• Structural Engineering and Mechanics
• /
• v.52 no.1
• /
• pp.51-73
• /
• 2014

A three-dimensional finite element model for the Jiashao Bridge, the longest multi-span cable-stayed bridge in the world, is established using the commercial software package ANSYS. Dynamic characteristics of the bridge are analyzed and the effects of structural system measures including the rigid hinge, auxiliary piers and longitudinal constraints between the girders and side towers on the dynamic properties including modal frequency, mode shape and effective mass are studied by referring to the Jiashao Bridge. The analysis results reveal that: (i) the installation of the rigid hinge significantly reduces the modal frequency of the first symmetric lateral bending mode of bridge deck. Moreover, the rigid hinge significantly changes the mode shape and effective mass of the first symmetric torsional mode of bridge deck; (ii) the layout of the auxiliary piers in the side-spans has a limited effect on changing the modal frequencies, mode shapes and effective masses of global vibration modes; (iii) the employment of the longitudinal constraints significantly increases the modal frequencies of the vertical bending modes and lateral bending modes of bridge deck and have significant effects on changing the mode shapes of vertical bending modes and lateral bending modes of bridge deck. Moreover, the effective mass of the first anti-symmetric vertical bending of bridge deck in the longitudinal direction of the fully floating system is significantly larger than that of the partially constrained system and fully constrained system. The results obtained indicate that the structural system measures of the multi-span cable-stayed bridge have a great effect on the dynamic properties, which deserves special attention for seismic design and wind-resistant design of the multi-span cable-stayed bridge.

• Journal of architectural history
• /
• v.22 no.6
• /
• pp.35-46
• /
• 2013

This study aims to examine the early use of Da-bo tap and their transformation by analyzing the various meanings of the term pagoda in Chinese translations, the Sanskrit version of the Lotus Sutra, as well as Dabotap in the Mogao Caves of Dunhuang. In addition, we aim to highlight changes in Dabotap usage, which started out as residential spaces, but transformed into burial spaces over time. The details can be summarized as follows. First, early Buddhist monuments were usually either pagodas serving as burial places for the dead or shrines that were not. A Dabotap is a type of pagoda enshrining the body of Prabhutaratna, and was initially used as a residential space, rather than a burial place for the dead. Second, the terms stupa and caitya are clearly distinguished from each other in the Sanskrit scriptures, and stupa is also further classified into dhatu, sarisa, and atmabhava based on the object being enshrined. In Gyeon-bo-tab-pum, the preconditions for caitya to transform into stupa is presented by explaining that worshipping the space enshrining the body of Prabhutaratna is worthy of the same status as the space enshrining sarira. Third, the Mogao Caves of Dunhuang had been depicted from the Western Wei of the Northern Dynasties until the time of the Yuan Dynasty. It was used as a residential space until the early Sui Dynasty, but was used as both residence and burial places until the Tang Dynasty when pagodas were first being constructed with wheel or circles forms on top, which then gradually changed into stupa (grave towers).

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.879-882
• /
• 2008

The market of Korea of post-tension system for building is growing up since 2000 and many engineers and construction companies show interest in it. This paper introduces the structure system and construction of post-tension tall buildings including recent trend in the industry of post-tension system for buildings in Korea and the point to be considered when design post-tensioned tall building. Park Polis is composed of two towers of 39 stories with a level to the top of the roof +144m and is currently under construction at Ulsan in Korea. This building designed as the unbonded post-tension floor system and will be the tallest and first high-rise post-tensioned building in Korea. The structural system is composed of the flat slabs, perimeter columns and core walls. At first, this building had designed as regular RC flat slab with perimeter beams. However, floor structure system was reconsidered because the construction company wants to improve efficiency of construction. As a result, the floor system of PARK POLIS re-designed as PT flat slab.

• Journal of Advanced Research in Ocean Engineering
• /
• v.4 no.2
• /
• pp.86-95
• /
• 2018

The fluid flow over structures has been widely investigated by many researchers because its extensive application in offshore structures, skyscrapers, chimneys and cooling towers, brides. In the viewpoint of reducing the drag for offshore structure, it becomes challenging problem in the field of hydrodynamic of offshore structure. The purpose of this study is to investigate a flow over a square cylinder with an attached splitter plate using RANS method. First, RANS turbulent models such as a standard $k-{\omega}$ model, SST $k-{\omega}$ model, RNG $k-{\varepsilon}$ model, realizable $k-{\varepsilon}$ model, standard $k-{\varepsilon}$ model were used for choosing suitable turbulent model which has the best agreement with available experimental result. Drag of single cylinder estimated by using standard $k-{\omega}$ has a good agreement with published experimental result. Therefore, the stand $k-{\omega}$ was selected for simulation for flow over a square cylinder with an attached plate. Second, the numerical results of drag of square cylinder with an attached splitter plate in various length of an attached plate were performed using RANS method in ANSYS Fluent. In this paper, the numerical simulations were conducted at a Reynolds number of 485 and the thickness of the splitter plate is chosen as a constant value about 10% of cylinder width. The numerical results of drag coefficient of square cylinder are compared with experimental result published by other researchers. Finally, the effect of the splitter plate attached to the rear side of the square cylinder has been investigated numerically with a focus on the drag coefficient and flow characteristic. As a result, the drag coefficient decreases with an increase in splitter plate length.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.110-112
• /
• 2010

Because the building of new meteorological observation towers requires high cost, a collection of precise meteorological data over city area is not easy. To collect atmosphere environment data or meteorological data precisely, a new approach is required. This paper introduces a new meteorological data collecting system using the public traffic systems such as regular route bus. On real time, the regular route bus can provide a meteorological data in periodic time interval and provide them on static route. Without constructing new facilities, only simple sensing and transmission equipments to attach on the bus are needed.

