Analysis Of Long-span Cable-stayed Bridges Research Articles

Unified framework for stochastic dynamic responses and system reliability analysis of long-span cable-stayed bridges under near-fault ground motions

Long-span cable-stayed bridges are complex systems with numerous components, and prone to failures of multiple components under near-fault ground motions with long-period velocity pulses. The evaluation of dynamic system reliability of cable-stayed bridges is an important challenging issue. In this work, a unified framework for simultaneously determining both the stochastic dynamic responses and system reliabilities of long-span cable-stayed bridges under near-fault stochastic ground motions is proposed based on direct probability integral method (DPIM) with adaptive strategy. Firstly, the 3-dimensional finite element model of typical cable-stayed bridge and the stochastic synthesis model of near-fault ground motions are established. Based on probability density integral equation, new formulas in input probability space of time-variant moments of response are derived. Then, DPIM with adaptive strategy is suggested to calculate the mean value and standard deviation of response via new formulas. Dynamic system reliability of cable-stayed bridge under near-fault stochastic ground motions is evaluated by establishing failure criteria of extreme value mappings of multiple performance functions. Finally, numerical results indicate that the long-period velocity pulse of near-fault motions imposes an important effect, resulting in large mean responses and failure of cables. Failure probability of cables is significantly increased with the occurrence of velocity pulses, which causes the decrease of system reliability of cable-stayed bridge. Thus, the randomness and velocity pulse effect of near-fault ground motions should be seriously considered for reliability-based design and safety assessment of cable-stayed bridges.

Seismic behavior analysis of long-span cable-stayed bridge under bi-directional near-fault ground motions

In this paper, the seismic behaviors of a long-span cable-stayed bridge subjected to bi-directional near-fault ground motions are analyzed. The cable-stayed bridge with a main span of 432 m is selected as the research object and appropriately modeled using the OpenSees software. Ten sets of historical near-fault and far-field ground motions associated with the same earthquake event and site class are utilized as input excitations. Nonlinear time-history analyses are conducted to explore three key aspects: the influence of ground motion directionality, the effectiveness of the percentage rule and simplified Square-Root-of-Sum-of-Squares (SRSS) rule, and the main influential factors. The findings reveal that near-fault ground motions induce larger seismic responses compared to far-field ground motions. Moreover, the effects of ground motion directionality are more pronounced in near-fault scenarios than in far-field events. The percentage rule and simplified SRSS rule demonstrate minor significance in predicting the critical seismic responses. The bi-directional peak ground velocity (PGV) of seismic motions in the principal directions of the cable-stayed bridge may emerge as the primary factor influencing the seismic responses, making it a suitable intensity measure for bi-directional seismic fragility assessment.

Effect of uncertainties in cable corrosion and material strength on seismic fragility of long-span cable-stayed bridges in marine environments

This paper presents an investigation into the seismic fragility of cable-stayed bridges and considers the complex uncertainties in cable corrosion and material strength. Under certain assumptions and using the limited measured data available for steel corrosion, a cable corrosion model is established. The probability distribution of several parameters, including the corrosion rate, corrosion initiation time, chloride concentration, and cable replacement in the corrosion model, is considered. In addition, the influence of the stress level of cables is also considered in the model by the amplification coefficient of the corrosion rate. To consider the effect of the uncertainties in cable corrosion and material strength on the seismic fragility of this bridge, the uniform design (UD) method is used to generate reasonable bridge samples and to build probabilistic seismic demand models. The results indicate that cable corrosion has a significant impact on the seismic fragility of cable-stayed bridges. The seismic fragility of girders and piers are the smallest and the highest among all bridge components, respectively. The material strength uncertainties have a significant influence on the seismic fragility of bridge components. The coupling between the uncertainties in cable corrosion and material strength does not increase the seismic fragility of the bridge components in most cases because of the cancellation effect of the two uncertainties to some extent. In addition, cable replacement has a significant influence on the seismic fragility of bridge components. In order to correctly evaluate the performance of cable-stayed bridges in service, it is necessary to consider the uncertainties in cable corrosion and material strength in a seismic fragility analysis of long-span cable-stayed bridges with different service periods.

