Construction Of Structural Elements Research Articles

Fire behavior of high‐contents recycled aggregate concrete composite slabs with small openings

AbstractRecycled aggregate concrete (RAC) is increasingly being used in the construction of structural elements. However, the performance of RAC elements under fire is usually considered to be inferior to that of normal concrete (NC) elements. This study investigates the fire behavior of RAC composite steel slabs with and without openings. Ten slabs of size of 1.0 m × 2.2 m were cast either with no opening, one or two circular openings, and one or two square openings. Five of the slabs were manufactured with 100% RAC, while the other five slabs were made with NC. The concrete slabs were loaded and subjected to fire tests at a temperature of about 900°C for 120 min. Test results show that RAC composite slabs have lower stiffness (thus larger mid‐span deflections) under fire exposure compared to their counterpart NC slabs. In terms of the recorded temperature–time curves, RAC slabs showed similar performance to that of NC slabs. The ratio of soffit temperature to the temperature at the top of slab was considerably smaller for RAC slabs compared to NC slabs. RAC slabs also showed more spalling than NC slabs. Experimental test results were numerically verified using PyroSim® software with the two showing good agreement. A series of new design charts for composite RAC slabs with desired fire endurance are proposed. This study is expected to promote the wider use of RAC in construction of structural elements, particularly of composite slabs exposed to extreme temperatures.

Модель формирования протокольных блоков данных управляющих сообщений канала управления динамическим изменением параметров сигналов абонентских терминалов

The article presents a model of formation of protocol data blocks of control messages of the control channel for the dynamic change in signal parameters of subscriber terminals of satellite communication systems. The model takes into account the dynamic distribution of the frequency-time resource of user terminals and the change in the number of simultaneously functioning subscriber terminals in the group signal. The basic principles of functioning of satellite communication systems with dynamic change of signal parameters are considered. The description of the structure of protocol data blocks of control channel messages and their main structural elements is presented. The issues of variability in the construction of structural elements of control messages of protocol data blocks of the control channel are considered. The number of possible alternatives to the structure of protocol data blocks of channel control messages was estimated. The results obtained on the basis of modeling can be used to identify data blocks of control channel messages and determine the parameters of user terminal signals for further reception and processing.

Optimization of the organization of the construction process of structural elements of monolithic buildings

The modern construction market dictates strict rules for labor productivity, product quality, optimality and cost-effectiveness of processes. The need for a tool to optimize the organization of the construction of structural elements of monolithic buildings is a significant issue in the construction process. In the field of organization of construction production, the main role is played by the organizational and technological decisions that have a direct impact on the processes and results of construction activities. Optimization of the organization of the process of constructing structural elements, which is the possibility of reducing the construction time of structural elements of monolithic buildings through the use of effective organizational and technical solutions, or by adjusting inefficient organizational and technical solutions characterized by a complex quality indicator, is an urgent task in the field of research. Thus, the goal of optimizing the organization of the process of constructing structural elements is to reduce the duration of work and reduce labor costs. Based on the results of field observations, the influencing factors determined on the parameters that affect the organization of the erection of structural elements of monolithic buildings have been established. The necessity of taking into account all the main influencing factors of the model in order to achieve an objective characteristic of the effectiveness of the organizational process is noted. A possible direction for the development of the study is to expand the scope of application of the results of the study in the organization of various construction processes. The expansion of statistical data, computerization and programming of organizational structures in the construction process remains an urgent task for the development of the direction.

