Span Bridges Research Articles

Research Progress on Fire Resistance of Steel-concrete Composite Structures

The 1930s was an important period of development in the design theory of bridge technology in Europe and the United States. Among them was the invention of welding technology, which created more favorable conditions for the development of combined structures, i.e., the connection between reinforced concrete slabs and steel girders could be welded instead of the initial connection method. In China, for more than thirty years, on the one hand, large span bridges have been able to develop rapidly and set new world records, driven by the huge technical demand seeking span breakthroughs. On the other hand, concrete bridges dominate the large number of small span bridges. In short, in China, steel-concrete (SC) structures have also developed accordingly. This paper first introduces the steel-concrete combination structure, and then analyzes the steel-ability concretes to withstand fire from both theoretical and experimental perspectives. Valid data are provided by graphs and equation analysis. Finally, a method that can measure the fire resistance of SC composite structures in fire is obtained.

Study on the History and Present Situation of Cable-stayed Bridge Structures in China

With the improvement of force mode, the development of material characteristics and technologies, the Cable-stayed Bridge structures are used more and more widely. In 1975, Yunyang Bridge, the first experimental Cable-stayed Bridge of China, was completed. In the following decades, China has greatly increased the span of bridges and the height of towers. During construction, the materials used to build bridge structures are more diverse and safer. In 2017, the Hong Kong-Zhuhai-Macao Bridge, representing the most advanced bridge-building technology in China at the time, was born. In this paper, the history of ancient Cable-stayed Bridges is firstly introduced. Then, several Cable-stayed Bridges which have great influence are researched, respectively. Finally, this paper compares Yunyang Bridge and Hong Kong-Zhuhai-Macao Bridge in-depth from three aspects: comparison of the construction scales, comparison of the construction materials and comparison of the cable technologies. The results show the progress of bridge industry in the past 42 years of China.

Towards predicting dynamic reliability of bridge spans

In conditions of increasing impact of temporary live load, a premature wear of bridge superstructures occurs, operational strength and durability decrease. The paper discusses the dynamic reliability of the load-bearing elements of superstructures within the frame of ensuring the structure safety during operation, with regard to defects and overloads. Reliability is considered within the framework of random events and processes based on the possible superstructure exit beyond its serviceability based on the statistical dynamic properties. The par ametric and structural reliability is considered. Based on the mathematical statistics and random numbers theories, the dynamic reliability theory is characterized by the quality deployed in time. The effect of load variation for a long time is considered. The possibility is predicted for changing resources and structure failure. The dynamic reliability conditions are approximated based on the Gauss and Weibull distribution curves. Mathematical expressions are given to the structure indestructibility. The superstructure failure is considered with respect to possible overload using the principle of accidental release.

Investigation of a dynamic chord method and its application on track irregularity evaluation and track maintenance

Track irregularity causes dynamic train-track interactions and accelerates the degradation of their components. In this paper, we proposed a dynamic chord method based on dynamic measurements that can be directly used for maintenance planning. Based on the extensive investigations, we found that the results from the dynamic chord method are comparable to the static chord measurement results with appropriate cut-off wavelength and chord length. Specifically, the maximum chord lengths to apply on the dynamic measurements with cut-off wavelengths of 42 m, 70 m, and 120 m are 20 m, 30 m, and 40 m respectively. Track settlement can be identified based on the difference analysis between the static and dynamic chord results when the chord length is larger than the maximum chord length. Further, we proposed a method to evaluate track stiffness based on the peak differences between static and dynamic measurements. A threshold of 2 mm is used to determine whether there are track stiffness anomalies. The validity of the method is shown with experimental tests and field validations. Finally, a more direct method to guide track adjustment based on dynamic measurement is proposed. The application of this method on track adjustment shows that the amplitude of dynamic longitudinal level and the standard deviation reduces by 42 % and 51 % respectively. Periodic longitudinal level at the wavelength of 32 m, due to the bridge span, also sees significant improvements.

