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Wu H.-L.,Hunan Dayue Freeway Construction and Development Co. | Xie J.-J.,Hunan Zhongda Design Institute Co. | Xiong Z.,Hunan Dayue Freeway Construction and Development Co.
Zhendong yu Chongji/Journal of Vibration and Shock

The element residual energy was defined and its sensitivity was analyzed. Furthermore, the structural damage identification method based on the sensitivity of element residual energy was presented and the corresponding equations were established, by solving which, damage location and severity can be simultaneously determinated. Numerical simulations show that the proposed method is effective in different damage cases. Source

Han J.-P.,Lanzhou University of Technology | Han J.-P.,Tongji University | Li D.-W.,Hunan Zhongda Design Institute Co.
Gongcheng Lixue/Engineering Mechanics

Identifying modal parameters via processing vibration signals is one of the mainstream approaches for structural health monitoring and damage diagnosis. The processing approaches based on Fourier analysis are not able to process nonlinear and non-stationary signals. In addition, most of traditional identification methods suffer from low precision to identify damping. Therefore, a new approach is proposed for identifying modal parameters based on Hilbert-Huang transform (HHT) and natural excitation technique (NExT). First, the instantaneous characteristics of the original signal are extracted by means of empirical mode decomposition (EMD) and Hilbert transform (HT). Then, NExT and basic modal analysis theory are used to identify modal frequencies and modal damping ratios. Furthermore, the original acceleration record from the shaking table test of a 12-storey RC frame model is processed and modal parameters are identified by the proposed approach. And identification results are compared with the results from other identification algorithms and finite element analysis. Comparison indicates that the proposed approach is reliable to identify modal frequencies. Although identification of modal damping ratios gets improved by comparison with half-power bandwidth method, it is still difficult to confirm the precision of the results. Source

Xiao J.,Central South University | Chen L.,Bridge Science Research Institute LTD | Xing H.,Hunan Zhongda Design Institute Co.
Jianzhu Cailiao Xuebao/Journal of Building Materials

The influence of fly ash and slag powder on the autogenous shrinkage of cement mortars was studied. The experiment test results indicate that the autogenous shrinkage of cement mortar made with 1:0.5 binder to sand ratio (by mass) and 0.3 water to binder ratio (by mass) increases with development of hydration. At early age, rate of autogenous shrinkage develops sharply. Addition of fly ash reduces the autogenous shrinkage of cement mortar, and the autogenous shrinkage of cement mortar decreases with increase of fly ash content (by mass). Compared to pure cement mortar, after hydrated for 21d, the 10% and 20% of fly ash addition reduce autogenous shrinkage of cement mortar by 21.1% and 29.5% respectively. Originally within 5d, the 10%-20% (by mass) of slag powder addition decreases autogenous shrinkage of cement mortar. Compared to pure cement mortar, after hydrated for 21d, the 10% and 20% of slag powder addition increase autogenous shrinkage of cement mortar by 11.1% and 6.6% respectively. Source

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