Response Of Cable-stayed Bridge Research Articles

Seismic response of cable-stayed bridge subjected to single-support excitation on various soil condition

For cable-stayed bridge, pylon and girder are one of the most important factors in the design process. Because of the length this structure, it needs to consider the type of the soil because different soil type can be resulting a different earthquake loads. In this study, the behavior of superstructure was investigated using time history analysis subjected to excitation uniformly on the pylon and girder. The test model was a cable-stayed bridge which classified as a long-span bridge. For obtaining the effects of soil type condition, different response spectrums are considered for three soil types: firm, medium, and soft soil. The response spectrums were thus converted to become ground acceleration time history and displacement time history. The displacement was then applied longitudinally and transversally to the supports of the structure to determine the behavior of the bridge. The result shows that the maximum displacement on the pylon and girder due to longitudinal load was at the top of the pylon and in the middle of the main span. As for the transverse earthquake load, the maximum displacement was in the middle area of the pylon and the middle of the main span. The results also defines that the displacement caused by firm soil is smaller than medium soil and soft soil.

Modeling and Separation of Thermal Effects from Cable-Stayed Bridge Response

Modeling and Separation of Thermal Effects from Cable-Stayed Bridge Response

A comprehensive study of the thermal response of a long-span cable-stayed bridge: From monitoring phenomena to underlying mechanisms

Abstract Structural deformation and variation in internal force are important considerations with regard to bridge health monitoring. Field measurements demonstrate that thermal effects of cable-stayed bridges—which represent high-order statically indeterminate structures—are extremely complex and nearly impossible to explicate in terms of temperature-limit states assumed during the design stage. Based on monitoring data recorded for the Shanghai Yangtze River Bridge—a steel box girder, twin-tower cable-stayed bridge with a 730 m central span—simultaneous investigations were performed concerning effects of seasonal as well as diurnal temperature variations on thermally induced changes in the mid-span vertical displacement ( D T ) and horizontal projection length ( L T ) of the girder, distance between the two tower tops ( S T ), structural total or elastic strains ( e M / e E ) at the mid-span section and average cable tensions of the longest centre-span cables ( F T ). In terms of variation amplitudes, correlations between temperature and structural response of a cable-stayed bridge can be classified into two modes. In the first mode, annual variation amplitudes are observed to be significantly larger compared with diurnal amplitudes. This applies to parameters L T , S T and e M . In the second mode, annual variation amplitudes approximately equal diurnal amplitudes. This is true for parameters D T , e E and F T . Temperature variables upon which structural response of cable-stayed bridges primarily depends usually differ from one another in that L T , S T and e M are governed exclusively by the average girder temperature while D T and F T are simultaneously determined by the cable and average girder temperatures; parameter e E is dominated by the temperature difference between the top and bottom plates of the girder. This study establishes a sound understanding of behavioural patterns in cable-stayed bridges to facilitate the determination of feasible measurement-point locations, useful with regards to bridge-monitoring systems, as well as selection of appropriate temperature variables for thermal-response modelling.

Structural response of cable-stayed bridge subjected to blast load

The recent increase number of terrorist attacks have accrued the vigilance from defense and securities organization of many countries. These entities collaborating with scientists allows providing a better insight into the structural performance of existing buildings subjected to pre-planned attacks. On the other hand, the explosive weapon is the most used methodology by the terrorists since they aimed to reach a consequent loss or damages. In this paper, the structural performance of a generic cable-stayed bridge under blast loading is assessed throughout an extensive numerical analysis. Firstly, a though non-linear analysis is performed to under the ultimate capacity of a generic cable-stayed bridge, then it was possible to simulate the damage induced by the dynamic effect of a high impact action and finally considering different magnitudes of impact load, the failure state of the bridge is highlighted.

Longitudinal seismic responses of a cable-stayed bridge based on shaking table tests of a half-bridge scale model

This article studies the seismic response of a symmetric long-span cable-stayed bridge under longitudinal uniform excitations by finite element analysis and shaking table tests. The feasibility and method of performing shaking table tests are examined using a simplified half-bridge scale model. By taking advantage of the symmetry, it is possible to construct a scale model with a larger scale ratio than a full-bridge scale model. The main components of the scale model (i.e. tower, piers, girder, and cables) were fabricated using the same or similar materials as in the prototype. The design and construction of the scale model is presented. Longitudinal structural responses obtained from the finite element analysis and shaking table tests are compared. The seismic mitigation effects of viscous dampers are examined through shaking table tests.