• Journal of Korean Association for Spatial Structures
• /
• v.12 no.3
• /
• pp.97-104
• /
• 2012

In the design procedure of the cooling tower the form-finding of the shell is the most important process, because the shape of the shell determines the sensitivity of dynamic behaviour of the whole tower against wind excitation. In engineering practice, geometric parameters of the shell are generally determined based on natural frequency analysis. 32 cooling tower shell geometries were selected through variation of the geometric parameters of an existing cooling tower shell. They were evaluated based on the first natural frequency. From the result three representative cooling towers are selected for the analysis of the structural behaviour by means of linear FE-method. As a result, a hyperbolic rotational shell with the small radius overall will yield the shell geometry with a higher first natural frequency and thus a wind-insensitive structure.

• Composites Research
• /
• v.25 no.2
• /
• pp.54-61
• /
• 2012

In this study, a specific structural design procedure for 2 MW class glass/epoxy composite wind turbine system towers is newly proposed through load case study, trade-off study, optimal structural design and structural analysis. Optimal tower design is very important because its cost is about 20% of the wind turbine system's cost. In the structural design of the tower, three kinds of loads such as wind load, blades, nacelle and tower weight and blade aerodynamic drag load should be considered. Initial structural design is carried out using the netting rule and the rule of mixture. Then the structural safety and stability are confirmed using a commercial finite element code, MSC NASTRAN/PATRAN. The finally proposed tower configuration meets the tower design requirements.

• Structural Engineering and Mechanics
• /
• v.50 no.2
• /
• pp.241-255
• /
• 2014

The girder of self-anchored suspension bridge is subjected to large compression force applied by main cables. So, serious damage of the girder due to breakage of hangers may cause collapse of the whole bridge. With the time increasing, the hangers may break suddenly for their resistance capacities decrease due to corrosion. Using nonlinear static and dynamic analysis methods and adopting 3D finite element model, the responses of a concrete self-anchored suspension bridge to sudden breakage of hangers are studied in this paper. The results show that the sudden breakage of a hanger has significant effects on tensions of the hangers next to the broken hanger, bending and torsion moments of the girder, moments of the towers and reaction forces of the bearings. The results obtained from dynamic analysis method are very different from those obtained from static analysis method. The maximum tension of hanger produced by breakage of a hanger exceeds 2.2 times of its initial value, the maximum dynamic amplification factor reaches 2.54, which is larger than the value of 2.0 recommended for cable-stayed bridge in PTI codes. If two adjacent hangers on the same side of bridge break one after another, the maximum tension of other hangers exceeds 3.0 times of its initial value. If the safety factor adopted to design hanger is too small, or the hangers have been exposed to corrosion, the bridge may collapse due to breakage of two adjacent hangers.

• Structural Engineering and Mechanics
• /
• v.34 no.6
• /
• pp.719-738
• /
• 2010

The aim of this paper concerns with the nonlinear analysis of cable-stayed bridges including the vibration effect of cable stays. Two models for the cable stay system are built up in the study. One is the OECS (one element cable system) model in which one single element per cable stay is used and the other is MECS (multi-elements cable system) model, where multi-elements per cable stay are used. A finite element computation procedure has been set up for the nonlinear analysis of such kind of structures. For shape finding of the cable-stayed bridge with MECS model, an efficient computation procedure is presented by using the two-loop iteration method (equilibrium iteration and shape iteration) with help of the catenary function method to discretize each single cable stay. After the convergent initial shape of the bridge is found, further analysis can then be performed. The structural behaviors of cable-stayed bridges influenced by the cable lateral motion will be examined here detailedly, such as the static deflection, the natural frequencies and modes, and the dynamic responses induced by seismic loading. The results show that the MECS model offers the real shape of cable stays in the initial shape, and all the natural frequencies and modes of the bridge including global modes and local modes. The global mode of the bridge consists of coupled girder, tower and cable stays motion and is a coupled mode, while the local mode exhibits only the motion of cable stays and is uncoupled with girder and tower. The OECS model can only offers global mode of tower and girder without any motion of cable stays, because each cable stay is represented by a single straight cable (or truss) element. In the nonlinear seismic analysis, only the MECS model can offer the lateral displacement response of cable stays and the axial force variation in cable stays. The responses of towers and girders of the bridge determined by both OECS- and MECS-models have no great difference.

• Journal of the Korean Solar Energy Society
• /
• v.37 no.6
• /
• pp.103-114
• /
• 2017

Radiation energy budget was analyzed using observation data from the Weather Information Service Engine (WISE) energy flux tower on the Seoul metropolitan area. Among observation data from the 13 energy flux towers, we used meteorological variables, radiation data (upward and downward short wave, upward and downward long wave, net short wave, net long wave and net radiation), albedo and emissivity for 15 months from July 2016 to September 2017. Although Gajwa (205) and Ttuksumm (216) sites located in urban, the albedo was relatively high due to the surround environment by glass wall buildings and the Han river around the sites. And Bucheon (209) site located in the suburb represented generally low emissivity. As a result, the albedo decreased and the emissivity increased in the city center. In the Seoul metropolitan area, the net radiation energy is $73.9W/m^2$ that the radiation budget of the surface is absorbed into the atmosphere. According to WISE observation data, it can be seen that observation at each sites are influenced by the surrounding environment.