Load-bearing Structural Elements Research Articles

Inspection and evaluation of the technical condition of a monolithic frame reinforced concrete structure of a hotel in Borovets resort

Abstract This study examines, the current research endeavours to analyse the results of structural inspection of an existing hotel building situated within the confines of Borovets resort. The structure consists of one basement level, four above-ground levels and one unusable attic level. The building was built site-cast in the period from 1983 until 1985. For the inspection, a series of activities were carried out, and the load-bearing structural elements of the building were established, the strength characteristics of the inserted materials were determined through destructive and non-destructive activities, a geometric survey of the load-bearing vertical and horizontal elements was carried out, existing defects and damages were found, an analysis of the impacts on the structure was made, the results of the structural assessment were summarized and basic recommendations were presented for bringing the building into compliance with the requirements of the current regulatory documents. The purpose of the performed in-situ, analytical, and computational activities is to establish the current technical condition of the load-bearing and non-load-bearing structural elements and to assess the possibilities for ensuring the future operation of the building, according to the construction and investment intentions of the owner.

Разработка математической модели деформационного поведения изоляционной перемычки в процессе гидрозакладки горной выработки

Implementing measures to eliminate the negative consequences of soil subsidence during mine workings is an urgent problem. One of the methods to close mine workings not in operation is the technology of hydraulic filling; new types of insulating jumpers are studied in order to improve the technology. To select optimum dimensions of the structural elements, a comprehensive study of the impact of geometry and materials structure on its operability is required. The ANSYS Mechanical APDL software package provides a mathematical model of the deformation behavior of the insulating jumper with step-by-step backfilling of the worked space with a backfill mixture. The model is fully parametrized in accordance with the geometrical dimensions of the structure, the mechanical properties of materials, the space-filling rate, and the backfill mixture properties. This enabled the automation of the process of analysis of the impact of technological solutions and the nature of filling the worked mine space on the operability of load-bearing structural elements. Within the framework of the first approximation, the impact of the bearing frame wall thickness on the waterproof jumper stress-strain state has been evaluated; the behavior of the structure during a step-by-step filling and under instantaneous load has been compared.

Atmospheric Pressure Plasma Treatment of Glass Surface and Its Influence on the Reliability of Adhesive Bonding

Glass load-bearing structural elements are currently used more often in civil engineering. However, due to the brittle fracture of glass, it is necessary to design these structures with sufficient reliability. Adhesive joints have a number of advantages over mechanical connectors of glass commonly used in construction. Adhesives can eliminate thermal bridges and provide a more uniform stress distribution along the connection without weakening the bonded material.A variety of chemical methods have been developed for cleaning and activating glass surfaces prior to adhesive bonding. Recently, these methods have been substituted by glass surface cleaning and activation using ambient (humid) air plasma. Such an approach is considered much faster, technically simpler, and more environmentally friendly than the traditional chemical methods. For example, it eliminates the need for the so-called primer interlayer, where the primer is usually considered a heavy chemical with significant environmental impact.The presented work is focused on the surface activation of glass by atmospheric pressure plasma to improve adhesion using specially selected transparent adhesives. We studied Diffuse Coplanar Surface Barrier Discharge (DCSBD) plasma treatment of different float-glass, heat-treated and tempered glass surfaces in ambient air. The DCSBD plasma effect was evaluated by surface free energy and peel-test adhesion measurements. The morphological changes on the glass surface were investigated by scanning electron and atomic force microscopy. The glass-to-glass adhesion at elevated temperatures was tested with respect to the artificial ageing of adhesive bonding due to the environment. Acknowledgement: This research was supported by project LM2023039, funded by the Ministry of Education, Youth and Sports of the Czech Republic and supported by project No. GA23-06016S, funded by the Czech Science Foundation (GAČR).