Effectiveness of Soil–Structure Interaction and Dynamic Characteristics on Cable-Stayed Bridges Subjected to Multiple Support Excitation

The purpose of the study is to determine the effects of multiple support excitations (MSE) and soil–structure interaction (SSI) on the dynamic characteristics of cable-stayed bridges founded on pile foundation groups. In the design of these structures, it is important to consider the effects of spatial variability of earthquake ground motions. To do this, the time histories of the ground motions are generated based on the spatially varying ground motion components of incoherence, wave-passage, and site-response. The effects of SSI on the response of a bridge subjected to the MSE are numerically illustrated using a three-dimensional model of Quincy Bayview cable-stayed bridge in the USA. The soil around the pile is linearly elastic, homogeneous isotropic half space represented by dynamic impedance functions based on the Winkler model of soil reaction. Structural responses obtained from the dynamic analysis of the bridge system show the importance of the SSI and the MSE effects on the dynamic responses of cable-stayed bridges.

Optimization of longitudinal viscous dampers for a freight railway cable-stayed bridge under braking forces

Under braking forces of a freight train, there are great longitudinal structural responses of a large freight railway cable-stayed bridge. To alleviate such adverse reactions, viscous dampers are required, whose parametric selection is one of important and arduous researches. Based on the longitudinal dynamics vehicle model, responses of a cable-stayed bridge are investigated under various cases. It shows that there is a notable effect of initial braking speeds and locations of a freight train on the structural responses. Under the most unfavorable braking condition, the parameter sensitivity analyses of viscous dampers are systematically performed. Meanwhile, a mixing method called BPNN-NSGA-II, combining the Back Propagation neural network (BPNN) and Non-Dominated Sorting Genetic Algorithm With Elitist Strategy (NSGA-II), is employed to optimize parameters of viscous dampers. The result shows that: 1. the relationships between the parameters of viscous dampers and the key longitudinal responses of the bridge are high nonlinear, which are completely different from each other; 2. the longitudinal displacement of the bridge main girder significantly decreases by the optimized viscous dampers.

SEISMIC RESPONSE ANALYSIS OF LONG-SPAN CABLE-STAYED BRIDGE WITH NONLINEAR VISCOUS DAMPERS UNDER DIFFERENT PERIODIC SEISMIC WAVES

In order to study the effect of nonlinear viscous dampers on the seismic response of long-span cable-stayed bridge under different periodic seismic waves, as Erdong Yangtze River Bridge which main span is 926 meters in Hubei province of China for the research object, nonlinear viscous dampers are simulated by Maxwell model, and four viscous dampers are set at the joint of main tower and beam. The displacement and internal force responses of cable-stayed bridge with different velocity index and damping coefficient of nonlinear viscous dampers are analysed and discussed, in the situation of that long period and ordinary period seismic waves are input as earthquake motions. Analysis results show that: the displacement and internal force responses of long-span cable-stayed bridge under long period seismic wave are more negative; the displacements of key nodes of bridge can be reduced effectively by nonlinear viscous dampers; the internal force responses of bridge would be influenced greatly by the combination of different parameters of viscous dampers; the growth of shear and bending moment at the bottom of the tower can be controlled in an acceptable range by the reasonable parameter combination; the ideal parameter combination is that velocity index of viscous damper is 0.6 and the damping coefficient is 7000 N.(s/m)α for this cable-stayed bridge under long-period seismic wave.

Experimental investigations on seismic control of cable-stayed bridges using shape memory alloy self-centering dampers

This paper presents the experimental investigations of a novel self-centering damper (SCD) for controlling seismic responses of cable-stayed bridges. The damper is fabricated employing the super-elasticity effect and energy dissipation characteristics of shape memory alloy wires. Within super-elastic range, a damping force model is derived and verified based on the constitutive model of shape memory alloy wires. One reduced-scale cable-stayed bridge model is designed to investigate its seismic control performance. Two different system configurations of the cable-stayed bridge model are considered, including the without control state and incorporating with the SCD between the tower and the deck. Seismic behavior of different cable-stayed bridge systems is then evaluated via shaking table tests under different ground excitations. Experimental results show the effectiveness of the SCD. The accelerations and the relative displacements of the tower reduce obviously due to the energy dissipation of the SCD. Relative displacements of the deck decline dramatically because of the connection of the SCD. Moreover, the strain responses also indicate the drop of the bending moment in the tower.

