Span Bridges Research Articles

Monitoring the dynamic response of a pedestrian bridge by using low-cost GNSS receivers

The development of low-cost GNSS receivers with carrier-phase measurement capacity has led to low-budget GNSS applications of higher accuracy and precision. Recent studies have mainly been carried out with those low-cost receivers for landslide monitoring and achieved promising results. In this study, the performance of two closely-spaced high-rate low-cost GNSS receivers was assessed against the robotic total station (RTS) and geodetic GNSS receiver in monitoring the dynamic response of a major pedestrian suspension bridge at the mid-span. Potential accuracy improvement by the combination of two low-cost GNSS time-series was also examined. It was proved that multi-GNSS solution is required to resolve potential outliers and offsets of the low-cost GNSS time-series, due to cycle slip induced errors. The analysis of the low-cost GNSS time-series showed that the low-cost GNSS receivers can estimate (i) the main dominant frequencies of the bridge with the same accuracy as the geodetic-grade GNSS receiver and (ii) the amplitude of the bridge response with difference of ∼3 mm with respect the geodetic GNSS receiver due to higher noise level. This study revealed the prospect of utilising low-cost GNSS sensors in monitoring dynamic displacement with frequency of 1–3 Hz, corresponding to relatively rigid structures (e.g., short span bridges, etc.).

Study on the EPSD of Wind-Induced Responses of the Sutong Bridge Using Harmonic Wavelets

Many long-span bridges are located at typhoon prone regions. With the continuous increase of the bridge span, the typhoon-induced buffeting becomes more and more prominent. In this study, based on the structural health monitoring system installed in the Sutong Bridge, the recorded buffeting responses of the main girder during typhoons Damrey and Haikui were analyzed. The run test method demonstrated that the recorded acceleration responses can be regarded as zero-mean non-stationary random processes. Hence, to capture the energy distribution of the recorded data in the time-frequency domain, the evolutionary power spectral density (EPSD) estimation was conducted using efficient generalized harmonic wavelet (GHW) and filtered harmonic wavelet (FHW), respectively. Compared with the GHW, narrower wavelet bandwidth is required by the FHW to yield a compromise between the time and frequency resolution. For the FHW-based method, the power spectral density amplitudes of the averaging EPSDs are slightly larger for certain major frequency components than those obtained by the Pwelch method. Results show that the non-stationary features of the buffeting of long-span bridges during Typhoon events should be considered. This study can also provide references for non-stationary buffeting analysis of other long-span bridges during extreme wind events.

Front Cover: Copper(I) and Gold(I) Complexes of Aminofunctionalized Phosphinines: Synthesis and Structural Characterization (Z. Anorg. Allg. Chem. 6‐7/2023)

The cover picture shows the solid-state structure of an unusual Cu4-rhombus, which is capped by a total of four chlorido ligands. Two aminofunctionalized, aromatic phosphinines coordinate in the classical σ-coordination mode via the phosphorus lone pair to two of the four Cu(I) centers. The other two phosphinines show a rare bridging μ2-coordination mode and span two of the four Cu(I) centers. (DOI: 10.1002/zaac.202200365).

Parametric analysis of variables influencing the design of I‐girder bridge decks made of high‐performance fiber reinforced concrete

AbstractDespite the good balance between notable mechanical properties and a reasonable cost, high‐performance fiber reinforced concrete (HPFRC) is not widely employed in the construction of bridges. This work is part of a larger research addressed at exploring the potential of this material for replacing standard concrete in the construction sector. Specifically, this paper focuses on the use of HPFRC to build precast simply supported I‐girders for road bridges. This work investigates the influence of several design variables on the material consumption to identify the key features that can lead to possible material savings. The variables, explored through a parametric analysis, are: (i) the concrete class (C80/95, C100/115, and C120/140); (ii) the number of beams to form the deck (from 3 to 5); (iii) the girder span‐to‐depth ratio (17, 20, and 23); (iv) the bridge span (L) (20, 40 and 60 m). One specific case of study is described in detail, and then the same procedure is applied to all the case studies. In addition, the effect of different hypotheses and formulations for the bending and shear verifications are analyzed. The results shed light on the relevance that these variables play in the final solution and how they affect the dimensioning of these elements. As main finding, this work proves that the use of HPFRC represent a material‐efficient solution for slender and long‐span precast I‐girders.

