Deck Displacement Research Articles

Development of a Cable Assessment Method Based on Phase Space Trajectory for Cable-Stayed Bridge Under Moving Loads

This study emphasized the importance of structural health monitoring for assessing cable-stayed bridges, which are vulnerable to damage, particularly fatigue and corrosion in their cables. Cable tension has been evaluated using natural frequency analysis and a widely adopted vibration-based approach. These conventional methods often required traffic disruptions or even completed bridge closures. This paper proposed a damage detection method for cable-stayed bridge cables under moving loads at low speeds, which minimizes traffic disruptions. This research focused on the phase space method and deck displacement responses in the time domain. A benchmark cable-stayed bridge with a concrete deck and pylon was studied. Seventeen damage scenarios were defined, and two damage indices, change in phase space topology and Mahalanobis distance, were used to detect cable damage. The effectiveness of the phase space-based method for damage detection was validated on two steel cable-stayed bridges with different configurations. The results demonstrated that changes in phase space topology were highly effective at detecting one or two damaged cables. This method required only displacement data at cable-deck connection points, eliminating the need for sensors along the entire deck. This damage detection approach faced challenges with back-stay cables and cables near the pylons.

In-plane Rotation Response of Skewed Simply Supported Bridges Considering Multi-point Pounding Effect

Previous earthquake events have shown that the in-plane rotation of skewed bridges can induce multi-point pounding at longitudinal expansion joints and transversely between the decks and shear keys. These pounding phenomena may result in damage to girders and excessive deck movement. To explore the interaction between multi-point pounding and in-plane rotation response of decks in multi-span skewed simply supported bridges under seismic excitation, simplified equations for estimating bi-directional pounding forces were derived based on the force equilibrium principle. Finite-element models of skewed simply supported bridges incorporating pounding effects were developed, and time-history analyses were conducted to investigate the influence of skew angle, expansion joint width, and shear key capacity on the seismic response of bridges. The analytical results demonstrate the accuracy of the simplified pounding force estimation equations. The interaction mechanism indicates a positive feedback loop between multi-point pounding and in-plane rotation response, in which the two phenomena mutually amplify the responses. Parametric analysis reveals that the maximum seismic response can occur at a skew angle of 30°, an expansion joint width of 10cm, or a shear key capacity exceeding 20%. With increasing expansion joint width and shear key capacity, the multi-point pounding effect and in-plane rotation response can be mitigated. However, an excessive expansion width may induce greater deck displacements, and a higher shear key capacity can lead to damage in the piers.

Optimal replicator dynamic controller for semi active control of long span cable stayed bridge with considering special variability of seismic excitations

Cable-stayed bridges are lifeline infrastructures. However, due to their design and structural characteristics, they are sensitive to the vibrations. Thus, vibration control in these structures is essential. Semi-active control systems have gained significant attention due to their high performance and adaptability. However, the implementation of these systems has always faced serious challenges particularly when it comes to developing appropriate control algorithms because semi active devices have complex and non-linear characteristics. Inspired by evolutionary game theory, the author utilizes the replicator dynamic controller concept to optimize the performance of MR dampers to improve the vibration reduction of cable-stayed bridges. Two key parameters in the proposed control methodologies using replicator dynamics are the total population (total available resources or the sum of actuator forces) and the growth rate. Instead of using the sensitivity analysis that has been done in previous studies for vibration reduction of highway bridges using a replicator controller, the author used an evolutionary algorithm named the nondominated sorting genetic algorithm (NSGA-II) to create an optimal replicator dynamic controller for more effective vibration reduction. The proposed methodology is evaluated through its numerical application to a second-generation benchmark example based on the Bill Emerson Memorial Bridge, which considers a more realistic behavior of the cable-stayed bridge by accounting for multiple support excitations. The study indicates that the optimal replicator dynamic controller improves the vibration reduction performance of MR dampers. Specifically, deck displacement is reduced by 46 % compared to passive control system and shear forces at the tower base are reduced by 33 % compared to active control systems for the El Centro earthquake. The results indicate that the proposed Replicator Dynamic Controller optimized through NSGA-II provides a robust and effective solution for improving seismic resilience of cable-stayed bridges.

