Concrete Continuous Bridge Research Articles

Prestressed concrete continuous bridge girders: comparison of the Chinese and Southern African codes

To provide a reference for designers, taking a 30 m + 40 m + 30 m prestressed concrete continuous beam bridge as an example, this paper compares the differences between Chinese Codes and Southern African Codes in terms of load effect, prestressing requirements and design safety. The results show that the actual number of prestressed strands required by the Southern African Code in the mid-span section is 11.63 %-12.50 % larger than that required by the Chinese Code. The actual number of prestressed strands required by the Southern African Code in the fulcrum section is 16.33 %-30.00 % lower than that required by the Chinese Code. The safety margin factor of the section designed by the Southern African Code is higher than that of the Chinese Code, and has a higher safety reserve.

A Failure Analysis of the Long-Term Overturning Stability of Concrete Continuous Single-Column Pier Bridges Considering Creep and Overloaded Vehicles

Several single-column pier girder bridges have been involved in overturning accidents, resulting in significant economic losses and casualties, thus necessitating a risk assessment of the overturning stability. To date, the effect of structural degradation due to concrete creep on the long-term stability of bridges has not been demonstrated. In this study, a full-scale nonlinear analysis of the lateral overturning process of a collapsed concrete box girder based on the explicit dynamic finite element method (EFEM) was conducted to verify the reliability of the numerical method. An EFEM model incorporating concrete creep was developed to demonstrate the effect of structural degradation on the long-term stability of bridges. The synthesis overturning axis method (SOAM) was proposed to evaluate the long-term overturning stability of concrete continuous bridges, aiming to address the deficiencies in existing methods, particularly for curved bridges, and was compared with conventional methods. The results show that the variations in bearing reaction forces between curved and straight bridges under creep and self-weight are minimal, staying within 2%. An increase in the creep terminal coefficient results in the opposite trend in the ultimate vehicle weight of curved bridges and straight bridges, but fluctuations remain within 2%, indicating that long-term creep has a limited effect on the overall overturning stability. A failure analysis of 20 single-column pier bridges reveals significant differences in the ultimate vehicle weight between the rigid overturning axis method (ROAM) and folded overturning axis method (FOAM), with error ranges of −14.2% to 567.4% and −99.1% to −32.1%, respectively. The SOAM results have the smallest error range compared to those of the EFEM, with an error range of −38.8% to 33.9%. Despite these errors, the SOAM demonstrates a significant improvement in characterizing the trend and assessment accuracy of the overall overturning stability of single-column pier bridges.

An EGO-based online model updating method for hybrid simulation

Hybrid simulation combines experimentally testing of physical substructures with computational simulation of numerical substructures to replicate structural responses under earthquakes. When numerical substructure involves parts that are similar to physical substructure, measured responses of physical substructure are often used to update similar parts within numerical substructure, aiming to improve accuracy of seismic assessment. This study proposes an efficient global optimization based approach for online model updating in hybrid simulation (HSMU-EGO) involving multiple key components yet with only one physically tested in laboratory. Kriging meta-model is constructed for the response error between the numerical model for updating and the experimental substructure, while efficient global optimization and optimal Latin hypercube design are integrated for parameter estimation to minimize the response error. Computational simulations are conducted for a simple steel braced frame and a complex concrete continuous bridge to comprehensively evaluate the performance of HSMU-EGO in the presence of constitutive parameter and model errors. The proposed method is demonstrated to effectively and efficiently improve the accuracy of hybrid simulation in almost all cases. Compared with Unscented Kalman Filter (UKF), this proposed HSMU-EGO provides more suitable alternative when prior information is limited for the physical substructure.

Preliminary Study on the Damping Effect of a Rotational Inertia Particle Damper Considering the Explosion Response of Continuous Concrete Bridges

Preliminary Study on the Damping Effect of a Rotational Inertia Particle Damper Considering the Explosion Response of Continuous Concrete Bridges

Topology Optimization of Continuous Precast Prestressed Concrete Bridge Girders Using Shape Memory Alloys

Despite the growing interest in the concept of topology optimization, its acceptance in civil structures, especially in prestressed concrete structures, is still faced with practical obstacles primarily due to the geometric complexities of optimized structures. Quite often, complex concrete topology yields a complex distribution of tensile zones, which are hard to be effectively prestressed with continuous steel reinforcement. Shape memory alloys (SMAs), with their ability to apply localized prestressing force only at target tensile regions, can offer solutions to the issues facing conventional prestressing steel reinforcement in topology-optimized concrete structures. This paper investigates the topology optimization of prestressed concrete bridge girders using locally prestressed SMAs. A prototype continuous concrete bridge is selected to be optimized under the AASHTO loading conditions. To prove the feasibility of the optimized design, a detailed 3D finite element analysis is performed. The performance of the optimized girder is compared with that of two commonly used conventional designs. The results show that the optimized design can effectively satisfy the AASHTO limit state with less material than the conventional cases.

