RC Bridge Research Articles

Degraded Gerber Saddles in RC Bridges

Degraded Gerber Saddles in RC Bridges

Numerical Study on Seismic Performance of Buckling-Restrained Braced Double-Pier RC Bridge with Bolted Gusset Connections

Buckling-restrained braces (BRBs) have been widely employed in buildings and bridges due to their excellent ductility and energy dissipation capabilities. However, a considerable frame action will be introduced at the beam–column–brace joint for the traditional weld gusset connection under a severe earthquake. To reduce the negative frame action effect, three alternative bolted gusset connections were developed in this study. A buckling-restrained braced-double-pier RC bridge (BRB-RCB) model was constructed by ABAQUS and calibrated by the existing experimental tests. Parameter analyses were conducted to investigate the effects of various connection types on the seismic performance of the BRB-RCBs. It was found that the proposed bolted gusset connection effectively released the constraints of gusset-to-frame interfaces, resulting in a low stress level at the panel zone. The BRB-RCB with the well-designed bolted connection exhibited excellent seismic performance even when subjected to a lateral drift of 3%.

Damage identification in RC bridges by confronting two approaches: visual inspection and numerical analysis

The present article aims to summarize the research study that was conducted the efficiency of methods and techniques designed for the detection and localization of faults in civil engineering structures, particularly in bridge structures. The diagnosis of a real reinforced concrete bridge by a visual inspection is presented. Then, three numerical damage detection and localization methods, namely the eigenfrequency change method, the eigenstrain change method (Coordinate Modal Assurance Criterion – CO-MAC), and the strain energy change method, are explicitly presented. Furthermore, the modeling of the bridge, before and after damage, using the Ansys software was carried out in order to identify all possible bridge defects. Afterward, the numerical results are graphically represented using the above mentioned methods. This made it possible to confirm the initial diagnosis and hence assess the damages observed on site and also in other zones.

Scour-dependent seismic fragility curves considering soil-structure interaction and fuzzy damage clustering: A case study of an Algerian RC Bridge with shallow foundations

Bridges face many hazardous events. For those located along rivers, additional flood-related hazards, such as local scour, can occur. This study focuses on the vulnerability due to the ductility loss of bridges supported on shallow foundations, where both scouring and seismic risks are considered.The impact of scouring on bridge stability has received less consideration compared to seismic vulnerability. This study aims to overcome this lack by using a numerical modeling approach employing ductile fragility curves to assess the vulnerability of a typical reinforced concrete bridge model supported on shallow foundations. A complete bridge model is used, considering all the bridge's components and the soil-structure interaction. Moreover, the damage results are clustered by a fuzzy process to avoid analysis overestimation.The obtained results highlight the significance of considering both seismic and scouring in bridge vulnerability assessment, in addition to using a fuzzy clustering to optimize the obtained damage. For a bridge with shallow foundations, results indicate that scouring can positively influence the bridge's ability to dissipate energy, thereby improving its ductility. Although ductile fragility assessment could be used to assess the vulnerability of buildings during seismic events; however, it may not be relevant for other hazards, such as scouring.

A study of the impact damages detection and dynamic responses of RC bridge piers based on a frequency domain correlation method

The applicability potential of correlation methods (damage correlation indexes) based on frequency domains in the impact damage detection fields of reinforced concrete columns were examined in the present study. In the current study’s experiments, four reinforced concrete bridge pier members of reduced scale were impacted by a new type of ultra-high drop hammer experiment system in order to simulate the processes of medium-sized trucks impacting bridge piers. The frequency response functions of the members before and after damages occurred were measured using an acceleration acquisition system. The experimental results revealed that the damage correlation indexes (DCI) taken into account the multi-order modal frequencies could be used to accurately identify the degrees of damage to the piers. In addition, an impact finite element model and a modal analysis method were matched with the experiments and were established using the commercial program LS-DYNA. Finally, the setting of the finite element parameters matching the experimental results was applied for the purpose of simulating the impact processes between the medium-sized trucks and the reinforced concrete piers. In order to meet the structural design requirements, a peak impact force (PIF) formula under vehicle impact conditions was proposed based on the damage indexes.

Experimental investigation on seismic performance of severely earthquake-damaged RC bridge piers after rapid strengthening

Experimental investigation on seismic performance of severely earthquake-damaged RC bridge piers after rapid strengthening

RC Bridge Oscillation Memristor Chaotic Circuit for Electrical and Electronic Technology Extended Simulation Experiment.

