge, collision avoidance of the bridge piers, vibration of girders on high piers for the bridge approach and earthquake. As a field laboratory, the safety monitorying system also provides information to investigate the unknown and indeterminate problems on bridge structures and specific environment around bridges.

The New Arched Bridge over Dnipro in Kyiv

The Podilskyi Arch bridge is crossing the Dnipro River in center of Kiev and is part of a 7.4 km long link which connects the center of Kiev with the “sleeping district” on the left bank of the river. The bridge has a main span of 344 m intended for six lanes of vehicles in the top level and two metro lines in the bottom level plus large diameter water pipes. The bridge is of steel, except of the reinforced concrete bases of the lower parts of the arches. The draft design works began in 1991 and in 2005 parallel design and construction work started. Due to the financial crisis in Ukraine, the work was interrupted for several years but construction recommenced in 2018 and the bridge is now planned to be completed in 2020 and the first stage of the transition in 2022.

积石山6.2级地震桥梁典型震害特征

调查了306省道、310国道以及川亭公路上位于地震烈度8度和7度区的桥梁。GS.N0028台站记录到的大河家镇加速度峰值超过900 cm/s~2,远超当地罕遇地震设防标准,但从调查的结果看,本次地震中,8度区的桥梁震害主要以轻微破坏为主,包括挡块破坏、主梁侧移和支座滑移,除了川亭公路上发现一桥梁的桥墩出现剪切裂缝外,其他桥梁未发现主体结构发生破坏。7度区的桥梁基本完好,橡胶支座中橡胶有变形无法恢复以及主梁位移导致挡块间距发生变化,但都不影响功能。混凝土挡块作为主梁防侧移装置,震害虽然表明其有效性,但缺乏快速恢复的特性,同时设置缓冲橡胶垫的挡块仍然发生了较严重的破坏,因此,以后需要进一步加强挡块的缓冲装置和考虑可快速恢复性能的研究。

基于无剪力钉体系的RBPC钢桥面铺装技术及其应用

为探索长大桥钢桥面全寿命周期养护新技术,解决现有钢桥面铺装及正交异性板疲劳损伤的难题,开展树脂连接型超高性能混凝土RBPC铺装技术研发工作。研究结果表明:相比同条件环氧类EA铺装结构,RBPC铺装下钢板应力减少约40%,提升钢桥面结构刚度50%以上,验证此铺装结构对正交异性板具有一定刚度提升和补强效果;使用缓粘接湿粘接剂代替栓钉粘接防水抗滑层(RBChip)的新工艺,接触方式由“点”改“面”,便于后期维修养护,且全国首次在长江公路大桥铺装重置工程中成功应用。

跨河桥梁河道段整治工程设计方案研究

公路或者铁路等交通线路跨越河道交叉工程规划的是否合理,关系到工程的投资以及协调、施工和管理的难易程度,也关系到工程能否顺利推进。在公路桥桥墩难以避开河道条件下,根据堤线布置原则,结合河道水流条件和协调难度等因素,坚持少征地或不征地,在保证河道行洪能力前提下,对不同河道堤线和断面型式进行了比选,提出最优设计方案,为类似工程提供借鉴。

资江流域江水DOM三维荧光特征及其对锑迁移的指示意义

溶解性有机质(dissolvedorganicmatter,DOM)是影响重金属元素在水体中迁移转化的关键因素之一。资江是洞庭湖第三大支流,流域内锑矿开发导致资江江水中锑(Sb)的质量浓度处于较高水平。为了解析资江流域江水中DOM的特征及来源,探索DOM对Sb迁移的指示意义,研究对资江流域江水进行了三维荧光光谱分析,利用平行因子法分析了水体中DOM的组分和荧光特征以及各组分与Sb质量浓度的关联。结果表明:(1)资江流域江水中Sb质量浓度为1.50~62.20μg/L,平均值为7.26μg/L,其中有55.56%的采样点Sb质量浓度超过最低限制5μg/L;(2)资江流域江水DOM有C1、C2和C3共3个组分,依次为陆源的类富里酸组分、类腐殖质组分以及可作为电子运输工具的醌类腐殖质组分,以C1和C2组分为主;(3)DOM主要通过2种方式影响Sb的迁移,一是水体中DOM的醌类基团作为电子传递体并参与有机质的氧化及铁氧化物的还原,二是富里酸基团与Sb进行络合形成DOM-Sb型复合物,2种方式协同促进了资江流域江水中Sb的富集,提高了Sb的迁移能力。研究结果将为资江流域江水Sb污染溯源和防治提供新的方向和理论依据。

长江下游桥区动态自适应自主航行决策方法

针对长江下游桥区环境复杂且时变,存在特殊航行规则、可航水域受限等问题,提出一种自主航行决策方法。在该类水域,基于数字化交通环境模型,结合导航模型、船舶操纵运动数学模型(MMG)、航向航迹控制方法构建自动航行模型。以航行规则和良好船艺为前提计算可行操纵区间,依靠时序滚动框架消除剩余误差和自适应目标船(TS)机动,求取自主航行决策方案。仿真结果表明:该方法能自适应时变环境,实现自适应多目标避让,并沿推荐航线安全通过,为桥区水域自主航行提供一种自适应的决策方法。