A Review on the Combined Effects of Seismic and Vehicular Vibrations on Long Span Bridges

Long span bridges are massive structures which are subjected to combined loadings. The increase in span length of long span bridges will result in decrease of their natural frequencies that renders them very susceptible to the actions of various combined dynamic forces. Dynamic loads such as vehicular movement and seismic excitations have greater potential in causing increased vibrations in long span bridges. The vehicular loading is highly variable and depends on type of vehicle, number of lane, behaviour of vehicle such as lane changing, traffic congestions and so on. Further, seismic excitations are characterized by its spatial variability parameters such as incoherence effect, wave passage effect and site response effects. From detailed review, it was found that fewer researches have been carried out in the field of dynamic effects of long span arch bridges and thus the study aims in determining the combined effects of seismic and vehicular vibrations on long span arch bridges.

Seismic (effect on) time history analysis for cable-stayed suspension hybrid bridge considering different geometrical configuration for far field earthquakes

To increase the maximum span of cable-stayed bridges, Uwe Starossek has developed a modified statical system. The basic idea of this new concept is the use of pairs of inclined pylon legs that spread out longitudinally from the foundation base or from the girder level. Spread-pylon cable-stayed bridge has distinct advantage like reduction of sag of cables and oscillation of cable during earthquake over traditional cable-stayed bridges. Spread-pylon also improves seismic performance of deck during strong ground motion. Here in this paper dynamic behaviour of cable stayed suspension Hybrid bridge with different structural configuration with seismic loading was studied. The primary aim , here, is to present response to Seismic effect on Cable stayed Bridges with different cable system taking under consideration SSI.It is evidently clear that Soil Foundation Structure Interaction relies greatly on various factors such as soil and its properties, manner and type of structure and/or its foundation.. In this paper , the emphasis is on the simplified model and foundation on piles. For the modelling author has used SAP2000 software. The study includes the response of the bridge modelled towards variation in the cable system under consideration of SSI. A bridge similar to that of Bridge at Ling Ding Strait China is taken as a reference and 6 models are created with variation in cable system ( ranging from original cable stayed bridge to suspension type, composite bridge and cable stayed suspension hybrid bridge). Soil modeling is done using the spring and dashpots ( Kelvin element) for simulation of SSI effects.The results observed that effects of SSI has a substantial impact on selection of system of cables and the pylon leg inclination for any Cable- Stayed- Suspension Hybrid Bridge(CSSHB)

Theoretical Analysis of Ultimate Main Span Length for Arch Bridge

The advancement of construction techniques and high-performance sustainable materials enables the increase of span length for arch bridge. It is of great importance to study the theoretical ultimate span length of arch bridge. Based on the parabolic and catenary arch axes, the analytical solutions of ultimate span length of arch bridge are solved using theoretical derivation accounting for the strength, in-plane stability and out-plane stability conditions, respectively. Then, the use of high-performance concrete, reactive powder concrete and high-strength steel is considered to study the relationship between theoretical ultimate span length and rise-span ratio as well as material strength for concrete and steel arch bridges. The results show that the theoretical ultimate span length derived by catenary arch axis is smaller by about 2–6% than that obtained by parabolic arch axis, but the difference is insignificant. When the rise-span ratio is 1/5, the theoretical ultimate span length for concrete arch bridge using R200 reactive powder concrete can reach 2000 m (2161 m for catenary arch axis and 2099 m for parabolic arch axis) while the main span of steel arch bridge using Q690 high-strength steel can be longer than 2500 m (2948 m for catenary arch axis and 2865 m for parabolic arch axis).

Local and post-local buckling behavior of welded square high-strength steel tubes with concrete-infilled restraints

