Bridges In Taiwan Research Articles

Finite element model of a cable-stayed bridge updated with vibration measurements and its application to investigate the variation of modal frequencies in monitoring

Ambient vibration measurements of a cable-stayed bridge in Taiwan were first conducted to identify its dominant modal parameters with a reliable stochastic subspace identification algorithm recently developed. A finite element model is then constructed based on the identified frequencies and shape vectors of four vertically bending, one torsional, and one horizontally bending modes. This model is also updated by adjusting the girder-pier connection with the addition of a rotational spring to reflect the actual conditions and its accuracy is demonstrated with less than 1% of error for the first two vertically bending modes. As a solid application for probing the environmental effects in structural health monitoring, the vibration measurements of 24 hours were further conducted and combined with the well calibrated model to investigate the controlling factor for its variation in modal frequencies. It is found that the frequencies of the first two vertically bending modes are closely correlated to the root-mean-square velocity representing the traffic excitation intensity. Moreover, it is shown with the updated model that the daily variations in the frequencies of the first two vertically bending modes can be reasonably simulated by modifying the coefficient of the rotational spring merely in a limited range.

Analysis of general functional bearing model in a single-span bridge to identify structure response and suitable friction coefficient under near- and far-fault earthquakes

ABSTRACT Analysis of a single-span bridge with rubber bearing as the isolation system is performed under earthquakes. The conventional bridge seismic design requires the whole structure to be perfectly connected to avoid interrupting the transfer of earthquake energy from the ground through the bridge. A bridge with this typical design requires a high-cost construction due to the need for a huge section of the bridge to resist the earthquake force demand. Thus, many bridges in Taiwan are designed with a rubber bearing only put in between the column and girder without an anchor system. Thus, the bridge movement by rubber displacement is permissible, but the sliding displacement must be accommodated to limit the movement. The sliding displacement is the method to exploit the friction force provided by the sliding on the top and bottom interface of the rubber with the girder and column to dissipate the earthquake input energy transmitted to the structure. By involving the role of surface friction, the shear force transmitted to the structure can be reduced and the bridge performance optimized. General Functional Bearing Model (GFBM) analysis is a rubber bearing analysis which unmerges the function of friction and restoring force. In contrast with the conventional method, the rubber bearing designed with GFBM analysis may reduce the bridge stiffness and deck acceleration, and it is more convenient because only sliding displacement needs to be controlled. This research proposed GFBM analysis to simulate the rubber bearing that is reflected in the real conditions of bridges in Taiwan.

Establishment of a Sustainability Assessment System for Bridges

In this paper, with the motivation of “green” and “sustainability” for bridge projects, ten key indicators were selected to establish a reliable and applicable sustainability assessment system. It is also expecting the civil infrastructure to be developed more ecologically, environmentally, and friendly by applying the proposed assessment system. The data collection method in this research is questionnaire-based expert interviews. The questionnaire results were well analyzed and calculated for the key indicators’ weights by adopting the top two boxes theory (TTBT) and multiple attribute value theory (MAVT). Consequently, the sustainability assessment system for green civil infrastructure (SASGCI) was established to evaluate infrastructure projects’ sustainability achievements. In this study, the authors conclude the weights of ten key indicators for bridges as follows: risk mitigation and reliability: 15.3%, durability: 15.1%, landscape: 11.5%, ecology: 10.6%, benefit and function: 9.7%, environmental protection and carbon emissions reduction: 9.5%, waste reduction: 8.5%, energy-saving: 7.1%, creativity: 7.0%, and humanities and culture reservation: 5.6%. An example of a scenic bridge in Taiwan is presented to demonstrate the applicability of the established SASGCI for sustainability evaluation. The result indicates that the evaluation system is successful.

