Behavior Of Bridge Research Articles

A Machine Learning Model to Predict the Seismic Lifecycle Behavior of a Cross-Sea Cable-Stayed Bridge

Cross-sea cable-stayed bridges encounter challenges associated with cable corrosion and cable-force relaxation during their service life, which significantly affects their structural performance and seismic response. This study focuses on a cross-sea cable-stayed bridge located in Hainan Province. Utilizing an LSTM deep learning model, this study aims to fill in the gaps in short-term cable-monitoring data from the past year using the available cable-force-monitoring data from the same period. The authors of this study interpolated the cable-force data in the absence of sensors and employed a SARIMA machine learning time-series-prediction model to predict the future trends of all cable forces. A finite-element model was constructed, and a dynamic time-history analysis of the seismic response of the cross-sea cable-stayed bridge was conducted, considering the influence of cable-force relaxation and cable corrosion in the future. The findings indicate that the LSTM-SARIMA model predicted an average decrease of 11.81% in the cable force of the cable-stayed bridge after 20 years. During the lifecycle of the cables, cable corrosion exerts a significant impact on the variation in cable stress within the bridge structure during earthquakes, while cable-force relaxation has a more pronounced effect on the vertical displacement of the main beam of the bridge structure during seismic events. Compared to when using the traditional model that only considers cable corrosion, the maximum negative vertical displacement of the main beam increases by 29.7% when using the proposed model if the earthquake intensity is 0.35 g after 20 years, which indicates that the proposed machine learning model can exactly determine the seismic behavior of the lifecycle cross-sea cable-stayed bridge, considering the impacts of both cable-force relaxation and cable corrosion.

Experimental investigation on shear behavior of PVA-ECC keyed joints

Keyed joints play a critical role in ensuring the overall behavior of a precast concrete segmental bridges. However, these joints can exhibit poor shear capacity and durability as well as brittle failure. Polyvinyl alcohol fiber-reinforced engineered cementitious composites (PVA-ECCs) exhibit high shear strength and ductility as well as excellent fracture performance, making them attractive for use in the joints of segmental bridges. This study fabricated 16 Z-shaped specimens with number of keys (one, two, or three), concrete materials (normal concrete or PVA-ECC), and types (monolithic, epoxy, or dry) to investigate their failure modes, cracking loads, shear capacities, residual capacities, and shear stress–vertical displacement curves. The results indicated that the keyed joints exhibited shear failure at the root of a shear key, and an increase in the number of keys increased the residual strengths and ductility of both the dry and epoxy joints, but it had a negative effect on the shear strengths. When PVA-ECC was applied instead of normal concrete, the cracking resistance index for all joints improved significantly and the shear strengths and ductility of the monolithic and keyed epoxy joints increased. Generally, the shear strengths of the epoxy joints were 6.3–29.1% higher than those of the corresponding dry joints; however, the ultimate displacements of the epoxy joints were 46.6–72.4% lower. Finally, a method for calculating method of the shear capacities of keyed PVA-ECC joints was proposed and verified to accurately predict the behaviors of previously tested joint specimens.

Effect of Geometry and Size of Fiber Reinforced Plastic Deck Profile on Behavior of Bridges

Due to the important role that bridges play in rescue operations after an earthquake, it is necessary that these structures have a higher level of protection against seismic attacks. Earthquake identifies the weak points of the structure and causes the most damage there. Bridges are very vulnerable to these attacks due to their low degree of uncertainty. All bridges built before 1971 were designed with the elastic design method (permissible stress). In this method, the effects of plasticity, section cracking, and plastic deformation are not taken into account. The change of seismic locations based on the principles of elastic design is much less. It is because the structure experiences in a real earthquake, one of the consequences of which is the falling of the decks due to the loss of the support surface. The decision to strengthen the bridge was made when there were many bending and shear cracks on the king beams. The bridge was created. The use of FRP profiles can significantly prevent the damage caused by corrosion and is a good alternative to the traditional methods of strengthening the structure. In this study, a design for the deck of a steel bridge with I beams is presented. The shape of reinforcement using FRP fibers with vinyl ester resins has also been investigated, the effect of the geometry of FRP profiles has been investigated. The presented specifications are optimized to obtain a lasting shape and section, especially for the pultrusion process. FRP materials are light, resistant to corrosion and have high tensile strength. These materials come in different forms and range from multi-layer factory sheets to dry sheets that can be twisted on various structural forms before adding resin, is available. The durability and high tensile strength of FRP materials are among the advantages of these materials. The durability and long-term performance of FRP requires more research, which is ongoing and continues.

