Concrete Girder Bridges Research Articles

A Two-Step FE Model Updating Approach for System and Damage Identification of Prestressed Bridge Girders

This study presents a two-step FE model updating approach for health monitoring and damage identification of prestressed concrete girder bridges. To reduce the effects of modeling error in the model updating process, in the first step, modal-based model updating is used to estimate linear model parameters mainly related to the stiffness of boundary conditions and material properties. In the second step, a time-domain model updating is carried out using acceleration data to refine parameters accounting for the nonlinear response behavior of the bridge. In this step, boundary conditions are fixed at their final estimates using modal-based model updating. To prevent the convergence of updating algorithm to local solutions, the initial estimates for nonlinear material properties are selected based on the first-step model updating results. To validate the applicability of the two-step FE model updating approach, a series of forced-vibration experiments are designed and carried out on a pair of full-scale decommissioned and deteriorated prestressed bridge I-girders. In the first step, parameters related to boundary conditions, including stiffness of supports and coupling beams, as well as material properties, including initial stiffness of concrete material, are estimated. In the second step, concrete compressive strength and damping properties are updated. The final estimates of the concrete compressive strength are used to infer the extent of damage in the girders. The obtained results agree with the literature regarding the extent of reduction in concrete compressive strength in deteriorated concrete structures.

Automatic modal identification of bridges based on free vibration response and variational mode decomposition technique

Free vibration tests are often performed for the dynamic characterization of structural systems and components. In the field of road bridges monitoring, such tests require minimal equipment (i.e., a sparse network of few sensors, even a single one) in order to gather – quickly and at low cost – some essential information about the dynamic behavior of the structure. The experimental free-vibration response is thus processed for estimating structural modal features which, in turn, can be useful to corroborate or update available numerical models as well as to evaluate current bridge conditions. Within this framework, an efficient computational strategy is here developed for the modal identification of bridges based on their free vibration response. The procedure combines the variational mode decomposition technique with the area ratio-based damping identification method, which ensures enhanced robustness to noise-related effects in field-test signals. A novel procedure is implemented to make the whole identification process fully automatic, in such a way that it does not depend on specific structural features (e.g., to identify even closely-spaced modes) or subjective user’s settings. After a preliminary validation with a synthetic multi-modal signal, the proposed procedure is applied to two real case-studies. The first case-study deals with the identification of natural frequencies, modal damping ratios and mode shapes of prestressed concrete girder bridge decks. Particularly, experimental natural frequencies and mode shapes are compared with numerical predictions obtained from a finite element model of the bridge. The dynamic characterization of the cables of a cable-stayed bridge is considered in the second case-study. Herein, experimental natural frequencies of all the stay-cables are initially analyzed for estimating their stress levels, which have been critically analyzed to detect the existence of relaxation losses. Moreover, modal damping ratios of all the stay-cables are identified and compared to estimates obtained by alternative ambient-vibration-based techniques.

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.

A Stress Index-based Tendon Optimization Method for Prestressed Concrete Continuous Girder Bridges

PDF HTML XML Export Cite reminder A Stress Index-based Tendon Optimization Method for Prestressed Concrete Continuous Girder Bridges DOI: 10.59238/j.pt.2023.01.001 Author: Affiliation: (1. Department of Bridge Engineering, Tongji University, Shanghai 200092, China; 2. Anhui Transport consulting & Design Institute Co., Ltd. Anhui 230088, China) Clc Number: Fund Project: Article | Figures | Metrics | Reference | Related | Cited by | Materials | Comments Abstract:Traditional tendon design methods for prestressed concrete (PC) continuous girder bridges are tedious since they obtain feasible solutions based on trial calculation, and the existing optimization methods that can obtain the optimal solution have deficiencies regarding structural stress. In this study, based on research on the refined bridge design conducted in the Department of Bridge Engineering at Tongji University in recent years, a stress index-based tendon optimization method for PC continuous girder bridges is pro-posed. First, various tendon layouts are summarized, and a reasonable tendon layout is selected. Then, a mathematical tendon optimization model is established. After meeting the specifications and construction feasibility requirements, a genetic algorithm is used to find the optimal solution. This method not only realizes tendon forward design but also obtains a satisfactory solution. Finally, this method is used to successfully optimize the tendons of a three-span PC continuous girder bridge, which verifies the ration-ality of the method. Reference Related Cited by

Finite Element Simulation of Temperature Variations in Concrete Bridge Girders

The internal temperature of cast-in-place concrete bridges undergoes strong variations during the construction as a result of environmental factors. In order to determine precisely such variations, the present study relies on the finite element method, used to model the bridge box girder section and simulate the internal temperature distribution during construction. The numerical results display good agreement with measured temperature values. It is shown that when the external temperature is higher, and the internal and external temperature difference is relatively small, the deviation of the fitting line from existing specifications (Chinese specification, American specification, New Zealand specification) is relatively large and vice versa.

