Wall Cracks Research Articles

Understanding intrinsic healing process in cementitious cracks through modeling and experiments

This study aims to understand the intrinsic healing process along crack depth in cementitious materials with various physical and chemical parameters. A new, coupled transport-thermodynamics model was formulated to predict crack wall profile change with time due to healing. The model considers the time-dependent interaction among ions transport through crack depth, healing products precipitation along crack walls, and local alteration of crack transport properties. The model was validated by controlled experiments quantifying the 3D crack aperture field before and after healing. Using X-ray computed microtomography, scanning electron microscopy and chemical analysis, the experiments uncovered and quantified the non-homogenous healing ratios and chemical compositions along crack depth. Parametric studies further elucidated how different physical (crack width, geometry, flow rate) or chemical (unhydrated cement ratio, ion concentration) parameters affect the healing profile change with time. The results shed light on the intrinsic healing mechanisms and robustness in cementitious materials.

The Dynamic Image Analysis of Retaining Wall Crack Detection and Gap Hazard Evaluation Method with Deep Learning

This study uses machine vision combined with drones to detect cracks in retaining walls in mountaineering areas or forest roads. Using the drone’s pre-collected images of retaining walls, the gaps in the wall are obtained as the target for sample data. Deep learning is carried out with neural network architecture. After repeated training of the module, the characteristic conditions of the crack are extracted from the image to be tested. Then, the various characteristics of the gap feature are extracted through image conversion, and the factors are analyzed to evaluate the danger degree of the gap. This study proposes a series of gap danger factor equations for the gap to analyze the safety of the detected gap image so that the system can judge the image information collected by the drone to assist the user in evaluating the safety of the gap. At present, deep learning modules and gap hazard evaluation methods are used to make suggestions on gaps. The expansion of the database has effectively improved the efficiency of gap identification. The detection process is about 20–25 frames per second, and the processing time is about 0.04 s. During the capture process, there will still be a few misjudgments and improper circle selections. The misjudgment rate is between 2.1% and 2.6%.

Environmental Pressures at Dirre Sheikh Hussein Sanctuary

Dirre Sheikh Hussein is a religious complex in Ethiopia that dates from the 12th century or earlier. An important focus for pilgrimage, it lies in an isolated part of Oromia State on poorly drained semi-arid lowlands. Significant architecturally and culturally, recent expansion and refurbishment of the major buildings led to structural issues, though these are now largely overcome through consolidation of the prayer hall roof, laying a stone walkway, digging drainage ditches etc. Current deterioration of the buildings can be seen as: (i) fading of colours, (ii) cracks in walls, roofs, and festive places, (iii) deposits of sand around walls and (iv) staining and drainage marks on the white painted surfaces. Heavy falls of rain overwhelm drainage and overfill storage pools. Meteorological observations are infrequent locally, so those made some 70–100 km away were used, along with regridded historical data, reanalysis and CMIP6 projections. These revealed increases in temperature, precipitation and humidity, and provided indications of long-term climate pressures at the site. Changing patterns of future precipitation, particularly heavy rain, may threaten the site. The relative humidity changes are small, though an increasing Scheffer index suggests potentially enhanced wood decay. Changes in soil moisture have the potential to disrupt the foundations. Very hot days may become a problem for the two annual celebrations at the site.

Rhipicephalus sanguineus (Brown dog tick)

Rhipicephalus sanguineus sensu stricto (part of the R. sanguineus group) is a tick found mainly on dogs and occasionally on other hosts; for example, wild carnivores and hedgehogs are speculated to be the hosts for one or several stages of this tick. Previously thought to be distributed worldwide, current available evidence indicates that R. sanguineus s.s. is found predominantly in cold and temperate areas of the Americas (e.g., Argentina, southern Brazil, Chile, Uruguay, and the USA) and Europe (e.g., France, Italy, Spain, Portugal, and Switzerland). R. sanguineus s.s. has an endophilic behaviour and may be found inside houses, on wall cracks, and in furniture. It is known or suspected to act as a vector of pathogens to dogs (e.g., Babesia vogeli and Ehrlichia canis) and humans (e.g., Rickettsia conorii and Rickettsia rickettsii). Controlling tick infestations on dogs is pivotal to mitigate the direct effects of tick blood feeding and to reduce the risk of pathogen transmission to other dogs and humans.

