Prestressed Concrete Bridge Girders Research Articles

Enhancing structural damage evaluation of PC girder bridges through digital twinning Bayesian model updating

Developing a unified analytical framework to assess the structural performance of deteriorated prestressed concrete (PC) girder bridges is important for their maintenance. This study aims to construct a physics-based digital twin framework for PC girder bridges incorporating Bayesian model selection and updating, a high-fidelity three-dimensional (3D) finite element (FE) model, and a method for simulating prestressed tendon damage. In this study, three PC girder specimens were designed and tested to evaluate the effects of tendon rupture near the anchorage region on structural performance. Bayesian model selection was used to determine the most plausible model class based on the estimated model evidence. The most probable values (MPVs) of the model parameters, derived from the estimated posterior probability density functions (PDFs), were then used to calibrate the FE model, which reflects a healthy state of the PC girder bridge. This updated FE model serves as the baseline for conducting what-if scenario simulations. Subsequently, nonlinear segments of the constitutive model, obtained from coupon tests, and a simulation method for tendon rupture were incorporated into the updated FE model. Nonlinear static simulation results obtained through the updated model were found to be consistent with both the observed crack pattern and the load–deflection curve. The reliability of the digital twinning FE model for assessing tendon damage and for predicting the residual load-bearing capacity was verified through comparison with measured data. Therefore, the digital twinning Bayesian model updating approach shows potential applications in continuous structural health monitoring (SHM) of PC bridges.

Structural Health Monitoring at Single-span Prestressed Concrete Girder Bridge by Ambient Vibration Measurement and Identification Modal Frequency

Structural Health Monitoring at Single-span Prestressed Concrete Girder Bridge by Ambient Vibration Measurement and Identification Modal Frequency

Corrosion-induced fragility of existing prestressed concrete girder bridges under traffic loads

Italian and European transportation networks include a significant number of existing bridges, built since the early ‘60s, characterised by simply supported prestressed concrete (PC) girders with post-tensioned steel tendons. Corrosion of tendons, which may lead to significant loss of structural capacity, cannot be detected by simple visual inspections and requires advanced and expensive testing by bridge owners. Therefore, procedures aimed at risk-informed prioritisation of advanced inspections and possibly retrofit are needed. The paper presents a study on the fragility of existing PC girder bridges considering traffic loads, accounting for corrosion-induced effects. An automated framework is proposed, aiming at the efficient probabilistic structural assessment of the investigated bridge typology accounting for different critical corrosion scenarios and the influence of knowledge-based uncertainty related to geometric and mechanical properties. To simulate corrosion effects, prestressing steel tendon geometric and mechanical characteristics are modified through a specific algorithm able to estimate variations in flexural and shear bearing capacity of critical cross-sections. To simulate the traffic loads, a simplified analysis is performed by using code-based traffic load models. In the paper, the framework is tested with reference to a dataset of case-study superstructures. The obtained fragility curves are deeply discussed, highlighting the effects of the number of girders and span length on the corrosion-induced increase in fragility. Although the proposed methodology presents some simplifications, it could improve the current practices of risk prioritisation, by supporting transportation authorities in ensuring the safety of the existing bridge stock.

Grouting inspection of PC bridge girder using Ultrasonic Pulse Echo Tomography and multiparameter evaluation procedure

Assessing the condition of grouting in post-tensioned tendons within Prestressed Concrete (PC) structures stands as a challenge in the field of civil engineering infrastructure maintenance. Current non-destructive testing (NDT) techniques employed for grouting assessment have certain constraints. For instance, the Impact-Echo method exhibits relatively low accuracy, while the X-Ray method proves to be costly and demands significant time and labor resources. Simultaneously, there exist promising alternative NDT techniques that offer potential for grouting inspection. In this study the authors used commercially available Ultrasonic Pulse Echo Tomography device with an array of dry-contact sensors and multiparameter method of evaluation. The evaluation method uses amplitude of ultrasonic pulse reflected from PC sheath, backwall and phase of reflected ultrasonic pulse. The experimental study on large-scale specimens confirmed that the evaluation method allows to achieve higher accuracy, as compared to existing methods of evaluation. The developed procedure was applied for inspection of PC bridge girder on an existing road bridge. The inspection was carried out on one of the spans of the bridge, which had 4 I- shaped PC girders. The results of Ultrasonic Pulse Echo Tomography were confirmed by means of drilling and borescope inspection method The results of both methods showed good correlation.

