Multi-span Cable-stayed Bridge Research Articles

Pelješac bridge, Croatia – Part 2: Construction and Assembly/Pelješac-Brücke, Kroatien – Teil 2: Ausführung und Montage

The 2 404 m long Pelješac Bridge, Croatia ranks among the most demanding bridges in the Europe in terms of both the technological complexity of construction and the complexity of the design. The bridge is designed as a multi-span cable-stayed bridge with a semi-integral hybrid structure. While Part 1 (Bauingenieur 5/2023) dealt with the concept and planning of the bridge, the construction and assembly is reported now.

Pelješac bridge, Croatia – Part 1: Concept and Design/Pelješac-Brücke, Kroatien – Teil 1: Konzept und Planung

The 2 404 m long Pelješac Bridge, Croatia, ranks among the most demanding bridges in the Europe in terms of both the technological complexity of construction and the complexity of the design. The bridge is located in an area of very high seismic activity, exposed to strong and gusty north and south winds. The compact bedrock is located at a depth of up to 100 m below the seabed so very demanding foundation on up to 128 m long driven steel piles was required. The bridge is designed as a multi-span cable-stayed bridge with a semi-integral hybrid structure with five 285 m long central spans. Part 2 deals with execution and assembly.

Parametric Analysis of Multi-Span Cable-Stayed Bridges Under Alternate Loads

The influence of the stiffness of piers, pylons and deck in the behaviour of multi-span cable-stayed bridges under alternate live loads is analysed. The variation of these parameters is discussed considering both a harp cable system and a fan cable system. Different types of connections between pier-pylon and deck are also considered. Based on the behaviour of a three-span cable-stayed bridge, the variation of pier-pylon stiffness and deck stiffness was analysed. A similar state of stress and deflections was obtained for both a three-span and a multi-span cable-stayed bridge. The study shows that the harp type system presents advantages compared to fan type in terms of its behaviour under alternate live loads considering the same values of deck stiffness and pier-pylon stiffness. It is demonstrated that the resistant mechanism of multi-span cable- stayed bridges is provided by the pier-pylon element.

Optimum Criss Crossing Cables in Multi-span Cable-stayed Bridges using Genetic Algorithms

A multi-objective optimization approach in order to find the optimal cable overlap length in multi-span cable-stayed bridges with criss-cross cables is presented. The multi-objective optimization is solved by considering three objectives: 1) the cost of the cable system, 2) the displacement at the top of the pylon and 3) the alternate live load on the bridge. An unconventional criss-cross cable system configuration in which cables criss-cross at the center of intermediate spans is used for a bridge with five spans and four pylons. Taking into account both the cable overlap length and the different occurrences of alternate live load, the set of optimal solutions was obtained by the use of genetic algorithms. Results indicate that the optimal cable overlap length corresponds to three criss-crossing cables that corresponds to 0.28 times the length of the central span. Research on multi-span cable-stayed bridges with criss-cross cables allows the analysis of another solution for the problem of stabilizing the displacement of intermediate pylons in this kind of bridge.

Optimum crossing cable system in multi-span cable-stayed bridges

This paper presents a strategy to optimize the cable system of multi-span cable-stayed bridges with crossing stay cables. A general approach to minimize the steel volume in cables is performed considering number of cables, cable anchor positions on the deck, cable area and prestressing forces as design variables. Each cable anchor position is associated to an independent design variable allowing overlapping stay cables as well as different spacing along the deck. As the number of cables can vary throughout the bridge, the final design could have different number of cables on each side of the same tower. The possibility of designing a non-conventional cable arrangement leads to significant reductions in cable steel while satisfying structural design constraints. The Queensferry Crossing (UK) was chosen as a real application example to verify the capabilities of the proposed methodology.

A Comparative Assessment of Aerodynamic Models for Buffeting and Flutter of Long-Span Bridges

Abstract Wind-induced vibrations commonly represent the leading criterion in the design of long-span bridges. The aerodynamic forces in bridge aerodynamics are mainly based on the quasi-steady and linear unsteady theory. This paper aims to investigate different formulations of self-excited and buffeting forces in the time domain by comparing the dynamic response of a multi-span cable-stayed bridge during the critical erection condition. The bridge is selected to represent a typical reference object with a bluff concrete box girder for large river crossings. The models are viewed from a perspective of model complexity, comparing the influence of the aerodynamic properties implied in the aerodynamic models, such as aerodynamic damping and stiffness, fluid memory in the buffeting and self-excited forces, aerodynamic nonlinearity, and aerodynamic coupling on the bridge response. The selected models are studied for a wind-speed range that is typical for the construction stage for two levels of turbulence intensity. Furthermore, a simplified method for the computation of buffeting forces including the aerodynamic admittance is presented, in which rational approximation is avoided. The critical flutter velocities are also compared for the selected models under laminar flow.