Assessing mechanical responses for damage detection in bridge spans through resonance region analysis

This article introduces a new method for evaluating the mechanical behavior of structures to detect potential damages in bridge spans. The study enables us to monitor the stiffness degradation of bridge spans over time, operating under different working conditions. The proposed approach suggests monitoring the operational status of bridge spans at different measuring points, corresponding to different levels of applied load, measurement time, and environmental conditions according to the random theory. The study results demonstrate that changes in the area under the resonance regions of the power spectrum density can provide accurate information on the change in the structural behavior during operational periods. Furthermore, the research indicates that changes in the area under resonance regions can identify hazardous points on different spans of a bridge through different measuring points. Overall, in the future, this method can assist in identifying potential damages and warning of potential hazards to improve safety and reliability for people and vehicles crossing the bridge.

Investigating the dynamic behaviour of a railway bridge subjected to over-height vehicle collision

ABSTRACT Full service without defects of railway bridges is more important than highway bridges because failure at a part of the bridge results in the blockage of the entire track and the stopping of the trains. In recent years, the problem of an over-height vehicle collision to the bridge superstructure has occurred more frequently. These collisions damage the bridge superstructure and affect the safety of the train causing many problems in railway transportation. In this study, first, a model of the concrete girder bridge was used to validate the effect of the collision load applied to the bottom of the concrete girder bridge. Then, the dynamic responses of the railway bridge simulated as concrete girders and bridge deck also track including rail, sleeper, and ballast are presented by using the finite element method. Finally, the different sensitivity analyses express that changing the bridge span length, and the value of collision loads affect the concrete girder lateral displacement at the contact area. The results show that the lateral displacements decrease with increasing the span length. Additionally, by increasing the collision forces due to increasing the velocity of the impacting object, the lateral displacement at the bottom of the girder reduces.

Analysis on the stress mechanism of the exposed steel anchor box composite cable–pylon anchorage structure

For the exposed steel anchor box cable–pylon anchorage structure, there is a good application prospect in urban bridges of medium and small span due to its good mechanical behavior, easy construction and beautiful overall appearance. This paper reveals the stress-transfer mechanism of the exposed steel anchor box cable–pylon anchorage structure through a segmental model test with a scaled-down ratio of 1:2, and focused on the effect of prestress in the pylon. Three calculation modes for the anchorage structure are proposed, and simplified calculation equations of the horizontal load distribution relationship and the vertical shear force of the stud are derived. The effects of various design parameters on the load distribution ratio, the pylon wall tension caused by shrinkage and the vertical shear force of the studs are discussed by using the simplified calculation equation. The research results show that the exposed steel anchor box cable–pylon anchorage structure has good applicability in medium and small span bridges. Prestress can significantly reduce the tensile stress of the pylon wall concrete, and improve its crack resistance. There is no significant difference between the results of the simplified calculation equations and the finite element calculation, and the simplified calculation equations meet the design requirement.

