Large-span Bridge Research Articles

Deformation Performance Analysis of a Truss Structure Based on the Deformation Decomposition Method

Trusses are among the basic components of large-span bridges and large-space structures. A method is proposed to conduct a comprehensive deformation analysis of a truss in terms of the basic rigid body displacements and the tension and compression deformation based on complete mathematical orthogonality and mechanical equilibrium. The correctness of the proposed method is verified by comparison with a traditional strain analysis. Furthermore, a relative deformation decomposition of the mode shape is proposed to analyse in detail its relative displacement and deformation. The correctness and superiority of the proposed method are verified by comparison with the modal mass participation coefficient method and the animation from observation method. Additionally, the relative deformation decomposition of a plane truss structure is realized under any load conditions based on the superposition of mode shapes. The quantitative analysis of the basic deformation performance of a plane truss structure can also be conducted by countable mode shapes, which do not involve load conditions. Finally, the number of mode shapes that must be considered differs when using the maximum displacement and the tension and compression deformation analysis indicators.

Fatigue life assessment of high-strength steel wires: Beach marks test and numerical investigation

High-strength steel wires are widely used in large-span bridges. Fatigue damage of steel wires is becoming more and more prominent under adverse environment and repeated load. This paper performed the fatigue crack growth rate tests of high strength steel wires under different stress ratios. The striated fracture morphology was obtained by stepwise fatigue loading method. The fatigue crack growth rate of steel wire was determined by measuring fracture stripe width by optical microscope. The experimental curves of fatigue crack growth rate versus stress intensity factor range under various stress ratios were obtained. The fracture morphology of steel wires after fatigue was observed by scanning electron microscopy. The characterization parameters of fatigue crack growth and critical fracture required for numerical simulation were obtained based on experimental results and statistical method. Following that, a numerical fatigue crack propagation model was established combined with ABAQUS and FRANC3D. The numerical model was validated by experimental observations in the present study and open literature. A parametric analysis method considering initial pit depth and stress amplitude was proposed to evaluate the residual life of steel wires. The results showed that the linear elastic fracture mechanics and numerical simulation-based method can be used to assess the fatigue life of virgin and corroded steel wires.

Study on Iterative Modification Method of Parameters in the Health Monitoring of Large-Span Continuous Rigid Frame Bridges

Study on Iterative Modification Method of Parameters in the Health Monitoring of Large-Span Continuous Rigid Frame Bridges

Evaluation of the efficiency of aerodynamic dampers based on preliminary numerical modeling

The article is devoted to the issues of ensuring the stability of large-span bridge structures by means of their aerodynamic damping. Aerodynamic damping allows you to change the nature of the wind flow around structures or their individual elements, which can significantly reduce the loads that cause the occurrence of various aeroelastic phenomena. Aerodynamic damping devices (fairings, deflectors) are based on the phenomenon of changes in the circulation of the wind flow around the structure, the purpose of their use, as a rule, is to disrupt regular vortex formation. The main problem when using these devices is the lack of recommendations for their selection and the need for costly experimental studies to assess their effectiveness for each specific bridge. One of the ways to reduce the time and cost of research is preliminary numerical modeling in specialized software systems. Within the framework of this study, the most common types of aerodynamic dampers have been analyzed, and typical designs of large-span beam bridges have been selected. For the selected structures, a preliminary numerical simulation was carried out in a two-dimensional formulation. Based on the results obtained, the most effective designs of deflectors and fairings were determined.

NUMERICAL SIMULATION OF AERODYNAMIC STABILITY OF LONG-SPAN BRIDGES

Statement of the problem. The aim of the work is to simulate the resonant vibrations of the continuous beam span of the bridge in the direction perpendicular to the wind flow by the finite element method. The article deals with a non-standard situation that arose on May 20, 2010 on the bridge over the Volga River in the city of Volgograd.Results. As a result, an effective algorithm for calculating the aerodynamic stability of large-span bridge structures was developed using one of the most widespread software systems in Russia and neighboring countries - "Lira-SAPR". Recommendations for the selection and modeling of dampers are given. Conclusions. The developed algorithm makes it possible to numerically describe the disturbing force of periodic breakdown of wind flow vortices, which causes resonant oscillations of bridge spans, to apply this force to the design model in Lira-SAPR, and to obtain parameters that make it possible to assess the stress-strain state of the system during oscillations and to select the optimal characteristics of the damping devices.

