Load-bearing Elements Research Articles

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The article describes the features of the transition to information modeling at the design stage, which lead to an increase in the number of digital information models. Quantitative and qualitative improvement of models entails an increase in the time spent by highly qualified labor resources. A method is proposed for sorting intersection collisions for their subsequent correction in order to rationalize the use of labor resources in design organizations, and the organization of work to improve the quality of digital information models, and design solutions in general. Thus, using the collision sorting method, assigning weights to elements, it is possible to increase the productivity of qualified engineers through the rational use of labor resources.
 The greatest number of collisions consist of the intersection of walls with walls, from this it can be concluded that the tool with which the walls are modeled is used incorrectly, there is probably a duplication of elements. The value of weak intersections in the future can be reduced, thereby the verification conditions will become tougher, there will be more intersection collisions, the quality of the CIM will increase after their correction. The values of the weights in this study are assigned based on the fact that the load-bearing elements have a higher priority.
 As further research, it is possible to determine the weights for most of the CIM elements in different types of capital construction projects by expert evaluation and make methodological recommendations.

Mechanical Properties of Austenitic Stainless Steel After Exposure to Elevated Temperature

Stainless steel has been widely used in the building industry as load-bearing elements such as beams and columns. Many fire accidents in stainless steel buildings were recorded, but only a few have collapsed entirely. These buildings can be rehabilitated and the undamaged parts can be reused, which reduces the economic losses in buildings exposed to fire. The residual mechanical properties of stainless steel after the fire, are the primary determinant of the validity of the stainless steel structure. In this paper, the effect of high temperatures and the time of exposure and cooling method on the mechanical properties of S304 stainless steel was studied. The specimens were heated to 800°C and 1000°C for different heating times (30, 60,90 and 120 minutes) and cooling methods (air-cooled and water-cooled). Results showed that the post-fire yield stress was reduced by 24% and 18% after heating to 800°C for 120minutes and cooled in water and air respectively. However, heating to 1000°C showed a marginal effect on the yield stress of air-cooled specimens and a clear reduction (29%) in the water-cooled specimens. Elongation capacity increased with heating time for 1000oC specimens but decreased for 800oC specimens in both cooling methods.

Çelik Bina Modellerinin Kolonlarında Molibden Profil Kullanımının Modal Parametrelere Etkisi

From past to present, building designs and materials used are developing. Especially against the destructive effects of ground movements and free vibrations on structures, many structural system designs and composite structure designs have been developed. The purpose of the composite structure design is to choose different types of materials according to the structural load-bearing system stress, in short, to choose the most advantageous material type according to the cross-sectional stresses or to eliminate the negative aspects of one material with the positive aspects of another material. It is a known fact that the dynamic performance of steel structure carrier systems is high under the influence of ground movements and free vibrations. However, in cases where the section geometry cannot be changed due to architectural concerns due to architectural design difficulties, there are cases where the rigidity of the structure is not sufficient. In such cases, profiles made of different materials other than steel can be used in order to increase the rigidity of the structure, especially in the columns, which are a very important component of the structural load-bearing elements. Therefore, in this study, the effect of using molybdenum profile instead of steel profile on modal parameters in model steel structure columns was investigated. In the light of the information obtained, a decrease of approximately 23.72 percent was observed in the period value in the 1st free vibration mode of the steel-molybdenum structure model. Thus, it is understood that the rigidity of the model steel structure system increases. In cases where it is not possible to change the architectural design in steel structures, it is recommended to use column profiles as molybdenum profiles instead of steel profiles in order to provide the necessary rigidity and increase rigidity.

