Process Monitoring and Terminal Verification of Cable-Stayed Bridges with Corrugated Steel Webs under Contruction

In this paper,the construction process of a cable-stayed bridge with corrugated steel webs was monitored.Moreover,the end performance of the bridge was verified by load test.Owing to the consideration of the bridge structure safety,it is necessary to monitor the main girder deflection,stress,construction error and safety state during construction.Furthermore,to verify whether the bridge can meet the design requirements,the static and dynamic load tests are carried out after the completion of the bridge.The results of construction monitoring show that the stress state of the structure during construction is basically consistent with the theoretical calculation and design requirements,and both meet the design and specification requirements.The final measured stress state of the structure is within the allowable range of the cable-stayed bridge,and the stress state of the structure is normal and meets the specification requirements.The results of load tests show that the measured deflection values of the mid-span section of the main girder are less than the theoretical calculation values.The maximum deflection of the girder is−20.90 mm,which is less than−22.00 mm of the theoretical value,indicating that the girder has sufficient structural stiffness.The maximum impact coefficient under dynamic load test is 1.08,which is greater than 1.05 of theoretical value,indicating that the impact effect of heavy-duty truck on this type of bridge is larger.This study can provide important reference value for construction and maintenance of similar corrugated steel web cable-stayed bridges.

Optimization of Dead Load State in Earth-Anchored Cable-Stayed Bridges

In order to determine the reasonable completed dead load state in earth-anchored cable-stayed bridges,a practical method is proposed. The method is based on the rigidly supported continuous beam method and the feasible zone method,emphasizing on the mutual effect between the self-anchored structural parts and the earth-anchored ones. Three cable-stayed bridge models are designed with the main spans of 1 400 m,including a partially earth-anchored cable-stayed bridge,a cable-stayed-suspension bridge and a fully selfanchored cable-stayed bridge,in which the C50 concrete and Q345 steel are adopted. The partially earthanchored cable-stayed bridge and the cable-stayed-suspension bridge secure lower compressive force in the girder than the fully self-anchored cable-stayed bridge by 25 percent at least. The same is for the material consumption of the whole bridge. Furthermore,the anchor volume is more than 20% lower in the partially earthanchored cable-stayed bridge than that in the cable-stayed-suspension bridge. Consequently,the practical span of cable-stayed bridges can be accordingly extended.

Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part I,Comprehensive reliability and partial failure probabilities

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions： （1） formulate the failure probabilities; （2） normalize various load distributions; and （3） establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.

Ground motion spatial variability effects on seismic response control of cable-stayed bridges

The spatial variability of input ground motion at supporting foundations plays a key role in the structural response of cable-stayed bridges （CSBs）; therefore, spatial variation effects should be included in the analysis and design of effective vibration control systems. The control of CSBs represents a challenging and unique problem, with many complexities in modeling, control design and implementation, since the control system should be designed not only to mitigate the dynamic component of the structural response but also to counteract the effects of the pseudo-static component of the response. The spatial variability effects on the feasibility and efficiency of seismic control systems for the vibration control of CSBs are investigated in this paper. The assumption of uniform earthquake motion along the entire bridge may result in quantitative and qualitative differences in seismic response as compared with those produced by uniform motion at all supports. A systematic comparison of passive and active system performance in reducing the structural responses is performed, focusing on the effect of the spatially varying earthquake ground motion on the seismic response of a benchmark CSB model with different control strategies, and demonstrates the importance of accounting for the spatial variability of excitations.

Comparative Study on Structural Redundancy of Cable-Stayed and Extradosed Bridges Through Safety Assessment of Their Stay Cables

This study provides new insights into the comparison of cable-stayed and extradosed bridges based on the safety assessment of their stay cables.These bridges are often regarded as identical structures owing to the use of inclined cables;however,the international standards for bridge design stipulate different safety factors for stay cables of both types of bridges.To address this misconception,a comparative study was carried out on the safety factors of stay cables under fatigue and ultimate limit states by considering the effects of various untoward and damaging factors,such as overloading,cable loss,and corrosion.The primary goal of this study is to describe the structural disparities between both types of bridges and evaluate their structural redundancies by employing deterministic and nondeterministic methods.To achieve this goal,three-dimensional finite-element models of both bridges were developed based on the current design guidelines for stay cables in Japan.After the balanced states of the bridge models were achieved,static analyses were performed for different safety factors of stay cables in a parametric manner.Finally,the first-order reliability method and Monte Carlo method were applied to determine the reliability index of stay cables.The analysis results show that cable-stayed and extradosed bridges exhibit different structural redundancies for different safety factors under the same loading conditions.Moreover,a significant increase in structural redundancy occurs with an incremental increase in the safety factors of stay cables.