Strength Analysis of Single-Symmetry Ratio for Single-Symmetry I-Beam

Double-symmetry I-beams are the most common beam cross-sections in structural building. Because that is simpler to design and analyze steel profiles than single-symmetry I-beams. However, with the advancement of economy, the improvement of the quality of life and the cultural standards, large-scale emergence of various large span bridges, special bridge-type landscapes and viaducts. Single symmetrical I-section is better than Double-symmetry I-section to fairly in line with demand characteristics and material economy. This study chooses different Iyc/Iy ratio sections, 0.229, 0.23, 0.3 and 0.5. Iyc/Iy =0.23 is the change point of the sudden drop of the strength of the compressed airfoil. In study, the section is divided into three sections of plasticity, inelasticity and elasticity for analysis and comparison. Considering the different section sizes. If the value of Lb for a small non-elastic interval is too large, the section with a smaller cross-section will reach the elastic interval. Taking all section conditions Lb into consideration, taking 1.4m as a section will reach the non-elastic interval, if the value of the longer Lb is too small, the section with the larger section does not reach the elastic interval. In study, 10m is taken as the section to reach the elastic interval, orientation the AISC ( 2017 ) specification is used to analyze the I-beam. Symmetrical wing plate cross-sections were increased and reduced. The strength of the cross-sections between the compressed side and the tensioned side was discussed, and a single-symmetric I-section with the best cross-sectional efficiency was proposed.

Seismic reliability evaluation of bridges under spatially varying ground motions using a four-parameter distribution

Large-span bridges are often subjected to spatially varying ground motion (SVGM) excitations. Meanwhile, bridge structures and ground motion excitations generally present a large degree of inherent uncertainties. Carrying out the seismic reliability analysis of bridges under SVGMs can provide a direct assessment for the safety probability of bridges during an earthquake event and is of paramount importance for the probabilistic performance analysis of bridges. To this end, this study proposes a new method for the seismic reliability evaluation of random nonlinear bridges subjected to SVGMs, which tackles the drawback of the current seismic reliability analysis method that can only be applied for uniform seismic excitations. To implement, the space correlated ground motions are first generated via a random function-based spectral representation method, based on which the uncertainty of ground motions is characterized by three elementary random variables. The first-passage probability of bridges under SVSGMs is then derived by the equivalent extreme value distribution (EVD), which is approximated by a flexible four-parameter distribution, i.e., shifted generalized lognormal distribution (SGLD). To estimate the parameters in the SGLD model with high efficiency and accuracy, a novel fractional moment-based method is proposed. A numerical example of a two-span continuous box-girder bridge subjected to space varying site conditions is investigated to verify and exemplify the proposed method. The results demonstrate that: 1) The proposed method is efficient and accurate for the seismic reliability of bridge under SVGM, even at low failure probability levels, and the computational burden of the proposed method is less than 2% of that of MCS; 2) The spatial variability is significantly influential on the seismic reliability of the bridge, ignoring the spatial variability of seismic excitation will significantly underestimate the failure probability of the bridge.

Holistic Life‐Cycle Analysis of Bridge Solutions

AbstractSteel in bridge constructions is often associated with very large span bridges due to its favorable relationship between strength and weight. But even for bridges with small and medium spans of up to 60 m, steel combined with concrete as a composite bridge can lead to economically justifiable constructions, especially when the performance during the complete life‐cycle is integrated. In this paper, two life‐cycle oriented calculation methods (life‐cycle costs and external costs) are introduced and applied. As a result, comparisons between two abutment solutions (conventional reinforced concrete abutment and a permanent steel sheet pile abutment) and two superstructure variants (steel composite construction and in‐situ prestressed concrete superstructure) are presented. It is shown that accelerated construction processes, durable materials, and a smart bridge‐design considering actual technological developments lead to economically advantageous solution for traffic infrastructures.

Early Warning Method for Bearing Displacement of Long-Span Bridges Using a Proposed Time-Varying Temperature–Displacement Model

Bearing displacement is a necessary monitoring index for a long-span bridge because abnormal bearing displacements could result from structural deterioration or damage. Therefore, an early warning method is established for bearing displacement of long-span bridges. In this study, a novel time-varying temperature–displacement nonlinear model, which can eliminate the model error induced by temperature field simplification, is first proposed to accurately estimate bearing displacement. Then, early warning methods for abnormal displacement and out-of-bounds displacement of bearings are established using estimation errors, and different warning levels are delineated depending on combinations of the two types of early warning, followed by an implementation procedure for the early warning method. Finally, the long-term monitoring data of a large-span bridge are utilized to validate the advantage of the proposed time-varying model and the effectiveness of the early warning method. The results show that the modeling and prediction errors of the time-varying model are smaller than that of the linear model. Additionally, attention needs to be paid to the changes in the warning information for bearings with large modeling errors, which will correspond to a relatively high warning level.