Over 25-year monitoring of the Tsing Ma suspension bridge in Hong Kong

Bridges in service are subjected to environmental and load actions, but their status and conditions are typically unknown. Health monitoring systems have been installed on long-span bridges to monitor their loads and the associated responses in real time. Since 1997, the Tsing Ma suspension bridge in Hong Kong has been the world’s first of the type equipped with a long-term health monitoring system. For the first time, this study reports the first-hand field monitoring data of the bridge from 1997 to 2022. The 26-year data provide an invaluable and rare opportunity to examine the long-term characteristics of the loads, bridge responses, and their relationships, thereby enabling the assessment of the bridge’s load evolution and structural condition over time. Results show that traffic loads have remained stable after 2007, highway vehicles kept increasing until the COVID-19 pandemic in 2020, the annual maximum deck temperature continued to increase at a rate of 0.51 °C/decade, typhoon durations increased by 2.5 h/year, and monsoon speeds decreased and became dispersed and variable. For the bridge responses, deck displacement is governed by the varying temperature. Natural frequencies in the past 26 years were almost unchanged. The overall condition of the bridge is very satisfactory. Current status and recent update of the health monitoring system are also reported. Lastly, prospects of bridge health monitoring are discussed. This study is the first to report the over one-quarter century status of a structural health monitoring system and the behavior of a long-span suspension bridge. This research provides a benchmark for many other bridge monitoring systems worldwide.

Probabilistic damage evaluation of isolated steel box-girder bridge excited by near-field earthquakes

Modern civilization regards bridges as lifelines, and their failure due to significant earthquakes in the past has raised concerns about their seismic vulnerability. The effect of near-fault earthquakes on the bridge vulnerability is a significant problem that has not been well explored. The present work utilizes fragility analysis to assess the probabilistic seismic risk evaluation of a continuous isolated steel box girder bridge exposed to near-field ground motions (NFGMs). Probabilistic seismic demand models (PSDMs) of the bridge are explored to reliably associate key demand and intensity measures to capture the seismic performance of the system. This study examines a steel box girder bridge in Guwahati, India, isolated with lead rubber (LRB) bearings and a friction pendulum system (FPS). To achieve a comparable seismic response, each bearing system is designed for a similar isolation period. The PGV/PGA ratio is a useful metric for classifying ground motion suites and estimating their frequency content by classifying the input excitations into low- and high-frequency motions. To perform probabilistic seismic risk assessments, two ensembles of forward directivity records with PGV: PGA >160 cm/s/g (high frequency) and PGV: PGA <160 cm/s/g (low frequency) are considered. Moreover, one ensembles of near-field incorporating the fling effect and far-field are also utilized. The failure probability under the seismic hazards for isolated bridges is assessed utilizing different damage measures (DM) such as maximum displacement ductility of pier (DDP), displacement of deck (MDD), drift ratio of pier (PDR), and rotational ductility (RDP). The near-field earthquake damage probability is significantly impacted by the PGV/PGA ratio, as a high PGV/PGA ratio results in a greater probability of damage than a low PGV/PGA ratio. In conclusion, guidelines are provided that will help the design engineers for designing bridges with LRB and FPS isolators for seismic isolation in the event of varying ground motion characteristics.

Large scale monitoring of a highway bridge with remote sensing and distributed fiber optic techniques during load tests

Many bridges in western countries are at the end of their lifetime and hence Structural Health Monitoring is vital to ensure their safe operation. Load test are one way to assess the utilization grade and to decide if actions have to be taken. We report on a comprehensive monitoring campaign of load tests of a large highway bridge on the Brenner highway. The Brenner highway is the main alpine truck crossing passages from Germany to Italy. Several different remote sensing techniques like static and dynamic laser scanning, robotic total station measurements and interferometric radar were used to determine displacements of the bridge deck and girders. Strain changes and bending were observed with distributed fiber optic sensing. Furthermore, the movements of the bridge bearings were determined with IoT tilt sensors. Data was acquired during static and dynamic load tests. We demonstrate that the utilization grade of the bridge can be assessed by an integrated analysis of the different sensor data in combination with a numerical model of the structure. As a consequence of the investigations it was decided by the highway operator to close one of the three lanes of the bridge.

