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The present article proposes a model of wind force coefficient for designing open-topped storage tanks in various arrangements; main focus is on oil storage tanks. In our previous paper, we discussed the design wind force coefficients for isolated tanks, based on wind tunnel experiments of wind pressure distributions and buckling as well as on a finite element analysis of buckling under static wind loading. In practice, however, more than two tanks are constructed in various arrangements in a site. In such cases, the wind force distribution and the resultant buckling behavior of tanks may be affected by the arrangement significantly. Therefore, the present article focuses on the grouping effect on the wind force distribution and the buckling behavior. First, the wind pressures are measured simultaneously at many points both on the external and internal surfaces of a rigid model for various arrangements of two to four tanks in a turbulent boundary layer. The effects of arrangement pattern and gap spacing of tanks on the pressure distributions are discussed. Then, the buckling of tanks under static wind loading for various arrangements is analyzed by using a non-linear finite element method. The results indicate that the distribution of positive wind force coefficient in the windward area affects the buckling behavior significantly. Finally, based on the results obtained, we propose a model of wind force coefficient on tanks in various arrangements by modifying the model for isolated tanks that we proposed in our previous paper. For evaluating the design wind loads a gust effect factor approach is employed. The wind load evaluation is based on the quasi-steady principle and therefore the resonant effect is not taken into account. [ABSTRACT FROM AUTHOR]

Different four-tower arrangements have a great impact on wind-induced response and stability performance of super-large cooling tower. However, a single indicator (eg., interference factor of overall wind load) cannot provide a comprehensive and objective evaluation of wind-resistance safety of cooling tower. Here five typical four-tower arrangements in engineering practice were experimented, namely, row, rectangular, rhombic, L-shape, and oblique L-shape arrangement. Wind tunnel tests for rigid body were performed to determine the wind loads distribution pattern on the surface of group tower under different four-tower arrangements. Finite element method was employed to analyze the internal force and deformation distributions under the design wind load of return period. The influence of different four-tower arrangements on wind load-induced response was discussed under different incoming wind angles. Then the local stability and overall buckling stability of the cooling tower were estimated, and the ultimate bearing capacities under different four-tower arrangements were compared considering geometric nonlinearity. Instead of using a uniform structural design standard for cooling towers group, the influence rule of different arrangements on wind-induced response and safety performance of the cooling tower group was summarized. [ABSTRACT FROM AUTHOR]

This study presented a failure investigation on a wind farm which is located on the southeast coast of Mainland China and was severely damaged by two super typhoons: i.e., Dujuan in 2003 and Usagi in 2013. Failure characteristics of the wind farm in terms of rotor blade damage, tubular tower collapse and wind turbine (WT) burn were examined from a forensic engineering perspective. A systematic procedure was proposed to quantitatively investigate structural failure by calculating the extreme wind loads and re-constructing structural models for composite blades and steel towers. It was found that both extreme winds and the stop positions of WTs were critical to turbine failure due to the change of wind direction during typhoon impact. The overstrain/overstress was identified as the plausible root cause for structural failure of WTs. In addition, the dramatic reduction of shell wall thickness due to possible design defect was also found to be responsible for the tower collapse in this study. [ABSTRACT FROM AUTHOR]

Strong wind is one kind of the most destructive natural disasters devastating transmission towers. The damage and even collapse of transmission towers caused by strong winds occur frequently. Wind-induced fragility assessment of the transmission tower is of great significance for the safety and economy of transmission tower. It provides not only a basis for the disaster mitigation and risk assessment of the government, but the reference for the design, maintenance and retrofit of the transmission tower as well. In this paper, wind-induced fragility analysis and failure probability evaluation of the transmission tower with considering wind directionality are addressed. Firstly, the wind-induced fragility analysis method including two variants are presented. Then an engineering case is used to illustrate the fragility analysis of the transmission tower: the random finite element model of the transmission tower and the fluctuating wind speed and related wind load are simulated; the static non-linear buckling analysis under different wind attack angles is conducted to determine the threshold displacements in damage and collapse state of the tower; the incremental dynamic analysis is carried out to obtain the maximum displacement at the tower top and the fragility curve of the transmission tower is determined accordingly. Furthermore, the failure probability of the tower is determined considering wind directionality. Finally, the procedure to determine the optimal layout of the transmission tower is proposed, which is based on the overall damage and collapse probability of transmission tower under any layout in one year. The results show that the most unfavorable wind attack angle is 45°, then 0°, 60° and 90°, and the most favorable layout is 90° in damage and collapse state for the illustrated tower. • The wind-induced fragility analysis method including two variants are addressed and compared. • An approach to calculate the damage and collapse probability of the tower considering the wind directionality is proposed. • Given the wind speed statistical information, the layout optimization of the tower is analyzed. [ABSTRACT FROM AUTHOR]

