Ultra-high performance concrete (UHPC) is featured by a compressive strength 5 times higher than that of ordinary concrete and by a high durability owing to the control of the chloride penetration speed by its dense s...Ultra-high performance concrete (UHPC) is featured by a compressive strength 5 times higher than that of ordinary concrete and by a high durability owing to the control of the chloride penetration speed by its dense structure. The high strength characteristics of UHPC offer numerous advantages like the reduction of the quantities of cables and foundations by the design of a lightweight superstructure in the case of the long-span bridge preserving its structural performance through axial forces and structures governed by compression. This study conducted the conceptual design of a hybrid cable-stayed bridge with central span of 1000 m and exploiting 200 MPa-class UHPC. The economic efficiency of the conceptual design results of the hybrid cable-stayed bridge with central span of 1000 m and of Sutong Bridge, the longest cable-stayed bridge in the world, was analyzed.展开更多
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 (...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.展开更多
A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests...A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.展开更多
Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study t...Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study the effects of connection configurations on seismic responses and fragilities.Finite element models of bridges are established using OpenSees.A new ground motion screening method based on the statistical characteristic of the predominant period is proposed to avoid irregular behavior in the selection process of ground motions,and incremental dynamic analysis(IDA)is performed to develop components and systems fragility curves.The effects of damper failure on calculated results for PEDS are examined in terms of seismic response and fragility analysis.The results show that the bridge tower is the most affected component by different structural systems.For RS,the fragility of the middle tower is significantly higher than other components,and the bridge failure starts from the middle tower,exhibiting a characteristic of local failure.For FS and PEDS,the fragility of the edge tower is higher than the middle tower.The system fragility of RS is higher than FS and PEDS.Taking the failure of dampers into account is necessary to obtain reliable seismic capacity of cable-stayed bridges.展开更多
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/me...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.展开更多
Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design ...Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.展开更多
A method of cable safety analysis is proposed for safety evaluation of long-span cable-stayed bridges. The Daniels＇ effect and the probability of broken wires in the cable are introduced to develop the cable strength...A method of cable safety analysis is proposed for safety evaluation of long-span cable-stayed bridges. The Daniels＇ effect and the probability of broken wires in the cable are introduced to develop the cable strength model and the reliability assessment technique for long-span cable-stayed bridges based on the safety factors analysis of stay cables in service. As an application of the proposed model, the cable safety reliability of the cable No. 25 of Zhaobaoshan cable-stayed bridge in China is calculated. The effects of various parameters on the estimated cable safety reliability are investigated. The results indicate that the proposed method can be used to assess the safety level of stay cables in cable-stayed bridges effectively. The Daniels＇ effect should be taken into account for assessment, and the probability of broken wires can be used to simulate the deterioration of stay cables in service.展开更多
In order to study the mechanical performance of a new type of cable-stayed beam-arch combination bridge, the results of field static and dynamic load tests are comparatively analyzed with numerical results based on th...In order to study the mechanical performance of a new type of cable-stayed beam-arch combination bridge, the results of field static and dynamic load tests are comparatively analyzed with numerical results based on the Jingyi bridge straddling the Daxi River in Yixing. First, the test scheme, tasks, the corresponding measure method, as well as the relevant codes are described. Secondly, two sets of three- dimensional finite element models are established. One is Ansys which uses the solid element and the other is Midas which adopts the beam element. Finally, the experimental and analytical results are comparatively analyzed, and they show an agreement with each other. The results show that the bridge possesses adequate load-carrying capacity under all static load cases, but the capacity of dissipating external input energy is insufficient due to the relatively smaller damping ratio. The study results can provide a reference for further study and optimization of this type of bridge. Calibrated finite-element models that reflect the real conditions can be used as a baseline for future maintenance of the bridge.展开更多
In order to guarantee the safety service and life-span of long-span cable-stayed bridges, the uncertain type of analytic hierarchy process （AHP） method is adopted to access the bridge condition. The correlative theo...In order to guarantee the safety service and life-span of long-span cable-stayed bridges, the uncertain type of analytic hierarchy process （AHP） method is adopted to access the bridge condition. The correlative theory and applied objects of uncertain type of AHP are introduced, and then the optimal transitive matrix method is chosen to calculate the interval number judgment matrix, which makes the weights of indices more reliable and accurate. Finally, with Harbin Songhua River Cable-Stayed Bridge as an example, an index system and an assessment model are proposed for the condition assessment of this bridge, and by using uncertain type of AHP, the weights of assessment indices are fixed and the final assessment results of the bridge are calculated, which proves the feasibility and practicability of this method. The application of this assessment method can provide the scientific basis for maintenance and management of long-span cable-stayed bridges.展开更多
