BEHAVIOR OF PRE-STRESSED INTERSECTING CABLE STEEL BRIDGE

The bridges supported by high strength steel cables are the substitute to attain very lengthy bridge. Usually, cable supported bridge systems known as cable-stayed bridge and suspension bridge are used to achieve longer span bridge. In the cable-stayed bridge system better stiffness is achieved due to inclined stayed cables. In suspension bridge systems longer central span is achieved by provision of stiffened deck. The novelty in structural form, material technology and analysis methods offer further long span cable supported structural system. By combining the cable-stayed bridge and suspension bridge in a bridge, an innovative form of hybrid cable-stayed suspension bridge may offer enhanced behaviour. Mathematical model for innovative form of hybrid cable-stayed suspension bridge is addressed. The geometrical parameters play important role in structural behaviour of the cable-stayed suspension hybrid bridge. Nonlinear static analysis and modal analysis are carried out using SAP2000 software. The effects of intermediate side span support on the static and dynamic behaviour of cable-stayed suspension hybrid bridge are presented in the form of time period of bridge in lateral, longitudinal, vertical directions and pylon bending.

Recent developments in the social sphere also cause an increase in transportation activities. Increased transport activities lead to the construction of new roads and bridges. Different bridge construction systems are available to overcome large span obstacles. Cable-stayed bridges are more advantageous construction systems than other bridge type building carrier systems in overcoming large spans through suspension cables. Therefore, it is also widely preferred by designers. The biggest factor in the development of cable-stayed bridges is undoubtedly steel cables. Cable-stayed bridges are bridge structures that become lighter with the increase of the span, which has a more expanded flexibility, and that includes a cable system with the effect of nonlinear factors. Costs of cable-stayed bridges vary according to different spans. The span as well as the deck material used in the bridge system have a great effect on the cost. In cable-stayed bridge systems, decks are constructed of reinforced concrete and steel. The costs of cable-stayed bridges are widely discussed around the world; therefore, the effect of the span and deck material on the cost of cable-stayed bridges is being investigated. The main bearing elements of such bridges are cables, decks, and towers, and among these elements, the tower bridge carries all the weight of the bridge, even other external loads such as vehicle, wind, etc. In this study, the three-dimensional model of the cable, deck and tower elements that make up the cable-stayed bridge system was created and analysed using the CSI Bridge Program. The AASHTO LRFD Standards, which are widely used in the analysis of bridge systems with the CSI Bridge program and the design of bridge systems in the world, were used. In the study, the analysis and designs of cable-stayed bridges with reinforced concrete and steel deck at 250, 500, 750, 1000, 1500, 2000 meters span were carried out. The amount of materials and costs used in the analysis and design of the cable-stayed bridge systems were obtained and the results were interpreted.

As the span of conventional cable-stayed bridges reaches 1,200 m or longer, accumulated horizontal force components of the stay cables cause huge axial pressure in the girder, leading to sharp increases of girder dimension and weight, which makes it difficult to compete with suspension bridges in terms of economic consideration. In this paper, a new type of cable-stayed bridge is proposed, namely the partial ground-anchored cable-stayed bridge with crossing stay cables. In this new cable-stayed bridge system, long stay cables cross with each other in the midspan zone of the main span while the other ends of the long cables are anchored to the ground in the side spans. By this design, the long cables result in no additional horizontal pressure to the main girder, and the ratio of pylon height to span length can be reduced. A comparative analysis of this new bridge system with a conventional self-anchored cable-stayed bridge with a main span of 1,408 m is carried out. Results show that by using the new bridge system, the horizontal pressure in the main girder can be reduced by 29.6%, and the total cost can be reduced by 11.8%. Furthermore, the size of ground anchors for this new bridge system is only about 30% of that of a suspension bridge with the same span length. Finally, a cantilever construction method for the new bridge system is introduced as well.

