Abstract: To implement realtime monitoring for steel structure of vibration state,we employ digital photography technology to observe deformed steel structure.We capture instantaneous continuous deformation information for loaded and unloaded steel structures with multiple direct linear transformation method calibrated digital cameras. We further recognize and localize circular marks through Hough transform mathematical model and get image coordinates of a deformation point.The image coordinates are processed and drew into a deformation curve whose observation accuracy can reach 3/1 000. Experimental results show that we can achieve multipoints and instantaneous observation by this technology, and can capture instantaneous deformation information.The observation precision can also satisfy the requirement of structural deformation observation.

Key words: steel structure, ground motion, deformation observation, digital photography