Arch bridges provide significant technical and economic benefits under suitable conditions.In particular,concrete-filled steel tubular(CFST)arch bridges and steel-reinforced concrete(SRC)arch bridges are two types of ...Arch bridges provide significant technical and economic benefits under suitable conditions.In particular,concrete-filled steel tubular(CFST)arch bridges and steel-reinforced concrete(SRC)arch bridges are two types of arch bridges that have gained great economic competitiveness and span growth potential due to advancements in construction technology,engineering materials,and construction equipment over the past 30 years.Under the leadership of the author,two record-breaking arch bridges—that is,the Pingnan Third Bridge(a CFST arch bridge),with a span of 560 m,and the Tian’e Longtan Bridge(an SRC arch bridge),with a span of 600 m—have been built in the past five years,embodying great technological breakthroughs in the construction of these two types of arch bridges.This paper takes these two arch bridges as examples to systematically summarize the latest technological innovations and practices in the construction of CFST arch bridges and SRC arch bridges in China.The technological innovations of CFST arch bridges include cable-stayed fastening-hanging cantilevered assembly methods,new in-tube concrete materials,in-tube concrete pouring techniques,a novel thrust abutment foundation for nonrocky terrain,and measures to reduce the quantity of temporary facilities.The technological innovations of SRC arch bridges involve arch skeleton stiffness selection,the development of encasing concrete materials,encasing concrete pouring,arch rib stress mitigation,and longitudinal reinforcement optimization.To conclude,future research focuses and development directions for these two types of arch bridges are proposed.展开更多
A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile fini...A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.展开更多
Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,esp...Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.展开更多
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...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.展开更多
In a wind-vehicle-bridge(WVB) system,there are various interactions among wind,vehicle and bridge.The mechanism for coupling vibration of wind-vehicle-bridge systems is explored to demonstrate the effects of fundament...In a wind-vehicle-bridge(WVB) system,there are various interactions among wind,vehicle and bridge.The mechanism for coupling vibration of wind-vehicle-bridge systems is explored to demonstrate the effects of fundamental factors,such as mean wind,fluctuating wind,buffeting,rail irregularities,light rail vehicle vibration and bridge stiffness.A long cable-stayed bridge which carries light rail traffic is regarded as a numerical example.Firstly,a finite element model is built for the long cable-stayed bridge.The deck can generally be idealized as three-dimensional spine beam while cables are modeled as truss elements.Vehicles are modeled as mass-spring-damper systems.Rail irregularities and wind fluctuation are simulated in time domain by spectrum representation method.Then,aerodynamic loads on vehicle and bridge deck are measured by section model wind tunnel tests.Eight vertical and torsional flutter derivatives of bridge deck are identified by weighting ensemble least-square method.Finally,dynamic responses of the WVB system are analyzed in a series of cases.The results show that the accelerations of the vehicle are excited by the fluctuating wind and the track irregularity to a great extent.The transverse forces of wheel axles mainly depend on the track irregularity.The displacements of the bridge are predominantly determined by the mean wind and restricted by its stiffness.And the accelerations of the bridge are enlarged after adding the fluctuating wind.展开更多
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 ana...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.展开更多
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 pr...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.展开更多
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 feasibl...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.展开更多
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 aquedu...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.展开更多
This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on b...This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.展开更多
Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibratio...Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.展开更多
文摘Ultra-high performance concrete (UHPC) is featured by a compressive strength 5 times higher than that of ordinary concrete and by a high durability owing to the control of the chloride penetration speed by its dense structure. The high strength characteristics of UHPC offer numerous advantages like the reduction of the quantities of cables and foundations by the design of a lightweight superstructure in the case of the long-span bridge preserving its structural performance through axial forces and structures governed by compression. This study conducted the conceptual design of a hybrid cable-stayed bridge with central span of 1000 m and exploiting 200 MPa-class UHPC. The economic efficiency of the conceptual design results of the hybrid cable-stayed bridge with central span of 1000 m and of Sutong Bridge, the longest cable-stayed bridge in the world, was analyzed.
文摘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.
文摘A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.
