3D Laser Scanning Technique Research Articles

Experimental Investigation on the Influence of Strength Grade on the Surface Fractal Dimension of Concrete under Sulfuric Acid Attack

The corrosion of alkaline concrete materials exposed to a sulfuric acid environment is becoming more and more prevalent, and its damage assessment is becoming more and more imperative. This study aims to describe the corroded surfaces of concrete with different strength grades (C30, C50, C80) in sulfuric acid environments in terms of their three-dimensional fractal dimension. Three kinds of concrete with varying strength grades, namely C30, C50, and C80, were immersed in a sulfuric acid solution with pH ≈ 0.85 for four distinct corrosion durations, specifically 0, 28, 56, and 165 days, in accelerated corrosion tests. The 3D laser scanning technique was utilized to capture the 3D coordinates of the surface points of the concrete cylinder before and after corrosion. The fractal dimension of concrete’s uneven surface before and after corrosion was computed via the cube covering method, and the mass loss of the concrete specimen was also obtained. The outcomes demonstrate that the three-dimensional fractal dimension provides a new method for characterizing the degree of corrosion deterioration of concrete samples affected by sulfuric acid via laser scanning technology. From the perspective of the appearance, mass loss, and fractal dimension of a rough surface in the sulfuric acid environment at a pH level of approximately 0.85, the degree of the corrosion deterioration of concrete is ranked from high to low as C80 > C50 > C30. These fractal dimensions of the concrete’s corroded surfaces with various strength grades increase rapidly in the initial period. However, as the corrosion time progresses, the growth rate of the corroded surface fractal dimension gradually decelerates and tends towards stability, which accords with the law of exponential function. The widespread belief is that the higher the strength grade of concrete, the better its durability; however, this pattern varies in sulfuric acid corrosive environments. Therefore, based on this research, it is recommended that in extremely acidic environments (i.e., very low pH), more attention should be paid to high-strength grades of concrete.

3D scanning in Cultural Heritage: model creation and digital restoration of the tombstone of the bishop Vasilije Petrović (Negosh) in Saint Petersburg

3D laser and optical scanning techniques are widely employed in Cultural Heritage preservation for documenting pieces of different sizes and shapes. However, due to limitations of the methods available today, the results obtained vary according to different characteristics of the object under study. External surfaces showing very smooth features make the capturing process and the posterior processing a more elaborate task, requiring special attention and additional retouching to improve the final 3D model. Tombstones are a typical example of this type of objects, combining both flat external contours and refined outlines. In this work the procedure of creation of the digital model of the tombstone of the bishop Vasilije Petrović (Negosh) is described, a piece of art which combines both technical and historical importance. Post-processing steps required involved different software (Geomagic Design X, ZBrush, Adobe Photoshop) for surface correction and cleaning, details and photorealistic texture improvements and lost material restoration.

Experimental investigation of fixed-ended hot-rolled austenitic stainless-steel unequal-leg angles under compression

Structural stainless steel is gaining traction in the structural engineering field, however, there is currently limited published data on the performance of stainless steel unequal-leg single-angle compression members. This limitation of published data is reflected in the recently released AISC 370: Specification for Structural Stainless Steel Buildings which is limited in scope to equal-leg cross sections. Furthermore, the Specification requires the consideration of flexural–torsional buckling for single angles which is in contrast to the original design guidelines from AISC published in 2013, which mirrored the carbon steel specifications and did not required checking for flexural–torsional buckling for single angles. This paper reports a comprehensive experimental study on the behavior of hot-rolled austenitic stainless steel unequal-leg angle columns. A series of unequal-leg angles with cross-sectional dimensions of 76.2 × 50.8 × 6.35 mm (3″× 2″× 1/4″) and lengths ranging from 250 mm (10″) to 3760 mm (148″) were tested in compression. The ultimate loads were recorded in addition to displacements, twists, and failure modes through the use of strain gauges and an optical tracking system. The material properties were obtained through a series of tensile coupon tests, and the member geometric imperfections were measured through a non-contact 3D laser scanning technique. In addition, residual stress distributions were measured by the sectioning method. The results obtained from this experimental investigation indicated: (1) that torsional buckling is dominant in the shorter lengths and minor-axis flexural buckling in the longer lengths, with a transition occurring gradually in the middle lengths; (2) that the measured material properties are significantly higher than nominal values, and that this had a significant effect on the capacity predicted by the design provisions; (3) flexural buckling design provisions provide a better estimation than flexural–torsional buckling design provisions, although both are conservative.