Hygric properties and adsorption characteristics of simple and dual coblayers of bio-sourced building materials

With the world's population increasing and energy demand on the rise, innovative materials are becoming one of the most important solutions for building designers. This paper focuses on the hygrometric properties of bio-sourced materials, specifically new cob mixes used for insulation and load-bearing wall elements, those materials consist of various mixes of French soils and fibers with different water contents. Experiments are conducted using the isothermal sorption and the one-sided moisture transmission tests in transient and steady states. The hygrometric properties of the homogeneous bio-sourced samples (a thermally insulating material, and a structurally mechanical material), and composite bio-sourced materials (both structural and insulating materials) were investigated. Five salt solutions were used to measure distribution of the relative humidity in each material. The moisture content and moisture transfer resistance of the insulating material is more important than the structural material. The composite material has the lowest moisture flux and the adsorption is influenced by the multilayers. Results show that as much as the material contains fibers, as much as its impermeability increases and its diffusivity decreases. Diminution of the bio-sourced material density increases its resistance to the moisture transfer. Using the Freundlich isotherm model, the volumetric water content, sorption capacity and water content were correlated for all the tested samples. The Moisture diffusivity for the studied bio-sourced materials drops strongly in the dry region where the relative humidity is lower than 30%. In the wet state, the moisture diffusivity decreases slightly.

Revealing patterns in the stressed-strained state of load-bearing structures in special rolling stock to further improve them

The object of research is strength indicators of load-bearing structures of special rolling stock (dump cars). The research problem is the appearance of the same type of cracks in the girder beams of dump cars, the repair of which is not provided for by the current repair documentation. Malfunction analysis, control tests, strength studies by calculation and experiment were carried out. The analysis of malfunctions of cars in operation helped prove the place of occurrence of fatigue defects – the girder beam. This made it possible to determine specific zones of load-bearing elements, in which during control tests of cars, on the basis of taking into account data on fatigue defects, it is necessary to measure stress parameters. The results of the control tests showed that the lowest value of the fatigue resistance reserve factor n=1.6 for the dump car is found in the zone on the girder beam in the area of the pivot beam. The value of n is within acceptable limits. Normative calculations were carried out and a separate calculation (emergency) mode was additionally defined in the SolidWorks Simulation 2019 software package (France). Based on the results of the dump car stress calculations, it was established that the maximum equivalent stresses in the load-bearing structures of the car occur during its unloading due to twisting, and the stress vectors are at an angle of 45°. During the calculation of individual load modes, the stresses exceed the permissible values. In order to ensure the necessary strength conditions, it is proposed to introduce a reinforcing pad into the girder beam of the dump car, due to which the calculated stresses are within the permissible limits. The research will contribute to devising the recommendations for the restoration of dump cars, for designing modern structures of special rolling stock, and for improving strength determination processes

Laboratory study on mechanical behavior of hollow π-type steel–concrete composite support in loess tunnel

Failure or over-deformation of tunnel supports is common when tunneling in loess areas. Steel-concrete composite support (SCCS) is an innovative new support system that could provide a viable solution to improve the support in loess tunnels. Due to a lack of research, there is only a preliminary understanding of the structural effects of employing π-type SCCS arch as the initial load-bearing element. Based on similarity theory, we perform a large-scale ring model test to investigate the mechanical behavior of the π-type SCCS arch without grouting under typical surrounding loess pressure, i.e., symmetric and asymmetric bias pressure distributions. The damage patterns, deformation evolution, and structural strain development are obtained via the experimental investigation and presented in detail. The progressive failure and ultimate bearing capacity of the hollow π-type SCCS arch are further compared under a designed loading situation. It is concluded that the failure of the π-type SCCS arch has three stages, including the coordinate deformation stage, the load-bearing stage, and the failure stage, respectively. However, the deformation and failure modes under different surrounding pressure behave differently. The stiffness and bearing capacity of the π-type SCCS arch under symmetrical pressure is 1.65 and 1.16 times greater than that under asymmetric pressure, respectively. This experimental study provides new insights into the mechanical behavior of new arch frames for loess tunnel construction, which can serve as a benchmark for further theoretical and numerical studies.