Intelligent safety assessment method for demolition construction of closure segment of long-span continuous rigid frame bridges

In order to clarify the risk of demolition construction of large-span continuous rigid structure bridge and put forward an intelligent safety assessment method to ensure the safety of demolition construction of the closure segment. Taking a concrete continuous rigid bridge as an example, this paper uses the combination of finite element analysis, theoretical calculation and actual measurement verification to study the influencing parameters and construction safety assessment methods of the long-span continuous rigid bridge in the demolition construction stage of the closure segment. The results show that the parameters that have a great influence on the stress state of box girder and pier during the demolition stage of the closure segment are mainly the self-weight of the structure, tendon prestress state and construction temperature difference. Through the influence envelope analysis of each parameter, it is clear that the ultimate failure mode caused by the most unfavorable parameter combination in the demolition stage of the closure segment is the crushing of the bottom plate of the box girder in the middle span, and the cracking of the piers on the side span at the top and the variable section. In order to further accurately evaluate the construction safety in the demolition stage of the closure segment, based on the long-term down-warping state inversion analysis of the box girder, the identification method of cross-section damage and prestress loss of the box girder and the calculation results of engineering examples are given. Finally, a safety assessment method of the most unfavorable section based on the principle of influence matrix is proposed. Through the analysis of an example, the safety of the closure segment demolition construction is clarified, and the correctness of the analysis is verified by intelligent monitoring means.

Turning Telecommunication Fiber-Optic Cables into Distributed Acoustic Sensors for Vibration-Based Bridge Health Monitoring

We introduce a nondedicated bridge health monitoring (BHM) system that turns pre-existing telecommunication fiber-optic cables into distributed acoustic sensors to collect bridge dynamic strain responses. Due to extensively installed telecommunication fiber cables in the cities, our telecommunication cable-based system enables efficient and low-cost BHM without the requirement of on-site sensor installation and maintenance; however, it is challenging to extract bridge damage-sensitive information (e.g., natural frequencies and mode shapes) from this nondedicated strain data as it has large measurement noise and error propagation. To overcome the challenge, we develop a physics-guided system identification method that models strain mode shapes based on physics-guided parametric mode shape functions derived from bridge dynamics. We then estimate the displacement mode shape function by analytically double-integrating the modeled strain mode shape. Our method improves the accuracy of estimating bridge damage-sensitive features and reduces error propagation by constraining strain and displacement mode shapes with bridge dynamics. We evaluated our system on a concrete continuous three-span bridge in San Jose, California. Our system successfully identified the first three natural frequencies and reconstructed strain and displacement mode shapes in a meter-scale resolution.

Structural and Operational Safety Evaluation of a Long-Span Continuous Beam Bridge with an Excessive Deflection in Urban Rail Transit

Prestressed concrete continuous beam bridges often experience increasing deflection during operation, affecting service performance. However, the evaluation method of continuous beam bridges with an excessive deflection in urban rail transit still needs to be improved. This paper carried out a structural and operational safety evaluation of a long-span continuous beam bridge with an excessive deflection in urban rail transit. Long-term deformation monitoring, static load tests, and natural frequency tests were conducted to evaluate the structural property development and response under the train loading. Based on the field data, a train–track–bridge coupled numerical model was established and calibrated to analyze the dynamic deflection, acceleration of the bridge, train safety, and comfort indexes. Subsequently, the deflection limits and maintenance schedule were discussed. The results show that the bridge exhibited a deformation curve with a large midspan deflection and a slight side-span camber. The cumulative static deflection of the midspan was 50.4 mm since the beginning of long-term deformation monitoring. The increasing deflection led to the gradual reduction of elasticity recovery capacity (ERC), but ERC remained at a high level and there was no significant attenuation of the structural stiffness. The evaluation methods proposed in this paper can provide useful references for the management of similar long-span continuous beam bridges in urban rail transit.