Geospatial Tools for Determining Visitor Carrying Capacity in Tourist Streets and Public Spaces of Historic Centres

This paper presents a methodology for using geospatial tools to enact efficient tourism planning and management in streets and other public spaces in historic centres. The study uses 3D laser scanning, GIS, and spatial data processing techniques to analyse the visitor carrying capacity of streets near cultural attractions. The methodology was tested on Miguelete Street in València (Spain), next to the Cathedral. The results show that these digital tools are efficient and accurate for the spatial analysis of visitor carrying capacity studies.

Contribution of Lasergrammetry, Photogrammetry and Electrical Tomography for the Survey and 3D Representation of Caves: Case Study of the Cave of Kef El Baroud, Province of Benslimane, Morocco

The modeling of caves is constantly evolving and the classic modeling tools are giving way to new techniques that are more precise and more practical, indeed scientists are increasingly using 3D modeling to improve the representations of caves, in this study we have used lasergrammetry and photogrammetry which occupy an increasing place in the 3D representation of caves. Their simplicity favors their use for recording and modeling the parietal morphology of caves and the detailed representation of the complexity of Endokarst. As part of the geomorphological study of the Kef El Baroud Cave which is located in the province of Benslimane in Morocco, two modeling methods were carried out, it is a digital survey by lasergrammetry and by photogrammetry of the cave. and its parietal morphologies. The study was completed by a topographical survey with a DistoX rangefinder. The geophysical contribution by electrical tomography was also carried out. The 3D terrestrial laser scanning technique was performed by a LEICA RTC 345 scanner. These measurements made it possible to reconstruct the evolutionary stages of the paragenetic morphologies, and their relationships with the local geomorphology, and the structural elements. The field measurements were integrated into the morphometric analyzes of the digital models, which allowed a large number of observations.The surveys also made it possible to compare the results with those of the photogrammetry carried out by a reflex camera and a wide-angle lens with appropriate editing software.Lasergrammetry and its application have enabled us to precisely position within the point cloud all the details of the covered wall, and thus constitutes, alongside photogrammetry, an interesting means for the geomorphological study of the Caves. An electrical tomography study was coupled with the other measurements and made it possible not only to delimit the walls of the Cave according to the resistivity gradients but also to detect the very probable presence of fractured zones under the Cave which could constitute an aquifer.

Effect of temperature on pure mode Ⅲ fracture behavior and fracture morphology of granite after thermal shock

To investigate the effect of temperature on the pure mode III fracture behavior and fracture morphology of granite after thermal shock, edge-notched disc bend granite specimens are selected for heat treatment and a series of fracture tests. Firstly, the effect of temperature on the macroscopic fracture behavior of the rock is analyzed regarding the physical and mechanical properties and fracture toughness. Then, the impact of temperature on the microscopic fracture morphology of the rocks is discussed based on a fractal theory using 3D laser scanning techniques. The results show that temperature affects the fracture behavior of rock by changing its physical parameters and mechanical properties. High temperatures can change the fracture mode of rocks and have a softening effect on rocks. The heat treatment temperature of 325 °C above can convert rocks from brittle to ductile failure. When the heat treatment temperature is above 525 °C can evolve rocks from pure mode III fracture to mixed mode I/III fracture. The fracture toughness of the rock and the joint roughness coefficient are highly linearly correlated with temperature. The fracture toughness of the rock decreases by 0.5 MPa∙m0.5, and the joint roughness coefficient increases by 1.7 for every 100 °C increase in temperature in the range of 25 °C to 625 °C. The asperity height and slope angle of the rock obey a normal distribution. The higher the temperature, the larger the fracture surface area, the larger the fractal dimension, the stronger the anisotropy of the surface protrusions, and the rougher the rock surface.

Degradation of Steel Rebar Tensile Properties Affected by Longitudinal Non-Uniform Corrosion.

Rebar corrosion is the primary cause of the durability degradation of reinforced concrete (RC) structures, where non-uniform corrosion is the typical pattern in engineering. This study experimentally and numerically investigated the tensile degradation properties of non-uniform corroded rebars. Corrosion morphology was accurately determined by three-dimensional (3D) laser scanning techniques, studying the characteristics of longitudinal non-uniform corrosion. The results showed that the non-uniformity of corrosion increased with an increase in corrosion levels. From tensile tests, the differences in nominal stress-strain curves among rebars with similar average corrosion levels indicated that corrosion non-uniformity has appreciable effects on the tensile behavior of rebars. The residual load-bearing capacity of corroded rebars was dominated by the reduced critical cross-section, while residual ductility was associated with the cross-section loss throughout the entire length of rebars. The degradation relations of nominal yield and ultimate strength, ultimate strain, and elongation after fracture were better correlated to the maximum cross-section loss than to the average volume loss. Additionally, numerical calculation based on the cross-sectional areas of corroded rebars was conducted to evaluate the tensile behavior of non-uniform corroded rebars. Equivalent distribution models simulating the longitudinal non-uniform corrosion were proposed, on the basis of probability characteristics of cross-sectional areas, for practical application of the numerical method.