Conservation Status Diagnosis of Mural Painting in Geungnakjeon Hall of Daewonsa Temple, Boseong: Avalokitesvara Bodhisattva Mural and Buddhist Monk Bodhidharma Mural

Investigation of conservation status, optical survey, infrared thermography, and ultrasonic examination were performed on Avalokitesvara Bodhisattva mural and Buddhist Monk Bodhidharma mural to determine the conservation status and physical properties. As a result of investigation of conservation status, the types of damage are largely divided into the wall and finishing layer damage, painting layer degradation, damage due to restoration materials, stains and contamination, and biological damage. As a result of the optical survey, drawing, stains, and repainted site were confirmed. Result of the infrared thermography, the delamination of the finishing layer was confirmed, and some locations and shapes of the wooden lath inside the wall were identified. The result of the 3D scanning, the deviation, and the separation of the wall was confirmed. As a result of ultrasonic examination, it was confirmed that the physical properties of the mural were identified and the ultrasonic speed was relatively low due to physical damage such as delamination and exfoliation of the finishing layer and cracking. Ultrasonic speed values were also high in some wall cracks or delamination, and it was confirmed by the infrared thermography results that the wooden lath inside the wall was located in those parts. It was possible to understand that the wooden lath inside the walls affects the ultrasonic speed during the ultrasonic examination. Therefore, management through periodic inspection of the relevant elements is necessary, and a countermeasure for damage that may occur in the future should be prepared along with intensive monitoring of the major damage identified in this diagnosis result.

The long-term impact of an Ecohealth intervention: Entomological data suggest the interruption of Chagas disease transmission in southeastern Guatemala

Triatoma dimidiata is the main vector of Chagas disease in southern Mexico, Central America and northern South America. As a native vector, it moves readily among domestic, peri‑domestic and sylvatic environments, making it difficult to control only using insecticide as this requires regular application, and re-infestation frequently occurs. Other social innovation alternatives such as those based on Ecohealth principles can be used to tackle the dynamics of the disease in an integral way. We asked whether an Ecohealth intervention, implemented beginning in 2001 in a highly infested village, 41.8%, in southeastern Guatemala, was sustainable in the long term. This intervention included initial insecticide treatments, followed by making low-cost house improvements to eliminate transmission risk factors such as repairing cracked walls, covering dirt floors with a cement-like substance and moving domestic animals outside. We assessed the long-term sustainability through entomological and house condition surveys, as well as an analysis of community satisfaction. We found over a 19-year period, infestation with T. dimidiata was reduced to 2.2% and maintained at a level below the level (8%) where vector transmission is unlikely. This long-term maintenance of low infestation coincided with a large proportion of villagers (88.6%) improving their houses and completing other aspects of the Ecohealth approach to maintain the village at low risk for Chagas transmission. There was unanimous satisfaction among the villagers with their houses, following improvements using the Ecohealth method, which likely played a role in the long-term persistence of the modifications. Although the infestation has remained low, 11 years following the last intervention and as the population grew there has been an increase in the proportion of “at-risk” houses, to 33%, pointing out the necessity of maintaining vigilance. The Ecohealth approach is a low-cost, sustainable approach for the long-term control of vector-borne Chagas disease. We recommend this approach including ongoing community monitoring and institutional response for the long-term, integrated control of Chagas disease.

