Concrete Cable-stayed Bridge Research Articles

Damage detection under environmental and operational effects using cointegration analysis – Application to experimental data from a cable-stayed bridge

Abstract One of the main challenges that Structural Health Monitoring (SHM) faces when transitioning from academia to real-world applications is the discernment between structural changes due to damage and normal environmental, operational and long-term effects. In this context, a strategy for early damage detection based on multivariate cointegration analysis and statistical process control is proposed. The effects of environmental and operational variations are suppressed using cointegration analysis, being the cointegrating vector estimated following the multivariate Johansen procedure. The cointegrated residuals are then used for novelty detection by means of the Hotelling T2 control chart. The proposed strategy is systematised and is applied to a large prestressed concrete cable-stayed bridge of which 3.5 years of data are available, being the stay-cable forces used as damage sensitive-features. Several damage scenarios are studied involving increasing section loss of the stay cables. The damage intensities that can be detected using the proposed methodology and the available sensory system are quantified.

Online early damage detection and localisation using multivariate data analysis: Application to a cable‐stayed bridge

An online data-based methodology for early damage detection and localisation under the effects of environmental and operational variations (EOVs) is proposed. The methodology is described in detail and implemented in a large prestressed concrete cable-stayed bridge of which 3.5 years of data are available. The effects of EOVs are suppressed by the combined application of two well-established multivariate data analysis methods: multiple linear regression and principal component analysis. Criteria for the systematic choice of the predictor variables and the number of principal components to retain are proposed. Because the bridge is new and sound, the experimental time series are corrupted with numerically simulated damage scenarios in order to evaluate the damage detection ability. It is demonstrated that the sensitivity to damage is increased when daily, 2-day, or 3-day averaged data are used instead of hourly data. The effectiveness of the proposed methodology is also demonstrated with the detection of a real, small, and temporary sensor anomaly. The implemented methodology has revealed to be robust and efficient, presenting a contribution to the transition of structural health monitoring from academia to industry.

Assessment of a concrete cable-stayed bridge after replacement of the closure segment

The concept of replacement of the closure segment (RCS) emerged originally in a strengthening project for a concrete cable-stayed bridge and was intended to deal with a failure in the closure segment of the main girder. The construction procedure of RCS includes removing the failed closure segment, reconstructing the closure segment and finally improving the connection between the new closure segment and the original residual part of the main girder. Thus, a relatively complex conversion in structural state is involved. To assess the completed bridge after RCS, a finite-element model of a typical bridge is developed by using the software Dr. Bridge, and then a construction stage analysis is performed in the present study. Numerical results show that RCS eradicated the hidden structural safety danger while the structural integrity was improved to a certain extent. However, RCS had no significant influence on the geometric profile of the bridge deck, on the horizontal displacement at the top of each pylon and on tensions in the cable stays. As the stress condition in the new closure segment and associated joints between segments could not be improved by mere RCS, other strengthening measures should be taken to achieve a further structural state adjustment for the completed bridge. As a novel strengthening idea, RCS has a comparable advantage and remarkable economic benefit in dealing with local failure in the structure. Inevitably, it has some limitations in practical use.

Girder crack of concrete single pylon cable-stayed bridge

Taking the reinforcement and maintenance project of a concrete cable-stayed bridge as the background, aiming at the stress cracks on the web of the box girder of the main bridge after several years of operation, starting from the actual situation of design and construction, the integral calculation model of the bridge is established by Midas Civil and the local analysis and calculation model of the main girder is established by the general finite element software. Four kinds of analysis and calculation models are analyzed. Finally, it is shown that the web cracks of the bridge are caused by the cable tension when the bridge is cantilevered. On this basis, the concrete and feasible bonded steel plate method is proposed to repair and strengthen the cracks, which is of certain reference significance for the reinforcement and maintenance of the same type of bridge cracks in the future.

Practical Design Method of Yielding Steel Dampers in Concrete Cable-Stayed Bridges

Restrained transversal tower/pier–girder connections of cable-stayed bridges may lead to high seismic demands for tower columns when subject to earthquake excitations; however, free transversal tower/pier–girder connections may cause large relative displacement. Using an energy dissipation system can effectively control the bending moment of tower columns and the relative tower/pier-girder displacement simultaneously, but repeated time history analyses are needed to determine reasonable design parameters, such as yield strength. In order to improve design efficiency, a practical design method is demanded. Therefore, the influence of yielding strength at different locations is studied by using comprehensive and parametric time history analyses at first. The results indicate that yielding steel dampers can significantly reduce the bending moment at tower columns and the relative pier–girder displacement due to the system switch mechanism during the vibration. Meanwhile, the yielding steel damper shows its general effect on reducing relative displacement between all piers/tower columns and the main girder as well, with only a localized effect on controlling seismic induced forces. Furthermore, a practical design method is proposed for engineering practices to determine key parameters of the yielding steel damper.