The fourth basic circuit component, the memristor, has been proposed for a long time, but it is not mentioned in the experiment teaching system of Electrical and Electronic Technology. In this paper, an RC bridge oscillation chaotic circuit based on memristor is designed to solve this problem. The dynamical behavior of the circuit system is analyzed using Lyapunov exponents spectrum, bifurcation diagram, phase portrait and Poincaré map. A series of complex dynamical behaviors such as symmetric single-scroll coexistence, asymmetrical single-scroll coexistence, symmetric double-scroll coexistence and asymmetrical limit-cycle coexistence exist in the circuit system. This research plays a critical role in enriching students' knowledge and improving the experiment teaching system of Electrical and Electronic Technology.

Seismic design and performance analysis of bridge bents retrofitted with multistage buckling-restrained braces

Buckling-restrained braces (BRBs) are often used to retrofit RC bridge bents to increase their strength and stiffness, and dissipate the seismic energy through hysteretic behavior. However, the post-yielding stiffness of BRBs is very low, and the total stiffness of the retrofitted bent drops sharply when the brace yields, which can lead to more serious damage to the primary structure contrary to the design purpose. Accordingly, multistage buckling-restrained braces (MSBRBs), consisting of steel cores with different yield strains, were used for the seismic retrofitting of bridge bents in this study. By controlling the low yield point (LYP) core yield before the bridge bents and high yield point (HYP) core yield after the bents, the expressions for the steel core length related to the geometric parameters of the bridge bents were derived. Furthermore, a preliminary seismic design method based on the structural fuse concept was proposed, which realized that the MSBRB dissipates energy while providing stable stiffness to improve the safety of the entire system. The advantages of the MSBRB in controlling the peak and residual displacement of the RC bent were proved via nonlinear time history analyses. Finally, the effects of the stiffness ratios, yield displacement ratios, and different configurations on the seismic performance of retrofitting bridge bents with MSBRBs were examined. The results showed that seismic performance of reinforced bents can be improved by increasing the stiffness ratio appropriately. The LYP core is primarily related to the energy dissipation capacity of the MSBRBs, and the value of βL should be less than 0.5. The HYP core is largely responsible for controlling the deformation of bridge bent, and βH must be greater than 1.0. Compared to other configurations, the diagonal MSBRB system has a greater energy dissipation capacity and higher seismic reduction rate.

Operational Modal Analysis as a Support for the Development of Digital Twin Models of Bridges

Many transportation infrastructures all around the world are facing new challenges in terms of ageing and loss of performance. The infrastructural asset managers are required to perform scrupulous control of the health condition of the infrastructures over time and to execute the required maintenance works. In this context, digital twin models of the infrastructures should have a key role to simplify and speed up the procedures for proper maintenance. This paper discusses the advantages of developing digital twin models for the management of infrastructures, with a focus on bridges. In particular, the role of dynamic tests performed on bridges for the development of digital twin models is addressed, paying attention to test procedures and requirements. Issues such as the quality of instrumentation, the numerosity, and layout of sensors, and the acquisition and post-processing procedures are addressed through applications to two real bridge case studies. Both infrastructures are multi-span pre-stressed RC bridges that were dynamically tested after the restoration and seismic upgrading works. Results of ambient vibration tests and operational modal analyses are described, providing an idea of dynamic test requirements, as well as their use within the framework of the digital twin model creation.

Analysis and design of mechanically spliced precast bridge columns

Reinforcement continuity in concrete members is traditionally achieved through lap splicing. An alternative is to use couplers to mechanically connect bars. Mechanical bar splices have been used in conventional and accelerated bridge construction (ABC) applications usually in capacity-protected and/or non-seismic members. Nevertheless, couplers are not currently allowed in the US national design codes to be used in the plastic hinge region of bridge columns in high seismic regions mostly due to uncertainty on their structural effects. This ban has also prevented the use of couplers as an ABC bent connection. A comprehensive analytical study was carried out to determine the effects of bar couplers on the RC bridge column seismic performance, specifically displacement capacities and demands. Modeling methods were proposed and validated against multiple test data. Subsequently, more than 950 pushover and nonlinear dynamic analyses were carried out on mechanically spliced circular and square bridge columns using the validated models. The results from the pushover analyses showed that couplers can reduce the columns displacement ductility capacity up to 45 %. A trend between the coupler length, rigidity, and the column displacement ductility capacity was established. Furthermore, the effect of couplers on the column displacement demands was found to be less than 10 % compared with unspliced columns. Finally, available design methods for mechanically spliced RC bridge columns were evaluated using test data for eight large-scale bridge columns.