Concrete-filled high-strength steel tubular members gain increasing popularity as the building height and bridge span increase. The slender sections and higher stress levels, however, make the high-strength steel plates more susceptible to local buckling. This paper reports an experimental and numerical investigation on local and post-local buckling behavior of welded square high-strength steel tubes with concrete-infilled restraints. Sixteen high-strength steel tubes with nominal yield strengths of 460, 500, and 550 MPa with concrete-infilled restraints were tested. The experimental results reveal that the post-buckling reserve strength of steel tubes with slender sections increases with the increase in plate slenderness regardless of steel grade. A total of 168 numerical models were subsequently established using the verified finite element method. Based on the finite element analysis results, the slenderness limits and effective width formula were proposed for both high-strength and normal-strength steel tubes with concrete-infilled restraints. Available test data of steel-only-loaded concrete-filled steel tubular specimens constitutes an experimental database to evaluate the reliability of the existing slenderness limits and effective width formulas. The comparison result shows that GB 50936, AS/NZS 2327, and AISC 360-16 overestimate the slenderness limits, while Song et al. underestimate the slenderness limit excessively. The proposed slenderness limit (λpl = 0.500) is more consistent with the experimental results with a reasonable conservative level. The mean ratio of predicted post-buckling strengths by the proposed effective width formula to experimental results is 0.94, with a standard deviation of 0.073. The proposed slenderness limit and effective width formula provide a more accurate prediction and, therefore, are recommended in design.

An analytical method for assessing the live load deformation of a suspension bridge with an improved central buckle

Suspension bridges lack favorable supports for global vertical stiffness, making it challenging to meet the road safety requirement due to the excessive deflection of stiffening girder when developing towards larger spans. It hinders the development of the ultimate span of suspension bridges and reduces the utilization rate of materials. This paper proposes an improved central buckle (ICB) to increase the global vertical stiffness of suspension bridges. Without changing the constraints of the stiffening girder, the central buckle and horizontal cable are placed at the mid-span and bottom of the stiffening girder, respectively, which combination is referred to as ICB. It restrains the horizontal displacement of the main cable and reduces the maximum deflection of the suspension bridge due to the asymmetric live loads. The analytical expressions of the deflection and girder-end rotation of the suspension bridge with the ICB are derived based on the deflection theory. The expression of the variable equivalent horizontal spring stiffness of the ICB is proposed and verified by a finite element model of the suspension bridge. These results prove that the ICB can effectively restrain the horizontal displacement of the main cable caused by the asymmetric live load and significantly reduce the vertical deflection of the stiffening girder. The performed parametric analysis clarified the mechanism of increasing the vertical stiffness of the suspension bridge based on the ICB force transmission path, providing a new design scheme for improving the global vertical stiffness of the suspension bridge and expanding its upper span limit.

Single keyed joints behaviour and capacity formulation under direct shear using non-linear finite-element analysis

Short precast box girders offer economical, safe, and serviceable structures that can be rapidly constructed. The joints between segments along the bridge span are considered locations of discontinuity that control its strength and behavior. This research aims to study the effect of lateral confinement and concrete compressive strength on the behavior of the dry single-keyed joint in precast segmental bridges under direct static shear caused by vertical load through non-linear FEA simulation. A parametric study was carried out by establishing and validating a Finite Element Analysis model in ABAQUS based on the Concrete Damage Plasticity model. The keyed joints with various combinations of compressive concrete strengths ranging from 15 MPa to 50 MPa at 5 MPa increments and confinement pressure ranging from 0 to 6 MPa at 1 MPa increments were tested. The results of the numerical analysis of the 56 combinations were produced in the form of ultimate load-carrying capacity, load–displacement curves, crack evolution, and concrete crushing evolution in the keyed zone, leading to a better understanding of the behavior and failure sequence of the mentioned joints. The increase in lateral confinement led to increasing the ultimate shear strength of the keyed dry joint as well as increasing its initial stiffness and vertical displacement at the peak load consequently. However, this enhancement ceases with lower-grade concrete strength at higher confinement levels. A new shear capacity formula was proposed and evaluated against the numerical analysis results, selected experimental work, and the current design formulas, including AASHTO. The proposed formula was shown to agree very well with mentioned experimental and numerical work.