Dynamic Deformation Measurement by the Sampling Moir\xe9 Method from Video Recording and its Application to Bridge Engineering

Measuring accurate dynamic deformation distribution for large-scale structures inexpensively and efficiently is a crucial challenge of structural health monitoring. In this study, a simple technique for measuring the deflection and vibration frequency from a captured video, based on the sampling Moiré method is developed. The striking advantage over conventional measurement using sensors and other imaging techniques are that the developed technique allows accurate measurement of two-dimensional deformations at multiple locations as well as the natural frequency of the target structure. Joint Photographic Experts Group (JPEG)-formatted images encoded from the recorded video with Motion-JPEG (MJPEG) format reduced the file size significantly without degrading the measurement accuracy and applied to deformation measurement. The effectiveness of the developed technique was confirmed through a field experiment of an old bridge in Taiwan. The field experiment demonstrated that both deflection and natural frequency of the bridge were successfully measured with higher 0.1 mm displacement accuracy and 0.05 Hz frequecy comparable to a conventional microwave radar displacement sensor from 20 m distance.

Analysis of arch bridge collapse based on finite element technology

Even in today’s technologically advanced, engineering accidents are still unavoidable. How to numerically simulate the collapse process of bridges becomes a major problem, and the continuous development and maturity of finite element technology provides an effective way to solve this problem. This paper takes the Yilanao Bridge in Taiwan as the research object, and establishes multiple models based on the finite element analysis software MSC. MARC and MIDAS, and analyzes the causes of the damage. This paper has certain reference significance for the study of the failure form and failure process of arch bridges.

Overwater depth inspection on a submerged pile bent

In this paper, a foundation inspection strategy was developed to determine the condition on a fully-submerged pile bent foundation supporting an overwater vehicular bridge in Taiwan. The electrical resistivity tomography inspection displayed the overall conditions of the salt-content canal. Using the reciprocal principle-based ultra-seismic inspection could finely determine the foundation depth. The time lapse analysis and traditional frequency analysis provided varying degrees of reliability on the pile length estimate, positively re-confirmed with the design charts. The entire investigation demonstrates the conclusiveness in determining the foundation depths when two testing methods are corroborated with appropriate analysis modes.

Virtual reality for showcasing sustainable engineering design

One of the goals of national parks is to promote sustainable development and environmental education. This paper presents a study to further the goal by demonstrating the value of virtual reality and augmented reality in the construction of a FRP (Fiber Reinforced Polymer or Plastics) pedestrian bridge in Taiwan’s national park. The purposes are three-fold. First, the bridge serves to educate visitors about the infrastructure of the park. Second, it attracts the attention of the public and raises interest in conservation and sustainability. Third, it allows to showcase sustainable engineering design with the latest virtual reality technology. The example described in this paper is based on the same principles of e-learning and mobile learning. The experience is valuable in encouraging and promoting tourism opportunities and sustainable resource use in national parks.

A Probabilistic Safety Evaluation Framework for Multi-Hazard Assessment in a Bridge using SO-MARS Learning Model

A probabilistic evaluation procedure is established to assess a bridge safety against floods and earthquakes, which are the two major threats of a bridge in Taiwan. Scour depth distribution is used to reflect the flood hazard, in which swarm optimized multivariate adaptive regression splines (SO-MARS) is utilized to calculate scour depth density followed by Monte Carlo Simulation (MCS) and a scour risk curve is constructed. Displacement ductility is used to measure the bridge performance under attacks of both hazards through nonlinear time history analyses followed by a power law regression to build the fragility curve. A code-based probabilistic seismic hazard curve is constructed and the joint failure probability under seismic and flood attacks is obtained. A numerical example is provided to illustrate the proposed methodology, in which the nonlinear behaviors in concrete (including core and cover areas), steel bar and soil are included in a bridge model. A threshold scour depth for a given earthquake (e.g., the return period or the peak ground acceleration is given) is derived to meet a specified target reliability. The suggested scour depth is a deterministic number which is immediately applicable in engineering practice.

