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Erosion Model for Wind-Blown Sand Flow at Earthen Sites in Arid Environment, Northwest China

ABSTRACT This study investigates the erosive impact of wind-blown sand on earthen sites within arid environments through the establishment of meteorological observation equipment. Over a span of 47 months, a comprehensive approach encompassing numerical simulation, plume analysis, particle examination, three-dimensional scanning, and photo monitoring was employed to continuously monitor the patterns of wind-blown sand movement and the degradation of test walls. The study identifies six distinct zones extending from five times the windward side to ten times the leeward side of the test wall’s height. Notably, a negative correlation between captured particle mass and the height of the sand traps is observed, with 70% of particles concentrated within 50 cm from the base of the test wall. Three primary erosion mechanisms for wind-blown sand are elucidated, including frontal impact, side abrasion, and reverse sapping. Furthermore, the study highlights pronounced erosion at the base of the wall due to vortex flow, with depth erosion affecting the lower, side, and upper sections of the test walls. This paper delves into the erosion mechanisms and operational models of wind-blown sand flow surrounding discontinuous site walls, offering valuable insights for the conservation of ancient earthen sites.

Compressive Creep and Ultrasonic Characterization of Adobe Bricks Stabilized with Quicklime, Portland Cement, and Date Palm Fibers

ABSTRACT As ecological architecture and green buildings have become essential in the fight against climate change, earthen architecture has an undoubted role to play in achieving this goal because of its numerous benefits. To help providing a better understanding of the behavior of earthen materials to fulfill modern architectural needs and to preserve earthen heritages, this study aims to investigate the effect of stabilization using Portland cement and quicklime and that of reinforcement using date palm fibers on the compressive creep, ultrasonic properties, and swelling of adobes, besides their impacts on physical characteristics. One of the earthen heritages in Algeria is taken as a case study, and various adobe mixes were examined to attain this objective. The outcomes revealed that stabilization overall improved the properties of adobes, unlike the mutable impact of fibers. Stabilizers played an important role in reducing creep, while fibers reduced the creep of the unstabilized adobes and those with 6%PC-3%QL, but withdrew the positive effect that was offered by binders for adobes with 10%QL and 3%PC-6%QL. Water absorption and swelling were reduced by stabilization, but both increased with the presence of fibers. The changes in ultrasonic characteristics showed a good correlation with those of compressive strength.

Proof of Concept for Methodological Framework Including Point Clouds in the Non-Destructive Diagnosis of Historical Masonry Structures

ABSTRACT The diagnosis of cultural heritage structures is a challenging and delicate task. It involves the evaluation of potential pathological situations, the understanding of the origin of displacements and deformations, and the assessment of the state of conservation of building materials. Destructive and minor destructive techniques are mostly prevented from being used in the context of historical constructions and the complementary use of non-destructive techniques is often the only viable solution. This paper addresses the possibility of employing point clouds, widely used for representation aims, as a source of information to identify the deterioration patterns that can affect construction safety. The proposed methodology includes two approaches following a perspective based on simple and recurring elements that form the complex and unique shape of historical buildings. The geometry of structural elements guides the choice towards the computation either of the Z-coordinate of each point of the cloud or the Euclidean distance between the point cloud and an elementary non-deformed geometry fitted to it. By investigating several case studies and diverse deterioration patterns, the proposal establishes a framework to employ point clouds, together with other techniques, as an effective tool to support the diagnosis of heritage structures.

Deep Learning for the Segmentation of Large-Scale Surveys of Historic Masonry: A New Tool for Building Archaeology Applied at the Basilica of St Anthony in Padua

ABSTRACT In the last decade, the documentation of historical buildings has made tremendous progress in generalising the use of high-precision laser scanning and drone photogrammetry. Yet the potential of digital surveying is not fully exploited due to difficulties in manually analysing large amounts of collected data. Machine learning offers immense potential as a game-changer in building archaeology, especially for the documentation of structures composed of millions of units. This paper presents the first segmentation of large-scale surveys of historic masonry using machine learning, using the thirteenth-century Basilica of St Anthony (Padua, Italy) as a case study. Based on a drone survey of the north façade of the building (110 × 70 m), a state-of-the-art non-learning segmentation approach is described and its limitations for historical structures are illustrated. Then, a new workflow based on convolutional neural networks (CNN) is presented. The result is a precise mapping of about 300,000 individual bricks showing a large variety of formats and bonds. The automatic surveys are analysed using visual programming language (VPL), enabling a rapid and feature-based identification of building phases and repair interventions. The outcome demonstrates the validity of machine learning for the analysis of historical structures and its potential in the field of heritage.

Open Access
Moment-Rotation Calculation Method and Parameter Analysis for Loose Continuous-Tenon Joint in Column-And-Tie Timber Structure

ABSTRACT To quantitatively calculate the moment-rotation relationship of loose continuous-tenon joints in traditional column-and-tie timber frame, the rotational deformation of loose joints is divided into two stages: free sliding and contact compression. Using constitutive, geometric, and equilibrium equations, a theoretical formula for moment-rotation is derived. The calculated values are then compared with experimental results to validate the accuracy of the theoretical calculation method. A sensitivity analysis is conducted on typical parameters, such as beam height, column diameter, joint clearance, and perpendicular compression modulus of wood, to explore their effects on the moment-rotation relationship of tenon joints. The results show that increasing the perpendicular compression modulus of wood leads to greater bending stiffness and load carrying capacity of tenon joints, with the latter increasing more significantly. In the elastic stage, the rotational stiffness of the joint increases with beam height or column diameter, while after entering the elastoplastic stage, the joint stiffness is less influenced by these factors. The initial rotational stiffness and load carrying capacity of the joint both decrease with joint clearance, and the effect of joint clearance on load carrying capacity decreases as the clearance increases when the joint enters the yielding stage.

Experimental Investigation on Comprehensive Performance of Natural Hydraulic Lime-Based Mortars: Effect of Waterproof Admixtures Addition

ABSTRACT In this study, the bulk modification method via incorporating two different types of waterproof admixtures was adopted to make natural hydraulic lime-based mortars more durable. The influence of two admixtures and their dosages on the hydration, physical, mechanical, and aggressive environment resistance properties were evaluated. The correlations between pore and water absorption characteristics, between hydration, pore characteristics, and mechanical strength were interpreted. Results showed that two waterproof admixtures changed the microscopic reaction between different components as well as internal structure of NHL-based mortar. Introduction of silane impregnant improved the workability of natural hydraulic lime-based mortars, and the appropriate dosage of silane impregnant facilitated hydration and improved mechanical strength at 28 and 90 days. Silane impregnant modified mortars were no more hydrophilic, acid resistance was improved while water absorption characteristics were not obviously improved even resulting in degraded freeze-thaw cycle resistance. Introduction of silicon-acrylic latex deteriorated the workability and retarded hydration of natural hydraulic lime-based mortars, regardless of dosage, leading to the degradation of mechanical strength. However, water absorption characteristics and freeze-thaw cycle and acid resistance can get a noticeable improvement when appropriate dosage was adopted.