Analysis of Low frequency Noise of Bridge Considering the Vibration of Bridge Deck

Under the dynamic load of vehicle, the bridge will vibrate and radiate low frequency noise which is harmful to human health. A method for predicting the low frequency noise is proposed based on the analysis of vibration of bridge deck. The prediction includes the analysis of vehicle bridge coupling vibration considering the bridge deck and the analysis of sound radiation and propagation in the air. By taking a bridge with low frequency noise as example, the vibration and sound radiation of the bridge are analyzed respectively by the current method and the previous method based on the grillage model. The results show that the prediction based on the vibration of bridge deck is more accurate. Furthermore, the measures to reduce the noise of bridge are explored, and the results indicate that a smoother road surface leads to lower noise. But when the condition of road surface is up to the extremely good standard defined by ISO, the effect of reducing the roughness of surface is not significant. Also, strengthening the crossbeam in the bridgehead is a simple and effective way to reduce the low frequency noise of bridge.     

Wind Tunnel Tests of Long Span Half - through Arch Bridge Section Model

Wind induced vibration is one of the main control factors in the Long span bridge structure design. The wind tunnel tests for measuring the static wind forces on the bridge girder and the section model wind tunnel dynamic testing for Caiyuanba Yangtze River Bridge in Chongqing are introduced in this paper. The wind tunnel testing for measuring static wind forces and vortex- induced vibration test on the arch are introduced taking account of the influence between two arches. The main contents and outcomes of testing are presented. It is indicated that the bridge girder has excellent wind stability and the arch mechanical characters are rather complicated. The drag force on the hind arch varied a lot because of the font arch interference on the wind flow. The drag force on the hind arch will be negative when two arches are close to each other. It increases with the space of two arches. The results of testing will give the data of buffeting and vortex - induced vibration and flutter analysis of the bridge.     

Computer simulation of all terrain vehicle vibration performance

In order to assess the vibration performance of all terrain vehicles, a half vehicle model with 10 degrees of freedom was built. The model was solved using the time domain method. Road surface irregularity excites the model and was generated by a trigonometric function. Based on this model, the beaming of the frame was analyzed. The results show that the first beaming and second beaming influence the vibration significantly. As a result, a half vehicle model that includes the first two beamings of the frame can satisfy the vehicle vibration analysis precision requirements. Driver ride quality was evaluated according to ISO2631 1.     

Operational Bridge Responses due to Road Surface Profile Spectral Excitations

Random spectrum excitation samples of a road surface profile are investigated. The displacements, velocities, accelerations of a vehicle and a bridge structure are discussed using certain samples. The road excitations are numerically simulated by the random phase cosine method of the power spectral density. The vehicle bridge system responses are obtained using the vehicle bridge differential equations for different road surface profiles. It is concluded that the random phase has critical effects on the road surface profile curve shape, and the power spectral density on the curve value. The random samples possesses the same statistical characteristics. The system response values are affected more by the road surface profiles, and the response shapes are affected more as the vehicle velocity varies. Some engineering advice is proposed based on the numerical calculation with the different random excitation inputs for their significant differential responses.     

大攻角及桥面粗糙度对扁平钢箱梁涡振性能的影响

为探究大攻角及桥面粗糙度对扁平钢箱梁涡振性能的影响,对寸滩长江大桥主梁进行了风洞试验。应用Matlab软件模拟桥面粗糙度变化范围,根据模拟结果选取对应的砂纸在试验中模拟桥面粗糙度,分析了攻角及桥面粗糙度对扁平钢箱梁涡振区间及幅值的影响。试验研究表明:在大攻角下扁平钢箱梁的涡振振幅和范围明显增大,对桥址位于山区等容易发生大风攻角的地区的桥梁应进行大攻角试验。扁平钢箱梁的涡振响应随着桥面粗糙度增大而减小。正攻角范围内,桥面粗糙度对涡振响应的影响随着攻角减小而增大。桥面粗糙度发生变化时,扭转涡振响应更加敏感,变化幅度大于竖向涡振响应变化幅度。     

Numerical Model of Temperature Field in SMA Asphalt Road Surface of Steel Box Girder Bridge

When paving SMA asphalt road surface, the temperature factor must be thought over which infects life-span of road surface. Winter and summer temperature distribution on a steel box girder bridge is simulated, compared with data measured on EGongYan Bridge in Chongqing and HaiCang Bridge in Xiamen. A change range of high road surface design temperature suit to China is given.     

