• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.25 no.9
• /
• pp.620-627
• /
• 2015

Long continuous bridge deck can become contracted considerably as temperature drops, which can lead to a large expansion of sleeper span at the end of it. Since this huge sleeper span then can cause problems both with safety of train operation and structural stability of tracks, it is necessary to take the issue into consideration systematically in the designing process of the bridge. In this paper, an evaluation process through the analysis of train-track interaction was presented which can basically review the effects of the expansion of sleeper span at the end of long continuous bridge deck on the safety of the train and the structural stability of the track. The analyses of the interaction between the light rail train and tracks were carried out targeting the sleeper span as a main parameter. The safety of train operation and structural stability of tracks in a light rail system due to the expansion of the sleeper span were evaluated by comparing the numerical results with the related criteria.

• Earthquakes and Structures
• /
• v.16 no.6
• /
• pp.665-677
• /
• 2019

This study utilizes large-scale shake table test to investigate the seismic performance of an isolated bridge with lead rubber bearings crossing an active fault. Two transverse restraining systems with and without shear keys are tested by applying spatially varying ground motions. It is shown that the near-fault span exhibits larger bearing displacement than the crossing-fault span. Bridge piers away from the fault rupture are more vulnerable than those adjacent to the fault rupture by attracting more seismic demand. It is also verified that the shear keys are effective in restraining the bearing displacement on the near-fault span, particularly under the large permanent ground displacement.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.1
• /
• pp.5-16
• /
• 2015

In the long span bridge construction, construction cost portion of large scale marine foundation is about 40% (KICTEP, 2007). In this study, designs for deep water depth large composite foundation of a super long span cable-stayed girder bridge of prototype were performed by three design methods (ASD, LRFD, Eurocode) and the behaviors of a large diameter drilled shaft were analyzed and the 3D numerical analysis was performed. As a result, the soft rock socket lengths in allowable stress design estimation method were the longest. The soft rock socket lengths estimated by the design approach 2 among Eurocode and the LRFD were similar. The longer the socket length socketed in the soft rock was, the smaller the axial force acting on a large-diameter drilled shaft head was and the smaller the settlement of drilled shaft was.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.04a
• /
• pp.427-439
• /
• 2003

A previous study evaluated the seismic response of typical multi-span simply supported (MSSS) and multi-span continuous (MSC) steel-girder bridges in the central and southeastern United States. The results showed that the bridges were vulnerable to damage resulting from impact between decks, and large ductility demands on nonductile columns. Furthermore, fixed and expansion bearings were likely to fail during strong ground motion. In this paper, several retrofit measures to improve the seismic performance of typical multi-span simply supported and multi-span continuous steel girder bridges are evaluated, including the use of elastomeric bearings, lead-rubber bearings, and restrainer cables. It is determined that lead-rubber bearings are the most effective retrofit measure for reducing the seismic vulnerability of typical bridges. While isolation provided by elastomeric bearings limits the forces into the columns, the added flexibility results in pounding between decks in the MSSS steel-girder bridge. Restrainer cables, which are becoming a common retrofit measure, are only moderately effective in reducing the seismic vulnerability of MSSS and MSC steel girder bridges.

• Architectural research
• /
• v.19 no.4
• /
• pp.109-115
• /
• 2017

This study is done to evaluate how existence of shear-span ratio and shear reinforcing bar effects on shear performance from through shear experiment using PVA fiber reinforced ferroconcrete building. Ratio of shear-span was set 1, 1.7, and arrangement of shear reinforcing bar was set with KCI2012 regulation. In result, subject with less shear-span ratio, and shear reinforcing bar with arrangement of bar shows high stiffness. Subjects with high shear-span ratio show large difference depending on existence of shear reinforcing bar. Therefore, theoretical shear strength followed by CEB code underestimates experimental shear strength by 43.9%. Shear strength of the deep beam with headed bars is more affected by the bearing strength of head than the bond strength of bar.