Effects of Vertical Ground Motion on Pedestrian-Induced Vibrations of Footbridges: Numerical Analysis and Machine Learning-Based Prediction

Current codes and guidelines for the dynamic design of footbridges often only specify the pedestrian-induced excitations. However, earthquakes may occur during the passing stage of pedestrians in earthquake-prone regions. In addition, modern footbridges tend to be slender and are sensitive to vertical ground motions. Therefore, we investigate the effects of vertical ground motion on pedestrian-induced vibrations of footbridges. A total of 138 footbridges with different materials, dimensions, and structural types are considered as the target structures. The classical social force model combined with the pedestrian-induced load is used to simulate crowd loads for the scenarios with six typical pedestrian densities. Furthermore, 59 vertical ground motions with four seismic intensities are taken as the seismic inputs. An amplification factor is introduced to quantify the amplification effects of vertical ground motion on human-induced vibrations of footbridges. Four machine learning (ML) algorithms are used to predict the amplification factor. The feature importance indicates that the scaled peak ground acceleration, the pedestrian density, and the bridge span are the three most important parameters influencing the amplification factor. Finally, the vibration serviceability of the footbridge subjected to both crowd load and vertical ground motion is assessed.

A method for calculating strand tension in the anchor span of a suspension bridge considering the rotation of a splay saddle

This paper reports a method for strand tension in anchor spans considering rotation. A kind of co-moved coordinate system, a saddle local coordinate system, was set up. This system implemented the rotation of the splay saddle through the rotation of the coordinate system, and all calculations proceeded in this coordinate system. Considering the rotation of the anchoring surface by the rotation of the local coordinate system of the anchoring surface, the anchorage point coordinates of strands were transformed to the local saddle coordinate system. There was a two-layer iteration adopted in the calculation. In the inner iteration, the cable force at the end of the vertical bend was taken as the variable, and the ordinate of the anchorage point was taken as the target value. In the outer iteration, the vertical tangential angle at the end of the vertical bend was taken as the variable, and the ordinate of the anchorage point was taken as the target value. The method carried out the rotation of the splay saddle and anchor surface and was simple, convenient and without approximation. The effect of rotation was considered precisely; it showed stability during the process of two-layer iteration, powerful adaptation and higher efficiency and had been successfully applied in the construction control of the Wufengshan Yangtze River Bridge, the world's first kilometer-level combined highway and railway suspension bridge.

Fatigue behaviour of joint-free bridges with steel and GFRP-reinforced ECC link slabs

Engineered Cementitious Composite (ECC) link slabs provide a feasible alternative to leaking expansion joints for improving long-term durability of slab-on-girder bridges. The use of Glass Fiber Reinforced Polymer (GFRP) rebars have become increasingly common for inducing superior chemical resistance in bridge decks in salt-prone locations. Existing literature lacks experimental research on effects of fatigue load on joint-free bridges with ECC link slabs reinforced with GFRP bars. This paper presents results of experimental testing of joint-free bridges with GFRP or steel-reinforced ECC link slabs subjected to static and fatigue (up to 1 million cycles at 4 Hz) loadings. Comparative performance between GFRP and steel-reinforced ECC link slab bridges is described based on load–deflection or moment-rotation behaviour, strain characteristics and crack development in pre-fatigue, fatigue and post-fatigue stages. After 1 million fatigue cycles, the GFRP-reinforced ECC link slab exhibited smaller crack widths and higher deformation capacity while its incorporation provided superior ductility and deformation capability of the full bridge. A finite element (FE) model was also developed using experimental results to simulate load–deflection behaviour of composite deck-steel girder joint-free bridge with ECC link slab subjected to fatigue loading. Parametric FE study showed that increasing mean stress level caused increased composite deck-steel girder deflection while link slab deflection was limited by bridge span deformation.

Application of 3D cellular automata-based analysis to chloride diffusion process in concrete bridges

Chloride-induced corrosion is one of the main reasons for degrading the serviceability and reliability of concrete bridge structures in severe environments. Consequently, a more accurate simulation of the chloride diffusion process is essential for a durable design. This paper performs a three-dimensional (3D) cellular automata (CA) model that accurately simulates chloride diffusion in concrete. The model's accuracy was investigated by comparing the results with Fick's second law (FSL), 2D-CA model, and experimental data. The 3D-CA model is improved and applied to simulate the chloride diffusion in a concrete bridge, considering the effect of multiple factors such as relative environmental humidity, variations in temperature, stresses, water-cement ratio (w/c), concrete degradation, corrosion propagation, cracking, and time. The 3D-CA model algorithms were developed using Python to accomplish this goal. The life span of the concrete bridge was assessed based on critical regions of the corrosion beginning and concrete cracking time. The 3D-CA model provides a more suitable approach to simulating chloride diffusion and predicting the initial corrosion time of reinforcement bars. It can also provide a basis for establishing a maintenance strategy with low-cost solutions for evaluating risk areas and constructing durable projects.

