Concrete Continuous Box Girder Bridge Research Articles

Experimental and Modeling Study on Long-Term Deformation of Three-Span Prestressed Concrete Continuous Box-Girder Bridge Model after Cracking

Experimental and Modeling Study on Long-Term Deformation of Three-Span Prestressed Concrete Continuous Box-Girder Bridge Model after Cracking

Temperature gradient estimation of long-span concrete box girders using average conditional exceedance rate function

An accurate assessment of temperature gradients in box girders is crucial for design and maintenance of long-span bridges. Although the current bridge specifications have provided temperature gradient patterns, these existing specifications are insufficient to accurately describe temperature gradients of bridges in service period. In this article, a novel methodology for determining an efficient positive temperature gradient pattern considering condition dependent and whole design service life is proposed. Firstly, statistical analysis and curve fitting are performed by using the long-term temperature data collected through structural health monitoring system, which indicates that temperature gradient patterns can be described as exponential functions. Secondly, the representative values of temperature difference have been estimated using average conditional exceedance rate (ACER) functions, which can use short-term data and consider conditional dependencies to predict long-term extreme values. Finally, the temperature gradient patterns of box girder of bridges in the whole service life have been estimated. Compared with the gradient patterns in current Chinese specification, the proposed temperature gradient pattern demonstrates better applicability in a long-span continuous concrete box-girder bridge. This result is expected to provide a research reference for accurately assessment of temperature gradients in box girders, which is crucial for design and maintenance of long-span bridges.

Research on Monitoring Technology for Frame Piers of Continuous Box-Girder Bridges Constructed by the Cantilever Method

This paper focuses on the analysis of the stress state of a large-span frame pier-continuous box girder bridge with pier crossbeams anchored by pier crossbeams on the main pier of the Guangfo-Zhao Expressway. The bridge is constructed by the cantilever method, and a refined finite element model of the entire bridge is established using the finite element software Midas/FEA to analyze the stress state of the frame pier during the cantilever construction process. It is found that under the possible combined action of an unbalanced load during construction, the torsional resistance of the frame pier crossbeam does not meet the requirements of the design code. In order to eliminate the torsion of the frame piers, counterweights were used to monitor the frame piers during the construction of the box girders. In this paper, the theoretical calculation formula of the inclination angle of the end section of the frame pier crossbeam with the change of unbalanced bending moment, the calculation formula of the relationship between the horizontal displacement of the frame pier and the unbalanced bending moment, and the calculation formula corresponding to the relationship with the water tank counterweight are derived using the structural mechanics method. Two monitoring methods for the frame pier are proposed. In the construction monitoring of the bridge, the numerical fitting formula obtained by finite element numerical analysis calculation is compared with the calculated formula obtained by substituting the design parameters of the frame pier into the theoretical formula. The basic constants in both formulas are basically equal, verifying the correctness of the monitoring calculation formula proposed in this paper for the torsional resistance of the frame pier crossbeam. The applicability of the two monitoring methods is also compared and analyzed. This paper takes the main pier of Chaoyang overpass’s mainline bridge as the engineering background, which adopts the framework pier with a large-span prestressed concrete continuous box girder bridge. It analyzes the torsional state of the beam of the framework pier during the bridge construction process and conducts research on the construction monitoring of the framework pier crossbeam, providing valuable references for the construction monitoring of framework pier crossbeams in the construction of large-span framework pier continuous bridges in the future. The research results of this paper can provide assistance for the construction monitoring of similar projects. This paper’s innovation primarily resides in employing structural mechanics methods to compute the torsion of frame piers. On this basis, a simplified beam torsion calculation formula is proposed to strengthen its practical application in construction monitoring. The findings of this paper can help in the construction monitoring of similar projects.

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.

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.