Probabilistic safety evaluation of a river bridge substructure against floods

Many factors affect the safety of a reinforced concrete river bridge, and some of these factors might have significant uncertainty that should be evaluated. This study focuses on a system reliability analysis of a reinforced concrete bridge, which is the most common type of river bridge in Taiwan. Specifically, non-linear behaviours of core/cover concrete and steel reinforcement in the substructure of a bridge are considered. Uncertainties of stream surface elevation, water velocity, local scour depth, soil property and record-to-record variations are included in the probabilistic model. The aforementioned parameters of six river geometries are incorporated into a Hydrologic Engineering Center-river analysis system (HEC-RAS) model to assess their impacts on the bridge safety. The effect of river geometry has not been studied thoroughly. Results shown here indicate that it plays an important role. Adopting Bayesian theory to consider the record-to-record uncertainty by combining historic and HEC simulation data is another innovative aspect of this study. Monte Carlo simulation is used to conduct the reliability analysis. The results obtained indicate that the proposed procedure for the bridge reliability analysis is consistent with expert engineering judgement and that the variation in scouring depth and river geometry are pertinent to bridge safety.

Delphi process applied to the 921 earthquake relief for damaged bridges in Taiwan

This paper presents panel-developed, expert opinion-based suggestions, and a Delphi process for the development of an earthquake damage assessment and recovery model. The model was specifically designed for the disaster relief of the damaged bridges of the 921 earthquake in Taiwan and uses four major indices: emergency handling ability, administrative capability, budget execution responsibility, and law enforcement reliability. The 921 earthquake, which occurred on September 21, 1999, forced the Taiwanese government into an unprecedented relief operation consisting of emergency rescue and reconstruction. However, some of the relief measures reflected possible inefficiency in intergovernmental cooperation. Regarded as one of the most decisive relief measures in Taichung County before it was consolidated and upgraded to a municipality on 25 December, 2010, the rescue and reconstruction of the majorly damaged bridges in the county were taken as an example to analyze the differences in the earthquake relief policies between the central and local governments. Based on experts’ experiences in government affairs and the four major indices of the damage assessment and recovery model, the ongoing governmental restructuring policy is considered retrospectively not only at the central government level but also at the local government level; this would serve to improve preparedness for catastrophes and to solve possible problems in earthquake-related intergovernmental cooperation.

A self organizing map optimization based image recognition and processing model for bridge crack inspection

Abstract The current deterioration inspection method for bridges heavily depends on human recognition, which is time consuming and subjective. This research adopts Self Organizing Map Optimization (SOMO) integrated with image processing techniques to develop a crack recognition model for bridge inspection. Bridge crack data from 216 images was collected from the database of the Taiwan Bridge Management System (TBMS), which provides detailed information on the condition of bridges. This study selected 40 out of 216 images to be used as training and testing datasets. A case study on the developed model implementation is also conducted in the severely damage Hsichou Bridge in Taiwan. The recognition results achieved high accuracy rates of 89% for crack recognition and 91% for non-crack recognition. This model demonstrates the feasibility of accurate computerized recognition for crack inspection in bridge management.

Case study on foundation aberration of a river-crossing bridge in Taiwan

Case study on foundation aberration of a river-crossing bridge in Taiwan

Flutter Derivatives of the Kao-Pin Hsi Cable-Supported Bridge

Long-span cable-supported bridges, characterized with low natural frequencies and mechanical damping, are very sensitive to wind effects. Therefore, investigation of the aeroelastic behaviour of bridges is particularly important when designing these complex engineering structures. The focus is on evaluation of dimensionless aeroelastic coefficients, i.e. flutter derivatives, which are considered as indicators of the aeroelastic stability of bridges. A comprehensive experimental study on dynamic wind-induced behaviour of the Kao-Pin Hsi Bridge in Taiwan is carried out in the Climatic Wind Tunnel of the Centre of Excellence Telč (CET), Czech Republic. The bridge-deck section is tested at a multipurpose experimental setup originally developed in the CET. Flutter derivatives are obtained by the means of the free-vibration technique for the double-degree-of-freedom (DDOF) system. The results are compared to those of a thin flat plate with large width to height ratio, which previously proved to be stable with respect to the flutter phenomenon. While the torsional instability is observed for the Kao-Pin Hsi bridge-deck section, the flat plate proves to be aeroelastically stable.

