Hyperbolic Cooling Towers Research Articles

Study of Wind Loads on Free-Standing and Closely Spaced Hyperbolic Cooling Towers

Introduction. The construction of cooling towers has always been and remains a pressing issue in today's world. Wide spreading of cooling towers is necessary for power industry. The problem lies in the allowable location of a set of hyperbolic cooling towers at a premises of a single fuel-and-energy facility. The aim of the present study is to investigate the wind pressure distribution on a cooling tower having the shape of a single-cavity hyperboloid of rotation and the cross-interference of the closely spaced cooling towers. To achieve the set forth aim the following objectives are being solved: the finite-element modeling of a free-standing and several closely spaced structures, the analysis of the wind pressure isofields at different elevations and the comparison of the results with the currently valid standards.Materials and methods. The object of the study is the hyperboloid type cooling towers of total height 53.3 m. The analysis is carried out with the help of the three-dimensional finite-element modeling in the CFX module of the verified ANSYS software package. The k-epsilon turbulence model is used. For simplification, the wind speed is assumed constant along the structure’s height. The shells in the shape of a single-cavity hyperboloid including the airspace are specified by a parametric equation, which is modeled by using the solid finite elements in the form of tetrahedrons. The surface of the shells is assumed to be perfectly smooth. Besides finite-element analysis, the calculation of the interference factor is made according to the standards currently valid for reinforced concrete cooling towers.Results. The results of wind pressure distribution on free-standing and closely spaced cooling towers were obtained. The data on the wind pressure isofields at various elevations at various locations of tower structures was given.Discussion and conclusions. Upon comparing the obtained results with the currently valid SP 20.13330.2016 «Loads and actions» and SP 340.1325800.2017 «Reinforced concrete and concrete structures of cooling towers. Design rules» it was found that the distribution of wind pressure along circumference depends on the height, which had not been taken into account in the regulatory documentation. The analysis of cross-interference of the closely spaced cooling towers was carried out and it was demonstrated that in the currently valid standards the interference factor had been greatly overestimated.

Analysis of Reliability and Seismic Appraisal of a Reinforced Concrete Hyperbolic Cooling Tower

A reinforced concrete hyperbolic cooling tower of a thermal power plant was built and put into operation in the late 1990s. To understand the current status of the structure, reliability, and seismic appraisal was carried out on the structure. Through field testing, investigations were conducted on structural damage, crack distribution, and tilting conditions. Through finite element analysis, combined with field testing conditions and previous design drawings, the safety and seismic performance of the structure were reviewed. This paper aims to provide guidance for the inspection and appraisal of reinforced concrete hyperbolic cooling towers and to provide valuable references for decision-makers and practitioners encountering similar problems in engineering practice.

Failure process and ultimate strength of RC hyperbolic cooling towers under equivalent static wind loads

Wind induced failure process of RC hyperbolic cooling towers (HCTs) considering material nonlinearity was investigated numerically. Following a detailed introduction and several numerical verifications on the material models of concrete and reinforcement and the layered shell element, the failure process, ultimate strength and failure mechanics of a tower under two load cases, with or without winter temperature, were discussed via the load–displacement curves, distribution and evolution of cracking, stress and internal forces. Loss of the load-carrying capacity is preceded by severe cracking of concrete in windward; and yielding of reinforcement in windward when winter temperature is not included.

A Study on Dynamic Behavior of Natural Draft Cooling Tower Considering the Effect of Soil-Structure Interaction

In this present era, the technology in advanced construction has developed to a very large extent. Some parts of the constructions are still in the improving stage which includes Cooling tower Construction. Hyperbolic cooling towers are large, thin shell reinforced concrete structures which Contribute to power generation efficiency, reliability, and to environmental protection. Cooling towers use evaporation of water to eject heat from processes such as cooling the circulating water used in oil refineries and in power plants. Nowadays in many thermal power plants, we can see the Cooling tower. So, preserving this industrial structure is an effort to save the cooling tower from dangerous earthquakes. The present-day cooling towers are exceptional structures in view of their sheer size and complexities. Present paper deals with the study of dynamic response that is modal analysis, seismic analysis of the two different cooling towers varying the H/t ratio and thicknesses with fixity at the base boundary condition, and the soil is modelled as raft for the effect of soil-structure interaction using the direct approach. In this paper, hyperbolic cooling towers are modelled using Ansys software, which is a Finite element Software. Results show that the soil-structure interaction effect significantly modifies the earthquake behavior of Hyperbolic Cooling towers.

A Simplified Procedure for the Structural Reinforcement Design of Hyperbolic Cooling Tower Shells

A Simplified Procedure for the Structural Reinforcement Design of Hyperbolic Cooling Tower Shells

Seismic responses of hyperbolic cooling towers under horizontal and vertical earthquake

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.