Behavior of container berth structure under the influence of environmental and operational loads

Abstract Container docks, which are an essential component of the marine berth, are exposed to loads from various sources, such as self-weight, operation, and environment. In this study, four sets of combined loads to which the container berth is exposed were selected at the Um-Qaser Port in southern Iraq. The berth was constructed more than 40 years ago, which has to be verified according to latest specifications, and each set of combined loads was analyzed in three cases. In the first case, the piles were assumed to be fixed at the seabed, and in the second and third cases the piles were modeled as embedded in elastic and elasto-plastic sandy soil, respectively. The general-purpose finite-element software ABAQUS was used to model the various components to determine the maximum stresses, displacements, axial forces, shear forces, and bending moments due to dead, live, operate, berthing, mooring, waves, and seismic loads. It has been demonstrated that the impact loads of ships have a more significant impact on the structure compared to other loads. The calculated displacement when the piles are assumed to be fixed at the seabed level may be reduced by 50–94% of that calculated when the soil is modeled, meaning that assuming fixed piles yields inaccurate results, especially for deck displacements. However, this assumption was verified to yield reasonable results for shear forces at the pile head. It could also be noted that the elasto-plastic model of soil was more sensitive than the elastic model in displacement by 0.4–8% and bending moment by 0.3–34%, while it is less sensitive in axial force by 3–8%. The aim of this study is to obtain knowledge on the behavior and efficiency of container berth under the influence of different loads and the environmental conditions surrounding it.

Effects of dynamic load application, irregular wave conditions, and base flexibility on the structural response of a vertical pile platform

The dynamic structural response of a vertical pile port platform under the action of irregular wave loads considering soil-structure interaction is studied. Deck displacement and bending moment on the piles were evaluated for a set of structural, hydraulic, and geotechnical parameters. Static structural analyses with the maximum base shear produced by wave loads and dynamic time-history analyses are performed to study the effects of dynamic amplification on the structural response of the platform. Two types of waves are analyzed, regular and irregular, to analyze the amplification effects due to the superposition of a wave train of different periods in the case of irregular waves. Cases with fixed base support and non-linear spring-modeled soil are considered to evaluate the effect of considering a flexible base for the platform. Eight structures composed of a different number of piles and with different heights were analyzed. Six wave conditions with different characteristics are used, varying the wave period and mean water height. Two sandy and two clayey soil profiles are considered with different densities and consistency. The results show that resonance effects associated with dynamic loading and small-period wave superposition in cases of irregular waves significantly affect the response. Furthermore, considering a flexible base tends to decrease the response for short wave periods, concluding that, in most cases, for wave periods close to 5 s, considering a fixed base model overestimates the response.

Study on a 3D Train-Track-Bridge System Dynamic Behavior Subjected to Over-Height Collision Force

Railway bridges are built to allow trains to cross over highways, valleys, or other transportation infrastructure. In recent years, the number of railway bridges subjected to over-height collision forces has increased. These collisions damage the bridge and affect the safety of the running train. In this investigation, first, a 3D GT26 train-track-bridge interaction model was created to study the effects of collision forces applied to the bridge superstructure and not to the bridge piers as a novelty of this research using the finite element analysis. Then, the dynamic responses of the railway bridge due to the GT26 train load and subjected to over-height collision forces were obtained. Finally, the different sensitivity analyses describe that changing the length of the collision area, the bridge span, and the value of collision forces affect the dynamic responses of the bridge in the contact area. The results show that maximum lateral displacement of the concrete girder in case of assuming the GT26 train 3D model plus over-height collision force is 8.88% less than the case in which considering only freight train axle-load and same over-height collision force apply to the bridge superstructure, and its value reduces from 45 mm to 41 mm. The maximum lateral displacement of the bridge deck is reduced by about 71% by increasing the collision area length from 0.2 m to 1.2 m and at the impact area rises about 43.5% by changing collision speed from 48 km/hr to 144 km/hr as collision force from 7753 kN to 13370 kN.