Evaluation of the damage and reinforcement of the foundation in a ten-storey multi-purpose building in Port Harcourt, Rivers State, Nigeria

The research work examined the evaluation of the damage and reinforcement of the foundation in a ten-storey building in Rivers State. The following tests: deep boring test, standard penetration test, boreholes sampling, and crack monitoring by Demec gauge have been carried out to check all kinds of damages related to a strong connection with the ground since the behaviour of the ground determines the stability of the building foundation and the long-term performance of the building. Foundation failures have a major impact on the performance of the building structure. If the base is not stable and moves easily, distortion and deflection will occur. It causes damage to the structure, such as cracks in walls, beams, and floors, and becomes a problem for residents. This problem needs to be fixed and corrective work is the option to fix the error. The following recommendations were considered as follows; maintenance of the building and subsoil to avoid deformation and damage to the building structure at least every six months. Periodic on-site inspection is very important to determine if there is any damage to the building structure. The inspection can be carried out at least once every six months or once a year.

A cross-platform smart drone controller framework – for real-time surveillance and inspection

This can form the basis for strategic management of new Smart Cities that aim to reduce Line-of-Sight piloting overheads and automate surveillance task. In this paper, we propose an architectural design to support the needed capabilities and basic features of a Smart Drone Controller. framework. This prototype framework supports a deployed team of Wi-Fi drones to conduct assigned surveillance. SDC’s machine learning engine evaluated with Deep Learning algorithms to detect target accuracy from drones live video feed. We have used Darknet/YOLO model for custom object detection in Intruder drone and Wall crack detection use cases and accuracy is reaching over 80%, which is encouraging.

Evaluation on the progressive collapse resistance of infilled reinforced concrete frames based on numerical and semi-analytical methods

The effect of infill walls on the progressive collapse behaviour of reinforced concrete (RC) frames should be fully considered due to the formation of alternative load paths. To explore the configuration that could affect the progressive collapse resistance of infilled RC frames, parametric analyses are performed based on the validated simulation method. In the study, the impact introduced by the extra tie and integrity rebars in walls is emphasised. It is indicated that the variation in the reinforcement ratio of tie rebars leads to a limited change in structural progressive collapse resistance. In contrast, with the arrangement of the integrity reinforcement, the progressive collapse resistance of the infilled frames is enhanced and the propagation of the diagonal cracks in partial infill walls is suppressed. The notable re-ascending trend in the resistance curve for models with integrity rebars reveals the significant development of the catenary action in the integrity reinforcement. Then, with the help of linear regression and gene expression programming (GEP) techniques, a semi-analytical model is proposed for the prediction of the load-bearing capacity of infilled frames after column loss. In the prediction model, the linear effect of geometrical parameters and the non-linear effect of openings on the progressive collapse resistance are included by introducing three modification coefficients. Based on the statistical assessment, the capability of this explainable model is verified, and the appropriate amount of integrity reinforcement to mitigate the progressive collapse is discussed.

Severe Termite Infestation: Conservation of the EDSA Shrine Oil Mural Painting on Canvas

Severe termite infestation resulted in the loss of around 80% of the canvas in one of the four panels of the Philippine’s Epifanio De Los Santos Avenue (EDSA) Shrine’s oil mural painting mounted on plywood. Eight colonies of termites were discovered tunnelling through the cracks in the concrete walls coming from plant boxes outside the building. Initial work required eradication of the termites’ source and reduction of moisture from the exterior wall. Preparation of the interior wall behind the panels included waterproofing, polyester insulation and application of a lime-based plaster. Several layers of RK-0 tissue, Chiang-mai tissue, gauze and cheesecloth were used as facing prior to de-installation. Treatment of the damaged artwork followed the five basic steps, (1) cleaning, (2) chemical stabilisation, (3) physical stabilisation, (4) aesthetic unity and (5) protection with ultraviolet stable varnish. After cleaning the back of the painting eaten by termites, the paint layer soiled with frass, was swabbed with peroxide, flattened with tissue, brushed with cellulose fibre-reinforced plaster and relined with de-acidified canvas. The restored painting exhibited shrinkage in size with wrinkling of paint. In lieu of infested plywood, it was re-mounted on a stretcher and reinstalled with a spacer from the wall provided for ventilation.