基金National Key R&D Program of China under Grant No.2022YFC3003603。
文摘Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study the effects of connection configurations on seismic responses and fragilities.Finite element models of bridges are established using OpenSees.A new ground motion screening method based on the statistical characteristic of the predominant period is proposed to avoid irregular behavior in the selection process of ground motions,and incremental dynamic analysis(IDA)is performed to develop components and systems fragility curves.The effects of damper failure on calculated results for PEDS are examined in terms of seismic response and fragility analysis.The results show that the bridge tower is the most affected component by different structural systems.For RS,the fragility of the middle tower is significantly higher than other components,and the bridge failure starts from the middle tower,exhibiting a characteristic of local failure.For FS and PEDS,the fragility of the edge tower is higher than the middle tower.The system fragility of RS is higher than FS and PEDS.Taking the failure of dampers into account is necessary to obtain reliable seismic capacity of cable-stayed bridges.
基金supported by the Key Project of Science and Technology R&DProgram of CHINA RAILWAY(AJZH2020-001)and Science and Technology Program Project of Shudao Investment Group(SRIG2020GG0001).On behalf of all authors,the corresponding author states that there is no conflict of interest.
文摘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.
基金Project (No.502118) supported by Zhejiang Provincial ScienceFoundation of China
文摘Three-dimensional nonlinear aerodynamic stability analysis was applied to study the aerodynamic stability of a cable-stayed-suspension (CSS) hybrid bridge with main span of 1400 meters, and the effects of some design parameters (such as the cable sag, length of suspension portion, cable plane arrangement, subsidiary piers in side spans, the deck form, etc.) on the aerodynamic stability of the bridge are analytically investigated. The key design parameters, which significantly influence the aerodynamic stability of CSS hybrid bridges, are pointed out, and based on the wind stability the favorable structural system of CSS hybrid bridges is discussed.
基金The Opening Fund of the Key Laboratory of UrbanSecurity and Disaster Engineering of Ministry of Education (NoEESR200701)the Opening Fund of Beijing Laboratory of EarthquakeEngineering and Structural Retrofit
文摘A method of cable safety analysis is proposed for safety evaluation of long-span cable-stayed bridges. The Daniels＇ effect and the probability of broken wires in the cable are introduced to develop the cable strength model and the reliability assessment technique for long-span cable-stayed bridges based on the safety factors analysis of stay cables in service. As an application of the proposed model, the cable safety reliability of the cable No. 25 of Zhaobaoshan cable-stayed bridge in China is calculated. The effects of various parameters on the estimated cable safety reliability are investigated. The results indicate that the proposed method can be used to assess the safety level of stay cables in cable-stayed bridges effectively. The Daniels＇ effect should be taken into account for assessment, and the probability of broken wires can be used to simulate the deterioration of stay cables in service.
文摘In order to study the mechanical performance of a new type of cable-stayed beam-arch combination bridge, the results of field static and dynamic load tests are comparatively analyzed with numerical results based on the Jingyi bridge straddling the Daxi River in Yixing. First, the test scheme, tasks, the corresponding measure method, as well as the relevant codes are described. Secondly, two sets of three- dimensional finite element models are established. One is Ansys which uses the solid element and the other is Midas which adopts the beam element. Finally, the experimental and analytical results are comparatively analyzed, and they show an agreement with each other. The results show that the bridge possesses adequate load-carrying capacity under all static load cases, but the capacity of dissipating external input energy is insufficient due to the relatively smaller damping ratio. The study results can provide a reference for further study and optimization of this type of bridge. Calibrated finite-element models that reflect the real conditions can be used as a baseline for future maintenance of the bridge.
基金Specialized Research Fund for the Doctoral Programof Higher Education (No20050213008)the Scientific and TechnicalPlan Item of Communications Department of Heilongjiang Province ofChina (2004)
文摘In order to guarantee the safety service and life-span of long-span cable-stayed bridges, the uncertain type of analytic hierarchy process （AHP） method is adopted to access the bridge condition. The correlative theory and applied objects of uncertain type of AHP are introduced, and then the optimal transitive matrix method is chosen to calculate the interval number judgment matrix, which makes the weights of indices more reliable and accurate. Finally, with Harbin Songhua River Cable-Stayed Bridge as an example, an index system and an assessment model are proposed for the condition assessment of this bridge, and by using uncertain type of AHP, the weights of assessment indices are fixed and the final assessment results of the bridge are calculated, which proves the feasibility and practicability of this method. The application of this assessment method can provide the scientific basis for maintenance and management of long-span cable-stayed bridges.
基金financially supported by the Guangxi Key Research and Development Plan Program(AB22036007).
