A shear panel damper using low-yield steel is considered as one of cost-effective solutions to reduce earthquake damage to building structure. In this paper, we describe the development of a shear panel damper with high deformation capacity, which is a necessary condition for it to be a bridge bearing. The development is based on the measurement of strain distribution of the shear panels under cyclic loading test. For the measurement, an image processing technique is proposed to use with the two-dimensional finite element method, in which a constant stress triangular element is employed. The accuracy of the measurement is validated by comparing with the results acquired by strain gauges. Various shapes of shear panels are tested in the experiment to obtain the relationship between the strain distribution and the deformation capacity. Based on the results of the experiment, the shear panel damper is improved to achieve high seismic performance with large deformation capacity.
Shear panel dampers (SPDs) made of low-yield steel have been widely studied and applied to high-rise buildings as hysteretic dampers globally. When shear panel dampers are installed into building structures, they are expected to partially divert the input seismic energy into the dampers and reduce the seismic response of the structures under strong earthquake loads effectively and economically and to improve the energy dissipation capacity of the buildings [
In recent years, we have focused on developing high seismic performance shear panel damper made of the super low-yield steel LY100 with the aim of applying them in bridge structures [
The use of digital cameras and image processing in strain measurement has been extensively investigated due to the development of high-performance technology and price reduction of digital cameras during the past 30 years. These studies include strain measurements in materials forming processes [
In this paper, with the aim of obtaining the strain distribution in the panel of SPD, we present a large strain distribution measurement system by using image processing technique combined with the two-dimensional finite element method with a constant stress triangular element. The strains measured with the proposed method is validated by strain gauges, especially, in the large strain range. The relationship between the shear load-displacement and the strain distribution in the panels is studied to identify the crack initiation mechanism in the shear panel dampers, which can lead to the development of a high seismic performance shear panel damper with large deformation capacity.
The basic knowledge and general methods of image processing techniques are available in books or papers, for example, [
The flowchart for obtaining the image data from a digital camera and the calculation of the stress are shown in Figure
Flowchart of image measurements.
Position of the marks.
After these marks are recorded by a high-precision digital camera, the points are specified on the imaginary coordinates by using image processing. Subsequently, the strain is calculated using the two-dimensional finite element method (2D-FEM) with a constant stress triangular element, where the nodal points coincide with the marks on the imaginary coordinates. The image processing part in Figure
Flowchart of image processing.
We used the two-dimensional finite element method (2D-FEM) with a constant stress triangular element [
Triangular element.
The three strain components are calculated using (
Regardless of (
Figure
Position of three-axis gauges (unit: mm).
Comparison with three-axis gauge measurement.
Before the cyclic loading test, a tensile coupon test was performed to obtain the stress strain curve, as shown in Figure
Stress-strain relationship in tensile tests.
The shapes of the shear panel specimens are shown in Figure
Specimen dimensions (mm).
REC
R3
R6.5
REC-RIB
Consider
The name and characteristics of the four specimens are shown in Table
Test specimens.
Specimen | Characteristics |
---|---|
(a) REC |
|
(b) R3 | With a transition radius |
(c) R6.5 | With a transition radius |
(d) REC-RIB | With vertical stiffeners along the both sides |
Fixture and boundary condition of the specimen (Unit: mm).
Experimental equipment for the cyclic loading test.
Loading history.
The strain measurement system consists of two digital cameras, the image processing program and experimental equipment. The basic features of the digital cameras are shown in Table
Basic features of the utilized camera.
Image recorder | Nikon digital camera D40X |
---|---|
Lens type | AF-S DX ZOOM Nikkor ED 18 |
Filter size | 52 mm |
Pixel |
|
The position of the cameras relative to the specimen is shown in Figures
Camera setup.
The hysteretic relationship of the normalized shear load
Hysteretic shear load-displacement curves.
REC
R3
R6.5
REC-RIB
Deformation and destruction appearance of the test specimens.
REC
R3
R6.5
REC-RIB
Strain distributions obtained using image processing.
REC
R3
R6.5
REC-RIB
The maximum load and maximum shear deformation of each specimen are shown in Table
Maximum load and maximum shear deformation.
Specimen |
|
|
---|---|---|
(a) REC | 2.20 | 16.0 |
(b) R3 | 2.25 | 23.0 |
(c) R6.5 | 3.30 | 28.5 |
(d) REC-RIB | 3.35 | 25.0 |
As the REC-RIB was mentioned in Section
Improved shear panel dampers.
Specimen | Characteristics |
---|---|
REC-RIB-RF | REC-RIB with reinforcing plates at the upper and bottom edges of shear panel |
REC-RIB-RF-R | REC-RIB-RF with curved vertical flanges along both sides |
Shapes of the improved shear panel dampers (Unit: mm).
REC-RIB-RF
REC-RIB-RF-R
Figures
Hysteresis curves of the improved shear panel dampers.
REC-RIB-RF
REC-RIB-RF-R
Envelopesof the hysteresis curves.
Comparison of accumulated absorbing energy.
Comparing with the REC-RIB (Figure
To develop the low-yield steel shear panel damper with high deformation capacity for bridge structure, the strain distribution properties of the shear panel damper under cyclic loading were investigated by the digital image processing technology. With the presented large strain distribution measurement system, strain distributions of four types of shear panel dampers were obtained along with the hysteretic load-displacement curves. The relationship between the shear deformation performance and the stress distribution in the panels was studied to identify the crack initiation mechanism in the shear panel dampers. Based on the investigation, the shear panel damper was improved to achieve a high deformation capacity, which contributes to make it possible to be a bridge horizontal bearing.