Concrete Part Research Articles

Monitoring of Thermal Damage Evolution in Concrete Parts by Acoustic NDT Methods

The paper presents the results of the experimental work which was focused on the use of the Impact-echo method for testing of concrete specimens damaged by high-temperature. The test specimens were heated to 600 and 800 °C for sixty, one hundred twenty and three hundred minutes. After heating, the samples were continuously cooled to room temperature and tested by Impact-echo method.

The Possibility of Using Nonlinear Acoustic Spectroscopy with a Single Excitation Signal for Testing of Concrete Elements Damaged by High Temperature

This paper focuses on the use of nonlinear acoustic spectroscopy with one excitation signal for NDT of concrete parts exposed to high temperature. The rate of the temperature rise, the highest achieved temperature, time of exposure to elevated temperature and the cooling rate has an influence on the overall damage of concrete structures affected by fire. The test specimens described in this paper have been heated for various periods of time and at a different temperature. Nonlinear acoustic spectroscopy method was performed before and after heat load.

Presenting a Suitable Quick Construction Pattern Using Prefabricated Components in Critical Conditions

Abstract Every year, many people in the world lose their homes due to natural disasters such as earthquakes, floods and so on. In critical situations, the use of prefabricated parts in the buildings has many technical and economic advantages. Hence, today, this technology is widely used in the industrialized societies. The purpose of this research is to provide an appropriate model for speeding up the process of constructing buildings using prefabricated parts in critical conditions. To do this, Analytic Network Process (ANP) approach has been used to select the best option for speeding up construction projects using prefabricated parts and in critical situations. In this study, the intended criteria are quality, time, cost, and strength. The options that we should compare and the best option among them, according to the criteria mentioned, are Lightweight Steel Frame (LSF) parts, steel parts and concrete parts. In order to find this prioritization, the viewpoints of civil engineers and construction experts have been used. It should also be noted that for the ANP method, the Super Decisions software has been used.

Optimization of composite dowels shape in steel-concrete composite floor

The paper contains a numerical analysis of a steel-concrete composite beam with a composite dowel. The connector is a contoured part of the web in a half of the steel section. In the first part of the work, the composite beam was analytically designed in accordance with PN-EN 1994-1-1 standard. Three cross-sections were selected from a hot-rolled sections 1/2 HEB 600, 1/2 HEA 500 and 1/2 HEA 400, so that the beams effort was 50%, 70% and 90% respectively. The length of the beam was 6.0 m. Structural steel S235, reinforcement steel fyk = 500 MPa (B500B) and concrete C20/25, C25/30, C30/37 were used. In the second part of the work the numerical analysis was carried out using the ADINA System program based on the Finite Element Method. The shape of the composite dowels in the class from the concrete class was optimized. The influence of the composite dowels shape on the stress concentration in the area of the composite dowels depending on the beam effort was considered. The stresses and displacements in the steel and concrete parts as well as cracking in concrete were assessed.

Analysis on steel-concrete joint section of hybrid girder cable-stayed bridge

Hybrid girder cable-stayed bridge has some advantages, such as structure mechanism performance and the low cost. In China, more and more cable-stayed bridge with hybrid girder appeared. The steel–concrete joint part is one of the key structures of large span cable-stayed bridge with hybrid girder, the static bearing capacity and fatigue performance of steel–concrete joint part structure is directly related to security and durability of the bridge. Through the finite element simulation calculation, the stress distribution is calculated, and the stress distribution of the steel structure top plate, steel structure baseplate, concrete top plate and concrete baseplate is analysed emphatically. Verify the bearing capacity and safety of the structural design of joint section.

Directions of Convergence of the Requirements of the Main Domestic Standard for the Design of Concrete and Reinforced Concrete Structures SP 63.13330.2012 with the Requirements of the International Standard ISO 19338

