Evaluation of end bearing capacity of drilled shafts in sand by numerical and SPT-based methods

Drilled shafts are a common type of pile foundations which are often used as foundations for buildings, bridges and other structures. The end bearing capacity of drilled shafts, which plays an important role in their design particularly in sandy soils, has traditionally been estimated using empirical or semi-empirical methods. With advances in computing power, it is now possible to conduct more realistic analyses. In this paper, at first, the end bearing capacity of drilled shafts in sandy soils is analyzed numerically and validated with the results of pile load test. Then, the numerical results are compared with the results of Standard Penetration Test (SPT)-based methods. The comparison indicated that there is a satisfactory agreement between the results of numerical method proposed in this paper and the results achieved by SPT-based methods

Forecasting the condition of petroleum impregnated load bearing concrete and reinforced concrete structures

Petroleum products (PP) used in industrial processes systematically fall on the load-bearing CRC structures and gradually impregnate therein. Currently, available guidelines for the assessment of technical condition and reliability of load-bearing CRC structures do not fully take into account the effect of viscosity of PP that impregnated therein. Our study was performed on the basis of analyzing, generalizing and evaluations of experimental data on the effect of PP of different viscosities on the physical and mechanical properties (PMP) of concrete using the methods of probability theory and mathematical statistics. The obtained results allow to constitute a scientifically substantiated forecast of changes in PMP of PP impregnated load-bearing CRC structures and to provide a quantitative characterization of their technical condition.Keywords: viscosity, strain, endurance, fatigue

Effect of modifier mb10-50c on the physical and mechanical properties of high-strength fine-aggregate "powdery" concrete

In this study we used concrete modifier MB10-50C, an admixture on an organic-mineral basiscontained of micro-silica, fly ash, hardening regulator, superplasticizer, to produce thehigh-strength fine-aggregate "powdery" concrete (HSFPC). We produced samples of HSFPCwith dimensions of 100x100x100 mm and 100x100x400 mm. The physical and mechanicalcharacteristics of HSFPC, such as: compressive strength, tensile strength at bending, strengthat axial tension, cracking moment, HSFPC grade, and elastic modulus, at the curing periods of7, 14, 28, 60 days, have been determined. The research results have been implemented in theconstruction of high-rise buildings of the Moscow International Business Center "MoscowCity", and in reconstruction of the Engineering Faculty building of the RUDN University.Keywords: compressive strength, tensile strength at bending, strength at axial tension,cracking moment, elastic modulus

Cтратегии и технологии инновационного развития корпораций

У монографії представлено результати дослідження й систематизації теоретичних, науково-методологічних і практичних положень та розробок щодо стратегій та технологій інноваційного розвитку корпорацій. Запропоновано і обґрунтовано технології управління інноваційним розвитком підприємств, стратегії розвитку бізнесу, визначено сучасні реалії та тенденції корпоративного маркетингу, культури та соціальної відповідальності бізнесу, запропоновано нові підходи у корпоративному управлінні, обґрунтовано доцільність використання краудтехнологій фінансування інноваційних проектів, визначено підхо-ди щодо управління персоналом корпорацій в поведінковій економіці. Для науковців та фахівців сфери економіки та управління підприємствам

Forecasting the compressive strength of soil-concretedepending on the percentage of cement and curing period

One of the most important physical and mechanical properties of soil-concrete is the compressive strength. To this end we carried out a study of soil-concrete strength depending on its curing conditions and percentage of cement. For our study we used loam soil with the plasticity index of Ip = 12.3, Portland cement of type I, ground limestone with the specific surface of 4500 cm2/g, polycarboxylate based superplasticizer C-3 and water for mixing. A mathematical model for determining the compressive strength of soil-concrete depending on the percentage of cement and the curing period is developed. This proposed mathematical model is advisable to apply for assessment of the compressive strength of soil-cement massive layer after the urgent repair of under-road pipelines, as well as where soil-concrete is used to strengthen the structure's base.Keywords: compressive strength, curing condition, soil-cement ratio