Node-based wave analysis method for the dynamic response and stiffness of long-span cable-stayed bridges

For dynamic analysis of long-span cable-stayed bridges (LCB) with high flexibility and long force transmission paths, wave analysis method offers unique advantages over modal analysis. However, conducting wave analysis for the entire LCB poses challenges due to the modeling complexity and the substantial computational cost associated with solving numerous wave equations. Therefore, a simple analytical approach for wave analysis of LCB is proposed, which entails the discretization of the entire bridge into waveguides and the subsequent recombination of the regularized local wave propagation models. The feasibility and strategy of solving the global propagation function using local double coordinate systems and specific node-based local wave propagation models are demonstrated. Additionally, based on the geometric and mechanical configuration of nodes in the LCB, local wave scattering and propagation models corresponding to the four standardized nodes types are proposed. A unified Node-Based Wave Analysis (NWA) method for LCB is developed, considering the viscoelastic behavior of cable-stayed beams according to the Kelvin-Voigt model to enhance structural realism. The reasonable damping coefficient in bridge is determined by means of theory and dynamic in situ test of three bridges. Finally, an extended case study is conducted on a typical two-pylon cable-stayed bridge, focusing on the impact of moving loads and material properties on wave characteristics. The results demonstrate the reliability of the proposed NWA method in predicting wave energy distribution, highlighting the suitability of wave analysis for dynamic analysis of LCB. In comparison to undamped structures, it has been found that the presence of damping results in a pair of additional flexural waves with a new dispersion relation in cable-stayed bridges. Furthermore, the study reveals the stiffness enhancement mechanism associated with wave dispersion characteristics in cable-stayed bridges.

Multi-parameter seismic fragility and sensitivity analysis of long-span cable-stayed bridge based on multi-task lasso regression

The accuracy and efficiency of the seismic fragility assessment of bridges encounter challenges when the span increases and the structure becomes more complex, which is significantly affected by various uncertain parameters and has to be studied. Multi-parameter seismic fragility analysis (MP-SFA) is a powerful tool that explicitly connects fragilities and multiple variables, including structural parameters and seismic intensity measures (IM). This paper presents an efficient generation method for MP-SFA based on multi-task Lasso regression and is verified using an example of a long-span cable-stayed bridge. Based on the framework of MP-SFA, the mean fragility curves of various bridge components are established, which averages the influence of all considered random parameters. A sensitivity analysis method is also established to identify significant variables for fragility function. The analysis and numerical results show the necessity of MP-SFA to overcome the dispersion of bridge fragility due to the incapability of a single parameter. PGV is shown as the most significant parameter for the case. However, the other IMs also have a non-negligible impact on fragility.

Nonlinear dynamic analysis of long-span cable-stayed bridges with train\u2013bridge and cable coupling

Span lengths of newly constructed cable-stayed railway bridges continue to show increases relative to those of older bridges. Accompanying such increases is the importance of ensuring that vibrations of long-span cable-stayed bridges satisfy both safety and serviceability requirements, particularly for bridges that support train passages. In contrast to modern design of bridges that support roadway vehicles, current methods for analyzing cable-stayed railway bridges do not yet typically account for coupling effects that may occur between cables and the surrounding bridge structure during train passages. This paper presents a computational framework for the nonlinear dynamic analysis of railway bridges based on a coupled train–bridge analytical model and investigates the significance of accounting for cable-related coupling effects. A case study is then carried out, where coupled dynamic responses of cables, towers, and girders of an in-service railway bridge are computed and compared to those obtained using an uncoupled approach. These comparisons demonstrate the merits of accounting for coupling phenomena when computing dynamic characteristics of cable-stayed railway bridges and highlight benefits of the coupled analysis approach in bridge design applications.

Construction sequence analysis of long-span cable-stayed bridges

In cantilever construction of long-span cable-stayed bridges the stressing sequence of stays is fundamental for establishing the final configuration of the bridge. The structural behaviour of these bridges is usually evaluated through a forward staged construction analysis, in which the values of the prestressing forces to be applied to stays are the main unknowns. A unified procedure for determining the initial cable forces and for analyzing the entire sequence is presented here, considering the geometric nonlinearity of stays through the Dischinger equivalent elastic modulus. The target is the simultaneous determination of the initial cable forces with the simulation of the construction stages in the forward analysis, taking into account the cable-sag effect, in order to achieve the required geometric configuration at the end of the sequence together with an advantageous state of stress for deck and pylon. Furthermore, a probabilistic approach is proposed for the evaluation of the effects that uncertainties of stay forces, occurring in the actual stressing sequences on site, have on the bridge behaviour. With this purpose probable errors during the real work operations on site are considered here in addition to the theoretical analysis of construction stages. Finally, the evaluation of the reliability of the proposed procedure is tested on a case-study of a long-span cable-stayed bridge, considering the influence of the deck typology on the stressing sequence.