Stability analysis of long-span bridge under static wind load

With the maturity of various technologies and the vigorous development of advanced materials, the design and construction of suspension bridges require larger spans and lighter structures, but at the same time, the problems arising from the dynamic and static responses of the system under wind loads have become more and more prominent. The phenomenon of wind-induced static response occurring before the emotional response has been found in wind tunnel tests at home and abroad. Static instability is also a vital issue in the wind-resistant design of large-span suspension bridges, so studying the static behavior and instability law of large-span suspension bridges under strong winds is of high practical value for the construction of large-span bridges in the future. In this paper, relevant research results of previous researchers based on static wind stability of suspension bridges are sorted out and summarized. Their corresponding fundamental theories are introduced in detail. In addition, the related analysis program is prepared by using the APDL language of ANSYS.

Tailor-joining of Ti6Al4V skin with V-shaped assembly error using enhanced PLBW scheme: Keyhole dynamics and metal bridging behavior

Building thin-walled titanium alloy skin using conventional laser beam welding (LBW) frequently suffers from undesirable seam quality due to the V-shaped notch; a typical assembly error occurs after skin rolling with a specific sheet thickness range. This work proposed an improved scheme with metal bridging capacity and liquid film stability to overcome this by executing a pulsed laser beam and spot irradiation in a flat-top mode. Welding was performed on 1.5 mm-thick Ti6Al4V sheets configured in the butt joint with a reserved notch geometry, which is 20 degrees between the groove surface. We also conducted numerical modeling and solutions concerning the heat-flow-phase dynamics using an enhanced ray tracing algorithm. Results show that the as-build weld beads, characterized by middle rippers, slight depression, and edge ridges, present superb continuity and uniformity when applying an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. Effective metal bridging across the notch error is achieved at both pulse duration and interval phases due to not only the complete melting of welding side but also the enhanced melt film stability against the surface tension. The cooling of the weld pool starts with a sharp temperature drop at ∼3×105 K/s (on average) during the keyhole collapsing regime, then slows down due to the damped up-down oscillation of the free surface combined with the natural convection-conduction effect. The flow pattern of molten metal changes from squeezing-like to vortexes and finally to a backfilling mode, depending on the evolution of keyhole geometry. Although the keyhole dynamics differs, various process conditions regarding heat input and pulse energy yield effective metal bridging of a single weld spot and sufficient refusion between the adjacent weld spots, ensuring the well-overlapped weld bead formation.

Insights into structural assessment and long-term effects of a post-tensioned multispan concrete box girder bridge with vertically prestressed internal joints

The study focuses on multi-span prestressed bridges, where time-dependent effects like creep, shrinkage and prestress losses can have a significant impact on long-term behaviour. Specifically, the paper analyses a bridge constructed with the balanced-cantilever method and presenting the peculiarity of vertically prestressed internal joints, which significantly influence the deformed shape and require proper modelling approaches. The testing campaign is fundamental to achieve a deepened awareness of the actual behaviour of the bridge and to correctly reproduce it through a Finite Element (FE) model. The constructed FE model accurately predicts actual and future deformations and stresses, and allows simulating the actual service conditions of the structure. The novelty of the work presented in this paper lies in the development of a detailed model specifically tailored for the analysed bridge typology, considering real construction stages and long-term phenomena of both steel and concrete. The model has reached a high level of validation through the comparison of the results with extensive in-situ tests and theoretical formulations, so as to be able to achieve insights and learn important lessons on the long-term structural behaviour of post-tensioned bridges with special internal connections.

