Concrete Box Girder Bridge Research Articles

Skew Adjustment Factors for Fragilities of California Box-Girder Bridges Subjected to near-Fault and Far-Field Ground Motions

Past reconnaissance studies revealed that bridges close to active faults are more susceptible to damage and more than 60% of the bridges in California are skewed. To assess the combined effect of near-fault ground motions and skewness, this paper evaluates the seismic vulnerability of skewed concrete box-girder bridges in California subjected to near-fault and far-field ground motions. The relative risk of skewness and fault-location on the bridges is evaluated by developing fragility curves of bridge components and system accounting for the material, geometric, and structural uncertainties. It is noted that the skewness and bridge site close to active faults make bridges more vulnerable, and the existing modification factor in HAZUS cannot capture the variation in the median value of the fragilities appropriately. A new set of fragility adjustment factors for skewness coupled with the effect of fault location is suggested in this paper.

Three‐dimensional nonlinear creep and shrinkage effects of a long‐span prestressed concrete box girder bridge

To analyze the impacts of creep and shrinkage effects on the behaviors of long‐span prestressed concrete box girder bridges, a new nonlinear analysis model of creep and shrinkage effects that comprehensively considered three‐dimensional (3D) characteristics and girder damage evolution was presented. A corresponding numerical analysis method was implemented into the ABAQUS user‐supplied subroutine; this method was verified by comparing the analytical results to the classical experimental results. Finally, a continuous rigid frame bridge with a main span of 220 m was taken as an engineering example, and the analysis results and in situ measured data of long‐term deflection were compared. The results show that the 3D characteristic and the nonlinear property of creep have significant impacts on the prediction of long‐term deflection.

Cumulative vulnerability assessment of highway bridges considering corrosion deterioration and repeated earthquake events

Civil infrastructure systems when located in high seismic zones may experience multiple earthquake events along their service life. Highway bridges that comprise critical elements of the transportation network are often exposed to harsh environments that exacerbate the structural performance to withstand such repeated shocks. While earthquake occurrences are intermittent in nature, environmental degradation mechanisms such as corrosion deterioration continually weakens the structural capacity. Presently there exists a gap in literature that simultaneously considers such temporally varying multi-hazard threats within a probabilistic framework. This study presents a novel methodology that considers repeated main shock sequences and corrosion deterioration for an index-based estimation of cumulative damage along the service life while considering the associated uncertainties with the earthquake occurrence and the deterioration process. A newly introduced analytical strategy in this study enables the updating of bridge pier section properties reflecting deterioration of an already damaged bridge between subsequent earthquake shock events. The proposed framework is demonstrated on a representative case-study multi-span continuous concrete box-girder bridge in California, United States. The results reveal a significant impact of corrosion deterioration on the seismic damage accumulation under multiple earthquakes and underlines the necessity to incorporate aging effects within bridge asset management in high seismic zones.

System identification and model updating of highway bridges using ambient vibration tests

Vibration-based structural health monitoring (SHM) has received significant attention in the past. Due to the existence of some defect of implementation, the measured response of a structure and the response from its finite element model may not match. There are a number of methods available for updating the Finite Element (FE) model of a structure such that the response calculated from the model agrees with field measurements, and identifying the system parameters like stiffness and mass based on dynamic response of the structure. These methods are categorized into physics based and data driven. In this study, the FE models of a 16-span Pre-Stress Concrete Box (PSCB) girder bridge with the total length of 780 m, a 3-span Void Slab Bridge with the total length is of 65 m, and a Steel Box (STB) with 380 m length and 12 m width, with 8 spans of equal length of 47.5 m bridge are constructed and updated using the measured vibration data. The objective of this study is to identify the system properties of the bridges using physics-based and data-driven methods and update the corresponding models using the data from ambient vibration tests and determine the efficacy of each method. A well-known and effective physics-based method, the matrix update method, is used for correlating the models by solving the relevant inverse problem through constrained optimization. In data-driven methods, the Neural Network and Genetic Algorithms are applied to find the correlations between the structural frequencies and changes in the sectional properties of the bridge segments. The outputs of these models are compared with certain target frequencies based on the measured data in order to adjust the section properties of the bridge elements. It is found that while the physics-based method has a better performance than the data-driven model in identifying the modal properties, the physics-based model is difficult to implement and there is a need for developing a hybrid method to achieve a better result.

