Study On Mechanical Behavior And Design Method Of Double Angle T-shaped Composite Section Press-bending Member

Due to the generally low design standards of transmission towers built in the 1970s and1980s,as well as the increasing occurrence of extreme weather phenomena in recent years and frequent natural disasters such as rain,snow,frost,wind and so on,many tower collapse accidents have occurred in recent years.Most of these old towers have not met the requirements of the new standard(DL/T5154-2012).If the reconstruction of new transmission towers will consume huge manpower,material and financial resources,and will affect the stability of power supply at the same time.It is a better choice to continue to use these old and dangerous transmission towers after reinforcement.However,at present,most of the mainstream reinforcement methods are relatively complex,which can not meet the construction requirements of the tower under electrified operation.Therefore,scientific and reasonable reinforcement of the tower is an engineering problem to be solved urgently.In this regard,this paper mainly does the following research:(1)A new double angle steel T-shaped composite section reinforcement scheme is designed,and 10 full scale members are designed for experimental research.Mainly studies the slenderness ratio,number of fixture,bolt row number and fill in the plate spacing influence on bearing capacity and failure mode,and adopt technical code for the design of tower and pole structures of overhead transmission line(DL/T5154-2012)to predict the ultimate bearing capacity of test components,and introduce work coefficient k_d improved the calculation method to find the improved formula calculation precision is higher.(2)Based on the experimental study,the finite element numerical simulation is carried out,and the finite element simulation model is established.The accuracy and applicability of the finite element simulation model were verified by comparing the failure mode,load-displacement curve,load-strain curve and load-lateral horizontal displacement curve with the experimental phenomena and results.(3)This paper established the finite element simulation model adopted for double angle combination T-shaped composite press-bending component to the parametric analysis,mainly studies the slenderness ratio,bolt row number,the number of jig(fill plate spacing),bolt pre-tension force,reinforcement material strength,reinforcement material specification,fill plate thickness and end constraints,such as the influence of parameters on the mechanical performance of the strengthened member.(4)The ultimate bearing capacity of 106 press-bending members established by finite element parameterization analysis is theoretically analyzed and calculated.The calculation method of standard(DL/T5154-2012),the improved calculation method in this paper and BP neural network prediction algorithm are adopted respectively.The results show that both the improved calculation method and the BP neural network prediction algorithm have higher calculation accuracy,while the calculation results obtained by the standard(DL/T5154-2012)formula are conservative.