Experimental background behind new AASHTO LRFD specifications for partially partially debonded strands

To develop a unified approach for the design of partially debonded strands in prestressed concrete highway bridge girders, a coordinated analytical and experimental investigation was conducted. This investigation examined amounts of partial debonding, distribution of partially debonded strands within the cross section, debonded lengths, locations and staggering of termination of debonded strands, confinement of debonded regions and their termination points, and the impact of adding nonprestressed reinforcement in the region of partial debonding. The results from testing full-scale I- and U-shaped girders indicate that partially debonding strands does not result in deleterious performance if adequate reinforcement is provided to resist the longitudinal tension due to bending and shear. Crack patterns and angles were not noticeably affected by the amount of debonding. Regardless of the debonding ratio, the maximum measured crack widths at the capacities predicted by the eighth edition of the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications remained small. The requirements for debonded strands were revised significantly in the ninth edition of the AASTHO LRFD specifications based on the presented research.

An Explicit Approach for Determining the Rational Length of Steel Portion in Steel–Concrete Hybrid Girder Bridges

The steel–concrete hybrid girder bridge structure is a combination of steel and concrete members in the direction of the bridge length. In long-span segmental concrete box girder bridges, the utilization of lightweight steel girders in the middle portion of the main span would greatly reduce the bridge self-weight while decreasing concrete creep and shrinkage effects. A critical parameter in the design of hybrid girder bridges is the rational length of the steel portion as a part of the main span (in other words, the rational location of the steel–concrete connection). Based on the concept of system equivalence, the steel–concrete hybrid system is equivalent to a full-concrete system with a reasonable span arrangement. The governing condition of the equivalence is that both systems have the same magnitude of self-weight hogging bending moments over the piers. Applying the system equivalence method, the rational length ratio of the steel portion to the main span (ξ) is explicitly solved, and its relationship with the length ratio of side span to main span (λ) is established. Finally, the proposed analytical approach is validated by five case studies, indicating that it is an effective and efficient method for the preliminary design of hybrid girder bridges.

Investigation of repair techniques for deteriorated end regions of prestressed concrete bridge girders

Deterioration of the end regions of prestressed concrete bridge girders is commonly observed in the field when girders are exposed to chloride-laden water that has leaked through failed expansion joints. Because the deterioration is often localized to the end regions of the girders, reliable repair techniques can provide a means to extend girder service life, avoiding the need for immediate superstructure replacement. To evaluate different repair methods and identify key design considerations for end region repair, shear tests to failure were conducted on prestressed concrete girders extracted from a decommissioned superstructure. Three repair systems were evaluated: an externally bonded fiber-reinforced-polymer (FRP) system, a near-surface-mounted FRP system, and a concrete end block. Only the externally bonded FRP system successfully restored both the strength and initial stiffness of the girder. Although the other two methods were not successful, the tests on the repaired girders highlight important factors that must be considered when designing repairs or conducting further research. The tests also demonstrate that end region deterioration can cause significant (> 40%) reductions in strength, underscoring the importance of addressing such deterioration observed in the field.

Acoustic emission testing for multi-scale assessment of reinforcement corrosion in concrete structures

Degradation of existing structures poses a serious threat to our built environment. The aim of this paper is to investigate the use of acoustic emission monitoring in degradation assessment of existing structures, focusing specifically on corrosion damage detection in reinforced concrete structures. Reinforcement corrosion is seen as one of the most significant and costly degradation mechanisms that impact the durability and structural safety of our built infrastructure and Modern heritage buildings. The paper presents a multi-scale experimental approach, from material to structure, focusing on two challenges: (i) monitoring the evolution of the corrosion process itself and the consequential concrete cracking during accelerated corrosion, and (ii) identifying the different AE sources in this complex process. The application of AE testing for rebar corrosion monitoring is investigated on various sample types and scales under accelerated conditions in a lab environment, and from on-site monitoring of a concrete girder bridge. Results show that the developed test setups, data filtering and processing procedures substantially improve AE-based corrosion damage monitoring, and provide a valuable contribution towards on-site application.

