| With the continuous improvement of construction engineering technology and requirements,the safety requirements for tower cranes are becoming increasingly strict.As the tower crane is a high-rise structure,the top of the tower body moves laterally under normal use,and the P-(35)of second-order effect caused by vertical load is significant,which has a greater impact on the internal force and stability of the tower crane structure and its attachment devices.The P-(35)of second-order effect can be analyzed through finite element analysis,but the technical threshold is high,and it is also laborious and inconvenient for frontline engineering technicians to use.In response to this issue,this article proposes a simplified calculation method for tower body lateral displacement considering the P-(35)of second-order effect through on-site testing,finite element analysis,and theoretical means.The main research content is as follows:(1)The second-order effect of tower cranes needs to be considered.It is pointed out that the main second-order effect of tower cranes is the P-(35)of second-order effect,which is actually the gravity second-order effect of the tower body.The second-order effect of the tower arm is very small or even non-existent,and it does not need to be considered.The action of the upper structure can be equivalent to the force on the top of the tower body.(2)Based on the theoretical foundation of the second-order effect of tower cranes,a suitable second-order simplified analysis method is explored to address the issue of second-order lateral displacement of tower cranes,and a formula for calculating second-order lateral displacement is derived theoretically.Based on the structure and working characteristics of tower cranes,an equivalent method for the overall structure and load is proposed,and a simplified mechanical model is obtained.Based on the simplified mechanical model of the tower crane body,theoretical derivation was conducted using two methods: second-order analysis method and second-order approximate analysis method,and two second-order lateral displacement calculation formulas were preliminarily obtained.Select QTP125(ZTT6513)tower crane,compare and verify the results between the formula and finite element simulation,and obtain a reliable analysis method for the second-order effect of the tower crane and a calculation formula for the second-order lateral displacement.(3)In order to verify the rationality of the finite element simulation model,on-site testing was conducted on the QTP125(ZTT6513)and QTZ80(ST5513)tower cranes in engineering,and the finite element simulation model of the tower body was simplified and established to obtain the actual lateral displacement of the tower crane under different working conditions.Comparing the test data with the results of finite element analysis,data fitting confirmed the reliability of the finite element analysis results.(4)Based on the simulation finite element model,further parameterized analysis was conducted on the variable parameters of the tower body,exploring the relationship between each parameter and second-order effects.The specific parameters include the equivalent bending moment load,shear load,uniformly distributed wind load,upper structure gravity load,and tower height at the top of the tower.The finite element verification results indicate that in practical engineering,the formula parameters are still applicable after changes.(5)In practical engineering,considering that the variable factors of tower cranes have varying effects on their second-order effects,the influence of four main factors and the precautions for using formulas when factors change were studied.The specific factors to consider include the arrangement of the tower’s web members,the angle of tower arm rotation,the types of flat arm and movable arm,and the different height positions of the tower body.In engineering practice,the arrangement of the tower’s web members and the angle of tower arm rotation have little impact on the second-order lateral displacement of the tower body and can be ignored;Compared to flat arm tower cranes,when using formulas for boom tower cranes,attention should be paid to changes in equivalent loads;The second-order lateral displacement at different heights of the tower body can be calculated using formulas based on the equivalent isolation body. |
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