Asymmetric Cantilever Construction Control of a U-Shaped Box Concrete Continuous Bridge in Complex Environment

The bridge of Shanghai Metro Line 10 over Metro Line 6 is a U-shaped concrete single-box double-cell concrete box beam continuous bridge. A novel method is applied to construct the asymmetric cantilever prefabricated and assembled continuous bridge due to the limited construction space and the complex environment. Four mechanical state control methods are applied during the T-shape structure construction process: tensioning pre-stressed steel strand, jacking by the axial force servo system, adjusting the leg reaction force, and setting the auxiliary leg. Auxiliary measures such as the compressive column, side-span counterweight, and temporary pre-stressing are also taken into consideration. The finite element method simulations are performed to measure effects of the four control methods during the construction process. The front leg force of the bridge erection machine and the deflection of the bridge are then monitored. It was deduced that the simulated and measured values of the cantilever T-shape structure are controlled within the limit range during the construction process.

The Train-Bridge Coupled Vibration Analysis of a Long-Span Prestressed Concrete Continuous Beam Bridge under Creep Deformation Effect

The track smoothness of high-speed railroads is severely limited to ensure train performance. The concrete continuous girder bridge is deformed to influence the smoothness of the bridge decks and track caused by creep bulge. There is a need to research the impact of beam creep on the dynamical response of bridge and train operation safety. This paper used Midas software to calculate the long-term deformation of large-span prestressed concrete continuous beam bridges under concrete creep and shrinkage. The train-bridge coupled system was established by adopting self-programming software. Thereafter, the large-term deformation results of the main girder are considered as track irregularity input into the vibration equation of the train-bridge system. The safety of the train operation was evaluated by calculating the dynamic response of the bridge and analyzing the criteria of train running safety. It was shown that the indicators of the large-span bridge are within the allowable code values under all working conditions. The bridge deformation under creep has an impact on the displacement and acceleration response of the bridge when a high-speed train passes through. There is no noticeable impact of creep deformation on the operational performance of trains. Nevertheless, the criteria for assessing the safety of trains’ operation, such as derailment factor, wheel load differences, lateral wheel forces, and vehicle acceleration, have been increased.

Simplified method for estimating restraint moment induced by vertical temperature gradient in continuous prestressed concrete bridges and verification using AASHTO BDS

Diurnal and seasonal temperature variations cause uniform temperature changes, vertical temperature gradients, and horizontal temperature gradients. Vertical temperature gradients occur when the bridge deck absorbs heat due to solar radiation more than the bottom parts of bridge girders. Consequently, the vertical temperature gradient causes redistribution of bearing reactions, and induces additional flexural stresses in continuous spans. Estimating the vertical temperature gradient effect on continuous concrete bridges requires knowledge of thermal analysis of statically indeterminate structures or advanced three-dimensional (3 D) finite element (FE) analysis. Therefore, this article focuses on developing a simplified analysis method for estimating vertical temperature variations effects on continuous prestressed concrete bridge girders, which is required for bridge design. Restraint moments induced by vertical temperature gradients are investigated using 3 D FE analysis. A total of 115 bridges with different configurations (number of spans, girder spacing, and girder type) were analyzed to estimate the positive thermal moments at support locations. Results from these analyses were then used to develop simplified equations for estimating the positive restraint moments due to vertical temperature gradients from AASHTO LRFD Bridge Design Specifications (BDS). The developed equations are validated using John James Audubon Bridge #2 field data, and for other AASHTO LRFD temperature zones.

Continuous monitoring of in-service performance of prestressed concrete continuous bridges with two strengthening measures

The strengthening measures without traffic interruption have been widely used for maintenance and renovation of bridges with damage and stiffness degeneration, due to their advantages of convenience and insignificant influence on traffic. However, evaluation of the associated reinforcement effect and service performance is intractable, because on site load capacity tests could not be conducted. In this study, a continuous monitoring method was proposed to evaluate the enhancement effect of the prestressed concrete continuous bridge with two different strengthening measures, by using the measurement data under operation status. First, the Ensemble Empirical Mode Decomposition (EEMD) method was used to distinguish the thermal effect and traffic induced effect. Then, cross-correlation and linear regression analysis was conducted to investigate the relevance of monitored temperature data and extracted thermal effect. Next, the t location-scale distribution was used for probabilistic statistical analysis of the peak values of traffic induced bridge responses. The generalized Pareto distribution (GPD) model and finite element model were used to set the two-level threshold of the bridges. The statistical results of the monitored data with different strengthening measures were compared to evaluate the associated reinforcement efficiency. The results demonstrated that the proposed continuous method performs well in assessment of bridge reinforcement and service performance with no traffic disruption.

