混凝土高温动态劈拉行为细观数值分析

金浏; 郝慧敏; 张仁波; 杜修力

doi:10.11883/bzycj-2018-0401

混凝土高温动态劈拉行为细观数值分析

doi: 10.11883/bzycj-2018-0401

北京工业大学城市与工程安全减灾教育部重点实验室，北京 100124

基金项目: 国家自然科学基金（51822801）；国家重点研发项目(2018YFC1504302)

详细信息

作者简介:
金　浏（1985－　），男，博士，教授，kinglew2007@163.com

通讯作者:
杜修力（1962－　），男，博士，教授，duxiuli@bjut.edu.cn

中图分类号: O383；TU528.1
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- 被引次数: 0
出版历程
- 收稿日期: 2018-10-17
- 修回日期: 2019-01-25
- 刊出日期: 2020-05-01

Meso-scale simulations on dynamic splitting tensile behaviors of concrete at elevated temperatures

Key Laboratory of Urban Security and Disaster Engineering, Ministry of Education, Beijing University of Technology, Beijing 100124, China

摘要

摘要: 为研究高温作用下混凝土的动态劈裂拉伸破坏行为，考虑了力学性能的高温退化与应变率增强效应的联合作用，结合混凝土材料内部非均质性，建立了细观尺度数值分析模型与方法。将该数值方法分为两个步骤：首先对混凝土进行热传导行为模拟，进而将输出结果作为初始条件对混凝土动态劈裂拉伸行为进行细观模拟。在模拟结果与已有试验现象良好吻合的基础上，分析了高温下混凝土动态劈裂拉伸行为及其细观破坏机制，对比了不同应变率及加热温度下混凝土的劈裂拉伸应力-应变关系，揭示了混凝土应变率效应与温度退化效应的相互影响规律。研究结果表明：(1) 高温作用后，试件损伤区域较常温下更集中；(2) 名义应变率较大时，破坏过程急促，常温下骨料发生破坏，而经历高温后骨料基本没有破坏；(3) 由于混凝土试件细观结构的非均质性，其内部应力呈枣核状不连续分布；(4) 相比于应变率效应，混凝土劈裂拉伸强度受温度退化作用的影响更显著。
- 混凝土 /
- 高温 /
- 动态劈拉 /
- 应变率效应 /
- 细观尺度
Abstract: To study the dynamic splitting tensile fracture behaviors of concrete at elevated temperatures, the numerical meso-scale model and method are established by considering the coupling effects of the high temperature degradation and strain rate enhancement of the mechanical properties, and combining with the internal heterogeneities of concrete materials. The simulation method is divided into two steps: the heat conduction behavior is first simulated, then the output results areused as the initial conditions to simulate the dynamic splitting tensile behaviors of the concrete. Based on the good agreement between the numerical simulation results and the experimental phenomenon, the dynamic splitting tensile behaviors and meso-scale failure mechanism of the concrete at elevated temperature are analyzed, the splitting tensile stress-strain relations of the concrete at different strain rates and high temperatures are compared, and the interacting regulation between the temperature degradation and the strain rate effect of concrete is revealed. The results prove that: (1) after high temperature, the damage area in the concrete is more concentrated; (2) the destructed process becomes more rapid as the nominal strain rate is higher, the aggregation is destroyed at room temperature; (3) the internal stress appears date-shaped distributions due to the heterogeneities of the concrete microstructures; (4) the temperature degradation effects on the splitting tensile strength of the concrete is more dramatic comparing with the strain rate effects.
- concrete /
- high temperature /
- dynamic splitting tensile /
- strain rate effect /
- meso-scale