Numerical and experimental study of a suspension bridge with combined viscous-steel damping system under train and seismic loads

The longitudinal dynamic performance of long-span bridges with passive vibration control devices when subjected to vehicle and seismic loads has raised extensive attention of the civil engineering community. This study aims to provide numerical and experimental assessments of the dynamic performance of a railway suspension bridge with the Combined Viscous-Steel Damping System (CVSDS) under various excitations. The deck is simplified to a single-degree-of-freedom (SDOF) system according to the longitudinal vibration characteristics of the suspension bridge. The Dynamic Equation Method (DEM) and Fourier Expansion Method (FEM) are suggested for the equivalence of the spatiotemporal variable train loads to horizontal excitations. A simplified two-stage analytical model is proposed to simulate the restoring force characteristics and fuse-lock function of the CVSDS. Shake table tests are conducted to further illustrate the feasibility of the simplified model and evaluate the effectiveness of the CVSDS. The results indicate that the SDOF system is reasonable and satisfactory in simulating the deck displacement. The two-stage working mechanism of the CVSDS is verified by both the simulation and experiment, i.e. the viscous fluid damper works under train loads and the steel yielding damper operates under earthquakes. The vibration mitigation effectiveness of the CVSDS is remarkable.

Semi-Active Groundhook Control of Offshore Tension Leg Platforms Using Tuned Mass Damper With Optimized Parameters and Magneto-Rheological Damper Under Multiple Hazards

Abstract The purpose of the current study is to recommend an offshore tension leg platform (TLP) semi-active control system to lessen vibrations caused by various risks, such as the wind load and regular and irregular waves. State-of-the-art indicates that there has not been much study on semi-active management of offshore TLPs exposed to numerous hazards while taking into account system nonlinearities and employing a control method that is resilient to uncertainty. An augmented velocity–displacement-based groundhook (AVDB-GH) semi-active control scheme using magneto-rheological (MR) dampers, which is an improvement over the displacement-based groundhook (DB-GH) control algorithm, is proposed. The proposed controller uses a semi-active tuned mass damper (SATMD) consisting of a passive tuned mass damper (TMD) and two semi-active MR dampers as the control devices. Constrained nonlinear optimization is used to determine the SATMD's optimized parameters in order to produce the best control performance. A significant reduction in surge response of TLP is observed both in the time domain and the frequency domain. Compared to the SATMD using the usual DB-GH algorithm, the suggested control strategy more successfully decreases the key response variables—deck displacement, power spectral density, and acceleration. The effectiveness of the controller is better for regular waves than for irregular waves and wind forces. Because the performance of the controller is unaffected by changes in the mass and stiffness of the TLP, the controller can be regarded as robust.

Transversal Displacement Detection of an Arched Bridge with a Multimonostatic Multiple-Input Multiple-Output Radar.

Interferometric radars are widely used for monitoring civil structures. Bridges are critical structures that need to be constantly monitored for the safety of the users. In this work, a frequency-modulated continuous wave (FMCW) multiple-input multiple-output (MIMO) radar was used for monitoring an arched bridge in Catanzaro, Italy. Two measurements were carried out; a first standard measurement was made in a monostatic configuration, while a subsequent measurement was carried out in a multimonostatic configuration in order to retrieve the components of the deck displacement. A method that is able to predict the measurement uncertainty as a function of the multimonostatic geometry is provided, thereby aiming to facilitate the operators in the choice of the proper experimental setup. The multimonostatic measurement revealed a displacement along the horizontal direction that was four times higher than the one along the vertical direction, while the values reported in the literature correspond to a ratio of at most around 0.2. This is the first time that such a large ratio detected by radar has been reported; at any rate, it is compatible with the arched structure of this specific bridge. This case study highlights the importance of techniques that are able to retrieve at least two components of the displacement.

Seismic response of RC bridges under near-fault ground motions: A parametric investigation

Natural disasters such as earthquakes can potentially harm bridges and incur significant socioeconomic losses. This study examines the effect of near-fault ground motions on reinforced concrete bridges, specifically the variation in the seismic performance with the height, aspect ratio, and longitudinal reinforcement. A suite of 332 near-fault ground motions is used to evaluate the performance of 60 bridge models in OpenSees, and the seismic responses are measured in terms of pier curvature ductility, maximum bearing deformation, and deck displacement. Linear regression analysis is used to generate probabilistic seismic demand models and fragility curves corresponding to different damage states. Expected behaviors are displayed within the models grouped with respect to height classes. Since the column diameters are based on aspect ratios, the effect of taller columns reduces the exceedance probabilities. This brought forward a need to define the damage states for tall columns in a manner different from short or medium columns. Moreover, this study underscores the need to update HAZUS fragility median values for near-field seismic response of RC bridges.

