External Corners Research Articles

The Jajarkot Earthquake: Revealed the Vulnerability of Load Bearing Structures in Western Nepal

The Jajarkot Earthquake, which occurred on 3rd November, 2023 of magnitude 5.7 (Mw) exposed Nepal’s longstanding vulnerability to seismic activity. This paper presents damage assessments derived from both on-site field observations and secondary resources to evaluate the damages sustained by load bearing masonry structures. In the region, 95% of the building structures are based on masonry construction. The damage status of structures in Jajarkot and Rukum East highlighted that about 50% of the building structures were partially and complete damage. The evaluation encompassed various aspects, including the types, mechanisms, and underlying causes of the damage incurred by structures. The observed damage was categorized using an established catalogue originally developed for the identification of failure mechanisms and vulnerability assessment. The common types of damage encompassed features like cracks in the load bearing external walls and corners, diagonal cracks originating from door and window corners, vertical out-of-plane displacement of external walls, collapse of external walls, and partial collapse of load bearing internal walls, fracturing of window and door lintels and complete collapse of structure. Some special forms of damage which was of new nature and distinct from those observed in prior seismic events such as the Gorkha earthquake included ruptures in the outer surfaces of loadbearing external walls, partial roof structure collapses, out-of-plane fragmentation or disintegration as well as rupture. The causes underlying this general damage were attributed to irregular bonding systems, weak mortar, stone block formation, size of stone blocks, absence of tie beams, weakly connected corners, insufficient connections of wall-roof and wall-floor systems, and differing internal wall systems. The mechanisms of damage varied based on the number and specifics of these causative factors, as well as certain structural attributes.

Fusion of Multiple Basic Element Features for Airborne LiDAR in-house Surveys

When using airborne LiDAR point clouds for city modelling and road extraction, point cloud classification is a crucial step. There are numerous ways for classifying point clouds, but there are still issues like redundant multi-dimensional feature vector data and poor point cloud classification in intricate situations. A point cloud classification method built on the fusing of multikernel feature vectors is suggested as a solution to these issues. The technique employs random forest to classify point cloud data by merging colour information, and it extracts feature vectors based on point primitives and object primitives, respectively. In this study, a densely populated area was chosen as the study area. Light airborne LIDAR mounted on a delta wing was used to collect point cloud data at a low altitude (170 m) over a dense cross-course. The point cloud data were then combined, corrected, and enhanced with texture data, and the houses were vectorized on the point cloud. The accuracy of the results was then assessed. With a median inaccuracy of 4.8 cm and a point cloud data collection rate of 83.3%, using airborne LIDAR to measure house corners can significantly lighten the labour associated with external house corner measurements.This test extracts the texture information of point cloud data through the efficient processing of high-density point cloud data, providing a reference for the application of texture information of airborne LIDAR data and a clear understanding of its accuracy.

Features of modeling the heat transfer through the external corner

Features of modeling the heat transfer through the external corner

Hygrothermal performance of corners and floor junctions of timber-framed exterior walls: a simulation study

Corners and basement junctions of different timber-framed walls were studied by computer simulation using Delphin 5.8.3 software. Wooden cladding and brick veneer were compared with each other, as well as different wind barrier solutions. Both internal and external corners were studied, first assuming them airtight and then modelling an air leak. Simulations were performed both in present and future climate conditions. According to the results, the walls with wooden cladding and brick veneer had a big difference in their hygrothermal behaviour. Mould index rose considerably after construction in sole plate of brick clad wall, even if the plate was originally dry. Wet sole plates dried up very slowly. Almost all corner junctions of walls with wooden cladding performed well when there was no air leak. Corners of brick clad walls were more problematic. With an air leak, all studied walls developed considerably high mould indices, underlining the importance of building airtightness.

Thermal protection improvement of building envelope near external corner (Tomsk)

The problem of energy saving is relevant nowadays. Great attention is especially paid to improving the energy efficiency of different building envelopes, since the heat consumption is a significant part of total costs for utility needs. Purpose: The aim of the paper is to study the state of the building envelopes nearby the outer corner. Research findings: Methods of reduction of the negative impact of the thermal bypass nearby the corner manifest themselves in condensation, mold, and subsequently lead to the envelope destruction. The use of insulated bevel edge leads to better results than that without insulation. But the minimum dew point temperature remains at corners and does not exceed 13.5 °C. Only in this case, the minimum dew point temperature moves to bevel edges. Value: The thermal bypass (outer corner) effect on the temperature field of its inner surface is studied. Three wall thicknesses are investigated: 510, 640, and 770 mm. It is shown that in all cases the corner temperature decreases below the dew point temperature.