Method for visualizing the shear process of rock joints using 3D laser scanning and 3D printing techniques

This study presents a visualized approach for tracking joint surface morphology. Three-dimensional laser scanning (3DLS) and 3D printing (3DP) techniques are adopted to record progressive failure during rock joint shearing. The 3DP resin is used to create transparent specimens to reproduce the surface morphology of a natural joint precisely. The freezing method is employed to enhance the mechanical properties of the 3DP specimens to reproduce the properties of hard rock more accurately. A video camera containing a charge-coupled device (CCD) camera is utilized to record the evolution of damaged area of joint surface during the direct shear test. The optimal shooting distance and shooting angle are recommended to be 800 mm and 40°, respectively. The images captured by the CCD camera are corrected to quantitatively describe the damaged area on the joint surface. Verification indicates that this method can accurately describe the total sheared areas at different shear stages. These findings may contribute to elucidating the shear behavior of rock joints.

Ambient Vibration Testing and model updating of the bell tower of St. Michele Arcangelo Cathedral in Casertavecchia, Italy

The present study focuses on the dynamical characterisation of the bell tower adjacent to St. Michele Arcangelo Cathedral in Casertavecchia, Italy. The ancient tuff-masonry tower, which was built in the 13th century, is 32 meters high and presents Gothic influences, as it is clear from the large ogival arch supporting the first level. A geometrical model of the tower was created, based on an accurate survey realized by means of 3D laser scanning technique. Also, some physical tests were performed to investigate the materials constituting the tower. Once that preliminary information was acquired, Ambient Vibration Tests (AVTs) were performed by using tri-axial and bi-axial accelerometers. The recorded data allowed for the identification of the fundamental frequencies and mode shapes of the structure under consideration. Then, a Finite Element model was built in Code Aster software and a model updating process was performed to correctly reproduce the dynamical behaviour of the structure.

Statistical Estimation of Blast Fragmentation by Applying 3D Laser Scanning to Muck Pile

Run-of-mine fragmentation is an important aspect of mine productivity optimization, as it affects all mine-to-mill processes. The current blasting fragmentation calculation methods do not consider the 3D geometric information. Therefore, their calculation results are imprecise. 3D laser scanning is a technique for extracting the 3D geometric information of an object by constructing a 3D point cloud model, with which extra information on the geometrical characteristics of an object could be captured than with the technique of 2D image processing. In this paper, 3D laser scanning technology was utilized for the calculation of the rock blocks on the surface of a muck pile, and the information about the surface blocks was utilized as the samples for the statistical estimation of blasting fragmentation of muck pile (BFMP). Monte Carlo simulation was utilized as the statistical estimation method for the BFMP. In the lab experiment, results from 2D image processing technique and from 3D laser scanning technique combined with statistical estimate were compared with the physical measurements utilizing a water tank, which show that results with 3D laser scanning are more similar to the physical measurement. Finally, the applicability of 3D laser scanning technology combined with statistical methods to the calculation of blast fragmentation was estimated through field tests in Biesikuduke and Santanghu mine, two open-pit coal mines in Xinjiang Province of western China. Results show that the accuracy of the statistical estimation results of BFMP has a particle size deviation of 1–3 cm.

Effect of Leaching Behavior on the Geometric and Hydraulic Characteristics of Concrete Fracture.

The leaching of material from concrete fracture surfaces has an impact on the structural concrete in service, but the number of studies that consider the effect of the coupling of the leaching, fracture geometry and hydraulic processes on concrete fractures is insufficient. In this study, a series of experiments was conducted, and a leaching model proposed, to investigate the mechanism of leaching behavior on the geometric and hydraulic characteristics of concrete fractures. Following the leaching experiment, the evolution of fracture geometric characteristics was observed by a three-dimensional (3D) laser scanning technique, finding that the fracture produces residual leached depth and local uneven leaching, which results in a decrease in roughness. The hydraulic characteristics were then investigated by permeability tests, and it was found that the fracture hydraulic aperture and permeability increase monotonically with leaching time. A simulation of fluid flow in a numerical fracture revealed the effect of residual leached depth and a decrease in roughness on the hydraulic characteristics. Finally, based on the analysis of the chemical composition of the leaching solution, a leaching model of concrete rough fracture surface is proposed and the mechanism of leaching behavior is discussed. These new findings are useful for the understanding of the development of leaching, local to concrete fracture surfaces.

