Safety Analysis Of Old Transmission Tower Structure

As the safety pillar of power transmission system,any form of partial damage or overall collapse of transmission tower will lead to serious consequences.Especially the old transmission tower has the common characteristics of large base number,long service time and imperfect structural design theory.The base number of collapsed tower increases year by year,which has an important impact on national economy and people's life.Therefore,it is urgent to evaluate the safety of old towers and further improve their performance to prolong their service life.Based on the analysis of the performance of old transmission towers,this paper establishes the macro-model and multi-scale numerical calculation model of the structural analysis of transmission towers,carries out the research on the static and dynamic characteristics of the structure,systematically carries out the safety analysis of the transmission towers under unfavorable conditions,analyses the failure process of the structure,puts forward the structural reinforcement scheme and carries out the checking calculation.Mainly carries on the research from the following aspects.The research achieves the automated numerical simulation of tower for structural diagnosis and treatment and the safety analysis of tower structure.The APDL language is used to realize the rapid modeling of the same type of tower structure with different heights,which can be applied to the batch study of structural safety.The safety evaluation is carried out through the analysis of static and dynamic characteristics of the structure,and the results show that there are local structural loads in the tower members.The phenomenon of insufficient load leads to the failure of weak parts and the overall damage of the structure.The collapse of old poles and towers is usually caused by the failure of some key parts.This paper analyses the weak position of the tower body structure,establishes a local micro-model,fully considers the geometric location and material information of the local part of the structure,and through USERMAT interface based on FORTRAN language,completes the secondary development of ANSYS software elastic-plastic damage constitutive model and carries out the key bureau.The damage analysis of the meso-model determines the evolution process of the local failure of the tower structure.The results show that the damage of the material begins in the plastic zone on the outside of the angle steel and extends gradually.With the increase of the load,some elements fail and some components produce large bending and torsion deformation,which ultimately leads to local structural damage.In order to study the influence of the results of the local model analysis on the whole structure,a multi-scale model including both macro and micro damage models is established and the damage analysis of the whole structure is carried out.The local damage evolution process in the process of structural failure is obtained.The damage evolution analysis of the multi-scale model is realized by improving the USERMAT subroutine.In the multi-scale model,not only the whole structure can be analyzed,but also the key parts can be studied at the meso-level.Different connection modes are considered and the numerical models are compared.The results show that the connection modes have little influence on the overall stress state of the model,and the local bending and torsion deformation results in tower failure.Based on the safety analysis of the tower structure mentioned above,the reinforcement scheme of the transmission tower structure is put forward.The numerical model of the reinforced structure is established by using the life and death treatment technology of the element and the restart method.The feasibility of the reinforcement scheme is verified by comparing the numerical model before and after the reinforcement with the data of the real experiment.Combined with the above material subroutine,the damage analysis of the reinforced model is carried out,and the dynamic characteristics of the structure before and after reinforcement are further compared.The results show that the reinforcement scheme is very effective and has important engineering application value for the reconstruction of old poles and towers.