Study and Analysis of Steel, RCC, and Composite Structure Comparison

In India, plain concrete is a common building material, especially for medium- and low-rise buildings. Even while steel is still widely used in high-rise structures and composite construction is less frequent, it's possible that composite construction could prove more beneficial in these projects. Reinforced concrete is often used in construction projects. Steel beams are put into concrete to make reinforced concrete, an efficient composite material. The distinguishing feature of composite construction is the secure joining and bending of two load-bearing structural elements into a single piece. When compared to RCC most steel frames, composite constructions are considered to be some of the least expensive and transient building materials. The main component of a composite construction is an I-section column embedded or encased in building materials, or a tube of steel filled with steel and concrete. Composed of cold steel plates plus mortar, Part I consists of a beam plus a plate for the deck. The beams are connected to the top slab using fire-resistant and robust shear connections. Keywords— Steel Concrete Composite Building, RCC building, Seismic Analysis etc.

GEODETIC MONITORING OF DEFORMATIONS OF BEARING REINFORCED CONCRETE STRUCTURES OF AN UNDERGROUND MULTI-FUNCTIONAL PUBLIC CENTER

The article highlights the stages of carrying out measurement and survey work of an underground multifunctional public center to assess the technical condition of the load-bearing structural elements of block 1 and the entrance group in order to carry out reconstruction on the above-ground part of the building. The reconstruction consisted of installing metal structures on the eastern and western sides of the dome and a metal canopy over the entrance group. As a result of a technical examination and geodetic observations, cracks with an opening width of 0.5 mm and significant deflections in the floor slabs and crossbars at the upper and lower levels were identified in the load-bearing structures. To ensure safe operation and timely detection of dangerous values of deformation of a unique building with an increased class of responsibility, an effective method of geodetic monitoring of deflections of reinforced concrete floor slabs and crossbars and recommendations for their strengthening, taking into account the location of the construction site at the intersection of zones of influence of several tectonic faults, are proposed. Geodetic observations of deformation processes were carried out. Based on the results of the measurements, it was decided to strengthen the reinforced concrete structures by gluing fiber-reinforced composite materials to the lower part of the floor slabs. A comparative analysis of the obtained quantitative parameters of shifts of load-bearing structures makes it possible to assess the technical condition of an underground building and its individual structures before and after strengthening measures.

The Importance of Application of EN ISO 3834 and EN 1090 in Production of Steel Structures

Fractures of welded structures in operational conditions most often occur in the welded joint or its immediate vicinity. Due to this, special attention is paid to ensuring the quality of the welded joint. The application of the EN ISO 3834 and EN 1090 standards in the manufacture of steel structures aims to ensure the highest possible quality of welded joints, and thus the quality of the structures as a whole. Weld quality is achieved by welding, whereas weld quality control provides a check of product reliability. Increasing requirements in terms of reliability, better use of materials, lower weight and cost of constructions, but also high use of load-bearing structural elements, and thus welded joints, leave less room for errors in welded joints, which is why constant control and monitoring of documented procedures is required.

Exploring the Cyclic Behaviour of URM Walls with and without Damp-Proof Course (DPC) Membranes through Discrete Element Method

Unreinforced masonry (URM) walls are common load-bearing structural elements in most existing buildings, consisting of masonry units (bricks) and mortar joints. They indicate a highly nonlinear and complex behaviour when subjected to combined compression–shear loading influenced by different factors, such as pre-compression load and boundary conditions, among many others, which makes predicting their structural response challenging. To this end, the present study offers a discontinuum-based modelling strategy based on the discrete element method (DEM) to investigate the in-plane cyclic response of URM panels under different vertical pressures with and without a damp-proof course (DPC) membrane. The adopted modelling strategy represents URM walls as a group of discrete rigid block systems interacting along their boundaries through the contact points. A novel contact constitutive model addressing the elasto-softening stress–displacement behaviour of unit–mortar interfaces and the associated stiffness degradation in tension–compression regimes is adopted within the implemented discontinuum-based modelling framework. The proposed modelling strategy is validated by comparing a recent experimental campaign where the essential data regarding geometrical features, material properties and loading histories are obtained. The results show that while the proposed computational modelling strategy can accurately capture the hysteric response of URM walls without a DPC membrane, it may underestimate the load-carrying capacity of URM walls with a DPC membrane.