Racehorse welfare across a training season.

Racehorse welfare is gaining increasing public attention, however scientific evidence in this area is lacking. In order to develop a better understanding of racehorse welfare, it must be measured and monitored. This is the first study to assess racehorse welfare using scientific objective methods across a training season. The aim of this study was threefold, firstly to investigate welfare measures which could be used in the first welfare assessment protocol for racehorses. Secondly, to understand the effect that a racing and training season had on individual racehorses and thirdly to identify risk factors for both good and poor welfare. Thirteen racehorse training yards were visited at the beginning and the peak of the racing season in England. Behavioral observations along with individual environmental and animal-based welfare measures were carried out on 353 horses in 13 training yards selected for variability. In our sample the horses were generally in good physical health: 94% of horses recorded as an ideal body condition score, no horses had signs of hoof neglect and 77.7% had no nasal discharge. The overall prevalence of external Mouth Corner Lesions was 12.9% and was significantly higher for Flat racing than Jump racing horses. The majority of horses (67.5%) showed positive horse human interactions. When stabled 54.1% horses had physical social contact and nasal discharge was not associated with increased physical contact. The training season significantly affected Human Reactivity Tests, Horse Grimace Scale scores and time spent resting and feeding. A total of 14.5% of horses displayed stereotypic behavior on at least two occasions. Horses with windows in their stables spent more time surveying their surroundings. Overall, in this population of racehorses, horses spent around a third of their daytime feeding (33.7%) followed by time spent standing resting (22.6%). The welfare assessment protocol used in this study is suitable for use in industry to collect welfare data on racehorses.

Calculation of active earth pressure on external corners with equal length on both sides in excavation engineering

Taking the external corner with equal lengths as the research object, two failure modes of the equilateral external corner are established, and the active earth pressure calculation formula of the equilateral external corner in the limit state is further deduced when the external angle is 90°. The comparison between the theoretical calculation results and Midas/GTS simulation results shows that when the ratio of the side length B to the depth H is large, the sliding wedge failure will occur at the external corner, and the active earth pressure of the external corner in the range of wedge-shaped slider will not change with the change of size B. When the ratio of the side length B to the depth H is small, the displaced soil is composed of two parts, and the earth pressure varies with the change of size B. In this paper, the magnitude and distribution law of the active earth pressure obtained by the horizontal micro-layered limit equilibrium analysis method is similar to the three-dimensional simulation value of the Midas/GTS software, which can prove the feasibility and rationality of the theoretical calculation.

Strategies of Heating and Hardening External Corners on the Example of Bending Tools for Press Brakes

Strategies of Heating and Hardening External Corners on the Example of Bending Tools for Press Brakes

Unified Simplified Capacity Model for Beam-Column Joints into RC Moment Resisting Frame

Seismic vulnerability of reinforced concrete (RC) buildings is strongly influenced by beam-column joints. Horizontal and vertical structural members converge in beam-column joints, as extremely delimited areas where the internal forces in concrete core and reinforcing bars have elevated stress gradients. In order to fully understand the seismic behavior of RC buildings and the related failures of T- and X-shaped beam-column joints (external corner and internal-positioned), an analytical model of RC joint behavior is proposed in a unified and simplified way. The equilibrium equations of cracked joint portions allow the assessment of internal stresses’ evolution at increasing values of column shear forces. In this way, the strength hierarchy is evaluated in terms of capacity for the different potential failure modes. This can drive, as a useful tool for designers, the design of new efficient structures or the assessment of existing ones to occur, with subsequent interventions to move an initial undesired failure mode to a more suitable one. Nearly 500 experimental results of tests available in the literature are compared with the analytical predictions of the proposed model.

Effect of freeze–thaw cycles on deformation properties of deep foundation pit supported by pile-anchor in Harbin

Abstract In the course of the construction of deep foundation pits during the winter in seasonally frozen areas, the pit wall soil is often unstable due to frost heave and thawing settlement, which leads to hidden safety hazards in engineering construction. Based on the analysis of the deformation data of a pile-anchor supporting a deep foundation pit in Harbin obtained from monitoring during the winter, the influence of freezing and thawing cycles was investigated. The results show that the horizontal displacement in the middle of the shallow layer of the foundation pit is significantly larger than that on both sides during the freeze–thaw cycles, and the spatial effect becomes noticeable. The stress concentration at the external corner of the foundation pit, coupled with the effects of atmospheric precipitation and freeze–thaw cycles, led to the maximum growth rate of horizontal displacement up to 1.40 mm·day−1. The external corner effect is evident from 1 m in the shallow layer of the pit to the depth H/2 of the foundation pit. The support scheme is generally feasible, and we can appropriately enhance the support of the shallow layer of the foundation pit during the freeze–thaw cycles. For similar projects experiencing freeze–thaw cycles, the safety reserve can be appropriately enhanced when carrying out support design.