Water Vapour Resistance of Ceiling Paints—Implications for the Use of Smart Vapour Barriers in Compact Wooden Roofs

Smart vapour barriers enable building envelopes to dry toward the interior side. This property can be used in compact wooden roofs to create more slender structures by placing the wooden load-bearing elements inside the insulation layer. There is, however, some concern that the ceiling assembly on the interior side may inhibit inward drying by trapping moisture between the vapour barrier and the ceiling boards. This article examined the water vapour resistance of gypsum boards painted with two, four, and six layers of typical ceiling paints. WUFI® 2D simulations were conducted to assess the risk of mould growth in compact wooden roofs with painted board ceilings. It was found that a painted ceiling board may exhibit an equivalent stagnant air layer thickness (sd value) between 0.074 m for two layers of the most vapour-open paint and 0.53 m for six layers of the least vapour-open. For an unpainted board, the sd value was measured to be 0.071 m. The difference was not found to make a substantial impact on the drying of a typical compact wooden roof. The application of paint may cause the assembly to dry at a slightly slower rate but was not found to present a notably higher risk of mould growth, even under unfavourable conditions.

Design optimization of 3D printed concrete elements considering buildability

In this paper, we propose an integration of 3D concrete printing buildability requirements into a formal structural optimization problem. The aim is to enable the design of a structural element while balancing between its performance as a load-bearing element and its stability during the printing process. Physical buildability is quantified by stress constraints imposed on the fresh concrete, whose time-dependent strength is determined according to a rheological material characterization. This is complemented by geometric buildability that is achieved by imposing constraints on the overlap between layers. The output of optimization is the shape of the structure and the time instance at which each layer is deposited. Several prototypes were printed for verifying the numerical buildability predictions, showing acceptable quantitative agreement between theory and experiments. A critical trade-off between structural performance and buildability is exposed, that emphasizes the need for further development of holistic methodologies that integrate structural design, material design and tooling limitations.

Modeling of Stochastic Material Properties with User Subroutines in SIMULIA Abaqus

This article describes a software module component integrated with the SIMULIA Abaqus engineering analysis software package and designed to simulate random values of material parameters in a finite element model based on specified statistical characteristics, with the possibility of taking into account the physical nonlinearity of material behavior under various combinations of loads and influences. The target group of materials under study is materials of load-bearing elements of building structures, such as concrete, stone, steel. This software module can be recommended for use by specialists, engineers and scientists engaged in probabilistic analysis of the reliability of structures of buildings and structures, apparatus, machines, devices, with the combined use of complexes of computer modeling and engineering analysis. Has a certificate of state registration of the computer program «AS for modeling stochastic properties of materials» No. 2019667439 dated 12.24.2019.

A Parametric BIM Framework to Conceptual Structural Design for Assessing the Embodied Environmental Impact

Decisions made in the early design stage have a significant effect on a building’s performance and environmental impact. In practice, a conceptual design is performed by an architect, while a structural engineer begins to work in later phases when the architectural concept has already evolved. However, the geometry and form of a building directly determine the type of structure and applicable materials; therefore, the conceptual design phase gives rise to examining alternative solutions. This paper presents a method for generating alternative structural solutions in the conceptual design phase and examining their embodied environmental impact by integrating parametric design and building information modeling (BIM). Rhinoceros and Grasshopper were used to develop the parametric script, which includes the generation of geometrical variations, the automatic definition of initial cross sections for the load-bearing elements based on in-built structural design approximations, the datasets for embodied environmental impact of the used building materials, the generation of life cycle inventory (LCI), the automatic calculation of life cycle assessment (LCA) results based on the geometry, and the conversion of the parametric model into building information model. The method was demonstrated using a case study of 48 different alternative solutions for an unheated warehouse made of steel frames. Based on the results, the areas with the greatest energy impact were identified. The case study analysis also illustrated that the applied cross section may have a significant effect on the impact categories. The results draw attention to the complexity of LCA calculations even in the case of a simple structure containing a limited number of variables, where parametric design can serve as an effective tool for a comprehensive environmental impact assessment.

Testing and Numerical Simulation of the Shear Resistance of Blind-Bolted Aluminum Connections

Due to their high bending stiffness, high torsional stiffness, and high local stability, rectangular section members of Al alloy space structures are frequently utilized as load-bearing elements. However, the joint construction is more complex because of the closed cross-section. To join rectangular section members without drilling holes in them, a variety of blind bolts that can be placed and fastened on one side have been devised. The blind bolts researched in this paper is known as BOM bolt. The shear resistance of BOM-bolted Al alloy connections is investigated using shear testing and finite element calculations of individual bolts and bolt groups. According to the test and numerical simulation results, the formulas for the compressive strength of the aluminum plate and the shear capacity reduction factor of BOM-bolted long connections are derived.