Design standards on building structures should contain, first of all, the performance and assessment requirements of structures. At the same time, design standards should provide the possibility for design and construction of concrete and reinforced concrete parts of buildings and structures that meet the requirements of the Technical regulations "On the safety of buildings and structures".
 Taking into account the importance of ensuring the reliability and safety of buildings and structures erected with the use of structural concrete, the technical Committee of the international organization for standardization ISO TC 71 "Concrete, reinforced concrete and prestressed concrete", certifies national standards for compliance with the requirements of the international standard ISO 19338 "Performance and Assessment Requirements for Design Standards on Structural Concrete", developed by the same Committee.
 The standard describes the issues that should be included in the standards for the design of concrete and reinforced concrete structures (terms and definitions, basic requirements, performance requirements,loads and impacts, design estimates, requirements for manufacturing and construction, as well as quality control). These requirements are common to all standards in the design of concrete and reinforced concrete structures.
 In this regard, it is relevant and important to establish the possibility of presenting the National Code of rules SP 63.13330.2012 "SNiP 52.01-2003 Plain and Reinforced Concrete Structures. General Provisions" for certification for compliance with the requirements of ISO 19338. To achieve this goal, the relevant work has been done, based on the results of which were made the proposals for the submission of SP 63.13330.2012 for certification for compliance with ISO 19338:2014. These proposals are set out in the text of the article.

Toward discerning community based tourism

CBT rooted some decades ago in the West and has currently been on the rapid rise thanks to the promotion of internet-based informatics. CBT tourists has shaped several driving forces and motivation to speed up the promotion and completion of CBT worldwide. Along with the boom of high-tech and its incredible pressures on human mind, post-modernism (PM) has been shaped due to the strong demand of liberalizing in human beings' mind and diversifying their lifestyles under the mutual interaction between ecological and cultural resources. PM starts firstly in arts and literature, gradually influences on business and tourism; hence impacts on CBT. The reconciliation of CBT and PM gives birth to discerning CBT advanced by discerning travelers who definitly care on their selfparticipation, self-experience, self-discovery during their journeys as well as the request for cooperation, co-controlling and co-responsibility of all the tourists, state agents and the local communities during the services. The discerning CBT travelers partially promote the commeners' awareness and engagement in advancing standard of life and civilizing of their lifestyle. Discerning CBT is surely not to replace popular CBT as a whole but to modify the diversity of modern tourism as it meets a concrete part of the various demands of tourists and pay more important role in standardizing human life.

Crack Detection in Concrete Parts Using Vibrothermography

This study investigates the use of vibrothermography to detect cracks in concrete parts, developing acoustic excitation devices (sonic and ultrasonic and low- and high-power excitation devices) and examining the influences of excitation frequency, power, and pressure on the ability to detect cracks. Experimental results demonstrate that this inspection technique can suitably detect concrete cracks: Ultrasound at frequencies from 20 to 100 kHz could be used to excite concrete cracks with notable temperature rise; coarse aggregates in concrete do not interfere with the ability to detect cracks; high-power ultrasound enhances crack detection though intense scattering of attenuation that could be induced by coarse aggregates. Moreover, the stimulus horn designed as part of this study can input ultrasound at high power into concrete parts without damaging the contact surface, while the custom-made pressure loading sleeve can steadily exert force on the transducer during excitation; the optimal force exerted on KMD ultrasonic transducers with a rated power of 50 W is ~ 1500 N, which can make the transducer output enough power to detect cracks.

Stress-strain state of corrosion-damaged reinforced concrete elements under dynamic loading

The solution of problems of survivability of reinforced concrete elements at beyond design impacts caused by simultaneous manifestation of power and environmental factors is necessary in modern realities. The impact of external aggressive environments, the operation of buildings without timely repairs is the cause of corrosion processes in reinforced concrete elements, which leads to a decrease in their bearing capacity and, as a consequence, reduction in the life of buildings. Currently, one of the urgent problems is the actual work of corrosion-damaged reinforced concrete elements under the impact of dynamic and static loads. The bendable reinforced concrete beam locally damaged in the compressed part of the cross-section is considered. Using modern computing software complex, it was carried out the comparative evaluation of the stress-strain state of an undamaged and corrosion-damaged reinforced concrete elements under dynamic and static loading. The influence of the weakened by corrosion concrete part of the compressed area on the redistribution of stresses in the section is analyzed.

