Fifth Tongji-UBC Symposium on Earthquake Engineering REN Xiangxiang Research Institute of Structural...

Fifth Tongji-UBC Symposium on Earthquake Engineering

REN Xiangxiang

Research Institute of Structural engineering and Disaster Reduction

2015/05/04

Dynamic Similitude Mechanism and

Design of Base-isolated Model


1. Similitude Mechanism of Base-isolated Structures

Outline

2. Design Procedure of a Base-isolated Building Model

4. Conclusion

3. Model Construction and Testing



Shanghai Oriental Pearl Tower Shanghai Tower

Similitude

Similitude


Similitude Design

Similitude Relation

LoadingPrototyp

e ModelTest

Results

Reinforced structures

steel structures

Base-isolated

• Stress-strain property during the elastic stage

• Bearing capacity of the critical elements

• The matching material

• Connections in small size

• Typical nonlinear performance



Structure

ElementMaterial

• Cross section of the critical element

• The mechanical characters of different media interface



Structure

Element

Material

Base-isolated Structures?


Structure-based similitude method


Structure-based similitude method ---the structural property and dynamic responses of the model structure keep being similar to that of the prototype structure under actions of earthquake in different level.

3）Damping ratio

Structural property Loading Structural response

1）Natrual frequncy2）Mode of vibration

4）Fai lure mode

1）Acceleration response

2）Displacement response3）Stress response



Isolation bearing arrangementIsolate layerGlobal structure

Superstructure

Transfer layer

2. Design Procedure of a Base-isolated Building


• Superstructure

1/4

The

prototype

The model



Similitude

Theoretical

model

• Transfer layer

The

prototypeProblems： Insufficient stiffness

Less bearings， insufficient overturning resistance

？



• Transfer layer

Theoretical

model

Actual model

Increase the stiffness of transfer beam

Increase the transfer layer resistance to overturning



• Isolate layer

Taking horizontal stiffness of the isolated layer as the

basic similitude factor

6 rubber laminated bearings

12 elastic sliding bearings

4rubber laminated bearings

4 elastic sliding bearings



振动台试验

Forms of the transfer layer Concrete placing Curing of the concrete

Building the wall of the first floor Wall of the first floor The global model



Shaking table

test

Seismic intensity:

7 degree

Seismic excitation: El-Centro wave

Wenchuan wave

Pasadena wave

Shanghai wave



Frequency and mode of the prototype and the model



0.02 0.025 0.03 0.035 0.040

1

2

3

4Pasadena wave

模型原型

Peak value of acceleration（ g）

Laye

r

0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.120

1

2

3

4Pasadena wave

模型原型


Laye

r0.05 0.1 0.15 0.2 0.250

1

2

3

4Pasadena wave

模型原型


Laye

r

Peak values of acceleration under Pasadena wave

Frequent earthquake Basic earthquake

Rare earthquake

Maximum acceleration distribution are in good agreement;

Peak value of the model is bigger than that of the prototype.



Frequent earthquake Basic earthquake

Rare earthquake

Acceleration response history under Pasadena wave

Acceleration response of the basic earthquake is in good agreement with the rare earthquake

Values of the model are bigger than that of the prototype under frequent earthquake.



4. Conclusion

(1) Existing similitude approaches are classified into three levels, including the material level, the elemental level and the structural level.

(2) Model of the base-isolated structures are scaled down based on similitude approach in structural level.

(3) The similitude between the model and the prototype is greatly improved compared to the traditional similitude approach.

Fifth Tongji-UBC Symposium on Earthquake Engineering REN Xiangxiang Research Institute of Structural...

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