| With the continuous upgrading of China's power grid system,transmission line is developing rapidly towards the trend of high voltage level,large capacity,compact and multi loop,which requires transmission towerhas a large size and high load capability.In order to make the iron tower meet the demand of load bearing andcomplete the functions,high-strength steel is adopted in the transmission tower.In the selection of component section,due to the section of steeltubepossesses those advantages such as symmetrical section,clear force-transfer and small wind-resistant area,the transmission tower with large span,large size and high load carrying capacity is being applied more and more.In our country,as the application of high strength steel tube in the transmission line is very late,high-strength steel tubes,which are Q420 and Q460,are now being used in transmission lines,but the application of higher-strength steeltube is not mature.Due to the lack of sufficient theoretical guidance and experience for high-strength steel Q690,it is necessary to carry out a lot of research work to make such high-strength steel tube be widely used in transmission line tower.Based on this,this paper carried out the research on application of Q690 high-strength steel tube in transmission line,including the overall stability of high-strength steel tube,local buckling,thetheory of tube-gusset joint of plane K type,experiment and numerical simulation.The above research in the domestic transmission industry is the first time.Firstly,the material test of Q690 high-strength steel was conducted to determine the basic mechanical properties of high-strength steel and the parameters of basic mechanical properties of high-strength steel.Based on this,experimental researchon the stability of axial compression of high-strength steeltube was conducted to analyze the integral stability and ultimate bearing capacity of axial compression of high-strength steeltube.The stable coefficient of axial compression of high-strength steeltube was calculated by “the unit length method of inverse calculation”.The influence of slenderness ratio,residual stressand other factorson the overall stability of high-strength steeltube was studied by changing parameter.The stability coefficient of high-strength steeltubeand the overall-stability formula were recommended.Secondly,the local stability bearing capacity test of Q690 high-strength steel tube under axial compression was carried out and the failure mode of specimen was observed.The local stability bearing capacity,change of load-displacement and the strain distribution of specimen were obtained.In considerationofthe influence of initial geometric imperfections and residual stresses,numerical simulation and analysis of the local stability bearing capacity was conducted.The important factors of influencing local stability and bearing capacity were determined.The design and calculation method on local stability bearing capacity of pressure bar in domestic and international codes was analyzed and studied,and the rationality of the design method in each norm was analyzed.The comparison on test and numerical simulation provided a basis for the design of the axially compressed stability of high-strength steel and promoted the application of high-strength steel in China.In the end,the experimental research on tube-gusset jointof the steel tube tower was carried out.The failure mechanism and failure mode of K joint of high-strength steel Q690 was revealed.On the basis of test results,the four kinds of nodes were simulated using Ansys and the mechanical properties of high-strength steel joints were studied.The influencing parameters of the load carrying capacity of the joint were analyzed by the finite element method.The solving process of the carrying capacity of the joint was derived by using the energy method,and an analytical model for estimating the ultimate bearing capacity of such joints was obtained.The calculation method of the load bearing capacity of tube-gusset joint of plane K typeof Q690 high-strength steelunder tension-compression loadwas obtained. |
PDF Full Text Request