Dynamic Response of Sea-Crossing Rail-cum-Road Cable-Stayed Bridge Influenced by Random Wind–Wave–Undercurrent Coupling

Sea-crossing bridges are affected by random wind–wave–undercurrent coupling loads, due to the complex marine environment. The dynamic response of long-span Rail-cum-Road cable-stayed bridges is particularly severe under their influence, potentially leading to safety problems. In this paper, a fluid–structure separation solution method is implemented using Ansys–Midas co-simulation, in order to solve the above issues effectively while using less computational resources. The feasibility of the method is verified by comparing the tower top displacement response with relevant experimental data. From time and frequency domain perspectives, the displacement and acceleration responses of the sea-crossing Rail-cum-Road cable-stayed bridge influenced by wave-only, wind–wave, and wind–wave–undercurrent coupling are comparatively studied. The results indicate that the displacement and acceleration of the front bearing platform top are more significant than those of the rear bearing platform. The dominant frequency under wind–wave–undercurrent coupling is close to the natural vibration frequencies of several bridge modes,such that wind–wave–undercurrent coupling is more likely to cause a resonance effect in the bridge. Compared with the wave-only and wind–wave coupling, wind–wave–undercurrent coupling can excite bridges to produce larger displacement and acceleration responses: at the middle of the main girder span, compared with the wave-only case, the maximum displacement in the transverse bridge direction increases by 23.58% and 46.95% in the wind–wave and wind–wave–undercurrent coupling cases, respectively;at the tower top, the variation in the amplitude of the displacement and acceleration responses of wind–wave and wind–wave–undercurrent coupling are larger than those in the wave-only case, where the acceleration change amplitude of the tower top is from-0.93 to 0.86 m/s^(2) in the waveonly case, from-2.2 to 2.1 m/s^(2) under wind–wave coupling effect, and from-2.6 to 2.65 m/s^(2) under wind–wave–undercurrent coupling effect, indicating that the tower top is mainly affected by wind loads, but wave and undercurrent loads cannot be neglected.

A simplified design method for metallic dampers used in the transverse direction of cable-stayed bridges

The aseismic design of cable-stayed bridges in the transverse direction with newly proposed metallic dampers that can accommodate both longitudinal and transverse movement of the deck has recently been considered.This work focuses on developing a simplified method to design an appropriate metallic damper.The seismic performance of cablestayed bridges with different damper stiffness,main span lengths,tower shapes and types of deck in the transverse direction are investigated.The transverse displacement of the deck of a cable-stayed bridge increases significantly with the increment of the damper stiffness,which proves that the design of the damper stiffness is crucial.A simplified model considering the damper stiffness,cable system and tower in the transverse direction is developed to evaluate the period and lateral displacement of a complicated cable-stayed bridge.Based on the simplified model,a design method is proposed and assessed using two cable-stayed bridges as examples.The results show that metallic dampers can be designed with high efficiency,and the optimal ductility of the damper can be selected.

Development of Optimal Structural System for Hybrid Cable-Stayed Bridges Using Ultra High Performance Concrete

This study developed an optimal structural system for the hybrid cable-stayed bridge expected to have a durable lifetime of 200 years and of which major structural members are made of ultra high performance concrete (UHPC) with 200 MPa-class compressive strength. This innovative cable-stayed bridge system makes it possible to reduce each of the construction and maintenance costs by 20% compared to the conventional concrete cable-stayed bridge by improving significantly the weight and durability of the bridge. Therefore, detail design is carried out considering a real 800 m cable-stayed bridge and the optimal structure of the hybrid cable-stayed bridge is proposed and verified.

Modeling of cable vibration effects of cable-stayed bridges

The analysis of dynamic responses of cable-stayed bridges subjected to wind and earthquake loads generally considers only the motions of the bridge deck and pylons.The influence of the stay cable vibration on the responses of the bridge is either ignored or considered by approximate procedures.The transverse vibration of the stay cables,which can be significant in some cases,are usually neglected in previous research.In the present study,a new three-node cable element has been developed to model the transverse motions of the cables.The interactions between the cable behavior and the other parts of the bridge superstructure are considered by the concept of dynamic stiffness.The nonlinear effect of the cable caused by its self-weight is included in the formulation.Numerical examples are presented to demonstrate the accuracy and efficiency of the proposed model. The impact of cable vibration behavior on the dynamic characteristics of cable-stayed bridges is discussed.