Seismic responses of super-span cable-stayed bridges induced by ground motions in different sites relative to fault rupture considering soil-structure interaction

The focus of this paper is to evaluate the seismic response of a cable-stayed bridge built in fault zones considering soil-structure interaction (SSI) effects. Bridges crossing fault-rupture zones may be built in the Forward Region (FR), Middle Region (MR) and Backward Region (BR) relative to the possible position of the fault. Three groups of ground motions (51 records in two orthogonal directions) in above regions are selected as the input from the 1999 Taiwan Chi-Chi earthquake based on the sites relative to the fault rupture. The Sutong Cable-stayed Bridge (SCB) is taken as an example. Two models are used in this study, i.e. the fixed-base bridge and the bridge with SSI effects where four different orientation angles (0°, 30°, 60°, and 90°) have been considered compared to the fault direction. Systematic lumped-parameter models are utilized to represent the dynamic behavior of the foundation supported on soil. The results reveal that the seismic behavior of the SCB in those 3 regions shows significant differences. The SSI effects affect the bridge response through a systematic decrease of all modal frequencies and a substantial change in nature of dominant shapes especially for the higher modes of vibrations. The displacement of such bridges may be underestimated if the SSI effects are ignored. The orientation of the bridge axis relative to fault trace influences the seismic responses of the bridges in fault regions. The bridge located in MR experiences larger responses than that in FR and BR. Due to the high values of velocity spectra, velocity-related intensity measures i.e. peak ground velocity (PGV) and the ratio of PGV to peak ground acceleration (PGA) show strong correlation with the seismic responses of the bridge located in FR. Since the records in MR and BR have high acceleration spectra, PGV and PGA correlate well with the responses of the bridge located in MR and BR.

Effect of spatial variability of earthquakes on cable-stayed bridges

This paper focuses on the effect of spatially variable ground motions on the towers of cable-stayed bridges with 200, 400 and 600 m main spans. Seismic analysis of the bridges is performed, taking account of different sources of the spatial variability, namely; incoherence and wave passage effects. To address these effects, the response of the towers is assessed under the effect of different propagation velocities of the seismic waves and different assumptions on the coherency of the ground motion, to conclude that the effect of spatially variable motions on the seismic response of cable-stayed bridges is dependent on the assumed wave propagation velocity and rate of coherency.

Seismic Responses of a Cable-Stayed Bridge with Consideration of Uniform Temperature Load

The effects of temperature load on the dynamic responses of cable-stayed bridges have attracted the attention of researchers in recent years. However, these investigations mainly focus on the influence of temperature on the dynamic characteristics of structures, such as vibration mode and frequency. This paper discusses the effects of uniform temperature changes on the seismic responses of a cable-stayed bridge. A three dimensional finite element model of a cable-stayed bridge using OpenSees is established for nonlinear time history analysis, and uniform temperature load is applied to the prototype bridge before the conducting of seismic excitation. Three ground motion records are selected from the PEER strong motion database based on the design spectrum. Case studies are then performed considering the varying temperature and the connections between the deck and pylons of the bridge. The result shows that the seismic responses of the bridge are significantly increased with the consideration of temperature load. Meanwhile, the types between the deck and pylon also have notable impacts on the seismic responses of the bridge with and without temperature changes. This research could provide a reference for designers during the design phase of cable-stayed brides.

Dynamic response of cable-stayed bridge under blast load

Over the past two decades, blast loads have been recognised as one of the extreme loading events that must be considered in the design of important structures such as cable-stayed bridges. However, design provisions for blast-resistant bridges are very limited and mostly empirical owing to an inadequate understanding of the local and global dynamic response of the bridge components (piers, deck and cables) subjected to blast loading scenarios. Accordingly, this study develops detailed finite element models of a steel cable-stayed bridge and it is analysed using an explicit solver. Three different explosive sizes, i.e. small (01W), medium (04W) and large (10W), are considered (W being the TNT equivalent explosive weight index) and placed at different locations above the deck level to determine the influence of the size and location of the blast loads on the global and local response of the bridge components. In particular, the results of the computer simulations are employed to characterise the type and extent of damage on the pylon and deck, and additionally to investigate the potential cable loss scenarios associated with a loss of anchorage. Furthermore, the results of the finite element simulations are used to assess the potential progressive collapse response of a cable stayed bridge subject to various blast loading scenarios.

Deck–tower interaction in the transverse seismic response of cable-stayed bridges and optimum configurations

Modern design solutions in cable-stayed bridges give a significant importance to the seismic response in the transverse direction. This work is focused on the dynamic interaction between the deck and the towers, exploring the key role of different vibration modes. An extensive parametric analysis is proposed to address the influence of the main span length, the tower geometry, the cable-system arrangement, the width and height of the deck and the soil conditions. It is demonstrated that the vibration modes that govern the seismic response of cable-stayed bridges in the transverse direction involve the interaction between the tower and the deck, but the order of these modes and the parts of the deck that are affected change with the main span length. It is also observed that the interaction between the deck and the towers during the earthquake is maximised if their isolated vibration frequencies are close to each other, leading to a significantly large seismic demand. Analytical expressions are proposed to obtain the critical frequencies of the towers for which these interactions arise, and recommendations are given to define the tower geometry in order to avoid such problematic scenarios.