Deterioration Models for Texas Bridges and Culverts

This paper discusses 38 bridge- and eight culvert deterioration models of three bridge and one culvert condition rating stored in the National Bridge Inventory (NBI) as Items 58, 59, 60 and 62. The models were developed by age groups and by families of relevant variables such as span type, deck material, and bridges over water or land. Each model is a 2-year Markov matrix for every age group or family, containing the probabilities that each rating will remain the same, or transition to all possible lower ratings. These probabilities were calculated by counting all actual transitions in a database containing 19 years of bridge inspection data in Texas, unlike previous models which assumed that ratings cannot drop by more than 1 point in one inspection cycle. Models were validated and standard errors calculated. Updatable results were implemented in Excel workbooks and included 18-year forecasts of condition rating and network deterioration tables and curves, and comparisons between the current network condition and 10-year forecasts. The culvert models also included updatable cost forecasts to maintain the culvert network above Condition Rating 4. The main technical contribution of this project is the probabilities of bridge and culvert ratings decreasing by more than 1 in a 2-year inspection cycle being greater than zero for all condition ratings modeled (range: 8% to 61%). The models developed using the Texas data were strictly applicable to maintenance, environmental, and traffic conditions comparable to those prevalent in Texas. However, the modeling methodology is applicable to any state or location.

A FBG pull-wire vertical displacement sensor for health monitoring of medium-small span bridges

With the increase of service life, a growing number of medium-small span bridges have suffered degradation and even serious damage, and the vertical displacement is one of the significant parameters for their safety condition and performance evaluation. In terms of medium-small span bridges, to solve the difficulty for long term vertical displacement measuring and the demand for low-cost monitoring, this paper proposes a fiber Bragg grating (FBG) pull-wire vertical displacement sensor, which owns advantages of low cost, high accuracy and convenient installation. Firstly, the calibration and temperature correction of the sensor were carried out. Secondly, the influences of the fixed angle and sag effect of the sensor on measuring results were investigated. Finally, the sensor was installed in an in-service hollow slab bridge and the static and dynamic load experiments were carried out. Results show that the linearity of the proposed sensor is 0.998, the sensitivity is 7.87 pm/mm, the hysteresis error is 1.54 %, the temperature correction coefficient is 18.08 pm/°C, the relative combined uncertainties are within 4 %; the fixed angle of this sensor is recommended to choose in the range of 15°-30° in order to obtain higher measuring accuracy; when θ = 15° and the radius of the external wire is 0.3 mm, the limit of the external wire length can be set to 19.5 m to avoid the influence of the wire sag effect on measuring results; the sensor is feasible in vertical displacement measurement of in-service medium-small span bridge, and the relative measuring errors in both static and dynamic load experiments are less than 5 %.

Flutter Control of Active Aerodynamic Flaps Mounted on Streamlined Bridge Deck Fairing Edges: An Experimental Study

Traditional aerodynamic measures with fixed geometric shapes make it difficult to relieve the wind-induced vibration issues under the continuous expansion of bridge spans. Active aerodynamic control measures would be an alternative way to improve the wind vibration performance of long-span bridges. In this study, a bridge flutter control method based on active flaps was proposed, and the main girder-active flap-suspended aeroelastic model was designed to study the control effect. A pair of active flaps was installed on both sides of the box girder near the lateral fairings, and the movement signal of the main girder was detected using internal sensors. The two flaps move relative to the deck according to the preset equations of motion. This improved the flutter stability of the system with high effectiveness compared to traditional passive aerodynamic measures. By adjusting the gain coefficient in the motion function of the flaps and the phase difference between the flaps and the deck, the changing characteristics of the critical flutter wind speed were revealed with a deeper understanding of the relationship between the phase differences and gain coefficient of the active flaps and main girder. Studies have shown that the flutter performance of the deck-flap system is significantly affected by the phase difference and gain coefficient on both sides of the aerodynamic flap. The control law of the windward flap is relatively stable, but the control effect of the leeward flap is greatly affected by the movement of the windward flap.

A novel extraction method for the actual influence line of bridge structures

This paper presents a novel numerical method for accurately extracting bridge influence line (IL) from dynamic responses of general bridge structures. In this method, the IL is approximated by a multi-segment basis function, and a normalized vehicle-induced bridge response is employed as initial IL. Subsequently, an iterative fitting calculation method is proposed to eliminate fluctuation interference in the initial IL curve such that highly accurate actual bridge IL with quasi-static characteristics can be extracted. The feasibility and accuracy of the proposed IL extraction approach for bridges are validated through numerical and experimental studies. Based on which, a parametric study is conducted to identify key parameters affecting the deflection IL extraction performance. The results show that the proposed method can extract the actual bridge IL accurately and efficiently when the segment length is in the range 1/32–1/16 of the bridge span. Compared with conventional methods, the proposed method can extract the actual IL under more flexible testing conditions. Hence, the presented numerical approach is promising for IL-based bridge structure applications.

