Now showing 1 - 4 of 4
  • Publication
    Slicing Method for curved façade and window extraction from point clouds
    Laser scanning technology is a fast and reliable method to survey structures. However, the automatic conversion of such data into solid models for computation remains a major challenge, especially where non-rectilinear features are present. Since, openings and the overall dimensions of the buildings are the most critical elements in computational models for structural analysis, this article introduces the Slicing Method as a new, computationally-efficient method for extracting overall façade and window boundary points for reconstructing a façade into a geometry compatible for computational modelling. After finding a principal plane, the technique slices a façade into limited portions, with each slice representing a unique, imaginary section passing through a building. This is done along a façade’s principal axes to segregate window and door openings from structural portions of the load-bearing masonry walls. The method detects each opening area’s boundaries, as well as the overall boundary of the façade, in part, by using a one-dimensional projection to accelerate processing. Slices were optimised as 14.3 slices per vertical metre of building and 25 slices per horizontal metre of building, irrespective of building configuration or complexity. The proposed procedure was validated by its application to three highly decorative, historic brick buildings. Accuracy in excess of 93% was achieved with no manual intervention on highly complex buildings and nearly 100% on simple ones. Furthermore, computational times were less than 3 sec for data sets up to 2.6 million points, while similar existing approaches required more than 16 hr for such datasets.
    Scopus© Citations 73  767
  • Publication
    Temperature-induced Chemical Changes in Soundless Chemical Demolition Agents
    This paper explored the relationship between ambient temperature, calcium oxide (CaO) hydration, and calcium carbonate (CaCO3CaCO3) generation in cold and moderate ambient temperatures (2°C–19°C). A total of 22 samples from 2 commercial soundless chemical demolition agents (SCDAs) were tested in 36-mm-diameter×170-mm-long36-mm-diameter×170-mm-long steel pipes. The raw powder and materials resulting from hydration were subjected to X-ray diffraction analysis, derivative thermogravimetric analysis, and thermogravimetry analysis. Raw and hydrated specimens proved chemically distinctive. Experimental results showed that (1) the unconfined portions of hydrated specimens contained more CaCO3CaCO3 due to carbonation of Ca(OH)2Ca(OH)2, and confined portions had higher Ca(OH)2Ca(OH)2concentrations; (2) all materials tested at 19°C ambient temperature had Ca(OH)2Ca(OH)2concentrations nearly 10% greater than those tested at 2°C; and (3) the higher Ca(OH)2Ca(OH)2 concentrations formed at 19°C generated 350% greater expansive pressure than did those that formed at 2°C.
    Scopus© Citations 11  199
  • Publication
    Three-dimensional building façade segmentation and opening area detection from point clouds
    Laser scanning generates a point cloud from which geometries can be extracted, but most methods struggle to do this automatically, especially for the entirety of an architecturally complex building (as opposed to that of a single façade). To address this issue, this paper introduces the Improved Slicing Method (ISM), an innovative and computationally-efficient method for three-dimensional building segmentation. The method is also able to detect opening boundaries even on roofs (e.g. chimneys), as well as a building’s overall outer boundaries using a local density analysis technique. The proposed procedure is validated by its application to two architecturally complex, historic brick buildings. Accuracies of at least 86% were achieved, with computational times as little as 0.53 s for detecting features from a data set of 5.0 million points. The accuracy more than rivalled the current state of the art, while being up to six times faster and with the further advantage of requiring no manual intervention or reliance on a priori information.
    Scopus© Citations 48  1218
  • Publication
    Impact of thermal transfer on hydration heat of a Soundless Chemical Demolition Agent
    This paper explores thermal transfer effects in Soundless Chemical Demolition Agents (SCDA). In a 10°C water bath, quadrupling the volume of SCDA in a pipe accelerated peak hydration onset and resulted in a 700% increase in expansive pressure and a 20% increase in volumetric expansion. An equivalent sample in a constant temperature chamber showed an almost 5°C greater hydration heat than in the water bath, which resulted in a six-fold expansive pressure difference after 4 days of testing and an order of magnitude more pressure in the first 24 h, thereby demonstrating limitations of previous SCDA experimental work and providing a temperature-based reason for discrepancies between large-scale testing and manufacturers’ predictions. Since most construction projects have scheduling requirements, understanding how to achieve sufficiently high pressures within a single work shift is important for evaluating the field viability of SCDAs on a particular project.
    Scopus© Citations 36  523