Concrete Box Girder Bridge Research Articles

Comprehensive review of seismic performance assessment for skew-reinforced concrete box-girder bridges

Comprehensive review of seismic performance assessment for skew-reinforced concrete box-girder bridges

Improved Deflection Prediction Model for PSC Box Girder with Stay Cable System during Tensioning Phase

To improve the accuracy of deflection prediction for prestressed concrete (PSC) box-girder bridges with a stay cable system (SCS) during tensioning, this study employs the Latin hypercube sampling (LHS) technique to sample random variables affecting long-term deflection of the main girder. A long-term deflection randomness analysis model is established, and the shear stiffness degradation factor is included to quantify the contribution of diagonal web cracking to the main girder deflection. Uncertainty and sensitivity analysis are conducted for the Dongming Huanghe River Highway Bridge. An objective function is applied to select the optimal combination of random variables, and a modified model is established and verified for accuracy. Results show that diagonal web-cracking accounts for 8.8% of total deflection and cannot be ignored, and the prestressed tension control stress, creep uncertainty coefficient, and concrete density significantly impact long-term deflection. The modified model predicts deflection with greater accuracy than the mean value model.

UAV photogrammetry and laser scanning of bridges: a new methodology and its application to a case study

The state of preservation of infrastructures, such as bridges and viaducts, plays a crucial role in the economic development of a country. To this aim, a multi-level knowledge-based approach providing guidance on several aspects included in the management of large bridge inventories is utterly needed. In particular, the knowledge of bridge geometry, construction details, and structural defectiveness is of pivotal importance. Accordingly, methodologies to achieve the systematic collection of this information should be investigated and tested in practical applications. This paper presents a new methodology for surveying reinforced concrete box girder bridges using UAV photogrammetry and laser scanning. The proposed methodology is based on the adoption of predefined trajectories to accelerate surveying procedures and achieve high-quality results. The use of UAV photogrammetry allows for capturing high-resolution images of the entire structure, structural flaws included, while laser scanning provides measurements of geometric details. By integrating the data acquired, an accurate 3D digital twin of the bridge can be obtained, and its structural defects can be assessed. A comparison between the employed technologies is also proposed. Although UAV photogrammetry is slightly less precise than laser scanning in detecting geometries and construction details, it offers a more cost-effective and faster alternative to traditional laser scanning, primarily due to its accessibility in the field, without compromising the quality and reliability of the collected data. The proposed methodology has been applied on a case study reinforced concrete box girder bridge located in central Italy. The obtained results highlight the effectiveness of the proposed approach for the systematic collection of essential data for the knowledge of the assets and suggest that UAV photogrammetry can almost replace traditional laser scanning of bridges within the structural risk assessment process.

A BIM-based approach for risk assessment and management in roadway bridges: preliminary results from the application to a post- tensioned concrete box girder bridge

The Guidelines for Risk Classification and Management, Safety Assessment, and Monitoring of Existing Bridges, released in 2020 by the Italian Ministry of Infrastructures and Transport, promote the use of Building Information Modeling (BIM) environment as one of the main tools to achieve informed risk mitigation of infrastructures. To date, BIM environments are often only used as repositories of information from different entities involved in bridge design, management, and retrofitting. However, to achieve informed risk mitigation of bridges, the current BIM paradigms should be expanded by integrating new typologies of data, such as those from Structural Health Monitoring (SHM) systems, and functionalities, such as the ability to process stored data directly within the BIM environments. In this light, this paper presents a BIM-based approach conceived to achieve comprehensive assessment and management of the risk conditions and structural performance of bridges. To this end, specific algorithms have been implemented into the selected BIM environment to perform tasks such as assessing the preliminary risk level of a bridge according to the methodology proposed by the Italian Guidelines, evaluating the outcomes from visual inspections to estimate its defect level, storing and processing data from SHM systems installed on the structure, and more. The paper also presents the first application of the proposed BIM-based approach to a post-tensioned box girder bridge belonging to the Italian road network.