Wind-induced internal forces in cladding support components of a long-span roof structure depend on local behaviors caused by local wind loads and wind-induced overall behaviors of the main structural frame. Based on the pioneering work of Ding and Tamura (2013) ; Ding et al. (2012) , a new method is proposed to estimate internal forces in cladding support components due to wind-induced overall behaviors directly. A detailed investigation on the contributions of wind-induced overall and local behaviors for internal forces in cladding support components of a space truss structure is performed. The results demonstrate that the bending moments and shear forces in cladding support components are dominated by local wind loads acting on the corresponding tributary areas, and the axial forces are caused by the overall displacements of the main structural frame. Considering only the local behavior will underestimate the axial forces in cladding support components significantly, which may lead to buckling failure. [ABSTRACT FROM AUTHOR]

Abstract The failure mechanisms of lattice transmission towers under the extreme wind conditions of typhoons are not well known and such knowledge is important for the improvement of overhead transmission line (OHL) design and to ensure the safe operation of transmission lines in typhoon-prone areas. This paper presents a case study on failure analysis of 13 collapsed lattice transmission towers in a110 kV transmission line during the super typhoon Rammasun that occurred in July 2014 in Hainan Province of China. A systematic computational procedure was developed to conduct the failure analysis with particular focus on modeling the fluctuating turbulent wind loads combined with the heavy rain loads. The results show that the failure mode and location obtained from the dynamic analysis are in good agreement with the post-event field observations. The collapse of the suspension lattice transmission towers was triggered by the buckling of the main leg members in the third panel from the ground level due to the extreme high axial stresses. Key design suggestions like improving the design wind speed and adopting an equal-strength beam approach are proposed to reduce the risk of lattice transmission tower failure and ensure continued serviceability and safe operations under the typhoon-wind conditions. Highlights • A systematic computational procedure to study the failure of lattice transmission towers damaged by typhoon is developed. • Tower collapse found in post-event observation is validated through failure analysis. • Fluctuating wind and rain loads have critical contribution to the failure of towers. • Overstress of the leg members in the third panel is the plausible root cause. [ABSTRACT FROM AUTHOR]

An aeroelastic model design method of a complicated steel truss arch tower was proposed and the response features subjected to skew incident wind forces were presented via experimental approach. At the geometric scaling of 1:40, the bars of aeroelastic model were designed and manufactured with scaled appearance, of which the rigidities are scaled based on the classification grouping to the dimensions and weights are compensated. The buckling analysis and checking calculation of members' slenderness ratio were carried out. Wind tunnel tests on the completed stage and two key construction stages were conducted with various skew incident angles. Otherwise, the sensitivity coefficient of the y directional extreme displacement for the completed tower in turbulent flow was analyzed. The results show that the wind load in y direction has much more effect on the structure and the wind induced responses meet the design requirements. The maximum y directional extreme displacement at the reference wind speed appears within the range of wind incident angles 0°~30°. The decrease trend of the y directional extreme displacement of the completed tower in turbulent flow in the wind incident angle range of 30°~80° is bigger than that in other angles. • The aeroelastic model design method of a complicated steel truss arch tower with multi-end constraints has been proposed. • The buckling analysis and checking calculation of members' slenderness ratio for the model have been carried out. • The complicated aeroelastic model has been manufactured and validated. • The dimensionless sensitivity coefficient has been used to analyze the response sensitivity of the model to skew wind. [ABSTRACT FROM AUTHOR]

Many tower structures have collapsed during strong wind events; therefore, the objective of the present study is to estimate the strength capacity of transmission towers accurately and to identify all potential failure modes. An uncertainty analysis method for tower structures subjected to a wind load is presented. Subsequently, random samples of material properties and section dimensions are generated based on the Latin Hypercube Sampling technique and then used to establish uncertain finite element models for transmission towers. A static non-linear buckling analysis for structures subjected to a wind load is conducted using ANSYS software. Based on tower models incorporating uncertainty, our analysis reveals that there are six possible initial failure tower members but only one for the deterministic model, indicating that the uncertainties regarding material properties and section dimensions should be taken into account. Furthermore, a sensitivity analysis is conducted, and the results reveal that the uncertainty of material properties has a stronger influence than the uncertainty of section dimensions. Finally, the influence of wind attack angle is discussed, and the initial failure positions and corresponding probabilities for various wind attack angles are obtained. The results show that the most unfavorable wind attack angle is 0° and that the most probable failure position of the tower of interest is the middle of the tower body. [ABSTRACT FROM AUTHOR]