Temperature-induced response reconstruction method based on DL-AR model and attention mechanism

Data loss is unavoidable for structural health monitoring (SHM) systems due to various potential factors, such as equipment aging, radio interference. Previous studies have revealed that it is more challenging to extract structural state information from incomplete data. Therefore, it is important to develop high-precision response reconstruction methods for missing data. In this study, a hybrid deep-learning and autoregressive model with attention mechanism (DL-AR-ATT) framework is proposed to accurately reconstruct structural responses considering data correlations. The proposed model consists of the deep-learning (DL) and autoregressive (AR) components, which can simultaneously model the linear and nonlinear structure of data. To adaptively weight the contribution of the two components to the final result instead of directly summing, the study introduces a custom weighting layer into DL-AR-ATT. Moreover, the attention mechanism is introduced to eliminate redundant information caused by the data from multiple sensors as input. To verify the validity and feasibility of the proposed method, long-term SHM data from a long-span steel box girder suspension bridge and a prestressed concrete continuous box girder bridge are used. The results show that the reconstruction performance of DL-AR-ATT is superior to that of the one-dimensional convolutional neural network (1D-CNN)-based and hybrid DL and AR (DL-AR) models. Finally, the weights of the modules of DL-AR and DL-AR-ATT are visualized to verify the ability of the model to capture data correlations, and to explain how the attention and custom weighting layers improve the performance of DL-AR-ATT.

Construction monitoring of a long-span prestressed concrete continuous box girder bridge with variable sections

The structural behaviors in each construction stage were monitored and analyzed against the background of a long-span prestressed concrete continuous box girder bridge with spans of 55+100+55 m. At first, the formwork erection elevation and pre-camber of the bridge in each stage, as well as stress values of key cross-sections were determined by simulating the whole construction process using the finite element software. Then, the design parameters were identified and the model was corrected by field data collection and considering various influencing factors, so as to ensure effectiveness of the model. Finally, the formwork erection elevation was adjusted according to the stress and altitude in each construction stage, followed by closure of the bridge. According to field monitoring and adjustment, the measured alignment and stress of the bridge conform to the design and the error meets the requirements of specification, indicating a favorable monitoring effect. The research can provide reference for construction of similar bridges.

Seismic energy demands and optimal intensity measures for continuous concrete box-girder bridges

The quantity of seismic energy absorbed during the earthquake event is an essential factor in assessing the level of damage in the structural system. Implementing an energy-based methodology in earthquake engineering is especially relevant for highway bridges in near-source areas since these types of ground motions have caused severe damage to these bridges in the past few years. This study investigates the distribution of seismic input energy(Ei) and other energy-related demands considering essential components of the bridges. Moreover, the optimal IM candidates for establishing probabilistic seismic demand modeling (PSDMs) for energy-related demands were examined. Three bridge models were considered and analyzed, subjected to 328 ground motions using the OpenSees framework. Also, 24 IMs and 14 energy-related demands were utilized. In order to investigate optimal IMs for energy-related demands, indicators, namely efficiency, practicality, proficiency, sufficiency, and relative sufficiency were evaluated, and potentially optimal candidates were identified. Results indicated a notable correlation between energy-based and conventional displacement-based demands. Furthermore, the significant role of column hysteretic energy (Eh column) in the dissipation of the seismic input energy was observed. Finally, the results indicated that velocity spectrum intensity related to horizontal ground motion (VSIH) is the optimal IM for the selected demands, i.e., column hysteretic (Ehcolumn), maximum kinetic (Max Ek), and summation of hysteretic (ΣEh) energies.