Optimization of concrete cable-stayed bridges under seismic action

A computational tool is presented for the optimum design of concrete cable-stayed bridges under seismic action. The finite element method is used for the three-dimensional analysis of the structure under dead and live loads, time-dependent effects and geometrical nonlinearities are considered. The dynamic analysis is solved by the modal/spectral approach. The design problem is posed as a multi-criteria optimization. The design variables are the cable forces and the cross-sectional dimensions of cables, deck and towers. Design objectives of minimum cost, deflections, natural frequencies and stresses considering both, serviceability and ultimate limit states are considered. Given that a gradient-based algorithm is applied for the optimization the discrete direct method is used for sensitivity analysis. An entropy-based algorithm finds economically and structurally efficient solutions by rearranging the stiffness and mass distribution to enhance the structural response. Numerical examples illustrate the features of the proposed computational tool.

Design and behavior of super-long span cable-stayed bridge with CFRP cables and UHPC members

This paper proposes a cable-stayed bridge with carbon fiber-reinforced polymer (CFRP) cables and ultra-high performance concrete (UHPC) members and presents its design and structural behavior to analyze its feasibility with a super-long span. Based on the geometrical dimensions of a real cable-stayed bridge with a steel girder and cables in addition to a normal concrete (NC) pylon and main-span of 1088 m, a new counterpart cable-stayed bridge using CFRP cables and a UHPC girder and pylon was designed. The dimensions of the UHPC girder were quantified by the section stiffness, punching resistance, local stability, and shearing resistance. The cross-section sizes of the CFRP cables were determined by the principle of equivalent strength. The geometric and physical conditions of the UHPC pylon satisfied the principle of similarity theory. Using the finite element method, a comparative analysis of the mechanical behavior of two cable-stayed bridge schemes was conducted, specifically regarding the static behavior, global stability, aerostatic stability, dynamic mode, and seismic performance. The results indicated that the detailed design and superior performance of the CFRP and UHPC made it practical to form a highly efficient and durable concrete cable-stayed bridge system with CFRP cables and UHPC members. Moreover, these properties could enlarge the main-span of a concrete cable-stayed bridge to approximately 1000 m.

Structural response of a concrete cable-stayed bridge under thermal loads

Daily and seasonal temperature variations have a significant influence on the structural response of bridges, inducing strains, displacements or rotations of the same order of magnitude, or even larger, than those due to dead or live loads. Besides understanding the structural behaviour under the operational loads, the characterization of the structural response induced by the daily and seasonal temperature variations is mandatory for the critical assessment of the bridge structural condition and when proactive conservation is envisaged. In this study, a methodology is proposed for the simulation of the structural response of large concrete bridges under the effects of realistic temperature variations, aiming at the optimum compromise between accuracy and simplicity of the involved procedures. The transient temperature field in a set of representative cross-sections is obtained from the available meteorological data via two-dimensional thermal analyses. The temperature field is decomposed into uniform, linear and non-linear components, the former two being introduced in a mechanical model of the bridge to obtain the transient structural response. The methodology is applied to a concrete cable-stayed bridge equipped with a permanent structural monitoring system. The measured and calculated hourly temperatures, deflections, bearing displacements, rotations and stay-cable forces are compared during a period of 17 months and good agreement is generally found. The consideration of the radiative cooling effects is demonstrated to be essential in other to obtain a good estimation of the thermal field of the bridge. The behaviour of the bridge is discussed and the relative contribution of each temperature component to a given structural response is disclosed. A discussion on the optimal deployment location of a minimum set of embedded temperature sensors in order achieve the best estimators of the temperature components (uniform and linear) is also presented.

Structural Health Monitoring System of a Concrete Cable-Stayed Bridge

Abstract In this paper a system of the Rędziński bridge will be described. The Rędziński bridge is the biggest object along the A8 motorway around the city of Wrocław and the biggest concrete cable-stayed bridge in Poland. For the purposes of the bridge monitoring a system of 222 sensors was installed. Results from the first 5 years of work of the SHM will be presented below.