On the use of an active turbulence grid in wind tunnel testing of bridge decks

A new experimental set-up with an active turbulence grid for wind tunnel testing of bridge decks in homogeneous freestream turbulence is presented. Unlike other active turbulence generators applied in bridge aerodynamics, the active turbulence grid generates stochastic turbulence and not quasi-harmonic velocity fluctuations that are correlated along the section model. A twin deck and a single deck section model are tested for aerodynamic properties using different incoming turbulence. The results show that the static coefficients can be highly sensitive to the properties of the incoming turbulence and that the sensitivity varies between the tested cross-sections. Significant changes in aerodynamic derivatives were observed with changing turbulence properties. The turbulence-dependent changes in the aerodynamic derivatives are less clear compared to the static coefficients since the presence of turbulence and buffeting forces makes it more difficult to identify the aerodynamic derivatives. It is also clear that the turbulence creates large variations in the instantaneous angles of attack, questioning the validity of linear models for prediction of self-excited forces. It is concluded that the active turbulence grid is a valuable asset in bridge aerodynamics research as it allows for novel studies of bridge aerodynamic properties in conditions relevant to long span bridge design.

A rapid evaluation method based on natural frequency for post-earthquake traffic capacity of small and medium span bridges

To improve the efficiency of evaluating the traffic capacity of bridges after the earthquake, a rapid method based on natural frequency for evaluating post-earthquake traffic capacity of small and medium-span bridges is proposed. Firstly, OpenSees software is selected to establish the seismic numerical analysis model of the pier, and the pressure of the main girder on the pier is equivalent to concentrated mass to extract the dynamic characteristics of the pier. The horizontal thrust on the pier top is adopted to simulate seismic action by the pseudo-static method, and the horizontal thrust is controlled by the maximum horizontal displacement. The value range of pier parameters is determined according to the definition of the regular bridge and relevant design data, then the design parameters and maximum horizontal displacement of each pier are sampled by the Latin hypercube sampling method to obtain various combined working conditions. Subsequently, the natural frequency, residual displacement and bearing capacity of the pier under different working conditions are obtained through numerical simulation. The relationship between natural frequency and residual bearing capacity of the pier after the earthquake is established in light of the simulation results of pier models. Then, the vehicle load is arranged on the basis of the most unfavorable loading principle, and the bearable maximum vehicle weight of the bridge is estimated from the bearing capacity of each pier, so that the traffic capacity of the bridge after the earthquake can be quickly evaluated by the change of natural frequency of piers. Finally, the reliability of the pier numerical model and residual displacement calculation method are verified by the test results of piers. The application process of the evaluation method proposed in this paper is illustrated by two typical examples of a simply supported beam bridge and a continuous beam bridge, which proves the feasibility of this method.

Bridge deck analysis of transversely post-tensioned concrete box girder bridges

For rural bridges in Australia, a common design practice is pouring in-situ concrete on top of beams in order to tie all the beams together and distribute load. However, pouring concrete on-site creates more risk and contractors prefer to avoid it. Another method is using transverse post tensioning to tie beams. This article investigated the behaviour of transverse post-tensioning bars in providing load distribution between beams and ultimately comment on their effectiveness compared to in-situ poured decks. Currently, the industry has not completely investigated this matter in order to design post-tensioning accurately. Conservative estimates are currently used in industry today. Current practice is 50% of the design load on the beam where the load is applied in their design assumptions which is quite high. The team modelled concrete box girder bridges with transverse post-tensioning using grillage method. Several factors were investigated including bridge length and width, bridge skew and beam type. From the models, the team concluded that increasing the bridge span increases the load distribution, the load distribution difference is negligible for skew between 0 and 20 degrees and larger shear actions are observed with increased skew and width. It was determined that the worst-case total load on the beam where the load as applied was found to be 40.5%, 9.5% less than current practice. It is recommended that a similar investigation is conducted using a finite element method to gain a deeper understanding.