КОНЦЕПЦИЯ «УМНОГО НЕФТЕСКЛАДА» НА ОСНОВЕ ТЕХНОЛОГИЙ МАШИННОГО ЗРЕНИЯ

The paper considers and solves the issues of the formation of algorithms and practical methods for the application of machine vision in the concept of a smart oil storage. The resulting technology will significantly increase the autonomy of intelligent algorithms for managing the tank farm and ensure its safe operation. The fundamental principle of the development of the bionic approach in machine vision is the use of artificial neural networks to recognize objects from the received images. The solution to the problem of visual perception with the help of a computer was the development of artificial neural networks and algorithms for their training. To increase the autonomy of intelligent algorithms for managing a tank farm and ensure its safe operation, it is necessary to develop algorithms and practical methods for using machine vision in the framework of an intelligent oil storage unit. The results of measurements of a steel surface horizontal tank by a neural network based on the image from the camera are obtained by spatial transformation of its image and construction of structural elements using the contour segmentation algorithm. The initial representation, from which the mapping is carried out to some final representation, is usually the representation of the image in the form of an array of raw data - a set of results of physical measurements made for some image from the camera. A picture from a camera contains, in terms of computer vision, a set of physical objects or some fragment of the real world, in our case, a ground horizontal cylindrical tank. The smallest image element with such an initial representation is a pixel containing the result of a single measurement of a given physical quantity. The result obtained was: tank height 2.05 m, tank length 3.17 m, diameter 2.25 m. The measurement error in this case is 4.5%.

GEODETIC SUPPLY FOR THE CONSTRUCTION OF ENGINEERING STRUCTURES

The construction of engineering structures when transferring the project to the area is impossible without geodetic work. The composition and sequence of engineering and geodetic works depend on the features of the design and construction of facilities and the type of structure. The purpose of the article is to consider geodetic works in the construction of engineering structures. The issues of performing engineering and geodetic works during the construction of structural elements of the bridge are considered. During the construction process, it is necessary to ensure full compliance with the design documentation and high accuracy of work performance. These requirements can be achieved by using high-precision geodetic works with constant monitoring of the installation work. At all stages of the bridge construction, geodetic works accompany the transfer to the terrain of the bridge axis, the resistance axis, perform a detailed breakdown during the construction of resistances and the installation of purlins. Also, the construction of individual parts of the building is constantly monitored, the dimensions and shape of the mounting elements are checked. When building large structures, it is necessary to have information about the points of the geodetic base of the bridge crossing, an extract from the catalog of coordinates and elevations of the geodetic base. The breakdown is carried out by tying to the points of the geodetic reference network, which has coordinates in the absolute or conditional system. Modern construction requires the use of new technologies and methods for performing geodetic work related to the introduction of electronic devices and programs for automated information processing into geodetic practice. Currently, a large number of geodetic instruments and new technologies in geodesy have been created, which differ from traditional ones. To carry out survey work, geodetic instruments, such as electronic total station and levels, were used. The electronic total station measures distances, angles and processes data directly in the process of field work, has an internal memory where it can store all the data obtained as a result of measurements. The digital level has a device for automatic registration of measurements along the rail and a processor for subsequent processing of all leveling results. During measurements, the device measures the distance to the rail and the elevation between points. This eliminates two main types of errors: observation errors when taking a reading and error in distance measurements. During the construction of supports, a temporary rapper is installed on each of them, which is tied to permanent rappers by leveling moves. The removal of marks on the supports is carried out by methods of geometric or trigonometric leveling. The coordinates of the rappers were received and entered into the local plan. Marks for serifs of the device with a retroreflective effect were pasted on the bridge supports. The data of coordinates and heights were entered into the total station memory. Geodetic work carried out during the construction of the span structure ensures the accuracy of its assembly in accordance with the project. After the installation is completed, the assembly results and deviations from the project are monitored. The construction of structural elements of engineering structures must comply with building codes and geometric parameters of the facility design.

Construction of Structural Elements and Characteristic System of Athletes’ Cognitive Ability

Construction of Structural Elements and Characteristic System of Athletes’ Cognitive Ability

Entropy-Driven Morphological Top-Hat Transformation for Infrared Small Target Detection