Three-dimensional reinforcement design method and program realization for prestressed concrete box-girder bridges based on a specific spatial lattice grid model

Reinforcement with prestressed steel tendons to prevent cracking is a major design procedure for most concrete box-girder bridges. They provide acceptable performance even though they do not cover all of the principal stress directions of the structural members because ordinary steel bars also play an important role in resisting external loads. However, with the limitations of current design methods, a plane model is always used as a standard for designers for manual performance of the procedure, but it does not provide sufficient information for the reinforcement of easily overlooked parts from the view of integral three-dimensional effects. Design experiences and detailing requirements must therefore be used extensively, leading to either a waste of materials or a greater likelihood of unexpected damage to members. To address this issue, this study proposes a solution for the reinforcement of prestressed concrete box-girder bridges with a new reinforcement method combined with a specific spatial lattice grid model. The model, which finely differentiates the stress sources of the members and especially emphasizes the in-plane stresses of the top and bottom plates, facilitates the establishment of a stress-based reinforcement method to completely consider the three-dimensional effects of prestressed concrete box-girders and provide the necessary information associated with current bridge codes. The method was implemented as the module of a bridge software with an automatic design function. The effectiveness of the method is demonstrated and discussed via numerical examples.

Probabilistic Seismic Vulnerability Assessment of Tall Horizontally Curved Concrete Bridges in California

The seismic performance of bridge structures is significantly affected by their column height, design era, and horizontal deck curvature. However, existing risk assessment platforms do not appropriately account for the effect of column height and horizontal deck curvature. This paper investigates the effect of column height, design era, and deck curvature on probabilistic seismic demand models and fragilities of bridges. This paper selects a typical configuration of horizontally curved concrete box-girder bridges in California: two-frame five-span bridges with single-column bents. Extensive nonlinear time history analysis results for the bridges including the uncertainties are initially compared using a statistical technique, analysis of covariance. Results from the analysis of covariance are used to estimate the influence of column height, design era, and horizontal deck curvature on bridge performance. An increase in the deck horizontal curvature is found to increase the bridge vulnerability irrespective of the design era and height range. Although the seismic vulnerability of bridges constructed prior to 1970 increases with the increase in the column height, there is no specific trend in the change in vulnerability with respect to column height for bridges constructed after 1970. This research also shows that the implementation of seismic design principles reduces the seismic vulnerability of the bridges.

Sustainable bridge design by metamodel-assisted multi-objective optimization and decision-making under uncertainty

Today, bridge design seeks not only to minimize cost, but also to minimize adverse environmental and social impacts. This multi-criteria decision-making problem is subject to variability of the opinions of stakeholders regarding the importance of criteria for sustainability. As a result, this paper proposes a method for designing and selecting optimally sustainable bridges under the uncertainty of criteria comparison. A Pareto set of solutions is obtained using a metamodel-assisted multi-objective optimization. A new decision-making technique introduces the uncertainty of the decision-maker's preference through triangular distributions and thereby ranks the sustainable bridge designs. The method is illustrated by a case study of a three-span post-tensioned concrete box-girder bridge designed according to the embodied energy, overall safety and corrosion initiation time. In this particular case, 211 efficient solutions are reduced to two preferred solutions which have a probability of being selected of 81.6% and 18.4%. In addition, a sensitivity analysis validates the influence of the uncertainty regarding the decision-making. The approach proposed allows actors involved in the bridge design and decision-making to determine the best sustainable design by finding the probability of a given design being chosen.