An investigation of dynamic vehicle-bridge interaction effects based on a comprehensive set of trains and bridges

The consideration of interaction effects between vehicle and structure is an important aspect in the dynamic analysis of railway bridges. They usually lead to a reduction of the structural responses compared to computations without consideration of the vehicle-bridge interaction. The interaction effects can either be accounted for by Finite Element analysis including multi-body models of the vehicles or in a simplified way – as adopted by the actual regulations – by artificially increasing the bridge damping. In this way, a simplified dynamic analysis under consideration of the interaction effects is possible using the moving load model.However, several studies have shown that the current approach of the additional damping included in Eurocode 1 is non-conservative in many cases, possibly leading to an underestimation of the structural responses. The approach in Eurocode 1 as well as the more recently proposed approaches were based on a limited number of combinations of trains and bridges. In order to verify these approaches in a more thorough way, the present paper investigates the vehicle-bridge interaction effects based on 25 real high-speed passenger trains (including conventional and articulated trains) and over 100 single-span bridges with spans ranging from 5m to 55m.A typical criterion of analyzing the vehicle-bridge interaction phenomenon is the reduction of the structural acceleration computed using a 2D multi-body representation of the vehicle compared to the simplified moving load approach. Therefore, the reduction of the acceleration due to the interaction is discussed in detail and put in relation to the results of previous research. The results of over 800 000dynamic analyses performed in the present study confirm that the additional damping approach depending on the bridge span as included in Eurocode 1 overestimates the actual vehicle-bridge interaction effects. Furthermore, the results show that recent additional damping approaches depending on bridge and train characteristics lead to more reliable additional damping values. Their application requires public availability of train characteristics and an extension of the approaches for articulated as well as heterogeneous trains.

Experimental and Numerical Investigation of the Anti-Overturning Theory of Single-Column Pier Bridges

In recent years, overturning accidents at single-pier bridges have occurred frequently, resulting in significant property losses and safety accidents. Overturning accidents show that there are still many hidden dangers in the design, operation, and management of existing single-pier bridges. Therefore, this paper takes the K503 + 647.4 separated overpass of the Hegang–Dalian Expressway as the research object and carries out an onsite anti-overturning stability test of a single-column pier bridge. Through loading under various working conditions, the displacement changes of each support are measured, and the reaction changes of the supports are calculated. In the process of simulating the field test using the finite element program ANSYS, a rigid model based on ideal support and an elastic model considering beam deformation are established, and the accuracy of the elastic model is verified by comparison with the field-measured data. Furthermore, a series of parameters, such as the bridge side-span ratio, bridge span number, bearing spacing, loading position, and torsional rigidity, are varied, and finite element simulation is carried out on the basis of the elastic model. Through comparison of the results, a relationship between the parameters of the single-pier bridge and the anti-overturning ability is obtained, which provides a theoretical basis for anti-overturning design research and the effective reinforcement of single-pier bridges.

Fatigue performance and optimal design of corrugated steel–concrete composite bridge deck