Dynamic serviceability and safety reliability analysis of aging PC girder bridges with non-prestressed reinforcement considering concrete shrinkage, creep and stochastic vehicle load flows

Prestressed concrete (PC) bridges’ service performance displays time-dependency due to several factors including concrete shrinkage, creep, resistance degradation, and stochastic vehicle load flows. These non-stationary vehicle load flows, combined with concrete shrinkage, creep, and resistance degradation, result in sequential alterations of internal forces and deformations in simply supported PC girder bridges, ultimately influencing their dynamic reliability. This study proposes a robust methodology that considers the impact of traffic loading, shrinkage, and creep to analyze the dynamic reliability of simply supported PC girder bridges through the development of a load probability model. A stochastic model for truck loads is generated using motion measurement data, which can be used to calculate bridge internal forces and subsequent quantitative analysis of structural deformation due to shrinkage and creep. Subsequently, the formula for the first exceedance probability under resistance degradation is presented and validated through Monte Carlo simulation. Reliability analysis is conducted for both serviceability and load carrying capacity limit states to assess the impact of shrinkage, creep, and increased mean vehicle load on structural reliability. The proposed method offers the theoretical foundation and practical guidance for assessing the structural health status of in-service bridges, thereby providing valuable insights into their long-term performance and maintenance requirements.

Influence of strand rupture on flexural behavior of reduced-scale prestressed concrete bridge girders with different prestressing levels

In prestressed concrete (PC) bridges, high-strength prestressing steel plays a key role in the flexural response of girders. In both pre-stressed and post-tensioned PC bridge girders, damage induced by corrosion or impact of under-passing high vehicles may led to rupture of one or more strands, significantly affecting the load-carrying capacity against dead and traffic loads. This paper presents an experimental study on the response of PC girders affected by strand rupture at different locations. Four reduced-scale post-tensioned concrete girders with different levels of initial prestressing force were tested under four-point bending. Two specimens with a different level of prestress were initially tested in undamaged configuration to provide a basis for the assessment of damage effects. The other pair of specimens were intentionally damaged - having the same initial prestressing level of their undamaged counterparts - in the lower tendon to investigate their limited flexural response under different performance levels including serviceability and collapse. Damage turned into a different critical cross section outside the loading region, i.e. both cracking and collapse were attained 1.1m away from midspan. In the last section of the paper, a cross sectional analysis of the girder was developed at cracking and ultimate conditions for the prediction of damage impact on failure mechanisms, thus validating the experimental findings.

The Risk of Failure Assessment in Bina Marga Standard Designed Prestressed Concrete Girder Bridges under B-WIM Load Measurement

The use of precast prestressed concrete girder bridges in Indonesia has been increasing rapidly due to their high quality, reliability, and faster construction on site. The girder components are typically designed for a specific bridge span and can be prefabricated. The Directorate General of Highways of the Ministry of PUPR (Bina Marga) has released a standard design for prestressed concrete girder bridges with a typical span of up to 40 m. This design is based on the bridge loading standard SNI 1725 2016, which determines the live traffic load through consensus due to limited data on actual traffic load measurement results. However, the Ministry of PUPR has been implementing actual traffic load measurements using weigh-in-motion (WIM) technology to directly measure the load of passing vehicles. In this study, a risk assessment of the failure risk of a standard Bina Marga bridge with a 40-m span prestressed concrete girder type was conducted based on B-WIM load measurements. The results of this assessment indicate that the standard Bina Marga bridge has a failure risk of 1.48 x 10-4, which is smaller than the acceptable risk of failure according to the AASHTO LRFD Bridge Design Specification as referenced in SNI 1725 2016.

Bayesian-optimized interpretable surrogate model for seismic demand prediction of urban highway bridges

Urban highway bridges are crucial for regional economic development and population mobility, but they are vulnerable to seismic hazards. Accurately predicting the seismic demands of bridges is essential. Several commonly-used methods for seismic demand estimates, such as cloud analysis, incremental dynamic analysis, and multiple stripe analysis, are computationally expensive and subject to theoretical assumptions and convergence issues, especially for portfolios of bridges. Machine learning techniques can be effective, but their lack of interpretability hinders understanding of the surrogate model's predictions. To address these challenges, this study develops a Bayesian-optimized interpretable ensemble learning surrogate model for predicting and interpreting the critical seismic demands of urban highway bridges.Thousands of continuous prestressed concrete girder bridges with typical geometric configurations in China are generated, and 120 ground motion records with different frequency, waveform, and duration characteristics are chosen. The seismic demand dataset is established based on nonlinear time-history analyses for urban highway bridges, accounting for different types of uncertainties. The surrogate models are developed based on the XGBoost ensemble learning method, with hyperparameters automatically and efficiently determined by Bayesian optimization technique. Compared to the random search and grid search methods, Bayesian optimization is approximately 8 times and 29 times faster, respectively, and it also achieves the highest prediction accuracy. Meanwhile, the relationship of each hyperparameter in the surrogate model is also revealed. The prediction results of the proposed model are compared with other machine learning models. The SHAP algorithm is subsequently used to explain the model predictions regarding the feature importance, global interpretations, and feature dependency analysis. The study quantifies the contribution of each structural feature and seismic intensity measure to the selected critical seismic demand and identifies the interaction effects between different input variables in the prediction.

