• Steel and Composite Structures
• /
• 제4권1호
• /
• pp.9-21
• /
• 2004

The present study aims at the reliability analysis of steel towers against the limit state of deflection. For this purpose tip deflection of the tower has been obtained after carrying out the dynamic analysis of the tower using modal method. This tip deflection is employed for subsequent reliability analysis. A limit state function based on serviceability criterion of deflection is derived in terms of random variables. A complete procedure of reliability computation is then presented. To study the influence of various random variables on tower reliability, sensitivity analysis has been carried out. Design points, important for probabilistic design of towers, are also located on the failure surface. Some parametric studies have also been included to obtain the results of academic and field interest.

• Wind and Structures
• /
• 제20권3호
• /
• pp.449-468
• /
• 2015

Current wind-resistance designs of large-scale indirect dry cooling towers (IDCTs) exclude an important factor: the influence of the ventilation rate for radiator shutter on wind loads on the outer surfaces of the tower shell. More seemingly overlooked aspects are the effects of various ventilation rates on the wind pressure distribution on the tower surfaces of two IDCTs, and the feature of the flow field around them. In order to investigate the effects of the radiator shutter ventilation rates on the aerodynamic interference between IDCTs, this paper established the numerical wind tunnel model based on the Computational Fluid Dynamic (CFD) technology, and analyzed the influences of various radiator shutter ventilation rates on the aerodynamic loads acting upon a single and two extra-large IDCTs during building, installation, and operation stages. Through the comparison with the results of physical wind tunnel test and different design codes, the results indicated that: the influence of the ventilation rate on the flow field and shape coefficients on the outer surface of a single IDCT is weak, and the curve of mean shape coefficients is close to the reference curve provided by the current design code. In a two-tower combination, the ventilation rate significantly affects the downwind surface of the front tower and the upwind surface of the back tower, and the larger positive pressure shifts down along the upwind surface of the back tower as the ventilation rate increases. The ventilation rate significantly influences the drag force coefficient of the back tower in a two-tower combination, the drag force coefficient increases with the ventilation rate and reaches the maximum in a building status of full ventilation, and the maximum drag coefficient is 11% greater than that with complete closure.

• Earthquakes and Structures
• /
• 제15권6호
• /
• pp.583-593
• /
• 2018

Seismic performance is particularly important for life-line structures, especially for long-span transmission tower line system subjected to multi-component ground motions. However, the influence of multi-component seismic loads and the coupling effect between supporting towers and transmission lines are not taken into consideration in the current seismic design specifications. In this research, shake table tests are conducted to investigate the performance of long-span transmission tower-line system under multi-component seismic excitations. For reproducing the genuine structural responses, the reduced-scale experimental model of the prototype is designed and constructed based on the Buckingham's theorem. And three commonly used seismic records are selected as the input ground motions according to the site soil condition of supporting towers. In order to compare the experimental results, the dynamic responses of transmission tower-line system subjected to single-component and two-component ground motions are also studied using shake table tests. Furthermore, an empirical model is proposed to evaluate the acceleration and member stress responses of transmission tower-line system subjected to multi-component ground motions. The results demonstrate that the ground motions with multi-components can amplify the dynamic response of transmission tower-line system, and transmission lines have a significant influence on the structural response and should not be neglected in seismic analysis. The experimental results can provide a reference for the seismic design and analysis of long-span transmission tower-line system subjected to multi-component ground motions.

• Structural Engineering and Mechanics
• /
• 제70권4호
• /
• pp.479-497
• /
• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• Structural Engineering and Mechanics
• /
• 제48권6호
• /
• pp.791-807
• /
• 2013

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.

• 국제초고층학회논문집
• /
• 제4권4호
• /
• pp.249-259
• /
• 2015

This paper introduces the structural design and construction method for the foundation of the TOKYO SKYTREE, a new digital broadcasting tower in Tokyo, which has a height of 634 meters. The surface layer of the ground is occupied by soft soil, thus the foundation of this tower is an SRC continuous underground wall pile, designed and developed to have horizontal rigidity and pull-out resistance. The structural integrity and construction method of the wall pile was verified with an on-site full scale pull-out test concluding a maximum load of 40,000 kN.

• 복합신소재구조학회 논문집
• /
• 제5권3호
• /
• pp.37-42
• /
• 2014

Wind turbine tower has a very important role in wind turbine system as one of the renewable energy that has been attracting attention worldwide recently. Due to the growth of wind power market, advance and development of offshore wind system and getting huger capacity is inevitable. As a result, the vibration is generated at wind turbine tower by receiving constantly dynamic loads such as wind load and wave load. Among these dynamic loads, the mechanical load caused by the rotation of the blade is able to make relatively periodic load to the wind turbine tower. So natural frequency of the wind turbine tower should be designed to avoid the rotation frequency of the rotor according to the design criteria to avoid resonance. Currently research of the wind turbine tower, the precise research does not be carried out because of simplifying the structure of the other upper and lower. In this study, the effect of blade modeling differences are to be analyzed in natural frequency of wind turbine tower.

• 설비공학논문집
• /
• 제26권3호
• /
• pp.130-136
• /
• 2014

The present study is performed to set up the framework of cooling tower performance predictions. The performance of mechanical forced draft cooling tower is directly related to the state of a nuclear power plant system, such as the condenser and evaporator. The main parameters related to the state of systems are as follows : wet bulb temperature, dry bulb temperature and absolute humidity. The performance evaluation of cooling tower must be considered at the power plant design. In this study, the toolkit developed by the American Cooling Tower Industry association (CTI) has been used for the framework construction. In order to validate the framework, it is being applied to the cooling tower constructed for the U.S. Nuclear Power Plant. The test results have shown good agreements with the cold water temperature on the cooling tower performance curves provided by manufacturers.

• Wind and Structures
• /
• 제11권6호
• /
• pp.479-496
• /
• 2008

In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.

• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 2006년도 추계공동학술대회
• /
• pp.499-507
• /
• 2006

The tower cranes are widely used in very useful construction machine the sites of constructing high-structure and have a structural sensitiveness. Therefore, the accidents have often happened due to the deficiency of laborer's understanding md lack of safety of structure. Till now, as we have research and studied above, we can properly protect accidents by construction equipments particularly crane as well as most disasters which occur frequently in construction site. The goal of this study is the safety inspection model of the tower crane a construction site, which preventible the collapse accident of tower crane which is constructed by using the correcting frame. In order to accomplish the goal of this study, the field survey, the reference investigation and the structure analysis were performed for the collapse accident of tower nine using the correcting data. This study will be proposed a build-up solutions about operating and release of safety constructions and researched about software safety estimation. Also, preventing safety problems of Tower Crane Construction site as applying safety estimation program and laws and regulations. As a result, The real time control of tower crane inspection system is implemented by to illustrate the application of the adopted optimal design model.