• Journal of information and communication convergence engineering
• /
• v.19 no.4
• /
• pp.199-204
• /
• 2021

We propose a dispersion-managed link with a non-midway optical phase conjugator (OPC), in which the residual dispersion per span (RDPS) of each fiber span is different for each transmission section before and after OPC. We numerically demonstrate the compensation for 960-Gb/s wavelength-division multiplexed (WDM) signals distorted by chromatic dispersion and Kerr nonlinearity of the fiber. We consider different cases for non-midway OPC, including six fiber spans - OPC - 14 fiber spans and 14 fiber spans - OPC - 6 fiber spans. The numerical results show that the compensation of the distorted 960 Gb/s WDM is more efficient when the OPC is placed after 6-th fiber span as compared to after the 14-th fiber span. Our simulation results also indicate that the compensation effect increases when the difference in net residual dispersion between both transmission sections is not large, but they are not the same. Under this condition, the larger the magnitude of the RDPSs of each fiber span, the greater the compensation.

• Journal of Advanced Navigation Technology
• /
• v.17 no.1
• /
• pp.16-23
• /
• 2013

The effects of dispersion coefficient of dispersion compensating fiber (DCF) and residual dispersion per span (RDPS) on in the dispersion managed optical links for compensating the distorted 960 Gbps wavelength division multiplexd (WDM) signals due to group velocity dispersion (GVD) and optical nonlinear effects of single mode fiber (SMF) are investigated. It is confirmed that optimal net residual dispersion (NRD), which greatly affects compensating for optical signals, should be induced under the large launch power condition, irrelevant on the considered dispersion coefficient of DCF and RDPS. It is also confirmed that system performances are greatly improved by selecting the very small RDPS and very large dispersion coefficient of DCF.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.1
• /
• pp.61-67
• /
• 2012

Spreading sequence is used for spreading spectrum in CDMA. For the purpose of minimizing multiple access interference and expanding linear span of the sequences, it is desirable to use such sequences with low correlation and high linear span. To obtain large family size and high linear span, the values of the correlation function of the sequences is more complex. In this paper, we propose the extended Zeng sequences with large family size and high linear span and analyze the correlation of the sequences.

• International Journal of High-Rise Buildings
• /
• v.11 no.4
• /
• pp.287-300
• /
• 2022

Unconventional structures are getting more popular in recent days. Large-span roofs are used for many structures, such as airports, stadiums, and conventional halls. Identifying the pressure distribution and wind load acting on those structures is essential. This paper offers a collaborative study of computational fluid dynamics (CFD) simulations and wind tunnel tests for assessing wind pressure distribution for a building with a combined slender curved roof. The hybrid turbulence model, Improved Delayed Detached Eddy Simulation (IDDES), simulates the open terrain turbulent flow field. The wind-induced local pressure coefficients on complex roof structures and the turbulent flow field around the structure were thus calculated based upon open terrain wind flow simulated with the FLUENT software. Local pressure measurements were investigated in a boundary layer wind tunnel simultaneous to the simulation to determine the pressure coefficient distributions. The results predicted by CFD were found to be consistent with the wind tunnel test results. The comparative study validated that the recommended IDDES model and the vortex method associated with CFD simulation are suitable tools for structural engineers to evaluate wind effects on long-span complex roofs and plan irregular buildings during the design stage.

• Structural Engineering and Mechanics
• /
• v.53 no.3
• /
• pp.607-623
• /
• 2015

The wind-induced dynamic response of large-span flexible structures includes two important components-background response and resonant response. However, it is difficult to separate the two components in time-domain. To solve the problem, a relational expression of wavelet packet coefficients and power spectrum is derived based on the principles of digital signal processing and the theories of wavelet packet analysis. Further, a new approach is proposed for separation of the background response from the resonant response. Then a numerical example of frequency detection is provided to test the accuracy and the spectral resolution of the proposed approach. In the engineering example, the approach is applied to compute the power spectra of the wind-induced response of a large-span roof structure, and the accuracy of spectral estimation for stochastic signals is verified. The numerical results indicate that the proposed approach is efficient and accurate with high spectral resolution, so it is applicable for power spectral computation of various response signals of structures induced by the wind. Moreover, the background and the resonant response time histories are separated successfully using the proposed approach, which is sufficiently proved by detailed verifications. Therefore, the proposed approach is a powerful tool for the verification of the existing frequency-domain formulations.