Dynamic Characteristics Analysis of Long-Span Cable-Stayed Bridge with Steel Truss Stiffening Girder

With the development of transportation, more and more long-span floating system steel truss-stiffened cable-stayed bridges have been built. Due to the non-restraint in longitudinal direction, this kind of bridges possess very superior performance in the dissipation of vibration energy. On account of the characteristics above, the paper intends to discuss the dynamic behavior of this type of bridges. Based on a real structure design, the numerical simulation procedure of the vibration has been introduced. According to a series of assumptions, the dynamic 3D FEM model of the bridge is established firstly. Thereafter, the vibration characteristics of the model are evaluated. Results show that the longitudinal stiffness is relatively small in comparison to the torsional stiffness. The 1st order mode is longitudinal floatation of girders and pylons. But overall the bridge is still rather flexible.

Dynamic analysis of long-span cable-stayed bridges under wind and traffic using aerodynamic coefficients considering aerodynamic interference

The aerodynamic characteristics of vehicles are critical to assess vehicle safety and passenger comfort for vehicles running on long span bridges in a windy environment. However, in previous wind–vehicle–bridge (WVB) system analysis, the aerodynamic interference between the vehicle and the bridge was seldom considered, which will result in changing aerodynamic coefficients. In this study, the aerodynamic coefficients of a high-sided truck on the ground (ground case) and a typical bridge deck (bridge deck case) are determined in a wind tunnel. The effects of existent structures including the bridge deck and bridge accessories on the high-sided vehicle\'s aerodynamic characteristics are investigated. A three-dimensional analytical framework of a fully coupled WVB system is then established based on the finite element method. By inputting the aerodynamic coefficients of both cases into the WVB system separately, the vehicle safety and passenger comfort are assessed, and the critical accidental wind speed for the truck on the bridge in a windy environment is derived. The differences in the bridge response between the windward case and the leeward case are also compared. The results show that the bridge deck and the accessories play a positive role in ensuring vehicle safety and improving passenger comfort, and the influence of aerodynamic interference on the response of the bridge is weak.

Seismic fragility assessment of long-span cable-stayed bridges in China

In the existing fragility assessment, most bridges are short-span bridges and a few bridges have long spans such as cable-stayed bridges. In this study, a procedure is proposed to conduct the component and system seismic fragility analysis of long-span cable-stayed bridges. Three critical issues are addressed in the procedure: (1) the optimal intensity measure of cable-stayed bridges, (2) limit state models of various components, and (3) contribution of individual components to the entire system failure of bridges. This study chooses a long-span cable-stayed bridge with the most common configuration in China and builds the numerical model of its multiple components using OpenSEES that can account for their nonlinear response and uncertainties in the ground motion and material properties. Four typical intensity measures are compared with respect to four characteristic properties including efficiency, practicality, sufficiency, and proficiency. Peak ground velocity turns out to be the optimal intensity measure. Limit states of pylon sections are derived by a numerical simulation based on pushover analysis and China’s guidelines. The pushover results indicate that the limit state of their section curvature depends highly on the section type and axial compression coefficient. A joint probabilistic seismic demand model and Monte Carlo simulation are employed to obtain an accurate system fragility estimate of cable-stayed bridges by accounting for the contribution of each component to the overall bridge system. The system fragility curves based on Monte Carlo simulation lie much closer to the upper bound fragilities given small correlation coefficients, implying that seismic demands of various components conditioned on the peak ground velocity are not correlated.

Static Parameter Sensitivity Analysis of Long-Span Cable-Stayed Bridge Based on RSM

AbstractThe response surface method (RSM) was used to construct the explicit response equation between design parameters and structure response. This method was also used to analyze the sensitivity of the parameters. Accordingly, the influence degree of various design parameters on the response of long-span cable-stayed bridge was analyzed. The sensitivity factors of the design parameters solved through the explicit response equation could show the tendency of internal force, deformation, and cable force of a long-span cable-stayed bridge under the condition of changing design parameters. These design parameters were divided into four importance ratings according to the sensitivity percentage value. This task could quantitatively distinguish the influence degree of the design parameters on the structural response. The method could provide the reference for parameter sensitivity analysis and identification of a long-span cable-stayed bridge.