Dynamic characterization of a curved nine-spans pre-stressed concrete box girder bridge with half-joints

In recent years, the failure of many bridges has pressed governments all over the world to increase investments and to enact new monitoring regulations. In the Italian context, the Ministry of Infrastructure and Transport answered to that challenge by enacting the new Guidelines on Risk Classification and Management, Safety Assessment and Monitoring of Existing Bridges, in 2022. In this new regulation, Structural Health Monitoring (SHM) plays a fundamental role, complementing traditional periodic inspections by carrying out low intrusive non-destructive analyses. In this field, Operational Modal Analysis (OMA) is a vibration-based method consisting in the processing of the ambient accelerations recorded on the structure in order to extract and track its modal features. The final goal of continuous OMA is the timely identification of possible damage-induced persistent variations in the modal features of the monitored structure. This is why one of the most recent advances in OMA algorithms is related to the development of continuous Automated OMA embedded in high-potential software, to enable the infrastructure management authorities to realize large-scale monitoring of bridge networks. Many road bridges are however long multi-span bridges which require numerous sensors for their monitoring, thus making automated OMA especially challenging from the computational point of view. The aim of the work is to contribute to a more computationally affordable automated OMA for long bridges, by proposing to subdivide the OMA task considering suitable selections of subgroups of sensors. The proposed approach is illustrated in a case study consisting of a curved nine-spans pre-stressed concrete box girder bridge with 10 half-joints and equipped with more than 50 sensors.

SHM-based digital twin calibration of a post-tensioned reinforced concrete bridge with vertically prestressed internal joints

Post-tensioned concrete box-girder bridges exhibit complex time-varying behavior due to factors like creep, shrinkage, and steel relaxation. Predicting these phenomena accurately at the design phase is a difficult task, often leading to underestimation of their impact. Particularly in bridges constructed using a balanced cantilever scheme and cast-in-place concrete, the aging process and the timing of load application can influence the time-dependent behavior of the structure. The combination of these effects can result in significant vertical displacements and serviceability issues that necessitate careful consideration. The Italian Bridge Guidelines introduced specific evaluations for post-tensioned concrete bridges, which often require the support of FE models for accurate safety evaluation. The paper reports the investigations carried out on a very challenging post-tensioned concrete box-girder bridge with vertically prestressed internal joints. The main objective is to calibrate a predictive FE model of the bridge by integrating information from design reports and drawings, static and dynamic non-destructive experimental tests as well as onsite inspections and digital surveys to characterize the presence of defects. The data obtained from the test campaign are utilized to build an accurate model, which is further calibrated to become an actual digital twin of the real structure employing ambient vibration tests (AVT) to identify the dynamic behavior of the structure. The digital twin thus obtained will serve as a tool for performing reliability analyses and predicting future serviceability or collapse issues.

Reliability Assessment Approach for Fire Resistance Performance of Prestressed Steel–Concrete Box Girder Bridges

This paper employs probability methods to evaluate the fire safety performance of prestressed steel–concrete beam bridges based on simulation experimental research. Firstly, fire simulation experimental sample analysis was conducted on actual small box girder bridges to assess the structural response of prestressed steel–concrete structures to fire, as is in line with engineering practice. Next, we constructed a reliability analysis model to investigate the fire resistance performance of prestressed steel–concrete beam bridges. Combining reliability theory with the finite element method, we established a reliability analysis method for the fire resistance performance of prestressed steel–concrete beam bridges. Subsequently, we proposed a safety factor evaluation model for the fire resistance performance of prestressed steel–concrete beam bridges and then established a safety factor evaluation method for the fire resistance performance of prestressed steel–concrete beam bridges based on reliability back analysis. Finally, based on the analysis of the post-fire structural response in the specific case of a steel–concrete continuous beam bridge project moving from conditions of being simply supported to continuously prestressed, a structural resistance sample of the prestressed steel–concrete beam bridge was generated via the uniform design method, and statistical analysis was conducted. Subsequently, probability methods were used to evaluate the safety of the prestressed steel–concrete beam bridge after a fire. Through analysis, we concluded that the duration of the fire had a significant impact on the structural performance of prestressed steel–concrete beam bridges and that the randomness of parameters had a significant impact on the safety reserve of prestressed steel–concrete beam bridges following the fire. Going forward, it is necessary to pay attention to this factor in specific engineering practices and strengthen the monitoring and statistical analysis of structural random characteristics.