A PROBABILISTIC EVALUATION OF PIER-SCOUR POTENTIAL IN THE GAOPING RIVER BASIN OF TAIWAN

A probabilistic approach is used to create a preliminary inspection evaluation form (PIEF) for scour potential at bridge sites. In Taiwan, the risk of pier scour is often evaluated using a two-step procedure. First, a bridge is visually inspected based on a PIEF. An advanced scour risk analysis is conducted for a bridge with a high PIEF score. Because a PIEF can quickly evaluate scour potential, it can be used to build a maintenance sequence for a group of bridges. However, a PIEF is often created based on only engineers’ experience; the accuracy and reliability of PIEFs have not been examined systematically. Thus, a probabilistic-based PIEF is constructed by establishing a close correlation between the PIEF score and scour potential via Taguchi method. The scour potential is evaluated by Bayesian network (BN) that incorporates experts’ judgments and results of reliability analyses. For example, the conditional probabilities (CP) in the proposed BN are calculated based on an existing PIEF and results of a stability-based reliability analysis. Thus, the proposed PIEF implicitly considers the probabilistic characteristics in the scour potential, which will provide an efficient and accurate evaluation of scour potential and assist in establishing maintenance priorities of existing bridges in Taiwan.

Seismic Assessment of Bridge Diagnostic in Taiwan Using the Evolutionary Support Vector Machine Inference Model (ESIM)

Because earthquakes cause bridge damage resulting in incidents such as traffic gridlock and casualties, it is necessary to assess possible bridge damage under different seismic intensity levels in order to reduce the incidence of disasters. However, because there are many bridges in Taiwan, the time and budget will be restricted to conduct traditional structural analysis (preliminary assessment, detailed analysis) of each bridge to obtain its yield acceleration (Ay) and collapse acceleration (Ac). Hence, this study developed an inference model by integrating two AI techniques: support vector machines (SVM) and fast messy genetic algorithms (fmGA). The study applied historical cases to infer Ay and Ac values by the mapping relation between preliminary assessment factors (input) of historical cases and the detailed assessment of Ay and Ac values (output). According to the above inference model to predict Ay and Ac values, the probability of possible bridge damage by earthquakes can be predicted as a suggestion for bridge management personnel in a short period of time. This study adopted 121 RC bridges in Taiwan and selected 109 bridges for training cases and 12 bridges for testing cases to calculate the root mean square error (RMSE). The results indicate that the RMSE of training is 0.087 and of testing is 0.0869.

Evaluation of Flood-Resistant Capacity of Scoured Bridges

AbstractThe exposure of pier foundations owing to scour significantly reduces the foundation-bearing capacity and diminishes the flood-resistant capacity of a bridge. This paper proposes a nonlinear quasi-static analysis procedure for the performance of bridges with pile foundations under flow-induced loads for the evaluation on the flood-resistant capacity of scoured bridges. The Winkler beam model is adopted for the modeling of the pile-soil system, and the distributed hinge model is utilized to simulate the possible flexural failure of the piles. Soil springs with nonlinear p-y curves are used to represent the nonlinearity of the supporting soil. To demonstrate this procedure, a case study on the Shuang-Yuan Bridge in Taiwan was performed for various flood and scour conditions. This bridge was partially demolished in a major flood event caused by Typhoon Morakot in 2009. According to the analysis results, a possible scenario for the failure of the Shuang-Yuan Bridge is presented, and the proposed metho...

Case study of first all-GFRP pedestrian bridge in Taiwan

To forestall the severe deterioration of structures as a result of corrosion, the first all-FRP composite pedestrian bridge was built in Tainan, Taiwan. The bridge superstructure was designed by placing Glass Fiber Reinforced Polymer (GFRP) decks onto four FRP I-girders that served as the bridge girders. Bridge diaphragms and FRP rods placed between the girders helped dissipate the loading to the other girders and prevent torsion respectively. The pultruded GFRP composite profiles were used in constructing this bridge located in the Taijiang National Park of Taiwan. This paper discusses the features of the pedestrian bridge and the detailed design of all the components of the bridge. A new method of digitally archiving the pedestrian bridge using a 3D terrestrial laser scanner was also presented. Lastly, results of the theoretical analysis were compared with the finite element analysis (FEA), to predict the static flexural behavior of an 8-m girder under loadings. After agreement of the theoretical results (using Timoshenko Beam Theory and Euler–Bernoulli Beam Theory) and the FEA results, the pedestrian bridge superstructure was modeled and analyzed. Deflection results obtained from the FEA showed that the pedestrian bridge meets the deflection criteria.

