This paper presents a new approach of health monitor using the curvature of the influence line. The study included numerical simulation and experimental test of H-beam to demonstrate the effectiveness of the new approach. The specific work includes: loading test method for moving vehicular to measure displacement influence line of beam structure, obtaining Eigen-damage intrinsic mode function (IMF) of displacement influence line with ensemble empirical mode decomposition (EEMD), processing the second-derivative on displacement influence line to obtain curvature influence line of Eigen-damage IMF, fitting against which through polynomial to obtain quasi-undamaged curve, using the product of absolute difference from both curvature influence line and quasi-undamaged curve to identify damage location of beam structures by means of the product of curvature difference map after fitted. Theoretical development and experimental verification are carried out on H-beam in this paper. In the experiment, measures of displacement influence line at middle span (L/2) of the H-beam when moving vehicular pass by. EEMD, curve fitting and calculating curvature of displacement influence line, etc. methods are used to process displacement influence line. The advantages of this experimental method are fast, time-saving, simple equipment set-up, and can avoid the disturbance of surrounding environmental vibration, but also trouble in a shortage of undamaged condition for the structure. ANSYS software in the paper simulates displacement influence line at middle span under loading test for H-beam to understand the change of displacement influence line for damage identification, which is used as a basis of theoretical development. Finally, conduct loading test method for moving vehicular to measure displacement influence line at middle span of H-beam; connecting with EEMD, curve fitting, and calculating the curvature of displacement influence line can effectively and quickly identify damaged location.

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A useful nondestructive testing tool for civil engineering should immediately reveal defects inside concrete structures at the construction sites. To date, there are few effective methods to image defects inside concrete structures. In this paper, a new nondestructive testing method using elastic waves for imaging possible defects inside concrete is developed. This method integrates the point-source/point receiver scheme with the synthetic aperture focusing technique (SAFT) to increase functioning depth and enhance received signals. To improve image quality, received signals are processed by Hilbert-Huang transform (HHT) to get time-frequency curves for the SAFT process. Compared with conventional SAFT method processing with time-amplitude signals, this new method is capable of providing a better image of defects not only in the numerical simulation but also in the experimental result. The image can reveal the number of defects and their locations and front-end profiles. The results shown in this paper indicate that this new elastic-wave-based method exhibits high capability in imaging the defects of in situ concrete structures.