Анализ прочности печатной платы на растяжение–сжатие методом частиц

Traditionally, the load-carrying printed circuit boards are applied as an electrical engineering device. At the same time, the promising nanosatellites are using them as the spacecraft load-bearing structural elements. The printed circuit board is able to accommodate a relatively heavy solar cell, rotating gyroscopes and a folding antenna. Load-carrying board strength calculation is a complicated task, as a large number of stress concentrators and structural defects are effecting its surface. This makes it difficult to use the traditional concept of “stress at a point” applicable in continuous and differentiable media. In this regard, the paper proposes to introduce the concept of the “model rupture-start time moment for a given particle pair”. Calculations show that even slow loading of the model under consideration leads to extremely intense particles motion, i.e. the static loading hypothesis does not work. To analyze strength of the board under consideration, the Cauchy problem with initial conditions was formulated. The problem solution convergence based on the number of particles in the model was analyzed. The paper shows that the convergence rate is quite high, and to solve the problem under consideration it is sufficient to take a model containing about 100 particles.

Fabrication and verification of vertical graphene-based strain sensor

The purpose of structural health monitoring in civil and mechanical engineering infrastructure is to make a structure safer at a lower cost. Strain, one of the crucial monitoring variables, has an innate relationship with deformation and is sensitive to the degeneration of load-bearing structural elements. In this study, a set of wireless real-time data acquisition and strain monitoring systems based on vertical graphene (VG) were developed. Both the parametric study and the feasibility of the VG-based strain sensor in crack monitoring of concrete structures were investigated. The greatest resistance difference in the cyclic tensile test is 2.99%, and the linearity is 2.4%, proving the newly designed sensor has good repeatability and stability. According to the monotonic tensile test based on a micro-displacement control platform, the relative resistance to change ΔR/R rises as applied strain rises and the repeatability error results in 0.576%. According to the notched concrete beam under the three-point bending test, the VG-based strain sensor's discrepancy from the extensometer's monitoring data is within 11.04%. The findings of this study suggest that the newly developed VG-based strain sensor has the potential for practical application in field strain monitoring, thus reaffirming the feasibility and effectiveness of this novel sensing technology.

Пропозиції щодо перспективної конструкції вантажного вагона зі змінними кузовами

The importance of this work for Ukraine stems from the need for efficient freight transportation technologies, freight car fleet renewal, introducing swap-body freight cars, and increasing their operating safety. Swap-body cars are an innovation in freight services. Traditionally, versatile and specialized freight cars consist of an undercarriage part (running gear, automatic couples, and automatic braking devices), which, as a rule, is versatile, and a body part (an underframe and a body). The cost of the former and the latter is 80 and 20 per cent, respectively, of the total car cost. The idea of a swap-body car is to separate the underframe from the car body and include the former into the undercarriage part, thus leaving only the car body in the body part. Thus, the undercarriage part of a car of this type is a flat car for swap bodies, which consists of an underframe, running gear, automatic couples, automatic braking devices, and body fasteners. A new type of freight rail vehicles for unimodal railway transportation is the swap-body car, whose bodies can be replaced according to seasonal freights. For the Ukrainian railways, it is expedient to develop a swap-body car design of their own. This calls for scientific and technical support at the design and the operational development stage. The aim of this work is to determine the maximum loads on the load-bearing structural elements of swap-body cars in normal operation and to work out recommendations on a prospective home design of a swap-body freight car. This paper presents a mathematical model of 3D vibrations of a swap-body freight car in its normal motion along a track of arbitrary alignment, which accounts for the technical condition of the car undercarriage and the track. This model underlies the scientific and technical novelty of the paper. The analytical model of a swap-body car moving along a track is a mechanical system of rigid bodies. For each wheel, the track is simulated as an equivalent mass, which can move only in a vertical and a lateral horizontal direction and bears in these directions on springs and viscous dampers, which model the elastoviscous properties of the rails and the underrail base. The nonlinear differential equations of the system’s dynamics are solved by the Adams?Bashforth method. The paper presents a numerical estimate of the dynamics of motion of cars with swap bodies of different length and mass. For all the car motion variants considered, the maximum forces in the fitting supports whereby the body is supported on the undercarriage do not exceed their permissible values. The calculated values of the flat car’s dynamic parameters show that in terms of safety a car speed higher than 80 km/h is not safe for all the body-on-undercarriage layouts considered. Practically important recommendations on a prospective home design of a swap-body freight car are presented. The innovative technology of freight transportation with the use of swap-body cars will allow one to avoid car demurrage caused by seasonal variations in freight shipment and speed up the replacement of damaged bodies. Besides, the service life of a body may differ from that of an undercarriage, which allows one to reduce acquisition, operation, and maintenance costs.