Tracking consolidation of out-of-autoclave prepreg corners using pressure sensors

A total of eight corner pieces with the four different thickness-to-radius ratio, one set using external and one set using internal tooling, were made to identify how unidirectional carbon-epoxy prepreg layers consolidate during lay-up and oven vacuum bag moulding. Flexible thin-film pressure sensors were introduced to both internal and external corner mould surfaces and pressure measurements were taken during hand lay-up. A second sensor was added to monitor how the pressure gradient changes during oven vacuum bag moulding. Time-lapsed pressure measurements found that the geometry-induced excess pressure on the external corners decreases during moulding, leading to some corner thinning but this effect is small. Meanwhile, internal corner parts saw significant ply-bridging in high thickness-to-radius conditions that could not be resolved during consolidation, resulting in corner thickening and voids. The flexible sensors are a viable option for in-situ pressure monitoring for potential meso-structural defects during composite product development or manufacture.

Turbulent flows along a streamwise external corner

A numerical investigation of turbulent flows in straight pipes with a cross-section in the form of a circular sector at different values of the apex angle${\alpha }$is carried out. Main attention is paid to the cases${\alpha }>{\rm \pi}$when the cross-section boundary contains a convex external corner. An analytical solution to the problem of laminar flow in the geometry under consideration is given. The law of resistance is determined, and velocity distributions over the pipe cross-section are obtained. The singularity of wall shear stress$\tau _w\sim r^{{\rm \pi} /{\alpha }-1}$at${\alpha }>{\rm \pi}$is shown which persists in turbulent flows as well. Turbulent flows are simulated at$Re=2000$and four apex-angle values${\alpha }=5{\rm \pi} /4$,$3{\rm \pi} /2$,$7{\rm \pi} /4$and$2{\rm \pi}$, as well as at a larger$Re=4000$and${\alpha }=3{\rm \pi} /2$. The characteristic features of the mean-velocity distributions are outlined, and their relationship with secondary flows is shown. The velocity of the secondary flow in the vicinity of the external corner reaches the value$6.3\,\%$of the bulk flow velocity at the maximum${\alpha }=2{\rm \pi}$. A characteristic feature of the considered flows is the presence of intense transverse velocity fluctuations in the region above the apex corner. It is hypothesized that the cause of these fluctuations may be the linear instability of the mean flow field. The studies of linear stability confirm this hypothesis. Considerable attention is paid to the study of secondary flows in the vicinity of the external corner. In general, the formation of these flows fits into the scheme proposed earlier (Nikitin,J. Fluid Mech., vol. 917, 2021, A24; Nikitinet al.,Fluid Dyn., vol. 56, issue 4, 2021, pp. 513–538), according to which the main mechanism is the centrifugal force arising from the fluctuating flow over the corner in the transverse plane. It is shown that the shape of secondary flows is reproduced to a certain extent by the vortical part of the Reynolds-stress force field. The latter may be found from the Helmholtz decomposition. The features of the mean pressure distribution associated with the secondary flow and with the presence of a region of concentrated fluctuations above the external corner are explained.

Systematics of Neotropical electric knifefish Tembeassu (Gymnotiformes, Apteronotidae)

A new species of the poorly known and critically endangered ghost knifefish Tembeassu is described from the upper Paraná and Araguari rivers, Brazil, using external anatomy and X-ray microcomputed tomography (µCT scan). Tembeassu titanicus sp. nov. is distinguished from its sole congener, T. marauna, by a unique set of morphometric and meristic characters, in addition to the absence of a tooth patch at the anterior portion of the roof of the oral cavity and the external corner of the mouth slightly passing the vertical through the posterior margin of the posterior nare. To test the monophyly of Tembeassu and reassess its phylogenetic position, a total-evidence approach was performed through a Bayesian inference (BI) and maximum-parsimony analysis (MP). Our results indicate that Tembeassu is monophyletic and the sister taxon of a clade formed by Apteronotus s.s., Megadontognathus, and Parapteronotus (BI); or as part of a large polytomy at the base of Apteronotidae (MP). Species of Tembeassu co-occur in the Paraná River basin, and the absence of the patch of accessory teeth in T. titanicus sp. nov. may indicate that this species accesses a different food resource, and also putatively occupies a different habitat than T. marauna. Comments on the evolution of the mandibular lobe in Gymnotiformes, dentition pattern in Tembeassu, and apteronotid diversity in the Paraná River are provided. http://zoobank.org/urn:lsid:zoobank.org:act:691CB9A5-5CDB-4BF9-8A6FEAE877563C12

Peri-zygomatic infection associated with zygomatic implants: Aretrospective longitudinal cohort study.