Probability-based damage assessment for reinforced concrete bridge columns considering the corrosive and seismic hazards in Taiwan

In this paper, we consider the time at which earthquake events occur when analyzing seismic structural damage to a deteriorating RC bridge within a specified period. Because the uncertainty exists in the occurrence time of earthquake events, Monte Carlo simulation is applied. The proposed procedure for evaluating the exceedance probability, which corresponds to a specified limit state, is then applied to a case study of RC bridges in Taiwan to demonstrate its applicability. This study selects three typical RC bridges located in the Taipei Basin, Taiwan, to analyze exceedance probabilities of specified damage states during various specified periods and then discusses the cumulative damage effect on the exceedance probabilities of specified damage states. Additionally, for the chloride-induced deteriorating bridges at various distances to the sea in Suao, Taiwan, the effects of the deterioration and seismic structural damage on the exceedance probabilities of specified damage states are demonstrated and discussed. The proposed assessment procedure can help engineers understand whether the deterioration would accelerate the declining seismic performance of bridges and shorten their serviceability-related and safety-related service lives, as well as provide reference for repairing RC bridges and retrofitting their seismic performance.

A study on damage assessment of the scoured bridges

Throughout the past decade, scoured bridges in Taiwan have frequently collapsed as a result of heavy rainfall during typhoon seasons. To mitigate the bridge damage caused by scouring, an improved warning system is required. Three fundamental parameters including the water level, the flow velocity, and the scouring depth (SD) are significant for the structural safety of a scoured bridge. Nowadays, these parameters can be successfully detected by advanced monitoring instruments and serve as a database for a damage assessment system to carry out the function of early warning. Therefore, this article aims at developing the damage assessment system for scoured bridges as the core of a warning system.We have proposed an analytical process as an assessment system. Through finite element analysis with respect to water level and flow velocity, the critical scouring depth with a specific degree of safety factor for a bridge foundation can be determined by choosing among different failure modes. Accordingly, the relationships between various possible sets of water levels, flow velocities and critical SD are established to present the surfaces of structural safety corresponding to different levels of safety factor. The surfaces obtained can then be applied to the warning system.Based on the proposed assessment process, the collapse of the Shuang-Yuan Bridge caused by Typhoon Morakot in 2009 is discussed in detail. The consequence of bridge collapse is reasonably explained by the analytical surfaces of structural safety based on the reported parameters at the bridge site. In addition, the Dia-Jia-Hsi Bridge, which has implemented advanced monitoring instruments serves as the second case study. The surfaces of structural safety obtained have been used in conjunction with real-time observations of sensitive parameters to display the situation of structural safety at any time. The results obtained in this article benefit bridge engineers, giving a safety-management platform to speed up the decision making process during an emergency.

Seismic risk assessment system of existing bridges in Taiwan

The main objective of this study is to establish a rapid seismic risk analysis system for the existing bridges based on the pre-calculated fragility curves of more than 2000 bridges in Taiwan. In order to get the peak ground accelerations at sites of different bridges located in Taiwan resulted from each different earthquake, the attenuation law of peak ground accelerations for each station was also proposed based on the regression analysis on recorded earthquakes in Taiwan. The accuracy of the simulated results was also verified through the comparison with the data collected by Central Weather Bureau's in the past three years. In this study, the object-oriented programming is also incorporated to develop a seismic risk assessment system, which can instantly estimate and visually demonstrate the level of damage to bridges due to a specific seismic event and the corresponding economic loss due to the damage of bridges. The achievements attained from this study may be helpful for earthquake protection strategy in the future.