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林业科学 ›› 2018, Vol. 54 ›› Issue (4): 100-112.doi: 10.11707/j.1001-7488.20180412

• 论文与研究报告 • 上一篇    下一篇

国产结构用规格材的抗拉强度设计值

钟永1,2, 武国芳1,2, 任海青1,2   

  1. 1. 中国林业科学研究院木材工业研究所 北京 100091;
    2. 中国林业科学研究院林业新技术研究所 北京 100091
  • 收稿日期:2017-04-27 修回日期:2017-07-05 出版日期:2018-04-25 发布日期:2018-05-28
  • 基金资助:
    "十二五"国家科技支撑计划(2015BAD14B0502);"十三五"国家重点研发计划(2017YFC0703501)。

Design Value of Tension Strength of Domestic Dimension Lumber for Structural Use

Zhong Yong1,2, Wu Guofang1,2, Ren Haiqing1,2   

  1. 1. Research Institute of Wood Industry, CAF Beijing 100091;
    2. Research Institute of Forestry New Technology, CAF Beijing 100091
  • Received:2017-04-27 Revised:2017-07-05 Online:2018-04-25 Published:2018-05-28

摘要: [目的]提出国产结构用规格材抗拉强度设计值确定方法,以指导国产结构用规格材在木结构中的安全设计和合理应用,为今后相关规范的制修订提供参考。[方法]以国产兴安落叶松规格材为例,总结不同材质等级(Ⅰc、Ⅱc、Ⅲc和Ⅳc)规格材的足尺抗拉试验数据;采用最小二乘法确定不同拟合数据点下规格材抗拉强度的概率分布参数值,并基于非参数法确定规格材的抗拉强度标准值;结合可靠度理论分析方法,分析规格材在不同拟合数据点、概率分布、荷载组合类型和荷载比值下可靠度指标与抗力分项系数之间的相互关系。[结果]不同材质等级规格材的抗拉强度存在显著差异,其平均值表现为Ⅰc > Ⅲc > Ⅳc > Ⅱc,变异系数则表现为Ⅱc < Ⅰc < Ⅲc < Ⅳc;通过拟合结果比较,随着拟合数据点减少,正态分布(Normal)、两参数威布尔分布(2-P-Weibull)和对数正态分布(Lognormal)拟合的尾部概率分布开始趋于一致,且与实测尾部概率分布基本相同;通过可靠度分析结果比较,规格材抗拉强度采用Lognormal分布得到的可靠度指标最大,采用Normal分布得到的可靠度指标最小;随着拟合数据点减少,3种概率分布(Normal、Lognormal和2-P-Weibull)得到的可靠度指标开始趋于一致;在抗力分项系数相同的情况下,对于恒荷载+住宅楼面活荷载(D+R)、恒荷载+办公室楼面活荷载(D+O)组合类型,其可靠度指标随荷载比值增大呈递增趋势,但对于恒荷载+雪活荷载(D+S)、恒荷载+风活荷载(D+W)组合类型,其可靠度指标随荷载比值的增大基本不变化;结合我国目标可靠度要求,D+WD+S荷载组合类型下的抗力分项系数最大,D+O荷载组合类型下的抗力分项系数最小。[结论]在确定国产结构用规格材的抗拉强度设计值时,建议其抗拉强度的概率分布选用对数正态分布模型且采用后25%的数据拟合点来确定模型参数值,荷载组合类型应选择恒荷载+住宅楼面活荷载且荷载比值为1.0。不同材质等级(Ⅰc、Ⅱc、Ⅲc和Ⅳc)国产兴安落叶松规格材抗拉强度设计值分别为9.0、6.8、5.6和2.9 MPa。

关键词: 国产规格材, 抗拉强度设计值, 木结构, 可靠度

Abstract: [Objective] For the safety design and the rational application of domestic dimension lumber in timber structure, the objective of this study was to develop a determination method of the design value of tension strength of domestic dimension lumber.[Method] The Chinese larch dimension lumber (Larix gmelinii) was selected as the research object. Full-size tensile test results of different visual grades (grade Ⅰc, Ⅱc, Ⅲc, Ⅳc) dimension lumber were summarized. By the least square method, the fitted parameters and results for tension strength were obtained under different probability distribution models and different fitting data points. The characteristic values of tension strength were also determined based on the nonparametric method. Finally, the relationships between the reliability index and the partial factor under different fitting data points, probability distribution models, load combinations, and load ratios were investigated by the reliability analysis theory.[Result] The results indicated that there were significant difference of tension strength between different visual grades. The average and the coefficient of variance of tension strength displayed the following order:Ⅰc > Ⅲc > Ⅳc > Ⅱc, Ⅱc < Ⅰc < Ⅲc < Ⅳc, respectively. Compared with the fitting results, the end probability distribution fitted by different models (Normal, Lognormal and 2-P-Weibull) begun to be identical with the decrease of the fitting data points, which was close to the tested values. The calculated reliability index with the lognormal probability distribution model was the highest, and that with the normal probability distribution model was the lowest. With the decrease of the fitting data points, the calculated reliability indexes with different probability distribution models (Normal, Lognormal and 2-P-Weibull) begun to be identical. If the partial factor was the same, with the increase of the load ratio, the calculated reliability indexes under dead load plus residential live load (D+R), or dead load plus office live load (D+O) were increased, however, the calculated reliability indexes under dead load plus snow live load (D+S), or dead load plus wind live load (D+W) changed very little. The partial factor for D+W or D+S was the highest while that for D+O was the lowest.[Conclusion] To determine the design value of tension strength of domestic dimension lumber, this study suggested that the lognormal probability distribution model be selected for the tested probability distribution of tension strength, the parameters of the selected lognormal probability distribution model be determined by the 25 per cent tested data points, the load type of dead load plus residential live load be selected, and the load ratio be 1.0. For Chinese larch dimension lumber, the design values of tension strength of grade Ⅰc, Ⅱc, Ⅲc, Ⅳc were 9.0, 6.8, 5.6 and 2.9 MPa, respectively.

Key words: domestic dimension lumber, design value of tension strength, timber structure, reliability

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