摘要
近年来,我国电力事业高速发展,对特高压输电塔钢材强度的选用及结构设计方法提出了更高的要求。Q460高强角钢有很好的承载力,其应用于实际工程对提高输电铁塔的经济性、先进性有重要意义。
架空送电线路塔架的受压角钢中,除一部分主材近似轴心受压构件,其余大部分是偏心受压构件。国内外学者对两端偏心受压单角钢的研究较多,而对一端偏心受压高强角钢试验研究资料很少。目前,我国规范中尚无一端偏心连接的Q460高强角钢计算方法。一端偏心受压角钢构件力的作用线不通过截面形心,且端部约束条件难以确定,受力性能非常复杂,因此单压杆试验中采用何种支座形式难以确定,这成为人们对角钢压杆深入研究的困扰之一,也是国内外研究角钢压杆只考虑两端偏心的原因之一。
为了避免单角钢受压试验时人为的处理角钢边界条件,考察符合工程实际的边界约束情况,即一端偏心连接Q460高强角钢的破坏模式及极限承载力,本文进行了两个足尺子结构试验,将单根角钢构件设计在类似输电铁塔横担的平面三角形桁架中进行破坏性静力试验,并通过ANSYS建模进行有限元分析,与单压杆试验进行比较并结合其结果对规范提出修改建议,从而使一端偏心高强角钢研究工作更全面、可靠。
试验研究表明：小长细比一端偏心连接的高强角钢受压时主要发生局部屈曲,变形集中于连接肢的偏心端,大长细比角钢受压时主要发生整体弯扭屈曲。子结构中试验角钢的受力性能和承载力与一端中心另端偏心连接的受压单根试验基本相同,说明单压杆试验偏心端端板直接顶在压力机顶板上、轴心端采用球铰支座能够模拟角钢在实际结构中的端部约束条件。试件《输电铁塔设计导则》(ASCE10-1997)计算值与试验值吻合较好,ASCE10-1997可为高强角钢设计提供依据,鉴于其对大长细比构件的计算偏于保守,本文依据试验结果将ASCE10-1997中一端中心另端偏心连接的角钢有效长细比公式修正为：可为规范修订及设计提供参考。
In recent years,electric power projects of our country has developed quickly. It will call for higher requirements on steel intensity and structural design of electric transmission towers.High-strength (Q460) steel-angle members have the high load-carrying capacity,utilizing them in transmission towers is of great significance to increasing economical efficiency and advanced technology.
The bulk of the hot-rolled single-angle members in tower structures of overhead transmission line are eccentric compression. The researchs of angle struts eccentricity at both ends are more than that of angle struts eccentricity at one end. The action line of the force does not through centre of section of the angle struts eccentricity at one end,the end supporting conditions are difficult to judge,and mechanical properties are very complex,so,which bearing should be used in single-strut tests is difficult to determine. Domestic single-strut tests tend to use the ball bearing or knife-edge bearing at the present time. Whether these bearings are able to simulate the actual mechanical behavior and constraints is uncertain.
To analyze mechanical behavior and the ultimate bearing capacity of Q460 high-strength equal-leg angle steel struts with an eccentric load at one end under actual project boundary condition, the angles are placed in the substructures similar to the transmission tower cross arm and failure static test of two substructures are conducted,and finite elements modeling analysis was done at the same time. The results are compared with single-strut tests and some suggestions to improve the specifications will be offered in this paper in order to make researchs more comprehensive and reliable.
Experimental studies indicate that:Most single-angle with small slenderness were controlled by local buckling while it was under eccentric load at one end, deformation concentrated in the eccentric side of the connected leg, and the large members were controlled by flexural-torsional buckling. Mechanical behavior and bearing capacity of the angles in the substructures is the same as the single-strut's. Therefore, the ball bearing used in single-strut tests can almost imitate the actual end supporting conditions. The calculation basis on ASCE10-1997 agreed well with the experimental results, so it can provide a basis for design of high-strength angle, but it was over-conservative on large slenderness angles, according to the test results, the revised formulas of it were proposed:KA= 45+0.47λ,it is a reference for design.
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