Effect of Non-Uniform Vertical Excitations on Vertical Pounding Phenomenon in Continuous-Deck Curved Box Girder RC Bridges Subjected to Near-Source Earthquakes

ABSTRACT The geometry of skewed and curved bridges can cause complexity of their dynamic response and difficulty of analysis against earthquakes. In addition, when vibration occurs in the curved bridges, due to their specific geometry, the vertical, flexural, and torsional vibrations of the deck are coupled. The present study was carried out aiming to investigate the effect of non-uniform vertical excitation of the bridge piers with various vertical/horizontal acceleration ratio (V/H) on the pounding phenomenon in concrete curved bridges subjected to near-source earthquakes. For this purpose, the analytical method was employed using the expansion of the functions of structural dynamics on a two-span continuous concrete bridge model, consisting of continuous flexural/torsional beam elements for the deck, springs for the rubber bearings, and rods as the bridge piers. The non-uniform vertical excitations of the piers were induced to the whole system by the harmonic functions in the form of transient wave transfer functions, and then the equations of the entire system were solved using the Eigen functions. The induced waves can cause separation of the box girder deck from the rubber bearing along with the vertical and horizontal displacement as well as the torsion of the box girder around the longitudinal axis of the bridge. After each separation, the deck returns back and hit the rubber bearing, resulting in a vertical pounding force on the bearing and the pier. The analyses results show that when the curved beam is subjected to a non-uniform vertical excitation with a various V/H, the lateral displacement of the deck are up to 21% larger than when the bridge is excited by considering a value of V/H = 2/3. The results also show when the excitation frequencies are different in different piers of the bridge, the pounding force can be increased up to three times, for some specific curvature angle, comparing to the case of equal excitation frequency in all piers.

Calculation method steel reinforced concrete continuous bridge spans with two reinforced concrete slabs on the effect of concrete shrinkage

The article is considered calculation method steel reinforced concrete continuous bridge spans with two reinforced concrete slabs on the effect of concrete shrinkage. For long-term processes that must be considered when calculating the span structures of bridges, besides creep, concrete shrinkage applies. Object of study: composite steel and concrete span beam bridge with two reinforced concrete slabs. Purpose: to develop a calculation method the cross section steel reinforced concrete bridges with two reinforced concrete slabs on the effect of concrete shrinkage considering concrete creep. Continuous spans of steel reinforced concrete bridges with two reinforced concrete slabs over intermediate supports much more economically, in terms of metal consumption, compared to steel reinforced concrete bridges with one concrete slab. Cross section of a reinforced reinforced concrete beam consists of a steel part that combined with two reinforced concrete slabs. The article presents the results of the calculation of continuous steel-concrete superstructure of a road bridge with two reinforced concrete slabs by the above method.

Seismic Fragility Analysis of the Reinforced Concrete Continuous Bridge Piers Based on Machine Learning and Symbolic Regression Fusion Algorithms

In the fragility analysis, researchers mostly chose and constructed seismic intensity measures (IMs) according to past experience and personal preference, resulting in large dispersion between the sample of engineering demand parameter (EDP) and the regression function with IM as the independent variable. This problem needs to be solved urgently. Firstly, the existing 46 types of ground motion intensity measures were taken as a candidate set, and the composite intensity measures (IMs) based on machine learning methods were selected and constructed. Secondly, the modified Park–Ang damage index was taken as EDP, and the symbolic regression method was used to fit the functional relationship between the composite intensity measures (CIMs) and EDP. Finally, the probabilistic seismic demand analysis (PSDA) and seismic fragility analysis were performed by the cloud‐stripe method. Taking the pier of a three‐span continuous reinforced concrete hollow slab bridge as an example, a nonlinear finite element model was established for vulnerability analysis. And the composite IM was compared with the linear composite IM constructed by Kiani, Lu Dagang, and Liu Tingting. The functions of them were compared. The analysis results indicated that the standard deviation of the composite IM fragility curve proposed in this paper is 60% to 70% smaller than the other composite indicators which verified the efficiency, practicality, proficiency, and sufficiency of the proposed machine learning and symbolic regression fusion algorithms in constructing composite IMs.

Structural behavior of CFST arch foots under pumping pressure of concrete infills

Prestressed concrete (PC) continuous girder-arch composite bridges, using concrete filled steel tubes (CFST) as the arch ribs to support the PC main girder, have gained their popularity in recently constructed large span bridges. The adoption of CFSTs brings many advantages, such as the concrete infill help to prevent the occurrence of local buckling in steel tubes, while the steel tubes can serve as framework for concrete core and strengthen the encased concrete. In order to achieve the above merits, the arch foots connecting the CFST arch ribs and PC girder are supposed to have sufficient strength and stiffness. However, the extensive use of CFST arch ribs showed that concrete cracking are commonly found at the arch foots. This paper studied the structural behavior of arch foot by employing a comprehensive numerical model. The influence of pumping pressure from concrete infill at construction stage on local stress of the arch foots was presented and discussed. The results indicated that the radial stress produced by pumping pressure at the joint zone squeezed the concrete around the arch foots, which resulted in significant hoop tensile stresses in the surrounding concrete. The outcomes of this study can provide technical support to improve the construction quality and structure stability, and optimize the construction procedures for this type of bridges.

