Large cooling towers in thermal power plants and nuclear power plants are likely to suffer from strong earthquakes during service periods.The resulting destructions of the cooling towers would endanger the power plant...Large cooling towers in thermal power plants and nuclear power plants are likely to suffer from strong earthquakes during service periods.The resulting destructions of the cooling towers would endanger the power plants and threaten the security of the related areas.It is important to use effective means to evaluate the safety status of the cooling towers and guide further precautions as well as retrofitting efforts.This paper is therefore focused on an elaborate numerical investigation to the earthquake-induced collapses of a large cooling tower structure.A complete numerical work for simulation of material failure,component fracture,structural buckling and system collapse is presented by integrating the stochastic damage constitutive model of concrete,refined structural element models,and some other key techniques.Numerical results indicate that the damage behavior and collapse mode of the cooling tower are affected notably by the randomness specification of ground motions.The collapse mechanisms of the cooling tower are studied from the energy absorption and dissipation points of view.An effective energy-based criterion is introduced to identify the collapse of the cooling tower under ground motion excitations.While distinct collapse modes are observed,the collapse criterion can predict well the damage and failure of the cooling tower.The proposed methodology is vital to better understanding the disastrous mechanisms and potential failure paths in optimal design of the cooling towers to ensure safety.展开更多
Wind energy is a clean and renewable energy for which technology has developed rapidly in recent years.Wind turbines are commonly supported on tubular steel towers.As the turbine size is growing and the towers are ris...Wind energy is a clean and renewable energy for which technology has developed rapidly in recent years.Wind turbines are commonly supported on tubular steel towers.As the turbine size is growing and the towers are rising in height,steel towers are required to be sufficiently strong and stiff,consequently leading to high construction costs.To tackle this problem,a new type of prestressed concrete tower was designed employing a novel tower concept having a regular octagon cross section with interior ribs on each side,which was optimized by comparing the natural frequency and stress difference under the same lateral load in different directions of the tower.The designed tower features a tapered profile that reduces the area subjected to wind;the tapered profile reduces the total weight,applied moment and the capital cost.An optimization method was developed employing ABAQUS software and a genetic algorithm.A target function was defined on the basis of the minimum cost of the concrete and prestressed tendon used,and constraints were applied by accounting for the stress,displacements and natural frequency of the tower.Employing the method,a 100 m prestressed concrete tower system for a 5 MW turbine was optimized and designed under wind and earthquake loads.The paper also reports a systematic design procedure incorporating the finite element method and the optimization method for the prestressed concrete wind-turbine towers.展开更多
基金support from the National Key Research and Development Project of China and the National Natural Science Foundation of China is gratefully appreciated.
文摘Large cooling towers in thermal power plants and nuclear power plants are likely to suffer from strong earthquakes during service periods.The resulting destructions of the cooling towers would endanger the power plants and threaten the security of the related areas.It is important to use effective means to evaluate the safety status of the cooling towers and guide further precautions as well as retrofitting efforts.This paper is therefore focused on an elaborate numerical investigation to the earthquake-induced collapses of a large cooling tower structure.A complete numerical work for simulation of material failure,component fracture,structural buckling and system collapse is presented by integrating the stochastic damage constitutive model of concrete,refined structural element models,and some other key techniques.Numerical results indicate that the damage behavior and collapse mode of the cooling tower are affected notably by the randomness specification of ground motions.The collapse mechanisms of the cooling tower are studied from the energy absorption and dissipation points of view.An effective energy-based criterion is introduced to identify the collapse of the cooling tower under ground motion excitations.While distinct collapse modes are observed,the collapse criterion can predict well the damage and failure of the cooling tower.The proposed methodology is vital to better understanding the disastrous mechanisms and potential failure paths in optimal design of the cooling towers to ensure safety.
文摘为探究爬模施工进程中索塔空间温度场和应力场分布,掌握塔柱线形特性,提出一种索塔爬模施工仿真分析方法.利用Fortran编程语言开发相应子程序,对结构施加复杂温度边界,实现不同节段混凝土水化放热、收缩徐变.利用Abaqus软件对索塔爬模施工过程进行分析.结果表明:施工过程中索塔空间温度分布不均匀,塔柱表里最大温差达25.9℃,向阳面与背阴面温差最大为9℃;考虑温度效应后,塔柱所受拉应力更大,且空间应力分布具有很强的时变性,索塔线形特征与变化规律也发生改变;施工塔顶累积竖向位移先增大后减小,在爬模第16节段达到最大值20.5 mm;施工过程塔顶累计顺桥向和横桥向位移更大,最大值分别为6.5和22.3 mm.
基金supported by the National Natural Science Foundation of China(Grant No.51078231)
文摘Wind energy is a clean and renewable energy for which technology has developed rapidly in recent years.Wind turbines are commonly supported on tubular steel towers.As the turbine size is growing and the towers are rising in height,steel towers are required to be sufficiently strong and stiff,consequently leading to high construction costs.To tackle this problem,a new type of prestressed concrete tower was designed employing a novel tower concept having a regular octagon cross section with interior ribs on each side,which was optimized by comparing the natural frequency and stress difference under the same lateral load in different directions of the tower.The designed tower features a tapered profile that reduces the area subjected to wind;the tapered profile reduces the total weight,applied moment and the capital cost.An optimization method was developed employing ABAQUS software and a genetic algorithm.A target function was defined on the basis of the minimum cost of the concrete and prestressed tendon used,and constraints were applied by accounting for the stress,displacements and natural frequency of the tower.Employing the method,a 100 m prestressed concrete tower system for a 5 MW turbine was optimized and designed under wind and earthquake loads.The paper also reports a systematic design procedure incorporating the finite element method and the optimization method for the prestressed concrete wind-turbine towers.
