Search Results (41)

The aim of the work is to analyze the survival strategy of Taxus baccata L., one of the promising plants for landscaping and the creation of woodlands, in the changing ecological conditions of the steppe zone of the Donetsk ridge. In order to achieve this goal, we used biomechanics methods, which help to understand the relationship between the physical and mechanical properties of living tissues and the overall stability of trees during interactions with environmental factors such as temperature, snow and ice storms, cyclic freeze–thaw processes, wind loads, and others. The work was based both on experimental studies on the estimation of the tissue elasticity modulus in response to temperature changes, the mechanical stability of plants, the field collection of materials, and studies on the modeling of forest stand conditions of English yew. As a result of the conducted experiments, it was established for the first time that at the absolute wood moisture content of 77 ± 5.1%, the density of wood tissues in the conditions of Donetsk is 907 ± 43 kg m⁻³. The modulus of elasticity of living tissues depending on the temperature factor varied in the following range: 8.8 ± 0.31 GN m⁻² (T = 288 K), 11.5 ± 0.55 GN m⁻² (T = 255 K) and 6.9 ± 0.47 GN m⁻² (t = 308 K). It was revealed that during the local thawing of skeletal branches and tables, the mechanical resistance of T. baccata is reduced by 20–22% and this critically affects the overall plant resistance. It was established for the first time that T. baccata in the conditions of the steppe zone has an adaptive strategy of preserving the integrity of the organism under the action of environmental factors with limited loads. The secret lies in the formation of the shape memory effect, under the influence of critical loads. The plant, thus, chooses not migration, not death, but adaptation to changes in environmental conditions, which can become a serious factor in the use of T. baccata in the landscaping of urban areas and the creation of artificial forests. Full article

Sandwich panels have established themselves as self-supporting and isolating construction elements for room closures in hall construction. As a result of subsequently installed photovoltaic (PV) systems or cladding, sandwich panels are subjected to point loads at the connection points to the substructure of additional systems. In the case of pressure-suction changes from wind, a cyclical local load also occurs. Therefore, for sandwich panels—which are designed and dimensioned for uniform surface loads (dead weight, wind, snow, temperature constraints)—the question must be answered as to how this local load introduction affects the load-bearing behaviour and stress distribution in the sandwich panel. To quantify any stress concentrations across the width of the panel, the method of effective widths is used here, based on stress distributions in the elastic range determined through component tests and numerical models. The results of these test series, along with the resulting design concept based on effective widths in the elastic range, as well as the failure under the ultimate load condition, are documented in this paper. Full article

The dynamic relationship between microplastics (MPs) in the air and on the Earth’s surface involves both natural and anthropogenic forces. MPs are transported from the ocean to the air by bubble scavenging and sea spray formation and are released from land sources by air movements and human activities. Up to 8.6 megatons of MPs per year have been estimated to be in air above the oceans. They are distributed by wind, water and fomites and returned to the Earth’s surface via rainfall and passive deposition, but can escape to the stratosphere, where they may exist for months. Anthropogenic sprays, such as paints, agrochemicals, personal care and cosmetic products, and domestic and industrial procedures (e.g., air conditioning, vacuuming and washing, waste disposal, manufacture of plastic-containing objects) add directly to the airborne MP load, which is higher in internal than external air. Atmospheric MPs are less researched than those on land and in water, but, in spite of the major problem of a lack of standard methods for determining MP levels, the clothing industry is commonly considered the main contributor to the external air pool, while furnishing fabrics, artificial ventilation devices and the presence and movement of human beings are the main source of indoor MPs. The majority of airborne plastic particles are fibers and fragments; air currents enable them to reach remote environments, potentially traveling thousands of kilometers through the air, before being deposited in various forms of precipitation (rain, snow or “dust”). The increasing preoccupation of the populace and greater attention being paid to industrial ecology may help to reduce the concentration and spread of MPs and nanoparticles (plastic particles of less than 100 nm) from domestic and industrial activities in the future. Full article

The aim of this paper is to conduct reliability analysis of flexural strength design provisions of FRP-reinforced concrete (FRP-RC) beams in accordance with CSA S806. In particular, different load combinations, including dead, live, wind and snow, are investigated. Through this, the various sources of uncertainty related to the material strength and geometrical properties are taken into account when examining the reliability of the flexural strength provisions of CSA. The uncertainty inherent in the flexural strength model is assessed using a large experimental database of 303 FRP-RC beams assembled from the literature. The first-order reliability method (FORM) is employed for reliability analysis. The results indicated that the reliability index, β, of the current code is not consistent for different failure modes, yielding overly conservative values for the FRP rupture mode (β = 4.895) compared to the concrete crushing mode of failure (β = 3.726). Based on the reliability-based calibration of the existing design equations, modifications to the current provisions are proposed to achieve a variety of target reliability indexes of 3.5, 3.8, and 4 for the failure modes of concrete crushing and FRP rupture, separately, and for a common range of load ratios in the different load combinations. The results presented enable designers to choose proper strength-reduction factors to reach the desired level of safety for each failure mode in the flexural design of FRP-RC beams. Full article