Cyclic Behavior of Rectangular Bridge Piers Subjected to the Coupling Effects of Chloride Corrosion and Bidirectional Loading

The degradation of seismic performance for RC bridge piers induced by chloride corrosion has previously been studied by treating the earthquake as a unilateral cyclic loading. Such studies do not consider the true response of the pier under the joint effect of corrosion damage and real multi-dimensional earthquake action. Thus, in the present study, the cyclic behavior of rectangular bridge piers subjected to the coupling effects of chloride corrosion and bidirectional loading was numerically investigated. First, the corrosion-induced deterioration of material mechanical properties is introduced. Second, the numerical model of two corroded piers is built and validated with the test results in the literature. Then, the time-dependent biaxial seismic performance of a rectangular bridge pier under the circular-shaped (CS) biaxial displacement pattern, square-shaped (SS) biaxial displacement pattern, uniaxial displacement in the X-direction (UX) pattern, and uniaxial displacement in the Y-direction (UY) pattern is analyzed using the validated model. The simulation results conclude that the trajectory of biaxial loading paths and corrosion levels significantly influence the peak force, deformation capacity, and dissipated energy of the piers. The biaxial loading path effect for the corrosive pier includes two stages with different biaxial force trajectory characteristics. Compared with the uncorroded pier, the corrosion level of 13.7% and biaxial loading induces up to a 40% reduction in strength and a 54% decrease in the residual ultimate displacement of the corroded pier. For the same corrosion degree, the dissipated energy under the SS biaxial displacement path is the largest among the four loading paths.

Seismic vulnerability assessment of reinforced concrete bridge piers with corroded bars

AbstractReinforced concrete (RC) structures located in aggressive environment, for example, RC bridge piers close to the sea and experiencing chloride attacks, may be exposed to an increased seismic vulnerability. This requires practical yet effective safety assessment strategies aimed to determine the seismic behavior by incorporating corrosion deterioration phenomena. An easy‐to‐use phenomenological model is here developed to describe the seismic behavior of corroded RC elements based on a fiber hinge formulation wherein the corrosion‐induced mechanical degradation of concrete and steel is implemented through appropriate constitutive laws at the fiber level. The developed fiber hinge formulation is first validated against experimental cyclic tests of corroded RC columns from the literature. Then, the proposed approach is used for the seismic vulnerability assessment of the Zappulla multi‐span viaduct (southern Italy), whose RC bridge piers (with a box‐shaped, two‐cell hollow rectangular cross section) are exposed to carbonation and chloride‐induced corrosion. A comprehensive in‐situ testing campaign is conducted for the mechanical characterization of the materials in the RC piers. Corrosion potential mapping, carbonation tests and tensile tests on corroded bars extracted from RC piers are critically interpreted to calibrate the constitutive laws of the fiber‐hinge model. Motivated by experimental findings, numerical seismic analyses (including linear dynamic, nonlinear static and nonlinear dynamic analyses) are performed under two different corrosion scenarios to quantify the impact of corrosion on the resulting seismic vulnerability conditions of bridge piers with corroded bars. The proposed approach is characterized by low computational cost and lends itself to large‐scale seismic vulnerability assessment of other existing RC bridges placed in corrosive environment.

Fragility Assessment of RC Bridges Exposed to Seismic Loads and Corrosion over Time.