Shake table experimental study of cable-stayed bridges with two different design strategies of H-shaped towers

As one of the main load-carrying components of cable-stayed bridges,bridge towers are typically required to remain elastic even when subjected to severe ground motions with a 2%-3%probability of exceedance in 50 years.To fulfill this special requirement imposed by current seismic design codes,reinforcement ratios in the bridge towers have to be kept significantly higher than if limited ductility behavior of the tower is allowed.In addition,since the foundation capacity is closely related to the moment and shear capacities of the bridge tower,a large increase in bridge construction cost for elastically designed cable-stayed bridge is inevitable.To further investigate the possibility of limited ductility bridge tower design strategies,a new 1/20-scale cable-stayed bridge model with H-shaped bridge towers designed according to strong strut-weak tower column design was tested.The shake table experimental results are compared with a previous strong tower column-weak strut designed full bridge model.A comparison of the results show that ductility design with plastic hinges located on tower columns,i.e.,strong strut-weak tower column design,is another effective seismic design strategy that results in only small residual displacement at the top of the tower column,even under very severe earthquake excitations.

Analysis of Key Factors in Cable Force Calculation for Cable-Stayed Bridges

Three methods for calculating cable force （analytic method, fitting method and finite element method） are analyzed and compared. The effects of boundary condition, spectrum resolution, sampling time, and number of sampling points on the precision of cable force identification are discussed, and error analysis is conducted. The results of three methods applied to a practical project are significantly less than the design value. Comparatively, the result of finite element method is the closest to the design value. Moreover, their computational precision and error are compared and analyzed. The precision of frequency identification of cables, long cables in particular, is strongly affected by frequency resolution. If the frequency resolution is included in calculating the cable force, the identification error can be reduced greatly.

Research review on steel–concrete composite joint of railway hybrid girder cable-stayed bridges

Purpose–This study aims to research the development trend,research status,research results and existing problems of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.Design/methodology/approach–Based on the investigation and analysis of the development history,structure form,structural parameters,stress characteristics,shear connector stress state,force transmission mechanism,and fatigue performance,aiming at the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge,the development trend,research status,research results and existing problems are expounded.Findings–The shear-compression composite joint has become the main form in practice,featuring shortened length and simplified structure.The length of composite joints between 1.5 and 3.0 m has no significant effect on the stress and force transmission laws of the main girder.The reasonable thickness of the bearing plate is 40–70 mm.The calculation theory and simplified calculation formula of the overall bearing capacity,the nonuniformity and distribution laws of the shear connector,the force transferring ratio of steel and concrete components,the fatigue failure mechanism and structural parameters effects are the focus of the research study.Originality/value–This study puts forward some suggestions and prospects for the structural design and theoretical research of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.

Experimental Study on Shear Lag Effect of Partial Cable-Stayed Bridge and Elasto-Plastic Seismic Analysis

The project of Xiaoxihu Yellow River Bridge in Lanzhou is chosen as partial cable-stayed bridge. To get the shear lag effect and anti-earthquake performance of the actual bridge under various loading conditions, organic glass scaled model was adopted to have an experiment and a theory research at one time. The experiment result is the basically same as the theory calculation which proves the FEA method can well calculate shear lag effect and dynamical performance. As a result, because the bridge is located in a seismic area of 8 degree, an elasto-plastic seismic checking is performed by customized FEA program in this paper.

Semi-active control of a cable-stayed bridge under multiple-support excitations

This paper presents a semi-active strategy for seismic protection of a benchmark cable-stayed bridge with consideration of multiple-support excitations. In this control strategy, Magnetorheological (MR) dampers are proposed as control devices, a LQG-clipped-optimal control algorithm is employed. An active control strategy, shown in previous researches to perform well at controlling the benchmark bridge when uniform earthquake motion was assumed, is also used in this study to control this benchmark bridge with consideration of multiple-support excitations. The performance of active control system is compared to that of the presented semi-active control strategy. Because the MR fluid damper is a con-trollable energy- dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. The numerical results demonstrated that the performance of the presented control design is nearly the same as that of the active control system; and that the MR dampers can effectively be used to control seismically excited cable-stayed bridges with multiple-support excitations.