Stochastic analysis of load-transfer mechanism of energy piles by random finite difference model

The surge in demand for renewable energy to combat the ever-escalating climate crisis promotes development of the energy-saving, carbon saving and reduction technologies. Shallow ground-source heat pump (GSHP) system is a promising carbon reduction technology that can stably and effectively exploit subsurface geothermal energy by taking advantage of load-bearing structural elements as heat transfer medium. However, the transformation of conventional geo-structures (e.g. piles) into heat exchangers between the ground and superstructures can potentially induce variable thermal axial stresses and displacements in piles. Traditional energy pile analysis methods often rely on deterministic and homogeneous soil parameter profiles for investigating thermo-mechanical soil-structure interaction, without consideration of soil spatial variability, model uncertainty or statistical uncertainty associated with interpolation of soil parameter profiles from limited site-specific measurements. In this study, a random finite difference model (FDM) is proposed to investigate the thermo-mechanical load-transfer mechanism of energy piles in granular soils. Spatially varying soil parameter profile is interpreted from limited site-specific measurements using Bayesian compressive sensing (BCS) with proper considering of soil spatial variability and other uncertainties in the framework of Monte Carlo simulation (MCS). Performance of the proposed method is demonstrated using an illustrative example. Results indicate that the proposed method enables an accurate evaluation of thermally induced axial stress/displacement and variation in null point (NP) location with quantified uncertainty. A series of sensitivity analyses are also carried out to assess effects of the pile-superstructure stiffness and measurement data number on the performance of the proposed method, leading to useful insights.

Experimental study of the bearing capacity of compressed steel struts of an I-beam profile in conditions of constrained torsion

Wide application in the construction of thin-walled steel rods of an open profile requires taking into account the peculiarities of the work of load-bearing structural elements under the action of the entire complex of loads. For a number of rod systems consisting of I-beam profiles, it is impossible to exclude torsion under the action of compressive forces, which leads to the appearance of additional normal stresses in the profile. In this regard, it is necessary to study the actual operation of compressed I-beams under the action of torsional loads. The bearing capacity of a compressed I-beam profile strut with constrained torsion is considered. The method of conducting an experimental study of a centrally and off-center compressed I-beam profile strut under the action of longitudinal force and bimoment is presented. The analysis of the effect of the bimoment on the bearing capacity of a centrally and off-center compressed thin-walled rod of an open profile with constrained torsion is performed. The bearing capacity of the centrally and off-center compressed I-beam profile strut from the action of longitudinal force and bimoment was experimentally determined, which was compared with the results of numerical calculations in finite element formulation, taking into account geometric and physical nonlinearity in conditions of constrained torsion. According to the results of the experiment, the possibility of using numerical modeling to assess the stability of centrally and off-center compressed thin-walled rods was established. open profile with constrained torsion under various schemes of external force.

Finite element modeling of heat propagation of a complete rod of constant cross-section

In this paper, the definition of the temperature distribution field for a rod made of heat-resistant alloy EI48 is introduced. The authors consider for the study a complete rod of circular cross-section of radius R, of limited length L. Studied body is under the influence of a heat flow q from the surface over the entire cross-sectional area of the left end, and heat exchange with the environment occurs on the cross-sectional area of the right end. The rod is thermally insulated along the side surface. The authors consider two cases: the first is the heat flow with intensity q can be set on the area of a small circle with radius r <R, the second is the heat flow can be set on its part, that is, on the area . During the study, the authors showed that during the thermomechanical process, the strength of each section of the load-bearing structural elements is significantly influenced by the temperature distribution field. The influence of high temperature on the morphology of heat-resistant alloys is also shown. This leads to the fact that in some parts of the structural elements the temperature will be acceptable, and in some — critical. As a result, rapid wear of structural elements and loss of their physical qualities occur. Therefore, mathematical modeling of temperature distribution field for a body of various configurations is an urgent problem. The article presents a method for constructing a mathematical model and a corresponding computational algorithm that allows solving a class of problems to determine the regularities of the temperature distribution field in the elements of rod-shaped structures. To do this, the authors used the energy-variation principle in combination with the finite element method.