Seismic fragility assessment of a multi-span cable-stayed bridge with tall piers

In this study, the longitudinal seismic fragility of a five-span cable-stayed bridge with tall piers is investigated using the fragility method. The OpenSees is applied to develop a finite element model of the cable-stayed bridge, and both the geometric and material nonlinearities are considered. A suite of 80 ground motions is selected to perform the nonlinear time history analysis, and the seismic responses of the expansion joint, deck, cables, and piers are discussed to determine the damage indexes of these components. Next, fragility curves are developed to assess the seismic performance of the cable-stayed bridge. The results show that the expansion joint, deck and cables are the vulnerable components, while the failure probability of the pier is relatively low. Moreover, the effects of the deck-pier connections and viscous fluid dampers on the vulnerability of the components and the bridge system are also studied. It is shown that the vulnerability of the cable and deck is sensitive to the deck-pier connections. Moreover, the deck-pier connection enhances the stiffness of the cable-stayed bridge. Therefore, it affects the seismic response of the cable-stayed bridge. However, the deck-pier connection has relatively slight effect on the system fragility. Furthermore, the location of the viscous fluid dampers significantly affects their effectiveness.

Wind resistant Design of Ngarai Sianok Bridge in Bukittinggi, West Sumatera - Indonesia

Ngarai Sianok Bridge is planned to cross the Sianok valley in Bukittinggi, West Sumatera Province, Indonesia. It will be a record breaking bridge in Indonesia in term of pier height. Its pair of 173.6 m tall pylon (elevation of deck is 123 m) are much taller than any bridges in Indonesia to date (2016). Another special feature of this bridge is the structural type: multi span cable-stayed bridge with 4 pylons and 3 main span of 170 m. The total length of the bridge is 685 m. This paper describes the wind resistant design process for the bridge: from design criteria and conceptual design to wind tunnel tests. Three wind tunnel tests were performed: static sectional test, full model test without terrain and full model test with terrain. Results from wind tunnel testing show that the design bridge is safe from flutter instability and vortex-induced vibration problem.

Structural characteristics of multi-span cable-stayed bridges with hybrid, RC and steel towers

Structural characteristics of multi-span cable-stayed bridges with hybrid, RC and steel towers

Mode identifiability of a multi-span cable-stayed bridge utilizing stabilization diagram and singular values

This study investigates the mode identifiability of a multi-span cable-stayed bridge in terms of a benchmark study using stabilization diagrams of a system model identified using stochastic subspace identification (SSI). Cumulative contribution ratios (CCRs) estimated from singular values of system models under different wind conditions were also considered. Observations revealed that wind speed might influence the mode identifiability of a specific mode of a cable-stayed bridge. Moreover the cumulative contribution ratio showed that the time histories monitored during strong winds, such as those of a typhoon, can be modeled with less system order than under weak winds. The blind data Acc 1 and Acc 2 were categorized as data obtained under a typhoon. Blind data Acc 3 and Acc 4 were categorized as data obtained under wind conditions of critical wind speeds around 7.5 m/s. Finally, blind data Acc 5 and Acc 6 were categorized as data measured under weak wind conditions.

Investigation of Influence Factors of Wind-Induced Buffeting Response of a Six-Tower Cable-Stayed Bridge

This paper presents an investigation of the wind-induced buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A three-dimensional finite element model for the Jiashao Bridge is established using the commercial software package ANSYS and a 3D fluctuating wind field is simulated for both bridge deck and towers. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects including the difference in the longitudinal stiffness between the side towers and central towers, partially longitudinal constraints between the bridge deck and part of bridge towers, self-excited aerodynamic forces, and the rigid hinge installed in the middle of the bridge deck. The analytical results can provide valuable references for wind-resistant design of multispan cable-stayed bridges in the future.

