Structural Elements Of Buildings Research Articles

Determination of Changes in the Parameters of Electrical Machines after Repairs to Prevent an Unacceptable Increase in Vibration of the Building Structure

This article discusses the improvement of control methods for electrical machines after repair. These methods allow during testing of an electric machine to determine deviations of parameters that can lead to an increase in the level of vibration and subsequent failure of both the machine itself and the elements of building structures.

Low-cycle fatigue behavior of 3D-printed metallic auxetic structure

Auxetics occupy a special place among structural products working under cyclic loads, such as orthopedic implants, elements of building structures, etc. In this work, a three-dimensional auxetic structure (with Poisson’s ratio of −0.450) was proposed and the mechanical characteristics were analyzed using static and low-cycle compression tests (up to 2000 cycles) by both testing physical samples obtained by 3D-printing using SLM method and by running a computer simulation (FEA). The studied properties of auxetics were compared with the properties of a non-auxetic hexagonal honeycomb structure. It has been demonstrated that the auxetic structure is deformed uniformly during cyclic tests with a maximum load of 12 kN at a failure; accordingly, a non-auxetic structure loses stability at a load of 8 kN. The results can be used in the development of structural elements of biomedical devices operating under increased cyclic loads (spinal implants, bone implants for supporting limbs).

Трансформация исторических зданий в Санкт-Петербурге и сохранение архитектурных и конструктивных элементов различных периодов

The article deals with the process of transformation of Saint Petersburg buildings in the period of the XVIII-XX centuries. The buildings of the city center have been rebuilt many times, and behind the facade designed in a specific style there may hide walls referring to various historical periods. The value of a building is determined not only with its architectural and spatial characteristics, but also with building materials and structural elements used. Specific cases of transformation of buildings` facades over time are analyzed on the examples of buildings located on Millionnaya Street and English Embankment. The issue of preserving, exhibiting, and museumifying structural elements is raised.

Modification of the structure of gypsum-cement-pozzolanic binder

Modification of the structure of gypsum-cement-pozzolan binder allows you to expand the range of gypsum binders for creating dry building mixes and structural elements of low-rise buildings. It was found that in the presence of functional additives, the character of crystallization of hydrate neoplasms changes, which leads to a change in the properties of the hardened binder. The study of the effect of individual and complex additives on the properties of gypsum-cement-pozzolan binder allowed us to develop water-resistant gypsum binders.

Integral monitoring of high-rise buildings while minimizing the number of sensors

Considered current issues of automatic monitoring of high-rise buildings. A review of currently implemented monitoring methods is given. An analytical study of the effect of the ratio of the rigidity of the vertical and horizontal structural elements of buildings of various structural systems on the deformation of the vertical axis of the building was performed. The basis of the research is the solution of the differential equation of the elastic vertical axis of the building. By finding the extrema of the deformation function of the vertical axis, critical points of control of its angles of rotation are determined. As a result of the study, it was concluded that it is advisable to minimize the number of control points, with limited control at certain critical points. The position of the control points dividing the vertical axis of the building through ¼ of its length at the corners of the perimeter of the floors has been determined. It is shown that minimization is necessary due to difficulties in processing and analyzing big data (Big Data). As a result of the traditional manual calculation with the accepted design methods, it was found that the box-barrel structural system has the greatest deformations, the frame-link frame with the stiffness core has the smallest deformations, and outriggers do not always allow to radically increase the building stiffness. Studies were conducted on computer models of the same types of buildings, which confirmed this dependence. However, here the maximum rigidity was shown by the cross-wall model. This testifies to the features of modeling buildings in various ways and confirms once again the need to monitor not only high-rise buildings, but all non-standard ones. It is concluded that it is necessary to accumulate data on the deformations of buildings using automatic monitoring methods. It is shown that information on the technical condition of the building is complemented by information on the longitudinal deformations of vertical structures - columns, stiffness cores, measured by tensiometers on concrete, as well as dynamic stiffness, determined by the natural oscillation frequency of accelerometers. The principle of sensor grouping and the need to use integrated, integrated monitoring are shown.