Seismic Analysis of Long-Span Cable-Stayed Bridges by an Integrated Finite Strip Method

AbstractThis paper provides a very efficient, integrated framework for seismic analyses of long-span cable-stayed bridges. The efficiency comes from the dramatic reduction in formation time and the degrees of freedom (DOF) associated with the structure, using the integrated finite strip method (IFSM) along with the application of a very robust and efficient time history method (THM) using the Newmark scheme for dynamic analysis of the bridge structure. The previous versions of the finite strip method are limited to modeling the bridge deck only, whereas other structural components are replaced by assumed boundary conditions. Using the IFSM, all components of the long-span cable-stayed bridge can be modeled in a unified system, and consequently, the real dynamic behavior including the interactions between deck, piers, and cables can be perfectly considered. To verify the solution, the geometric and dynamic properties of the Kap Shui Mun (KSM) Bridge, as a real example of a long-span cable-stayed bridge, ar...

Numerical Analysis of Long-Span Cable-Stayed Bridge in the Construction Phase

The fabrication and erection of cable-stayed bridges involve major changes in structure configuration through the addition and removal of structure components. In every stage of the construction process, adequate information on the constructed structure is important to determine the real structure situation for the analysis of errors and to verify construction requirements. The ultimate goals are to meet construction needs and identify the effects of modification in subsequent construction procedures. The final configuration of the structure is strongly dependent on the construction and fabrication procedures. In this regard, developing an FEA model to simulate the actual construction processes is necessary to determine the performance of a bridge under external loads. In this study, a general methodology for construction processes is presented to simulate a cable-stayed bridge. The stage-by-stage construction of the Sutong Bridge is simulated with ANSYS software package. The tensions of cables are realized with ANSYS parametric design language, element birth and death function, and mutliframe restart function. The objective of the construction stage simulation is to identify stresses and deformations of the steel box girder and the concrete towers, as well as the cable tension stress, to meet the design requirements. Results of the construction stage analysis showed that the temperature method could simulate the adjustment of the inclined cable force successfully, and the global stiffness of the Sutong Bridge was very small before closure. These findings served as the initial data for a dynamic research on the Sutong cable-stayed bridge.

Seismic Reliability Analysis of Long-Span Cable-stayed Bridges

Earthquake motion is a random process, and thus, analyzing the seismic responses and dynamic reliability of cable-stayed bridges based on the random vibration theory is important. In this paper, dynamic reliability is investigated under earthquake loads by applying the stochastic vibration theory to the Sutong Yangtze River Highway Bridge. The response statistics are obtained from random vibration analyses, and the dynamic reliability of the normal stress of several key cross sections in the bridge is analyzed using the first-order second-moment method and the first-passage failure theory. The dynamic reliability analysis shows that the reliability index changes with girder section location and meets the design requirements. The analysis shows that the Sutong Bridge has adequate earthquake resistance ability. The structure’s earthquake resistance is appraised to provide an important theoretical reference for improving the seismic resistance design methods.

Earthquake-Response Analysis of Long-Span Cable-Stayed Bridge under Uniform and Non-Uniform Excitations

Earthquake is a kind of natural disaster which is difficult to predict and the damage degree is very great, occurrence of the strong motion often leads to the tremendous life and property loss. Bridge is very important lifeline engineering and it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, the FEM model of a long-span cable-bridge was established; the dynamic characteristic and nonlinear seismic responses under uniform and non-uniform excitations of it were systematic studied. The results show that: 1) the basic cycle of it is about 8.881s. Its first mode of vibration is longitudinal floating mode, which is favorable to the earthquake-response of structures. 2) Its former 40 rank frequency are located between 0.1~2Hz which is avail to the condition of traffic condition.3) the geometric nonlinearity has much influence on the response of this kind of bridge.4) the seismic responses are sensitive to the frequency spectra of the input earthquake wave. 5) The traveling wave excitations are unfavorable to the design of tower and the main girder when considering the three orthogonal seismic wave input. In order to get correct results, artificial seismic wave of the bridge address is necessary to the time-history analysis.