Passive Control System for Mitigation of Longitudinal Buffeting Responses of a Six-Tower Cable-Stayed Bridge

This paper presents an investigation of mitigation of longitudinal buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of longitudinal buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects of insufficient longitudinal stiffness of central towers and partially longitudinal constraints between the bridge deck and part of bridge towers. The effectiveness of viscous fluid dampers on the mitigation of longitudinal buffeting responses of the bridge is further investigated and a multiobjective optimization design method that uses a nondominating sort genetic algorithm II (NSGA-II) is used to optimize parameters of the viscous fluid dampers. The results of the parametric investigations show that, by appropriate use of viscous fluid dampers, the top displacements of central towers and base forces of bridge towers longitudinally restricted with the bridge deck can be reduced significantly, with hampering the significant gain achieved in the base forces of bridge towers longitudinally unrestricted with the bridge deck. And the optimized parameters for the viscous fluid dampers can be determined from Pareto-optimal fronts using the NSGA-II that can satisfy the desired performance requirements.

Time series synthetic aperture radar interferometry over the multispan cable-stayed Rio-Antirio Bridge (central Greece): achievements and constraints

The aim of the present study is to monitor by means of multitemporal synthetic aperture radar (SAR) interferometry the stability of the fully suspended cable-stayed Rio-Antirio Bridge (RAB) as well as the ground deformation of its surrounding area. The bridge is located in a region characterized by high hazard susceptibility, therefore, the monitoring of its behavior is of significant interest to mitigate potential risks. Envisat ASAR descending and TerraSAR-X ascending acquisitions were exploited using the persistent scatterer interferometry technique covering the periods 2002 to 2010 and 2010 to 2012, respectively. For both periods, ground displacement rates ranging from −12 to +12  mm/year indicate the absence of a significant deformation source acting during the period of investigation. Of interest is the differential motion pattern between Rio and Antirio for both SAR geometries, signifying the contribution of horizontal motion components, meanwhile allowing the quantification of the relative vertical displacement rates of these regions. For the RAB infrastructure, displacement histories were obtained from TerraSAR-X data analysis only for the stable part of the bridge, namely the viaducts and the four pylons, possibly due to the oscillation of its suspended part and the uncertainty of phase measurements over the pavement. The common behavior of the pylons was confirmed with an overall subsidence between −2 and −3  mm/year . The highest rates were observed for pylons established on specific soil types and were attributed to sediment consolidation.

Influence of structural system measures on the dynamic characteristics of a multi-span cable-stayed bridge

A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cable-stayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

Seismic response study on a multi-span cable-stayed bridge scale model under multi-support excitations. Part II: numerical analysis

In recent years, local component destruction, collapse failure and the control of long-span cable-stayed bridges under strong multi-support excitations have received increasing attention. In this paper, two kinds of nonlinear finite element (FE) models are established to simulate the seismic responses and failure modes of a multi-span cable-stayed bridge scale model under multi-support excitations. One is the single girder model which is used to simulate the seismic response during four wave excitations. It can be concluded that the FE analysis results of the scale model are a good fit with those from the shaking table tests. The other one is the explicit dynamic FE model which is used to simulate the collapse and failure mechanisms of the scale model during strong earthquakes. The aggressive failure processes of the scale model under two different types of wave excitations were compared to reproduce the mechanisms in which the bearing at the middle tower failed under the El Centro (EC) wave (4.0 m/s2), and we also observed the connection failure of the cables and towers, and the elements failure of the upper beam in the middle tower, which occurred successively under a Jiangxin (JX) wave (4.0 m/s2). This simulation may be referenced as the basis for the collapse failure of a cable-stayed bridge with a large span during a strong earthquake.

Seismic response study on a multi-span cable-stayed bridge scale model under multi-support excitations. Part I: shaking table tests

With the rapid development of bridge engineering in China, multi-span cable-stayed bridges have become one of the main structures of modern highways and railways for crossing rivers or straits. In this study, a 1:100 scale model of a three-tower cable-stayed bridge was tested using a shaking table array system. The mechanism associated with the seismic response of the scale model under uniform and non-uniform excitations was clarified. The results from the tests indicated that: (1) the strong vibration responses of the main girder and towers under four different horizontal earthquake wave excitations were identified, and the seismic responses of the scale model were most evident under uniform Jiangxin (JX) wave excitation; (2) the seismic performances of the main girder and towers of the scale model were adversely affected by traveling wave effects, especially when the wave velocity exceeded 616 m/s, which suggests that traveling wave effects should be considered in the seismic design of multi-tower cable-stayed bridges; (3) when the peak acceleration value of the El Centro (EC) wave reached 4.0 m/s2, shear failure of the bearing of the middle tower first appeared. This kind of shaking table tests will help to improve our understanding of dynamic performance, and will be especially useful in the design process and numerical simulation of multi-span cable-stayed bridges with large span subjected to spatially varying earthquake ground motions.

