带接头在役混凝土电杆受力性能试验研究

为了揭示在役混凝土电杆连接接头的破坏机理和承载性能,进行了6根两类不同杆长、跨中带钢圈接头的混凝土电杆的抗弯承载力试验,通过试验观察了各试件的受力全过程和破坏形态,获取了弯矩-挠度曲线、裂缝宽度-弯矩曲线、刚度退化规律曲线以及极限弯矩等重要指标.对比分析了两种杆长试件的承载力和刚度变化规律,并通过试验拟合,提出了相关刚度退化规律公式.研究结果表明,试件所具有的破坏形态大多为混凝土拉裂、接头钢圈不屈服,破坏具有明显的脆性；截面的平均应变符合平截面假定；杆长较短试件的极限承载力显著大于较长杆长的试件；裂缝宽度-弯矩曲线大致经历了4个阶段:即未开裂阶段、逐渐增长阶段、稳定发展阶段、快速开裂阶段；杆长较短试件的初始弹性刚度以及弹塑性刚度都比较长杆长试件的大；电杆连接接头的相对刚域范围对杆身受力性能具有极大的影响.

Experimental Study of Mechanical Properties of Existing Reinforced Concrete Poles with Connection Joint

In order to reveal the failure mechanism and bearing capacity of existing reinforced concrete poles (RCP), flexural capacity experiment for two kinds of reinforced concrete pole with different rod length (6 poles altogether) and with steel ring joints at midspan were carried out. Through experiment, the whole process of forcing and failure pattern of specimens was observed, and a series of important indexes such as the bending moment-deflection curve, the crack width-bending moment curve, the stiffness degradation curve and the ultimate bending moment were obtained. The related stiffness degradation formula was put forward by comparing, the bearing capacity and the stiffness of two kinds of poles and experimental fitting. Results show that majority of specimen failure patterns is concrete creaking without steel ring joint yield, and their failures are obviously brittle. The mean strains of specimen cross-sections meet the plane-section assumption. The ultimate bearing load of short rod length specimen is larger than that of longer length specimen. Crack width-bending moment curve broadly experiences four stages: uncracked stage, gradual increase stage after cracking, stable development stage and rapid cracking stage. The initial elastic stiffness and elasto-plastic stiffness of short specimens are larger than those of long specimens. The range of relative rigid zone at the shorter pole are larger than that of longer pole. The relative stiffness domain of pole joint has great influence on mechanical properties of pole.