Soil-cement ratio and curing conditions as the factors of soil-concrete strength

Soil-concrete is widely used to strengthen the foundation footings, in the construction of roads and railways, as well as for the production of bricks and pavement tiles. One of the most important physical and mechanical properties of soil-concrete is the compressive strength. We carried out a study of soil-concrete strength depending on its curing conditions and percentage of cement. For our study we used loam soil with the plasticity index of Ip = 12.3, Portland cement of type I, ground limestone with the specific surface of 4500 cm2/g, polycarboxylate based superplasticizer and water for mixing. Curing of samples was carried out in air-humid condition in wet sawdust and also with the thermal-humid treatment in a steam chamber. It is experimentally established that the strength of soil-concrete depends not only on the ratio of clay aggregate and mineral binder, but also on the temperature and humidity conditions of curing. Additives of ground limestone and superplasticizer contribute to increase the compressive strength of soil-concrete. A mathematical model for determining the compressive strength of soil-concrete depending on the percentage of cement and the curing period is developed. This proposed mathematical model is advisable to apply for assessment of the compressive strength of soil-cement massive layer after the urgent repair of under-road pipelines. © 2017 Trans Tech Publications

Reliability of technological systems of building construction in permanent EPS formwork

Technological system (TS) of cast-in-situ reinforced concrete (RC) building construction in permanent EPS formwork is one of the most effective and promising areas of contemporary construction. It is important to determine the level of reliability to improve the efficiency of TS and the quality of construction output. Experience shows that technological defects occur during the construction of RC structures in the permanent EPS formwork. In this regard, reliability assessment of TS on the quality parameters is the relevant. Estimation features of the reliability indices of construction TS is that it can be described mathematically based on the distribution law of observations data. In our study we used the following methods: visual inspection of structures and detection of technological defects; direct measurement of the size of deviations from the design values; statistical analysis of the measurement results; analysis of the qualitative characteristics of constructed structures by the quantitative parameters based on the theory of reliability of TS. It is established that the structural defects in permanent EPS formwork occur during the construction of cast-in-situ RC buildings, and those are formed as the panels divergence under the thrust from fresh concrete mix. As a result, the thermal insulation layer of structures reduces, which may lead to the freezing in these parts. Based on the analysis of field measurements and generalizations of statistical data, the values of formation frequency of structural defects are determined, and also the assessment of assignment probability on quality parameters is given. (C) 2017 The Authors. Published by IASE. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Strength and deformability of reinforced concrete beams with indirect reinforcement in the form of welded meshes in compressed zone

One of the ways to improve the strength and deformation characteristics of reinforced concrete structures is the use of indirect reinforcement. Such reinforcement, located perpendicular to the compressive force, by limiting transverse deformations creates a volumetric stress state and increases the efficiency of concrete in compression. The article presents a method for assessing the stress-strain state of structures, which allows to take into account the reserves of bearing capacity and apply more economical design solutions. The calculation of strength is considered and the diagram of concrete deformation reinforced by indirect reinforcement is obtained. It is shown that the relative deformations at the apex of the compression diagram depend mainly on the relative level of lateral reduction and concrete strength. It is shown that the lower the concrete class, the less indirect reinforcement affects its strength characteristics, but the limiting deformations increase more strongly, and therefore an almost horizontal section appears near the top of the diagram, the longer the concrete class and the higher the reinforcement percentage. © 2019 Trans Tech Publications Ltd, Switzerland

Influence of thickness of air gap on concrete curing in formwork with transparent cover

Heat treatment of concrete is used to speed up its curing. Therefore, this process allows getting complete product in a short time and it is used at the plants for manufacturing of concrete elements. Fossil fuels are used for this purpose. An important task for engineers and scientists is to reduce costs of the manufacturing and make it ecological by introducing energy-saving technologies and renewable energy resources. The employment of solar energy for heat treatment is one of the ways to settle the problem. However, the efficiency of such engineering solution depends on type and construction of the solar energy equipment. The formwork, equipped by transparent cover, is chosen as the object of research. The research work is devoted to determination of optimal thickness of air gap between concrete element and transparent cover of the formwork. The results and methodology, as well as the information about materials and boundary conditions of the experiments are given in the research work. The obtained results allow increasing efficiency of employment of solar energy for manufacturing of concrete elements at the plants. © 2019 Trans Tech Publications Ltd, Switzerland