Moisture ingress is a critical concern in buildings, as it may profoundly affect structural integrity, the energy efficiency of a building, and as well the quality of the indoor environment that, in turn, could influence the health and safety of building occupants. Moisture ingress can occur during any phase in the lifecycle of a building component, where environmental loads, such as precipitation, wind, snow, and elevated relative humidity, play a fundamental role in affecting the building structure. Climate change exacerbates the issue of moisture ingress by intensifying these loads. In this review paper, the statistical perspective on publications related to moisture ingress in building envelope materials (BEMs) was first assessed through a scientometric study. All relevant publications were gathered and manually filtered, and the selected papers were categorized based on the topics discussed. The results of the scientometric study, as presented in this paper, include a bar chart in which the number of publications in each category is illustrated; a science journal mapping diagram showing the interdisciplinary connections of the research; a cluster map depicting the network between topics; and an R&D momentum analysis reflecting the rate of growth and publication count in this field. Given the strong focus on material properties, this review also examines experimental methods for characterizing moisture transport properties in building materials used in BEMs. Additionally, the differences between various codes and standards centered on this topic are reviewed and discussed. This combined strategy is intended to comprehensively evaluate available information and approaches to permit identifying the knowledge gaps that need to be addressed. Full article

The integration of photovoltaic (PV) systems into tensioned membrane structures presents a significant advancement for sustainable applications in the built environment. However, a critical technical challenge remains in the substantial strains induced by external loads, which can compromise both PV efficiency and the structural integrity of the membrane. Current design methodologies prioritize stress, deflection, and ponding analysis of tensioned membranes. Strain behavior of whole structures, a key factor for ensuring long-term performance and compatibility of PV-integrated membranes, has been largely overlooked. This study addresses this gap by examining the whole membrane structure designed for PV integration, with the aim of optimizing the membrane to provide suitable conditions for efficient energy transfer while minimizing membrane strains. For this purpose, it provides a comprehensive strain analysis for full-scale hyperbolic paraboloid (hypar) membrane structures under various design parameters and external loads. Employing the Finite Element Method (FEM) via Sofistik software, the research examines the relationship between load type, geometry, material properties, and patterning direction of membranes to understand their performance under operational conditions. The findings reveal that strain behavior in tensioned membrane structures is strictly influenced by these parameters. Wind loads generate significantly higher strain values compared to snow loads, with positive strains nearly doubling and negative strains tripling in some configurations. Larger structure sizes and increased curvature amplify strain magnitudes, particularly in parallel patterning, whereas diagonal patterning consistently reduces strain levels. High tensile-strength materials and optimized prestress further reduce strains, although edge type has minimal influence. By systematically analyzing these aspects, this study provides practical design guidelines for enhancing the structural and operational efficiency of PV-integrated tensioned membrane structures in the built environment. Full article

To address the structural concerns of a 12.0 m-span landing assembled single-tube frame (LASF) for Chinese solar greenhouses subjected to snow loads, the internal forces and deformations of LASF and its reinforced counterpart (RLASF) were numerically simulated to determine the ultimate bearing capacities (L_u) and the failure loads (L_f). During the simulations, steel tubes were modeled as beam188 elements and cables as link180 elements. The frame constraints and the connections were assumed to be fixed supports and rigid, respectively. The loads were determined according to the Chinese standard (GB51183-2016). Simulations revealed that the LASF and RLASF primarily withstand bending moments and are prone to strength failures under snow loads. Both exhibited lower L_u and L_f under non-uniform snow loads than under uniform snow loads. The results also indicated that crop loads could deteriorate the structural safety of the LASF and RLASF. L_u and L_f were found to be proportional to the section modulus of the tubes. The effects of wind loads and initial geometry imperfections on L_f of the LASF and RLASF can be neglected. Furthermore, the RLASF exhibited higher L_f compared to the LASF. Steel usage of the RLASF could be further reduced by replacing circular tubes with rectangular tubes, making the RLASF a feasible option for constructing Chinese solar greenhouses. Full article