Modeling and Analysis of 1:3 Internal Resonance of Suspension Bridge Under Boundary Excitations

This study investigated the nonlinear dynamic behavior of suspension bridge subjected to multi-frequency boundary excitations. Firstly, the nonlinear dynamic model of the suspension bridge subjected to multi-frequency boundary excitations is established. The in-plane vibration equations are derived based on Hamilton’s principle, taking into account the effects of geometric nonlinearity of the girder-deck and main cable as well as the stiffness of hangers. Secondly, the Galerkin method is used to solve for the frequencies and corresponding mode shape functions. Thirdly, the corresponding modulation equations are obtained based on the multiple scales method, and the 3:1 internal resonance between two symmetrical modes is analyzed. Combined with numerical analysis, the nonlinear dynamic behavior between modes of the suspension bridge is demonstrated through the frequency–response, force–response, and time history curves. The results indicate that the drift phenomenon appears when perturbing the amplitude and frequency of the different excitations, and the system exhibits intricate dynamic responses.

Influence of Mechanical Properties of Dental Implants on Biomechanical Behavior: A Three-Dimensional Finite Element Analysis

In the context of this numerical study is particularly to analyze and observe the effect of mechanical properties and masticatory efforts on the intensity and distribution of biomechanical stresses induced in the mandibular bone (the cortical bone, the spongy bone) and in the elements which constitute the structure of the dental bridge (abutments, implants, bridge). The 3D model studied is subjected to loading in the three directions of space (corrono-apical, disto-medial, bucolingual). The numerical analysis allowed us to highlight the localization of the stress concentration zones, on the one hand, at the level of the regions of contact between the elements of the dental bridge structure and on the other hand, at the level of the mandibular bone. This parametric approach for the mechanical properties of bridges is used to better visualize and quantify the biomechanical behavior of dental bridges.

Phase shift-based resonance assessment for in-service high-speed railway bridges

Resonance in high-speed railway bridges can deteriorate the structural integrity and running safety of a train; thus, the resonant speed needs to be identified. Previous studies have proposed resonant conditions analytically, but their applications to in-service bridges are limited. Free vibration after the passage of a train was utilized to assess resonance, but it could not capture the natural frequency of the coupled system because the train-bridge interaction was neglected. This study proposed a practical framework for quantifying the resonance in a high-speed railway bridge using a phase shift. The static displacement of the railway bridge was numerically reconstructed using the train loading history. Phase angles were extracted by comparing the static and dynamic displacements, which were directly utilized to develop a novel resonance indicator in this study. Numerical simulations and field demonstrations validated the applicability of the proposed method for understanding the resonance behavior of full-scale railway bridges.

Novel block element with axial-only deformation for limit analysis of masonry arch bridges

This paper proposes a novel limit analysis block element to model the ring behavior in masonry arch bridges, with consideration of axial deformation induced by both bending and axial compressing motions. The governing formulation is established based on the kinematic theorem. After constructing the velocity field of the block element, the new compatibility condition is put forward, followed by a discussion of possible linearization for the element constitutive model. A new heterogeneous limit analysis formulation that accounts for the deformability of the elements is given at the end. For benchmarking purposes, the collapse of an 80-block arch is first investigated to understand the influence of using different constitutive linearizations. Then, the proposed element is applied to analyze the collapse of a practical bridge involving arch-fill interactions. The results indicate a great necessity of considering the deformability of the ring when analyzing the collapse of masonry arch bridges. Compared with previous experimental results of Prestwood Bridge, employing the rigid modeling for the ring will lead to a significantly overestimated load prediction (about 46.3%) while the proposed deformable brick element with quadrilateral-linearized constitutive can produce a very accurate prediction (bias within 1%). Adoption of the hexagon linearization will give rise to a comparatively inflexible block behavior and the corresponding ring performs analogous to the rigid case. Finally, the model proposed gets over the main shortcoming exhibited by a beam discretization of the ring, namely the potential over-flexibility of the bridge arch, induced by the simplification of the actual geometry.

