Deformation Monitoring Using A Terrestrial Laser Scanner: A Case Study Of Alausa Shopping Mall, Ikeja, Lagos, Nigeria

Abstract

Deformation refers to the continuous transformation of a structure from a reference configuration to a current configuration. The passage of time causes significant damage to buildings, so it is necessary to carry out monitoring procedures. Hence, the objective of this paper is to monitor the deformation of Alausa Shopping Mall, Ikeja, Lagos, Nigeria using a Polaris Terrestrial Laser Scanner to ascertain the structure's stability. The Polaris Terrestrial Scanner was used to acquire the point cloud of the structure; which represents the as-is geometries of the structure, and when imported into a BIM software environment, a 3D point cloud model, which represents the current state of the structure is created. The dimension of the building was acquired from the Lagos state vector, and when combined with height data, a 3D model representing the As-built building was developed. Then a comparison between the 3D point cloud and the As-built model was performed by comparing building segments in the 3D point cloud model with their corresponding segments in the As-built model which resulted in the determination of the horizontal and vertical displacements. The horizontal displacement rate was calculated to be 0.593mm per year, and the vertical displacement rate recorded was 3.845mm per year. Predictions of the displacement rates over 50 years at 10 years intervals were made, with the maximum (after 50 years) as 29.65mm and 192.25mm at the horizontal and vertical, respectively. Therefore, monitoring of structure should be a continuous process in the build environment.