洪士林土木系 - Academia.edu (original) (raw)

Papers by 洪士林土木系

This work presents a digital image processing approach with a unique hive triangle pattern by int... more This work presents a digital image processing approach with a unique hive triangle pattern by integrating subpixel analysis for noncontact measurement of structural dynamic response data. Feasibility of proposed approach is demonstrated based on numerical simulation of a photography experiment. According to those results, the measured time-history displacement of simulated image correlates well with the numerical solution. A small three-story frame is then mounted on a small shaker table, and a linear variation differential transformation (LVDT) is set on the second floor. Experimental results indicate that the relative error between data fromLVDT and analyzed data fromdigital image correlation is below 0.007%, 0.0205 in terms of frequency and displacement, respectively. Additionally, the appropriate image block affects the estimation accuracy of the measurement system. Importantly, the proposed approach for evaluating pattern center and size is highly promising for use in assigning the adaptive block for a digital image correlation method.

This study developed an integrated global-local approach for locating damage on building structur... more This study developed an integrated global-local approach for locating damage on building structures. A damage detection approach with a novel embedded frequency response function damage index (NEFDI) was proposed and embedded in the Imote2.NETbased wireless structural health monitoring (SHM) system to locate global damage. Local damage is then identified using an electromechanical impedance- (EMI-) based damage detection method. The electromechanical impedance was measured using a single-chip impedancemeasurement device which has the advantages of small size, low cost, and portability. The feasibility of the proposed damage detection scheme was studied with reference to a numerical example of a six-storey shear plane frame structure and a small-scale experimental steel frame. Numerical and experimental analysis using the integrated global-local SHM approach reveals that, after NEFDI indicates the approximate location of a damaged area, the EMI-based damage detection approach can then identify the detailed damage location in the structure of the building.

This work develops an augmented particle swarm optimization (AugPSO) algorithm using two new stra... more This work develops an augmented particle swarm optimization (AugPSO) algorithm using two new strategies,:
boundary-shifting and particle-position-resetting. The purpose of the algorithm is to optimize the
design of truss structures. Inspired by a heuristic, the boundary-shifting approach forces particles to move
to the boundary between feasible and infeasible regions in order to increase the convergence rate in searching.
The purpose of the particle-position-resetting approach, motivated by mutation scheme in genetic
algorithms (GAs), is to increase the diversity of particles and to prevent the solution of particles from
falling into local minima. The performance of the AugPSO algorithm was tested on four benchmark truss
design problems involving 10, 25, 72 and 120 bars. The convergence rates and final solutions achieved
were compared among the simple PSO, the PSO with passive congregation (PSOPC) and the AugPSO
algorithms. The numerical results indicate that the new AugPSO algorithm outperforms the simple PSO
and PSOPC algorithms. The AugPSO achieved a new and superior optimal solution to the 120-bar truss
design problem. Numerical analyses showed that the AugPSO algorithm is more robust than the PSO and
PSOPC algorithms.

This study presents a digital image processing technique, by integrating sub-pixel analysis using... more This study presents a digital image processing technique, by integrating sub-pixel analysis using digital image correlation method with a novel hive-grid target, for the measurement of structural experiment data. First, a numerical simulation of photography experiment at short range is employed to validate the feasibility of proposed approach. Herein, the simulation image caught from digital speckle and hive-grid target are compared, and the measured time-history displacement of simulation image is computed by the digital image correlation and edge detection methods. The results reveal that, via the digital image correlation method with hive-grid target, the measured time-history displacement at specific position can be analyzed accurately. Following, the experimental data gained from LVDT and digital camera for a six-storey steel frame at National Center for Research on Earthquake Engineering (NCREE) in Taiwan is used to verify the performance of the proposed approach. The measured time-history displacements of the steel frame are converted into frequency domain via Fourier Transform and Wavelet Transform schemes. The results revealed that the relative error between data from LVDT and analyzed data from digital image correlation is below 1% on frequency domain. Herein, the sampling rate of digital camera is lower than LVDT, because high sampling rate led to underexposure and large data storage. The frame rate of common digital camera is about 30 frames/sec nowadays, however the high speed digital camera can overcome this restriction. The limitation of high sampling rate is exposure time and data storage. The experimental results of numerical simulation and shaking table test revealed that digital image correlation method with hive-grid target is accurate in high resolution images.

洪士林 土木系 - Academia.edu (original) (raw)

Papers by 洪士林 土木系

洪士林土木系 - Academia.edu (original) (raw)

Papers by 洪士林土木系