Analysis of vibrating characteristics of multi-span continuous skew bridges

To explore the vibrating frequencies and rational impact factors of multi-span skew bridge, the recursive algorithm of vibrating frequency and finite element formulations of static and dynamic analysis are established for uniform section multi-span continuous skew bridge. The first five order frequency changes of equal-span multi-span continuous skew bridge and unequal-span multi-span skew bridge are compared. The interaction of vehicle-bridge system for two-span skew bridge is analyzed. The history curves for deflection and moment of middle-span are presented. The influence of obliquity on dynamic deflection and dynamic moment as well as the influence of vehicle velocity and obliquity on impact factors of deflection and moment are investigated. Results show that the fundamental frequency of multi-span skew bridge is identical to that of single span skew bridge. The higher order frequencies of single span skew bridge are distributed in frequencies of multi-span skew bridge, which mix other vibrating frequencies. The more the span number is, the more the other vibrating frequencies mingle. Obliquity has an important influence on dynamical characteristics of skew bridge. Impact effects of vehicle have no harmonious changing rule with vehicle velocity and obliquity. The impact factors of deflection and moment are different for skew bridge.     

Time Domain Analysis on Buffeting of Jinma Bridge

Jinma bridge is a long span cooperative-system cable-stayed bridge with one tower cooperated with T frames on both sides.Owing to artistic form and lying in typhoonprone area,it is essential to process the buffeting analysis.In this paper,the turbulent wind velocity was first simulated with cosine wave superposition method as multi-correlated random processes;then,the time domain expressions for the buffeting and self-excited forces were given.On this basis,the buffeting analysis of Jinma Bridge was made.The results show that the anti-wind capacity of the cooperative-system cable-stayed bridge is ensured although the torsional resistibility of the main girders of this bridge is not good.     

现代桥梁雷击灾害风险研究

开展雷击灾害风险评估,选取最合适的雷击灾害防御方案,是防止和减少因雷击桥梁产生灾害损失的重要手段,也是进行科学防雷的重要前提,借助安徽省气象局ADTD型闪电定位系统监测的2006—2013年逐日闪电数据,应用IEC 62305规范以及GB/T 21714国家标准,对安徽省马鞍山市长江大桥进行雷击灾害风险研究。结果表明：人身伤亡损失风险主要由直接雷击大桥导致的接触、跨步电压和物理损害引起;经济损失风险主要由直接雷击大桥导致的物理损害以及直接雷击和邻近雷击导致的大桥内部系统故障引起;比较大桥在无LPS、LPSⅢ和LPSⅡ三种设定方案下雷击灾害风险值,确定针对马鞍山长江大桥最优化的雷击防御方案二来降低人身伤亡损失风险和经济损失风险值。该风险评估部分成果在马鞍山长江大桥建设中得到实际应用,项目达到防雷要求并暂未出现雷击灾害事故。     

Temperature Effect Analysis of Chongqing Shibanpo Yangtze River Double Line Bridge

Thermal stress is one of the important influence factors of crack and deformation for large-span bridge structures. Grounded on Shibanpo Yangtze River double line bridge and universal finite element program MIDAS-Civil with referring to specifications of China and British BS5400, above all, it is for this Bridge that the stress and deformation influence is studied by setting section temperature difference and system temperature change, afterwards, the effect on the newborn bridge is discussed by combining impact of the section temperature difference and the system-calefaction linearly , and then, the effect is compared with the impact brought by moving load. The results will have a certain extent value for the design of ShiBanpo double line bridge and other similar bridges.     

Construction Technology for the Main Bridge Pier of Citong Bridge in Quanzhou City

The Citong Bridge is located in the river estuary section with 4 meter tide range and mixed geological structure. In this paper, the technique for construction of the main bridge pier was presented in detail, which consists of the construction process, technological requirements, main construction parameters and amendment on defects. It is of great value for reference to the similar works.     

Fiber Fabry-Perot Sensor and Its Application for Monitoring Bridge Strain

The strain is an important parameter that reflects the bridge health status, the fiber Fabry-Perot sensor is embedded in the concrete structure as the intelligent sensing element for the bridge strain. The strain measuring system is made up of the fiber Fabry-Perot sensor,light switch,fiber strain gauge and the comput- er; it can be used to monitor automatically the bridge strain. At present,the system has been installed in the Dafosi Bridge over the Yangtze River in Chongqing. The monitoring data show that the fiber Fabry-Perot sensor has good stability and reliability; it can be used to monitor the bridge strain for a long time.     

Lateral Load Capacity Analysis of Variable Section Hybrid Piles with Wteel Casing

With the construction of deep-water bridge foundation, steel casing is left after the construction of cast-in place piles due to the dismantle difficulty. Then the pile actually forms a variable section pile which has bigger section area at upper part. Using the nonlinear NL method, the displacement and the internal force are analyzed for piles with and without casing in Sutong Bridge. It is found that the displacement of pile with casing can be reduced by 50%, and it can not be ignored for accurate calculation of displacement. 8 model pile tests are carried out, which suggests that the slurry thickness can significantly affect the capability of co-working between the pile and the casing.     

