• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.6
• /
• pp.645-654
• /
• 2011

Temporal supports is proposed for the large block construction of a double-deck truss girder of a bundle type cable-stayed bridge. The design force of the temporal bents cannot be evaluated by a conventional design procedure with gust factored static wind loads. The uplift forces in BS5400 also can not estimate the design forces of the temporal bents properly for the turbulent wind loads. A frequency-domain buffeting analysis is performed to evaluate the design forces of the temporal bents considering the interactions between the girder and temporal supports. Two cases of modeling are compared to estimate the stiffness contribution of temporal supports in determining design forces, i.e., an analysis model including temporal bents in the structural analysis modeling and an analysis model with fixed supports at the bent tops neglecting the stiffness of temporal bents. The consideration of bent stiffness usually generates smaller reaction forces than rigid support modeling. Consequently, the effectiveness and usefulness of the buffeting analysis procedure with full modeling of temporal supports are demonstrated for the design of a temporal bents of the construction of a bundle type cable-stayed bridge.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.6
• /
• pp.449-458
• /
• 2016

The temperature data were measured for two years in a bridge specimen and the bridge in service nearby in order to calculate the effective temperature for thermal loads in steel box girder bridge. The maximum and minimum effective temperatures were calculated in the bridge specimen and the bridge according to air temperature in 2014, 2015 and 2years. The effective temperatures calculated in this study were compared the Euro code and the Highway Bridge Design Criteria. The coefficients of determination in the maximum effective temperature and the Euro code for 2 year were calculated from R = 0.927, R = 0.894 in a bridge specimen and the bridge respectively. Those of minimum temperature and the Euro code were analyzed from R = 0.992, R = 0.813 in two bridge respectively. Also, the results were evaluated as being very similar, or slightly increased as compared with the maximum temperature of the Korean Highway Bridge Design Code(Limit State Design).

• Steel and Composite Structures
• /
• v.7 no.6
• /
• pp.487-502
• /
• 2007

In recent decades there has been a trend towards improved mechanical characteristics of materials used in footbridge construction. It has enabled engineers to design lighter, slender and more aesthetic structures. As a result of these construction trends, many footbridges have become more susceptible to vibrations when subjected to dynamic loads. In addition to this, some inherit modelling uncertainties related to a lack of information on the as-built structure, such as boundary conditions, material properties, and the effects of non-structural elements make difficult to evaluate modal properties of footbridges, analytically. For these purposes, modal testing of footbridges is used to rectify these problems after construction. This paper describes an arch type steel footbridge, its analytical modelling, modal testing and finite element model calibration. A modern steel footbridge which has arch type structural system and located on the Karadeniz coast road in Trabzon, Turkey is selected as an application. An analytical modal analysis is performed on the developed 3D finite element model of footbridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests on the footbridge deck under natural excitation such as human walking and traffic loads are conducted. The output-only modal parameter identification is carried out by using the peak picking of the average normalized power spectral densities in the frequency domain and stochastic subspace identification in the time domain, and dynamic characteristics such as natural frequencies mode shapes and damping ratios are determined. The finite element model of footbridge is calibrated to minimize the differences between analytically and experimentally estimated modal properties by changing some uncertain modelling parameters such as material properties. At the end of the study, maximum differences in the natural frequencies are reduced from 22% to only %5 and good agreement is found between analytical and experimental dynamic characteristics such as natural frequencies, mode shapes by model calibration.

• Journal of the Korea Concrete Institute
• /
• v.22 no.2
• /
• pp.247-254
• /
• 2010

The purpose of study is to investigate the load resistance mechanism of MRS continuous joint designed with different details. Six full-scale specimens, which could simulate the negative moment region of the 8 m long MRS system, were prepared to evaluate the structural performance of the continuous joint. According to the experimental results, all specimens which include the specimen with dapped ends designed by loads at the construction stage were failed in a flexural manner and showed the load carrying capacity over the nominal flexural strength. Therefore it is recommended that the dapped ends for MRS continuous joints be designed for the loads of the construction stage. And the shear key, which was installed on the top of rib for MRS slab, helps the enhancement of strength and especially deformation capacity.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.14 no.2
• /
• pp.28-39
• /
• 2011

This study estimates the characteristics of flow loads by classification items of the Ministry of Environment and by land cover change using HyGIS-SWAT. The result of analyzing the land cover change using the classification items shows that the urban area and the farmland area in Mishim-cheon and Gap-cheon are expanding while the forest area is decreasing. The result of analyzing the characteristics of classification items shows that peak discharge increases and total yearly discharge decreases in Mushim-cheon. The result of analyzing the characteristics by data-construction period shows that peak discharge decreases but total discharge increases in Gap-cheon. Three land cover change scenarios are applicable to the expansion of urban area and farmland area. According to the result of application, urbanization influences and Farmland area expansion influences increase peak discharge, total yearly discharge and sediment concentration.