Experimental Study on Seismic Performance of Concrete Continuous Bridge with HDR Bearings

Several earthquakes have shown that concrete continuous bridges suffer from major damage and permanent deformations. This paper investigates the use of high damping rubber (HDR) bearings to improve seismic performance of concrete continuous bridge. The shaking table array test of a two-span isolated continuous bridge specimen with 1:3 scale was carried out to study the seismic response characteristics of the continuous bridge with HDR bearing isolation. The experimental results were compared with the seismic response of non-isolated continuous girder bridge specimen. The results indicated that the seismic response of continuous girder bridge varied with input ground motion, direction and PGA. In terms of HDR bearing isolation system, there was time lag between seismic responses of the upper and lower structures, and the acceleration of the side pier was larger than that of the middle pier while displacement response has better symmetry than non-isolated specimen. The effect of vibration isolation varied with shaking frequency, intensity and direction. The seismic damage was mainly concentrated in the bottom of the middle pier column and the middle bearing. The horizontal shear capability model of the HDR bearing is proposed as the bilinear restoring force model. The numerical analysis model of the bridge specimen established on the simplified bearing model can reflect the damping effect of the HDR bearing on the concrete continuous bridge.

Fragility Assessment of Bridges Considering Cumulative Damage Caused by Seismic Loading

In this paper, an approach is proposed to obtain fragility curves of reinforced concrete structures which can accumulate damage due to inelastic behavior when they are exposed to seismic load sequences in a given instant of time. The cumulative damage caused by earthquakes is quantified considering the maximum drift. This study is mainly focused on the stochastic uncertainty and variability of seismic occurrence, which are considered the main sources that can influence the performance of the structural system. The approach is validated with the help of a numerical study using a reinforced concrete continuous bridge considering the effect of cumulative damage given by seismic sequences for different time instants of 0, 50, 100, 150 and 200 years, after bridge construction. The bridge is located in the transition part of the soil in Mexico City. Different drift thresholds are studied to evaluate the probability of being exceeded. The proposed approach demonstrates the importance of considering the effect of cumulative damage under seismic sequences. In addition, it is assumed that it could be possible to design bridge structures that develop a certain pre-established drift threshold.

Considering the Dynamic Response of Transverse and vertical Vehicle-bridge Coupled Curved Bridge

In order to explore the dynamic response of curved bridge under the coupling action of transverse and vertical vehicle-bridge, a three-span concrete continuous curve bridge model and a vehicle model are established by using the finite element software ANSYS. The coupling action of transverse and vertical vehicle-bridge is simulated by using the equilibrium and geometric coordination conditions of the forces between the two models, and the transversevibration of the vehicle model is considered. The dynamic response of curved bridge is studied by establishing the dynamic model of vehicle-bridge interaction. The results show that the maximum transverse force of 1# mid-span section increases by 1.43% under the action of 70t vehicle weight compared with that without considering the coupling effect of transverse and vertical vehicle-bridge; and the maximum transverse displacement of 1# mid-span section increases by 10.25% compared with that without considering the coupling effect of transverse and vertical vehicle-bridge. Therefore, it is necessary to take into account the vehicle-bridge coupling in the dynamic response analysis of curved bridges; the transverse displacement of curved bridges can be prevented by limiting load and weight.

Data Fusion Technique for Bridge Safety Assessment

Abstract This article proposes a multilevel assessment system tailored to the health condition evaluation of prestressed continuous concrete bridges. The main structure of the assessment system is divided into a prior database and data processing unit. Some of the factors mainly influencing bridge safety, including carbonation, freeze-thaw cycles, steel corrosion, overloading, and temperature, are utilized to form various load cases as a basis for the prior database. To evaluate the bridge safety conditions comprehensively and scientifically, artificial intelligence methods and data fusion techniques based on information entropy, fuzzy analytical hierarchy, and the Dempster-Shafer theory are utilized to establish the data processing unit. An ambient excitation modal test was conducted to verify the numerical model. In situ mechanical responses from monitoring sensors and visual inspection results are fed back to the data processing unit as indicators of the safety grade of the bridge. The novel assessment system proposed here can feasibly and effectively provide support for bridge management and maintenance.