Finite Element Analysis of Chloride Ingress in Prestressed Concrete Bridge Girders Accounting for Service-Life Ambient Conditions

Finite Element Analysis of Chloride Ingress in Prestressed Concrete Bridge Girders Accounting for Service-Life Ambient Conditions

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.

Multidimensional nonlinear numerical simulation of post‐tensioned concrete girders with different prestressing levels

AbstractMost of the Italian infrastructures have been built since the mid‐twentieth century. Prestressed concrete (PC) has been widely used, especially for bridges and viaducts. These structures have proved effective over time, but their performance could be affected by degradation phenomena (i.e., corrosion of the tendons and residual prestressing) or construction defects (i.e., grouting of the ducts), which need to be accurately modeled. This paper focuses on the flexural response of two reduced‐scale, posttensioned, PC bridge girders, prestressed with two different jacking forces and tested under four‐point bending configuration. Four multidimensional numerical models were developed to simulate the experimental behaviors of the selected specimens, using two alternative computational strategies, namely, the finite element method (FEM) and applied element method (AEM). Three FEM modeling were considered, ranging from one‐dimensional lumped‐plasticity models to two‐dimensional and three‐dimensional (3D) spread‐plasticity models. Besides, 3D AEM models were developed into another software package. The accuracy and the computational costs of the two numerical strategies are discussed in this paper. Also, the main features of each numerical modeling technique are addressed, including comparisons between numerical and experimental global response data as well as the statistical characterization of the model error. Based on these different features, the authors also suggest the most suitable numerical strategy for future studies on PC girders.

A simplified ANN-based evaluation method for creep sensitive girder bridge identification at preliminary design stage

Excessive deflection which exceeded expectations has been identified as one of the main problems contributing to long-term performance degradation of long-span girder bridges. Although the 3D refined finite element model of the full bridge can improve the prediction accuracy of long-term creep deformation, there is still a lack of efficient creep-sensitive structural judgment methods in the preliminary design stage. This study was thus intended to develop a new evaluation method and model to identify the possibility of excessive deflection will occur by utilizing simple structural design parameters, which contributed to new understandings of the creep deformation of bridge structural level. A finite element model database established by 20 long-span prestressed concrete girder bridges with actual project backgrounds was used for providing training, testing, and validation sample datasets for the artificial neural networks (ANN). The Back Propagation (BP) model was chosen for creating mappings among variables and results and solving complex problems with a fairly accurate prediction even without sufficient information. The indicator of deflection-span ratio difference between creep models was proposed as the key analysis factor. A case study was conducted to validate the effectiveness of the ANN model. The mean absolute error (MAE) between the results of the ANN model and FE analysis was 6.25%, which indicated a high consistency. The analysis of bridge design parameters using the ANN model revealed that it had a high risk of excessive deformation, which was consistent with the conclusion of the actual situation. Multiparameter sensitivity analysis results from the model also suggest that the side-span ratio, the main span, and the deflection caused by the pavement are the most three significant impacts compared to different input variables in this model. Based on the results, it can be concluded that the performance of the ANN-based technique can predict possible excessive creep problems in advance.

Time-variant reliability analysis of simply supported PC girder bridges considering shrinkage, creep, resistance degradation and vehicle load flows

The long-term performance of simply supported Prestressed Concrete (PC) girder bridges exhibits dynamic characteristics because of concrete shrinkage, concrete creep, resistance degradation and vehicle load flows. The vehicle loads are non-stationary and random, which interacts with concrete shrinkage, concrete creep and resistance degradation to cause dynamic changes of bridge internal force and deformation, further, bridge dynamic reliability occurs. This study presented a reasonable method for calculating the time-varying reliability of simply supported PC girder bridges under the effects of traffic loads and concrete shrinkage creep. Stochastic truck-load models were simulated based on site-specific weigh-in-motion measurements, then the internal forces of the bridge were calculated when the mean value of vehicle loads increases by 1% per year. Considering the resistance degradation and load effect increase, the PC bridge reliability for serviceability limit state and capacity-carrying ultimate state were analyzed using first-passage probability method and Monte-Carlo method, respectively. The accuracy of the proposed method was verified by comparison. The evaluation results show that the failure probability including concrete shrinkage and creep has increased significantly, creep is affected by the bridge span and the number of main girders, and the reliability assessment results are safer for bridges with smaller spans.

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.

