| Abstract： On the basis of the rapid safety appraisal of buildings in seismic field carried out by the seismic department during the period of earthquake emergency response, this paper, introducing the infrared nondestructive test technology, one supplementary means of the rapid safety appraisal of buildings nowadays, employing image processing, mathematical statistics and so on, discusses the infrared images of the damaged buildings in the earthquake and analyzes their relationship with all kinds of influence factors. Based on the typical damages of buildings in seismic field in Wenchuan Earthquake, emphasis is laid on the infrared images of the buildings of frame structure, brick and concrete structure or simple structure. This paper introduces evaluation systems for earthquake damage and losses of buildings, the characteristics and duties of seismic field work at the present in our country, and highlights the typical damage of buildings of different structure together with the features of the infrared and visible images. Building materials referred to in this paper are cement mortar, reinforced concrete, red bricks, clay, phoebe bournei, asbestos shingles, cement board and so on. The surface decorations are red lacquer, white plasterer, yellow coating, and white wallpaper, red or white tiles and so on. Different materials have different physical natures, leading to different features in their infrared images. This research designs a table for each infrared image, recording the capture time, location, weather, angle, distance together with the structure types, materials, damage level of the buildings. What the correlation analysis reveals are as follows: The image gives a better presentation in the noon than in the morning, and even better in the afternoon. In practice, the afternoon should be made full use of; A good presentation can be given in the sunny days, worse in the rainy days and worst in the cloudy days；The presentation of the infrared images is good in the case of direct sunlight, worse in the case of the slanting sunlight, and worst in the case of no sunlight. The correlation analysis shows that among the destruction degrees of well preservation, slight damage and moderate damage, the effect of the images enhanced as the damage degree increases, and as for images of moderate damage, severe damage and destruction, the effect of the images is inconspicuous as the damage degree increases. According to the decoration layer shows that the effect of images is correlated to the properties, color, and surface roughness of the materials. Among all the factors, the heat absorption of the material is directly influenced by the surface color, so the influence of surface color should not be ignored. The diversity of color appearing on the same material will interfere the interpretation of the images, and INDT is also not suitable when there are many kinds of decoration layers and complex background colors. |
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