Research on Bridge Structure Noise of Railroads and Underground

This paper analyses the generating mechanism of radiation noise which produced by bridge structures and vibro-acoustic characteristics, and reviews the current situation of the researches on the relevant standards of structure noise at house and abroad. The author summarizes the method of measurement and calculation about structural noise at house and abroad, further notes their limits. This paper explores the impact of such factors as rain speed and other different fluids on structure noise. The noise characteristics of structures like cavity structure and thin-slab structure are also discussed. Strategies for reduce the bridge structure noise are summed up by reducing the vibration of track structure, altering the structure of boundary conditions, increasing the stiffness and changing the bridge cross section. Finally it comes to a conclusion that a combination of these strategies is the root way to settle the question of the bridge structure noise.     

北京市平谷区“生态桥”治理工程废弃物资源化利用和运行模式研究

“生态桥”治理工程是北京平谷区针对桃树枝废弃物资源化利用而提出一套废弃物资源化利用和乡村治理的模式,对于破解乡村环境治理困境具有重要意义。本研究分析了“生态桥”治理工程废弃物资源化利用和运行模式特征。结果表明：“生态桥”治理工程通过堆制有机肥、食用菌栽培、制作栽培基质和地表覆盖物等资源化利用方式,打造桃树枝废弃物良性生态循环模式。在运行模式上,“生态桥”治理工程建立投融资平台,统筹资金使用与投入方式,建立起财政资金有效使用和管理办法,激发企业投入农村环境治理的动力,保障农民全员参与的机制。通过“生态桥”工程设施,吸引社会资本进入乡村环境治理领域,有效改善环境质量,推动乡村生态环境建设投融资机制改革,提高了乡村生态环境综合治理水平,是一种有效的乡村环境治理模式。     

Computer Aided Roll Collection Management System for Roads and Bridge

The application of Computer Aided Roll Collection Manage System for Roads and Bridge will ease workers and reduce leak of management,corruption farthest. It can improve manage level and work efficiency. It also can reduce traffic jam. This system adopts the technology of vehicle model recognition based on neural network, IC card, automatic recognition of bill based on OCR and transfer of compressed vehicle image. The technology of this system is advanced. This system has high reliability and durability and convenient.     

Research of Structure Optimization Design for Ten Mile River Landscape Bridge

Guiyang Huaxi district landscape bridge is seven miles the beach driving bearing type reinforced concrete box arch bridge, the design process of conventional arch bridge solutions with less thrust arch bridge to carry on the comparison, the combination of special terrain, geological conditions, finally chose the foundation excavation is small, economical, reasonable structure, less thrust of arch bridge using edge inclined rod and bearing platform consolidation, forming the free cantilever end method better solve the horizontal thrust at arch feet larger, by establishing the structure finite element model, analyzes the static force performance, the results show that the thrust of arch stress performance good, less economically feasible, beautiful appearance, and the scenic spot environment more harmonious.     

Monitoring and Assessment of Tie on the Caiyuanba Yangtze Bridge

The monitoring and assessment scheme of the Caiyuanba Yangtze Bridge is present by sensitivity analysis. The mechanics character of the six ties is studied by numerical simulation, and then the sensor location and selection are discussed considering the technique of sensor and construction situation. The trend of the displacement at the sensor location is analyzed according to different damage level of ties, the pattern associating with several displacements which are sensitive to damage at ties is bring forward to improve assessment reliability. The result can assist implement of structural health monitoring system to the same type as this bridge.     

Stress Measuring during the Construction Monitoring of Weisheng River Bridge in Guangzhou

In this paper,the simulation calculation of Weisheng River Bridge was firstly conducted.Based on it,the measuring points and methods for stress measuring and calculation approach for real stress were introduced.The measured results matched the calculated results very well.Stress measuring during the construction monitoring can serve as references and guides of the structural situations during the different bridge construction process.     

基于MODIS-NDVI时序数据的南方冬闲田信息提取

为了从宏观上监测冬闲田的面积及分布情况有效解决传统方法的时效性差的缺陷,以MODIS-NDVI时间序列数据、土地利用数据和湖北省农业统计数据为基础,得到2007年4月到2008年3月湖北省MODIS-NDVI时序数据变化曲线。由于遥感影像在传输过程中受到云、大气等的影响,曲线的变化与统计数据的物候期并不完全符合。为了如实反映地表事物的真实面貌,本文采用Savitzky-Golay滤波进行平滑去噪处理,并将结果与ERDAS中自带的Hanning滤波去噪的结果进行比较,发现前者效果较好,不仅能有效去掉噪声,不产生环形条纹,而且能最大程度地保留细节特征。根据变化曲线所反映的物候信息,最后得到湖北省冬闲田的总面积为5564.3平方千米,即834.6万亩,占耕地总面积的16.6%,主要分布在鄂东南低山丘陵和江汉平原地区,冬闲期主要有60天和120天两种。