Dynamic Analysis & Optimization of Prestressed Concrete Box Girder Bridge Superstructure

Dynamic Analysis & Optimization of Prestressed Concrete Box Girder Bridge Superstructure

Modified Elastic Dynamic Analysis (EDA) for Seismic Demand on In-Span Hinge Shear Keys in Multi-Frame Bridges

Long concrete box-girder bridges are typically constructed in multiple frames that are separated by in-span hinges. Shear keys, located at the in-span hinges, help preserve the transverse integrity of the bridge frames. To date, no reliable method other than nonlinear time history analysis exists to estimate the seismic force demands on in-span shear keys. Methods such as pushover and elastic dynamic analysis (EDA) do not provide accurate estimations. In this study, a rational and reliable analysis method was developed for obtaining the seismic demand on in-span shear keys of multi-frame bridges. A large number of time history analyses were performed on two- to five-frame bridge models with single- and two-column bents that were designed according to California Department of Transportation (Caltrans) Seismic Design Criteria. The results show that high-frequency modes of vibration of the superstructure significantly contribute to the shear key force demands. These modes may also cause transverse yielding in columns. It was established that a modified EDA method may be used to approximate the shear key force demands. In the proposed modified method, the modal forces are reduced separately by the corresponding modal displacement ductility before performing modal combination. This method accounts for the nonlinear response under high-frequency modes of vibration.

Adjustment Factors to Account for the Effect of Bridge Deck Horizontal Curvature on the Seismic Response of Concrete Box-Girder Bridges in California

This research suggests adjustment factors to account for the effect of bridge deck horizontal curvature on the probabilistic seismic demand model (PSDMs) and fragility curves of concrete box-girder bridges in California. For this purpose, typical configurations of horizontally curved bridges in California are selected to create detailed three-dimensional (3-D) probabilistic bridge models with different levels of bridge deck horizontal curvature. Simulation results from the nonlinear time history analysis (NLTHA) of bridges are used to compare the PSDM of individual bridge components using a statistical technique called analysis of covariance (ANCOVA). Comparison results are used to group bridge classes and to suggest adjustment factors. Grouping results indicate that the PSDMs of unseating and bearing displacement are statistically significant for bridges with different levels of deck horizontal curvature. The effect of deck curvature and the use of the modification factors are demonstrated in this paper through the generation of fragility curves.

Concrete Curved Box Girders Interacted with Vehicles in Braking or Acceleration

In this study, an experimentally validated spatial analysis method for the vehicle–bridge interaction system was modified to include the features of vehicle braking and accelerating. The effect of braking or accelerating was considered as external force acting on the vehicular center of gravity and was quasi-statically distributed to every tandem, for which the formulae of load redistribution were derived. The effect of centrifugal force was also incorporated in the model. Based on the modified spatial analysis method, the dynamic responses of a three-span continuous concrete box girder bridge due to vehicle braking and accelerating were studied. Impact factors, including deflection, bending moment, torsional moment and shear force, were examined. The results show that vehicle braking has considerable effect on dynamic responses and the impact factors are related to braking rise time and braking position, but cases of vehicle braking do not always cause larger effects. While the increase in initial speed can produce higher maximum dynamic responses and corresponding impact factors, the dynamic responses in the first span of a multi-span bridge are smaller than those in other spans due to vehicle accelerating.

Flexural response of skew-curved concrete box-girder bridges

The flexural response of the box-girder bridges, having curvature and skewness together referred as skew-curved bridges, cannot be predicted by simply superimposing the individual effect of skewness and curvature due to the coupling of these effects. Moreover, the complexity of such thin-walled box-girder bridges increases under eccentric vehicular loads causing additional torsional and warping stresses in the box-sections. The present study focuses on predicting the flexural response of simply supported single cell skew-curved concrete box-girder bridges. In order to investigate the effect of curvature and skewness, the central curvature angle has been varied from 0° to 48° at an interval of 12° while the skew angle is swept from 0° to 50° at an interval of 10°. Three-dimensional analysis models of the bridges are created using CSiBridge and a finite element analysis has been carried out for gravity loads and Indian Road Congress (IRC) specified Class 70R tracked vehicular Live Load (LL) plying at a minimum specified clearance from the kerb. The parametric study results indicate that the flexural response of the inner girder (web) becomes more pronounced in case of skew-curved bridges. In general, it has been observed that presence of skewness in highly curved bridges significantly improves the flexural response of the bridge. Furthermore, the critical position of LL producing the absolute maximum longitudinal moment as well as the location of the critical section for moment has been found significantly affected by skewness and curvature. These critical positions have been presented in the framework of newly developed ‘skew-curve’ coordinate system for systematic representation.