Numerical Analysis on Transverse Splicing Structure for the Widening of a Long Multi-Span Highway Concrete Continuous Box Girder Bridge

For the bridge widening of long multi-span highway concrete continuous box girder with a conventional splicing structure, due to the large longitudinal difference deformation by concrete shrinkage and creep between the existing and new ones, the widened structure will have an overlarge bending deformation after widening, especially an obvious transverse deformation at the end of girder, which will lead to structural damage to the newly widened structure. To effectively absorb the difference deformation mentioned above, this study proposes a novel transverse splicing structure based on the folding effect of a corrugated steel plate (CSP) (hereinafter referred to as “the CSP splicing structure”). Then, a finite element structural analysis was performed on the mechanical properties of the widened structure with the CSP splicing structure, and compared to those of a widened structure adopting the conventional concrete splicing mode, to clarify the transverse load transferring mechanism of the structure. Finally, by conducting a sensitivity analysis on CSP thickness, corrugation length, splicing stitch width, and other structural parameters, a sound parameter combination scheme was put forward. According to the research results, to ensure effective utilization of the CSP folding effect, the corrugation pattern direction of CSP should be set as horizontal, and the wave angle as the degree of 90°. In addition, it mitigated the transverse tensile stress to effectively avoid concrete cracking feasibility on the top flange of the box girder at the end of the girder. This study offers a feasible way of avoiding the structural damage produced by an excess transverse deformation at the end of the girder after bridge widening of a long multi-span concrete continuous box girder.

Rectification of a Slanted Box-Girder Bridge Caused by Unbalanced Soil Load

Aims: Rectification of a slanted continuous concrete box-girder bridge is presented in this paper. Background: Several bridge piers slanted due to uneven ground settlement, inducing excessive width of some expansion joints and oversize sliding displacement of some bridge bearings. The uneven ground settlement occured due to the unbalanced soil load on the ground. Methods: In this project, reverse ground loading was first applied to produce opposite-direction deformation of the bending bridge piles, thereby rectifying the slanted bridge piers rigidly connected to the piles. The procedure was accelerated by constructing several stress release holes on the opposite side of the reverse ground loading. Results: To stabilize foundation and prevent landsides of riverbank, combimationn of jet grouting piles and deep mixed piles was apliied to reinforce foundation soil, providing lateral restraint on the bridge piles as well. Finally, a hydraulic power system was used to reset the bridge piers, girders, and expansion joints. A similar system and additional equipment were used to replace the damaged bridge bearings. Conclusion: The recommended rectification techniques are suitable for rectifying bridges with similar geotechnical conditions and structure types and for replacing damaged bridge bearings.

Research of construction monitoring technology of large-span variable cross-section prestressed concrete continuous box-girder bridge

With the advancing development of structural performance and construction techniques, continuous concrete box girder bridges have been widely used due to their advantages including their broad applications, good appearance, and reliable structural safety. However, as the bridge span and its construction demands are increasing, the bridge construction process tends to be more complex. Especially, the construction methods and bridge installation sequences of cantilever bridges not only exert structural internal force on the bridge construction process but also affect the internal force and line shape of the bridge structure of finally constructed bridges. Hence, it is essential to realize bridge construction control. Only in the presence of the excellent construction control performance, can the structural safety in the bridge construction process can be ensured while meeting the designed requirements of bridge line shapes and internal forces of constructed bridges. In this research, by taking the Weihe grand bridge located at Shandong Province, China as construction background, the specific targets and methods of bridge construction control were introduced for the reference of bridge construction and research.

Internal Forces Analysis of Prestressed Concrete Box Girder Bridge by Using Structural Stressing State Theory.

This paper analyzes the working behavior characteristics of a prestressed concrete transverse large cantilever continuous (PCTLCC) box girder bridge model based on structural stressing state theory and the numerical shape function (NSF) method. At first, the normalized generalized strain energy density (GSED) is established to model the stressing state of the bridge model. Subsequently, the Mann Kendall (M–K) criterion is applied to detect three characteristic loads, respectively, elastic–plastic branch load P (200 kN), failure load Q (300 kN), and progressive failure load H (340 kN), and the failure load Q is found to be the starting load of the damage process of the bridge model, rather than the ultimate load where the structure has been destroyed. Finally, the NSF method is adopted to interpolate the test data, and a detailed analysis for the variation characteristics of the working behavior of the bridge model under loads is performed based on the interpolation results. The characteristic load detection method and experimental data extension method for PCTLCC box girder bridge established in this study can provide valuable references for the design and analysis of such bridges.

