摘要:
研究建筑施工扣件式钢管满堂支撑架立杆长度的计算方法。现行规范中的计算长度系数线性插入方法为:按照T/CECS 699—2020《建筑施工扣件式钢管脚手架安全技术标准》中附录D,满堂支撑架的步距h或立杆伸出顶层水平杆中心线至支撑点的长度a以固定的步距递增,以立杆段初始计算长度LC为自变量,先通过线性插入方法计算出相应的满堂支撑架立杆计算长度系数(μ1或μ2),进而再计算出相应的立杆段力学计算长度LL。新提出的计算长度直接线性插入方法为:按照T/CECS 699—2020附录D中给出的特定参数(步距h、立杆间距、立杆伸出顶层水平杆中心线至支撑点的长度a)下的立杆计算长度系数(基于理论和试验结果得到的μ1或μ2),先计算出特定参数下的LL,h或a(或h+2a),再以固定的步距递增,以LC(h+2a或h)为自变量,通过线性插入方法再计算出相应的LL。通过对以上两种插入方法的LL和LC(a或h+2a、h)的散点图和拟合函数的分析,发现现行规范中的计算长度系数线性插入方法的计算结果违背了线性插入的基本原则(插入的因变量超出了被插入因变量的范围)。进一步的分析表明:T/CECS 699—2020附录D中的LC、LL按线性函数拟合具有足够的精度,完全可以将二者视为线性关系;满堂支撑架立杆的计算长度L0、长细比λ、稳定系数φ、稳定承载力均呈线性关系;现行规范中,将实际上为下凹的LC-μ二次项或幂的函数错误地视为线性函数,是导致产生LL(或承载力)违背线性插入基本原则的原因。结合有关文献中针对稳定承载力的实测和有限元分析的结果,参考现行的英国标准BS 5975∶2019中的计算方法,提出了以LC(h+2a或h)为自变量,直接线性插入扣件式钢管满堂支撑架立杆计算长度的方法。
Abstract:
This paper studied the method of calculating the length of the vertical rods of steel pipe fully-supported frames with fasteners in construction. The linear interpolation method for calculating the length coefficient in the current specification:according to Appendix D of Technical Standard for Safety of Steel Tubular Scaffold with Couplers in Construction (T/CECS 699—2020), the step length h of the fully-supported frame or the length a of the vertical rod extending from the center line of the top horizontal rod to the support point increased with a fixed step length, and the initial calculated lengthLC of the vertical pole section was taken as an independent variable, firstly, the calculated length coefficient (μ1 or μ2) of the vertical bar of the fully-supported frame was calculated by linear insertion method, and then the calculated lengthLL of the corresponding vertical rod segment was calculated. The newly proposed direct linear interpolation method for calculating length was as follows:the length coefficient (μ1 or μ2 based on theoretical and experimental results) was calculated according to the specific parameters given in Appendix D of T/CECS 699—2020 (step distance h, distance between vertical poles, length a from the center line of the vertical rod extending out of the top horizontal rod to the support point), firstly, the mechanical calculation lengthLL of the vertical rod section under specific parameters was calculated, and then the step distance h of the fully-supported frame or the length a (or h+2a) of the vertical pole extending from the center line of the top horizontal rod to the support point was increased by a fixed step, and the initial calculated length LC (h+2a orh) of the vertical rod section was taken as the independent variable, then, the corresponding mechanical length LL of the vertical rod segment was calculated by linear insertion method. By analyzing the scatter plots and fitting functions of the mechanical calculation length LL of the vertical rod segment and the initial calculation length LC(a or h+2a, h) of the above two insertion methods, it was found that the calculation results of the linear interpolation method of the calculation length coefficient in the current specification violated the basic principle of linear interpolation (the interpolated dependent variable exceeded the scope of the interpolated dependent variable). Further analysis showed: the initial calculation lengthLC and mechanical calculation length LL in Appendix D of T/CECS 699—2020 were fitted according to linear function with sufficient accuracy, and could be regarded as linear relations; the calculated length L0, the slenderness ratio λ, the stability coefficient φ and the stability bearing capacity were all linear; in the current specification, the function which was actually a concave LC-μ quadratic term or power was wrongly regarded as a linear function, which led to the reason that the calculated lengthLL (or bearing capacity) of the vertical rod segment violated the basic principle of linear interpolation. Based on the measured results and finite element analysis of the stable bearing capacity in relevant literatures, and referring to the calculation method in the current British standard BS 5975[DK]∶2019, a method of directly calculating the length of the vertical rod with linear insert fasteners was proposed, taking the initial calculation length LC (h+2a orh) as the independent variable.
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