Infrared small target detection is a key technique in an infrared system. In the past decade, many methods have concentrated on traditional top-hat transformation, which relies on the hand-crafted shape and value of structural elements. However, these methods are inevitably challenged by the following two aspects: first, the structural elements cannot suppress heavy clutter because the construction of structural elements is always according to the prior information of the target and unable to consider the feature of clutter. Second, adaptively extracting sufficient local feature information for background suppression is hard for the structural element. In this article, we propose an entropy-driven top-hat transformation with guided filter kernel for considering the features of both the clutters and background. First, we propose an entropy-driven top-hat transformation method with our proposed local mean entropy, which can be used to suppress clutter according to the local complex degree of clutter. Then, an adaptive structural element based on a guided filter kernel is further exploited to capture the local feature information of image for background suppression. Finally, an adaptive threshold is combined with our algorithm to achieve target detection in image sequences. The experimental results show that the proposed algorithm is not only robust for suppressing different kinds of backgrounds but can also obtain a higher value of the signal-to-clutter ratio gain and detection accuracy compared with some popular traditional baseline methods and related top-hat methods.

Ductility Enhancement of Sustainable Fibrous-Reinforced High-Strength Lightweight Concrete.

To limit the cross-sectional size of concrete structures, high-strength, lightweight concrete is preferred for the design and construction of structural elements. However, the main drawback of high-strength, lightweight concrete is its brittleness over normal-weight concrete. The ductility of concrete is a crucial factor, which plays an important role when the concrete structures are subjected to extreme situations, such as earthquakes and wind. This study aims to improve the ductility of high-strength, lightweight concrete by incorporating steel fibers. The palm oil clinker (POC)-based, high-strength, lightweight concrete specimens reinforced with steel fibers were prepared and their ductility was systematically examined. POC was used as aggregates and supplementary cementitious materials. Steel fibers from 0–1.50% (by volume), with an increment of 0.5%, were used in the concrete mix. Compression ductility, displacement ductility and energy ductility were used as indicators to evaluate the enhancement of ductility. Moreover, the compressive strength, flexural strength, stress-strain behavior, modulus of elasticity, load-displacement characteristics, energy absorption capacity and deformability of the concrete samples were investigated. The compression ductility, displacement ductility and energy ductility indexes were found to be increased by up to 472%, 140% and 568% compared to the control specimens (concrete with 0% steel fibers), respectively. Moreover, the deformability and energy absorption capacity of the concrete were increased by up to 566% and 125%, respectively. Therefore, POC-based, high-strength, fibrous, lightweight concrete could perform better than conventional concrete under extreme loading conditions as it showed significantly higher ductility.

An analytical study of strengthening conventional concrete by replacing it with rubcrete concrete

Abstract In recent times, Non– Bio Degradable waste has been a major problem in World. In our Day-to-Day life due to increased consumption of the materials like Plastic, Rubber, Glass in Domestic and Industrial activities in rapidly developing countries like India, USA, Germany etc., it has been creating major harm to the Environment. About 6.3 billion tons of plastic waste, 3.5 billion tons of Rubber waste has been generated in the world so far. If this continues, then our future generations will have to face many serious problems. The probable solutions to reduce their damage to the Environment are either reducing their usage in daily times or recycling them. The first choice is inevitable, as we are habituated using these products. It is possible to adopt the latter. Using proper techniques, Rubber and other materials could be used in construction and other activities by adopting latest technologies. Our research is about, how we could properly use the Scrap Rubber as a Replacement material to Coarse Aggregate in Concrete and minimize the use of Coarse Aggregate. Concrete is a versatile, legendary and supremely strong material which is manufactured with the combination of Cement with Aggregates and Water. It is used in Construction of Structural Elements like Foundations, Columns, Beams and Slabs. It has been ruling the Construction industry since mid 1800‟s. By Replacing Coarse Aggregate with Rubber, it will save the Environment against Pollution from Rubber and Extraction of Aggregates through Quarrying. This will be a major boon towards the Environment. The Concrete obtained by Replacing Coarse Aggregate with Rubber can be called as RUBCRETE. Cost analysis comparison is also done in this paper for rubcrete concrete and conventional concrete.