Temperature Effect on Main Girder of Strengthened Dongming Huanghe River Highway Bridge in Service

The main girder of Dongming Huanghe River Highway Bridge was the first prestressed concrete (PC) continuous box girder bridge strengthened by a cable-stayed system in China. In order to study the temperature effect of the main girder structure of Dongming Huanghe River Highway Bridge after reinforcement, based on the measured data of middle span deflection, key section strain and typical crack width, the curve equations of strain and temperature of main girder were obtained by the regression analysis method. The results show that the annual strain value of main girder changed with the acquisition time in a sinusoidal function, and was linearly related to the temperature. The variation of mid-span deflection decreased gradually from side span to middle span, and varied dynamically with temperature in the whole girder, which also has obvious correlation with temperature. The crack width fluctuated up and down in a certain numerical range, which belonged to respiratory cracks and had equally correlation with temperature.

Risk-Based Multiobjective Optimal Seismic Design for RC Piers Using the Response Surface Method and NSGA-II

In this paper, a risk-based multiobjective optimal seismic design method for reinforced concrete (RC) piers is proposed. This method is used to determine the size and reinforcement ratios of piers to minimize the seismic risk of bridge systems and the construction cost of piers. The Pacific Earthquake Engineering Research- (PEER-) based probabilistic seismic risk assessment approach and the response surface method (RSM) are adopted to develop the seismic risk response surface model, which represents the relationship between the design parameters of piers and the seismic risk of bridge systems. The Pareto optimal solutions of piers are determined by applying an improved version of the nondominated sorting genetic algorithm (NSGA-II). As a case study, the proposed optimal seismic design method is applied to a continuous concrete box girder bridge. The optimal design schemes of piers according to two strategies are determined from the Pareto optimal solutions. The results show that the seismic risk response surface model can be used to accurately describe the relationship between the design parameters of piers and the seismic risk of bridge systems. The case study demonstrates the effectiveness of the proposed optimal seismic design method. The analysis of the Pareto optimal solutions allows designers to more rationally conduct the seismic design of piers.

Developing a multi-variable vulnerability function for a class of multi-span continuous concrete box-girder highway bridges with emphasis on near-field earthquakes

The most common tools in seismic performance assessment of highway bridges are single-variable fragility curves. However, fragility curves are not confidently reliable due to utilizing only a single intensity measure (IM). Alternatively, single- and multi-variable vulnerability functions, of which the latter is scarce and rather complex, have been proposed for that purpose, yet without considering the effects of the strong vertical component of near-field earthquakes. This study aimed to develop a multi-variable vulnerability function for multi-span continuous concrete box-girder bridges, accentuating near-field earthquakes. Ten bridge models corresponding to the 1971-1990 design era were considered and analyzed, subjected to three-component records of 164 earthquakes using OpenSees framework. First, 28 IMs related to horizontal and vertical ground motions, and 12 engineering demand parameters were utilized, and a set of potentially optimal IMs were determined through optimality investigation. Then, to ensure that identified IMs are authentically optimal candidates, Lasso regression was employed, introducing 12 IMs as optimal. Finally, Step-wise regressions were conducted to reduce the complexity of the proposed equation. Results revealed peak ground acceleration, peak ground velocity, and velocity spectrum intensity of the horizontal component of ground motion, and acceleration spectrum intensities of both horizontal and vertical components as optimal ones.

