http://hdl.handle.net/2451/37859 2026-04-15T07:15:26Z 2026-04-15T07:15:26Z Gyetvai, Nora Truong-Hong, Linh Laefer, Debra F. http://hdl.handle.net/2451/44474 2019-07-16T15:13:02Z 2018-05-01T00:00:00Z

Title: Laser Scanning-Based Diagnostics In The Structural Assessment Of Historic Wrought Iron Bridges Authors: Gyetvai, Nora; Truong-Hong, Linh; Laefer, Debra F. Abstract: This paper introduces a workflow to create the geometric documents for conducting finite element based structural assessment of wrought iron bridges using laser scanning data as the input dataset. First, a methodology for identifying actual cross-sections of the bridge components based on a point cloud obtained from a terrestrial laser scanner (TLS) is presented. Next, a non-parametric regression kernel density estimation is employed to determine the overall bridge dimensions to populate a computation model by projecting the position of the web and/or flange surface of the cross-section (appearing as local maximum peaks of a probability density shape). The process is demonstrated with respect to the previously undocumented Guinness Bridge in Dublin, Ireland to determine the bridge’s behaviour. The successful generation of this model proves that TLS can surpass other common techniques (e.g. UAV-based images) for acquiring the bridge geometry necessary for reconstructing accurate member cross-sections and overall bridge dimensions, regarding quantity and quality of the data points, and timing. The finite element analysis showed that the bridge currently satisfies both strength and serviceability requirements under self-weight, but would be unlikely to support a new slab and a modern pedestrian load level as per current code requirements for re-opening the bridge.

2018-05-01T00:00:00Z Natanzi, Atteyeh S. Laefer, Debra F. Kakali, Glikeria Zolanvari, S.M. Iman http://hdl.handle.net/2451/44419 2019-07-23T19:17:39Z 2019-07-01T00:00:00Z

Title: Temperature-induced Chemical Changes in Soundless Chemical Demolition Agents Authors: Natanzi, Atteyeh S.; Laefer, Debra F.; Kakali, Glikeria; Zolanvari, S.M. Iman Abstract: This paper explores the relationship between ambient temperature, calcium oxide (CaO) hydration, and calcium carbonate (CaCO3) 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 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: (1) the unconfined portions of hydrated specimens contained more CaCO3 due to carbonation of Ca(OH)2, where confined portions had higher Ca(OH)2 concentrations; (2) all materials tested at 19°C ambient temperatures had Ca(OH)2 concentrations nearly 10% greater than those tested at 2°C; and (3) the higher Ca(OH)2 concentrations formed at 19°C generated 350% greater expansive pressure than that which formed at 2°C.

2019-07-01T00:00:00Z Chen, Siyuan Laefer, Debra F. Mangina, Eleni Zolanvari, Iman Byrne, Jonathan http://hdl.handle.net/2451/43761 2019-07-23T19:17:39Z 2019-01-16T00:00:00Z

Title: UAV Bridge Inspection through Evaluated 3D Reconstructions Authors: Chen, Siyuan; Laefer, Debra F.; Mangina, Eleni; Zolanvari, Iman; Byrne, Jonathan Abstract: Imagery-based, three-dimensional (3D) reconstruction from Unmanned Aerial Vehicles (UAVs) holds the potential to provide safer, more economical, and less disruptive bridge inspection. In support of those efforts, this paper proposes a process using an imagery-based point cloud. First, a bridge inspection procedure is introduced, including data acquisition, 3D reconstruction, data quality evaluation, and subsequent damage detection. Next, evaluation mechanisms are proposed including checking data coverage, analysing points distribution, assessing outlier noise, and measuring geometric accuracy.  In this final aspect, the “Guide to the Expression of Uncertainty in Measurement” was used. The overall approach is illustrated in the form of a case study with a low-cost UAV. Areas of particular coverage difficulty involved slim features such as railings, where obtaining sufficient features for image matching proved challenging. Shadowing and large tilt angles hid or weakened texturing surfaces, which also interfered with the matching process. Description: Final published version available at https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29BE.1943-5592.0001343

2019-01-16T00:00:00Z Zahiri, Zohreh Laefer, Debra Gowen, Aoife http://hdl.handle.net/2451/43663 2019-07-23T19:17:40Z 2019-01-01T00:00:00Z

Title: Classification of hardened cement and lime mortar using short-wave infrared spectrometry data Authors: Zahiri, Zohreh; Laefer, Debra; Gowen, Aoife Abstract: This paper evaluated the feasibility of using spectrometry data in the short-wave infrared range (1,300-2,200nm) to distinguish lime mortar and Type S cement mortar using 42 lab samples (21 lime-based, 21 cement-based) each 404040mm were created. A Partial Least Squares Discriminant Analysis model was developed using the mean spectra of 28 specimens as the calibration set. The results were tested on the mean spectra of the remaining 14 specimens as a validation set. The results showed that, spectrometry data were able to fully distinguish modern mortars (made with cement) from historic lime mortars with a 100% classification accuracy, which can be very useful in archaeological and architectural conservation applications. Specifically, being able to distinguish mortar composition in situ can provide critical information about the construction history of a structure, as well as to inform an appropriate intervention scheme when historic material needs to be repaired or replaced.

2019-01-01T00:00:00Z