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.     

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.     

Transverse Seismic Design and Analysis of an H Type Bridge Tower Cable Stayed Bridge

According to our current bridge seismic design codes, the bridge tower is explicitly required to remain almost elastic even under the excitation of occasionally happened earthquake. To achieve this seismic performance objective, usually the steel ratios of tower base and strut are required to satisfy the static loading demand and increase by a large margin as well in most engineering practices which leads to engineering inefficiency as well as a rising seismic demand for the substructure. Therefore, the structural design parameters including the location, the stiffness and the constrain condition of the strut with respect to the tower column of H shape tower were studied to explore their effect on the transverse seismic responses of cable-stayed bridge tower, Moreover, the effect of yield intensity of the strut on the seismic responses of the tower column is also studied. The results show that the location and the stiffness of the strut have a slight effect on the seismic responses while the transverse seismic demands of the bridge tower decrease drastically when the constrain condition between the cross beam and the tower column changes.     

Research on Seismic Behavior of Top-bear Arch Bridge with Viscoelastic Damping Braces

This paper proposes a new method of structure control that to set damping braces in a top - bear arch bridge. Lumped damping can be introduced to structures to reduce seismic response. The FEM analysis of Nimu bridge which is braced with viscoelastic dampers had done. The results show that the viscoelastic damping braces can remarkably decrease displacement within the arc plane, which is an efficient structure control method.     

Nonlinear Aerostatic Stability of Suspension Bridge with Spatial Main Cables

The three component coefficients of section model of You Cha Bridge were obtained by using two five component balances.And the three dimensional aerostatic stability of You Cha Bridge was analyzed based on the modified increment and inner outer iteration method implemented in ANSYS.It is indicated that the aerostatic stability of You Cha Bridge with spatial main cables is more excellent compared with those of suspension bridges which have two parallel main cables.A full aero elastic model with geometrical scale of 1:90.35 was designed and used to experimentally determine the wind velocity inducing aerostatic divergence in smooth wind.And it is found that the critical wind velocity for attendant bridge is higher than the design wind velocity.     

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.     

Transverse Effect of Bottom Continuity Tendons in Continuous PC Box Girder

Bottom continuity tendons induce transverse additive effect while providing longitudinal compression during the construction of PC box girder. Taking a cross-sea bridge for example, the mechanism of bottom continuity tendon is investigated. The transverse effect and parameters study are conducted through a refined model. It is illustrated that the state of bottom flange is in a dynamic changeable process during the tensioning of bottom continuity tendons, and the transverse effect caused by the tendons is much more than that by dead loading and other prestressing tendons. The transverse effect is more sensitive to alignment and thickness of the bottom flange, as well as concrete cover of the ducts. Finally, based on the simplified frame analysis, the design method is proposed by introducing prestressing effect simplified factor and duct modified factor.     

Comparisons of Methods for In-Plane Bearing Capacity Calculation of Two-Hinged Parabolic Steel Arch Under Full-Span and Half-Span Loads

The internal force would vary largely with different load ratio for steel arches under combined full-span with half-span loads. However, most relevant formulas on in-plane stability capacity of steel arches were obtained by studying the stability under a single load. Thus, it lacks full considerations of the applicability of bearing capacity formulas under a combined full-span load with half-span load. To overcome this shortcoming, the two-hinged parabolic steel arch was used to compare the results of bearing capacity of arches with different load ratios, rise-span ratios and sections calculated by several methods, The method proposed in the current Chinese design specification of steel arch structure and the finite element method based on the perfect arch and the consistent imperfect arch were included. The results showed that the method in the specification for designing a steel arch would be conservative with a large ratio of the full-span load to the total loads while unsafe with a large ratio of the half-span load to the total loads.     