Elastic-plastic flexural behavior of hybrid steel girder bridge considering welded residual stress

Hybrid steel girders use a section type that fully utilizes the strength performance of steels, which are widely used in steel plate girder bridges with multiple spans. In this paper, the distribution of the welded residual stress in hybrid I-shaped steel girders was investigated by the hole drilling test, and the unified model was analyzed and revised. Considering welded residual stress, the elastic and plastic design method for calculating the flexural capacity of hybrid I-shaped steel girders was put forward. Experiments and numerical simulations were conducted to analyze the elastic-plastic flexural behavior of the hybrid I-shaped steel girders using multi-scale models. The influence of welded residual stress, geometry of section, steel grade, and initial geometrical imperfections on the elastic-plastic flexural capacity of hybrid I-shaped steel girders were discussed through the parameter analysis adopting the dimensions commonly used in bridges. Analysis results show that the welded residual stress reduces the value of the elastic and plastic bending moments by almost 25% to 40% and 3%, respectively. The geometry of the section should be paid attention to clarify the value of the flexural capacity of the hybrid I-shaped steel girder. The width-to-thickness ratio limit of the flange should be adjusted according to the severity of initial geometrical imperfections.

Mode Shape-Based Damage Detection of Twin Skewed Bridges Based on OMA and FE Model Updating

A comparative study of the dynamic behavior of twin single-span bridges was carried out based on operational modal analysis and a linear finite element model updating with the aim of finding a potential damage indicator. The bridges are skewed, 30 m long and with prestressed concrete girders as the main support structure, but one of them were collided and suffered damage in two of its I-shape girders. Ambient vibration tests were conducted by deploying 14 uniaxial accelerometers along the sidewalks, experimental modal parameters were identified using the COVariance-driven Stochastic Subspace Identification method (SSI-COV). Six vertical modes were clearly identified for each structure. Additionally, some extra modes with non-proportional damping were identified. It was found that the modal frequencies are sensitive to the support conditions and the overall stiffness of the bridge but not to the localized girder damage, which, on the contrary, is reflected in the discrepancy in the fundamental bending mode shape amplitude between the lateral sides of the bridge, and a so-called Continuous Symmetry Measure adopted as a symmetry index seems to be a good damage indicator for this type of straight-alignment simply supported bridges, given the symmetric nature of the bending mode shapes and the asymmetric nature of the damage.

Thermal deformation monitoring of a highway bridge: combined analysis of geodetic and satellite-based InSAR measurements with structural simulations

Structural Health Monitoring (SHM) of civil engineering structures is experiencing an increasing progress in the last decades. The present work focuses on the static behavior of a highway bridge due to environmental temperature effects. The goal of the present study was to test the applicability of the satellite-based synthetic aperture radar interferometry (InSAR) for deformation monitoring of a large, curved highway bridge and to compare the obtained results with alternative measurement techniques like classical geodesy surveying and with an advanced computer simulation. Such a comparison is quite rare and provides an important insight into the accuracy, efficiency and limitations of the InSAR technique in the context of SHM. Especially interesting was the question whether the InSAR technique is suitable for blind monitoring of a cluster of bridges in the region of interest. The present study shows that a pre-knowledge about each structure can be very important for a reliable interpretation of the InSAR measurement results. The second challenge of the study was to overcome several objective difficulties of combining and comparing quite different monitoring techniques that result from different sampling rates, measurement points and other specific features and sensitivities. Nevertheless, a suitable approach has been developed and implemented in the present study for the InSAR and total station measurements, providing new results and important knowledge about novel SHM techniques.

Experimental investigation of dynamic behaviour of pile-supported bridges in sandy deposits

This paper presents the results of centrifuge tests performed on reinforced concrete (RC) pile–supported simply supported girder bridge models in non-liquefiable (unsaturated) and liquefiable (saturated) slightly inclined sandy soil sites. The main objectives were to investigate the dynamic response characteristics of RC pile–supported simply supported girder bridges in non-liquefiable and liquefiable soils, examine the mechanisms causing beam collapse and damage to pile–pier yielding, and verify the effectiveness of cable restrainers. The centrifuge tests were conducted in non-liquefiable and liquefiable sites, each consisting of a three-span RC pile–supported simply supported girder bridge model and a control model with a superstructure equipped with a cable restrainer. First, the dynamic characteristic parameters of the soil and structural models in both sites were obtained. Subsequently, the conventional test results were interpreted, including the excess pore pressure ratio, acceleration, and displacement. The analysis included examining the moment demand of the pile–pier structure and seismic damage mechanisms. Finally, a correlation analysis was performed to evaluate the inertial and kinematic effects on the moment demand of the pile–pier structure. The results show that the acceleration response after soil liquefaction at the inclined sites is amplified unilaterally in the downslope direction and spikes appear. The liquefiable foundation is displaced to the downslope. However, major earthquake induces foundation displacement, and liquefaction leads to a longer duration and more significant soil displacement. The installation of cable restraints significantly increased the acceleration response of the superstructure. Still, it effectively reduced the relative displacement of the superstructure and prevented the beam from collapsing. Soil liquefaction decreases the bending moment of the pile–pier structure, and the cable restrainer causes the damage mode of the pile–pier structure to shift from the pile head to the pier bottom. In the non-liquefiable scenario, the bending moment demand at the pile head has a more significant influence on the inertial effect. Additionally, using the cable restrainer system can increase the kinematic effect after liquefaction. The test results can be used to validate numerical models and provide a reference for pile foundation design.