矮塔混凝土斜拉桥成桥索力优化分析

矮塔混凝土斜拉桥成桥索力优化分析

Parameters analysis of earth-anchored preseressed concrete cable-stayed bridge with single pylon based on totally rigidity

Parameters analysis of earth-anchored preseressed concrete cable-stayed bridge with single pylon based on totally rigidity

Design of Main Bridge of Second Penang Bridge in Malaysia

The main bridge of the Second Penang Bridge in Malaysia [1-2] is a two-pylon three-span prestressed concrete cable-stayed bridge, with span arrangement of (117.5+240+117.5) m.The pylons and the main girder are monolithic. The main girder, which is 34.6m wide, adopts the ladder type concrete deck section comprising top slab, transverse diaphragms and edge beams. The pylons are H-form pylons, and the stay cables are formed of parallel strands and are arranged in fan cable planes. Each pylon column carries 18 pairs of stay cables that are anchored by the deviation saddles in the pylons and anchor blisters in the main girder. The foundations consist of large diameter bored piles, varying from 2.3m to 2.0m in diameter. An optimized design scheme is tailored for the bridge, in which the main girder has the cross-section built up by a combination of slab, diaphragm and edge beam structuresand was constructed by using the rear supported form traveler and incorporating an optimization of construction timing. The scheme resolved the problems of load-bearing capacity verification for bridge deck and the verification of main girder prestress under the heavy vehicle loads prescribed in the BS5400. Meanwhile, a meticulous calculation method was put forward for the design and analysis of the main girder, to obtain the real load bearing conditions of the main girder and the bridge deck. The diaphragms were calculated by the spatial grillage analysis method, aimed at guaranteeing the load-bearing safety of the structure.

Structural health monitoring data reconstruction of a concrete cable-stayed bridge based on wavelet multi-resolution analysis and support vector machine

The accuracy and integrity of stress data acquired by bridge heath monitoring system is of significant importance for bridge safety assessment. However, the missing and abnormal data are inevitably existed in a realistic monitoring system. This paper presents a data reconstruction approach for bridge heath monitoring based on the wavelet multi-resolution analysis and support vector machine (SVM). The proposed method has been applied for data imputation based on the recorded data by the structural health monitoring (SHM) system instrumented on a prestressed concrete cable-stayed bridge. The effectiveness and accuracy of the proposed wavelet-based SVM prediction method is examined by comparing with the traditional autoregression moving average (ARMA) method and SVM prediction method without wavelet multi-resolution analysis in accordance with the prediction errors. The data reconstruction analysis based on 5-day and 1-day continuous stress history data with obvious preternatural signals is performed to examine the effect of sample size on the accuracy of data reconstruction. The results indicate that the proposed data reconstruction approach based on wavelet multi-resolution analysis and SVM is an effective tool for missing data imputation or preternatural signal replacement, which can serve as a solid foundation for the purpose of accurately evaluating the safety of bridge structures.

Assessment of the Current State of Internal Force and the Optimization of Cable Force for an Existing Long-span Pre-Stressed Concrete (PC) Cable-stayed Bridge

Introduction: Due to the influence of load, fatigue, corrosion, natural material aging and other long-term adverse factors, the state of the internal force of a cable-stayed bridge will be changed. These long-term effects can result in the bridge not meeting specified functional requirements, and potentially resulting in structural failure. This investigation focuses on the parameter identification of a girder for a pre-stressed concrete (PC) cable-stayed bridge. Without considering the influence of cable relaxation and temperature on the girder’s geometric shape, an improved method based on the “cable force-girder’s displacement” relationship is proposed. Method: In this method, measurement variations of displacement and cable force are simultaneously obtained, enabling the use of an optimization method to identify parameters which need to be resolved. To verify the proposed method, a single pylon PC cable stayed bridge (2×160m) is selected as a case study. For the state of internal force, results from the case study bridge indicate that the crack resistance value of the girder no longer satisfies the demand of Generalized codes for design of highway bridges and culverts(JTG D60-2004,in Chinese). In order to adjust the internal force, cable force optimization was undertaken, whereby bending energy was taken as the objective function. Result: Using these results the geometric shape of the girder was restored to its initial state. The results also show that neither the crack resistance value nor the compression resistance value of the girder exceeded specified limits, and that the stress of the girder was effectively controlled.

Creep and Shrinkage Effects of Prestressed Concrete Cable-stayed Bridge During Segmental Construction

During segmental construction of prestressed concrete cable-stayed bridges, the age-adjusted effective modulus method is used to perform the structural analysis. The effect of creep and shrinkage is converted into equivalent nodal loads by the linear creep theory. Loss of prestress and the effect of ordinary tendon are considered in the derivation. The effect of tendon is calculated using the limit equilibrium method. A calculation procedure is programmed via the above-mentioned method for analyzing construction process of cable-stayed bridges. The Hemaxi bridge, built recently in China is then taken as a case study. The study shows the measured data of elevations of some sections agrees well with the results of the calculation procedure. This demonstrates the proposed method is efficient and reliable.

Influence of Antisymmetrical Actions at Reinforced Concrete Cable-Stayed Bridge

Calculation of the cross-sectional properties of the concrete box-girder with two-cells using Vlasov`s theory and Generalized Beam Theory. Calculation of the internal forces of the St. Venant torsion, the warping torsion, the antisymmetrical and the symmetrical distortion on the basis analogy with beam on the elastic foundation loaded by transverse actions and tension force at the end of the beam. Creating of influence lines of torsion, antisymmetrical distortion and symmetrical distortion internal forces of large concrete cable-stayed bridge with continuous box-girders with two spans. The application for real reinforced concrete Harp bridge over pond Jordán near Tábor in Czech Republic is investigated. Evaluation of internal lines for action according to Eurocode EN 1991-2.