Identification of horseshoes chaos in a cable-stayed bridge subjected to randomly moving loads

In this paper, the dynamic response of cable-stayed bridge loaded by a train of moving forces with stochastic velocity is investigated. The cable-stayed bridge is modelled by Rayleigh beam with linear elastic supports. The stochastic Melnikov method is derived and the mean-square criterion is used to determine the effects of stochastic velocity and cables number on the threshold condition for the inhibition of smale horseshoes chaos in the system. The results indicate that the intensity of the random component of the loads velocity can be contributed to the enlargement of the possible chaotic domain of the system, and/or increases the chances to have a regular behavior of the system. On the other hand, the presence of cables in cable-stayed bridges system increases it degree of safety and paradoxically can be contributed to its destabilization. Numerical simulations of the governing equations are carried out to confirm the analytical prediction. The effect of loads number on the system response is also investigated.

Intelligent active control of a benchmark cable-stayed bridge

A neural-fuzzy control strategy for cable-stayed bridge structures subjected to earthquake excitation is presented by employing electromagnet-driven active mass dampers (EMDs). The active EMD is an innovative control device for the earthquake response mitigation of structures. Ensuring fast selection of the control voltage in accordance with the characteristics of seismically excited bridge structures is one of the most important problems for EMD systems. In the proposed control strategy, a neural-network technique is used to solve the time-delay problem, and fuzzy logic algorithms are used to determine the control voltage from the response of the EMD. The control performance of the proposed neural-fuzzy control strategy was analysed for the benchmark control problem of a seismically excited cable-stayed bridge with an EMD system. The simulated results show that the proposed active neural–fuzzy control strategy can quickly determine an accurate voltage for the EMD system, and mitigate the seismic response of cable-stayed bridges.

Integrated Analysis Model for the Seismic Responses of Cable-Stayed Bridges Near Active Faults

To study the special behaviors of seismic responses regarding a cable-stayed bridge under an active fault earthquake, a novel numerical algorithm named Structure-Medium-Fault (SMF) Integrated Model, in which the interaction of the three parts can be considered, is proposed. The mechanical simplification of causative faults' rupture, numerical simulation of stress wave propagation and the artificial boundary conditions (ABC) for the infinite body laid the groundwork of this model. Initially, the mechanical model for the structures and earth medium was established. Afterwards, the equivalent initial stresses of causative seismic sources can be calculated according to the monitored data of active faults. Thirdly, the function of the equivalent initial stress of seismic source time was derived by the second derivation of Brune source function. Finally, the viscoelastic boundary was chosen for the model as ABC. A cable-stayed bridge (600 m main span) above the causative fault was analyzed using the novel model. Consequently, vertical effect, velocity pulse effect and directivity effect were all confirmed by the analytical results. The model can reflect the mutual influences of near-fault structures, medium and causative faults. The seismic responses of the bridge under a near-fault earthquake can thus be obtained.

Effect of loading pattern and deck configuration on the progressive collapse response of cable-stayed bridges

Effect of loading pattern and deck configuration on the progressive collapse response of cable-stayed bridges

Effect of Loading Pattern and Deck Configuration on the Progressive Collapse Response of Cable-Stayed Bridges

In the cable stayed-bridges, sudden loss of cables is usually associated with material as well as geometrical non-linearities that may trigger progressive collapse of the entire bridge. Accordingly, in this paper detailed 3D finite element models of a hypothetical cable-stayed bridge is developed and analysed with material and geometrical non-linearities included. A parametric study is undertaken and effect of cable loss scenarios (symmetric and unsymmetric), deck configurations (steel box girder and open orthotropic deck) and number of lost cables on the progressive collapse response of the bridge is investigated. With regard to the results of parametric study, it is concluded that the deck configuration has a minor influence on the progressive collapse response of cable-stayed bridges. Also, it is shown that localised yielding of steel may occur following loss of more than one cable, however, such localised plastic strains cannot trigger the progressive collapse of the entire bridge. During cable loss scenarios, the reduction in post-tensioning stress and subsequently stiffness of the remaining cables (reflected in Ernst’s modulus) is found to be around 10% that warrants effect of geometrical non-linearities within the cables being considered.

Dynamic response of cable-stayed bridges subjected to sudden failure of stays - the 2D problem

A significant problem met in engineering practice when designing cable-stayed bridges is the failure of cables. Many different factors can lead to sudden failure of cables, such as corrosion, continuous friction or abrasion, progressive and extended crevice created by fatigue and finally an explosion caused by sabotage or accident, are some of the causes that can lead to the sudden failure of one or more cables. This paper deals with the sudden failure of cables in a special form of cable-stayed bridges with a single line of cables anchored at the central axis of the deck's cross-section. The analysis is carried out by the modal superposition technique where an analytical method developed by the authors in a previous work has been employed.