Influence of surface based cohesive parameters on static performance of concrete composite T-shaped beams

The study presented constitutes the next step of authors’ investigations on the concrete composite T-shaped beams. The comparison of the failure modes and crack patterns of numerical models and beams tested was performed previously. In this paper, analyses concentrate on determination the proper values of cohesive surface parameters ensuring the high conformity of deformation and strains of the numerical model to the experimental results. In the particular series of beams the interfaces between concrete parts are varied as follows: reinforced joint with normal and tangential interactions only (BZ/S2/A), non-reinforced joint with adhesion (BZ/P), and reinforced joint with adhesion (BZ/P+S). Material properties used in numerical model are based on obtained in the laboratory ones. Furthermore, the ‘traction–separation’ law in the ABAQUS software defining the cohesion surface is used and analysis of the cohesive parameters response to interface roughness is carried out. The results show a strong dependence between the cohesion surface parameters and the response of the composite beam. A very good convergence of the numerical model with the experimental results in terms of ‘force-displacement’ relationship is achieved. Finally the parameters defined in the ABAQUS are determined, which have a key impact on the beams response.

Experimental and theoretical study of composite trusses

Abstract The optimal use of the properties of steel and concrete is the advantage of composite constructions made of these materials. Especially, the steel section works efficiently in tension and the concrete part may transfer loads in compression. In composite element, they are acting in common to resist axial forces and bending moments. This structural system behaviour is rather complicate, mainly in the case of steel trusses combined with a concrete deck. Experimental research and numerical simulations based on finite element method are used to analyse the mechanical behaviour of these modern structural members.

Bentonite replacing part of cement concrete for resistance to chloride ion attack

Bentonite is known as a kind of natural pozzolan that can improve the mechanical properties of cementitious materials and reduce the overall CO2 output of cement production. This study is designed to evaluate the feasibility of using bentonite as a substitute for cement in concrete and analyze the effect of bentonite on resisting chloride ion penetration. The concrete was replaced by equal-quality bentonite for 0%, 5%, 10%, 15% and 20% cement respectively, and the water-cement ratio, fine and coarse aggregate content remained constant. The results indicated that as the bentonite content increased, the compressive strength of the mixes increased first and then decreased. The sample containing 10% bentonite got a higher compressive strength than the other samples. The rapid chloride migration (RCM) tests showed that the samples containing bentonite had better resistance to chloride ion attack than samples without bentonite against chloride, especially the sample containing 10% bentonite. It can be concluded that the concrete with 10% bentonite can improve the resistance to chloride ion diffusion with high compressive strength.

Assess the Effectiveness of protective Concrete coatings of microbiological sulfuric acid Aggression

Specification of corrosion processes in sewerage networks, the predominant role of microbiological processes in them requires the protection of concrete with materials resistant to specific biogenic sulfuric acid aggression. The effective protective materials, in this case, are those that, in addition to acid-proofing materials, have bactericidal properties. Polymer composite materials (PCM) of cold curing based on modified epoxy-resin, resins with dispersed oxides as fillers are widely used in construction. Unique properties and simple technologies make it possible to use them as injection formulations for repair, restoration and restoration of building structures and structures, waterproofing and facing materials, for impregnating, gluing and coating metal, wooden, brick and concrete building structures and parts. In the reconstruction and restoration of sewerage collectors operating under conditions of exposure to liquid biochemically aggressive media with mineral acids and organic substances, particular attention is paid to the permeability of repair materials. Based on the results of the study, PCM compositions were chosen whose estimated lifetime is about 20 years, ensuring reliable protection of the sewage collectors from corrosion.

Theoretical and experimental study on shear strength of precast steel reinforced concrete beam

With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

Utilization of Rice Straw Ash as A Mineral Admixture in Construction Work

This paper relates the practical use of rice straw ash (RSA) in construction work. In this project, a small house was built and rice straw ash was used in the half portion of the building, as the cement replacing agent. Both the destructive and non-destructive tests were performed, to study the strength variation of the walls made with and without RSA. Scanning electron micrograph and energy dispersive spectroscopy analysis were performed to study various properties of RSA. The experimental results shows that the strength of OPC and RSA walls are equivalent in case of both mortar and concrete parts of the building.