Analysis on the Damage Assessment Method of Reinforced Concrete Girder Bridge under Collision Based on Trace Theory

Analysis on the Damage Assessment Method of Reinforced Concrete Girder Bridge under Collision Based on Trace Theory

A new Rectangle Subsections Method (RSM) for the design of a reinforced concrete T-shaped cross-section bridge girders

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Crack detection in arbitrary beam cross-sections using a new mass-spring system

This paper presents a new system of spring masses for crack detection in structures. For modeling cracks in arbitrary cross-sections, the Gaussian quadrature method is used to obtain the integral of the energy release rate over the cracked cross-section. In the proposed method, the system of spring masses is used to obtain the time histories of displacements, which are then combined into a relative time history by weighted summation. For detecting cracks, three springs and three equal masses with equal spacing from each other are placed on the beam, starting to move consecutively from one end. At each station, the time history of the system under excitation by an external load applied to the middle mass is extracted. The extracted data in each station shows the relative stiffness of that station compared to adjacent stations. The differences in system responses are used to estimate the position of cracks. The performance of the proposed method was evaluated using the Z24 bridge and a three-span concrete girder bridge in which a multiple-crack scenario was applied. These examples were used for evaluating the proposed system for the effect of parameters such as the weight and spacing of masses. The novelty of the presented method is to model cracks in arbitrary beam cross-sections and identify cracks in real bridge beams using a new effective mass-spring system that uses only three sensor data.

Hybrid control of steel-concrete composite girder bridges considering the slip and shear-lag effects with MR–TMD based on train-bridge interactions

With the speed of trains higher and bridge structures towards larger spans with lighter weight, the train-bridge resonance will become fairly pronounced. Therefore, to ensure the safety of bridge structures, research on vibration control is of far-reaching significance, especially for steel–concrete composite girder bridges with mechanical properties, such as slip, and shear lag. Therefore, based on a magnetorheological tuned mass damper (MR–TMD), this paper proposes a hybrid control strategy for the steel–concrete composite girder bridge considering whether the trains are either on or off the bridge, and applies it to a numerical example, reducing vertical dynamic responses of a railway steel–concrete composite girder bridge based on train-bridge interactions. The results illustrate that this control strategy is suitable for the time-varying steel–concrete composite girder bridge-train coupling system, and exhibits reliability, stability and robustness to some extent, which has a bright future in engineering applications.

Impact of the Implementation of Unbonded Seismic Isolators on the Design and Retrofitting of Bridges

The existence of road infrastructure such as bridges that do not meet current design criteria, the deterioration of these due to use, environmental factors and extraordinary or unforeseen conditions, and the increase in seismic and gravitational design loads due to regulatory updates, generate the need for search of new design and retrofitting alternatives for this type of structure. Thus, the conditions of these structures need to be assessed and corresponding interventions need to be identified. It is important to implement alternatives that are both economically and functionally efficient. For example, base isolation can reduce direct construction costs by using devices designed and built in the country of origin, but the unfamiliarity and importation costs of these devices are the main obstacles to mass use. In this article, a comparative analysis is performed of a conventional design and an integrated design for base isolation using low-cost unbonded fiber-reinforced elastomeric isolators (U-FREIs) made in Colombia. A methodology is proposed for the analysis of new and existing isolated structures, in which the isolators are placed between the substructure and superstructure. This methodology is used to design and strengthen a typical prestressed concrete girder bridge, and the results are compared against those obtained using a conventional scheme. Finally, an existing bridge is analyzed using on-site measurements to determine the dynamic properties and modify the numerical model used for analysis, design, and retrofitting. The effectiveness of the proposed methodology as a tool for the design of new bridges and the retrofitting of existing structures was verified for all cases. Economic and structural benefits were evidenced by reductions in direct costs of up to 15% and the seismic force of up to 20%, respectively.

Semi-Active Control of Seismic Response on Prestressed Concrete Continuous Girder Bridges with Corrugated Steel Webs

To improve the seismic capacity of prestressed concrete (PC) continuous girder bridges with corrugated steel webs (CSWs), suitable damping control measures can be used to effectively reduce the seismic response of the bridge. Based on the semi-active control theory, the semi-active control system of a three-span PC continuous girder bridge with CSWs is designed, and the semi-active control system program of the three-span PC continuous girder bridge with CSWs is compiled by MATLAB. The time–history curves of damper energy consumption of active optimal control algorithm and three different semi-active control algorithms are compared and analyzed, as are the time–history curves of main girder displacement, acceleration, and pier internal force with or without semi-active control. The study shows that the rational determination of the weight matrix coefficient can make the active control achieve a better vibration absorption effect and economy. The semi-active control algorithm of Hrovat has the best vibration absorption effect, which is closest to that of the active optimal control algorithm. Under the state of semi-active control, the average vibration absorption rate of displacement and acceleration of the main girder with CSWs are 71% and 20%, respectively. The time–history curve of bending moment and shear force in the pier bottom is similar, and the average vibration absorption rate of bending moment and shear force at the bottom of pier #2 is 70%. At the same time, the average vibration absorption rate of bending moment and shear force at the bottom of pier #3 is between 42% and 48%. The semi-active control measure has a good vibration absorption effect on the overall seismic response of the PC continuous girder bridges with CSWs. This study provides a certain reference for the seismic reduction and isolation design of composite structure bridge with CSWs.