Cost Comparison of a Building Project by Manual and BIM

This article focuses on comparison between Manual/Traditional and Building Information Modelling (BIM) software based approaches for cost comparison. Centre line method for manual and Revit software for BIM based approaches are used in this research. The principal objectives of this research are to calculate quantities by Manual Centre line method, then to make the cost estimation fast, accurate, efficient, and errorless by using BIM software Rivet, and finally the comparison study of manual based and BIM / Software based estimation. For manual approach, quantities are calculated by multiplying the measurements of length, breadth, and height. Then to get the total quantities the deduction is subtracted from the quantities and final BOQ is prepared for which estimated cost of building is calculated. For BIM based approach, 3D model from 2D floor plan of building is prepared in Revit software, then to estimate the cost of building structure elements, sheets of quantities are generated in the schedule option of the view tab in the software. The Percentage difference between Manual and BIM / Revit Software estimation in brick work, RCC Slab, Plaster Work, PCC for Flooring, Floor Tile Work, Skirting, Paint Work, False Ceiling, Doors and Aluminum Work is 4.57, 2.61, 7.58, 3.27, 1.87, 6.73, 8.03, 1.87, and 0.00% respectively. The total cost difference between manual and BIM based estimation approach comes out to be 4.8%. It is thus concluded that the BIM-assisted estimates have better performance over traditional/manual estimating methods.

EVALUATION OF MONITORING THE PROCESS OF DEFORMATION AND SEDIMATION OF A RIGHT LINE VERTICAL ROD

Elements of building structures (EBS) undergo various kinds of deformation as a result of force and temperature effects. As long as the deformations are within the design values, they are not terrible for the structures of the structure, however, if they exceed the permissible values, then there may be a danger of their operation. Therefore, many large, complex, critical structures are constantly monitored by engineering geodesy methods and using sensors of deformations, displacements, tilts, etc.On the example of a vertical rod made of low-carbon steel, which is rigidly fixed and deformed as a result of subsidence of the lower base, the calculation of the accuracy of measuring the tensile strain is calculated, provided that it allows you to track the elastic limits. The calculation shows that the accuracy of measuring the tensile deformation of low-carbon steel is very high and can increase even more for metals of increased strength and with a different (less pronounced) tensile diagram. But modern devices can measure deformations with such precision. Such devices in the form of strain gauge networks are included in the general geodetic monitoring system.

Geometric rigidity of torsion of thin-walled pipes: theory and experiment

Thin-walled rods as structural elements of buildings, structures and machines that absorb torsion deformations are widely used in construction and engineering. Development of analytical methods for solving the problem of torsion of rods of non-circular cross section is one of the most important modern problems of construction mechanics. When solving torsion problems, the geometric rigidity of the section Ik is primarily determined. The analysis of the considered literature sources showed that the study of the problem in question using the isoperimetric properties of cross-sections of rods is very effective. In the present paper, for thin-walled pipes with an arbitrary convex contour and constant wall thickness, the authors obtain calculation formulae that associate the reduced geometric rigidity of the cross-sections of the pipes Ik with their form factor. It allows formulating the isoperimetric properties of the parameter under study depending on the shape of the pipe sections, and using geometric methods to determine the geometric rigidity of the cross-sections of pipes of arbitrary shape and a convex contour. The article also contains the results of experimental studies of triangular pipes confirming this isoperimetric relationship of the reduced geometric rigidity of pipes with the form factor.

Comparison on reinforced concrete bar strengthening using CFRP method, the IWF bar support addition, and bar dimension enlargement

Structure failures often happen whether caused by bad implementation, especially at reinforced concrete bar. Failures on building structure elements might be caused by several factors such as planned age of use, transformation on function, and even improper construction procedure. Thus, the reinforced concrete bar strengthening is required especially on a 10 m bar. This study focus is about comparison on strengthening the original structure of the building using the CFRP method which overlaying the bar surface, adding the IWF bar as a cantilever from below of the desired structure, and enlarging the bar dimensions. The result of the study shows that using 5 m2 CFRP overlaid on flexible reinforcement and 2.5 m2 CFRP overlaid in shear reinforcement get the results in Mn = 207.82 KNm and Vn = 146.33 Kn. Furthermore, additional 400, 400, 13, 31 IWF bar for the strengthening result is in Mn = 1045,32 KNm and Vn = 809,79 Kn. Dimension enlargement to 650 mm x 350 mm of 4D16 reinforced concrete and P10-250 mm reinforced cross-bar resulting in Mn = 529,23 Knm and Vn = 78,56 Kn. Effectiveness analysis is done to select the most effective method considering its strength gained and the cost that required.