Numerical and experimental investigation into the mid- and high-frequency vibration behavior of a concrete box girder bridge induced by high-speed trains

Concrete box girder bridges exhibit mid- and high-frequency (> 20 Hz) dynamic responses due to train excitations, which result in problems of noise radiation and track deterioration. This study presents a numerical model for box girder vibration prediction. Significant attention is focused on the mid- and high-frequency responses via introduction of a detailed track/bridge subsystem model. A hammer impact test was used to determine the model parameters. The model was then validated using a homologation test. The results show that the wheel/rail force and box girder mobility are the two principal factors that influence box girder vibration spectral characteristics and amplitudes. The box girder responses at cross-sections with similar dynamic characteristics vary little, as they increase moderately with the train speed. The application of a fastening system with low stiffness and high damping can effectively reduce box girder vibration. However, the elastic modulus and damping of the cement–asphalt mortar, and the thickness of the track slab and bearing base exert the smallest influences on the vibrations. The box girder slab thickness should be designed appropriately because its dynamic behavior is closely associated with the slab characteristics.

Simplified method for the transverse bending analysis of twin celled concrete box girder bridges

Box girder bridges are one of the best options for bridges with span more than 25 m. For the study of these bridges, three-dimensional finite element analysis is the best suited method. However, performing three-dimensional analysis for routine design is difficult as well as time consuming. Also, software used for the three-dimensional analysis are very expensive. Hence designers resort to simplified analysis for predicting longitudinal and transverse bending moments. Among the many analytical methods used to find the transverse bending moments, SFA is the simplest and widely used in design offices. Results from simplified frame analysis can be used for the preliminary analysis of the concrete box girder bridges.From the review of literatures, it is found that majority of the work done using SFA is restricted to the analysis of single cell box girder bridges. Not much work has been done on the analysis multi-cell concrete box girder bridges. In this present study, a double cell concrete box girder bridge is chosen. The bridge is modelled using three- dimensional finite element software and the results are then compared with the simplified frame analysis. The study mainly focuses on establishing correction factors for transverse bending moment values obtained from SFA.

Modeling for Assessment of Long-Term Behavior of Prestressed Concrete Box-Girder Bridges

Large-span prestressed concrete (PC) box-girder bridges suffer excessive vertical deflections and cracking. Recent serviceability failures in China show that the current Chinese standard modeling approach fails to accurately predict long-term deformations of large box-girder bridges. This hinders the efforts of inspectors to conduct satisfactory structural assessments and make decisions on potential repair and strengthening. This study presents a model-updating approach that aims to assess the models used in the current Chinese standard and improve the accuracy of numerical modeling of the long-term behavior of box-girder bridges, calibrated against data obtained from a bridge in service. A three-dimensional finite-element model representing the long-term behavior of box-girder sections is initially established. Parametric studies are then conducted to determine the relevant influencing parameters and to quantify the relationships between those and the behavior of box-girder bridges. Genetic algorithm optimization, based on the response-surface method (RSM), is used to determine realistic creep and shrinkage levels and prestress losses. The modeling results correspond well with the measured historic deflections and the observed cracks. This approach can lead to more accurate bridge assessments, which result in safer strengthening and more economic maintenance plans.

A 5 year track record on a galvanic CP system applied on a light weight concrete bridge with prestressed steel – Developments in time of the effectiveness as determined by depolarisation values and current densities

This paper gives insight in the research and investigations which were undertaken on a post tensioned light-weight concrete box girder bridge in the Netherlands. This project started in the first half of 2013 and measurements are still executed regularly. Due to long-term leakage of a longitudinal joint between 2 parts of the bridge, chlorides had penetrated into the concrete up to the level of the reinforcement and beyond, causing severe corrosion of the steel, spalling of the concrete cover and eventually causing danger for the shipping underneath the bridge due to falling lumps of concrete. To solve this problem, Galvanic Cathodic Protection (GCP) was applied in 2 stages. Firstly, in 2013, zinc based anode strips were applied on the soffit of 2 post tensioned lightweight bridge segments for the purpose of testing and monitoring. After obtaining good results from the test, in 2014/2015 the remaining 29 bridge segments were repaired and protected with the same GCP system as well. This paper reviews subsequent potential decay and current densities measurements, which have provided valuable information on GCP performance and throwing power. The results of anode performance at different locations and depths are reviewed. Concrete resistivity have shown a major influence on the effectiveness of the installed GCP system.