Progressive collapse analysis of prestressed concrete girder bridges using improved applied element method

AbstractIn this paper, the Improved Applied Element Method (IAEM), which was originally developed as an effective analysis technique for large-scale bonded and unbonded prestressed structures, is utilized to carry out failure modeling of prestressed bridges under different hazard loads. A typical prestressed concrete girder bridge is analyzed under two hazardous loading scenarios. The first one is applying a detonation charge located in the middle of the central span, while the second scenario is a sudden failure of a column representing a truck or a vessel colliding with the bridge pier. For both scenarios, the collapse analyses of the bridge structure after damage are explored. In addition, the mechanism and severity of damage in the bridge pier and deck are investigated. Both material and geometric nonlinearities are considered in the analysis. Moreover, it considers contact-impact, re-contact, and inertia effects, and hence, it can track the collapse stages of the structure as well as debris movement until the complete collapse of the structure. The results show a strong capability for simulating the total performance of the bridges from early the stages of loading until the total collapse, with a clear graphic representation of the collapse phenomena.

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

Verification of Precast Concrete Girder Bridge Under Static Load

Abstract Large-scale construction of transport infrastructure inevitably includes the construction of new bridges. During the design process, many assumptions and simplifications are taken into account. Therefore, the verification of the structural response of new bridges is necessary. One of the possible tests of structural response is a proof-load test which can detect certain problems of investigated structures. The paper introduces numerical and experimental analysis of the new bridge, which is located on Slovak Highway D1, section Hricovske Podhradie – Lietavska Lucka. The verified bridge is a four-span continuous structure with a total length of 129.4 m. The bridge is a representative of typical precast girder bridges adopted for construction of Slovak highways. The superstructure consists of eight post-tensioned precast I-beams. During a load test, predicted structural response was verified to check for any unusual behaviour. Finally, recorded data was summarised and report was distributed to all subcontractors and bridge owner. This information may help in further bridge management program.

Fire hazard in concrete bridges: review, assessment and mitigation strategies

This paper analyses the vulnerability of concrete bridges to fire through a comprehensive review and proposes strategies to overcome the fire hazard. As part of mitigation strategies, the application of advanced analysis is illustrated through developing a non-linear transient finite-element model for fire resistance evaluation of prestressed concrete bridge girders. The numerical model is validated using results from fire tests on concrete beams. The model is applied to investigate the effect of girder shape (rectangular and I-shaped sections) and strength of concrete (normal- and high-strength concretes) on the fire resistance of typical concrete bridge girders. Results from the analysis clearly show that fire resistance of high-strength concrete (HSC) girders is lower than that of normal-strength concrete (NSC) girders, which is attributed to its faster degradation of strength and stiffness with temperature. On the other hand, I-shaped girders present lower fire resistance than similar girders of rectangular cross-section due to rapid degradation of its shear capacity. This is mainly the result of slender web widths in I-shaped girders, which results in faster progression of temperatures in the web, leading to early failure under the shear limit state. This problem can be overcome by developing relevant fire mitigation strategies, such as provision of external thermal insulation on girders of critical bridges.

Study on the Structural Performance of UHPC Pavement and Hinge Joint Reinforcement for Hollow Slab Girder Bridges

To address the problem of structural performance degradation caused by hinged joints and pavement damage, we utilized actual engineering to conduct a construction study on the overall replacement of pavement and hinge joint reinforcement in ultra-high-performance concrete (UHPC) hollow slab girder bridges. A replacement and reinforcement design was developed and reconstruction was undertaken. By using UHPC and reinforcement bars, the adjacent slab girders were designed to work together under specific construction process guarantees for the characteristics of UHPC. The corresponding interface treatment and a combination of planting bars and steel mesh were necessary. According to the strain and deflection monitoring results, the overall performance of the bridge after pavement and hinge joint reinforcement was verified. The strain amplitude of the reinforcement was approximately 10 με, and that of the concrete was approximately 5 με. The deflection difference of the adjacent girder was similar, which proved that the hinge joints connect girders and transfer force effectively. All the results clearly demonstrated the positive overall effect of the UHPC replacement method. The conclusions could provide a reference for the reinforcement and reconstruction of similar projects.