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON THE FLEXURAL BEHAVIOR OF STEEL-UHPC COMPOSITE SLABS WITH PERFOBOND RIB SHEAR CONNECTORS

A new type of steel-ultra-high performance concrete (UHPC) composite slab with perfobond rib shear connectors (PBL shear connectors) is studied, which can be used as large-span bridge decks and floors in buildings. According to the deck system of an ultra-long-span composite cable-stayed bridge, full-scale tests on three steel-UHPC composite slabs (SUCS) and a steel-C60 composite slab (SCCS) were conducted. The influence of the number and type of shear connectors were investigated. The experimental results demonstrate that, subjected to concentrated load, typical flexural failure of SUCS occurred while punching failure of SCCS occurred; that the SUCS possessed much higher ultimate capacity, rigidity and ductility than the SCCS with the same thickness did; that the specimen with sufficient perfobond rib shear connectors exhibited the best mechanical performance among the three SUCSs. Elaborate finite element models of the SUCSs were established in ABAQUS, which can reproduce the load-deflection curves obtained from the tests. Parametric study is conducted adopting the established finite element models.

Bridge displacement estimation by fusing accelerometer and strain gauge measurements

For large-span bridge monitoring, displacement measurement is essential. However, it remains challenging to accurately estimate bridge displacement. When displacement is calculated by the double integration of acceleration, a low-frequency drift appears in the estimated displacement. Displacement can also be estimated from strains based on the Euler–Bernoulli beam theory. However, prior knowledge of the mode shapes and the neutral axis location of the target bridge are required for strain–displacement transformation. In this study, we propose a finite impulse response filter-based displacement estimation technique by fusing strain and acceleration measurements. First, the relationship between displacement and strain is established, and the parameter associated with this strain–displacement transformation is estimated from strain and acceleration measurements using a recursive least squares algorithm. Next, the low-frequency displacement estimated from the strain measurements and the high-frequency displacement obtained from an acceleration measurement are combined for high-fidelity displacement estimation. The feasibility of the proposed technique was examined via a series of numerical simulations, a lab-scale experiment, and a field test. The uniqueness of this study lies in the fact that the displacement and the unknown parameter in strain–displacement transformation are estimated simultaneously and the accuracy of displacement estimation is improved in comparison with those of previous data fusion techniques.

Safety Assessment of Rigid Frame Cantilever Construction Based on Matter-Element and Extension

In order to effectively evaluate the safety status of the cantilever construction of a large-span rigid frame bridge, this paper takes a four-span rigid frame bridge as the engineering background, selects the failure probability of the cantilever construction, the natural environment, the cantilever construction operation, and the management level as the evaluation factors and divides the possibility level into Five levels, an extension model is established to evaluate the cantilever construction of the bridge. This paper first uses fuzzy comprehensive evaluation to quantify the natural environment and cantilever construction technology, then calculates the failure probability of the bridge cantilever construction based on Monte Carlo theory, and finally scores according to the management level of the management system. Invite relevant experts to obtain the weight set of each evaluation factor through the 1-9 scale method, and use the goodness evaluation method in the matter-element extension method for evaluation. The results show that the safety assessment result of the cantilever construction of the bridge is a medium risk, which provides a reliable basis for predicting and avoiding risks. Based on the matter-element extension method, the rigid frame cantilever construction safety assessment takes into account the uncertainty and ambiguity of failure, and more objectively reflects the safety status of the cantilever construction during the construction period. The calculation results of different safety evaluation models are compared with the results of this paper, which verifies the feasibility and effectiveness of the matter-element extension theory applied to the safety evaluation of cantilever construction.