Determination of Civil Engineering Problems Using Resistivity Methods in Ramadi, Western Iraq

Many civil engineering problems resulting from the presence of gypsum soil near the surface and the water table in shallow depth led to the solubility of the soil and creates a subsurface weak area in Ramadi city. 2D and 3D electrical resistivity imaging were applied using a Dipole-dipole array with an n-factor of 6 and a-spacing values of 2 m. Imaging data sets have been acquired along five traverses with a line distance of 4 meters. The inversion model is generated by the robust inversion model constraint method, which clearly shows that the boundary of the weak area is sharper and straighter. The results show the presence of two main zones, the first represents the topsoil layer which extends to a depth of 2.5 m with a resistivity ranging from 28 to 312 Ωm. The second zone is located at 2.5 m depth and extends to 10 m with a resistivity value ranging from 0.267 to 28 Ωm. The variation of the water table, inhomogeneity of the sediment, weak areas, and sedimentation lenses are the main reasons for the failure of civil engineering. These failures may cause many problems such as wall cracks, foundation damage, and building collapses.

Evaluation of precast beam deflections resulting in cracks in curtain walls

Cracks in brick walls are among the most common examples of failures in residential constructions. This article focuses on the occurrence of cracks in brick curtain walls based on precast beams, made in a non-standard large-panel system. In order to analyse this issue, test loads on natural scale beams were carried out on a specially prepared test stand. Numerical calculations were also performed for a beam in the modified system and for a popular beam-wall in the classic system. The obtained results confirm that the serviceability limit state in the form of deflection was exceeded. The cracking was caused by designing the elements according to archival, less restrictive norms and making them from materials with lower material characteristics in relation to currently used. In addition, the modified beam has a significantly smaller cross-sectional height, while carrying a higher load in relation to the commonly used beam-wall. The resulting defects need to be thoroughly assessed, and then a decision on the acceptability of further use and possible strengthening has to be made, preferably by an approved engineer.

Experimental Study on the Effects of Freeze–Thaw Cycles on Strength and Microstructure of Xining Region Loess in China

Loess, a collapsible soil, is widely distributed in the Qinghai–Tibet Plateau in China. In the meantime, loess is a sustainable and green building material that is widely used in traditional residential buildings. However, previous studies have focused on the properties of loess itself, ignoring the influence of climatic conditions on loess buildings, as well as a series of engineering problems such as soil spalling caused by freezing and thawing, cold cracks in walls, and settlement deformation of foundation. This research presents a series of laboratory tests on both undisturbed and remolded loess. The tests investigated changes in the unconfined compressive strength (UCS) of both types of loess after different freeze–thaw cycles. The freeze–thaw-induced changes to the internal structures of the loess were also investigated using a scanning electron microscope (SEM) and X-ray diffraction test (XRD). The test results showed that: (1) with increasing freeze–thaw cycles, the UCS of both the undisturbed and remolded loess appeared to first increase and then decrease, and the stress–strain curves showed a stronger strain-softening tendency. (2) The compressive strength of undisturbed loess is higher than remolded loess. (3) SEM analysis showed that the large particles inside the loess sample were gradually broken down into small particles, which led to an accumulative increase in fine particles and a decrease in the porosity. With the increase in the number of freeze–thaw cycles, the particles inside the soil become denser, and the strength increases. (4) Freezing and thawing have less effect on loess minerals. (5) The conclusion can provide a reference value for the protection of loess buildings in Qinghai and the management of freeze–thaw disasters.

