• Structural Engineering and Mechanics
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• v.81 no.2
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• pp.147-161
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• 2022

The Brace-Type Shear Fuse (BSF) device is a newly proposed steel damper with excellent cumulative ductility and stable energy dissipation. In consideration of the current situation where there are not many alternatives for transversal seismic devices used in long-span three-tower self-anchored bridges (TSSBs), this paper implements improved BSFs into the world's longest TSSB, named Jinan Fenghuang Yellow River Bridge. The new details of the BSF are developed for the TSSB, and the force-displacement hysteretic curves of the BSFs are obtained using finite element (FE) simulations. A three-dimensional refined finite element model for the research TSSB was established in SAP2000, and the effects of BSFs on dynamic characteristics and seismic response of the TSSB under different site conditions were investigated by the numerical simulation method. The results show that remarkable controlling effects of BSFs on seismic response of TSSBs under different site conditions were obtained. Compared with the case without BSFs, the TSSB installed with BSFs has mitigation ratios of the tower top displacement, lateral girder displacement, tower bending moment and tower shear force exceeding 95%, 78%, 330% and 346%, respectively. Meanwhile, BSFs have a sufficient restoring force mechanism with a minor post-earthquake residual displacement. The proposed BSFs exhibit good application prospects in long-span TSSBs.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.897-919
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• 2015

In this study, the effects of ground shocks due to explosive loads on the dynamic response of historical masonry bridges are investigated by using the multi-point shock response spectrum method. With this purpose, different charge weights and distances from the charge center are considered for the analyses of a masonry bridge and depending on these parameters frequency-varying shock spectra are determined and applied to each support of the two-span masonry bridge. The net blast induced ground motion consists of air-induced and direct-induced ground motions. Acceleration time histories of blast induced ground motions are obtained depending on a deterministic shape function and a stationary process. Shock response spectrums determined from the ground shock time histories are simulated using BlastGM software. The results obtained from uniform and multi-point response spectrum analyses cases show that significant differences take place between the uniform and multi-point blast-induced ground motions.

• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.157-173
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• 2020

In the finite element modelling of long-span cable-stayed bridges, there are a lot of uncertainties brought about by the complex structural configuration, material behaviour, boundary conditions, structural connections, etc. In order to reduce the discrepancies between the theoretical finite element model and the actual static and dynamic behaviour, updating is indispensable after establishment of the finite element model to provide a reliable baseline version for further analysis. Traditional sensitivity-based updating methods cannot support updating based on static and dynamic measurement data at the same time. The finite element model is required in every optimization iteration which limits the efficiency greatly. A convenient but accurate Kriging surrogate model for updating of the finite element model of cable-stayed bridge is proposed. First, a simple cable-stayed bridge is used to verify the method and the updating results of Kriging model are compared with those using the response surface model. Results show that Kriging model has higher accuracy than the response surface model. Then the method is utilized to update the model of a long-span cable-stayed bridge in Hong Kong. The natural frequencies are extracted using various methods from the ambient data collected by the Wind and Structural Health Monitoring System installed on the bridge. The maximum deflection records at two specific locations in the load test form the updating objective function. Finally, the fatigue lives of the structure at two cross sections are calculated with the finite element models before and after updating considering the mean stress effect. Results are compared with those calculated from the strain gauge data for verification.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.125-135
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• 2015

The tendency of more longer span length being required economical in railway bridges is studying about PSC I shaped girder. In this case, it is important to analyze and choose the effective girder section for stiffness of bridge. This study investigates the dynamic properties and safety of PSC I shaped girder being used wide upper flange whose selection based on radii and efficiency factor of flexure for railway bridge in different span type. In addition, 40m PSC Box girder bridge adopted in Honam high speed railway is further analyzed to compare dynamic performance of PSC I shaped girder railway bridge with same span length. Time history response is acquired based on the mode superposition method. Static analysis is also analyzed using standard train load combined with the impact factor. Consequently, the result met limit values in every case including vertical displacement, acceleration and distort.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.50-57
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• 2023

Autonomous driving technologies have been gradually improved for road traffic owing to the development of artificial intelligence. Since the truck platooning is beneficial in terms of the associated transporting expenses, the Connected-Automated Vehicle technology is rapidly evolving. The structural performance is, however, rarely investigated to capture the effect of truck platooning on civil infrastructures.In this study, the dynamic behavior of bridges under truck platooning was investigated, and the amplification factor of responses was estimated considering several parameters associated with the driving conditions. Artificial intelligence techniques were used to estimate the maximum response of the mid span of a bridge as the platooning vehicles passing, and the importance of the parameters was evaluated. The most suitable algorithm was selected by evaluating the consistency of the estimated displacement.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.363-377
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• 2018