文摘Arch bridges provide significant technical and economic benefits under suitable conditions.In particular,concrete-filled steel tubular(CFST)arch bridges and steel-reinforced concrete(SRC)arch bridges are two types of arch bridges that have gained great economic competitiveness and span growth potential due to advancements in construction technology,engineering materials,and construction equipment over the past 30 years.Under the leadership of the author,two record-breaking arch bridges—that is,the Pingnan Third Bridge(a CFST arch bridge),with a span of 560 m,and the Tian’e Longtan Bridge(an SRC arch bridge),with a span of 600 m—have been built in the past five years,embodying great technological breakthroughs in the construction of these two types of arch bridges.This paper takes these two arch bridges as examples to systematically summarize the latest technological innovations and practices in the construction of CFST arch bridges and SRC arch bridges in China.The technological innovations of CFST arch bridges include cable-stayed fastening-hanging cantilevered assembly methods,new in-tube concrete materials,in-tube concrete pouring techniques,a novel thrust abutment foundation for nonrocky terrain,and measures to reduce the quantity of temporary facilities.The technological innovations of SRC arch bridges involve arch skeleton stiffness selection,the development of encasing concrete materials,encasing concrete pouring,arch rib stress mitigation,and longitudinal reinforcement optimization.To conclude,future research focuses and development directions for these two types of arch bridges are proposed.
基金Project(51178469) supported by the National Natural Science Foundation of China
文摘A proven beam-track contact model was used to analyze the track-structure interaction of CWR (continuously welded track) on bridge. Considering the impact of adjacent bridges, the tower-cable-track-beam-pier-pile finite element model of the cable-stayed bridge was established. Taking a bridge group including 40-32m simply-supported beam and (32+80+112)m single-tower cable-stayed bridge and 17-32m simply-supported beam on the Kunming-Shanghai high-speed railway as an example, the characteristics of CWR longitudinal force on the cable-stayed bridge were studied. It is shown that adjacent bridges must be considered in the calculation of the track expansion force and bending force on cable-stayed bridge. When the span amount of adjacent bridges is too numerous, it can be simplified as six spans; the fixed bearing of adjacent simply-supported beams should be placed on the side near the cable-stayed bridge; the track expansion device should be set at the bridge tower to reduce the track force near the bridge abutment.
基金supported by the National Natural Science Foundation of China(No. 50478075)the Jiangsu "Six Top Talent" Program of China(No. 07-F-008)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Scientific Research Foundation of Graduate School of Southeast University (No. YBJJ0817),China
文摘Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon.
文摘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.
基金Projects (U1334201,51525804) supported by the National Natural Science Foundation of ChinaProject (15CXTD0005) supported by the Sichuan Province Youth Science and Technology Innovation Team,China
文摘In a wind-vehicle-bridge(WVB) system,there are various interactions among wind,vehicle and bridge.The mechanism for coupling vibration of wind-vehicle-bridge systems is explored to demonstrate the effects of fundamental factors,such as mean wind,fluctuating wind,buffeting,rail irregularities,light rail vehicle vibration and bridge stiffness.A long cable-stayed bridge which carries light rail traffic is regarded as a numerical example.Firstly,a finite element model is built for the long cable-stayed bridge.The deck can generally be idealized as three-dimensional spine beam while cables are modeled as truss elements.Vehicles are modeled as mass-spring-damper systems.Rail irregularities and wind fluctuation are simulated in time domain by spectrum representation method.Then,aerodynamic loads on vehicle and bridge deck are measured by section model wind tunnel tests.Eight vertical and torsional flutter derivatives of bridge deck are identified by weighting ensemble least-square method.Finally,dynamic responses of the WVB system are analyzed in a series of cases.The results show that the accelerations of the vehicle are excited by the fluctuating wind and the track irregularity to a great extent.The transverse forces of wheel axles mainly depend on the track irregularity.The displacements of the bridge are predominantly determined by the mean wind and restricted by its stiffness.And the accelerations of the bridge are enlarged after adding the fluctuating wind.
基金Alexander von Humboldt Fellowship-AvH (IV–AGY/1117497 STP)Japan Society for the Promotion of Science-JSPS Fellowship (P06138)
文摘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.
文摘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.
基金Sponsored by the National Basic Research Program of China(Grant No.2013CB036303)the National Natural Science Foundation of China(Grant No.51008223)
文摘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.
基金National Natural Science Foundation of China Under Grant No.50678121Open Research Fund Program of State key Laboratory of Hydro-science and Engineering
文摘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.
基金Project(51678576) supported by the National Natural Science Foundation of ChinaProject(2017YFB1201204) supported by the National Key R&D Program of China。
文摘This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.
基金Project(No.20100481432)supported by the China Postdoctoral Science Foundation
文摘Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexi-bility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.