PROCEEDINGS IN UAS-ASSISTED BRIDGE INSPECTIONS: RTK-BASED PHOTOGRAMMETRIC RECONSTRUCTION AND SPATIAL FILTERING

Abstract. Traditional bridge inspections present considerable challenges in terms of efficiency and accuracy. However, recent advancements in Unmanned Aerial Systems (UASs) and deep learning for object detection have opened up new avenues for automatic bridge damage detection. We present a comprehensive framework leveraging these technologies for automated damage detection in UAS imagery, followed by accurate mapping of the damage predictions on photogrammetric models. In this work, we propose a photogrammetric procedure to retrieve geolocated bridge models solely based on Real-Time Kinematics (RTK) information. Within the damage detection step, we conduct extensive testing and optimization of model hyperparameters using YOLOv8 and Slicing Aided Hyper Interference (SAHI). Next, we map the predictions onto the 3D model using ray casting, allowing to group and filter the predictions by their area and position. Finally, a Graphical User Interface (GUI) allows bridge inspectors to identify false positive predictions, generate new training data, and directly measure damage dimensions in the images. Validation on a concrete box girder bridge resulted in a photogrammetric model with a mean error of 1.3 cm, negating the need for ground control points. Our model training process revealed substantial performance variations between training and test datasets, underscoring the importance of evaluating optimal hyperparameters on UAS inspection images rather than relying on the validation metrics. Lastly, we successfully map the detected damage and create new training data from the UAS inspection images. This framework significantly enhances bridge inspection accuracy and efficiency, providing a strong foundation for future developments in automated bridge inspections.

Torsional Strength of Horizontally Curved Continuous Reinforced Concrete Box Girder Bridges

Torsional Strength of Horizontally Curved Continuous Reinforced Concrete Box Girder Bridges

Operational modal identification of structures based on improved empirical wavelet transform

When empirical wavelet transform (EWT) is used to identify the modal parameters of civil engineering structures, the frequency band division is generally not accurate due to the noise effect on the Fourier spectrum. This phenomenon will lead to modal mixing and false modes in the analysis results. Therefore, this article establishes a signal frequency band division method by taking advantages of maximal spectrum technique and spectral skewness index. Combining the random decrement technique (RDT) and the least square method of single component modal parameter identification, an adaptive approach based on the improved EWT for operational modal parameter identification of civil engineering structures under stationary environmental excitations is proposed. The traditional frequency band division method based on EWT can not completely and effectively divide the meaningful frequency bands. While the proposed frequency band division technology based on the spectral skewness index can prevent the phenomenon of insufficient division and excessive division and realize adaptive frequency band division. The effectiveness of the proposed approach is validated by a numerical three-story frame and a field three-span concrete box girder bridge under ambient vibrations. The modal identification results from both numerical and experimental validations demonstrate that the proposed approach can effectively and accurately decompose the vibration responses and identify the structural modal parameters under operational conditions.

Investigation on the Through-Thickness Temperature Gradient and Thermal Stress of Concrete Box Girders

Bridges are generally affected by thermal loads which include the daily cycle, seasonal cycle and annual cycle. Thermal loads mode and thermal effects on bridges, especially for concrete girders, are quite essential but complicated. To investigate the temperature field and thermal stress in the thickness direction of a concrete box girder, the temperature field of a prestressed concrete continuous box girder bridge is monitored, and the temperature distribution in the thickness direction of the concrete box girder is analyzed. Finite element simulation, utilizing air elements specifically designed for concrete box girders, is employed to analyze the temperature field and thermal stress profiles along the thickness of the slab. The findings indicate a variation in temperature along the thickness of the concrete box girder slab. The most significant temperature differential, reaching up to 10.7 °C, is observed along the thickness of the top slab, followed by the bottom plate, with the web exhibiting relatively smaller differentials. Temperature in the full thickness range has a significant impact on the top plate, while the web plate and bottom plate are greatly influenced by temperature ranging from the outer surface to the center of the plate thickness. The temperature difference between the center of the plate thickness and the inner surface is approximately 0. The variation in temperature due to the variation in thickness direction is a temporal factor, wherein the outer layer of the roof is primarily compressed, while the inner layer is subjected to tension. The external surface of the web is mainly compressed. The stress exerted by the internal surface temperature is minimal. The internal and external surface effects of the floor are similar, and as time passes, tensile and compressive stresses appear.