Experimental and Numerical Analysis on Rupture of Rock Bridge with Non-Coplanar Intermittent Joints Under Direct Shear

By using servo control shear loading system, specimens with non-coplanar rock-like intermittent joints were tested by the way of forward and reverse direct shear, rupture mechanism and shearing law for rock bridge with non-coplanar intermittent joints were studied under direct shear. The experimental studies showed that five apparent stages are presented in the process of rock bridge rupture under direct shear, which are linear elastic stage, initiation and extension of crack, fracture and transfixion of rock bridge, climbing and occlusion of shear plane and residual friction. Rock bridge presented profile fracture plane under forward direct shear. While under reverse direct shear, band form fracture plane is showed which penetrated along with the direction of forward shear, and the shear strength of initiation and peak shear strength under reverse direct shear are bigger than that under forward shear. Crack angle, normal stress and lap proportion among adjacent joint are the main factors that influence the initiation strength and peak shear strength. The FLAC 3D simulation for the process of non-coplanar intermittent joints rock bridge rupture and formation of shear rupture surface under forward and reverse direct shear was conducted. The results of numerical simulation agreed well with those of experiment. The simulation results revealed tension crack failure of non-coplanar intermittent joints rock bridge and shear yielding mechanism of fracture plane.     

Analysis of Vehicle-Bridge Coupled Vibrations for Simply Supported Girder Bridge Considering Bridge Surface Roughness

Bridge surface roughness is usually considered to be the main Influencing factors of vehicle-bridge coupled vibrations.The way that obtaine Bridge surface roughness by the transformation of power spectral density is effective and rapid.The Bridge surface roughness is obtained by Fourier inverse transform method and trigonometric series method respectively. It can be concluded from the comparision that the precision of Fourier inverse transform method is higher than trigonometric series method. The vibration functions for 4-dofs Vehicle and bridge were derived with the employment of d'Alembert principle and computational procedures for vehicle-bridge coupled vibration were compiled. The dynamic response of a simply supported beam and vehicle was analyzed considering bridge surface roughness which was obtained by Fourier inverse transform method.The research shows that the influence due to the bridge surface roughness is significiant and vehicle speed also effects the bridge vibrations by changing the frequency of the force acting on the bridge due to vehicle and the force acting on the vehicle due to bridge deformation.     

Seismic Performance and Failure Process of Long-Span Bridge With High Piers

Based on OpenSEES platform, elastic-plastic structural model of long-span bridge with high piers is established. This paper utilizes time-history analysis method to analyze seismic responses of bridge under consistent or multi-support seismic excitation. Seismic performances and failure process for bridge with high piers are studied. Analysis results show that characteristics of seismic excitation and the way of excitation input have some effect on failure sequence and the occurrence or location of plastic hinge for bridge piers. The failure mode for high piers assumes bending failure, and the failure for top of pier is frequently prior to that of pier bottom, which should be paid enough attention.     

Effect of Marangoni Number of Liquid on Marangoni Convection in Liquid Bridge

The physical and mathematical model of the Marangoni convection in liquid bridge with liquid encapsulation (or two immiscible coaxial liquid columns ) are established. A numerical simulation of the Marangoni convection in liquid bridge with liquid encapsulation is performed by employing vorticity-streamfunction method and the Alternative Direction Implicit scheme in finite difference. The distribution of temperature and flow in two liquid columns are then obtained. The influence law of Ma number of liquid encapsulation to the Marangoni convection in liquid bridge with liquid encapsulation is obtained.     

Optimization Algorithm Research on the Arch Axis of Steel Box-Concrete Composite Arch Bridge

The paper proposed an innovative optimized design philosophy of the optimal arch axis of steel box-concrete arch bridge. Formulas to calculate the arch axis at the arch crown and the arch springing of this type of arch bridge were respectively derived wit     

Effect of Dynamic Viscosity on Marangoni Convection in Liquid Bridge With Liquid Encapsulation

The authors establish the physical and mathomatical model of the Marangoni convection in liquid bridge with liquid encapsulation (or two immiscible coaxial liquid columns). A Numerical simulation of the Marangoni convection in liquid bridge with liquid encapsulation is performed by employed vorticity-streamfunction method and the Alternative Direction Implicit scheme in finite difference. The distribution of temperature and flow in two liquid columns is then obtained. The influence law of the dynamic viscosity ratio of the inner liquid to the outer liquid to the Marangoni convection in liquid bridge with liquid encapsulation is obtained.     