The proper functioning of critical points on transport infrastructure is decisive for the entire network. Tunnels and bridges certainly belong to the critical points of the surface transport network, both road and rail. Risk management should be a holistic and dynamic process throughout the entire life cycle. However, the level of risk is usually determined only during the design stage mainly due to the fact that it is a time-consuming and costly process. This paper presents a simplified quantitative risk analysis method that can be used any time during the decades of a tunnel's lifetime and can estimate the changing risks on a continuous basis and thus uncover hidden safety threats. The presented method is a decision support system for tunnel managers designed to preserve or even increase tunnel safety. The CAPITA method is a deterministic scenario-oriented risk analysis approach for assessment of mortality risks in road tunnels in case of the most dangerous situation - a fire. It is implemented through an advanced risk analysis CAPITA SW. Both, the method as well as the resulting software were developed by the authors' team. Unlike existing analyzes requiring specialized microsimulation tools for traffic flow, smoke propagation and evacuation modeling, the CAPITA contains comprehensive database with the results of thousands of simulations performed in advance for various combinations of variables. This approach significantly simplifies the overall complexity and thus enhances the usability of the resulting risk analysis. Additionally, it provides the decision makers with holistic view by providing not only on the expected risk but also on the risk's sensitivity to different variables. This allows the tunnel manager or another decision maker to estimate the primary change of risk whenever traffic conditions in the tunnel change and to see the dependencies to particular input variables.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.1
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• pp.39-48
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• 2023

Because a railway bridge is designed over a long period of time and covers a large site, it involves various environmental factors and uncertainties. For this reason, design changes often occur, even if the design was thoroughly reviewed in the initial design stage. In particular, design changes of large-scale facilities, such as railway bridges, consume significant time and cost, and it is extremely inefficient to repeat all the procedures each time. In this study, a technique that can improve the efficiency of learning after design change was developed by utilizing the learning result before design change through transfer learning among deep-learning algorithms. For analysis, scenarios were created, and a database was built using a previously developed railway bridge deep-learning-based prediction system. The proposed method results in similar accuracy when learning only 1000 data points in the new domain compared with the 8000 data points used for learning in the old domain before the design change. Moreover, it was confirmed that it has a faster convergence speed.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.448-455
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• 2007

In 1992, the first design standard of quake proof bridge was established. However, most bridge structures which were constructed without considering earthquake in former times need performance of quakeproof property. Quakeproof analysis in current bridges, is based on analysis of load base which just has strength over the load of simple structures but is not checked through simple comparison of strength performance of structures so that we would like to check that ADRS method is reasonable or not using ADRS method(Accleration-Displacement Response Spectrum Method), a analysis method based on displacement of object of performance test. As the result of that, the capacity spectrum method can avoid complex dynamic analysis in analysis based on loads and it efficiently applies to design verification with normal checking for quakeproof performance and aimed performance of new structures. However we can not consider effects of high modes and it has problem that does not consider falling of performance in structures by repeated load.

• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.365-371
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• 2016

In the case of the superstructure which is consist of two I girders and slab, the section can behave as II section, so that the neutral axis with respect to out of plane direction flexure can be regarded as major axis. Therefore in-plane flexural mode might govern the free vibration mode. Meanwhile, horizontally curved girders always experience not only bending moments but also torsional moments although the primary load is usually supposed to be gravitational load. The interaction due to bending and torsional moments make the behavior complicated and torsional mode may govern the free vibration mode. In other words, structure can have different dynamic characteristic due to its initial curvature. In this research, using 3-dimensional sell elements, free-vibration analyses are carried out due to initial curvature. The analysis models are assumed to be composite and non-composite and finally natural frequency and eigen mode are discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.107-117
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• 2014

This study tests homogeneity and performs multiple comparison analysis among treatment levels of each factor group through t-test by materials and analysis of variance by structural type and service period. For that descriptive statistical analysis is performed for static and dynamic response characteristics and their ratios of calculated versus measured values based on a good many safety assessment reports for bridges. Homogeneity and post hoc test based on descriptive statistical analysis provide the measures for homogeneity identification among comparison groups in addition to the statistical reference values such as central tendency, variation and shape. This study is expected to be valuable for structural integrity assessment and design by comparing the measured and calculated values with the reference values for the homogeneous group identified, which can help the engineers review the adequacy of the values and put the group database to practical use.