| Transmission tower line system has the characteristics of high height,large span and strong flexibility.Because of the existing transmission line design technology in our country,of which the wind resistance design criterion about tower is low,under the attack of typhoon there are frequent transmission lines in the coastal areas where collapse of towers and broken poles have happened,which seriously affects economic development.The collapse of most towers is due to the overall instability of the structure which is often caused by the failure of local components including strength failure and stability failure.At present,the research on the structural stability of towers is not mature,especially the dynamic stability that involves geometric nonlinearity and material nonlinearity.So it has important significance to study elastoplastic instability damage of towers in the transmission tower line system under typhoon load.The equivalent static wind load was calculated according to Load Code for The Design of Building Structures(GB50009-2012)specified in the specification.At first,the influence of wind angle,the deformation of adjacent towers and the change of tension of conducting and grounding wires on the overall stability of towers was analyzed under equivalent static wind load,then the equivalent stress was calculated according to Mises yield criterion to analyze the local destruction of main levers of towers on different wind angle to identify the failure path and the weakest part.The results show that the tower is most easy to damage on 90° wind angle;the deformation of adjacent towers can accelerate the destruction of towers;the larger the tension of conducting and grounding wires is,the better stability of towers is;the weakest parts on 0°,45°,and 90° wind angles are all the 8th storey;the maximum stress of every main lever is mainly located on the end of the member which is connected with diagonal members and assistant members.The typhoon wind speed time history was simulated according to the typhoon parameters studied by Chinese scholars.The influence of wind angle,the deformation of adjacent towers and the change of tension of conducting and grounding wires on the overall stability of towers was analyzed under wind load time history,then the results of dynamic analysis were compared with that of the static analysis.The results shows that we can get the same law by dynamic analysis as the static analysis,but the equivalent static computation results are unsafer.The law of strain energy change of all members and the main levers of every storey of the tower of one tower and two-spans system under equivalent static wind load on different wind angle was analyzed to identify the damage degree of every storey and the main members which absorbed energy.The law of energy absorption of every tower of four towers and five-spans system under equivalent static wind load on different wind angle was analyzed to identify the weakest tower.The dynamic energy and strain energy time history of every storey of the tower of one tower and two-spans system were analyzed,and by analyzing the law when the dynamic energy and strain energy changed with the increasing of average wind speed to identify the damage degree of every storey.The results shows that the tower energy of every storey that transformed from the work of the external load is main absorbed by the main levers;over the time history the dynamic energy is far lower than the strain energy at the same average wind speed,thus the work of the external load mainly causes the structural deformation;the law of strain energy change of every storey under the dynamic load is the same as that under the equivalent static wind load,so the law of strain energy change of every storey can reflect the damage degree of the storey. |
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