Analysis On Wind-Induced Dynamic Failure Process Of Reinforced Concrete Cooling Tower

The reinforced concrete hyperbolic cooling tower is a tall space thin-walled structure,and the wind load is its design control load.For a long time,the stability and wind vibration response of cooling tower under wind load have been paid attention by researchers at home and abroad,but there is little research on the failure process of the structure under wind load.Therefore,it is of great significance to clarify the static/dynamic failure process of RC cooling tower.To this end,this paper takes an RC cooling tower as an example,uses ABAQUS finite element software and adopts layered shell elements to simulate the tower.Firstly,the dynamic characteristics and windinduced response time history of the tower under elastic category are analyzed,the wind-induced dynamic characteristics of each response of the tower are analyzed;Based on the verification of the constitutive model,and further considering the material and geometric nonlinearity,the static/dynamic ultimate bearing capacity and failure process of the tower were analyzed.The specific work and conclusions are as follows:(1)The layered shell model of cooling tower is established by ABAQUS software.Firstly,the dynamic characteristics of the cooling tower are analyzed,and then the wind-induced response time history of the tower is calculated.And the distribution characteristics of peak factor g and gust response factor G of different response of the tower are analyzed.The results show that the g values of different positions and different responses fluctuate greatly along the circumferential direction,but most of them are distributed between 3.0 and 4.5,which is not convenient for direct calculation of G values.Because of the symmetry of the structure and the arbitrariness of the wind load direction,the most unfavorable internal force element of each height may appear in any circumferential position.Therefore,only the response of the most unfavorable element of each height can be used to calculate g,so that its two-dimensional distribution can be transformed into one-dimensional distribution only along the height,and the response G values obtained are distributed between 1.3 and 3.5.At the same time,according to the spectrum distribution of each response,the main contribution of each response of the tower is the background component,but the resonance component also has a certain contribution.And the order of the contribution of different vibration modes to different positions and different response resonance components is different.(2)In order to carry out the nonlinear calculation,the Mc Neice plate and Jain plate are verified numerically.Based on the reasonable verification of the constitutive model,the plastic damage model and the double broken line model are used to simulate the nonlinear constitutive model of concrete and steel respectively.The ultimate bearing capacity of the tower under static wind load is analyzed: gravity+standard static wind(G+λW),gravity+winter temperature+standard static wind(G+T+λW)and gravity+test static wind(G+λW’).The results show that: under G+λW condition,the cracking load and ultimate load are 1.38 and 2.26 respectively,and the failure of the cooling tower is due to the continuous cracking of concrete in the windward area of the tower and the yielding of meridian reinforcement.For G+T+λW condition,considering the winter temperature load,the bi-directional positive bending moment leads to the early cracking of the tower,so the cracking load is 1.08;but with the increasing of the wind load,the winter temperature effect decreases.Therefore,the ultimate failure of cooling tower is still controlled by wind load,and the ultimate load is 2.26.At the same time,the ultimate bearing capacity of cooling tower under G+λW’ condition is larger than that under G+λW condition,but the ductility is smaller.In addition,compared with the existing research,the structural cracking load obtained by the plastic damage model in this paper is consistent with the dispersion cracking model,but the ultimate load obtained by the former is larger than the latter,and the ductility is better.(3)On the basis of the above nonlinear analysis,the time history of fluctuating wind pressure at different wind speeds is applied to the tower,and the dynamic failure process of the cooling tower is analyzed by the IDA method.The results show that:V=45m/s is the cracking wind speed of the tower.When V<45m/s,the displacement response of the tower changes linearly with the wind pressure.When V>45m/s,the cracking unit proportion of the tower concrete increases linearly with the wind speed,and the cracking time of the tower is advanced with the increase of the wind speed,when V=55m/s,the meridian steel bars yield for the first time.Finally,when V=57m/s,the structure occurs because of material strength failure destruction.In addition,the proportion of damping energy consumption gradually decreases,the proportion of elastic strain energy gradually decreases,and the proportion of plastic energy consumption gradually increases during the failure process of the cooling tower;And with the increase of damage,the structural frequency decreases continuously,and the G value increases at different wind speeds,but the dynamic effect of the cooling tower in the damaged state is not prominent.