One of the main issues in the design of cable-stayed steel bridges is the way of stabilization of its initial form under symmetrical and asymmetrical loads. The main mass of the load-bearing structures is concentrated in the stiffening girder. The article presents a hybrid pre-stressed cable-stayed steel bridge structural system. The behavior of this new system of the intersecting stay cables and the flexible string under the effect of the permanent and the temporary loads are the issues under analysis. The efficiency of this proposed cable-stayed steel bridge structure system was determined based of the performed numeric experiment.

Compared to other structural systems, cable-stayed bridges are marked by their exceptional architectural appeal. However, these bridges have several disadvantages – their deformability under asymmetrical or local loads the relatively significant mass of stiffening girder and the pylons. A successful way of stabilizing the bridge’s initial form could be using additional stay cables and additional pylons. The article discusses the calculation method of an innovative cable-stayed steel bridge system consisting of intersecting cables and additional intermediate pylons. The system’s behavior is analyzed under symmetrical and asymmetrical loading. The calculation method results are compared to the numerical analysis using the FEM software.

PurposeAs an important load-bearing component of cable-stayed bridge, the cable-stayed cable is an important load-bearing link for the bridge superstructure and the load transferred directly to the bridge tower. In order to better manage the risk of the cable system in the construction process, the purpose of this paper is to study a new method of dynamic risk analysis of the cable system of the suspended multi-tower cable-stayed bridge based on the Bayesian network.Design/methodology/approachFirst of all, this paper focuses on the whole process of the construction of the cable system, analyzes the construction characteristics of each process, identifies the safety risk factors in the construction process of the cable system, and determines the causal relationship between the risk factors. Secondly, the prior probability distribution of risk factors is determined by the expert investigation method, and the risk matrix method is used to evaluate the safety risk of cable failure quantitatively. The function expression of risk matrix is established by combining the probability of risk event occurrence and loss level. After that, the topology structure of Bayesian network is established, risk factors and probability parameters are incorporated into the network and then the Bayesian principle is applied to update the posterior probability of risk events according to the new information in the construction process. Finally, the construction reliability evaluation of PAIRA bridge main bridge cable system in Bangladesh is taken as an example to verify the effectiveness and accuracy of the new method.FindingsThe feasibility of using Bayesian network to dynamically assess the safety risk of PAIRA bridge in Bangladesh is verified by the construction reliability evaluation of the main bridge cable system. The research results show that the probability of the accident resulting from the insufficient safety of the cable components of the main bridge of PAIRA bridge is 0.02, which belongs to a very small range. According to the analysis of the risk grade matrix, the risk grade is Ⅱ, which belongs to the acceptable risk range. In addition, according to the reverse reasoning of the Bayesian model, when the serious failure of the cable system is certain to occur, the node with the greatest impact is B3 (cable break) and its probability of occurrence is 82%, that is, cable break is an important reason for the serious failure of the cable system. The factor that has the greatest influence on B3 node is C6 (cable quality), and its probability is 34%, that is, cable quality is not satisfied is the main reason for cable fracture. In the same way, it can be obtained that the D9 (steel wire fracture inside the cable) event of the next level is the biggest incentive of C6 event, its occurrence probability is 32% and E7 (steel strand strength is not up to standard) event is the biggest incentive of D9 event, its occurrence probability is 13%. At the same time, the sensitivity analysis also confirmed that B3, C6, D9 and E7 risk factors were the main causes of risk occurrence.Originality/valueThis paper proposes a Bayesian network-based construction reliability assessment method for cable-stayed bridge cable system. The core purpose of this method is to achieve comprehensive and accurate management and control of the risks in the construction process of the cable system, so as to improve the service life of the cable while strengthening the overall reliability of the structure. Compared with the existing evaluation methods, the proposed method has higher reliability and accuracy. This method can effectively assess the risk of the cable system in the construction process, and is innovative in the field of risk assessment of the cable system of cable-stayed bridge construction, enriching the scientific research achievements in this field, and providing strong support for the construction risk control of the cable system of cable-stayed bridge.