A Post-Scan Point Cloud Colorization Method for Cultural Heritage Documentation

The 3D laser scanning technique is important for cultural heritage documentation. The laser itself normally does not carry any color information, so it usually requires an embedded camera system to colorize the point cloud. However, when the embedded camera system fails to perform properly under some external interferences, a post-scan colorization method is always desired to improve the point cloud visuality. This paper presents a simple but efficient point cloud colorization method based on a point-to-pixel orthogonal projection under an assumption that the orthogonal and perspective projections can produce similar effects for a planar feature as long as the target-to-camera distance is relatively short (within several meters). This assumption was verified by a simulation experiment, and the results show that only approximately 5% of colorization error was found at a target-to-camera distance of 3 m. The method was further verified with two real datasets collected for the cultural heritage documentation. The results showed that the visuality of the point clouds for two giant historical buildings had been greatly improved after applying the proposed method.

BIM-based Facility Management Models for Existing Buildings

Building Information Modeling (BIM) is mainly used for the design and construction of new buildings. However, one of the main challenges facing BIM adoption for existing or old buildings constructed without consideration for their modeling is obtaining raw and accurate building data and converting it to the BIM model. Based on this challenge, this study develops a framework that uses different data capture techniques for existing buildings, then transforms this captured data into 3D BIM models through which it can improve its management processes as facilities during their service life. Specifically, 3D laser scanning techniques were used to capture indoor building data, while drones equipped with high-definition cameras (UAV) were used to capture outdoor building data such as geometric dimensions, material shapes, surfaces and various shapes. Then the captured data was converted into a high-resolution 3D model. This has been verified the accuracy of this engineering model by converting the two-dimensional engineering plans to three-dimensional through the well-known engineering design tools. Moreover, the 3D model has been integrated with the Web Based Building Management System (BMS) platform. This research framework helps in developing engineering facility management processes and modern digital transformation processes that aim at speeding up facility management during their service period using modern technologies. This study aims to develop current knowledge in the construction industry and facility management by reviewing a comprehensive understanding of how to use modern technologies to obtain various information to develop BIM models for existing and non-modeled buildings in order to exploit and integrate them with advanced facility management systems and platforms, which constitutes a major progress in this field allowing to save a lot of effort and money in the future.

Crushing behavior of recycled waste materials: Experimental analysis and DEM simulation

Sustainable usage of construction and demolition (C&D) wastes in pavement and railway structures has attracted attention globally. However, the high probability of C&D particle breakage can impact the performance of the material and calls for careful investigation and assessment. This study aims to investigate the particle shape effect on the breakage behavior of C&D aggregates under one-dimensional compression testing using the discrete element method (DEM). Crushable particles with realistic particle shapes were modeled by agglomerates of bonded sub-particles based on 3D laser scanning technique. The DEM model was calibrated and validated with a series of single-particle crushing experiments. Results of single crushing tests indicated that the particle shape had a considerable effect on the crushing strength of the tested materials. Comparable macro-mechanical results were observed between the DEM simulation of the one-dimensional compression test and the laboratory experiment. The results revealed that the proposed model is able to accurately capture the macro and micro-mechanical responses of the tested samples. The percentage of broken bonds, number of agglomerates and volumetric size distribution of recycled concrete aggregate (RCA) materials during compression is shown to be significantly affected by the particle shapes. A hyperbolic equation is furthermore proposed to capture the correlation between the dissipated energy and the volumetric breakage index.

An overview of 3D laser scanning techniques and application on digitization of historical structures

An overview of 3D laser scanning techniques and application on digitization of historical structures

Application of Replicas in the Measurement of the Wear of Forging Dies with Deep Hollows Using a Laser Scanner

Abstract This article discusses the possibilities of using replicas of the geometry of the tool shaping the product in the process of hot precision forging for the control of geometrical characteristics, with the use of the three-dimensional (3D) laser scanning technique. Two types of masses were selected for the studies and used to create replicas with similar parameters, with which a forging die with a deep working impression, applied in the process of forward extrusion, was filled. The obtained results demonstrated that, based on selected parameters characterizing the replicate masses and tests, it is possible to select the optimal mass for 3D scanning, due to the best mapping of the surface layer. With the proposed approach, it is possible to perform tests that do not damage forging dies with deep working impressions and to support the process by making decisions concerning the tools’ further operation through a reliable determination of their wear.

