| In recent years,China’s prefabricated buildings have developed rapidly with the support of national and local policies,and the performance requirements and intelligentized level of corresponding construction equipment have also been continuously improved.However,the lifting of prefabricated building components is still dominated by tower cranes,and there is no construction integration platform suitable for prefabricated buildings in China.In order to promote the industrialization and intelligent development of prefabricated buildings in China,this paper takes a highly automated prefabricated building special lifting platform as the research object,and analyzes and evaluates the safety of the special lifting platform used in the construction of a prefabricated building.The main research contents are as follows:(1)the analysis of lifting process of prefabricated components,hoisting system with vertical component and horizontal component hoisting system of the relative position and hoisting load for the principle,determines the working state of four kinds of the most unfavorable conditions,has been clear about the non-working state when stop lifting system of parking position,lifting platform biggest jack-up height(100.6 m)finite element modal analysis showed that the lifting platform low natural frequency of vibration,the vertical component of hoisting system of lifting platform has the greatest effect in the vibration mode,vibration occurs mainly in the more than a device attached to the wall structure,the transverse dynamic stiffness is poorer.(2)Wind-induced response analysis of lifting platform in working state.Through the numerical simulation of the fluctuating wind speed time history of the hoisting platform,the finite element analysis of the fluctuating wind speed time history is carried out with the method of time domain analysis,and the wind vibration response law of the displacement,acceleration and stress of each part of the structure of the hoisting platform under the working state is compared and analyzed.The results show that the position of the vertical component hoisting system has a great influence on the wind vibration response of the platform,and the deformation of the platform is the largest when the crane trolley hoisting the prefabricated components moving downwind.The wind load has little influence on the deformation of the track of the component hoisting system,and the overall deformation of the structure and the track deformation are both within the control range.The extreme stress response point of the hoisting platform can be found at the connection between the top of the tower and the upper frame,and the maximum stress ratio is 0.721.The structure is safe under the working state of the hoisting platform.(3)Wind-induced response analysis of non-working hoisting platform subjected to typhoon extreme weather.Considering the increasing effect of dynamic wind load caused by typhoon high turbulence,the Karman wind speed power spectrum was used to simulate the time-history curves of three typhoons,namely 28.6m/s(level 11),32.7m/s(level 12)and37m/s(level 13),to study the dynamic response of the lifting platform under different wind speeds and directions under non-working conditions.The results show that the maximum deformation of the lifting platform occurs in the middle of the upper frame where the vertical components are parked.The most unfavorable wind direction is 0°,and the deformation increases linearly with the increase of wind speed.The maximum stress response of the hoisting platform at 90° wind direction was found at the connection between the top of the tower and the upper frame,as well as the main chord at the constraint of the upper wall device of the tower.The maximum stress ratios of the three wind speeds were 0.774,0.999 and 1.282,respectively.The maximum lifting height of the hoisting platform can ensure the safety of the structure under the typhoon 12 of class C site.(4)Dynamic response analysis of independent height change of hoisting platform.The results show that when the maximum independent height of the lifting platform increases from 10.48 m to 13.48 m,the lateral stiffness of the structure decreases,the maximum deformation of the structure in working state increases by 35.08%,and the peak value of the stress response changes little.The deformation and stress in working state are both within the allowable limit.The maximum deformation under non-working condition increases by 30.33%,and the extreme stress response under different wind speeds is all in the core bar of the lower frame beam temporary stabilizer.The maximum stress ratio of the structure with wind speed of 28.6m/s reaches 0.984,and the increase proportion is 27.13%.Therefore,the maximum independent height of the hoisting platform can ensure the structural safety in the class C site under the typhoon level 11.(5)Through the above analysis and tower crane accident analysis under strong winds,the safety of the whole structure of the lifting platform when the attachment failure of the tower column of the lifting platform is studied.The results show that the failure of the tenth attachment device has a great impact on the safety of the platform,which increases the maximum displacement of the platform by 24.02%.The maximum displacement of the failure side of the platform increases by 43.85%.The maximum stress of the structure increases from155.03 MPa to 190.69 MPa with an increase ratio of 23.01%,and the maximum stress ratio is0.989.When the attachment device of a tower column fails,the structural safety can be guaranteed under the category C site with 11 typhoon.(6)Through the comparative analysis of different working condition of the lifting platform under the typhoon load the wind vibration response of the law,put forward the following Suggestions: lifting platform independent height above the attached device the size of the largest effect on its security under the action of a typhoon,the typhoon prone areas construction,should increase attached device in the process of setting to reduce the lifting platform using the largest independent height;In order to improve the safety of the hoisting platform under typhoon load,the lower frame should be strengthened near the temporary connecting device and the main chord of the tower. |
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