船舶撞击内河桥梁下部结构力学特性研究

为研究内河桥梁下部结构在船舶撞击下的受力特性,依托安康市汉江一桥,开展水平冲击荷载作用下的单桩冲击力室内模型试验,在通过室内模型试验结果验证数值模型有效性的基础上,建立汉江一桥下部结构模型,研究分析其受船舶撞击下的船撞力、位移及损伤特性。研究结果表明:船桥碰撞产生的船撞力可分为直接撞击阶段与残余力撞击阶段,船桥碰撞问题的研究可仅采用直接撞击阶段;桥梁下部结构的刚度越大,船桥碰撞的接触时间越短、船撞力峰值越大;船舶撞击桥梁下部结构不同位置的最大位移变形主要出现在各部件的连接处,桩基的中性点主要出现在桩顶附近与桩身下半段;进行桥梁下部结构防撞设计时,应重点关注桥墩与承台连接处,承台与桩基连接处的强度问题。研究结果可为内河桥梁的防撞设计与相应的规范规程提供参考。

湖南省资江流域娄底段的锑污染和成因分析

湖南省锑矿资源丰富,全省锑矿采、选、冶主要集中在资江流域,因历史遗留问题,资江流域锑污染问题较为突出,本文通过连续监测典型断面(水厂取水口断面)及水库数据,运用了等数值计算法、推算法等方法,研究了本次事件娄底市入资江干流的锑污染物(Sb)总量及其原因。结果表明,(1)本次事件排放锑总量7.575吨,全部流入资江干流;(2)本次事件发生的原因如下:①资江流域锑本底值高;②近期极端天气叠加影响。本研究成果可为后期资江流域水环境治理和质量管理决策提供科学依据。

冰盖下桥墩局部冲刷新型防冲组合结构试验研究

河流冰盖的形成改变了桥墩周围的水力特性,导致桥墩局部冲刷加剧。基于动床冲刷,在冰盖及明流条件下进行了螺纹式减冲索与钩环式护圈组合的新型防冲结构室内模型试验,探究其对桥墩局部冲刷的防冲效果。试验结果表明:新型防冲组合结构改变了桥墩的局部冲刷模式,延缓了冲刷过程;通过极差分析与方差分析可知,螺纹直径为6.0 mm、螺纹角为15°、螺纹排数为3的新型防冲组合结构的防护效果最优;与无防护工况相比,在粗糙冰盖条件下新型防冲组合结构桥墩最大冲刷深度减小了59.03%;螺纹式减冲索增大了桥墩表面的粗糙度,可以更好地削弱下潜流和分离墩前迎面水流,从而达到有效防冲的目的。

甘沟河特大桥关键施工技术研究

为解决大跨度连续钢构桥挂篮悬臂施工时的桥梁线型控制和挂篮稳定性问题,依托炉红山至慈利高速公路TJ1标甘沟河特大桥项目,运用连续钢构桥梁线性控制系统对挂篮悬浇施工线形控制进行监测,并运用数值模拟手段对施工阶段挂篮主构架进行受力和变形计算。研究结果表明,挂篮悬浇施工时,17号墩上部连续钢构桥线性大致呈单峰“抛物线”型,经过实际数据采集后,现场梁段的位移与理论值呈现不同程度的偏差,位移偏差范围为–0.956~0.954mm,控制在1.0mm的误差范围内,表明基于连续钢构桥梁线性控制系统的施工控制技术可起到了良好的变形控制效果;挂篮悬臂浇筑阶段,挂篮三角形主构架的前点竖向位移为7mm<20mm,其变形满足要求;主构架杆件的最大应力是49.7MPa<205MPa,其应力满足要求。

陇海铁路伊洛河桥改建工程与防洪的探讨

伊洛河作为黄河重要支流,历来灾害频发,而陇海铁路伊洛河桥处于伊洛河泄洪卡口处,对偃师夹滩地区防洪安全造成严重威胁。通过对区域防洪形势及陇海铁路伊洛河桥现状问题进行分析,结合规划、既有铁路现状、设计时速、征拆等因素,提出陇海铁路改线新建铁路桥的方案,并对桥梁建成后与黄河下游防洪的相互关系进行分析,提出应在协调好伊洛河流域和黄河下游防洪关系的基础上再行开展改建工程,对下一步工作的开展提供了有益参考。

河流水质自动监测站取水平台优化设置技术要点与案例

水质自动站是获取水环境质量数据的重要手段。国家相关标准对于水质自动站站址选择做了原则性的规定,但是自动站取水口受河道冲淤,人类活动的影响,可能影响监测结果的代表性和准确性。本文介绍了自然河流水质自动站取水平台优化设置的技术要点:自然河流水质自动站站址选择尽可能选择顺直或尽可能不受冲淤影响的河段、取水平台位置的99%水位保证率下水深不小于1m、流速不小于断面平均流速的30%。以阿七大桥水质自动站为例,分析了取水平台受下游电站运行和河道冲淤对取水平台获环境的影响,明晰了获取水样代表性不足的原因,提出阿七大桥断面取水口位置优化建议。