Nonlinear Analysis of Cable Vibration of a Multispan Cable-Stayed Bridge under Transverse Excitation

The nonlinear vibrations of cable in a multispan cable-stayed bridge subjected to transverse excitation are investigated. The MECS (multielements cable system) model, where multielements per cable stay are used, is built up and used to analyze the model properties of the multispan cable-stayed bridges. Then, a simplified two-degrees-of-freedom (2-DOFs) model, where the tower or the deck is reduced to a beam, is proposed to analyze the nonlinear dynamic behaviors of the beam and cable. The results of MECS model analysis show that the main tower in the multispan cable-stayed bridge is prone to the transverse vibration, and the local vibration of cables only has a little impact on the frequency values of the global modes. The results of simplified model analysis show that the energy can be transformed between the modes of the beam and cable when the nature frequencies of them are very close. On the other hand, with the transverse excitation changing, the cable can exhibit richer quasi-periodic or chaotic motions due to the nonlinear terms caused by the coupled mode between the beam and cable.

Ambient and free vibration tests of the Millau Viaduct: Evaluation of alternative processing strategies

The Millau Viaduct is an outstanding multi-span cable-stayed bridge located in southern France that opened to traffic in 2004. It is the tallest vehicular bridge in the world, with the top of a pylon rising at 343m above the river level, and due to its total length of 2460m, it also the longest cable-stayed bridge in the world. The present work aims to demonstrate the usefulness of ambient vibration tests performed at the commissioning stage and is specially focused on the evaluation of the efficiency and accuracy of alternative state-of-the-art processing strategies for identification of the modal parameters of the tested structure. Since both ambient and free vibration tests were performed, the modal damping ratio estimates obtained with the two testing approaches are compared. Furthermore, the natural frequencies and mode shapes provided by the ambient vibration test are correlated with modal estimates derived from a numerical model developed at the design stage. At the end, it is demonstrated that the data collected during the ambient vibration test, which only took some hours and very few resources, processed with adequate algorithms provided very useful information. It enabled the experimental identification of more than 20 natural frequencies and mode shapes that permitted the validation of their numerical counterparts and provided modal damping ratio estimates in good agreement with the values derived from the time series collected during the less economical and practical free vibration tests.

Static and seismic studies on steel/concrete hybrid towers for multi-span cable-stayed bridges

A new type of hybrid high tower is proposed and applied to a multi-span cable-stayed bridge. This is basically a sandwich type structure and consists of a steel double box section filled with concrete. The filled concrete increases its strength due to the confined effect and the steel plates increase the resistance against local buckling because the deformation is restricted by the filled concrete. Therefore, this hybrid tower is expected to have high bending and compressive strength, and also a good ductile property. First, static analysis is conducted for different live load intensity and distribution because the multi-span cable-stayed bridge is a new structure and its static behavior is not fully understood. The live loads distributed in alternate spans give larger bending moment of the towers than the live loads distributed in full spans. Towers with three different heights are also studied, showing that the higher tower produces smaller displacements and bending moments. Safety of the tower is checked by the limit states design method. Serviceability is not a major problem for the hybrid tower. Second, seismic analysis is carried out for a multi-span cable-stayed bridge subjected to the medium and ultra-strong seismic waves specified in Japanese Seismic Code for Highway Bridges. Three support conditions of the girder at the tower cross beams are compared: movable, connection with linear springs and bi-linear springs. Bi-linear springs are very effective in reducing the dynamic displacements and bending moments of the towers. Restorability of the composite tower is checked when an ultra-strong seismic wave hits the model bridge. This study shows that a new steel/concrete hybrid tower is feasible for multi-span cable-stayed bridges and most effective for seismic forces when the girder is connected with bi-linear springs.

Seismic Response Analysis of Multi-Span Cable-Stayed Bridge

Based on the dynamic characteristics analysis results of a precise three-dimensional finite element model, the earthquake responses of the bridge are analyzed in this paper. The influences of cable local modes and stabilizing cables on the seismic response are investigated by using different mode combinations and different models. It is found that the influence of cable local modes is negligible on the side towers while significant and not negligible on the main tower; the influence of the stabilizing cables is significant and not negligible on side towers, while minor and negligible on the main tower. As for the deck displacements, the influence of cable local modes is minor and negligible, while that of longitudinal stabilizing cables is significant and not negligible.