Fatigue behaviour at elevated temperature of RC slabs strengthened with EB CFRP strips

Abstract Reinforced concrete (RC) structures such as concrete box-girder highway bridges may suffer fatigue damage due to cyclic loads. Externally bonded (EB) carbon fibre reinforced polymer (CFRP) strips can be used to increase the fatigue (and static) load bearing capacity of such elements and to increase the service life of the elements. The EB CFRP strips under the asphalt layer can reach elevated temperatures of up to 50 °C during summer when the asphalt is directly exposed to solar radiation. Therefore, in this study, the fatigue behaviour at an elevated temperature of RC slabs strengthened with EB CFRP strips is evaluated. The focus is on the strengthening of lateral cantilevers of deck slabs of concrete box-girder highway bridges. The fatigue behaviour of RC elements is a complex phenomenon that is influenced by many parameters such as the maximum load, stress oscillation level on the longitudinal steel reinforcement, shear span-to-depth ratio, and quality of concrete. This phenomenon becomes even more complicated when elevated temperatures are considered. Majority of the existing experimental works on fatigue behaviour of EB-strengthened RC structures showed that the typical fatigue failure at room temperature is caused by fatigue failure of the longitudinal steel reinforcement followed by strip debonding. In this study, it was investigated if a different type of failure can be observed at elevated temperatures owing to the changes in epoxy properties.

Prestressing force monitoring method for a box girder through distributed long-gauge FBG sensors

Monitoring prestressing forces is essential for prestressed concrete box girder bridges. However, the current monitoring methods used for prestressing force were not applicable for a box girder neither because of the sensor’s setup being constrained or shear lag effect not being properly considered. Through combining with the previous analysis model of shear lag effect in the box girder, this paper proposed an indirect monitoring method for on-site determination of prestressing force in a concrete box girder utilizing the distributed long-gauge fiber Bragg grating sensor. The performance of this method was initially verified using numerical simulation for three different distribution forms of prestressing tendons. Then, an experiment involving two concrete box girders was conducted to study the feasibility of this method under different prestressing levels preliminarily. The results of both numerical simulation and lab experiment validated this method’s practicability in a box girder.

Effect of intermediate diaphragms on the load – carrying capacity of steel – concrete composite box girder bridges

Intermediate diaphragms are used in box girders not only to prevent premature distortion under eccentric loading conditions but also to improve the distribution of live loads. This paper reports an investigation into the effect of intermediate diaphragms on the load - carrying capacity of a Steel – Concrete Composite Box (SCCB) girder bridge with open steel box section. In the current study, a three - dimensional finite element (FE) model of the SCCB girder is developed and analyzed using ABAQUS software. The nonlinear inelastic analysis is invoked in order to accurately capture the actual behavior of the girder. The numerical model is verified with experimental results to ensure the accuracy of the FE modeling method. A parametric analysis is implemented to study the effect of intermediate diaphragms on the load – carrying capacity of an SCCB girder with a 30–60m span length. Based on parametric studies, the number of intermediate diaphragms (N) is recommended for practical design of the girder, which satisfies the requirement stated in the provisions of the AASHTO LRFD standard.

Prestress and excitation force identification in a prestressed concrete box-girder bridge

Prestress force identification (PFI) is crucial to maintain the safety of prestressed concrete bridges. A synergic identification method has been proposed recently by the authors that can determine the PF and the excitation force simultaneously in prestressed concrete beams with good accuracy. In this paper, the ability of this method in the application with prestressed concrete box-girder bridges is demonstrated. A reasonable assumption is made to capture the similarity of the dynamic behavior of the prestressed concrete box-girder bridge and a beam under a certain loading scenario, and the feasibility of this method for application in a prestressed box-girder bridge is affirmed. A comprehensive laboratory test program is conducted, and the effects of PF, excitation, measuring time and uncertainties are studied. Results show that the proposed method can predict the PF and the excitation force in a prestressed concrete box-girder accurately and has a great robustness against uncertainties.