Orthotropic steel bridge deck (OSD) has been widely used in long and medium span bridges. However, traditional OSD with U-ribs is prone to fatigue cracking at the deck-to-rib welded joint. Corrugated steel–concrete composite bridge deck (CSCCBD) composed of corrugated steel plate, concrete layer and perforated plate shear connectors was proposed recently to improve the fatigue performance of the bridge deck. In this paper, comparing of the fatigue performance of OSD and CSCCBD was conducted through finite element (FE) analysis. The results showed that the stress amplitude of deck-to-rib welded joint of CSCCBD was reduced by more than 90 % compared with OSD. The fatigue problem of deck-to-rib welded joints can be solved fundamentally. It is further studied that distribution of fatigue vulnerability details of CSCCBD. The most unfavorable fatigue vulnerability details are located around the diaphragm-to-rib weld. The fatigue life of CSCCBD was evaluated based on the linear cumulative damage theory. Consequently, the effect of diaphragm cut-out on the fatigue performance of CSCCBD was studied. It was found that the diaphragm without cut-out can effectively reduce the stress amplitude caused by vehicles, and increase the earliest fatigue cracking life of details around the diaphragm-to-rib weld from 2.16 years to 43.4 years compared with OSD. Finally, the section form of CSCCBD without cut-out was optimized by response surface method (RSM). It was proved that RSM was adequate for the optimization design of CSCCBD.

Assessing bridge stiffness decline using power spectral density: A case study on Saigon Bridge

Bridges, especially civil infrastructure, serve a vital role in social activities. A damaged bridge can cause severe consequences such as traffic congestion, economic impacts, and loss of lives. Therefore, it is crucial for infrastructure management communities to detect and assess the condition of damaged bridges to ensure safety. To address this issue, in this study, the authors have put forth a novel set of parameters that can be used to evaluate the reduction in stiffness of spans over time. The stiffness is a critical factor that determines its structural integrity, and it is essential to monitor any changes in this parameter over the lifespan of the bridge. The proposed parameters take into account factors such as the age of the bridge, the material used in its construction, and environmental factors that may contribute to the degradation of the structure. They conducted experiments on a beam structure to evaluate its ability to monitor the reduction in bearing capacity of Saigon Bridge's spans using these parameters. To analyze the vibration signals from a randomized traffic load model, they utilized the power spectral density. The results of the study suggest a correlation between the frequency of harmonics and the high-frequency regions observed in the power spectral density and the decline in the stiffness of spans.

Calculation of the stress-strain state of monolithic bridges on the action of real seismic impacts

To improve the transport infrastructure of the Republic of Uzbekistan, there is a tendency to build monolithic structures of bridges and overpasses. The article presents the calculation of a monolithic bridge on the 1083rd km of the M-39 highway passing through the city of Samarkand. The results of the monolithic bridge calculation on dynamic loads are presented, based on the records of two real seismograms of two dangerous earthquakes registered for a system with a spectral composition: the Gazli (Uzbekistan) and Manjil (Iran) earthquakes. The results of calculations of longitudinal and vertical displacements, and normal stress in the upper and lower parts of the span along the length of the bridge were analyzed. The calculations performed, show that the span structure and bridge supports have an overestimated margin of safety for an 8-point earthquake according to MSK-64. To ensure the guaranteed seismic safety of bridge structures, it is required to conduct design calculations based on a set of records of earthquake events that are close in dominant frequencies to the characteristics of the construction site. This provision must be included in the relevant regulatory documents.

Refinement of the Process Capability Index Сalculation

The variability of product performance is the reason for the introduction of special methods to ensure product quality, particularly statistical methods. These include introducing statistical process control (SPC) in production and calculating the process capability index to determine the manufacturing ability to meet the product’s quality requirements. To a large extent, the ability of a process to meet the requirements was determined by the location of the process or the mathematical expectation of the controlled quality characteristic value. Process setup center variability within the boundaries of the Shewhart control chart of the average values was supposed to be the natural state for a statistically controlled process. However, the calculation of the process capability index did not consider the possibility of a shift in the actual value of the process setup center for a controlled characteristic from its mathematical expectation. It was proposed to adjust the process capability index for the setup center’s possible deviation. It demonstrated the possibility of critical errors in determining the ability of a production process to meet requirements without considering the process setup center. The effectiveness of the proposed solutions was also demonstrated by the example of determining the ability of the welding wire manufacturing process to meet the requirements for metal yield strength of the welded joint of metal bridge span constructions.