As a pivotal node in both urban and rural power grids, the box-type substation not only serves the functions of power conversion and distribution but also need to provide structural support and environmental adaptability. However, deficiencies in strength, stiffness, or vibration characteristics may lead to vibration and noise issues, and extreme environmental changes can pose risks of structural damage. This study aims to verify and optimize the seismic resistance and environmental adaptability of box-type substations through finite element simulation methods. Using SOLIDWORKS, a three-dimensional model of the box-type substation was constructed, and static and dynamic analyses were conducted using Ansys Workbench to comprehensively evaluate the dynamic response of the box-type substation under wind, snow loads, and seismic action. Through iterative simulations and a comparison of multiple design solutions, the structural optimization of the substation was achieved. The optimized structure balances strength and stiffness, significantly reducing the weight of the substation body, with the wall thickness reduced by 60%. Additionally, the phenomenon of stress concentration on the side walls was eliminated, ensuring that the equivalent stress is below the material yield strength. This research provides methods and empirical results for enhancing the performance and reliability of box-type substations under seismic conditions, confirming the feasibility of a lightweight design, while ensuring structural safety. Full article

Entanglement in commercial fishing gear is one of the main factors inhibiting the recovery of critically endangered North Atlantic right whales. Installing low-breaking-strength (LBS) components in the buoy lines and main lines of stationary fishing gear may be a viable solution for some fisheries. But is it an effective solution for deep-water trap fisheries? This study quantified in-line rope tensions observed during fishing operations for snow crab (Chionoecetes opilio) in Newfoundland and Labrador, Canada. We conducted a controlled fishing experiment in which we documented the loads experienced while hauling fleets of traps. The results showed that several factors contributed to the loads observed, including the components of the traps, the presence of crabs, and environmental conditions such as wind direction and wave height. According to the statistical models, the maximum tension from the estimated marginal means was 477.53 kgf in the buoy line and 987.99 kgf in the main line for the baited hauls, which exceeds the safe working load (154 kgf) of the proposed low-breaking-strength components. Our results suggest that LBS components are not a viable solution for this deep-water fishery. Full article

In steel structures, skew thin steel plates serve as panel zones in structures spanning large spaces (e.g., warehouses and gymnasiums). Considerable research has been conducted on the shear buckling of panels due to seismic loads acting on a structure. Conversely, under snow or wind loads, the panel zone may experience compressive and tensile stresses simultaneously from two directions. Considering the economic preference for thin steel plates, evaluating the elastic critical local buckling stresses in the panel zone under biaxial normal stress may provide essential information to structural engineers. In this study, an elastic buckling analysis based on the energy method is performed to clarify the impact of panel geometry and boundary conditions on the elastic local buckling stresses of skew panel zones. As confirmed from the results, the local buckling stresses calculated using the energy method were consistent with those determined using finite element analysis. The findings indicate that a skew angle of up to 30° marginally affects the elastic buckling stress under uniaxial stress. Consequently, engineer-friendly design formulas were developed based on these findings. Comparisons with previous research demonstrated that the buckling loads reported were generally higher than those determined by finite element analysis. The study also established the correlation of the buckling stresses under biaxial stresses, which implied that the skew angle posed minimal influence on buckling stress for skew plates under biaxial stress. Additionally, a method for evaluating this correlation was presented. Engineers can utilize the provided design equations to more efficiently and accurately calculate buckling loads, facilitating a safer and more economical design of structures with skew plates. Full article

Over the years, structural engineering codes and specifications in Canada and elsewhere have moved from an allowable stress design (ASD) approach to a load and resistance factor design (LRFD) philosophy. LRFD methodology takes better account of the inherent variability in both loading and resistance by providing different factors of safety for loads of distinct natures with regard to their probability of overload, frequency of occurrences and changes in point of application. The method also results in safer structures because it considers the behavior at collapse. While resistance factors for traditional construction materials based on LRFD in the National Building Code (NBC) of Canada are available, they cannot be used for non-conventional ones. This is because the resistance of such materials due to various load effects has unique bias factors (λ_R) and coefficients of variation (V_R), which greatly impact their reliability index (β). In this study, relationships between the resistance factor ϕ and critical load effects from the NBC load combinations at ultimate limit states are developed for a wide range of resistance bias factors and coefficients of variation. The relationships are presented in the form of charts that are useful for researchers and code-writing professionals who have expertise in the various fields of structural engineering but lack proper background in reliability theory. The developed spectra showed that for the same ϕ, β increases with an increase in the live-to-dead load (L/D) ratio until it reaches 1; thereafter, the shape of the relationship will depend on the statistics of the resistance as well as on the magnitude of ϕ. For a small ϕ and V_R, β will keep increasing with an increase in the L/D ratio from 1 until 3, albeit at a lesser rate. For L/D > 3, the relationship between the critical β and applied load is just about constant. This finding is also true for load combinations involving snow and wind. Application of the method is illustrated by a practical example involving the shear strength of a corrugated web steel beam. Full article