Application of 3D Scanning, Computer Simulations and Virtual Reality in the Redesigning Process of Selected Areas of Underground Transportation Routes in Coal Mining Industry

Nowadays designing of selected areas of mines underground workings can be effectively improved by the application of computer techniques: 3D scanning, computer simulations and Virtual Reality. This, in fact, would result in the more reliable design process, significantly reduced designing costs and efforts, and improvement of the mines staff’s safety. This scientific paper presents a method developed for redesigning of selected areas of mines underground workings in which auxiliary transport is carried out. The method combines 3D laser scanning technique with computer simulations carried out in a CAD/MBS system, in order to determine the location of potential collisions of the transported loads with the arch yielding support and the equipment. The obtained results, visualized using Virtual Reality, will form input data in the process of designing the selected area of the mines underground workings. Finally, an example of the application of the described method during transportation of big-size load is given.

Development of 3D environmental laser scanner using pinhole projection

Three-dimensional (3D) information of capturing and reconstructing an object existing in its environment is a big challenge. In this work, we discuss the 3D laser scanning techniques, which can obtain a high density of data points by an accurate and fast method. This work considers the previous developments in this area to propose a developed cost-effective system based on pinhole projection concept and commercial hardware components taking into account the current achieved accuracy. A laser line auto-scanning system was designed to perform close-range 3D reconstructions for home/office objects with high accuracy and resolution. The system changes the laser plane direction with a microcontroller to perform automatic scanning and obtain continuous laser strips for objects’ 3D reconstruction. The system parameters were calibrated with Matlab’s built-in camera calibration toolbox to find camera focal length and optical center constraints. The pinhole projection equation was defined to optimize the prototype rotating axis equation. The developed 3D environmental laser scanner with pinhole projection proved the system’s effectiveness on close-range stationary objects with high resolution and accuracy with a measurement error in the range (0.05–0.25) mm. The 3D point cloud processing of the Matlab computer vision toolbox has been employed to show the 3D object reconstruction and to perform the camera calibration, which improves efficiency and highly simplifies the calibration method. The calibration error is the main error source in the measurements, and the errors of the actual measurement are found to be influenced by several environmental parameters. The presented platform can be equipped with a system of lower power consumption, and compact smaller size

Determination of Joint Surface Roughness Based on 3D Statistical Morphology Characteristic

Roughness significantly affects the shear behavior of rock joints, which are widely encountered in geotechnical engineering. Since the existing calculation methods on the joint roughness coefficient (JRC) fail to obtain a sufficiently accurate value of JRC, a new determination method was proposed in this study, where the 3D laser scanning technique and self‐compiled Python code, as well as the statistical parameter methods, were applied. Then, the shear strength of jointed rock was evaluated via Barton′s model, and therefore, a comprehensive comparison between the calculating results and experimental results was executed. Ultimately, the influencing factors of roughness profile extraction on the accuracy of JRC value, such as the measuring point interval, profile number, and measuring direction, were investigated. The results show that (1) equipped with the 3D laser scanning technique, the roughness profiles can be accurately extracted via the self‐compiled Python code, (2) an excellent consistency of shear strength could be observed between the calculating value and experimental results, verifying the validity and accuracy of the proposed method, and (3) a smaller measuring point interval can produce a more accurate digital profile and more accurate JRC value. To a certain extent, the more the sample numbers of profiles, the smaller the value of JRC.

Discrete Particle Simulation of Gas-Solid Flow in Air-Blowing Seed Metering Device

In this paper, the gas and seed flow characters in the air-blowing seed metering device are investigated by using the coupled computational fluid dynamics and discrete element method (CFD-DEM) in three dimensions (3D). The method of establishing boundary model based on the computer-aided design (CAD) drawing, has been used to build the boundary model of seed metering device. The 3D laser scanning technique and multi-element method are adopted to establish the particle model. Through a combined numerical and experimental effort, using 3D CFD-DEM software, which is based on the in-house codes, the mechanisms governing the gas and solid dynamic behaviors in the seed metering device have been studied. The gas velocity field and the effect of different rotational speeds and air pressures on the seeding performance and particle velocity have been studied, similar agreements between numerical and experimental results are gained. This reveals that the 3D CFD-DEM model established is able to predict the performance of the air-blowing seed metering device. It can be used to design and optimize the air-blowing seed metering device and other similar agriculture devices.