Dynamic Reliability Assessment of Heavy Vehicle Crossing a Prototype Bridge Deck by Using Simulation Technology and Health Monitoring Data

Overloads of vehicle may cause damage to bridge structures, and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges. In this report, using a large amount of monitored data collected from the structural health monitoring system (SHMS) in service of the prototype bridge, of which the bridge type is large-span continuous rigid frame bridge, and adopting FEM simulation technique, we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation. In the first place, by using the health monitored strain data, of which the selected monitored data time range is before the opening of traffic, the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained; then, with FEM technology, the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed. At last, assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact, the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge. Based on a large number of field measured data, the dynamic reliability value calculated by our proposed methodology is more accurate. The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.

Modeling the Quantitative Assessment of the Condition of Bridge Components Made of Reinforced Concrete Using ANN

Bridges in Ukraine are one of the most important components of the infrastructure, requiring attention from government agencies and constant funding. The object of the study was the methodology for quantifying the condition of bridge components. The Artificial Neural Network-based (ANN) tool was developed to quantify the technical condition of bridge components. The literature analysis showed that in most cases the datasets were obtained during the inspection of bridges to solve the problems of assessing the current technical condition. The lack of such a database prompted the creation of a dataset on the basis of the Classification Tables of the Operating Conditions of the Bridge Components (CT). Based on CTs, five datasets were formed to assess the condition of the bridge components: bridge span, bridge deck, pier caps beam, piers and abutments, approaches. The next step of this study was creating, training, validating and testing ANN models. The network with ADAM loss function and softmax activation showed the best results. The optimal values of MAPE and R2 were achieved at the 100th epoch with 64 neurons in the hidden layer and were equal to 0.1% and 0.99998, respectively. The practical application of the ANN models was carried out on the most common type of bridge in Ukraine, namely, a road beam bridge of small length, made of precast concrete. The novelty of this study consists of the development of a tool based on the use of ANN model, and the proposal to modify the methodology for quantifying the condition of bridge components. This will allow minimizing the uncertainties associated with the subjective judgments of experts, as well as increasing the accuracy of the assessment.

Finite Element Model Updating of RC Bridge Structure with Static Load Testing: A Case Study of Vietnamese ThiThac Bridge in Coastal and Marine Environment.

Diagnostic load testing refers to the use of the measured historical responses of the structure in the field data to better understand its dynamic and static structural behaviours. It is important and necessary to predict the health state, load capacity, and aging of the structure by updating the finite element (FE) model, which can give useful information to aid the design of retrofits and the maintenance of the existing bridge in the future. The paper presents an update of the full-scale FE model for the reinforced concrete (RC) bridge structure over the seawater river based on the experimental strains under the static load testing in which the representative FE model of the actual structure is determined from the optimisation procedures. The optimisation variables are applied, including the cross-sectional properties and concrete material calibrated through the genetic algorithm (GA) optimisation in the MATLAB software, which interfaces with the FE modelling in the scripting of the SOFISTIK TEDDY software automatically. The bending moments at the mid-span of the RC girders are determined in the FE modelling to compute stresses, which are compared with the measured stresses through optimisation scenarios with a percentage error of the objective function less than 10%. The measured data of concrete strains are recorded from reusable strain transducers installed on the mid-span girders for every bridge span, which are used to calibrate the bridge model in static load testing. The novelty of the solution is to implement innovative techniques using field data as an improved approach for calibrating automatically the analytical FE model parameters of all RC spans of the bridge until its static behaviours are very similar to those of the actual bridge. The final updated FE modelling is used to apply truck load configurations according to bridge design standards such as the AASHTO specifications, which can predict the load limits of the existing bridge structure more accurately and reliably. These proposed approaches can be applied to large bridges as well as complex structures with supporting FE analysis software and data processing software.

