集成竹拉伸蠕变性能加速试验

刘燕燕; 盛宝璐; 黄东升; 王文蹈; 张锟

doi:10.13801/j.cnki.fhclxb.20230625.003

集成竹拉伸蠕变性能加速试验

doi: 10.13801/j.cnki.fhclxb.20230625.003

刘燕燕¹,
盛宝璐²,
黄东升^1, ,,
王文蹈^{1, 3},
张锟^{1, 3}

1.
南京林业大学　国家工程中心，南京 210037
2.
金陵科技学院　建筑工程学院，南京 211169
3.
南京林业大学　土木工程学院，南京 210037

基金项目: 国家自然科学基金(52008212；51978338)

详细信息

通讯作者:
黄东升，工学博士，教授，博士生导师，研究方向为现代竹/木结构　E-mail：dshuang@njfu.edu.cn

中图分类号: TU366.3；TB332
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- 被引次数: 0
出版历程
- 收稿日期: 2023-04-21
- 修回日期: 2023-06-05
- 录用日期: 2023-06-10
- 网络出版日期: 2023-06-26
- 刊出日期: 2024-02-01

Accelerated creep testing of tensile properties of glued laminated bamboo

LIU Yanyan¹,
SHENG Baolu²,
HUANG Dongsheng^{1
, ,},
WANG Wendao^{1, 3},
ZHANG Kun^{1, 3}

1.
National Engineering Research Center of Biomaterials, Nanjing Forestry University, Nanjing 210037, China
2.
School of Architectural Engineering, Jinling Institute of Technology, Nanjing 211169, China
3.
School of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China

Funds: National Natural Science Foundation of China (52008212; 51978338)

摘要

摘要: 通过短期(500 h)拉伸蠕变试验，研究了不同应力水平下集成竹顺纹拉伸蠕变行为及变化规律，采用了Findley蠕变模型对蠕变曲线进行模拟；通过阶梯等温法加速蠕变试验，对集成竹顺纹拉伸长期蠕变行为进行了加速表征，构建了跨度50年的蠕变主曲线。结果表明：不同应力水平下，集成竹拉伸蠕变曲线具有初始蠕变和稳态蠕变两个阶段；集成竹拉伸蠕变行为符合线性黏弹性，在任意时刻，其蠕变变形基本与应力水平成正比；根据蠕变主曲线，在60%极限荷载下，集成竹约在104天发生蠕变断裂，呈现脆性破坏形态；Findley蠕变模型不仅能较好地模拟集成竹短期拉伸蠕变行为，其外推结果与加速蠕变试验所得主曲线吻合良好。基于上述试验结果与分析，建立了考虑材料蠕变效应的等时应力-应变曲线，进一步讨论了针对不同设计使用年限的集成竹弹性模量调整系数，并与GB/T 50005—2017《木结构设计标准》建议值进行了对比。
- 集成竹 /
- 拉伸蠕变 /
- 加速蠕变试验 /
- 蠕变曲线 /
- Findley蠕变模型
Abstract: The tensile creep behavior of glued laminated bamboo was experimentally studied by the conventional creep test with a time duration of 500 h. The Findley creep model was used to fit the creep curves. The accelerated test using the stepped isothermal method (SIM) was applied to characterize the long-term tensile behavior of glued laminated bamboo. The SIM master curves display the creep characteristics of several decades beyond the test duration. The results show that the tensile creep curve of glued laminated bamboo has two stages under different stress levels: The primary and the secondary creep stages. The tensile creep behavior of glued laminated bamboo conforms to linear viscoelasticity, and its creep deformation is proportional to the stress level at any time. When the stress level is high (reaching 60% of the ultimate strength), the glued laminated bamboo undergoes creep fracture, presenting a brittle failure mode. The Findley creep model can well fit the short-term tensile creep behavior of glued laminated bamboo, and its extrapolation agrees well with the SIM creep master curve. Based on the test results and analysis, the isochronous stress-strain curves were established. The coefficient of elastic modulus of laminated bamboo for different design service life was further discussed and compared with the recommended values in GB/T 50005—2017 standard for design of timber structures.
- glued laminated bamboo /
- tensile creep /
- accelerated creep testing /
- creep curve /
- Findley creep model