Applications of Biomimetic Adaptive Facades for Enhancing Building Energy Efficiency

The façade is the main component related to the design, occupation and performance of buildings. In the past, traditional facades were always constructed as load-bearing structural elements without flexibility, which made it impossible to deal with the changing environment, resulting in the consumption of large amounts of energy to maintain the internal comfort conditions. Biomimetic adaptive strategies have been proposed as an optimal solution for improving building façade performance. This paper aims to present biomimetic strategies that are translated into design solutions for dynamic façades, resulting in adaptive, flexible and more efficient façade design. Several illustrated case studies and researches have shown the high potential of biomimetic adaptive facades to reduce total energy consumption without reducing the internal comfort of buildings, which is a promising new approach to energy-efficient and sustainable building solutions.

3D-Concreting – Compositions, Techniques and Properties of Mixtures

The paper reflects the problems of 3D-concreting technology, which is developing quite intensively in modern conditions of construction production. The most important condition for its practical implementation is the development of concrete mixture compositions that provide the necessary rheological (technological) properties for formation of products, elements of building structures or the structure as a whole, as well as providing the required pace of work and physical and mechanical characteristics and properties of the hardened concrete. At the initial stage of research carried out in the Research and Testing Laboratory of Concrete and Building Materials of the Belarusian National Technical University a number of concrete mixtures compositions were developed that are designed and provide the necessary conditions for the implementation of 3D-concreting of self-supporting and load-bearing structural elements respectively, in the manufacture of products of small architectural forms and the erection (arrangement) of building structures for various purposes. A methodology has been developed and implemented for the selection of a rational granulometric composition of aggregate, type, properties and amount of binder, chemical and mineral additives, together providing the required technological properties of concrete mixtures after they have been mixed with water. Original methods for assessing the rheological properties of water-soluble concrete mixtures and their changes over time, leading to an increase in the plastic strength of molded concrete, as well as a method for calculating the rate of concrete work depending on the properties of the concrete mixtures used, are proposed and experimentally substantiated. As a result, prerequisites have been created for further expansion of a number of compositions of dry concrete mixes taking into account their purpose for 3D-concreting, and for developing methods and evaluating the physical and mechanical characteristics and properties of hardened concrete, taking into consideration the purpose of manufactured products and erected (arranged) building structures.

Mechanical Properties of Lightweight Foamed Concrete Modified with Magnetite (Fe3O4) Nanoparticles

The advancement in sustainable construction has stimulated wide-ranging investigation of construction materials and practices globally. With exceptional thermal properties, fire resistance performance, excellent strength, and outstanding durability, concrete is the utmost extensively utilized construction material around the world. Taking into consideration the quantity of concrete necessary for numerous constructions works, improving concrete sustainability would be an extremely attractive potential. Lightweight foamed concrete (LFC) is tremendously permeable, and its mechanical properties weaken with a growth in the volume of voids. Air-void segregation from solid cement phases by means of aging, drainage, and merging of voids can trigger and reduce the stability and consistency of the emitted pores, making the LFC less reliable for main utilization in load-bearing components and structural elements. In turn, to augment LFC mechanical properties, the LFC cementitious matrix can be adjusted by adding various nanoparticles. The influence of magnetite nanoparticles (MNP) in LFC was not examined in the past; hence, there is some vagueness considering the mechanism to which level the MNP can affect the LFC mechanical properties. Thus, the aim of this study is to investigate the influences of MNP on the compressive, splitting tensile, and flexural LFC of 1000 kg/m3 density. Six MNP weight fractions of 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, and 0.35% were considered. The parameters accessed were compressive, splitting tensile and flexural strengths. The correlation between strength parameters was established as well. The results indicated that a 0.25% weight fraction of MNP gave the best performance in terms of compressive, flexural, and splitting tensile strengths. The presence of MNP in the LFC matrix enhances the viscosity and yield stress of the mixture as well as an augmented utilization of LFC cementitious binder content, which can sustain the integrity of the wet networks hence preventing further amalgamation and aging of the voids.