The main objective of this retrospective, longitudinal, cohort study was to describe the occurrence of peri-zygomatic infection (PZI) as a complication associated with zygomatic implant (ZI) placement in a period of 22years. A retrospective search was carried out in the department of oral and maxillofacial surgery of Saint John's hospital in Genk, Belgium. Patients that had a severely atrophic fully or partially edentulous maxilla, and at least one ZI placed, were included. A total of 302 eligible patients, underwent ZI surgery between 1998 and 2020. From a total of 940 ZI, 45 were associated with the development of PZI. PZI was located in the upper portion of the cheek in relation to the external corner of the eye, one or two centimeters under the lower lid. The total number of affected patients was 25 (8.3%), who had a mean age of 58.1years. In this subset, PZI occurred in 15 cases on the right side, in eight cases on the left side, and in two cases bilaterally. Ultimately, 16 ZI were lost in the PZI site. The mean time since the implant placement to the diagnosis of PZI was 1.9years (SD ±2.4) and to the ZI removal of 3.8years (SD ±3.7). After implant removal, the PZI symptomatology dissipated in all patients. Peri-zygomatic infection should be informed to the patients as a possible complication after ZI placement. Once identified, it should be acknowledged as a risk factor for ZI failure.

Tool interface pressure during the forming of model composite corners

A new experimental technique is proposed to measure the pressure gradient in corner laminates with the aim of guiding manufacturing practices that can produce composites laminates to the desired thickness. A pressure mapping sensor was placed between a metal mould tool and a silicone sheet that acts as an idealised composite part. The compaction pressure loss in internal corners and rise in external corners is reported for the first time, covering a part thickness to radius ratio of 0.2 to 0.8 in the corner. A conclusive trend was observed in internal corners, where the pressure drop increases proportionally with the thickness to radius ratio. The sensor thickness, bulk, and contact with the tool created difficulties in measuring the true extent of the pressure rise for external corners. Stretchable thin film sensors might provide better alternatives for future studies looking to investigate pressure gradients in doubly curved geometries.

Seismic performance improvement of RC buildings with external steel frames

In this study, in order to improve the seismic performance of existing reinforced concrete (RC) framed structures, various external attachment of corner steel frame configurations was considered as a user-friendly retrofitting method. The external steel frame is designed to contribute to the lateral stiffness and load carrying capacity of the existing RC structure. A six story building was taken into account. Four different external corner steel frame configurations were suggested in order to strengthen the building. The 3D models of the building with suggested retrofitting steel frames were developed within ABAQUS environment using solid finite elements and analyzed under horizontal loadings nonlinearly. Horizontal top displacement vs loading curves were obtained to determine the overall performance of the building. Contributions of steel and RC frames to the carried loads were computed individually. Load/capacity ratios for the ground floor columns were presented. In the study, 3D rendered images of the building with the suggested retrofits are created to better visualize the real effect of the retrofit on the final appearance of the facade of the building. The analysis results have shown that the proposed external steel frame retrofit configurations increased the lateral load carrying capacity and lateral stiffness and can be used to improve the seismic performance of RC framed buildings.

Building wall corner structures, its microclimate and seismic resistance

Widespread low-rise residential buildings with a seismically resistant concrete frame and brick infill walls have lower microclimate levels in cold seasons due to low temperatures on the inner wall corner surfaces.These temperatures are lower if there is a corner column. For Bishkek, this temperature is 4.6 °C lower than that for permissible microclimate, even when the external wall has the required 70 mm of mineral wool slab insulation. It is caused by the negative effect of the wall corner thermal bridge. This effect is determined by ArchiCAD 20 software packages by visualizing the temperature distribution in the cross-section of the corner, which needs an additional thermal insulation layer of 40 mm. Using the LiraSAPR 2013 software package, the authors reduced the square cross-section dimensions of the column by 40 mm to allow for that additional thermal insulation layer. The optimal width of this layer is determined for different options for the meeting angle of two external walls from 70° to 180°. For a typical 90° angle, an acceptable width is 860 mm. With this insulation, it is possible to achieve the required temperature at the corner. The authors eliminated the negative thermal effect of the corner by rounding it with cement-sand plaster. Using the isotherms, it was determined that the rounding radius of 300 mm allowed for equal temperatures on the corner and inner surface of the external walls. The achieved results show that the microclimate formed as in a room without external wall corners.

