线性弯矩分布下的搭接钢筋应力计算方法试验研究

Experimental Study on Calculation Method of Rebar Stress for Lap-splices Under Linear Moment Distribution

搭接连接是钢筋混凝土结构中一种常见的钢筋连接方式,目前规范中钢筋搭接长度或锚固长度的计算公式为基于大量搭接梁试验结果的半理论半经验公式,试验中搭接钢筋处于梁的纯弯曲段。然而在实际工程中构件普遍同时承受弯矩和剪力作用,线性弯矩分布减小了钢筋搭接长度范围内受到的拉力,从而降低了搭接钢筋的粘结要求,因此现有规范公式无法反映搭接钢筋的真实受力情况,计算得到的搭接钢筋应力结果普遍偏低。提出了一种线性弯矩分布下搭接钢筋应力的修正系数,并进行了8根钢筋搭接简支梁的静载试验,通过三点加载或四点加载的方式对比了搭接钢筋在不同弯矩分布下的搭接性能,并以GB 50010-2010和ACI 318-19的计算公式为例,对修正后的公式进行了验证,结果表明修正后的计算公式具有更好的预测精度,为实际构件的搭接钢筋应力计算提供参考。

In reinforced concrete structures,lap-splice is used for continuity of reinforcing bars.Current design codes specify the bar development length or splice length as the semi-theoretical and empirical equations based on large number of beam lap-splice test results.In the lap-splice tests,lapped bars are affected by flexural moment only.However,structural members are generally subjected to bending moment and shear force simultaneously.The linear moment distribution reduces the tension force of the lapped bars,which decreases the bond requirement.Therefore,the equations in current codes cannot response to the actual force condition of the lapped bars.In this paper,a modification factor of rebar stress of lap-spliced bars under linear moment distribution was proposed.Lap-splice tests were performed on eight reinforced concrete beams under 4-point loading and 3-point loading in order to investigate the moment distribution effect on the rebar stress.A modification factor for current design methods including GB 50010-2010 and ACI 318-19 was proposed for actual bond conditions.The results showed that the proposed method was reasonable to evaluate the rebar stress of the lap-spliced bars,the proposed method provides guidance for the lap-spliced bar stress calculation of existing structural components.