Utjecaj kuta djelovanja potresa na seizmičko ponašanje betonskih mostova na autocestama

This study aims to evaluate the effect of earthquake angle on the seismic performance of a concrete highway bridge. As a numerical example, a twin prestressed concrete box-girder highway bridge was analysed using finite element methods. The bridge was subjected to the 1992 Erzincan earthquake ground accelerations in 19 directions with values ranging from 0° to 90° in 5-degree increments. To evaluate the effects of different earthquake angles on seismic performance, variations in the maximum displacements, internal forces and principal stresses on the bridge deck, columns, isolator and foundation were studied . The results changed considerably for different earthquake angles. Variations in the displacement, internal forces and principal stresses occurred at different incidence angles. In other words, there is no unique angle of incidence for each structure.

Time-lag effect of temperature-induced strain for concrete box girder bridges

Time-lag effect of temperature-induced strain for concrete box girder bridges

Shear stress migration in a tapered girder with trapezoidal corrugated steel webs

This study conducted a comprehensive investigation into the shear stress migration of a tapered prestressed concrete (PC) continuous box girder bridge with trapezoidal corrugated steel webs (TCSWs) throughout the entire construction process, including cantilever construction, structural system transformation and external prestressing tendon tensioning. The results revealed that the basic assumptions, which state that TCSWs bear all the shear force and that only the vertical component of the external prestressing contributes to shear stress when considering its contribution, are not valid for the shear design of tapered PC girder bridges with TCSWs. The horizontal component of the external prestressing and bending moments can cause additional shear forces via the Resal effect, which results in the migration of the shear stresses between the curved bottom concrete slabs and TCSWs. This study investigated the mechanism through which the Resal effect and external prestressing influence the migration of shear stress in the entire construction process. The results revealed that within continuous girders, the Resal effect exhibits both positive and negative implications. Specifically, the negative Resal effect exerts an unfavorable influence, resulting in an increase in the shear stress experienced by the TCSWs. Moreover, this study introduced a modified shear method that that takes into account the influence of bending moments and the horizontal component of external prestressing. In contrast to basic shear methods, this approach provides notably heightened accuracy.

Mechanism of noise reduction caused by thickening top plate for high-speed railway box-girder bridge

For the high-speed railway concrete box-girder bridge, thickening the top plate can effectively reduce the structural noise radiation caused by moving trains. However, the noise reduction mechanism for thickening top plate has not been investigated. This mechanism is systematically studied in this paper by employing a train-track-bridge spatially coupled dynamics model and an acoustics boundary element model of the box-girder bridge. The results demonstrate that the top plate is the dominant noise source for the concrete box-girder bridge. Thickening top plate can significantly reduce the noise radiation capacity of the box-girder bridge, mainly through three mechanisms: (1) reducing the local modal shapes and vibrations of top plate, (2) decreasing the acoustic radiation efficiency, and (3) redistributing the train-induced vibration in the bridge. Furthermore, these three aspects collectively determine the total amount and spatial distribution of the noise radiation from the box-girder bridge due to moving trains. It is crucial to comprehensively these three aspects for the low-noise design of box-girder bridge.

Assessment and strengthening of post-tensioned concrete box-girder bridges

Post-tensioned concrete box girders have been widely adopted for the construction of medium- to long-span bridges since the mid-20th century. Since the construction of the first such bridges, there has been rapid growth in the volume and weight of heavy vehicles, as well as an increase in exposure to adverse environmental conditions. At the same time, it is estimated that more than 50% of existing bridges in higher-income countries are over half-way through their design life and thus bridge owners are challenged with the management of aging structures. When deterioration in prestressed concrete bridges is identified during inspections, it leads to specific assessments and is usually followed by the need for bespoke strengthening design solutions. In many cases, the challenge in implementing the strengthening resides in maintaining structural capacity to minimise traffic disruption before the works are complete. This article covers the technical and asset management aspects related to the assessment and subsequent strengthening design for post-tensioned concrete box-girder bridges through the lens of case studies on two successful post-tensioned bridge rehabilitations. The strengthening solutions presented have been implemented with minimal disruption to traffic and have had a positive environmental impact by avoiding demolition and full deck reconstruction.