HTML全文

图 1 阶梯等温法(SIM)蠕变主曲线的构建

T—Temperature; t—Time

Figure 1. Construction of the stepped isothermal method (SIM) creep maser curves

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图 2 集成竹拉伸试样尺寸

R—Radius

Figure 2. Dimensions of glued laminated bamboo tensile specimen

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图 3 集成竹顺纹拉伸应力-应变曲线

Figure 3. Tensile stress-strain curves parallel to the grain of glued laminated bamboo

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图 4 蠕变试验装置

Figure 4. Creep test equipment

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图 5 不同应力水平下集成竹常规蠕变结果

Figure 5. Creep results of glued laminated bamboo under different stress levels

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图 6 不同应力水平下集成竹相对蠕变曲线

Figure 6. Relative creep curves of glued laminated bamboo under different stress levels

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图 7 不同应力水平下集成竹加速蠕变试验结果

Figure 7. Results of accelerated creep test of glued laminated bamboo under different stress levels

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图 8 温度应变修正

Figure 8. Thermal strain correction

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图 9 参考温度23℃下集成竹的蠕变主曲线

Figure 9. Creep master curves of glued laminated bamboo at the reference temperature of 23℃

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图 10 基于加速蠕变试验的集成竹等时应力-应变曲线

Figure 10. Isochronous stress-strain curves of glued laminated bamboo based on the accelerated creep test

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表 1 阶梯等温法(SIM)加速蠕变试验加载方案

Table 1. Loading scheme of the accelerated creep test using the stepped isothermal method (SIM)

Loading condition	Number of specimen	Stress level	Stepped temperature/℃
SIM-T0%	2	0%	23, 30, 37, 44, 51, 58, 65, 72, 79, 86
SIM-T30%	2	30%
SIM-T40%	2	40%
SIM-T50%	2	50%
SIM-T60%	2	60%
SIM-T70%	2	70%
Note: T—Tensile loading.

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表 2 Findley蠕变模型拟合参数

Table 2. Fitting parameters of Findley creep model

Stress level	$ {\varepsilon _0} $	$ a $	$ n $	$ {R^2} $
30%	$ 3.58 \times {10^{ - 3}} $	$ 6.01 \times {10^{ - 4}} $	0.09	0.74
40%	$ 4.39 \times {10^{ - 3}} $	$ 6.61 \times {10^{ - 4}} $	0.11	0.98
50%	$ 5.17 \times {10^{ - 3}} $	$ 6.53 \times {10^{ - 4}} $	0.09	0.95
60%	$ 6.46 \times {10^{ - 3}} $	$ 6.97 \times {10^{ - 4}} $	0.10	0.92
70%	$ 7.22 \times {10^{ - 3}} $	$ 7.25 \times {10^{ - 4}} $	0.11	0.96
Notes: $ {\varepsilon _0} $—Instantaneous elastic strain; $ a $ and $ n $—Parameters of Findley model; $ {R^2} $—Goodness of fit.

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表 3 不同设计使用年限集成竹弹性模量调整系数

Table 3. Coefficient of elastic modulus of glued laminated bamboo for different design service life

Design service life/year	GB/T 50005—2017^[36]	Test results
Design service life/year	GB/T 50005—2017^[36]	$ E $/MPa	$ {K_{\text{L}}} $
5	1.10	11460	1.09
25	1.05	10770	1.02
50	1.00	10520	1.00
Notes: $ E $—Elastic modulus considering creep effect, obtained from the isochronous stress-strain curves in Fig. 10; $ {K_{\text{L}}} $—Coefficient of elastic modulus.

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