Review on: Construction Technique of Hyperbolic Cooling Tower

Review on: Construction Technique of Hyperbolic Cooling Tower

Cooling performance of cylinder-frustum natural draft dry cooling tower

Cooling towers are an important part of thermal power plants, and applications of steel cooling towers have increased in recent years. Hyperbolic cooling towers (HCTs) have a traditional geometry. However, this style may be less suitable for steel structures, owing to its construction difficulties. A simpler tower shape is beneficial for constructing steel structures, as it improves construction efficiency and reduces costs. Therefore, the cylinder-frustum cooling tower (CFCT) was selected as the research object in this study. The cooling performance of CFCTs was studied experimentally and by numerical simulations. In the experiment, the particle image velocimetry (PIV) technique was introduced to measure the velocity inside the tower. The results show that the cooling performance of the HCT and that of the CFCT were mostly similar in no-wind conditions. In the numerical simulation, two cooling tower heights were researched to ensure the validity of the results. The influence of geometric parameter p, which is the ratio of frustum height to the shell height, on the cooling performance was studied via computational fluid dynamics (CFD), and recommended geometric parameters were proposed. The recommended value range p for the CFCT is 0.3–0.5.

Studies on the influence factors of wind dynamic responses on hyperbolic cooling tower shells

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells are complicated functions of structure and wind properties, such as the fundamental frequency fmin, damping ratio zeta wind velocity V, correlationship in meridian direction and so on, but comprehensions on the sensitivities of the dynamic responses to these four factors are still limited and disagree from each other. Following the dynamic calculation in time domain, features of dynamic effects were elaborated, focusing on the background and resonant components SigmaB and SigmaR, and their contributions to the total rms value SigmaT. The SigmaR is always less than SigmaB when only the maximum SigmaT along latitude is concerned and the contribution of SigmaR to SigmaT varies with responses and locations, but the SigmaR couldn\'t be neglected for structural design. Then, parameters of the above four factors were artificially adjusted respectively and their influences on the gust responses were illustrated. The relationships of SigmaR and the former three factors were expressed by fitted equations which shows certain differences from the existing equations. Moreover, a new strategy for wind tunnel tests aiming at surface pressures and the following dynamic calculations, which demands less experiment equipment, was proposed according to the influence from meridian correlationship.

Parametric Analysis of Hyperbolic Cooling Tower under Seismic Loads, Wind Loads and Dead Load through Staad. Pro

Parametric Analysis of Hyperbolic Cooling Tower under Seismic Loads, Wind Loads and Dead Load through Staad. Pro

Wind induced dynamic responses on hyperbolic cooling tower shells and the equivalent static wind load

Wind induced dynamic responses on hyperbolic cooling tower (HCT) shells and the equivalent static wind load (ESWL) are prime concerns for structural designers and researchers. Followed the dynamic calculation in time domain, using the wind pressure got from wind tunnel tests, the dynamic effects of internal forces and displacement of HCT shell were illustrated through the peak factor g and gust response factor G. The original 2-D distribution of G along latitude and meridian directions was degenerated reasonably to 1-D distribution just along meridian direction and the 2-D distribution of g to a single value, according to the structure behaviors, characteristics of dynamic responses and structural design principles of HCT shell. Based on these features of HCT shell and degenerations of g and G, a new approach pursuing ESWL was proposed whose objective is the reinforcement amount but not the internal forces. The ESWL is got by simple amplification of the mean wind load with a single parameter γ, but the γ used for the latitude and meridian directions are independent and the former is much larger. This is the actual reflection of the independent structural design and different dynamic effects of internal forces in latitude and meridian directions.

Progressive Collapse of Hyperbolic Cooling Tower Considering the Support Inclinations

Progressive Collapse of Hyperbolic Cooling Tower Considering the Support Inclinations

Extreme Wind Pressures and Non-Gaussian Characteristics for Super-Large Hyperbolic Cooling Towers Considering Aeroelastic Effect

AbstractSuper-large hyperbolic cooling towers (SCT) are typical cylinder-like structures and feature spatial, three-dimensional (3D), circumferential motion characteristics, wherein the non-Gaussian probability distribution characteristics of local fluctuating wind pressures involved with vortex shedding or reattachment phenomena are excessive compared with the traditional wind load theoretical system based on Gaussian assumption. In this paper, the stochastic distribution characteristics of fluctuating wind pressures for the SCT (H=215 m) in the Jiangxi nuclear power plant with aeroelastic effect based on synchronous pressure and vibration wind tunnel test were investigated, then the formation mechanism of non-Gaussian fluctuating wind pressures was further revealed. According to the formation mechanism, the probability distribution characteristics, spatial correlation, criterion, and division of non-Gaussian fluctuating wind pressures were discussed in detail. Finally, the prediction method and distrib...

