Cracks induced by external excitation on a material that has defects may generate the stress concentration phenomenon. The stress concentration behaviour causes local budding, which will induce the damage of the members made of this material. Thus, developing techniques to monitor the strain variation of a cracked member is an important study. The traditional technique (such as strain gauge) can only measure the average strain of a region. The strain variation within this region cannot be determined. Therefore, it cannot sufficiently reflect the mechanical behaviour surrounding the crack. The Digital image correlation technique recently developed is an image identification technique to be applied for measuring the object deformation. This technique is capable of correlating the digital images of an object before and after deformation and further determining the displacement and strain field of an object based on the corresponding position on the image. In this work, this technique is applied to analyse the mechanics of a cylindrical pipe experiencing crack destruction. The fixing device is used to avoid shaking the specimen during the pressurizing process. The image capture instruments are fixed on the stable frame to measure the deformation of specimen accurately. Through the cylindrical pipe cracking test, the capacity of the digital image correlation technique for surveying the strain variation in a tiny region is validated. Then, the experimental results obtained using the digital image correlation analysis is used to demonstrate the crack development tendency in defect materials and the stress concentration zone

In earthquake engineering, a hydraulic damper is a kind of energy-dissipating device to reduce the structural response. Newly developed Displacement Dependent Semi-Active Hydraulic Damper (DSHD) is one of the hydraulic dampers. For this damper, the hydraulic cylinder is acting as a damper connector. This damper connector is like a flexible switch with tight-loose and close-open functions and is used to connect a structure and a resistance component. For a DSHD-added structure, to linearize the nonlinear behavior of DSHD is required for preliminary design. Using the damping ratio as a parameter, the DSHD is modeled as a fixture of a linear spring and linear viscous damper. This approach is valid for application in the engineering practice

In structural engineering, the damping device is the best way to equip the structure for resisting earthquakes. The newly developed displacement dependent semi-active hydraulic damper (DSHD) is a kind of hydraulic damper to reduce the structural response. The DSHD is a fixture connecting the brace and the structure. At a seismic loading, the DSHD is functioned to dissipate the energy at the transition of bracing from the tensile constraint to the compressive constraint or in reverse. When a structure suffers a large seismic excitation, the overflow function is triggered to prevent the failure of a bracing member. That is, at the stress in the linked brace reaching a certain value, it will start the opening of the overflow valve maintaining an aptotic pressure for confining the bracing deformation within the design value. This DSHD provides availability for resisting excessive vibration in the structural design. In this paper, the analysis modeling is set up for simulating the nonlinear behavior of DSHD. The performance of DSHD is investigated in the nonlinear analysis for seismic evaluation

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