Nonlinear Dynamic Analysis Of Tall Chimney Under Wind And Temperature

As a special structure in industrial construction,chimneys work at high temperatures all year round and their height is constantly increasing,making them a towering structure susceptible to wind load damage.In order to ensure the safety of towering chimneys in use,their non-linear dynamic response under the combined effect of wind loads and temperature stresses is investigated.In this paper,a 180 m high reinforced concrete chimney at a site in northwest China is used as the object of study to carry out a non-linear analysis of the wind vibration time response.The results of wind vibration acting alone are also compared with the non-linear results of the wind vibration force response under high temperature action.The main research contents and achievements of this paper are as follows.(1)According to the actual dimensions of the architectural drawings,the finite element model of the towering reinforced concrete chimney was established by ABAQUS software,the constitutive relationship between the steel bar and the concrete was clarified,and the appropriate element was selected in the finite element software library.Finally,the modal analysis of the chimney model was carried out and the frequencies of each order of the structure were obtained.(2)The thermal parameters and mechanical properties of steel and concrete at high temperature were determined.Subsequently,the heat conduction equation was established,and the finite element method was used to simulate the calculation method of the temperature field.The results of the overall temperature field of the chimney under the action of hightemperature flue gas and the heating curves of the inner and outer surfaces of the concrete layer were obtained.Good insulation of heat,so that the temperature of the cylinder wall gradually decreases from the inside to the outside.(3)The time history of fluctuating wind speed at different heights of the chimney was simulated by the AR linear filtering method based on time-domain analysis,and then superimposed with the average wind speed to obtain the total wind speed time history,and then the wind vibration coefficient of the structure was calculated.The wind speed was converted into the corresponding equivalent nodal wind load applied to the structure.Finally,the nonlinear dynamic analysis of the towering chimney was carried out,and the related wind vibration response data such as the horizontal displacement,horizontal velocity and horizontal acceleration of the chimney vertex were obtained.(4)Using the thermal-structural coupling method in three working conditions,the nonlinear wind vibration response of the towering chimney at high temperature was studied,and compared with the wind vibration response analysis of the chimney at room temperature.It is concluded that the displacement,velocity and acceleration of the top of the chimney increase significantly in the wind vibration response under high temperature compared with those at normal temperature,and show a further increasing trend with the increase of temperature.