Comparative Cost Analysis Between Hydraform Interlocking Brick and Sandcrete Block as Walling Materials for Low-Cost Housing Development in Nigeria

This study analyzed the cost of production and construction of 225mm hollow sandcrete blocks and hydraform interlocking bricks and walls to compare the findings of the results. The study was conducted in Auchi, Estako West Local Government Area of Edo State, Nigeria. The study compared the construction of two models of 225mm hollow sandcrete blocks and hydraform interlocking bricks, materials employed for wall construction for the study are; clay, cement, sand, water and mould. The result of the study indicates that unit cost of 225mm hollow sandcrete block and hydraform interlocking bricks are ₦168.57 and ₦57.85 respectively. While the cost per square metre of 225mm hollow sandcrete block wall and hydraform interlocking brick wall are ₦3,199.40 and ₦3,079.52 respectively. The study also revealed that it is more costly to apply finishes to sandcrete block wall when compared with hydraform interlocking brick wall. Sandcrete block wall requires rendering or plastering to both faces of the walls, while hyraform interlocking wall requires rendering of not more than 300mm girth to vertical external corners of the brick wall. The study, therefore, recommends the use of hydraform interlocking bricks for low-cost housing to reduce the housing deficit in Nigeria. Keywords : Sandcrete block; hydraform interlocking brick; walling; cost analysis; Auchi; DOI: 10.7176/JNSR/11-22-07 Publication date: November 30 th 2020

Discontinuous Bifurcation of a Soft-Impact System

In this paper, we investigate discontinuous bifurcations of a soft-impact system, which is nonsmooth at the switching boundary consisting of two parts. We find that there are no periodic orbits located only in the impact zone, and when grazing bifurcation on one part of the switching boundary occurs, the tangency point changes may occur for different bifurcation parameters, which is also verified by numerical simulation. In particular, we discover degenerate inner and external corner bifurcations, which can produce chaotic behavior, for example, period-doubling cascades and a degenerate inner corner bifurcation that induce chaotic responses. In this way, our investigation reveals the presence of narrow bands of chaotic motion induced by the afore mentioned dynamical phenomena.

Structural evaluation of masonry building damages during the April 24, 2014 Gökçeada earthquake in the Aegean Sea

An earthquake of MW = 6.5 occurred on May 24, 2014, at 12:25 h local time (09:25 GMT), its epicenter in the Aegean Sea, 25 km north of Gokceada. The effect of the earthquake produced the most damage in the rural houses of Gokceada. This paper describes the evaluations made through onsite field observations of the damages inflicted on the structures of thirty rural houses in the Tepekoy settlement connected to Gokceada. An evaluation was made of the types of damage, the mechanisms of damage and the causes of the damage sustained by these houses, which all had similar structural characteristics but different plan typologies and suffered varying levels of damage. The damage observed in Gokceada was classified using the catalogue of mechanisms originally developed for the failure mechanisms identification and vulnerability evaluation procedure. The general types of damage were cracks in the loadbearing external walls and corners, diagonal cracks starting from the corners of doors and windows, vertical out-of-plane displacement of external walls, out-of-plane fragmentation or disintegration and collapse of external wall and partial collapse of loadbearing internal walls, ruptures in the outer surfaces of loadbearing external walls, partial collapse of roof structure, partial collapse of hearth and chimney sections, rupture or flaking of window and door lintels. The causes of the general damage may be cited as an irregular bonding system, weak mortar, stone block formation, stone block size, absence of tie beams, corners weakly connected, weak connection of wall-roof system, week connection of wall-floor system, and different internal wall systems. The levels of damage and the mechanisms of damage vary depending upon the number of causes of the damage, the particulars of the layout, and some structural properties. In terms of the characteristics of the layout, an increase in unsupported loadbearing wall lengths led to more destructive damage mechanisms in the houses. In terms of structural characteristics, the construction of the internal wall system with timber on the upper floors, and with stone material on the lower floors was a major factor in increasing the level of damage and determining its type and mechanism.