Gaussian process regression-based load-carrying capacity models of corroded prestressed concrete bridge girders for fast-screening and reliability-based evaluation

Fast screening and reliability-based evaluation of corroded prestressed concrete (PC) bridge girders for safety assessment requires efficient capacity prediction models. This paper aims at developing data-based prediction models to quantify corrosion effects on load-carrying capacity of PC girders that are precast and standardized for short-span bridges. The load-carrying capacity of corroded bridge girders depends on their initial design configuration (e.g., those characterized by the standardized PC girders), loading condition (e.g., shear-span-to-effective-depth ratio), and corrosion conditions (e.g., corrosion degree). To develop data-based prediction models, generating sufficient data through physical experimental tests of full-scale corroded PC girders is prohibitively costly. Thus, a virtual experimental database is generated numerically using two-dimensional continuum-based finite element (FE) models for corroded PC girders, after being validated using 9 corroded PC girders tested in the literature with flexure or shear failure. To this end, a total of 4,165 PC girders under point loading are simulated to consider various design, loading, and corrosion conditions to estimate their load-carrying capacities. With this database, probabilistic machine learning, specifically Gaussian process regression or kriging, is used to develop (1) a residual capacity factor model (i.e., the ratio between load-carrying capacities from corroded and uncorroded girders), and (2) a load-carrying capacity prediction model (i.e., to predict the load-carrying capacity of uncorroded/corroded girders). The first model is used to study the load-carrying capacity reduction of PC girders due to corrosion compared to their uncorroded counterparts; this can reveal how the increasing corrosion condition affects the load-carrying capacity of corroded PC girders together with other design and loading parameters. The second model is developed to predict the load-carrying capacity of corroded PC girders as a function of design, loading, and corrosion parameters; its application to conditional reliability analysis provides insights into corrosion effect on the probability of failure of corroded PC girders at given load levels when the capacity is affected by corrosion. The application results of the two models enable engineers to quantify the corrosion effect on PC girders in terms of (1) reduction in load-carrying capacity for fast screening and (2) increase in probability of failure for reliability-based evaluation.

Large-Scale Experimental Static Testing on 50-Year-Old Prestressed Concrete Bridge Girders

The heritage of existing road infrastructures and in particular of bridges consists of structures that are approaching or exceeding their designed service life. Detrimental causes such as aging, fatigue and deterioration processes other than variation in loading conditions introduce uncertainties that make structural assessment a challenging task. Experimental data on their performances are crucial for a proper calibration of numerical models able to predict their behavior and life-cycle structural performance. In this scenario, an experimental research program was established with the aim of investigating a set of 50-year-old prestressed concrete bridge girders that were recovered from a decommissioned bridge. The activities included initial non-destructive tests, and then full-scale load tests followed by a destructive test on the material samples. This paper reports the experimental results of the full-scale tests conducted on the first group of four I-beams assumed to be in good condition from visual inspection at the time of testing. Loading tests were performed using a specifically designed steel reaction frame and a test setup equipment, as detailed in the present work. Due to the structural response of this first group of girders, a uniform behavior was found at both service and ultimate conditions. The failure mechanism was characterized by the crushing of the cast-in-situ top slab corresponding to a limited deflection, highlighting a non-ductile behavior. The outcomes of the experimental research are expected to provide new data for the life-cycle safety assessment of existing bridges through an extended database of validated experimental tests and models.

Dynamic Similitude Analysis for Establishing Scaled-Down Model to Predict Vibration Behaviour of Prestressed Concrete Bridge Girder

Dynamic Similitude Analysis for Establishing Scaled-Down Model to Predict Vibration Behaviour of Prestressed Concrete Bridge Girder

On-Site Manufacturing Method for Pre-Tension U-Type Pre-Stressed Concrete Girders and Analytical Performance Verification of Anchoring Blocks Used for Applying Tension Force

Development of U-type pre-stressed girders has been attempted to increase the length of I-type girders in South Korea. However, a length of 30 m or less is common because the self-weight, according to the post-tension method, is large. In this study, the pre-tension method was applied without limiting the post-tension method to induce a reduction in self-weight and in the materials used because of the decrease in the cross section. In addition, the authors proposed an application of an on-site pre-tensioning method using the internal reaction arm of a U-type girder. A pre-stressed concrete U-type girder bridge is composed of a concrete deck slab and a composite section. Structural performance characteristics, such as resistance and rigidity, were improved compared to those of the PSC I-type girders. Construction safety is also improved in the manufacturing and installation stages, and the elongation ratio is reduced because of the reduction in the weight of the girders. Therefore, it is possible to ensure the aesthetic landscape and economic efficiency of bridges. As a result, it is expected that efficient construction will be possible with high-quality factory-made and cast-in-place members. In this study, the pre-tension method is introduced in the field, and the analytical performance of the anchoring block used for tension is verified.

Numerical Analysis of Prestressed Concrete Bridge Girders Failing in Shear

Numerical Analysis of Prestressed Concrete Bridge Girders Failing in Shear

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.