Developing procedures for post-earthquake structural evaluation by laser scanning techniques

There have been several safety issues related to the post-disaster evaluation of buildings devastated by natural forces or human actions. Excessive deformation or damage occurring at the main load-carrying members frequently raise concerns about safety for.field investigators. To evaluate structural integrity in a conventional manner, they must risk their lives and physically enter the building to perform surveying through direct contact. However, timing is crucial and the data collected must be thorough because the building often remains in an unstable condition. It is desirable to measure the overall spatial information in a short period of time by using 3D laser scanners with a high-precision measuring capacity. To propose a standard procedure for data acquisition using 3D laser scanners in the post-disaster evaluation of buildings, the research team reported the results of a full-scale push-over lest on a two-storey classroom building in 2005 and a field investigation of a classroom building damaged during the 921 Chi-Chi earthquake. An optimised data acquisition procedure, precision assessment and post-processing program for 3D laser scanning of structural deformation were developed afterwards. The case studied suggests that 3D laser scanners are suitable and have the capacity to obtain three-dimensional measurements as required in a short time. The technology should be used in post-disaster investigations of buildings to acquire the displacement information of columns and beams for rapid safety evaluations. Moreover, information such as the degree of tilting and width of cracks can also be obtained using the post-processing program. This paper introduces a working procedure summarising lessons learned and knowledge gained in the pilot tests.