Assessment of Load-Bearing Timber Elements for the Design for Disassembly

This literature review examined the functionality of the connection or connections and disassembly as a general strategy. The prerequisites that arose for disassembly were, among other things, damage tolerance, reduction of emissions compared to raw materials, costs, and guaranteeing safety. The set of criteria for disassembly was defined from the structural engineers’ perspective through the literature review. The criteria focus on joints, which are key to the success of disassembly. Five different criteria were used to evaluate joints in this study. The criteria were ease of access to components, ease of disassembly, independence, simplicity, and standardization. The evaluation was executed for different widely used connections in timber constructions. The criteria were evaluated subjectively from one to four. As a conclusion, the load-bearing timber elements have a promising future in design for disassembly. Design for disassembly aims to promote reuse and other features to increase the life cycle of structural elements. It has the potential to reduce the usage of raw materials and significantly decrease the emissions of construction.

Sizing optimisation of steel truss based on algorithms

Computational methods enable mathematical discretisation in structural design. Thus, thanks to the algorithmic design, the obtained results matrix presents various structurally efficient load-bearing elements. The main aim of this paper is to address the topic of material optimisation in truss bar structures with different approaches. The paper analyses and compares steel truss optimisation based on two software optimisation algorithms (MS Excel and Ansys Mechanical) using gradient and sub-problem methods. The key findings present how effective each method is in structural optimisation and concludes the present study with a roadmap to efficient structural designing of the load-bearing truss elements.

Effects of aspect ratios and strengthening methods on seismic behavior of masonry piers strengthened by using hybrid-fibers modified reactive powder concrete

Piers are the main load-bearing elements of masonry structures. Damage to piers in earthquakes will lead to the collapse of the whole structure, so piers need to be strengthened. In order to study the effectiveness of hybrid-fibers modified reactive powder concrete (HFMRPC) coating strengthening on masonry piers and the influence of different strengthening methods and aspect ratios on the seismic behavior of masonry structures, six masonry walls with different aspect ratios (0.8, 1.0, and 1.4) and strengthened by different methods (unreinforced, single-sided coverage in piers, double-sided coverage in piers, and double-sided cross-bracing) were tested under in-plane quasi-static loading. The test and analysis results showed that the seismic behavior of masonry walls in terms of bearing capacity, displacement ductility, stiffness, and energy dissipation was effectively enhanced by HFMRPC coating. The improvement range of ductility coefficient, initial stiffness, and cumulative energy dissipation were 86.3% ∼ 229.3%, 18.2% ∼ 104.0%, and 57.0% ∼ 139.7%, respectively. The most suitable strengthening method for strengthening piers was double-sided cross-bracing compared with other methods. The strengthening effect of the double-sided coverage in piers was improved with the increased aspect ratio. Additionally, masonry wall shear strength and flexural capacity calculation methods were proposed based on GB 50003-2011, N-M interaction diagrams, and equivalent rectangular stress block.

Engineering software development for strengthening concrete structures using fiber-reinforced polymers

In this study, engineering software for the calculations of the strengthening applications of reinforced concrete (RC) load-bearing elements with Fiber Reinforced Polymer (FRP) composite materials is developed. This software is developed to increase the axial compression strength and ductility capacity of columns and improve the shear capacity of beams using FRP material according to provisions of the Turkısh Building Earthquake Code 2018 (TBEC-2018). In addition, this software offers designers the opportunity to perform calculations to increase the bending moment capacity of beams using FRP composite material, according to the American Concrete Institute 440-2R.17 (ACI 440-2R.17). Algorithms to be used to increase the capacities of RC load-bearing elements with FRP composite materials are formed according to the provisions of the mentioned codes. Then, computer and web-based engineering software with different coding languages are developed depending on these algorithms.