Numerical simulation of dynamic characteristics of a cable-stayed aqueduct bridge

In this paper, a full-scale 3-D finite element model of the Jundushan cable-stayed aqueduct bridge is established with ANSYS Code. The shell, fluid, tension-only spar and beam elements are used for modeling the aqueduct deck, filled water, cables and support towers, respectively. A multi-element cable formulation is introduced to simulate the cable vibration. The dry （without water） and wet （with water） modes of the aqueduct bridge are both extracted and investigated in detail. The dry modes of the aqueduct bridge are basically similar to those of highway cable-stayed bridges. A dry mode may correspond to two types of wet modes, which are called the in-phase （with lower frequency） and out-of-phase （with higher frequency） modes. When the water-structure system vibrates in the in-phase/out-of-phase modes, the aqueduct deck moves and water sloshes in the same/opposite phase-angle, and the sloshing water may take different surface-wave modes. The wet modes of the system reflect the properties of interaction among the deck, towers, cables and water. The in-phase wet frequency generally decreases as the water depth increases, and the out-of-phase wet frequency may increase or decrease as the water depth increases.

Infl uence of structural parameters on dynamic characteristics and wind-induced buffeting responses of a super-long-span cable-stayed bridge

A 3D finite element （FE） model for the Sutong cable-stayed bridge （SCB） is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wind data, the measured spectra expression is presented using the nonlinear least-squares regression method. Turbulent winds at the bridge site are simulated based on the spectral representation method and the FFT technique. The influence of some key structural parameters and measures on the dynamic characteristics of the bridge are investigated. These parameters include dead load intensity, as well as vertical, lateral and torsional stiffness of the steel box girder. In addition, the influence of elastic stiffness of the connection device employed between the towers and the girder on the vibration mode of the steel box girder is investigated. The analysis shows that all of the vertical, lateral and torsional buffeting displacement responses reduce gradually as the dead load intensity increases. The dynamic characteristics and the structural buffeting displacement response of the SCB are only slightly affected by the vertical and torsional stiffness of the steel box girder, and the lateral and torsional buffeting displacement responses reduce gradually as the lateral stiffness increases. These results provide a reference for dynamic analysis and design of super-long-span cable-stayed bridges.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations——I:Theory

In this paper, wind-induced vibration control of a single column tower of a cable-stayed bridge with a multi- stage pendulum mass damper （MSPMD） is investigated. Special attention is given to overcoming space limitations for installing the control device in the tower and the effect of varying natural frequency of the towers during construction. First, the finite element model of the bridge during its construction and the basic equation of motion of the MSPMD are introduced. The equation of motion of the bridge with the MSPMD under along-wind excitation is then established. Finally, a numerical simulation and parametric study are conducted to assess the effectiveness of the control system for reducing the wind-induced vibration of the bridge towers during construction. The numerical simulation results show that the MSPMD is practical and effective for reducing the along-wind response of the single column tower, can be installed in a small area of the tower, and complies with the time-variant characteristics of the bridge during its entire construction stage.

Analysis on Deflection Characteristics of Steel Cable-Stayed Bridge

Various kinds of deflection characteristics on the steel cable-stayed bridge(Nanjing No.3 Yangtze River Bridge)are investigated by different mathematical statistical methods.Firstly,via Pearson correlation coefficient calculation,it shows good consistency between the adjacent measuring point of side span or middle span.Secondly,taking mid-span deflection as an example,the correlation analysis of deflection and temperature is conducted.They are synchronous via cross correlation coefficient calculation but not completely linear and a"hysteresis loop"phenomenon of three stages is formed.The fitting result on the monitoring data at day time is consistent with the numerical value through the application of unit temperature difference between the cable and girder and the positive temperature gradient of girder in the finite element model.And the temperature effect is considerable.Vehicle loads effect is obtained from wavelet analysis.The extracted curve can indirectly reflect the change of traffic loads.Finally,the structural damage is analyzed through the trend fusion on the deflection,cable force and visual inspection from 2006 to 2015.Relevant conclusions can provide a basis for management departments to carry out special detection.

Internal Force Distribution in Steel-Concrete Composite Structure for Pylon of Cable-Stayed Bridge

Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.

Dynamic performance of cable-stayed bridge tower with multi-stage pendulum mass damper under wind excitations—Ⅱ: Experiment

The possibility of using a multi-stage pendulum mass damper （MSPMD） to control wind-induced vibration of a single column tower of a cable-stayed bridge during construction was studied theoretically in part I of this work. In this paper, the performance of the MSPMD for reducing bridge tower vibration is studied experimentally. A MSPMD model and a tower model of the bridge with geometry scaling of 1：100 were designed and manufactured. Calibration of the MSPMD model with different wire lengths is conducted to verify the analytical model of the damper. A series of tests for the uncontrolled freestanding tower, tower with cables, and tower with MSPMD model are then performed under harmonic and white noise excitations. The experimental results show that the responses of the tower model significantly decrease with the installation of the MSPMD model, which demonstrates the effectiveness of the M SPMD to mitigate the vibration of the bridge tower.