| With the rapid development of power grid in china,the application of transmission towers using high-strength steel has become an inevitable trend,and the importance of structural safety is also becoming increasingly apparent.Because of acid rain and wind force,the transmission tower is in the alternate environment of fatigue and corrosion fatigue when working.However,in the current transmission tower structure design,people take insufficient account of the natural environment,and only focuses on the strength and safety during construction,this is one of the important factors of transmission tower collapse.Meanwhile,the transmission tower nodes are numerous and they are vital to the structural safety,but the study on steel joints mostly focuses on the fields of Marine engineering and aircraft parts structure,etc while the research on transmission tower nodes is basically vacant.From the above,it is necessary to study on the damage reliability analysis of the transmission tower based on the corrosion fatigue of joints.In this paper,the damage reliability analysis of the transmission tower based on the corrosion fatigue of joints are researched in three aspects by study on the experiments and reliability theory.The first is the corrosion fatigue experimental research of bolted nodes and welded nodes with the material of Q420 high-strength steel in the actual service environment of the transmission tower.And the second is the study on the method for reliability analysis.And the last is the study on the method of damage reliability analysis of the transmission tower based on the corrosion fatigue of joints through the sample using ANSYS numerical simulation.And the main research contents and conclusions are shown as follows:1)The S-N curves and P-S-N curves of bolted joints and welded joints are proposed under the condition of the alternation of fatigue and corrosion fatigue.2)The stress level has a great influence on the failure mode of joint specimens.The failure of the specimens is brittle failure overall,but the fracture of the specimens is divided into two parts-one is the smooth part of crack propagation,and the other is the serrated part with the local plastic failure characteristic.The smaller the stress level is,the larger the integral part caused by crack growth is,the smaller the serrated part is,the less obvious the local plastic failure characteristics is,and the more obvious the brittle failure of the specimens is.3)The corrosion environment affects the fatigue life of the specimen.With the decrease of stress level,the impact of pure corrosion environment on the reduction of fatigue life is more significant than that of intermittent corrosion environment.4)The corrosion fatigue performance of bolt joints is better than that of welded joints.Since the fastening force of the bolt connection will increase the corrosion fatigue life of the joint while the welded joints will produce defects in the heat affected zone of the welded steel during the processing.Considering processing convenience,economy and safety practicality,this paper suggests bolt connection for transmission tower using angle steel.5)A new rational hybrid high dimensional model representation is proposed in this paper,and the point estimation method & moment method of reliability analysis are developed based on the proposed rational hybrid high dimensional model representation.At last,the rationality and applicability are verified by numerical examples and engineering examples.6)A damage reliability analysis method based on the nodal corrosion fatigue failure as the damage criterion of transmission tower is proposed in this paper.And the feasibility of the method is verified by a numerical simulation example. |
PDF Full Text Request