Time-Dependent Reliability Analysis for Deflection of a Reinforced Concrete Box Girder Bridge

Prior to casting of concrete, proper supervision and attention to camber provision in bridge construction are required. It is also critical to use an appropriate quality control manual, pay due attention to reinforcement bar placement, and have a high level of formwork design before construction begins. If these issues are not properly addressed, performance of structures will be affected. In this research, performance of a 40.5m box-girder reinforced concrete bridge which was constructed without having proper camber is studied. As camber was the most important issue of the bridge under investigation, the impact on strength and serviceability requirements is compared to the standard. A dynamic load test with an Arduino type accelerometer is performed to assess the bridge's current condition in relation to the serviceability limit requirement. The deterioration of reinforced concrete (RC) sections due to reinforcement corrosion, creep, and an increase in load intensity, as well as the corresponding statistical distributions are considered to estimate the long-term effect of bridge deflection. The time-variant analysis results show that a linear decrease in deflection reliability indices with the bridge's expected service life of 58 years and strengthening it increased to 85 years.

Time-Domain Finite Element Model Updating for Operational Monitoring and Damage Identification of Bridges

The well-known limitations of modal system identification methods have led to a broad exploration of alternative solutions for operational monitoring and damage diagnosis of structures. This study presents a time-domain Bayesian finite element model updating approach to jointly identify the vehicular loads and finite element modeling parameters of bridges using the vibration data and the location of vehicles traversing the bridge as input. A Bayesian model updating is devised and verified through a series of case studies based on numerically simulated data from a prestressed reinforced concrete box-girder bridge model. Damage states are defined for concrete degradation and delamination, steel corrosion, and loss of prestressing force. Ten different damage scenarios, encompassing the range from minor localized to major distributed damage, are examined. The responses of the damaged bridge are simulated under random traffic scenarios. The acceleration responses, along with the location of the vehicles on the bridge, are used for jointly estimating the model parameters and vehicular loads. The estimated model parameters are then used to infer the location and extent of damage within the bridge. The results show the successful performance of the proposed approach in a numerically simulated environment.

Simplified Evaluation of Shear Stiffness Degradation of Diagonally Cracked Reinforced Concrete Beams.

Shear cracking in concrete box-girder bridges, which could cause excessive deflection during the serviceability limit state, cannot be effectively avoided by code-guided design. While elastic shear deformation only accounts for a small proportion of total deformation for un-cracked reinforced concrete (RC) beams, the magnitude of after-cracking shear deformation becomes comparable to flexural deformation for RC beams. However, there is still a lack of practical models to predict the after-cracking shear deformation of RC beams. First, six thin-webbed I beams were tested to investigate the shear stiffness degradation mechanism and the decrease ratio. Then, a very simple truss strut angle formula, which is the crucial parameter for shear stiffness, was established. Furthermore, a stiffness degradation rule for partially cracked beams was proposed considering the influence of concrete tension stiffening, which is essential for predicting the development process of after-cracking shear deformation. Finally, directly measured shear strains were used to validate the proposed shear stiffness model. The results showed that the shear stiffness drops to about 30~40% of the original stiffness after the first diagonal crack, and the remaining shear stiffness is only about 10% of the original one when the stirrup yields. Increasing the stirrup ratio is a more effective method to control shear stiffness degradation for diagonally cracked RC beams. Also, the proposed shear stiffness model well captures the main features of the shear stiffness degradation, and it provides a relatively accurate prediction of the equivalent shear stiffness at the post-cracking stage.

Analysis of Damage Pattern of Road Bridge Landslide in Mountainous Area

Through on-site defect investigation, special inspection, and finite element simulation calculation of a high-speed upper-span (30 + 32 + 30) m prestressed concrete box girder bridge, the overall sliding force of the bridge on the right side of platform 0# is analyzed. In this situation, typical defects such as overall girder slippage, support dislocation, pier column deviation, and pier bottom side cracks have occurred in the overpass. At the same time, combined with simulation calculation analysis, it is interpreted that the 0# and 1# foundation has been damaged at a certain position below the ground line. The occurrence of broken piles has provided a reliable basis for the later reinforcement and maintenance of the bridge and ideas for emergency inspection and analysis of bridges damaged by the same type of landslides.