Slant shear strength of hybrid concrete made with old and new parts using reactive and inert waste powders

Manufactured reactive powders, as a silica fume, are usually used in production of high strength concrete with for retrofitting purposes of concrete structures. The efficiency of inert waste glass powder in hybrid concrete fabrication has not been widely investigated, thus further studies are essentially considered in this area. In the present study, hybrid concrete prisms with size of 10x10x30 cm have been made with old ordinary concrete (OC) and new high strength concrete (HSC). High strength of new concrete part of these prisms is achieved via using of waste glass powder, silica fume and mixture of them. The roughness of interfacial surface between old and new parts of hybrid concrete is improved in various manners with utilizing sand blast, holes and grooves. Performance of these elements has been measured in terms of slant shear strength and mode of failure. The results have been shown that there is a relatively similar strength with using retrofitted concrete made with the used powder which includes silica fume, glass powders, and their mixture, the mixture of both powders, namely, silica fume and waste glass powders is regarded a best choice in the present stud. It is demonstrated also that the grooved interface between old and new concretes induces proper strength equivalent to 89% of control concrete prisms strength.

Numerical and experimental tests of steel-concrete composite beam with the connector made of top-hat profile

The paper presents solution for a steel-concrete composite beam structure. The connectors were executed from sections of a non-weldable top-hat profile 80 × 85 × 3 made of S235 steel. The connectors were fastened to the beam with four shot nails.In the first part of the work the push-out tests of connectors were carried out. The tests allowed to optimize the length of the connector. The connectors with a length of 60 and 100 mm were considered. The results were verified in a numerical analysis.In the second part of the work, for the best variant of the connector, two models of the composite ceiling beam were made: a numerical one and in real scale. The ceiling model was constructed from an IPE I-beam, galvanized trapezoidal sheet, concrete, reinforcing mesh and top-hat connectors. The values of normal stresses and displacements were determined based on the numerical analysis. These results were compared with the displacements obtained in experimental test.The numerical analysis was carried out using the ADINA System program based on the Finite Element Method. The stresses and displacements in the steel and concrete parts as well as cracking in concrete were assessed.

Steel–concrete hybrid bridge decks: rational design models for connection regions

Steel–concrete hybrid bridge decks have been used in several bridges for their added benefit in constructive operations and cost. They usually adopt reinforced concrete side-spans and all-steel or steel–concrete composite girders as main spans, typically with monolithic connections between them. Design codes address separately the design of the steel and concrete regions of the connection. However, a rational design, with an efficient transfer of stresses between the steel and the concrete parts, should be based on a global understanding of the connection region structural behaviour. Therefore, a rational model for the design of the connection region is proposed, which is based on web shear buckling models developed over recent decades for steel panels and stress field models for structural concrete elements. A hybrid bridge deck connection region is presented as the case study. Several solutions for the connection are introduced and shear resistances are evaluated based on the proposed models.

Comunicação e trabalho: implicações teórico-metodológicas

Resumo Neste artigo, discute-se a abordagem teórico-metodológica de comunicação e trabalho. Argumenta-se que a comunicação é uma atividade humana, tal qual a atividade de trabalho na invenção do indivíduo e da subjetividade. Além disso, afirma-se que as relações de comunicação compõem o local de trabalho concreto, atravessam e fazem parte de sua historicidade. O mundo do trabalho é, nesta perspectiva, mais do que local geográfico; abrange a produção de significados, as lógicas socioculturais, históricas e políticas. Este entendimento permite abrangências metodológicas e empíricas que possibilitam compreender o fenômeno comunicacional como objeto da área da comunicação.

Modified Strut Effectiveness Factor for FRP-Reinforced Concrete Deep Beams

A few examinations have endeavored to assess a definitive shear quality of a fiber fortified polymer (FRP)- strengthened solid shallow shafts. Be that as it may, need data announced for examining the solid profound pillars strengthened with FRP bars. The majority of these investigations don't think about the blend of the rigidity of both FRP support and cement. This examination builds up a basic swagger adequacy factor model to evaluate the referenced issue. Two sorts of disappointment modes; concrete part and pulverizing disappointment modes were examined. Protection from corner to corner part is chiefly given by the longitudinal FRP support, steel shear fortification, and cement rigidity. The proposed model has been confirmed utilizing an aggregate of 45 databases gathered from writing. Results show that the proposed model can evaluate a definitive shear quality. Structure of trial (DOE) programming was used to examine the impact of different parameter esteems on a definitive shear quality limit. The outcomes demonstrate that the shear range to powerful profundity proportion has the most astounding impact contrasted and alternate parameters.