各规范钢筋间接搭接设计方法对比研究

Comparative study on design methods for noncontact lap splice of rebars in different codes

归纳对比了国内外规范钢筋间接搭接连接的设计方法和构造要求,分析了各因素对搭接长度的影响。我国规范未明确给出钢筋间接搭接的概念,无法直接应用于装配式结构中钢筋间接搭接连接设计。我国规范仅给出了绑扎搭接区域横向钢筋的基本构造要求,但不考虑横向钢筋对搭接长度的影响,国外规范普遍建立了基于横向钢筋配筋量的搭接长度折减系数。各规范建议的末端带弯钩钢筋的受拉搭接长度约为直钢筋的0.50~0.90倍,我国规范规定带弯钩钢筋的受拉搭接长度较直钢筋折减0.60也在该范围内。各规范计算得到的受压搭接长度均小于受拉搭接长度,我国规范计算得到的受拉搭接长度普遍大于国外规范,建议修正我国规范中建议的纵向搭接钢筋接头面积百分率影响系数。参考国外规范,建议间接搭接连接的搭接钢筋横向净距s不应低于25mm、搭接钢筋直径d和4/3倍粗骨料名义最大尺寸的较大值,不应大于0.2ls-t-d(ls-t为受拉搭接长度)和150mm-d的较小值。s>4d时,搭接长度ls-t在计算搭接长度的基础上增加s。

The design methods and detailing requirments for noncontact lap splice of rebars in Chinese and foreign codes were summarized and compared.And effects of different factors on lap length were identified.Due to the lack of specification on noncontact lap splice,Chinese code can not be directly applied to the design of noncontact lap splice in precast structures.Chinese code stipulates basic detailing requirments for transverse rebars along the bundled rebar splice,ignoring the influence of transverse rebars on lap length,while foreign codes generally introduce reduction coefficients of lap length to consider the contribution of transverse rebars.The recommended lap length with standard hooks in tension is about 0.50~0.90 times that of straight rebars in foreign codes;the value of 0.60 times specified by Chinese code is also within this range.The calculated compression lap length by all codes is smaller than the tension lap length.Considering that the tension lap length in Chinese code is generally larger than that in foreign codes,it is recommended to modify the coefficient that incorporates the influence of the pencentage of rebars lapped in one section.Based on foreign codes,it is proposed that the transverse clear distance s between two lapped rebars should not be less than the maximum of 25 mm,the lapped rebar diameter d and 4/3 times of the nominal maximum size of coarse aggregate,while s should not exceed 0.2ls-t-d(ls-t denotes the tension lap length)and 150 mm-d;and ls-t should be increased by s if s is greater than 4d.