Effects on Reinforced Concrete Slabs by Environmental Loads

Throughout the development of accelerated testing procedures, the behavior of pure concrete specimens was evaluated for a comparison in the different effects that are generated between concrete specimens with resistance to the compression of 20 MPa (200 kg/cm2) regarding water/cement (w/c) 0.62, being this compressive the employee minimum value according to Mexican regulations and which is currently used in the construction of structural elements of the housing and specimens with compressive strength of 25 MPa (250 kg/cm2) with ratio water/cement (w/ c) of 0.55, considering that this resistance corresponds to the recommended minimum value according to criteria of durability in coastal areas to the same regulations. The different concrete structures early deterioration has been the cause of constant study in recent years, finding that their durability differs as specified in the Mexican regulations. Damages that occur in elements directly exposed to environmental influences, as in the case of roof slabs, are attributed, mainly, to errors and defects in the design stages or execution in the construction process and not to the effect of these charges. Visualizing the effect of conditions of moisture, temperature, and solar radiation on this type of structure requires years of direct observation. The mass loss and degradation of the exposed surface, as well as the penetration of the carbonation front, were established as measurement parameters. The significant mass loss registred was 0.374% in the specimens with an f’c of 20 MPa and a minor value of 0.046% in the specimens with an f’c of 25 MPa. Regarding the carbonatation front, a value of 10.7 mm was registered in the short edges of the trial specimens with an f´c of 20 MPa and 7.3 mm for the specimens with an f´c of 25 MPa. Even though the mass loss percentages were less than 1%, and considering that carbonatation triggers corrosion processes that lead to the early deterioration of reinforced concrete structures, the results obtained indicated that the increase to the compressive strength by decreasing the w/c relation, besides favoring the concrete mechanical properties, it can also increase its durability; demonstrating the necessity of designing concrete mixtures that attend the local weather conditions, and even more in the significant exposed elements such as roof slabs.

Microscopic Analysis of Bamboo Pieces and Its Relation to Compression Resistance

Bamboo has been identified as a structural element capable of satisfactorily absorbing tension and compression stresses, and, to a lesser proportion, parallel shear along its fibers, as well as bending with possibility of usage in buildings and as viable ecological alternative. The ultrastructure of the bamboo, from the Guadua Velutina species, obtained from the Vega Rica ejido in El Higo, Veracruz, Mexico, was characterized It was characterized the ultra structure of the bamboo, of the species Guadua velutina, obtained of the Ejido Vega Rica of the municipality El Higo, Veracruz, Mexico for use in the industry of the construction. Previously, pieces were tested to determine their mechanical properties: compression and shear parallel to the fiber, following the standards indicated in the methodology. Subsequently, the microscopic analysis of longitudinal and transverse sections of this anisotropic material, with variable porosity in its walls, was carried out. It was found that the arrangement and shape of its fibers that give rise to its porosity is correlated with its resistance to the different stresses to which it is subjected and that its porosity also decreases in joints zones, where its fibers have no defined direction. These findings are important because they make it possible to recognize the durability of the material in such a way that they can be considered in the construction of structural elements.

EXPERIMENTAL AND THEORETICAL TESTING OF THE EFFECTIVENESS OF CONSTRUCTIVE MEASURES TO PREVENT THE PROGRESSIVE COLLAPSE OF THE SPECIAL TYPE METAL SHELLS

The article considers frameless structures in the form of special type metal shells. The main structural element of these special shells is arched thin-walled cold-deformed profiles. The construction of structural elements takes place directly at the construction site. The main anomalies of the exploitation of the specified structures are considered. The main of these anomalies of exploitation is a certain number of accidents and collapses, which, after detailed analysis, can be classified as progressive or “avalanche-like” collapse. The computational algorithms for estimating the stress-strain state and preventing measures the onset of a progressive collapse of special type metal shells are considered. As the preventing measure was described constructive modernization of the original junction of arched structural elements. The aim of the research was to assess the impact of the proposed constructive modernization on the deformation properties of special type metal shell during a two-stage full-scale experiment. The block under research was close to a square, in the plan, cylindrical composite coating shell. Block dimensions: span between side elements 22m., Block length 15.6m., Lifting arm 8.37m., Radius of the cylindrical shell 11.585m. The thickness of the steel element was 1.2 mm.A comparative finite-element analysis of the stress-strain state of the original models of special type metal shell, models of the discrete-continuum ribbed shell (with the implementation of constructive modernization of the joint) was also carried out. The results of the analysis are presented in the form of comparative graphs of displacements of tracked points from loading. The results obtained testify to the effectiveness of the proposed constructive modernization of metal shells of a special type, as measures preventing the onset of progressive collapse of these shell systems.

