输电铁塔中连续轴压杆计算长度系数的讨论

输电铁塔中的主杆通常是连续的轴压杆件,在设计中常用计算长度系数考虑结构对于构件的支撑作用,然而无论是DL/T 5154-2002《架空送电线路杆塔结构设计技术规程》还是ASCE10-1997《美国输电铁塔设计导则》,对于上下段压杆对于中部压杆端部约束的有利影响都未考虑,将其作为强度储备忽略其作用,使得设计偏于保守。通过简化的理论分析模型,按照弹性弯曲理论,推导出连续轴压杆的计算长度系数的计算公式,通过对计算长度系数的观察,连续轴压杆中部压杆的端部约束要强于两端铰接的单根构件,上下段压杆对于中部压杆有一定的支撑作用,且支撑作用随着上下段压杆与中段压杆长细比相对比值的增大而增强。

Investigation of the effective length factor in continuous axially-loaded members of electricity transmission tower

The continuous axially-loaded members are usually applied to the electricity transmission tower.During the design,we usually use the effective length factor to consider the supporting function of structure to the bar.However,neither the Technical Regulation of Design for Tower and Pole Structures of Overhead Transmission Line(DL/T 5154-2002) nor Design of Latticed Steel Transmission Structures(ANSI/ASCE 10-1997) gives the consideration to the good effect of end restraint from adjacent segment members to middle members,by only thinking it as the strength storage and makes the design more conservative.Through the simplified theoretical analyzing model,and according to elastic bending theory,we deduct a calculating formula to effective length factor of continuous axially-loaded members in this paper.Through the observation to effective length factor,we get some results such as the end restraint of middle axially-loaded strut should be stronger than the hinged connection of axially-loaded bar;a certain supporting effect can be got from the top and bottom struts to the middle part,and this supporting effect can be magnified with the enlarge of slenderness ratio from the top and bottom struts to the middle part.