1999 Fiscal Year Final Research Report Summary
Dynamic Vibration Model for Ordinary Building Considering Ground Characteristics
| Project/Area Number |
09450201
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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 |
Building structures/materials
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KANDA Jun Graduate School of Frontier Sciences, The University of Tokyo, Professor, 大学院・新領域創成科学研究科, 教授 (80134477)
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| Co-Investigator(Kenkyū-buntansha) |
IWASAKI Ryoji Graduate School of Engineering, The University of Tokyo, Research Assoc., 大学院・工学系研究科, 助手 (60011160)
TAKADA Tsuyoshi Graduate School of Engineering, The University of Tokyo, Assoc.Professor, 大学院・工学系研究科, 助教授 (10302762)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Micro tremor / Soil-Structure Interaction / high rise buildings / low rise buildings / a fixed base model / an SR model / natural period / damping ratio |
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| Research Abstract |
To construct a dynamic vibration model taking account of ground soil, micro-tremor measurement of existing buildings has been made, and dynamic characteristics of the buildings was studied with the aid of a system identification technique with transfer functions.
For high rise buildings, measurement of twenty four existing steel buildings have been carried out. As the result, a fixed base-model is found to be sufficient enough as an appropriate dynamic model since the soil-structure interaction effect cannot be observed. Among the dynamic characteristics, the natural period arid a damping ratio were selected as important parameters and studied with several system identification techniques : a curve fitting method, a RD (Random Decrement) method and an ARX (Auto-Regressive model with eXogeneous input) method. With the RD method, the following relationships : TィイD21ィエD2=0.021H and hィイD21ィエD2=0.956/T1+0.566 are obtained, where TィイD21ィエD2 is a first natural period of a building and H is a b
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uilding height in meter, hィイD21ィエD2 is a first modal damping ratio. Consecutively, higher modal damping ratios were estimated as hィイD22ィエD2=0.873hィイD21ィエD2+0.301 and hィイD23ィエD2=0.440hィイD21ィエD2+O.993.
For the middle and low rise buildings, micro-tremor measurement of seven reinforced concrete buildings have been made. As the results, it is pointed out that an SR (Sway-Rocking) model is appropriate as an dynamic model since the soil-structure interaction effect is found to be significant. The first natural period of a building were estimated from measured transfer functions of an assumed fixed base model, then the first modal damping ratio, rocking stiffness of the ground and its damping ratio were estimated on the basis that the rocking stiffness takes the maximum value for the measured transfer function of an assumed SR model.
A new two-step system identification technique has been proposed fully utilizing a curve-fitting method in order to estimate some important vibration parameters of buildings as well as the soil-structure interaction effect. It is found that there is a tendency that TィイD2bィエD2 < TィイD2RィエD2 < TィイD2TィエD2 model and TィイD2TィエD2 : that of an SR model. Since the sway mode is more prominent in the low rise buildings than the rocking mode is, the degree of lengthening from Tb to TィイD2RィエD2 is much more significant than that from TィイD2RィエD2 to TィイD2TィエD2.
The damping ratio of the SR model is much larger than that of the building itself, and the relationship between the first natural period and the damping ratio becomes hィイD2TィエD2TィイD2TィエD2=0.02. It implies that a larger damping ratio is obtained in case the natural period of a building is short. Less
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