The Seismic Response Analysis of Long-Span Cable-Stayed Bridge

Anti-seismic property was essential in the progress of bridge designing and construction due to destructive power of earthquake disaster and increasing span of bridge. This paper elaborated theory method of analysis, taking five spans continuous cable-stayed bridge which was half floating system as an engineering background, and using method of special finite element analysis to calculating dynamic characteristics and seismic response respectively which also considered longitudinal limit damping and stiffness of cable under longitudinal, transverse, vertical and three-dimensional seismic oscillation. Fundamental frequency of cable-stayed bridge was affected significantly with considering longitudinal limit damping, so connection measures would be determined reasonably in designing and analyzing anti-seismic property of long-span cable-stayed bridge. When response spectrum analysis was adopted, longitudinal and vertical displacement were larger than lateral displacement under longitudinal seismic oscillation, lateral seismic oscillation only affected the structural lateral displacement, and vertical seismic oscillation affected vertical and longitudinal displacement.

Seismic response analysis of a double-deck long-span cable-stayed bridge under multi-support excitations

In this article, the effect of earthquake ground motions, especially spatially varying motion, on the seismic response of a long-span double-deck cable-stayed bridge is investigated. Static and dynamic response analyses, with the focus on internal forces on web members, are carried out on the Shanghai Minpu Bridge which is the longest long-span double-deck cable-stayed highway bridge. Firstly, a program for the generation of multi-ground motions has been developed, based on the multivariate stochastic processes of the weighted amplitude wave superposition method in FORTRAN. Secondly, a refined finite element model composed of beam and shell elements and a simplified model using equivalent beam elements to model girders of the bridge are established in ABAQUS. Geometrical nonlinear static analysis is performed to get initial equilibrium configuration of the bridge for both the above models. Modal analysis is carried out on the initial equilibrium configuration and the natures of mode shapes for the refined model are discussed in detail. The dynamic response analyses under two groups of uniform seismic excitation indicate that the two models result in approximately identical results. Thirdly, the effect of nonlinear viscous dampers, located between the tower and the girder, on movement due to seismic excitation is investigated on the simplified model under uniform excitation. Results show that the dampers magnify the shear force and moment on lower tower columns in the longitudinal direction, but have relatively small effect on the upper tower columns. The shear force and moment of the tower base increase with the damping coefficient in a certain range. Finally, the characteristics of internal force for towers, subsidiary piers, and web members (vertical and oblique web members and side oblique chords) under multipoint excitation are examined. It is concluded that the abrupt changes on the shear envelope curves at the intersection of the tower column and the lower transverse beam are aroused due to the eight nonlinear fluid viscous dampers. The lateral moment of the subsidiary piers increases with the distance from the tower to subsidiary piers. The maximum axial forces of web members of side-span vary acutely, especially those of the vertical and oblique members close to the piers. For side oblique chords, the maximum axial force is uniformly distributed with the exception of members at the piers and the mid-span sections. Therefore, attention should be paid to the fluctuation forces of cables in seismic analysis of long-span cable-stayed bridges, since the uplift of girder ends may cause severe damage to bridges.

Seismic Fragility Analysis of Long-Span Cable-Stayed Bridges

Seismic Fragility Analysis of Long-Span Cable-Stayed Bridges

Construction Control and Simulation Analysis of Long-Span Cable-Stayed Bridge

Simulation analysis is the basis for construction control of cable-stayed bridges, it monitors the process of the bridge construction. The relationship and importance of simulation and construction control are introduced in the paper. Based on the finite element theory and combined with construction theory of the cable -stayed bridges, according to use the software Midas/Civil, the construction characteristics of Masangxi Bridge is researched by making use of the forward calculation method and the backward calculation method. The results show that the system transformation of the bridge is occurred during the construction, thus, it is important to carry out careful and detailed forward simulation to ensure the safety of construction structure and meet with design requirements. The reasonable results can be drawn when the backward calculation method is combined with the forward calculation method.

Travelling Wave Effect Analysis of Long-Span Cable-Stayed Bridge

The vertical distance is generally greater of long-span cable-stayed bridge, while the velocity of seismic wave propagation is certain, therefore, the incentive suffered of long-span cable-stayed bridge’s pier is not the same time, but there is a certain time interval. Currently in the bridge designs, seismic response analysis is numerically based on coincident earthquake excitation, so that the actual results are different from the results of obtained widely. Based on the analysis of the traveling wave effect to the long-span cable-stayed bridge under the assumption of seismic waves, there are a series results of the bridge control point displacement, the maximum internal force of the earthquake response, and through these results, conclude some effective conclusions.