The “M and P” Technique for Damage Identification in Reinforced Concrete Bridges

The seismic damage in reinforced concrete bridges is identified in this study using the “M and P” hybrid technique initially developed for planar frames, where M signifies “Monitoring” and P denotes “Pushover analysis”. The proposed methodology involves a series of pushover and instantaneous modal analyses with a progressively increasing target deck displacement along the longitudinal direction of the bridge. From the results of these analyses, the diagram of the instantaneous eigenfrequency of the bridge, ranging from the health state to near collapse, is plotted against the inelastic seismic deck displacement. By pre-determining the eigenfrequency of an existing bridge along its longitudinal direction through “monitoring and frequency identification”, the target deck displacement corresponding to the damage state can directly be found from this diagram. Subsequently, the damage can be identified by examining the results of the pushover analysis at the step where the target deck displacement is indicated. The effectiveness of this proposed technique is evaluated in the context of straight multiple span bridges with unequal pier heights, illustrated through an example of a four-span bridge. The findings demonstrate that the damage potential in bridge piers can be successfully identified by combining the results of a monitoring process and pushover analysis.

Numerical seismic analysis of high-piled wharf strengthened with CFRP

High-piled wharves are widely employed in coastal areas, but their vulnerability to earthquake damage necessitates effective strengthening measures. This research focuses on investigating the effectiveness of carbon fiber reinforced polymer (CFRP) laminates in enhancing the seismic resistance of high-piled wharves. Full-scale 3D numerical high-piled wharves, divided into As-built groups and Retrofit groups, were established herein. During modeling, the concrete damage plasticity model (CDP) and the finite-infinite coupling element were contemplated. Two representative ground motions, i.e., the EI Centro wave and the Northridge wave, with peak accelerations of 0.2g and 0.4g, respectively, were utilized to simulate different earthquake scenarios. The responses of the resulting earthquake-induced deck displacement, pile distortion, and pile bending moment profile were explored. The computational analysis revealed significant improvements in the seismic performance of the retrofitted wharves compared to the as-built structures, proving that the externally bonded CFRP method was of great significance in improving overall structural seismic performance. Notably, the retrofitted wharf exhibited reduced deck displacement and remarkable decreases in pile deformation and bending moment. The modeling and analysis techniques can be applied to general wharves or other buildings strengthened with CFRP.

Shaking table test and numerical investigation of seismic response of pile-supported wharves with batter piles

Batter piles control displacement of wharves and offshore platforms by absorbing most earthquake and berthing loads because of their high lateral stiffness. Nevertheless, structural failure caused by stress concentrated in the pile caps has been reported in past earthquakes. The present paper investigates the seismic performance of wharf models with and without batter piles using 1 g shaking table tests with harmonic excitation as well as real earthquake records. Sensitivity analysis was performed by studying the effect of the deck load, shaking frequency, embedment depth of the pile and the relative density of the soil on horizontal displacement and acceleration of the deck. A numerical investigation was conducted using 3D finite element method to evaluate the role of the pile inclination angle on the behavior of the pile-supported system. The results of dynamic analysis quantitatively indicated the defects in the batter piles under different conditions. It was also concluded that, although the amount of deck displacement decreased when the inclination angle was reduced, the axial force generated in the batter piles showed no upward or downward trend and maximized at a specific angle.

Performance of Seismically Isolated Pile-supported Structures through 1 g Shaking Table Tests

This study fabricated friction pendulum (FP) and rolling pendulum (RP) seismic isolation systems using 3D printing to conduct 1g shaking table tests of pile-supported structure models incorporating these systems. The test results indicate that, when the FP bearing was applied to the pile heads, the acceleration response of the structure decreased once the FP bearing began to operate; as the input earthquake frequency increased (1, 3, and 10 Hz), the seismic isolation system engaged at lower input accelerations (0.16, 0.11, and 0.02 g, respectively), and the deck acceleration response decreased significantly (15, 37, and 65%, respectively) compared to that in the fixed pile head condition. Similarly, when the RP bearing was applied to the pile heads, a higher input earthquake frequency (1, 3, and 10 Hz) corresponded to a greater decrease in the deck acceleration response (82, 95, and 96%, respectively) compared to that in the fixed condition. However, a significant deck displacement was observed when using the RP bearing owing to the resonance phenomenon when the natural period of the structure was similar to the frequency of the input earthquake. Therefore, since applying RP bearing is not desirable in terms of structural displacement, it is appropriate to apply FP bearing, which can avoid resonance by changing the natural period during the operation of the seismic isolation system.

