Terrestrial laser scanning-based stress estimation model using multi-dimensional double layer lattices

In the field of structural health monitoring, terrestrial laser scanning (TLS) is commonly used as a measurement method for structural safety evaluation. However, the major disadvantages of using laser pulses is the possibility of data discontinuity and the likelihood of the existence a certain level of error because acquired points tend to not have a uniform distribution. This paper suggests a stress distribution estimation model for elastic beam structures using multi-dimensional double-layer lattices composed of main layer lattices with a specific constraint range as well as sublayer lattices that depend on the main lattices. The purpose of using the proposed double-layer lattice is to overcome not only the limitations of the existing method, which is based on the single shape function, but also the difficulty of evaluating responses of irregular distribution characteristics of point clouds corresponding to the accuracy of TLS. The representative points from each lattice are used to extract the deformed shape of a target, and the curvature distortion that occurs owing to error points is minimized through cubic smoothing spline interpolation. Based on the Euler-Bernoulli beam theory, the stress of the beam structure is calculated for the direction of gravity. Three static loading tests for 4-m long steel beams were conducted to verify the proposed model. The comparison of the measured and estimated values showed errors of less than 5% at the maximum displacement point, thereby validating the effectiveness of the proposed method.