Walking-Type Bidirectional Incremental Launching and Mid-Span Closure Technology for Steel Box Girders with Long Cantilevers

Unidirectional incremental launching is not applicable for the incremental launching construction of large-span bridges owing to the span capacity of steel box girders is restricted by the cantilever length and the setting of temporary piers. Aiming at the limitation, by taking Qingdao (Shandong Province)–Lanzhou (Gansu Province) expressway bridge crossing over the main canal in the South-to-North Water Diversion Project as the engineering background, a key construction technique, that is, bidirectional incremental launching and mid-span closure of steel box girders with long cantilevers was proposed. On this basis, the walking-type incremental launching device system and the technique of bidirectional incremental launching and mid-span closure were explored and also a finite element analysis model was established to compute the pre-camber. Moreover, the results of the alignment control of structures during the construction were compared and analyzed. The research result showed that during the construction using bidirectional incremental launching and mid-span closure, it was unnecessary to set the steel launching nose and it was able to greatly improve the span capacity of steel box girders and the construction efficiency during incremental launching. The research provides reliable experience in engineering practice for the future similar engineering.

The Incremental Launching Construction Technology of Pontoon Pivot Conversion of Large-span Steel Arch Bridge

Abstract With the progress of building materials and building technology, the span of bridges is becoming larger and larger. This paper briefly introduces the incremental launching construction technology of a bridge and the incremental launching construction technology of pontoon fulcrum conversion, makes an instance analysis on a large-span steel arch bridge that adopted the incremental launching technology of pontoon fulcrum conversion in Shaoyang, Hunan, China, and makes a simulation calculation on the construction process using Midas civil software. The construction process was monitored using stress sensors and total station. The results showed that the simulation results of the stress and deformation changes of the steel arch bridge in the construction process were close to the actual monitoring data, and the variation trend was basically the same. The finite element model effectively simulated the stress and deformation changes of the steel arch bridge in incremental launching. With the progress of construction conditions, the maximum stress and deformation degree of the arch rib increased first and then decreased, the maximum stress and deformation degree of the main longitudinal beam showed an increase tendency, the maximum stress of the front guide beam increased first and then decreased, and the deformation degree gradually decreased.

Research on the bridge monitoring method of ground-based radar

Bridge is an important infrastructure, and with the increase of bridge construction, the factors such as material aging and traffic congestion will affect the structural health of bridges. Therefore, the special attention should be paid to the regular deformation monitoring and health assessment of bridges. Due to the increasing monitoring requirements for large scale and span bridges, some new monitoring methods should be added as a complement to traditional monitoring methods such as precise leveling, total station, GNSS, terrestrial laser scanning, and so on. With the unique advantages of non-contact and real time, the microwave interferometry technology has become one of the means for deformation monitoring of bridges. The ground-based interferometric radar system has a high sampling rate in both the time and space domain, and it can be an effective complement to traditional methods. In this paper, the basic principle of ground-based interferometric radar system for dynamic deformation monitoring is briefly described. An improved projection method for computing the deflection with ground-based radar data is illustrated and is compared with the traditional projection method. A method for local relative deformation analysis of the bridge based on the characteristics of ground-based radar data is proposed. There are two parameters described for evaluating the local deformation of the bridge. Through the analysis of the deformation process of the bridge in a static load experiment, the feasibility of the method in the actual bridge structure safety monitoring is illustrated.

Investigation of the Dynamic Performance of a Large-Span Suspension Bridge Influenced by Scouring Based on Vehicle-Bridge Coupled Vibration

To study the damage of bridge pile foundations caused by scouring, two damage mechanisms of scouring are proposed in this paper. Considering the vehicle-bridge coupled vibration in terms of two aspects of the scouring depth and erosion depth, the vertical and transversal dynamic characteristics and dynamic responses of the bridge are studied under different cases for the most sensitive vehicle speed. The dynamic characteristics include the 1st and 2nd vibration modes of the vertical and transversal directions of the bridge. The dynamic responses include the vertical and transversal dynamic load allowances and acceleration of the bridge. The souring depth is more sensitive than the erosion depth, and the 2nd vertical mode is most substantially influenced by scouring and erosion. Because of the small value of the natural frequency of the vertical vibration modes, the transversal vibration modes may be more convenient to obtain. The study of the dynamic responses shows that the scouring depth can be represented by the dynamic load allowance in the middle of the span’s section and the erosion depth can be characterized by the dynamic load allowance at the quarter location of the span’s section.