Seismic Control of a Concrete Bridge with Hybrid Passive Control Devices

Abstract: This study focuses on the seismic response of a three-span deck slab RCC T-Girder bridge with and without LRB (Lead Rubber Bearing) and in combination with LRB and FVD (Fluid Viscous Damper). The bridge is subjected to AASHTO, IRC design standards, and IRC Class A vehicle load. Linear time history analysis using CsiBridge and SAPfire is conducted to assess the bridge's seismic behavior. Excessive deck displacement, which can lead to deck failure and bridge closure, is a key concern. The study utilizes finite element analysis with Csibridge and incorporates viscous dampers throughout the bridge. The findings show that the presence of supplemental dampers significantly reduces pier top displacements. Base shear, deck displacement, pier response, and structural time period are the primary response parameters examined. The effectiveness of different isolation system configurations is compared to the non-isolated bridge in terms of these response characteristics. The study offers suggestions for design improvements to enhance the structure's performance.

Wind responses on twin box girder bridge deck using a fluid–structure interaction approach

Wind responses on a twin box girder bridge can be observed by a wind tunnel experiment or by having a full-scale setup if possible. Another possible approach is to go through a numerical approach, which is the CFD simulation of the atmospheric boundary layer surrounding the twin box girder bridge deck. A virtual wind tunnel CFD modelling simulation was carried out on the bridge deck using the Ansys Fluent FSI technique to find out the displacement of the bridge deck. The steady-state simulations were computed. The turbulence model was used to calculate the mean force coefficients as K-ω SST. It has been seen that steady simulation is needed to get the static aerodynamic coefficients right when modelling. Ansys ICEM CFD is used for meshing the bridge deck. In this study, the wind flow behaviour around the structure is analysed at different wind incident angles of − 10°, − 5°, 0°, 5°, and 10°. The pressure variations at different wind directions are mapped in the present work. Responses across and along the wind are also depicted. It was found that the drag coefficient was higher at low angles of attack, whereas the moment and the lift coefficients showed fewer values at large angles.

Experimental study on dynamic response of pile-supported wharf under wave and ship berthing collision

Pile-supported wharf is widely used in deep-water port engineering, which is inevitably subject to joint action of wave and ship berthing collision in marine environment. The evaluation of dynamic response of pile-supported wharf under wave and berthing collision is particularly essential for the design of deep-water port infrastructures. In this study, a wave flume experiment was carried out to investigate the dynamic response of pile-supported wharf embedded in a saturated sand stratum under a given wave and a three-stage pendulum steel ball collision. The pendulum collision was applied at the corner and edge midpoint of the wharf deck, respectively. A variety of representative responses are explored, including time histories of acceleration, displacement, hydrodynamic pressure, pore water pressure, and strain, which characterize the important aspects of dynamic behavior of pile-supported wharf-ground system. Acceleration and displacement of deck as well as acceleration of sand stratum are dominated by the berthing collision; hydrodynamic pressure on piles and pore water pressure of sand stratum are controlled by the wave action; and strain and bending moment on piles are depended on the joint action of wave and collision. It should be noted that dynamic response characteristics of pile-supported wharf will change significantly due to the decreasing of pile effective buried depth near berths induced by the berthing collision energy accumulation. Furthermore, pile group effects including wave scour around piles, collision energy propagation in a sand stratum, and peak bending moment on piles are explored. For comparison, dynamic response of a single pile-ground system and free field are also discussed. Dynamic response of sand stratum around single pile induced by berthing collision on wharf deck is greater than that of free field at the same distance. Experiment techniques and insights from this study may be of significance to the design and maintenance of pile-supported wharves.