Seismic response of long span arch bridge under spatially variable seismic exicitation

Based on a spatial nonstationary model of seismic ground motion, the seismic acceleration time history are simulated by the wave superposition method. And then taking CaiYuanBa arch bridge in Chongqing as original model , this paper utilizes time history analysis method to analyze the seismic response characteristic of this type of long span arch bridge by support consistent or multi support seismic excitation .The numerical results indicate that the spatial variation of seismic ground motion have significant effect on the response of the arch bridge. Thrust of arch rib and vertical displacement, internal force of arch crown are increased greatly, but most internal forces of stiffener support are reduced.     

Nonlinear Analysis Method for Seismic Responses Considering Pounding between Girders of Curved Bridge with LRBs

A nonlinear constraint-surface impact element (CIE) was developed for simulating the pounding in axial direction between 3D shell-element-mesh bridge girders based on the engineering background of ChaoShan airport. Then, a method, different from the previous literatures, for calculating the stiffness of impact element was proposed based on the flexibility method. The methods proposed were adopted and used to analyze the elevated bridge of ChaoShan airport in GuangZhou for the purpose of investigating comprehensively the earthquake-resistance capability. The bridge girders were modeled by shell elements and CIEs were assigned to the positions of the corresponding expansion joints. Isolating elements were used to simulate LRBs, and typical bilinear LRB hysteresis stiffness model obtained from experiment were adopted to describe the dynamic hysteresis behavior. Pounding forces, dissipation capability of LRBs, lateral displacements of LRBs, pier base shear forces and moments as well as the pounding effect on these cases were investigated, respectively. The proposed methods and analysis results aim at improving the earthquake resistance of the elevated bridge, which provides reference for the similar project.     

模式识别的斜拉桥损伤诊断动力指纹与识别算法

为有效并准确诊断出斜拉桥损伤,对基于模式识别的斜拉桥损伤诊断方法进行了研究。选取易于测试出的低阶模态频率和部分关键点竖向振型数据为动力指纹,无需模态扩展或模型缩聚。研究并采用全因子设计进行动力指纹库的创建,可精确评估设定的损伤因子及其交互作用对损伤识别结果的影响。设计并增加了带随机误差的动力指纹库样本集。编制了基于Matlab的模式识别的多种算法,重点研究了精确度高的多层感知器识别算法及其提高该算法预测准确率的装袋集成算法。最后给出一座单塔双跨双索面斜拉桥的多种识别算法的损伤诊断过程和结果,得到一种可包容测试随机误差的高精确度斜拉桥损伤诊断评估模型。     

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.     

Arch Axis Optimization of New Type Arch Bridge with Diagonal Web Cables Based on Geometric Nonlinear Mechanical Analysis

There are obvious geometric nonlinear mechanical characteristics in new type arch bridge with diagonal web cables. Meanwhile, the convergence of the existing arch axis iterative optimization method is not good. In order to solve new type arch bridge axis iteration convergence problem considering geometric nonlinear mechanical analysis, an arch axis iteration optimization method was proposed based on the iteration basis finite element model with two hinge arch model in main arch ring. A 600m span arch bridge with diagonal web cables was selected as an example to test the convergence performance and applicability of proposed method. The results showed that the bending moment of proposed method had better distribution along arch span, and it is about 35% smaller in maximum bending moment, 17% smaller in minimum bending moment and 23% smaller in bending strain energy compared to the results of linear iteration optimization method. Convergence analysis results demonstrated that proposed method had better iteration performance than the existing method. Meanwhile, different initial arch axis can converge to stable results.     

地震下高墩刚构桥桥台背土相互作用分析方法对比

针对重力式U型桥台背土相互作用,结合现行抗震规范,提出了4种分析模型及其力学本构关系和计算式。采用非线性时程法对比研究了某在建高墩双薄壁连续刚构桥的桥台背土相互作用效应。结果表明：只有弹簧模型可以求得与精细模型基本一致的高阶弹性模态;在纵桥向,滚轴模型和支座模型的结果都比精细模型小,弹簧模型相对精细模型的计算误差最小,关键内力误差不超过20%;在横桥向,支座模型的内力最接近精细模型,而弹簧模型和滚轴模型的结果都偏保守;桥台刚度对关键地震内力的影响幅度低于10%,而桥台有效参与质量的影响幅度也低于15%。综合考虑分析精度和计算成本,弹簧模型在抗震设计中更值得推荐。