Enhancing Resiliency and Delivery of Bridge Elements using Ultra-High Performance Concrete as Formwork

A feasibility study of the use of ultra-high performance concrete (UHPC) shell as a formwork is presented. The core concept of the research, developed by the first author, is prefabrication of UHPC shell which acts as a stay-in-place formwork. In the proposed approach, after transporting the UHPC shell to site, the construction of structural elements is completed by placing reinforcing cage inside the UHPC shell and post-pouring with normal concrete. The superior properties of UHPC provide excellent means to enhance the service life of bridge elements, while eliminating the need for assembling or stripping of formwork. As a proof of concept, a combination of experimental and numerical studies was conducted, results of which are reported here. Before conducting experimental work, numerical study in the form of finite element analysis was carried out to investigate performance of shell during placement of the normal concrete. To provide a baseline comparison between UHPC shell formwork and conventional methods, two test specimens were constructed and tested under three-point load setup. The shell test specimen demonstrated flexural strength, 14% greater than an equivalent normal strength concrete specimen. The UHPC shell test specimen failure occurred by debonding of shell at the interface and development of a large crack in the shell. The shell test specimen exhibited improved levels of ductility before failure. The preliminary analysis demonstrated that the idea is feasible and useful for accelerated bridge construction applications.

Analysis to Improve the Strength of Beds Due to the Excess Weight of Users in Slovakia

Good quality sleep is a prerequisite for regenerating the human body, hence, beds should be optimized for specific group of users, taking into consideration their size or age. Current research studies show similar trends in adult populations around the world, where increases in height as well as in weight can be observed. Not only the ergonomics but also the safety of beds, which is determined by the quality and dimensions of structural elements, must be taken into account in bed design. Designing the structural elements for users with a high body weight is presented in the paper. The properties of a bed’s structural elements, which ensure comfort as well as the safety of a bed are affected by the excess weight of users. New requirements for cross sections, suitable materials and construction of structural elements were set in accordance with the standard EN 1725:1998. Also, an analysis of stresses was done using the finite element method (FEM) and the calculation of allowable stresses related to a user weighing 150 kg. The results of our research provide complete standards and regulations associated with the safety requirements of bedroom furniture for users with a weight more than 110 kg to ensure that the manusfacture of quality products in Slovakia.

Structural elements with transparent wood in architecture

Transparent wood is a relatively new material. For the first time, it was created in 1992 by a German researcher Siegfried Fink. Back then he turned wood transparent to reveal its specific cavities for analytical purpose. But it was not until between 2015 and 2016 when Professor Lars Berglund from Swedish KTH University and Professor Liangbing Hu from University of Maryland developed a method to remove colour and some chemicals from small wood samples and added polymers to make it transparent. The material then has the higher strength than original wood while having a 90% transparency. In the future it can be used as an ecological building material which is significantly more biodegradable than plastic or glass. In the present article, examples of the possible use of transparent wood in the construction of structural elements in architecture are given. Examples of beam type load bearing elements and structural parts of the wall structures with use of transparent wood are presented.

Mechanical and microstructural properties of GGBFS–RHA geopolymer concrete

The current study aims to evaluate the suitability of ground granulated blast-furnace slag (GGBFS)- and rice husk ash (RHA)-based geopolymer concrete for construction of structural elements by using high amounts of the industrial and agricultural solid wastes as raw materials. Compressive and splitting tensile strength, shrinkage and rapid chloride permeability tests were carried out to investigate the geopolymer’s properties. The test results indicated that replacement of cement with GGBFS–RHA-based geopolymer improved the mechanical properties of concrete and 100% replacement with the geopolymer can be considered as having the best results from environmental, structural and economic points of view. Furthermore, the curing time affected the compressive strength significantly. In addition, the carbon dioxide (CO2) emmision will be significant with the construction of studied sustainable GGBFS–RHA-based geopolymer composites. Moreover, from a microstructural point of view, total incorporation of GGBFS–RHA-based geopolymer in composites led to pore refinement in both the matrix and the interfacial zones and a reduction in the width of the interfacial transition zone between the paste and the aggregate, which could efficiently reduce water permeability.