The prohibitive costs of small-scale solar photovoltaic (PV) racks decrease PV adoption velocity. To overcome these costs challenges, an open hardware design method is used to develop two novel variable tilt racking designs. These are the first stilt-mounted racking designs that allow for the manual change of the tilt angle from zero to 90 degrees by varying the length of cables. The racks are designed using the calculated dead, wind, and snow loads for Canada as a conservative design for most of the rest of the world. Structural capacities of the wooden members are then ascertained and the resisting bending moment, shear force, tensile force, and compressive force is calculated for them. A structural and truss analysis is performed to ensure that the racking design withstands the applicable forces. Moreover, the implications of changing the tilt angle on the wooden members/cables used to build the system are also determined. The systems offer significant economic savings ranging from one third to two thirds of the capital expenses of the commercially available alternatives. In addition, the racking designs are easy-to-build and require minimal manufacturing operations, which increases their accessibility. The stilt-mounted designs can be employed for agrivoltaic settings while allowing farm workers shaded, ergonomic access to perform planting, weeding, and harvesting. Full article

Large high-frequency reflector antennas typically operate outdoors and are impacted by environmental factors such as wind, rain, snow, solar radiation, etc. These conditions cause the antenna structures to distort, which, in turn, affects electrical performance. The observation performance of the antenna is seriously affected. To solve this problem, based on the active control of sub-reflector arrays, an optimization method for sub-reflector arrays and an active compensation method for electrical performance are proposed. Through real-time regulation of the phase plane of the distorted aperture field, the electrical performance of the antenna can be compensated for. The research object, a 65 m Cassegrain dual-reflector antenna, is designed in this work using a sub-reflector with an aperture of 6.1 m. The form and posture of the sub-reflector are comprehensively changed by adjusting the position of the sub-reflector panel and the overall movement of the sub-reflector, and the phase inaccuracy of the aperture field brought by the deformation of the main reflector is compensated for. The simulation results demonstrate that the maximum gain loss can be reduced from 0.44315 dB to 0.0803 dB and the maximum point error can be reduced from 0.00143° to 0.00047° under wind load with an average wind speed of 12 m/s using the active sub-reflector array adjustment strategy proposed. Full article

In this paper, the mechanics of inflatable drop-stitch panels are investigated, including the impact of large shear deformations, nonlinearity due to wrinkling of the panel skin that occurs under net compressive strain, work done by the confined internal air, and the effect of the drop-stitch yarns on the panel skin stresses. A large deflection finite element (FE) analysis framework is presented that allows for a panel’s stability and post-buckling response to be quantified. The FE code is verified through comparison with available analytical solutions, and the impact of critical response drivers is examined. The FE models are then used to explore the capacity of panel walls when used as part of a shelter subject to realistic wind and snow loads and to assess the dependence of the capacity on the important design parameters of inflation pressure and panel depth. The analyses indicate that while the drop-stitch panel capacity is sensitive to the panel depth and inflation pressure, panels with reasonable cross-sectional dimensions are viable for use in structural applications where they must support significant compression and bending. Future work should focus on increasing the structural efficiency and capacity by increasing the panel shear stiffness and operational inflation pressure. Full article

The existing large inflatable membrane structure is complex in structure and takes a long time to be extended. In this paper, an air-ribbed skeleton membrane structure is proposed to meet the requirement of camp and emergency tents needing to be set up quickly and easily. Ten single-arch air ribs are arranged side by side to support the tarpaulin, and wind ropes are added to the end and side faces of the tarpaulin to remain stable. The finite element model of the air-ribbed skeleton membrane structure is established to analyze the stress and the displacement of the membrane structure under combined wind and snow loads. The maximum displacement (439.4 mm) and maximum stress (29.94 MPa) are both within the safe standard. The stress and the displacement of the membrane structure in the wind load case is affected by the angle of the wind. The value of maximum stress and displacement at the wind angle of 90° are both lower than those at 0° and 45° in the wind load case. It is advisable to align the site layout of the membrane structure at the wind angle of 90°. The effect of the angle of wind ropes on the stress and displacement of the membrane structure is also studied. The maximum stress and displacement in the case when the angle of wind rope is 30° is smaller than those in the case when the angle of wind ropes is 45°. It is recommended that the wind rope should be laid at 30° to reinforce the membrane structure. Full article