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图 1 混凝土细观力学模型及网格划分

Figure 1. Meso-scopic models of concrete specimens and meshing

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图 2 高温下混凝土力学性能退化

Figure 2. Mechanical property degradation of concrete at elevated temperature

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图 3 标准温升曲线

Figure 3. Standard temperature curve

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图 4 四面受火混凝土试件不同时刻温度场分布

Figure 4. Temperature field within concrete specimen subjected to four-side fire

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图 5 模拟的破坏模式与试验结果对比

Figure 5. Comparison of failure modes between the simulated and experimental results

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图 6 加热60 min后混凝土试件应变率为1 s⁻¹时的劈裂拉伸损伤过程

Figure 6. Damage process of the concrete specimen at the strain rate of 1 s⁻¹ exposured to fire for 60 minutes

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图 7 高温下不同应变率下峰值应力处混凝土试件等效塑性应变

Figure 7. Equivalent plastic strain of the concrete specimen at peak stress under different strain rates and elevated temperatures

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图 8 不同细观组分的损伤分布情况

Figure 8. Damage distribution in different microscopic components

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图 9 高温下不同应变率下峰值应力处混凝土试件竖直应力

Figure 9. Longitudinal stress in the concrete specimen at peak stress under different strain rates and elevated temperatures

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图 10 不同应变率下混凝土试件应力-应变关系

Figure 10. Stress-strain curves of the concrete specimen at different strain rates and elevated temperatures

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图 11 不同应变率下的温度损伤程度

Figure 11. Temperature damage factors at different strain rates

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图 12 不同温度下动态拉伸强度增大系数与应变率的关系

Figure 12. Relations of dynamic increase factors of tensile strength to strain rates at different elevated temperatures

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表 1 室温下混凝土各细观组分热工参数

Table 1. Thermal parameters for the meso-constituents of concrete at room temperature (20 °C)

细观组分	导热系数κ/ (W·m⁻¹∙K⁻¹)	比热容c/ (J·kg⁻¹∙K⁻¹)	密度ρ/ (kg·m⁻³)
骨料	3.15^[17]	798^[18]	2 750
界面	0.7	906	2 450
砂浆	1.9	813^[19]	2 750

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表 2 室温下混凝土各细观组分力学参数

Table 2. Mechanical parameters for the meso-constituents of concrete at room temperature (20 °C)

细观组分	压缩强度 f_c/MPa	拉伸强度 f_t/MPa	弹性模量 E /GPa	泊松比 υ
骨料	152.0^[23]	−	35^[23]	0.2
界面	32.5	3.25	30	0.2
砂浆	40.0	4.00	25	0.2

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表 3 不同应变率下的混凝土温度损伤残余因子

Table 3. Temperature damage residual factors of concrete at different strain rates and different heating times

应变率/s⁻¹	温度损伤残余因子
应变率/s⁻¹	0 min	15 min	30 min	60 min
1×10⁻⁶	1	0.410	0.262	0.242
1×10⁻⁴	1	0.401	0.263	0.238
1×10⁻²	1	0.397	0.262	0.235
1×10⁻¹	1	0.392	0.256	0.229
1×10⁰	1	0.376	0.249	0.228
1×10¹	1	0.372	0.244	0.221
1×10²	1	0.317	0.208	0.194

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表 4 高温时不同应变率下的混凝土动态拉伸强度增大系数

Table 4. Dynamic increase factors of tensile strength of concrete under different strain rates and different heating times

应变率/s⁻¹	δ_t					δ_c
应变率/s⁻¹	0 min	15 min	30 min	60 min	CEB规范^[16]	δ_c
1×10⁻⁶	1.000	1.000	1.000	1.000	1.000	1.000
1×10⁻⁴	1.113	1.087	1.118	1.095	1.086	1.017
1×10⁻²	1.249	1.207	1.250	1.214	1.180	1.085
1×10⁻¹	1.355	1.295	1.322	1.283	1.230	1.120
1×10⁰	1.544	1.416	1.470	1.455	1.282	1.157
1×10¹	1.836	1.667	1.709	1.674	1.337	1.195
1×10²	3.137	2.423	2.487	2.519	2.878	1.793

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