A methodology to estimate the structural fragility of RC bridges, considering the effects of seismic loadings and corrosion over time, is presented. Two scenarios are considered: (a) The structure is exposed only to seismic loads, (b) Both the effect of corrosion and seismic loads are present in the system. The uncertainties related to material properties, structural geometry, seismic occurrences, corrosion initiation time, cracking and corrosion evolution are considered. Different time stages, such as 0, 50, 75, 100, and 125 years are selected to evaluate the effect of both seismic loads and seismic loads plus corrosion. The calculation of fragility curves implies a structural design, nonlinear modeling of structures with simulated properties, estimation of both corrosion times and seismic occurrences, and evaluation of structural demand over time considering the effect of seismic loads and corrosion. An illustrative example is provided on an RC continuous bridge with AASHTO beams, cap beams and circular columns located in Acapulco, Guerrero, Mexico. A performance level equal to 0.002 is chosen for the design of the structure. Results show that the probability of exceeding the design performance levels for both cases (seismic and seismic plus corrosion) are similar at the stage of time equal to zero (a newly built bridge). However, such probabilities, after 150 years, are equal to 0.61 and 0.85 due to the cumulative damage caused by seismic and seismic plus corrosion, respectively. The estimation of the probability of exceeding a certain performance level, considering the effect of corrosion together with seismic loads, highlights the importance of considering more than one type of solicitation for these kinds of structural systems. Lastly, recommendations about design are given.

<i>Retracted: </i>Performance of Grouted Coupler Embedded in Reinforced Concrete ABC Bridge Pier at Vehicle Impact

Increased occurrence of dynamic loading on bridge piers caused by seismic, blast and vehicular impact incidences have been increasingly reported. Statistical data shows that while seismic and blast have received significant attention in the literature, whereas the frequency of occurrence of vehicular impact is remarkably higher but contemplating little consideration. With the newer construction methods like accelerated bridge construction (ABC) and its response against vehicle impact performance needs an additional study before widespread use. Static and dynamic performances of the coupler are investigated. A representative circular RC bridge with circular cross-section is considered and hollow cylindrical splice-sleeves filled up with concrete grout is embedded in the foundation. Finite element model (FEM) of single grouted coupler is developed based on the manufacturer data. Apportioned load through load ratio is considered and applied to the individual coupler. Numerical simulations are also performed using commercial finite element software package, ANSYS. This research is led by mesh independent studies to precisely accomplish sensitivity analyses. The results from numerical simulations are compared with the corresponding analytical solution. Stress-strain resulted from conservative dynamic simulation are plotted followed by integrity analyses to capture material performance at high deformation. Quasi-static strain rates are utilized for steel re-bars with connected coupler and validated with the finite element (FE) results to determine dynamic impact factor (DIF) of steel. This is further validated through utilizing experimental data from published journal. This study instills a good agreement by providing valuable information to aid in the selection of appropriate coupler connections, addressing material properties at various performance level, and contributes useful guidelines for the researchers, practitioners, and structural engineers.

Time-dependent reliability calculation method of RC bridges based on the dual neural network

Time-dependent reliability calculation method of RC bridges based on the dual neural network

Machine Learning-based Seismic Fragility Curves for RC Bridge Piers

A significant part of ongoing studies in the field of earthquake engineering is directed toward the seismic risk assessment of buildings and infrastructures at a territorial scale. This task is usually accomplished by grouping the structures into homogenous classes in terms of typology, for which seismic fragility curves are then obtained for different limit states via numerical simulations or from the statistical analysis of observational data when available. Particularly, the development of typological fragility curves for bridges under earthquake is useful for assessing the reliability and resilience of transportation networks in seismic areas and can be also effective decision-making support. Within this framework, the proposed study establishes a machine learning-based paradigm for the closed-form prediction of the main statistical parameters required to obtain relevant seismic fragility curves for reinforced concrete bridge piers. Initially, a huge training dataset has been obtained by Monte Carlo simulations and displacement-based bridge pier assessments by assuming data representative of the Italian highway transportation network. Next, symbolic nonlinear regression formulae for estimating the main statistical parameters of seismic fragility curves have been generated. With the aid of those formulae, the effort of calculating the seismic fragility curves is greatly reduced since the corresponding main statistical parameters can be directly calculated from a set of commonly available attributes. Therefore, the proposed study provides a helpful tool for the rapid preliminary assessment of damage and risk level of existing highway transportation networks exposed to seismic hazards.

Full-scale Field Test Extraction of Natural Frequency and Acceleration of Bridge using Modal Test and Operational Modal Analysis

Vibration in bridges occurred due to several factors such as structural design, environmental loadings, and loading characteristics (speed parameter, loading patterns, and configuration of axles). If this problem is prolonged for several years, this may lead to stages of failure such as structural cracking, fatigue on structural members, excessive deformation, and local stress concentration on structural connections. In response to this issue, an investigation was carried out in this study by utilising numerical modelling of Finite Element Analysis (FEA) to explore the effect of the Intermediate Diaphragm (ID) on the RC bridge deck. The FEA is then validated and confirmed from the full-scale field-test, which consists of a modal test for both frequency and mode shape comparisons, and operational modal analysis for extraction of deck acceleration. The results show that the current natural frequency of the bridge does not reach the minimum frequency requirement from the BS5400 Code of Practice, while the acceleration based on a 24-tonnes moving truck is within the allowable acceleration limit. In comparison, frequency, mode shape and acceleration between the FEA numerical analysis and field test had shown insignificant differences and minimum error between the two.