A Mahalanobis Distance Cumulant-Based Structural Damage Identification Method with IMFs and Fitting Residual of SHM Measurements

Data-driven damage identification based on measurements of the structural health monitoring (SHM) system is a hot issue. In this study, based on the intrinsic mode functions (IMFs) decomposed by the empirical mode decomposition (EMD) method and the trend term fitting residual of measured data, a structural damage identification method based on Mahalanobis distance cumulant (MDC) was proposed. The damage feature vector is composed of the squared MDC values and is calculated by the segmentation data set. It makes the changes of monitoring points caused by damage accumulate as “amplification effect,” so as to obtain more damage information. The calculation method of the damage feature vector and the damage identification procedure were given. A mass-spring system with four mass points and four springs was used to simulate the damage cases. The results showed that the damage feature vector MDC can effectively identify the occurrence and location of the damage. The dynamic measurements of a prestress concrete continuous box-girder bridge were used for decomposing into IMFs and the trend term by the EMD method and the recursive algorithm autoregressive-moving average with the exogenous inputs (RARMX) method, which were used for fitting the trend term and to obtain the fitting residual. By using the first n-order IMFs and the fitting residual as the clusters for damage identification, the effectiveness of the method is also shown.

Static Strength of Friction-Type High-Strength Bolted T-Stub Connections under Shear and Compression

The friction-type high-strength bolted (FHSB) T-stub connection has been widely used in steel structures, due to their good fatigue resistance and ease of installation. While the current studies on FHSB T-stub connections mainly focus on the structural behaviors under both shear and tensile force, no research has been reported on the mechanical responses of the connections under the combined effects of shear and compression. To make up for this gap, this paper presents a novel FHSB T-stub connection, which is simple in structure, definite in load condition, and easy to construct. Static load tests were carried out on 21 specimens under different shear–compression ratios, and the finite-element (FE) models were created for each specimen. The failure modes, initial friction loads and ultimate strengths of the specimens were compared in details. Then, 144 FE models were adopted to analyze the effects of the friction coefficient, shear–compression ratio, bolt diameter and clamping force on the initial friction load and ultimate strength. The results showed that the FHSB T-stub connection under shear and compression mainly suffers from bolt shearing failure. The load–displacement curve generally covers the elastic, yield, hardening and failure stage. If the shear–compression ratio is small and the friction coefficient is large, its curve only contains the elastic and failure stage. The friction coefficient and shear–compression ratio have great impacts on the initial friction load and ultimate strength. For every 1 mm increase in bolt diameter, the initial friction load increased by about 10%, while the ultimate strength increased by about 8.5%. For each 10% increase/decrease of the design clamping force, the initial friction load decreases/increases by 7.8%, while the ultimate load remains basically the same. The proposed formula of shear capacity and self-lock angles of FHSB T-stub connection can be applied to the design of CSS-enhanced prestressed concrete continuous box girder bridges (PSC-CBGBs) and diagonal bracing.

Tensioning-Phase Box Girder Deformation Prediction Model Based on Ant Colony Algorithm and Residual Correction

The girder of prestressed concrete continuous box girder bridge strengthened by a stay cable system has a very complex deformation mechanism, and it is difficult to establish accurate numerical model for prediction. For these problems, a prediction method based on the combination of ant colony algorithm and residual combination correction model is proposed. In this method, the measuring points are considered as the cities in TSP ant colony algorithm, the information function model and heuristic function model are constructed, the pheromone update mechanism and ant search mechanism are established, and the deformation prediction of the main girder based on ant colony algorithm prediction model is achieved. On this basis, in order to fit the random change process of main girder deflection better, the periodic function generated by harmonic transform and sine function are introduced to modify the predicted results, which makes up for the low precision defect of single model. The results show that compared with finite element method, unequal interval gray model (1,1) (UIGM (1,1)), one-time residual correction UIGM (1,1), Markov chain residual correction UIGM (1,1), and ant colony algorithm model, this model can reflect the space-time effect and casual fluctuation feature of the development of girder deformation better and also has higher prediction accuracy and efficiency. The mean relative error of the predictive value is 3.39%, the posterior error ratio is 0.060, and the accuracy level reaches level 1. This model provides a new way for the girder deformation prediction of bridge strengthened by the stay cable system.

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.

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.