• Ming-Hsiang Shih

      Articles written in Sadhana

    • Development of digital image correlation method to analyse crack variations of masonry wall

      Shih-Heng Tung Ming-Hsiang Shih Wen-Pei Sung

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      The detection of crack development in a masonry wall forms an important study for investigating the earthquake resistance capability of the masonry structures. Traditionally, inspecting the structure and documenting the findings were done manually. The procedures are time-consuming, and the results are sometimes inaccurate. Therefore, the digital image correlation (DIC) technique is developed to identify the strain and crack variations. This technique is non-destructive for inspecting the whole displacement and strain field. Tests on two masonry wall samples were performed to verify the performance of the digital image correlation method. The phenomena of micro cracks, strain concentration situation and nonuniform deformation distribution which could not have been observed preciously by manual inspection are successfully identified using DIC. The crack formation tendencies on masonry wall can be observed at an earlier stage by this proposed method. These results show a great application potential of the DIC technique for various situations such as inspecting shrinkage-induced cracks in fresh concrete, masonry and reinforced concrete structures, and safety of bridges.

    • Application of digital image correlation method for analysing crack variation of reinforced concrete beams

      Ming-Hsiang Shih Wen-Pei Sung

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      The Digital Image Correlation (DIC) method is a fast-growing emerging technology that provides a low-cost method for measuring the strain of an object. In this study, the feasibility of using this method to observe cracks developed in reinforced concrete beams will be explored so that a practical application can be proposed. The DIC method has been applied for analysing the field of surface displacement and strain; it is not applicable for measuring non-continuous field of displacement. However, if a singular point (i.e., crack points) can be considered as the area of concentrated strain by imitating the treatment of micro-cracks using the finite element method, the region of concentrated strain field based on analyses of digital images can be applied for determining the locations of cracks. Laboratory results show that cracks developed in reinforced cement beams can be observed with a good precision using the von Mises strain field, and that smaller grids lead to clearer crack images. In addition to identifying visible cracks, the DIC image analysis will enable researchers to identify minute cracks that are not visible to naked eyes. Additionally, the DIC method has more accuracy and precision than visual observation for analysing crack loadings so that earlier warnings can be realized before cracks develop in the specimen.

    • Development of semi-active hydraulic damper as active interaction control device to withstand external excitation

      Ming-Hsiang Shih Wen-Pei Sung

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      Semi-automatic control systems have the characteristics of being adaptable and requiring low energy. The objective of this research was to study the performance of an improved DSHD (Displacement Semi-Active Hydraulic Damper) by converting it to AIC (Active Interaction Control Device) with the addition of an accumulator. The prototype was tested using full-scale elements for examining the structural displacement, and typical responses of the interacting interface element developed in this research, the pressure variation of the pressure storage device, and the energy dissipation hysteresis loop when the structure installed with these elements is subjected to external force of various magnitude. The laboratory results confirm that the device developed in this research is capable of applying the energy dissipation characteristics of DSHD so that these elements are appropriate for developing the proposed AIC. The mutual interaction between the subordinate structure and the main structure to be protected is capable of transforming the quake energy applied to the main structure to the subordinate structure so that the objective of minimizing the deformation of main structural can be achieved.

    • Applying the digital-image-correlation technique to measure the deformation of an old building’s column retrofitted with steel plate in an in situ pushover test

      Shih-Heng Tung Ming-Hsiang Shih Wen-Pei Sung

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      An in situ pushover test is carried out on an old building of Guan-Miao elementary school in south Taiwan. Columns of this building are seismically retrofitted with steel plate. The DIC (digital-image-correlation) technique is used to measure the deformation of the retrofitted column. The result shows that the DIC technique can be successfully applied to measure the relative displacement of the column. Additionally, thismethod leads to the measurement of relative displacements formany points on the column simultaneously. Hence, the column deformation curve, rotation and curvature can be determined using interpolation method. The resulting curvaturediagram reveals that the phenomenon of plastic hinge occurs at about 2% storey drift ratio, and that the DIC technique can be applied to measure column deformation in a full scale in situ test.

    • Accuracy verification of a simple local three-dimensional displacement measurement method of DIC with two images coordinates

      MING-HSIANG SHIH SHIH-HENG TUNG HAN-WEI HSIAO WEN-PEI SUNG

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      There are two methods applied for three-dimensional digital image correlation method to measure three-dimensional displacement. One is to measure the spatial coordinates of measuring points by analyzing the images. Then, the displacement vectors of these points can be calculated using the spatial coordinates of these points obtained at different stages. The other is to calibrate the parameters for individual measuring points locally. Then, the local displacements of these points can be measured directly. This study proposes a simple local three-dimensional displacement measurement method. Without any complicated distortion correction processes, this method can be used to measure small displacement in the three-dimensional space through asimple calibration process. A laboratory experiment and field experiment are carried out to prove the accuracy of this proposed method. Laboratory test errors of one-dimensional experiment are similar to the accuracy of theXYZ table; the error in Z-direction is only 0.0025&#37 of the object distance. The measurement error of laboratory test is about 0.0033&#37 of the object distance for local three-dimensional displacement measurement test. Test and analysis results of field test display that in-plane displacement error is only 0.12 mm, and the out-of-plane error is 1.1 mm for 20 m 9 30 m measuring range. The out-of-plane error is only about 10 PPM of the object distance. These test and analysis results show that this proposed method can achieve very high accuracy under small displacement for both of laboratory and field tests.

    • Shaking table test and verification of development of an accumulated semi-active hydraulic damper as an active interaction control device

      MING-HSIANG SHIH WEN-PEI SUNG

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      Semi-active control is based on the use of the emerging concept of active control and passive control. The developed accumulator semi-active hydraulic damper (ASHD) is converted to interaction element (IE) of active interaction control (AIC). Systemic equations of motion, control law and control rulers of this proposed new AIC are studied in this research. A full-scale multiple degrees of freedom shaking table is tested toverify the energy dissipation of this proposed AIC, including test building without control, with passive control added involving various stiffness ratios and also with synchronic control added involving various stiffness ratios. Shock absorption of displacement can be up to 74–81% of that of the test structure with stiffness ratio = 2.3387 and 1.790 at 1st and 2nd floor under control of synchronous switch of this proposed AIC, respectively. No matter what the test structure added with various stiffeners at 1st and 2nd floor under synchronous control, test results of shock absorption ratio of acceleration show good seismic proof capability. In addition, base shear control effects of this proposed AIC method are higher than those of the test structure with various stiffeners added underpassive control. These results show that AIC with stiffeners for structural control provides the characteristics of a stabilized structure under excitation of near-fault earthquake with velocity impulse action

    • A method for correcting radial distortion based on verifying the planarity of specimens

      MING-HSIANG SHIH SHIH-HENG TUNG

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      Image distortion is inevitable when an image is captured through a lens. While the digital image measurement technique is getting popular, image distortion problem can result in significant error. A new distortion correction method is proposed in this study. The proposed method is based on the fact that a flat surface should keep flat when it is measured using three-dimensional (3D) digital image measurement technique. The 3D digital image measurement technique adopted in this research is the simplified 3D digital image correlation (DIC) method. Because radial distortion has a more noticeable influence than other types of distortions,this method deals only with radial distortion. A few experiments are carried out in this study to verify the correctness of this method and its accuracy. Both simulated data and actual image data are adopted in these experiments. The results show that this method can achieve a good accuracy. The standard deviations caused byrandom errors are about the same order as the random errors. It also shows that this method is suitable for both large and small distortion conditions

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