Shrinkage and creep effect analysis of beam-arch composite bridge based on field test

To study the time-dependent behavior of the beam-arch composite bridge under the effects of shrinkage and creep, this paper conducted field tests on C55 concrete with different reinforcement ratios at the bridge site environment. Based on the experimental results, the commonly used CEB-FIP-90 model in engineering was modified, and new shrinkage strain and creep coefficient values were proposed. These modifications allowed for an analysis of the long-term performance of the bridge. Finally, the influence of the arch rib stiffening on long-term performance was discussed. The results indicate that the modified model aligns better with the actual structure compared to the CEB-FIP-90 value. During the operation stage, the bridge exhibits an overall significant compressive stress reserve. Specially, it is worth noting that the concrete footings experience tensile stress, which indicates a risk of cracking during the operation stage. Furthermore, the deflection of the beam-arch composite bridge is 1/7 of that of the continuous rigid frame bridge while the stress distribution in the beam-arch composite bridge is more uniform. This paper provides important reference value for the maintenance and management of beam-arch composite bridges during their operation period.

Study of the Impact of Varying Inclination Angles of Arch Ribs on the Seismic Behavior of Half-Through Steel Basket-Handle Arch Bridge

In the present study, multiscale finite element (FE) models of half-through steel basket-handle arch bridges were established. The eigenvalue analyses were conducted to explore the dynamic characteristics of the arch bridges based on the FE models. In addition, a parametric analysis was carried out to investigate the impact of the inclination angle of the arch rib (0°, 4°, and 7°) on the longitudinal and transverse seismic performances of arch bridges. The results show that with the increase in inclination angle, the out-of-plane stiffness of half-through steel basket-handle arch bridges increases, resulting in the natural period of the structure becoming shorter from 3.09 s to 2.93 s. Adjusting the inclination angle appropriately has a beneficial impact on the overall seismic performance of the structures, affecting both displacement and internal forces, in which the most significant improvements include a 42.8% decrease in displacement and a 62.6% reduction in internal forces. Adjusting the inclination angle can cause the arch springing and transverse brace to undergo larger plastic deformation. It is advisable to judiciously enlarge the sectional dimensions and enhance the material strength of both the arch springing and the transverse bracing in seismic designs.

Structural Condition Assessment of Reinforced Concrete Bridge Using Operational Modal Analysis and Finite Element Model

The integration of Operational Modal Analysis (OMA) and Finite Element Model (FEM) techniques has proven to be a valuable approach for evaluating and maintaining the health of such structures. OMA extracts dynamic characteristics from a bridge's responses to ambient vibrations, while FEM employs computational models to simulate and compare these dynamic behaviours. This comprehensive methodology ensures an accurate representation of the bridge's behaviour and its correlation with real-world conditions. However, a significant challenge arises in assessing the Ultra High Performance Fiber Reinforced Concrete (UHPFRC) pedestrian bridge in Klang, Selangor, launched in October 2022, due to limited available information about OMA and FEM on UHPFRC. This research aims to develop FEM and conduct ambient vibration tests to obtain modal parameters. Moreover, the study investigates OMA techniques in the context of weak excitation sources, filling a critical knowledge gap. By comparing experimental results with FEM, this research provides insights into the feasibility and reliability of OMA under challenging environmental conditions. The principal results reveal significant percentage differences in natural frequencies between FEM and OMA, with the most notable disparities occurring in the first mode. Nevertheless, the mode shapes extracted from OMA closely resemble those from FEM. In conclusion, this research enhances the understanding of UHPFRC pedestrian bridge behaviour and modal analysis techniques.