According to the seismic performance of cable-stayed bridge with a project example, using finite element analysis method, establishing the space beam element and link element calculation model, the dynamic characteristic and the seismic response of the cable-stayed bridge with selected three earthquake waves were calculated, the results were compared with the of the response spectrum method.The results show that:the semi-floating system of cable-stayed bridge is great flexibility, the vibration cycle is generally longer; the results by using the response spectrum method are smaller; the cable-stayed bridge should be calculated in accordance with the specific circumstances of the project with multiple seismic waves.

Larger displacement and inter-force response of the structure will be produced when self-anchored cable-stayed suspension bridge in longitudinal earthquake. Engineering practice proved that the viscous damper has obviously damping effect for structure. For the vibration reduction system of self-anchored cable-stayed suspension bridge, whose main tower is set viscous damper. This essay does the nonlinear time history analysis under the longitudinal earthquake about the vibration reduction system that considering the LRB putted in different location. Compared with the damping system that only set viscous damper, analysis results show that inter-force and displacement of control section and control node are reduced greatly in hybrid vibration control.

As a high-order statically indeterminate structure, long-span cable-stayed bridges usually consist of many components such as main towers, stay cables, main beams, auxiliary piers, and connecting piers. Due to the mutual influence between components under earthquakes, the accurate simulations of the correlations among component seismic responses are critical to the vulnerability assessment of the overall system of a cable-stayed bridge. Pair Copula can simulate the correlation between two components. It is theoretically feasible to use Pair Copula in a hierarchically iterated way to simulate the whole system of a cable-stayed bridge. Therefore, a new seismic vulnerability assessment method of a cable-stayed bridge system is proposed based on Pair Copula iterative model. Based on structural uncertainty parameters and ground motion uncertainty, Latin hypercube sampling technique is used to establish bridge-ground motion probabilistic seismic response analysis samples. The correlations among the seismic responses of components are quantified through nonlinear dynamic time history and correlation analysis. Pair Copula models are fitted with maximum likelihood estimation and optimized based on AIC and BIC criteria. Through the hierarchical iteration of Pair Copulas, the overall model of a cable-stayed bridge is established, and its seismic vulnerability is evaluated. The engineering example shows that the correlation among multiple components can be accurately simulated based on the technology of hierarchical iteration of Pair Copula. With the assumption that the seismic responses of components are completely unrelated, the seismic vulnerability of a whole cable-stayed bridge system will be significantly overestimated.

The structural system with better seismic performance is one of the key to the seismic design of cable-stayed bridges. The research shows that the internal force response of floating system is small and the displacement response is large, and the seismic response of the hinged system is the opposite. However, the tower bottom moment of the fix hinged cable-bridge could be less than it of the floating system actually, because the inertia force of the girder in the hinge system would be transmitted to the tower through the connection of tower and girder. In the light of these characteristics, a new low-gravity cable-stayed bridge seismic structure system, the safe-belt constraint system, is proposed in this paper, and the seismic response characteristics are studied by ANSYS. In addition, the effect of safe-belt parameters on the vibration reduction effect of the belt system cable-stayed bridge is analyzed.

As important load bearing members of cable-stayed bridges, stay cables may experience corrosion, fatigue, and accidental or intentional actions that may lead to possible breakage failure. The current bridge design guidelines require that a cable-stayed bridge be designed against single-cable breakage. A holistic reliability assessment framework is developed for a long-span cable-stayed bridge and traffic system subjected to breakage of stay cables considering service load conditions from both traffic and wind. In addition to the bridge structural ultimate limit state, a new bridge serviceability limit state is also introduced by focusing on the overall traffic safety performance of all vehicles of the traffic flow on the bridge following cable breakage incidents. Random variables are defined by considering uncertainties related to structural material properties, sectional properties, traffic, wind condition, and cable breakage parameters. The Latin hypercube sampling technique is adopted to sample the random variables and establish the simulation models by considering various uncertainties of parameters. Nonlinear dynamic analysis is conducted in each experiment to simulate the breakage of stay cables, during which various sources of nonlinearities and dynamic coupling effects from traffic and wind are incorporated. Fragility analyses of the bridge subjected to cable breakage events in terms of the ultimate limit state and the serviceability limit state are finally conducted.