Assesment of the temperature loading influence on crack resistance of a tank with a semi-eliptical crack

Reservoir parks are the main place of storage of petroleum products. There has been a tendency transition to the use of larger tanks in recent years, which is economically justified. However, it is leads to fire risk increase to accumulate large quantities of petroleum products. Tank fire is one of the most dangerous emergency event, which can lead not only to significant material damage but also to ecological human losses in case of spreading of fire to other tanks. To ensure safety and test the bearing capacity in these conditions determination of the stress-strain state in such tanks must be performed taking into account the temperature load. If there is an initial crack in the tank wall the assessment of crack resistance should be performed. In a previous work the authors determined the stress intensity factor (SIF) distribution along the semi-elliptical crack front in the RVS-5000 tank under hydrostatic pressure. The estimation of a stress-strain state of a steel vertical tank with an initial semi-elliptical crack under the thermal loading is performed in this article. It is suppoused that the part of wall of the tank, located closest to the fire epicenter, is heated unevenly in height: from 300 degrees at the top to 200 degrees at the bottom. On the other part of the tank the temperature reaches 70 degrees. The temperature within wall thickness is considered constant. Given the asymmetric nature of the temperature distribution, a discrete model was developed for the entire tank. After determining the stress-strained state in the whole tank under hydrostatic pressure and temperature load, a fragment with a semi-elliptical crack was calculated separately. The stresses determined from the calculation of the whole tank are used like an external load, applied on fragment boundaries. The difference of results of direct and energetic method of SIF calculation are in the range of 5%. Taking into account the temperature loading leads to an increase in the SIF values by about 20 % in comparison to the results of the calculation only under hydrostatic pressure.

On the hydraulics of flow in cracks in embankment dam cores

A major hazard to embankment dams is internal erosion and piping arising from concentrated leaks through transverse cracks in the core near the crest due to differential settlement or desiccation. This contribution summarises experiments and a formal boundary layer analysis of flow through such transverse cracks subject to near-horizontal pressure gradients. The critical hydraulic gradients, at which erosion in such cracks may initiate, occur at the downstream end of the crack. This location and the maximum crack width defines the local point most vulnerable to erosion. The hydraulic laboratory measurements are shown to be consistent with equivalent international standards describing depths at free overflows, in spite of the narrow vertical profile of the cracks, provided that the tendency towards laminar flow in very narrow cracks is incorporated within the modelling. A backwater model based on conventional representations of flow in narrow channels is verified qualitatively by hydraulic laboratory data. Flow-depth relationships, maximum crack wall hydraulic stresses, normalised hydraulic wall stress profiles and depth profiles along cracks are presented for the two principal crack geometries present in embankment dams. These characterisations are a significant improvement on the simplified methods previously used to assess internal erosion in transverse cracks in dams.

Characteristics of Resistive PM Sensors for Onboard Diagnostics of Diesel Particulate Filter Failure.

In accordance with the recently reinforced exhaust regulations and onboard diagnostics regulations, it is essential to adopt diesel particulate filter systems in diesel vehicles; a sensor that directly measures particulate matter (PM) in exhaust gas is installed to precisely monitor diesel particulate filter (DPF) failure. Because the reduction of particulate matter in the diesel particulate filter system is greatly influenced by the physical wall structure of the substrate, the presence or absence of damage to the substrate wall (cracks or local melting, etc.) determines the reliability of normal DPF operation. Therefore, an onboard diagnostics sensor for particle matter is being developed with a focus on monitoring damage to the DPF wall. In this study, as a sensor for determining damage to the substrate wall, an accumulation-type sensor whose resistance changes as soot particles are deposited between two electrodes was fabricated. The sensor characteristics were investigated by changing the gap between the sensor electrodes, sensor cap shape, and electrode bias voltage to improve resistive soot sensor sensitivity and response. From the signal characteristics of various sensor configurations, a combination sensor with improved signal stability and response time is manufactured, and they were compared with the characteristics of commercially available sensors in the engine-simulated NEDC mode in terms of the degree of DPF crack. As a result of transient mode, PM monitoring cycle was improved by 1.2~1.5 times during the same vehicle driving time compared to the existing commercial sensor.