Estudo de impacto econômico e ambiental devido ao aumento da resistência do concreto na produção de pilares submetidos a pequenas cargas de compressão

The use of concrete with strengths up to conventional allows the construction of structural elements with greater durability due to their characteristics. Therefore, the purpose of this research is to evaluate the economic and environmental impacts due to increased strength of concrete in the design and execution of columns subject to small loads of compression. Thus, the columns were dimensioned with 1000 kN loading pattern, 3.2 meters height and square cross section. It was analyzed the design of this section, execution cost for concrete with compression strength of the concrete (fck) ranging from 20 MPa to 50 MPa, cement consumption and CO2 emission associated with cement and steel consumption per structural element. The results showed that, taking the dimensioned column with C25 concrete as a reference, with increasing compressive strength of the concrete column, is possible to gain a reduction of the area occupied up to 45%, decreasing costs by up to 18% and reducing damage caused to the environment related to the consumption of cement and steel, because the columns dimensioned with concrete with strengths up to conventional until C45 had lower CO2 emission associated with cement and steel per structural element than those with the scaled reference concrete. Keywords: economic viability, useful area gain, durability, sustainability.

Properties of sandcrete mixtures modified with metakaolin

Eco-friendly, low-cost, sustainable construction materials for utilisation in civil engineering projects have attracted much attention recently. This work deals with the synthesis of sandcrete mixes with metakaolin as a mineral admixture, which can be used either as grout in soil stabilisation (p.e. in corrosive environments like landfills, coastal regions etc.) or as a material for the construction of structural elements. Sandcrete mix design optimisation and mechanical behaviour of the produced samples have been experimentally investigated. It has been found that the beneficial properties of metakaolin can be used towards the production of sandcrete mixes with improved mechanical properties.

Mechanical characterization of Trebisacce stone: preliminary results

Trebisacce stone is a building material employed in the past for the construction of structural elements of the historical centre of Trebisacce and for the realization of ornamental elements of the northern part of Cosenza province.The outcrops of Trebisacce stone belong to the Albidona Formation and are located in the area of Sibari. Lithotypes which have been investigated, limestones, come from historical outcrops situated in the old town of Trebisacce.The aim of this study is to characterize Trebisacce stone, a carbonate rock with good mechanical and durability properties, and to compare results obtained performing different techniques of analysis. Tests which have been performed belong to both non-destructive techniques (Schmidt hammer test) and to destructive techniques (uniaxial compressive strength test). Relationship between Schmidt hammer rebound values and uniaxial strength was analyzed using different equations. Results obtained demonstrate that Trebisacce stone has good mechanical properties. No-destructive tests performed show that the Schmidt hammer device could be a useful tool in estimating rock strength values for engineering applications. Furthermore, the comparison between direct and indirect uniaxial compressive values, demonstrate which of the relationships proposed by many authors, could be better for evaluating the uniaxial compressive strength as a function of unit weight and Schmidt hammer rebound.

Effect of brick infill panel on the seismic safety of reinforced concrete frames under progressive collapse

Structural safety has always been a key preoccupation for engineers responsible for the design of civil engineering projects. One of the mechanisms of structural failure, which has gathered increasing attention over the past few decades, is referred to as \'progressive collapse\' which happens when one or several structural members suddenly fail, whatever the cause (accident, attack, seismic loading(.Any weakness in design or construction of structuralelements can inducethe progressive collapse in structures, during seismic loading. Masonry infill panels have significant influence on structureresponseagainst the lateral load. Therefore in this paper, seismic performance and shear strength of R.C frameswith brick infill panel under various lateral loading patterns are investigated. This evaluation is performed by nonlinear static analysis. The results provided important information for additional design guidance on seismic safety of RC frames with brick infill panel under progressive collapse.