STRENGTHENING OF REINFORCED CONCRETE ROOF WITH STEEL FRAME

Strengthening methods of reinforced concrete roofs are known and developed in sufficient detail. They are classified according to the constructions: strengthening of simply supported and continuous beams, cantilever beams, panels, girders, trusses, arches, etc. But all the proposed ways have common disadvantages – they require open space for work, provide for preliminary unloading, and under certain circumstances, partial dismantling of significantly damaged structures, and cannot consider the features of a specific technical situation naturally. We offer the strengthening method of not a single beam, but the entire roof block, with limited time period and the need to restart the production process in the shortest possible time, which has got critical damage, during the situation that excludes temporary unloading, and the dismantling of damaged areas or structures is impossible. The additional technical problem is that the supporting vertical structures of the emergency shutdown – the columns are also in a critical technical condition. Therefore, the attempt to dismantle any load-bearing element will lead to the complete destruction of a large part of the industrial building and the cessation of production for a considerable time period. The use of a spatial steel frame simplifies the strengthening work, speeds up the return to production and does not increase the material costs

Out of Plane Offset in Multistoried Buildings: Analysis and Significance for Best Possibility Model Case

Abstract: The phenomenon of out of plane offset in multistoried buildings has gained significant attention in the field of structural engineering. Out of plane offset refers to the vertical displacement or misalignment of structural components, such as walls or columns, in relation to the main vertical load-bearing elements of a building. This research paper aims to investigate the best possible strategies associated with out of plane offset in multistoried buildings. For this, total 6 possibility model cases with one additional case of 1.1 has made and all 7 cases analysed. When compared the result parameters, it has found that the possibility case 6 performs best among all and should be recommended that always use out of plane offset at top floors only.

Developing a method of accounting for the existence of local surface heat exchange in rods of variable cross-section

The load-bearing elements of a number of strategic equipment are of limited length and variable cross-section. Most of them are exposed to certain types of heat sources. In order to ensure the reliable operation of this equipment, it is necessary to know the temperature field along the length of the variable cross-section rod. In this paper, a computational algorithm and a method for determining the temperature field along the length of a rod with a limited length and variable cross-section are proposed. They are based on the fundamental laws of conservation of energy. The nonlinearity of the process is due to nonlinear dependencies of the areas of the variable cross-section on the coordinate. The radius of the cross-section of the rod decreases linearly along the entire length, starting from the left end. The side surface of the first and third discrete elements of the rod is heat-insulated. Convective heat exchange with the environment takes place on the side surface of the second discrete element of the rod. The cross-sectional area of the left end of the rod is under the heat flow with a constant intensity, and a heat flow with different intensities is supplied to the right end, wherein the heat transfer coefficient is considered constant. For this task, you must first determine the law of temperature distribution along the length of the rod. In addition, if one end is rigidly fixed and the other end is free, the elongation must be calculated depending on the available heat sources, the physical and geometric characteristics of the rod, taking into account the presence of insulation. In case of pinching of both ends of the investigated rod, the value of axial compressive force is calculated taking into account the addition of real factors. The distribution of all components of the strain, stress, and displacement field is also defined

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.

Research of frogs point wear resistance in various conditions for transportation systems: main-line railway and subway

The experience of operating switches shows that load-bearing elements fail for two main reasons: defects and wear. The percentage failure of elements due to one reason or another depends on the operating conditions in which they operate. In this case, the most worn elements of switches are pointers and point frogs and their service life is determined by the amount of tonnage passed through them before reaching the standard values of wear or the appearance defects. The article is devoted to the study of wear resistance of switches operated in various transport systems, namely, mainline transport and subways. The article considers the issues of predicting the standard service life cross elements of typical angles using operational studies for subway conditions and a new theoretical methodology based on the analysis of switches withdrawn from operation after they reach the standard wear values for mainline transport. For analytical calculations, the method of modeling the interaction process and graph-analytical methods were used. As a result of the study, the analytical equations predictive curves for the formation vertical wear as a function of the passed tonnage for the switches point frogs operated on lines of mainline railway transport and the Kyiv subway were established.