Detecting deck damage in concrete box girder bridges using mode shapes constructed from a moving vehicle

Longitudinal cracks at the bottom of the deck are a common form of hidden damage in box girder bridges. Timely detection of deck cracking is critical to ensure the safe operation of box girder bridges. This paper proposes a damage detection method for the deck of box girder bridges using mode shapes constructed from a moving vehicle. One stationary excitation vehicle excites the local bending modes of the deck, and the other vehicle moves along the planned path. The moving vehicle acceleration is collected to construct mode shapes on the driving path. First, generalized beam theory is used to analyze the dynamic behavior of the box girder bridge. The theoretical model of the proposed approach is built to analyze the response of the vehicle-bridge system under shaker excitation, and mapping relationship between the instantaneous amplitude of the vehicle response and the local bending mode of the deck is deduced. The damage indicator based on the mode curvature is used to determine the crack position. Then, a damage detection process for field testing is proposed. Technical details such as excitation parameters, driving path, and narrowband filtering are explained. Finally, factors that affect damage detection, including road roughness, crack length, and crack height are investigated via numerical analysis. Results show that the proposed method can detect medium damage.

Mechanical behavior and track geometry evaluation of long-span cable-stayed bridges with ballastless tracks

Ballastless tracks have been widely used in China’s high-speed railways; however, they have only recently been laid on 300 m-class cable-stayed bridges. For cable-stayed bridges with a longer span, the mechanical behavior of ballastless tracks is unclear, and the track construction acceptance method is incomplete, restricting the development of cable-stayed bridges with ballastless tracks. Taking four 300–1000 m-class cable-stayed bridges as research objects, this study established static track–bridge interaction models and dynamic vehicle–bridge coupled models. By evaluating static and dynamic indices, the feasibility of laying ballastless tracks and operating high-speed trains at 350 km/h on cable-stayed bridges was analyzed. Based on the results of dynamic analysis and track geometry evaluation, a 40 m chord was proposed for track geometry acceptance on cable-stayed bridges. The accuracy of the simulation results was verified through the measured data from the Xi-Cheng Railway. The numerical results showed that the 300–1000 m-class cable-stayed bridges with ballastless tracks had good static and dynamic characteristics. The 300 m baseline was unsuitable for the long-wave irregularity evaluation of tracks on cable-stayed bridges, and the 60 m chord was easily affected by wavelengths above 200 m, leading to misjudgment of the evaluation results. The 5 mm limits of the 40 m chord could be used for track geometry acceptance on cable-stayed bridges. Finally, a comprehensive evaluation method for track geometry, namely 10 m chord, 40 m chord, and minimum vertical curve radius, was formed.

Experimental Study on Transverse Seismic Behavior of Long-Span Cable-Stayed Bridge with Two Inverted Y-Shaped Reinforced Concrete Towers

ABSTRACT The transverse seismic behavior of a long-span cable-stayed bridge with two inverted Y-shaped reinforced concrete towers is investigated in this study. To accomplish this, a 1/35-scale model of a cable-stayed bridge with a span of 1088 m was designed, constructed, and tested until failure on four shake tables; the test was conducted at Tongji University, China. A site-specific artificial wave was applied in the transverse direction. Moreover, the input peak ground acceleration was increased from 0.1 g to 1.3 g until the test model failed. The transverse displacement, force, rebar strain, and curvature responses of the bridge model are obtained and studied. The test results showed that the transverse displacement response of the tower was significantly affected by high-order modes. This resulted in the maximum seismic displacement of the tower at the middle – upper level of the middle column except for the tower top. The ratio of the transverse seismic forces acting on the towers significantly exceeded that of the forces acting on the piers. In the final test case, severe damage, including concrete crushing and rebar exposure, occurred at the bottom of the middle column – the most critical part of the tower – leading to the inclination of the tower. Damage to the cables or deck was not observed. The finite element model captured the elastic transverse seismic behavior of the test model.