Use of generalized finite difference method for calculation of beams from nonlinear elastic material

The introduction into practice of construction of structures made of high-strength steels and other materials having a nonlinear deformation diagram caused the active development of the nonlinear theory of calculation of structures. Replacing Hooke’s law with nonlinear dependencies between stresses and strains leads to so-called physical nonlinearity. For the calculation of such structures, the experimentally obtained dependences between stresses and strains are described using analytical expressions. A number of variants of such approximations have been proposed by various researchers. In this paper, we consider the calculation of beams of symmetrical cross-section made of nonlinear elastic material, for which the dependence between stresses and strains is described by a cubic parabola. This approximation ensures the symmetry of the diagram σ with respect to the tension σ – ɛ compression, and also gives a good match with the experimental curve. The use of the generalized finite difference method for solving the problem allows to reduce the system of nonlinear differential equations to the system of algebraic equations, for the solution of which the method of successive approximations is used. Studies have shown that the proposed method of calculation makes it possible to obtain a fairly accurate solution for a small number of elements. In addition, the presented calculation algorithm is convenient for programming and numerical calculation. As an example of systems that allow calculation using the considered algorithm, beam elements of building structures can act. The calculation of a beam from a nonlinear elastic material on the action of a concentrated force is given.

Comparative energy analysis from fire resistance tests on combustible versus noncombustible slabs

SummaryStandard fire resistance tests have been used in the design of structural building elements for more than a century. Originally developed to provide comparative measures of the level of fire safety of noncombustible products and elements, the recent resurgence in engineered timber construction raises important questions regarding the suitability of standard fire resistance tests for combustible structural elements. Three standard fire resistance floor tests (5.9 m × 3.9 m in plan), one on a concrete slab and two on cross‐laminated timber (CLT) slabs, were undertaken to explore some of the relevant issues. The fuel consumption rate within the furnace was recorded during these tests, and the energy supplied from this was determined. An external fuel supply (from natural gas supplied to the furnace) equating to approximately 3 MW was recorded throughout the concrete test, whereas this was about 1.25 MW throughout the CLT tests. The total heat release rate was calculated using carbon dioxide generation calorimetry; this yielded values of approximately 1.75 MW during the CLT tests (ie, an additional energy contribution of approximately 0.5 MW from the timber). This demonstrates that considerably more energy input (by about 1.25 MW) was needed to heat the system when the test sample was noncombustible. A further series of six large‐scale compartment fire experiments (6 m × 4 m × 2.52 m) was undertaken to further explore comparative performance of combustible versus noncombustible construction when the external fuel load is kept constant and is governed by more realistic compartment fire dynamics. For a fuel‐controlled case, the peak temperatures in the compartment with an unprotected CLT ceiling were approximately 200°C higher than in the compartments with a concrete ceiling, whereas for a ventilation‐controlled case, the compartment with a CLT slab ceiling displayed a burning duration that increased by approximately 15 minutes. Potential implications for standard fire resistance testing of combustible specimens are discussed.

Treatments and modification to improve the reaction to fire of wood and wood based products—An overview

SUMMARYWood and wood‐based products are widely used for structural building elements, but due to their composition, they are susceptible of combusting if exposed to fire. Fire safety is an important issue of building safety, especially when the building's fire load contents enhance the risks of fire spread. Therefore, the involved materials are very important to address the fire safety requirements. When existing timber structures are involved, the most usual way to improve its reaction to fire is to treat wood with fire retardant materials.The idea of this paper is to give an overall overview, on the existing fire‐retardant and intumescent coating materials, modification, and treatments that can be applied to wood and wood‐based products in order to improve their reaction to fire.

Parametric identification of multy-storey building model based on oscillation testing results

Buildings and structures are complex systems having predetermined parameters, which should be controlled in the process of manufacturing structures, construction and installation. In some cases, oscillations are the most dangerous effects on the buildings and structures. Significant alternate stresses caused by oscillational actions leads to accumulation of damage in the material. It causes the appearance of fatigue cracks and destruction. In addition to fatigue failure in mechanical systems there are other phenomena that cause changes in the structure of the surface layers of the parts to be joined and consequently the reduction of the frictional force in the joint. The object of the study is a multi-storey building having a rectangular shape in plane. Structural scheme of the building is a two spans frame. The frame of the building consists of monolithic reinforced concrete structures. According to the analysis of the basic diagnostic parameters of the technical condition of buildings and structures, affect their stability and reliability are geometrical parameters of buildings and structures, and their main structural elements, as well as physical and mechanical parameters of structural elements of building and dynamic parameters of buildings and structures. An analysis of methods for determining the dynamic parameters of buildings has shown that the main criteria for assessing the technical condition of bearing structures, using the dynamic method, is the period and frequency building oscillation. Dynamic tests were conducted to determine the dynamic and rigid characteristics of bearing structural elements of the building and structures, detection of hidden defects. According to the method of measuring the dynamic parameters, the degree of damage to a building or structure, is determined by the comparison of the design values of dynamic parameters, periods of eigenoscillations, and the decrement of oscillations with experimentally obtained data.