Finite Element Analysis of Glass Fiber Reinforced Plastic Hyperbolic Natural Draft Cooling Tower

Applicating the finite element analysis software Ansys to do finite element analysis of a glass fiber reinforced plastic hyperbolic natural draft cooling tower .Under the working condition of gravity and wind load, to contrast the two models of the presence or absence of abdominal rod displacement, stress and unit axial force, and check the stability of compressive bar, and structural optimization. Analysis results can provide reference for the structural design of hyperbolic cooling tower.

Analysis and Design of Strengthened Hyperbolic Cooling Tower by Using PDS Module in ANSYS

In consideration of the uncertain factors, a hyperbolic cooling tower with initial geometrical imperfections is studied by the PDS module in ANSYS. Contrastive analysis is made on stress, internal force, displacement and failure probability of cooling tower shell. It is indicated that the value of Mx and Ty is sensitive to the initial geometrical imperfections, and the failure of shell in imperfections increase in large. On top of this, the non-local cooling tower shell strengthened with FRP is found to solve the insufficient capacity, which is proved to be feasible. Lastly, the reliability analysis and design of tower shell strengthened with FRP are also carried out. It is proved that the probability design of strengthened shell can assure structure to meet the requirement of target reliability.

Analysis and Design of Strengthened Hyperbolic Cooling Tower by Using PDS Module in ANSYS

Analysis and Design of Strengthened Hyperbolic Cooling Tower by Using PDS Module in ANSYS

The Influence of Stochastic Imperfection Field on the Bearing Capacity of Hyperbolic Cooling Towers

The uncontrollable factors such as construction errors, material inhomogeneity, etc. will inevitably lead to a certain initial imperfections. It is generally known that the stochastic initial imperfection of the structure is an important factor for affecting structural stability and bearing capacity. Since these imperfections are random in nature, this paper proposes the method mainly based on the standard orthogonal basis to expand the stochastic field, taking into account the decomposition of the stochastic initial imperfections related to structures, which is projected in the buckling mode orthogonal basis. In the end, the article by the stability analysis example shows that this method can use less random variables effectively describing the original stochastic imperfection field, and efficiently search for the most unfavorable initial imperfection distribution form in order to ensure the imperfection sensitivity structures have a higher reliability, so it can be applied to large-scale engineering structure stochastic imperfection analysis.

Self-Weight Stresses in Hyperbolic Cooling Towers of General Shape

Explicit analytical results are developed for self-weight membrane stresses in hyperbolic cooling towers of general shape, for a number of different patterns of shell-thickness variation along a meridian of the shell of revolution. The very general nature of the results makes them particularly useful in obtaining quick estimates of dead-weight stresses for structures of this type, and any desired parametric studies may readily be undertaken, permitting the designer to choose the most optimum shell-thickness variation for a given combination of geometric parameters of the hyperboloid of revolution. The results are intended for use during the preliminary phase of the design process. Other equally important effects (such as wind loading and thermal gradients) are best taken into account numerically using the finite element method, and will therefore not be treated in this paper. Some numerical results for self-weight stresses are then obtained on the basis of special but very practical cases, and an analysis of these results reveals interesting design implications.

Hyperbolic Cooling Towers with Bulge Imperfections

Owing to the large expanse of cooling towers, it is not possible to maintain the exact shape of a tower during construction. Alterations in shape also occur due to secondary effects like shrinkage and cracking. These alterations cause the failure of some towers. This paper deals with the application of semiloof shell elements in the analysis of towers with bulge imperfections for both dead and wind loads. Four parameters, namely, (1) radial error amplitude, ζ\im, (2) vertical location of bulge, \iZ\i\dm, (3) vertical extent of bulge, \ih, and (4) angular extent of bulge, Θ\i\dm, have been identified as responsible in influencing the behavior of imperfect towers. Their influence has been studied in detail and most critical geometry of the tower has been arrived at. The behavior of a tower with most critical geometry has also been studied. Analysis suggests that the effect of bulge imperfections on stress resultants is localized, the development of hoop tension in the imperfection zone is of primary concern, and stress changes induced are greater if the imperfection is located closer to the base. Shorter wavelength of an imperfection is more severe since curvature error is significantly high for low wavelength. With increase in angular extent, the change in hoop force is maximum for axisymmetric imperfection. Critical hoop stresses develop around the 70° meridian, where high hoop tension and high meridional moments develop that can induce yielding of hoop reinforcement and consequent failure.

Discussion of “ Tolerance Limits for Geometric Imperfections in Hyperbolic Cooling Towers ” by A. Alexandridis and N. J. Gardner (August, 1992, Vol. 118, No. 8)

Discussion of “ <i>Tolerance Limits for Geometric Imperfections in Hyperbolic Cooling Towers</i> ” by A. Alexandridis and N. J. Gardner (August, 1992, Vol. 118, No. 8)