Structural considerations to minimise the risk of horizontal cracks in the wall of circular concrete tanks

The inspection of on-ground circular concrete tanks by the authors has shown that the formation of horizontal cracks in tank walls is a common serviceability issue in Australia. These cracks often lead to leakage or durability-related issues that impact the service life of tanks. In this research, a harmonised design approach is provided for designers to consider the contribution of different parameters such as liquid pressure and volumetric changes of concrete, autogenous shrinkage, solar, seasonal and thermal process loads to the serviceability design. A practical model has been developed to predict the vertical serviceability bending moments and the width of horizontal cracks in the wall of tanks without the need to perform complex Finite Element (FE) modelling. This model has been developed by establishing a mathematical correlation between the design inputs and results of FE analysis of 320 tanks. In addition, risk factors in the formation of horizontal cracks on the internal and external faces of tanks were investigated, and recommendations for minimising the risk of horizontal cracks are provided.

Effect of Leak Geometry on Water Characteristics Inside Pipes

Water leaks from pipelines have large economic and ecological impacts. Minimizing water loss from supply pipelines has favorable effects on the environment as well as on energy consumption. This paper aims to understand the effect of the geometry of a leaking crack in a pipe wall by examining fluid flow characteristics, namely pressure and velocity distributions, inside the pipe. Practical observations show that the cause of wall rupture influences the geometry of cracks formed in a pipe wall, impacting aspects such as excessive pressure, corrosion. Knowledge of fluid flow characteristics could help in detecting and identifying leak characteristics at an early stage and assist in improving the energy and resource efficiency of water supply services. An experimental setup is developed to detect water leakage in a pipe when the leak is at an early stage and is difficult to detect by visual inspection. A computational fluid dynamic (CFD) model is developed using the COMSOL software. A comprehensive analysis of the effect of leak geometry on pressure and velocity distributions along the pipe is carried out while considering factors such as different pipe sizes, leak geometries, and steady-state flow conditions. It is observed that both velocity and pressure magnitudes rapidly fluctuate in the vicinity of leaks. Leaking cracks with slot, circle, and square shapes are found to generate distinguishing pressure and velocity distributions along the pipe. Thus, the geometry of the leaking crack and potentially its root cause(s) could be predicted by measuring velocity and pressure distributions.

Use of recycled concrete aggregates as carriers for self-healing of concrete cracks by bacteria with high urease activity

Microbial induced carbonate precipitation (MICP) has become one of the most attractive strategies to achieve self-healing of concrete cracks in recent decades. In order to provide a moderate space for bacteria in the harsh environment of concrete, the incorporation of protective carriers is a necessity. In this study, the microbial urease activity at different generation of propagation in the selected culture medium was first investigated, followed by exploring the potential of using recycled concrete aggregates (RCAs) as microbial carriers, considering the porous nature of RCAs. The specific urease activity of bacteria at 48 h kept as high as 2.4 × 10−8 mM·min−1·cells−1 even after 5 generations of propagation in the selected culturing medium. RCAs would not result in a loss of ureolytic activity after immobilization and were capable of retaining bacterial viability during concrete mixing. Compared with concrete without any healing agents or with only substrates and calcium source, the one with bio-agents loaded in RCAs completed most of the crack healing in the first week. When the initial crack widths were less than 0.6 mm, the average crack healing ratio and the crack area healing ratio were 71% and 84%, respectively, for microbial self-healing. The depth of crack healing was 17.8 mm as indicated by the microbial precipitates on the crack wall. After microbial self-healing, the compressive strength regain ratio achieved 99.7% while the water tightness regain ratio attained 99.2%, and the cracks were filled with densely packed irregular rhombohedral-shaped crystals consisting of calcite and a small amount of vaterite.

Generalized multifrequency fusion algorithm for defect detection in eddy current inspection data

This paper introduces a novel generalized multifrequency fusion method for defect detection in Eddy Current NDE. The proposed technique provides an ability to highlight small defect signals in presence of noise or larger signals from structural irregularities. This paper contains a complete mathematical formulation of the method and its applications to simulated and experimental data arising from two typical ECT problems: detection of the small cracks in the tube wall near tube support region of steam generator tubes, and detection of small cracks in the bottom layer of two-layer aluminum panels riveted with steel fasteners.