Many wind-induced collapse events of super-large cooling tower have been taken place in history. Existing norms are limited within local excessive strength or buckling failure of the tower body, but ignore the follow-up phenomena after the general continuous collapse caused by local damages. Hence, they are difficult to disclose the wind-induced collapse mechanism and failure mechanism of super-large cooling tower. A case study on the world highest (228 m) cooling tower under construction in Northwest China was carried out. Variations of multi-scale wall thickness and reinforcement ratio at different positions of the tower body were considered by the layered shell element modeling method. The wind loads on the cooling tower surface were acquired through a wind tunnel test of pressure measurement on the rigid body. Displacement and internal force responses of the tower body under typical wind speeds were analyzed by combining the incremental dynamic analysis (IDA), thus determining the critical wind speed. Three redistribution of internal forces mechanisms during collapse of tower body were extracted based on the stress variation indexes before and after the node failure. Moreover, the development paths of three collapse mechanisms among units with different thicknesses of the tower body were discussed. Finally, the wind-induced failure criteria of super-large cooling tower structure were proposed based on throat deformation of the tower body. Research results demonstrated that the layered shell element model could simulate the full process of collapse of super-large cooling tower effectively and a central damage area from the throat of windward side to the center of tower body was formed. Subsequently, a crack network was formed after diffusion of the damage area along the circumferential and meridian until the complete collapse. Three redistribution mechanisms of internal forces during the collapse of the super-large cooling tower were proposed, including the sliding surface mechanism, rotating hinge mechanism and slipping surface mechanism. The super-large cooling tower structure developed wind-induced failure and collapse when the deformation failure index is δ ≥ 1.5%. It is of great significance to the design and construction of super-large cooling towers. • High precision of super-large cooling tower based on layered shell element model. • Progressive collapse of super-large cooling tower due to failure of throat when wind speed is 83 m/s. • Redistributed of internal forces by observing the three redistribution mechanisms in collapse process of super-large cooling tower. • The super-large cooling tower collapses after deformation failure criterion index δ ≥ 1.5%. [ABSTRACT FROM AUTHOR]

Abstract: When crest-fixed thin trapezoidal steel cladding with closely spaced ribs is subjected to wind uplift/suction forces, local dimpling or pull-through failures occur prematurely at their screw connections because of the large stress concentrations in the cladding under the screw heads. Currently, the design of crest-fixed profiled steel cladding is mainly based on time consuming and expensive laboratory tests due to the lack of adequate design rules. In this research, a shell finite element model of crest-fixed trapezoidal steel cladding with closely spaced ribs was developed and validated using experimental results. The finite element model included a recently developed splitting criterion and other advanced features including geometric imperfections, buckling effects, contact modelling and hyperelastic behaviour of neoprene washers, and was used in a detailed parametric study to develop suitable design formulae for local failures. This paper presents the details of the finite element analyses, large scale experiments and their results including the new wind uplift design strength formulae for trapezoidal steel cladding with closely spaced ribs. The new design formulae can be used to achieve both safe and optimised solutions. [Copyright &y& Elsevier]

Following such landmark aerodynamic tests as Irminger''s in 1894, Flachsbart''s in 1932—the first to be conducted in boundary-layer flow—and University of Western Ontario (UWO) 1970s tests, considerable progress has been achieved in low-rise building design for wind. Nevertheless, the present state of the art remains inadequate. UWO tests were conducted at low angular and spatial resolutions. Their results were then used to create drastically simplifying standard aerodynamic tables and plots designed for slide-rule era calculations and entailing errors that can exceed 50%.We review material which shows that significant improvements in main wind-load resisting system and component design can be achieved by using database-assisted design (DAD) and associated structural reliability tools, thus accounting realistically for the complexity of the wind loading as well as for the stochasticity and knowledge uncertainties affecting wind effects calculations. We illustrate DAD''s capability to obtain, for the first time in a wind engineering context, realistic estimates of ultimate limit states due to local or global buckling failure. In the future other types of nonlinear behavior associated with ultimate limit states can be similarly dealt with. We note that DAD is ideally suited for use with data likely to be obtained in the future by Computational Fluid Dynamics methods. We discuss the need for assuring quality control procedures for wind tunnel testing so that inter-laboratory comparisons of test results and wind tunnel certifications can be conducted effectively. We also discuss the possibility of systematic database corrections based on full-scale test results, and the possibility of using tests in non-standard wind environments and/or on buildings with non-standard shapes. [Copyright &y& Elsevier]