Summary
Identifying mode shapes of bridge structures typically require a dense array of stationary sensors to accurately capture mode shapes with appropriate spatial resolution. An alternative ...approach is developed here, which requires only a single pair of actuator and sensor. The mode shape identification involves, first, identifying the natural frequencies and modal damping ratios, followed by an estimation of the mass normalized mode shapes components at the excited and measured degrees of freedom. An input–output balance is employed with a series of inputs and outputs obtained from a sequence of tests. The sequence of tests include exciting and measuring at different locations along the bridge, using either a roving actuator and/or a roving sensor; the requirement for a unique identification is that the roving actuator and sensor must be collocated in at least one of the tests. The performance of the proposed method using different types of responses, namely, displacement, velocity, and acceleration, is assessed using numerical simulations. The effect of different types of errors in the identification process is also studied. The method is finally applied to experimental data obtained from laboratory scale tests.
A self-centering designed bridge model that can eliminate residual deformations after earthquakes was constructed and tested by a shaking table. The bridge model consists of two precast RC bridge ...columns post-tensioned to the concrete deck and foundations by high strength rods. The concrete deck moves horizontally and columns rock on the foundation surface under the excitation of earthquakes. Research parameters include materials used in the rocking interface (plastic or steel), anchoring states and forms of ground shaking. Through the shaking table tests, the seismic performance of the bridge model with variable parameters was evaluated in terms of deck displacement, deck acceleration, vibrating frequency and damping ratio. Test results showed that the bridge model rocked up to at least 5% of the column rotation without damage or residual deformation. Seismic energy dissipated through each impact of column rocking was used to evaluate the radiation damping of the bridge system based on a previous study. Analytical damping of each test was calculated and compared with tested damping estimated from the modified response spectra and the measured displacement and acceleration at the concrete deck.
Beam bridges, as the primary structural form of medium and small-sized bridges, are extensively utilized for road and railway crossings over rivers and valleys. Ensuring their reliability during ...earthquakes is crucial not only for maintaining traffic flow but also for mitigating the seismic impact on the economy and society. Considering earthquake intensity and uncertain parameters, this paper proposes an innovative method for assessing the seismic reliability of simply-supported beam bridges under three different levels of seismic design: minor, moderate, and major earthquakes. The proposed method first estimates the probability of encountering three typical earthquake intensities during the design life of simply-supported beam bridges based on crowd intensity, benchmark intensity, and major earthquake intensity. It then introduces uncertain parameters and employs the point estimation method to calculate the probability of bridge passage under specific earthquake intensities. Finally, it combines these earthquake intensities to calculate the overall seismic reliability of simply-supported beam bridges. The effectiveness and efficiency of this method are demonstrated through calculations for a three-span, double-degree-of-freedom simply-supported beam bridge, and validated using Monte Carlo simulations. This research provides solid theoretical support for seismic assessment, design, and intensity-based reliability analysis of simply-supported beam bridges.
Recently, there has been a shift in emphasis in bridge monitoring from instrumentation of the bridge to instrumentation of a passing vehicle, known by “drive-by bridge inspection”. This paper ...introduces a new method of identifying bridge damage using an instrumented truck; specifically using the truck acceleration histories to calculate changes in the “bridge displacement profile” which is shown to be sensitive to structural damage. The study includes three different bridges modeled as 1D FE beam elements and 2D FE plate elements. The simulation of the vehicle–bridge interaction is implemented in MATLAB. The truck is represented as a simple quarter car model crossing over a rough profile. The approach is also numerically tested for local damage in the bridge plate model. Finally, there is a study of sensitivity to signal noise, corrupted truck properties, initial conditions and transverse vehicle position.
Elastomeric bearings (EB) and lead-rubber bearings (LRB) are used in bridge structures to reduce vehicle vibrations, wind loads, and earthquakes. Therefore, studying their stability is crucial to ...ensuring the stability of the bridge system itself. Building upon previously proposed linear and partially nonlinear models, two fully nonlinear models suitable for EBs and LRBs are proposed in this paper. The models are developed to adequately account for the interaction between the horizontal and vertical loads and their effect on the bearing’s performance. This study considers that the horizontal and vertical loads do not always act in isolation and that their interaction can significantly affect the bearing’s overall behavior and stability. Comparisons with experiments demonstrated that the models could accurately replicate the behavior of seismic isolators. Additionally, analytical models are developed to predict the horizontal and vertical stiffnesses as a function of the critical buckling load. The two mathematical models can readily be incorporated into open-source structural analysis software, such as OpenSees.