Fiber-optic sensors for monitoring the stress-strain state of construction objects

For the timely detection of significant changes in the stress-strain state in the bearing elements of various building structures, which may lead to a deterioration of the technical condition of the object or transfer it to the emergency state, the use of fiber-optic sensors is proposed. The main advantageous characteristics of fiber-optic sensors, describing the promise of their application for practical applications, are disclosed. As a parameter recorded by the measuring transducer, the fiber-optic sensors use the intensity of the light wave. The mechanism of changing the optical intensity can be due to reflection, absorption, refraction of light rays passing through the measurement zone. The authors have developed a fiber optic attenuator type deformation sensor capable of controlling mechanical deformations of structural elements caused by disturbed internal geometric characteristics, destruction of structural integrity and negative influence of external weather conditions, seismic factors, temperature drops during operation. When developing the design of a fiber-optic sensor, the fundamentals of circuit design of measuring devices, methods of geometrical and fiber optics are used. As a basic measuring transducer, a fiber-optic microdisplacement transducer with a limiting attenuator is used, in which the intensity of the optical signal is modulated by changing the position of the attenuator placed in its path or increasing the optical power. A design-structural diagram of a fiber-optic micro-displacement measuring transducer and a block diagram and the design of a new sensor are presented. The principle of operation of an attenuator-type fiber-optic strain gauge is described.

Damage assessment of squat, thin and lightly-reinforced concrete walls by the Park & Ang damage index

Damage progression indexes are widely used to evaluate the performance of structural elements in buildings and bridges subjected to seismic actions. Although the Park & Ang damage index is currently implemented in several computational tools, the index has not been calibrated for squat and thin reinforced concrete (RC) elements controlled by shear deformations. It has been observed that the equations originally proposed for the Park & Ang damage index are unsuited for these types of structural elements, which are characterized by a failure mode dominated by shear instead of flexural deformations. The index was evaluated in this study for squat, thin and lightly-reinforced concrete walls using experimental data from a program comprising monotonic and reversed-cyclic load testing of 25 RC squat cantilever walls. The experimental program included walls, with and without openings, having height-to-length ratios equal to 0.5, 1.0 and 2.0. Full-scale wall thickness and clear height were 100 mm and 2.4 m, respectively. The specimens were built using three different types of concrete (normal-weight, light-weight and self-consolidating) with nominal compressive strength of 15 MPa. A novel formulation for the parameter β included in the Park & Ang damage index was proposed in this study using key variables of the wall specimens such as web reinforcement ratio and cumulative ductility. Comparison between the computed damage index and crack pattern evolution observed in wall specimens at different damage states demonstrated the ability of the model to numerically assess the damage of the wall specimens. Hence, this new formulation proposed for parameter β leads to a better estimation of damage for this particular type of elements when applying the broadly used Park & Ang damage index.

ВЛИЯНИЕ ВЫСОТЫ ПОПЕРЕЧНОГО СЕЧЕНИЯ И ХАРАКТЕРА АРМИРОВАНИЯ ДЕРЕВЯННЫХ КЛЕЕННЫХ БАЛОК НА РАСПРЕДЕЛЕНИЕ ВНУТРЕННИХ УСИЛИЙ

The main trends of modern construction is the production and use of light construction structures, which can significantly accelerate the construction of building objects. At the same time, the use of structural and finishing materials that meet modern environmental requirements is important. Structural elements of buildings have dominated for many centuries and have broad prospects for use in modern capital construction: they have high strength and rigidity; they are reliable and durable and have a low installation weight. In particular, in a number of Western countries, high-rise buildings are already being built using a frame made of glued wooden structures. Despite the natural symmetry of coniferous woods structure, its non-standard tracheids are the main reason for the variability of its mechanical properties. In addition, when calculating glued reinforced structures, it is necessary to take into account the so-called "scale effect" when calculating the bent glued wooden elements. The applied methods for the calculation of "low" reinforced beams sometimes give an error in the calculation of "high" beams. In this paper, the definition of a more rational method of calculating the "high" beams with symmetrical reinforcement and comparison of options for reinforcing such beams are performed

An automated standard-based life cycle quality inspection methodology for smart precast concrete solutions in buildings

ABSTRACTBuilt2Spec research project brought together a new and breakthrough set of tools in order to improve construction quality inspection processes. These can be put into the hands of construction stakeholders to help meet Europe’s energy efficiency targets, standards for constructing and retrofitting buildings, and related policy ambitions. This paper focuses on the automated standard-based life cycle quality inspections for precast concrete structural building elements that can be enhanced by leveraging a range of different technologies. Particular attention is placed on the use of embedded sensors in the precast concrete structural building elements as a tool to support quality assurance of these elements. Starting with the design, through manufacturing, delivery to site, installation, commissioning and operation until the end of life, the performance of precast concrete building elements is monitored and controlled to ensure their compliance with specifications, standards and guidelines. The outputs of proposed technologies integrated within the virtual construction management platform (VCMP) can enable automated continuous quality checks, while making them accessible to stakeholders through the life of a building. The measurements to support the development of this methodology were provided by a newly constructed demonstration building in Ireland.