Durability enhancement of half-joints in RC bridges through external prestressed tendons: The Musmeci Bridge’s case study

This paper numerically investigates the effect of post-tension interventions to strengthen the deteriorated half-joints of the Musmeci Bridge in Potenza (Italy), with the primary objective of increasing the ultimate load-bearing capacity and monitoring the secondary effects in terms of preventing or limiting cracking patterns. Bearing this in mind, the study aims to investigate the role of the reinforcement detailing, of the post-tension stress and of the corroding time in the presence of chlorides, outlining the intervention ability to improve the structure’s durability. To this end, nonlinear finite element models are provided with chloride ions diffusion analysis to investigate corrosion initiation and progress in reinforced concrete elements and account for deterioration due to two scenarios (45 and 95 years). Results show the significant impact of reinforcement layout as the presence of inclined bars increases the ultimate load by about 86 %. The ultimate load improvement is in the range 50–55 % when the intervention is carried out after 45 years while it is equal to about 30–35 % if a period of 95 years is last since the construction. This latter highlights the significant influence of the intervention timeliness on structural durability.

Nonlinear Static Pushover Analysis of Hollow Shear Critical RC Bridge Piers Under Monotonic Loading: A Comparitive Study

Hollow RC bridge piers exhibit several failure modes when subjected to extensive time varying loads during their service lives. Shear failure of hollow RC bridge piers is very critical as it is brittle in nature involving rapid deterioration of strength with increasing widths of the shear cracks and low ductility. Hence this type of failure is not desirable in the earthquake prone areas. Simulation models that can accurately predict the characteristic load deflection curve parameters (including yield load, peak load, ultimate load and corresponding drift, ductility and post peak strength degradation) are very much essential for efficient design of these structures. In the present study, a nonlinear static pushover analysis of three hollow rectangular RC bridge piers (one flexure critical and two shear critical) has been performed under monotonic loading using four different analysis techniques. The first type of simulation model used in the present study is based on the commonly used fiber based nonlinear beam-column elements with simple uniaxial material constitutive relationships, which are very effective in predicting the flexural response of bridge piers. The second type of simulation model used in the present study is also based on simple fiber based nonlinear beam-column elements. However, the constitutive relationships of steel in this model are modified to predict the post-peak strength degradation in shear critical bridge piers. The third type of simulation model is based on two dimensional (2D) CSMM based smeared RC plane stress elements. The fourth type of simulation model is an analytical model based on the sectional analysis method. The load deflection curve properties obtained from all the simulation models have been compared with each other and also with the experimental data. It has been concluded from the present study that all four models are equally efficient in predicting the behaviour of flexure critical bridge pier. However, in the case of shear critical bridge piers, predictions from the 2D CSMM based simulation model are more accurate.

Modelling the Cyclic Response and Development of the Backbone Curve of Corroded RC Bridge Piers

Modelling the cyclic response for the evaluation of the seismic capacity of existing corroded RC bridges is important as it is well recognised in literature. Procedures exist in the literature for the inclusion of corrosion effects through variation in different parameters like cross-sectional area of reinforcement, stress–strain behaviour, yield strength, ultimate strength and elastic modulus. In the present study, change in the inelastic buckling behaviour of reinforcement and variation in the core concrete damage characteristic under different levels of corrosion are also modelled in detail with OpenSees computational software. Modelling procedures for pristine and corroded bridge piers are validated by comparison of the cyclic response results and backbone curves obtained from analytical modelling with the experimental results reported in the literature. In this paper, the procedure for the cyclic response evaluation of piers for different mass loss percentages for corrosion has been demonstrated. From cyclic response results, the backbone curves for corroded bridge pier specimens are developed for different mass loss percentages of corrosion. The modelling strategy proposed in this paper for the cyclic response evaluation of bridge piers can be adopted for quantifying the effect of corrosion on the cyclic response of similar important structures.