• Earthquakes and Structures
• /
• v.23 no.5
• /
• pp.403-417
• /
• 2022

Reinforced concrete (RC) structures with low-strength RC columns are rampant in several countries, especially those constructed during the early 1960s and 1970s. The weakness of these structures due to overloading or some natural disasters such as earthquakes and building age effects are some of the main reasons to collapse, particularly with the scarcity of data on the impact of aspect ratio and corner radius on the confinement effectiveness. Hence, it is crucial to investigate if these columns (with different aspect ratios) can be made safe by strengthening them with carbon fiber-reinforced polymers (CFRP) sheets. Therefore, experimental and numerical studies of CFRP-strengthened low-strength reinforced concrete short rectangular, square, and circular columns were studied. In this investigation, a total of 6 columns divided into three sets were evaluated. The first set had two circular cross-sectional columns, the second set had two square cross-section columns, and the third set has two rectangular cross-section columns. Furthermore, FEM validation has been conducted for some of the experimental results obtained from the literature. The experimental results revealed that the confinement equations for RC columns as per both CSA and ACI codes could give incorrect results for low-strength concrete. The control specimen (unstrengthened ones) displayed that both ACI and CSA equations overestimate the ultimate strength of low-strength RC columns by order of extent. For strengthened columns with CFRP, the code equations of CSA and ACI code overestimate the maximum strength by around 6 to 13% and 23 to 29%, respectively, depending on the cross-section of the column (i.e., square, rectangular, or circular). Results of finite element models (FEMs) showed that increasing the layer number of new commonly CFRP type (B) from one to 3 for circular columns can increase the column's ultimate loads by around eight times compared to unjacketed columns. However, in the case of strengthened square and rectangular columns with CFRP, the increase of the ultimate loads of columns can reach up to six times and two times, respectively.

• Advances in nano research
• /
• v.16 no.6
• /
• pp.623-638
• /
• 2024

This study investigates the thermal post-buckling behavior of concrete eccentric annular sector plates reinforced with graphene oxide powders (GOPs). Employing the minimum total potential energy principle, the plates' stability and response under thermal loads are analyzed. The Haber-Schaim foundation model is utilized to account for the support conditions, while the transform differential quadrature method (TDQM) is applied to solve the governing differential equations efficiently. The integration of GOPs significantly enhances the mechanical properties and stability of the plates, making them suitable for advanced engineering applications. Numerical results demonstrate the critical thermal loads and post-buckling paths, providing valuable insights into the design and optimization of such reinforced structures. This study presents a machine learning algorithm designed to predict complex engineering phenomena using datasets derived from presented mathematical modeling. By leveraging advanced data analytics and machine learning techniques, the algorithm effectively captures and learns intricate patterns from the mathematical models, providing accurate and efficient predictions. The methodology involves generating comprehensive datasets from mathematical simulations, which are then used to train the machine learning model. The trained model is capable of predicting various engineering outcomes, such as stress, strain, and thermal responses, with high precision. This approach significantly reduces the computational time and resources required for traditional simulations, enabling rapid and reliable analysis. This comprehensive approach offers a robust framework for predicting the thermal post-buckling behavior of reinforced concrete plates, contributing to the development of resilient and efficient structural components in civil engineering.

• International Journal of Concrete Structures and Materials
• /
• v.7 no.4
• /
• pp.319-332
• /
• 2013

The purpose of this study was to investigate the design comparison of totally prefabricated bridge substructure system. Prefabricated bridge substructure systems are a relatively new and versatile alternative in substructure design that can offer numerous benefits. The system can reduce the work load at a construction site and can result in shorter construction periods. The prefabricated bridge substructures are designed by the methods of Korea Highway Bridge Code (KHBD) and load and resistance factor design (AASHTO-LRFD). For the design, the KHBD with DB-24 and DL-24 live loads is used. This study evaluates the design method of KHBD (2005) and AASHTO-LRFD (2007) for totally prefabricated bridge substructure systems. The computer program, reinforced concrete analysis in higher evaluation system technology was used for the analysis of reinforced concrete structures. A bonded tendon element is used based on the finite element method, and can represent the interaction between the tendon and concrete of a prestressed concrete member. A joint element is used in order to predict the inelastic behaviors of segmental joints. This study documents the design comparison of totally prefabricated bridge substructure and presents conclusions and design recommendations based on the analytical findings.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.411-418
• /
• 2002

In domestic road construction sites, the compaction control based on strength are widely performed through the direct method with high accuracy, such as Plate Loading Test or Field CBR test. It is impossible to manage all construction sites using the direct method because the direct method requires heavy reaction loads and long measurement time. Therefore, it is necessary to apply the indirect method that could control the relative density of construction sites on the whole. Indirect methods, such as Cone Penetration Test and Fall Cone Test, require extra time for data analyzing and fixed area for test device. In this paper, the field applicability of Soil Impact Hammer (SIH) was investigated comparing with the results of field measurement tests and laboratory compaction tests. SIH developed by Japan Construction Administration and Asanuma Ltd., is a kind of indirect methods for compaction checking. According to the results of SIH performed in domestic road construction site, the subgrade reaction modulus obtained from SIH are similar to that from Plate loading tests in the range of 10 to 40. In comparison with laboratory compaction test, similar compaction line are shown in the dry side of optimum moisture contents.

• International conference on construction engineering and project management
• /
• 2009.05a
• /
• pp.230-236
• /
• 2009

Double-front construction machinery, which was designed for complicated tasks, requires intelligent systems that can provide the quantitative work analysis needed to determine effective work procedures and that can provide operational and cognitive support for operators. Construction work environments are extremely complicated, however, and this makes state identification difficult. We therefore defined primitive static states (PSS) that are determined using on-off data for the lever inputs and manipulator loads for each part of the grapple and front and that are completely independent of the various environmental conditions and operator skill levels. To confirm the usefulness of PSS, we performed experiments with a demolition task by using our virtual reality simulator. We confirmed that PSS could robustly and accurately identify the work states and that untrained skills could be easily inferred from the PSS-based work analysis. We also confirmed in skill-training experiments that advice information using PSS-based skill analysis greatly improved work performance. We thus confirmed that PSS can adequately identify work states and are useful for work analysis and skill improvement.