Wind characteristics of a bridge site and wind-resistance key technology in complex mountains

The random variability of mountainous area terrain and the mutual aerodynamic interference between different terrain features make the wind field in bridge sites extremely complicated, which results in considerable challenges to the wind resistance of large-span bridges. In this study, the wind characteristics of a bridge site in a typical mountainous area were determined by field measurements. The design reference wind speed was derived from historical statistics, numerical wind tunnel simulations, field measurements, etc. According to the wind characteristics of the mountainous area, the flutter performances of a bridge under non-uniform and non-stationary inflow were analyzed, and the effects of common aerodynamic measures on flutter stability were analyzed at large angles of attack. The results showed that the integrated wind speed standard in complex mountainous terrains can derived in various ways, which is significantly different from a conventional plain area. The non-uniform, large angle of attack, and non-stationary inflow has a significant impact on the flutter performance of a bridge.

Fracture acoustic emission signals identification of stay cables in bridge engineering application using deep transfer learning and wavelet analysis

Stay cables are typically exposed to the environment and traffic loading leading to degradations due to corrosion and cyclic loading after years’ in service. A non-destructive method to detect the defects of cables as early as possible is needed and important for adequate large-span bridge maintenance. Use of a status-driven acoustic emission (AE) monitoring Convolutional neural network (CNN) method is investigated by combing wavelet analysis and transfer deep learning. CNN is used to construct the relationship between AE signals’ scalograms and cable status. The trained CNN is suitable to identify the in-situ monitored signals and evaluate the current status of cables during the operation of a bridge. As a pilot study, the binary AE signals classification CNN is implemented to identify noise & fracture AE signals in static tests of a stay-cable. Accuracy of the method is investigated. In addition, the trained model is examined using AE signals which are not used in the machine learning to check possible improvements of the accuracy. Expectations in recognition of results and status-driven monitoring potentials are addressed in the paper.

The influence of the structural vibrations’ logarithmic decrement on its stability in the event of vortex excitation

The article considers the influence of the structural vibrations’ logarithmic decrement on its stability in the event of vortex excitation. The relevance of the topic is due to the widespread problem of vortex excitation in the construction and operation of large-span bridge structures. The introduction presents the characteristic features of vortex excitation as a phenomenon of aerodynamic instability. In the second section, the research method is given, the research object is described, and the considered variants of the logarithmic decrement of the beam span’s investigated construction vibrations are given. The third section presents the experimental studies’ results at the Unique Scientific Installation, Big Research Gradient Wind Tunnel, NRU MGSU in graphical form. The conclusions about increasing the structural stability with increasing values of the vibrations’ logarithmic decrement are drawn.

Dynamic analysis of the train-bridge system considering the non-linear behaviour of the track-deck interface

This article presents an efficient computational methodology for solving the train-track-bridge interaction problem, including track irregularities and considering the non-linear behaviour of the track-deck interface. One of the novelties of the work is the proposal of a specific finite element used to model the track-deck interface, based on an assembly of a friction contact element and a non-linear spring, which is generally not used in non-linear dynamic problems. This element automatically performs changes in the longitudinal resistance of the track, according to the positions of the traffic loads, and takes into account the loading history. The dynamic analyses are performed based on an iterative methodology implemented in AIVE software, which takes advantage of the advanced modeling tools of Abaqus software controlled on Matlab. This software ensures flexibility in the selection of the methods for solving the dynamic problem and allows the incorporation of non-linearities in the vehicle and bridge models, including their interfaces. A parametric study was performed in order to demonstrate the importance of including the non-linear behaviour at the track-deck interface in the evaluation of the dynamic responses of the bridge and vehicle subsystems, under different scenarios of deck temperature, horizontal stiffness of the supports and deck cross-sections. The results show that the responses of the track-deck interface are more influenced by the effects of temperature variations than by the effects of vertical traffic loads, particularly for medium and large span bridges. Significant plastic incursions were detected at the track-deck interface under realistic temperature scenarios, particularly on the side of the mobile support. Under vertical traffic loads, the extension of the regions with plastic behaviour proved to be sensitive to variations in the horizontal stiffness of the support. Additionally, another important achievement of this study was the evaluation of the plastic incursions at the track-deck interface for different bridges typologies. Relevant incursions were detected for medium and large span bridges, where the extension of these regions can reach 25–55% of the bridge span, otherwise, for short span bridges, practically no significant plasticized regions were identified. Non-linear incursions on the track-deck interface cause an overall reduction of the track-bridge stiffness, leading to an increase of the vertical movements of the bridge, and, inherently, of the vehicle’s dynamic responses. The evaluation of the extension of the ballast plastic regions for the different analysis scenarios, which is still a topic shortly addressed in the bibliography, will be particularly useful for upgrading the existing methods for assessment of the dynamic behavior of railway bridges.