Analysis of local deformation effects in cold-formed tubular profiles subjected to bending

Application of high-strength steel can serve improving structural efficiency as well as solve structural problems when traditional materials are inapplicable due to strength limitations. Innovative structural solutions, however, are facing problems related to the absence of corresponding design procedures and reliable constitutive models. Cold-formed profiles are frequently used as structural elements in buildings. The enhancement of a material strength in the profiles with nominal geometry increases slenderness of the cross-section that can cause a local increase of deformations due to high stress concentrations. The increase is a consequence of web crippling often followed by failure of the flange. The investigation of the combined web crippling and flange failure effects is rather complicated due to localized deformed behaviour that is not a trivial subject for experimental identification. The premature deformation increase in a critical cross-section is not necessarily caused failure of the profile that continues to carry further loads. This paper investigates local deformation effects in cold-formed square tubular profiles subjected to bending load. A four-point bending test was used to estimate the effect of local nonlinear deformation on the overall deformation behaviour. The profiles made of high strength steel S700 and S900 grades were considered. Similar profiles made of the steel S355 were tested for the reference. A digital image correlation system was used to monitor deformations of the web surface. A nonlinear finite element model was developed to investigate the local deformation effects on the overall deformation behaviour and load-bearing capacity of the profiles. The model was customized with the reference to the experimental results. After the verification, it was used to illustrate deformation analysis procedure of a continuous tubular beam.

Research of the stress-strain state of cylindrical elements of engineering constructions of special purpose under the effect of temperature load

Active development of monolithic-frame construction in the recent period of time requires a new approach to the calculation of elements of building structures. Concrete columns are one of the most important elements of such buildings, the failure of which is of great durability. Loss of strength characteristics of the column may occur as a result of the loads caused by the effect of temperature fields. Therefore, research related to the influence of temperature on the supporting elements of structures of military objects, is relevant and of great importance.The non-stationary temperature field in a cylindrical concrete column, which changes over time under high temperatures, is investigated. When modeling the heating process of a column, the boundary conditions of the third kind are taken into account. Using the Laplace transform, we obtained analytical expressions for the research of a temperature field. The stress-strain state of the column with pinched and free ends is determined, which is caused by a non-stationary temperature field, where various values of the heat transfer coefficient between column and the environment were taken into account.One of the most significant causes of increased danger for such structures is uneven heating and changes in the characteristics of strength and deformability of concrete during and after the fire. At the same time it is necessary to solve the issues connected with ensuring sustainable and reliable operation of building structures, including the influence of high temperatures, due to the adoption of appropriate materials or protective coatings. Thus, mathematical modeling of the processes of temperature fields in a stress-strain state of cylindrical structures can significantly increase accuracy of calculations, which contributes to the strength and reliability of engineering structures. The graphic dependences of radial, ring, and axial stresses from the radius are researched as a result of the temperature fields of different intensity on the rod elements are obtained and we have found radial displacement at different temperature.

Whole timber construction: A state of the art review

Abstract Forests worldwide are overstocked with small-diameter trees, putting them at increased risk of disease, insect attack, and destructive high-intensity wildfires. This overstocking is caused primarily by the low market value of these small-diameter trees, which are generally unsuitable for sawn timber production and yield low prices when sold for biomass fuel, paper, or fibre-based engineered timber products. Considerable research in recent decades has demonstrated the potential for these small-diameter trees to be used in minimally processed round segments as structural elements in buildings, bridges, towers, and other infrastructure. Recent structures have also demonstrated the use of trees with major curvature and branching, which are also of low market value, in their round form as primary structural elements. Such “whole timber” construction serves as a low-cost, low-impact building system while providing revenue to forest owners to conduct harvests of low-value trees as required for sustainable forest management. This paper reviews developments in whole timber construction, presenting new non-destructive evaluation techniques, digital survey, design and fabrication methods, new processing technologies, and a diverse range of novel connection types and structural systems. It is shown that the key materials characterisation, processing, and design challenges for whole timber construction have been largely addressed, and that whole timber has the potential to be an important complement to other timber products in construction globally in the coming decades. It is recommended that future work focus on exploiting new digital technologies and scaling whole timber structural applications through increased prefabrication.