Eccentrically loaded concrete-filled steel tubes made with high strength materials

High-strength welded steel sections filled with high-strength concrete, so called high-strength concrete filled steel tubes (HSCFSTs), are widely used in multi-story buildings and large span bridges to achieve superior structural performance with optimized cost. Many experimental and numerical investigations have been conducted on the behaviour of small and large scale HSCSFTs under centric axial compression. However, very few studies have investigated the response of large scale HSCFSTs under eccentric loads. This paper presents an experimental investigation conducted on five square HSCFSTs that are 2.7 m height under eccentric axial compression. The effects of loading eccentricity and depth-to-thickness ratios on the behaviour of HSCFST columns were investigated. The experimental results reveal that the failure mode of HSCFSTs was governed by local buckling of the steel tube in all cases. A finite element model was also developed in ABAQUS and was validated against the test results. Sensitivity and parametric studies that investigate the effect of various parameters of the concrete damaged plasticity model, imperfections, concrete and steel strengths, load eccentricity and plate slenderness are also presented.

Soil-structure interaction of integral abutments

Integral abutment bridges (IABs) are pioneering structures that offer certain advantages over conventional bridges. The main difference is the ability of IABs to eliminate the necessity of utilizing bearings and expansion joints. This results in more economical construction and enhanced structural performance. However, the intricate soil-structure interactions of IABs under the influence of seasonal changes are not yet fully understood. This paper aims to improve the understanding of these innovative structures by utilizing comprehensive numerical models to investigate their geostructural performance under various conditions. The case study selected for this research was the Middlesex bridge in Vermont, USA. A full-scale monitoring program at this bridge measured and recorded the bridge acting pressures, deformations, and internal forces, making it possible to gain insight into the thermal response of such structures. For the numerical research, a comprehensive two-dimensional numerical model, developed by using the PLAXIS software, was verified against the available field measurements. Subsequently, parametric studies were conducted to investigate earth pressure and pile bending moment variations influenced by different model conditions. Key model parameters were varied, including the constitutive soil model, thermal loading, backfill stiffness, pile size and orientation, and span length. It was found that utilizing a linear constitutive soil model could lead to significant inaccuracies in the results. Increasing the backfill stiffness was seen to increase passive earth pressures and decrease pile bending moments. With smaller pile sections, oriented for weak-axis bending, pile bending moments decreased substantially and lateral earth pressures increased. Because dead load magnitudes were closely linked to span lengths, pile bending moments and backfill pressures increased when fewer and longer bridge spans were used.

Influence Analysis of Lubricant Recesses on the Working Capacity of the Bridge Span Spherical Bearing

The load on transport and logistics systems is increasing every year. This is due to car park growth around the world. Thus, increasing bridge structure durability is an urgent task for bridge-building companies. This study analyses the contact deformation of spherical bearing elements through an anti-friction polymer layer with different geometrical configurations of recesses for the lubricant, i.e., annular grooves and spherical holes. The material of the anti-friction layer (a modified polytetrafluoroethylene (PTFE)) is modelled within the framework of the deformation theory of plasticity. The procedure of automating the numerical model construction depends on the input parameters, including the thickness of the layer, the basic geometrical parameters of the recesses for the lubricant, and the distance between the rows of recesses, etc. The influence of the arrangement of filling sliding anti-friction layers on recesses for lubricants in the form of spherical holes on the contact deformation behaviour of bridge bearings has been considered. The reduction of lubricant volume in the sliding anti-friction layer with the geometry of recesses in the form of spherical holes ranges from 26 to 48.4%, depending on the filling scheme, has been found. In this case, structures with lubrication recesses in the form of spherical holes have several advantages, including a more uniform distribution of contact parameters in the interface areas of the steel plates with the anti-friction layer, reduction of the maximum level of the plastic deformation intensity, displacements along the normal relative to the free end of the sliding layer, and the settlement of the bearing.