ПОВЫШЕНИЕ ТЕХНИЧЕСКИХ ХАРАКТЕРИСТИК СЕЛЬСКОХОЗЯЙСТВЕННЫХ ШИН ДЛЯ ПРИЦЕПНОЙ ТЕХНИКИ

A problem of import substitution is acute not only for the raw material base for the tire industry, both for the military-industrial complex and for the national economy, but also for products in general due to the current geopolitical situation. The problem of improving the technical characteristics of tire products to the level of leading manufacturers in Europe and the USA with the maximum use of domestic raw materials, taking into account the preservation of the level of product quality is considered in the article. An overview of the results of investigations of LLC “NORTEC”, carried out as part of import substitution for agricultural tires for trailers of the RUF-2 type, is given. The influence of the use of anid cords instead of the previously used nylon cords in the main load-bearing structural elements on the tire performance was established. Also, to improve the quality of products, the formulations of rubber compounds have been revised in terms of increasing the proportion of natural rubber to reduce the risk of tire destruction in the shoulder area when working with overload and at low pressure relative to the norm, which is most important for trailer tires. Based on the results of laboratory tests, it was established that the developed design of an agricultural tire with improved technical characteristics for trailers fully complies with the requirements of the Russian Federation standards and has improved performance characteristics with the elimination of the previously existing problem - tire destruction in the shoulder area

Influence of Elevated Temperature on the Mechanical Properties of Transparent Adhesive Glass-Glass Joints

Glass is an attractive, transparent but brittle material which is increasingly popular in civil engineering. Not only small and secondary glass structures such as canopies or railings, but also load-bearing structures or structural elements such as stairways, beams, facades, etc. are commonly designed today. The wider use of glass places demands on the connections of glass-to-glass or glass-to-other materials. Mechanical connections are commonly used owing to their known mechanical properties but there is pressure to use adhesives for their considerable advantages. Unfortunately, there is not enough information about the mechanical properties of adhesives exposed to environmental effects and elevated temperature. The paper is focused on experimental testing of glass-to-glass connection using transparent adhesives. The specimens were prepared as double-lap shear joints with 1 mm adhesive joint thickness. In the study, three two-component epoxy adhesives were selected, one rigid adhesive and two semi-rigid adhesives. Specimens were tested at room temperature (reference set) and at elevated temperature (80 °C), six sets of specimens were prepared in total. The test was controlled by displacement with continuous loading until the specimen’s collapse. The cross-head speed was 0.05 mm/min. Shear strength at failure rapidly decreased for specimens exposed to elevated temperature and each specimen failed due to loss of adhesion between adhesive and glass.

SPECTRAL METHODS FOR DETERMINING THE SEISMIC FORCES OF BUILDINGS

The article discusses methods for calculating seismic effects on buildings and structures along the spectral curve, creating a dynamic calculation scheme for load-bearing structural elements, inertial reactions and displacements of building structures, natural and forced vibrations of buildings under the effect of seismic forces.

Challenges and Opportunities in Scaling up Architectural Applications of Mycelium-Based Materials with Digital Fabrication.

In an increasing effort to address the environmental challenges caused by the currently linear economic paradigm of “produce, use, and discard”, the construction industry has been shifting towards a more circular model. A circular economy requires closing of the loops, where the end-of-life of a building is considered more carefully, and waste is used as a resource. In comparison to traditional building materials such as timber, steel and concrete, mycelium-based materials are renewable alternatives that use organic agricultural and industrial waste as a key ingredient for production, and do not rely on mass extraction or exploitation of valuable finite or non-finite resources. Mycelium-based materials have shown their potential as a more circular and economically competitive alternative to conventional synthetic materials in numerous industries ranging from packaging, electronic prototyping, furniture, fashion to architecture. However, application of mycelium-based materials in the construction industry has been limited to small-scale prototypes and architectural installations due to low mechanical properties, lack of standardisation in production methods and material characterisation. This paper aims to review the current state of the art in research and applications of mycelium-based materials across disciplines, with a particular focus on digital methods of fabrication, production, and design. The information gathered from this review will be synthesised to identify key challenges in scaling up applications of mycelium-based materials as load-bearing structural elements in architecture and suggest opportunities and directions for future research.