Cable-stayed bridges can be a very effective means of bridging large distances in both seismic and non-seismic regions. Their design, analysis, and construction can be very challenging, and fortunately there is a considerable amount of literature that can assist engineers with both the analysis and detailed design of cable-stayed bridges. It is less common, however, to find simple recommendations for the conceptual design of cable-stayed bridges, in particular for seismic loading. As such, this article reviews and discusses some of the important conceptual design considerations for cable-stayed bridges, first for gravity loads and then for seismic excitation. The advantages and disadvantages of different cable-stayed bridge solutions are highlighted, with review of deck sections, tower configurations in both the longitudinal and transverse direction, deck-to-pier connections, and cable arrangements, amongst other things. Reference is made to a number of real cable-stayed bridge solutions. After reviewing the important conceptual design considerations for cable-stayed bridges, a simple preliminary sizing procedure is proposed. The preliminary sizing procedure is intended to offer designers a quick but rational means of identifying reasonable member sizes for cable-stayed bridges that should then be verified through advanced analyses in the developed and detailed design stages of the project. A case study application of the preliminary sizing procedure is made for a three-tower cable-stayed bridge in Ecuador, and by comparing preliminary and final design member sizes it is concluded that the preliminary sizing procedure may be a useful tool for design.

In this study, wireless structural health monitoring (SHM) system of cable-stayed bridge is developed using Imote2- platformed smart sensors. In order to achieve the objective, the following approaches are proposed. Firstly, vibrationand impedance-based SHM methods suitable for the pylon-cable-deck system in cable-stayed bridge are briefly described. Secondly, the multi-scale vibration-impedance sensor node on Imote2-platform is presented on the design of hardware components and embedded software for vibration- and impedance-based SHM. In this approach, a solarpowered energy harvesting is implemented for autonomous operation of the smart sensor node. Finally, the feasibility and practicality of the multi-scale sensor system is experimentally evaluated on a real cable-stayed bridge, Hwamyung Bridge in Korea. Successful level of wireless communication and solar-power supply for smart sensor nodes are verified. Also, vibration and impedance responses measured from the target bridge which experiences various weather conditions are examined for the robust long-term monitoring capability of the smart sensor system.

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

The dynamic analysis of train-bridge systems has been a popular research topic for a long time; however, studies on cable-stayed bridges subject to train and seismic loads remain limited. Cable-stayed bridges can experience large vibrations under external periodical loads due to the high flexibility caused by their long decks and cables. Previous approaches to modeling the cables have limitations in accuracy, principle, or calculation efficiency, making them unsuitable for dynamic analysis with numerous time steps for long-span bridges with many cables. Furthermore, track irregularities and earthquakes bring additional excitations to the train-bridge system and threaten its structural and running safety. Thus, an accurate and fast approach to modeling and analyzing cable-stayed bridges under train loads and other excitations is needed. In this study, an improved parabolic cable element is included for dynamic analysis. This cable element facilitates a faster calculation while maintaining an accuracy similar to that of a catenary cable element. The coupled equation-of-motion of the train and cable-stayed bridge system is derived and solved via the time integration method. The effects of railway track quality and seismic load are investigated through the dynamic responses of train-bridge systems by considering various classes of tracks and levels of seismic intensities, respectively. The impact factors of the vertical displacement of the deck and the tensions in cables are used to represent the behaviors of the bridge, while the maximum accelerations of vehicle bodies are used to represent the behaviors of the train. Track irregularities and seismic load significantly increase the responses of the bridge and train. With increased train speed, the negative effects of poor quality track on the responses of the train-bridge system increased; however, with increased seismic loads the effects were found to decrease.