2002 Fiscal Year Final Research Report Summary
Modeling of Onset of Spalling of Concrete during Fire by Pore Pressure Rise
| Project/Area Number |
12450235
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Architectural environment/equipment
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
HARADA Kazunori Graduate School of Engineering, Assoc. Prof., 工学研究科, 助教授 (90198911)
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| Co-Investigator(Kenkyū-buntansha) |
TAKADA Satoru Graduate School of Engineering, Instructor, 工学研究科, 助手 (20301244)
YAMAZAKI Masahiro Graduate School of Engineering, Lecturer, 工学研究科, 講師 (60240826)
HOKOI Shuichi Graduate School of Engineering, Professor, 工学研究科, 教授 (80111938)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Concrete / Spalling / Vapor Pressure / Thermal Stress / Heat and Mass Transfer / Stress Analysis |
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| Research Abstract |
This work is concerned with; 1) Sensitivity analysis of thermal stress and pore vapor pressure upon the onset of spalling of concrete during fire, 2) experimental analysis by using small scale specimens and 3) development of computer code for simultaneous transfer of heat, mass (water vapor) and stress within concrete material. 1) As to the sensitivity analysis, a simple two-dimensional model for heat and mass transfer program was developed. Simulations were carried out for cylinders heated by standard time- temperature curve. The resulting thermal stress was calculated under the assumption of plane strain. It was found that the thermal stress is increased as the strength of concrete is increased. Comparing with thermal stress and pore pressure, thermal stress is dominant in magnitude. The effect of pore pressure may have certain effect, however pore pressure alone cannot be a main cause of spalling. Following the findings of sensitivity analysis. 2) experiments were conducted for cylindrical specimens of three different strength (40, 110 and 150 MPa). Axial loading and non-uniformity of heating were selected as parameters to be examined. The results showed at least qualitatively that frequency and degree of spalling is increased as strength is increased, that non-uniform heating cause the degree of spalling considerably and that existence of axial compression and end-restraint changes the depth of spalling to shallow layer. By summarizing above, it was suggested to analyze stress and pore pressure in the early stage of heating in three- dimensional field. Thus the simple model used in sensitivity analysis was extended into three dimensional model. In addition, the effect of pore pressure was explicitly taken into account by using the concept of uplift coefficient. The analytical results showed that the effect of non-uniform heating may cause large thermal stress in the early stage of heating.
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Research Products
(10 results)