Modern bridge structures need light decks with long durability and promising technical parameters. Glass fiber-reinforced polymer orthotropic bridge deck creates unconventional possibilities in ...bridge designing. Parallel identification of glass fiber-reinforced polymer deck panel by differential thermal analysis, spectroscopy analysis, scanning and optical microscope monitoring, dynamic mechanical analysis and differential scanning calorimetry analysis, tensile and flexural tests will be presented in the paper. Differential thermal analysis was carried out for estimation of the physical and chemical transformation of glass fiber. The differential scanning calorimetry experiments were performed in the glass fiber-reinforced polymer–bridge deck material for determining the mass variation and the energy changes suffered by the materials, as a function of temperature and time. Dynamic mechanical analysis was allowed to detect thermal effects based on the changes in the modulus or damping behavior. Tensile and flexural tests allowed the observation of the decomposition process and information about the basic stress parameters of glass fiber-reinforced polymer material used in bridge applications was taken. Aforementioned analyses are necessary to examine the durability description of the composite element.
Coastal bridges are susceptible to severe damage when subjected to successive earthquake-tsunami events. Previous studies mainly consider the tsunami loadings as hydrodynamic forces, whereas other ...hydrodynamic forces such as uplift and slamming forces, are not fully investigated. Moreover, there are limited studies on the dynamic performance of simply supported girder bridges under the earthquake-tsunami sequences. To this end, this paper aims to conduct an in-depth investigation on dynamic performance of simply supported bridges subjected to sequential earthquake and tsunami hazards by means of a high-fidelity wave force simulation approach. More specifically, a typical, already constructed simply supported girder bridge is taken as the example bridge, and the numerical model of this bridge is built using the analytical platform OpenSees. The applied time series of tsunami wave force with five wave heights are generated based on a refined computational fluid dynamics (CFD) model, and are separately combined with the time histories of 21 pairs of far-field earthquake records to generate the sequential earthquake and tsunami loadings. Subsequently, nonlinear time history analyses (NTHAs) are carried out to obtain the structural dynamic responses, and the effects of preceding earthquakes and wave heights on the performance are investigated. Results indicate that the bearings are susceptible to the damage in the longitudinal direction of the bridge under the sequential earthquake and tsunami loadings, while the piers sustain more damage in the transverse direction. The preceding earthquakes have a significant effect on the bridge performance, and the effect becomes more pronounced with the increase of the ground motion intensity. The contribution of the tsunami loadings to the bridge response increases as the wave height rises. In particular, the transverse pier drift is dominated by the tsunami loadings when the wave height is higher than 7 m. The outcome of this study could aid the design and management of coastal bridge subjected to successive earthquake-tsunami events.
Ground penetrating radar (GPR) is a non-destructive geophysical technique that is widely used to determine the relative condition of reinforced concrete. This paper presents case studies from ...Missouri, USA, where a ground-coupled GPR system was used to assess the condition of eleven concrete bridge decks. The main goal of this paper is to develop appropriate acquisition and processing parameters in order to conduct rapid, efficient, and cost-effective assessment of bridge decks. To accomplish this goal, the GPR data sets were collected with slightly different acquisition parameters and processed using different parameters. The quality of the results and the time required for each bridge deck survey are analyzed. Additionally, several experimental data sets were collected across a 12th concrete bridge deck to examine the influence of weather conditions on reflection amplitude values, since amplitude analysis is used in this study. Based on the authors' experience and findings, appropriate GPR acquisition and processing parameters are suggested and described for use of the ground-coupled GPR method for bridge deck assessment.
•Ground-coupled GPR system is deployed to assess the condition of the bridge decks.•We recommended optimum acquisition and processing parameters.•Weather conditions affect the reflection amplitude values.•High-frequency ground-coupled GPR antenna provides detailed information.
This paper characterizes the extensive research activities conducted in the Earthquake Engineering Laboratory of University of Nevada, Reno, in the field of dynamic monitoring and system ...identification of three 1/3-scale two-span bridges. The first part of the study briefly presents the verification of target-tracking Digital Image Correlation (DIC) results as compared to conventional sensors, e.g., string potentiometers and triaxial accelerometers from one of the three bridge tests. Structural system identification is presented in the second part for the other two bridges with a focus on determining structural model parameters based on the DIC measured response data. All bridges were tested under bidirectional earthquake loading using the multiple shake table array. However, the system identification used data collected from white noise runs before and after the seismic tests. A quasi-linear response of the system was assumed because of the low intensity white noise base excitations, and the modal parameters were estimated accordingly. Using the structural vibration data recorded by target-tracking DIC at various locations on the bridges, five system identification methods were applied to analyze the modal parameters of the tested bridges. The results were used to estimate the frequency, damping ratio, and mode shapes of the bridges in two states. The initial state is before seismic testing and the end state is the damaged state after the completion of the seismic tests. The results show that the applied methods provide a reasonable estimate of the natural frequency and damping ratio of the bridge systems in the original and damaged states.
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