Non-contacting monitor for bridges and civil structures
A method for monitoring the condition of a bridge includes: stably positioning a video camera at a selected location with an unobstructed view of a selected portion of the bridge structure; collecting a video file of the structure over a selected total time interval; using a data processing system to analyze the video and calculate a physical parameter related to movement of the selected portion as a function of time, wherein the data processing system is controlled through a graphical user interface (GUI) having the following features: a display of a single video frame corresponding to a selected time; a movable area selector in the video frame to indicate the selection of an area of the structure for analysis; and, a display of displacement versus time for the selected area over the total time interval. The processor may perform some tasks, e.g., area selection, autonomously or via predetermined rules.
1. A method for monitoring the condition of a bridge comprising the steps of:
stably positioning a video camera at a selected location and having an unobstructed view of a selected portion of the bridge structure;
collecting a video file of said structure over a selected total time interval;
using a data processing system to analyze the video and calculate a physical parameter related to movement of said selected portion of said bridge structure as a function of time, wherein said data processing system is controlled through a graphical user interface (GUI) having at least the following features:
a display of a single video frame corresponding to a selected time within said total time interval;
a movable area selector superimposed on said video frame to indicate the selection of an area of said structure for analysis; and,
a display of displacement versus time for said selected area over said total time interval.
2. The method of claim 1 wherein said display of displacement versus time has therein a first movable cursor to allow a user to select a particular time within said total time interval and cause the GUI to display the particular video frame corresponding to that particular time.
3. The method of claim 1 further including the step of:
populating a searchable database with the video file and selected metadata associated with said video file.
4. The method of claim 1 further including the steps of:
selecting a first area of said structure and calculating a physical displacement associated with said first area;
selecting a second area of said structure and calculating a physical displacement associated with said second area;
comparing the displacements in said first and second areas to determine spatial variations in structural behavior within said bridge.
5. The method of claim 1 further including the steps of:
collecting video files of the same structure at different times; and,
comparing the displacement of a selected area of said structure at said different times to determine changes in the structural behavior of said bridge over time.
6. The method of claim 1 further including the further of:
collecting a video file while a vehicle of known mass traverses said bridge, and analyzing said video file to provide a calibrated baseline for comparison to files acquired for the same bridge at later times.
7. The method of claim 3 wherein said selected metadata associated with each video file may include data selected from the group consisting of: specific bridge identifier; bridge location; bridge type; date; time; weather conditions; bridge loading; traffic conditions; locations of selected areas analyzed and maximum deflections at said selected areas; and position of video camera relative to bridge.
8. The method of claim 1 wherein said searchable database includes data sets created by multiple users and is accessible to multiple users so that a larger amount of comparative data is available to each user and a particular bridge may be compared to a larger population of comparable bridges.
9. The method of claim 8 wherein said searchable database resides in the user's data processing system and is periodically updated by adding data from other systems and users.
10. The method of claim 8 wherein said searchable database resides in a centralized server accessible to users via any suitable communication means.
11. The method of claim 1 wherein said camera is positioned on the ground at a selected distance from said bridge.
12. The method of claim 1 wherein said camera is positioned on said bridge with an unobstructed view of a portion of the bridge structure.
13. The method of claim 1 wherein said physical parameter related to movement of said selected portion of said bridge structure is selected from the group consisting of: physical displacement; frequency; phase; maximum displacement; and damping rate.
14. The method of claim 1 wherein said movable area selector in said GUI comprises a user-generated box of a selected size and shape defining a selected portion of said video frame for analysis.
15. The method of claim 1 wherein said movable area selector in said GUI comprises a user-selected X,Y coordinate and a user-defined set of pixels centered on said X,Y coordinate in said video frame.
16. The method of claim 1 wherein said GUI further allows the user to define a line segment on said video image for use as a reference for measuring displacements and analyzing movement along said line segment.
17. The method of claim 1 wherein said GUI further includes an output selected from the group consisting of:
still images containing phase information;
still images containing frequency information;
still images containing edge enhancement;
moving images displaying motion amplification; and,
audio recordings.
18. The method of claim 1 wherein said movable area selector is controlled by said data processing system using a rules-based process.
19. The method of claim 18 wherein said data processing system performs an edge detection step and then uses said rules-based process to select areas along said edges for analysis.