A multi-parameter optimization technique for prestressed concrete cable-stayed bridges considering prestress in girder

The traditional design procedure of a prestressed concrete (PC) cable-stayed bridge is complex and time-consuming. The designers have to repeatedly modify the configuration of the large number of design parameters to obtain a feasible design scheme which maybe not an economical design. In order to efficiently achieve an optimum design for PC cable-stayed bridges, a multi-parameter optimization technique is proposed. In this optimization technique, the number of prestressing tendons in girder is firstly set as one of design variables, as well as cable forces, cable areas and cross-section sizes of the girders and the towers. The stress and displacement constraints are simultaneously utilized to ensure the safety and serviceability of the structure. The target is to obtain the minimum cost design for a PC cable-stayed bridge. Finally, this optimization technique is carried out by a developed PC cable-stayed bridge optimization program involving the interaction of the parameterized automatically modeling program, the finite element structural analysis program and the optimization algorithm. A low-pylon PC cable-stayed bridge is selected as the example to test the proposed optimization technique. The optimum result verifies the capability and efficiency of the optimization technique, and the significance to optimize the number of prestressing tendons in the girder. The optimum design scheme obtained by the application can achieve a 24.03% reduction in cost, compared with the initial design.

Transverse Seismic Behavior Studies of a Medium Span Cable-Stayed Bridge Model with Two Concrete Towers

Due to lack of investigation on nonlinear seismic behavior of cable-stayed bridges under strong earthquake excitation, the concrete towers, as the main gravity-carrying component, are usually required to remain nearly elastic. However, in order to achieve this high seismic performance objective, the reinforcement ratio of the tower legs and the tower struts need to be greatly increased in addition to its static loading requirement. To study the potential plastic region and possible failure mode of the cable-stayed bridge, a 1/20-scale full bridge model from a typical medium span concrete cable-stayed bridge was designed, constructed and tested on 4 linear shake tables using a site specific artificial wave in the transverse direction. Test results showed that the damage characteristics of the bridge model were as follows: (1) the severe damage was observed at the upper strut, with several steel bars fractured at both ends; (2) the repairable damage was observed at tower legs at the bottom and the middle part, with concrete cover spalling and exposure of steel bars; (3) the minimal damage was observed at the lower strut and the both sides of the side bents, with only slightly concrete spalling; and (4) no damage was observed at the auxiliary bents, the superstructure and the cables. Numerical results and test results were further compared and showed good agreement in low amplitudes of excitations. The test also proved that the bridge system was stable in flexural failure of upper struts, and had the negligible residual displacement subjected to high amplitudes of excitations.

Optimum design of concrete cable-stayed bridges with prestressed decks

ABSTRACTThis article presents an optimization-based numerical method for the design of concrete cable-stayed bridges with prestressed decks. This method includes a structural analysis module and a sensitivity analysis and optimization module. The structural analysis considers concrete time-dependent effects, construction stages and geometrical nonlinearities. The discrete direct method is used for sensitivity analysis and an entropy-based approach is used for structural optimization. The design is formulated as a multi-objective optimization problem with objectives of minimum cost, minimum deflections and stresses. Numerical examples concerning the optimization of a real sized cable-stayed bridge are presented to illustrate the applicability of the proposed method.

Experimental Verification of a Cable-Stayed Bridge Model Using Passive Energy Dissipation Devices

To investigate the efficiency of passive energy dissipation devices in protecting cable-stayed bridges from severe damage when subjected to high-intensity ground motions, a 1/20-scale bridge model from a typical medium-span concrete cable-stayed bridge was designed, constructed, and tested on shake tables. Yielding steel damper (YSD) and viscous fluid damper (VFD) were used as passive energy dissipation devices in the transverse and longitudinal directions, respectively. The bridge models were then excited by two ground motions with different spectral characteristics in transverse and longitudinal directions accordingly, including the Chi-Chi earthquake wave and a site-specific artificial wave. The seismic responses of the bridge models with and without the passive devices were analyzed and compared. Both numerical and test results show that the YSD applied in the transverse direction could reduce the seismic responses of the towers effectively, and the VFD applied in the longitudinal direction could reduce the displacement of the deck effectively while simultaneously limiting the seismic responses of the towers. Therefore, it is suggested that the proposed energy dissipation system, consisting of YSD transversely and VFD longitudinally along with the sliding bearing, is applied in the cable-stayed bridges for better overall seismic performance compared to the traditional isolation system that provides efficiency only longitudinally.