Viktor Gribniak

SHRINKAGE IN REINFORCED CONCRETE STRUCTURES: A COMPUTATIONAL ASPECT

Abstract This paper introduces the recent state of research on shrinkage of concrete. It reviews prediction models of shrinkage strain and curvature analysis methods of reinforced concrete members. New test data on concrete shrinkage has been presented. Various factors that influence shrinkage have been discussed. A calculation technique on short‐term deformations of cracked reinforced concrete members including shrinkage has been introduced. The technique is based on layer model and smeared crack approach. Shrinkage influence on behaviour of reinforced concrete beams was investigated numerically and compared with test data reported in the literature. It has been shown that shrinkage has significantly reduced the cracking resistance and leads to larger deflections.

Eliminating Shrinkage Effect from Moment Curvature and Tension Stiffening Relationships of Reinforced Concrete Members

Experimental results on cracking and deformation behavior of RC members subjected to short-term loading are frequently misinterpreted because shrinkage effect is not taken into account. Even at first loading, free shrinkage strain of concrete may well exceed the cracking strain. The shrinkage strain, restrained by reinforcement, significantly affects the cracking resistance and short-term deformations of RC members. Despite this, most known constitutive laws were derived by using the test data of shrunk RC members under the influence of tension stiffening coupled with shrinkage effect. In this paper, a numerical procedure has been proposed for eliminating shrinkage from moment-curvature and tension-stiffening relationships. The procedure is on the basis of the smeared crack approach and layer section model. It combines direct and inverse techniques of analysis of RC members. The inverse technique, earlier proposed by the first writer, aims at deriving tension-stiffening stress-strain relationships from experimental moment-curvature diagrams. The shrinkage effect was eliminated by assuming in the direct technique a positive (expansion) free shrinkage strain. On the basis of the proposed procedure, free-of-shrinkage tension-stiffening and moment-curvature relationships were derived by using test data of shrunk RC beams obtained by the writers and reported by other investigators. It was shown that negative portions of the tension-stiffening curves disappear after eliminating shrinkage.

Biometric and Intelligent Self-Assessment of Student Progress system

All distance learning participants (students, professors, instructors, mentors, tutors and the rest) would like to know how well the students have assimilated the study materials being taught. The analysis and assessment of the knowledge students have acquired over a semester are an integral part of the independent studies process at the most advanced universities worldwide. A formal test or exam during the semester would cause needless stress for students. To resolve this problem, the authors of this article have developed a Biometric and Intelligent Self-Assessment of Student Progress (BISASP) System. The obtained research results are comparable with the results from other similar studies. This article ends with two case studies to demonstrate practical operation of the BISASP System. The first case study analyses the interdependencies between microtremors, stress and student marks. The second case study compares the marks assigned to students during the e-self-assessment, prior to the e-test and during the e-test. The dependence, determined in the second case study, between the student marks scored for the real examination and the marks based on their self-evaluation is statistically significant (the significance >0.99%). The original contribution of this article, compared to the research results published earlier, is as follows: the BISASP System developed by the authors is superior to the traditional self-assessment systems due to the use of voice stress analysis and a special algorithm, which permits a more detailed analysis of the knowledge attained by a student.

Web-based Biometric Computer Mouse Advisory System to Analyze a User's Emotions and Work Productivity

This chapter describes the analysis of emotional state and work productivity using a Web-based Biometric Computer Mouse Advisory System to Analyze a User’s Emotions and Work Productivity (Advisory system hereafter) developed by author in conjunction with colleagues. The Advisory system determines the level of emotional state and work productivity integrally by employing three main biometric techniques (physiological, psychological and behavioral). By using these three biometric techniques, the Advisory system can analyze a person’s eleven states of being (stress, work productivity, mood, interest in work) and seven emotions (self-control, happiness, anger, fear, sadness, surprise and anxiety) during a realistic timeframe. Furthermore, to raise the reliability of the Advisory system even more, it also integrated the data supplied by the Biometric Finger (blood pressure and pulse rates). Worldwide research includes various scientists who conducted in-depth studies on the different and very important areas of biometric mouse systems. However, biometric mouse systems cannot generate recommendations. The Advisory system determines a user’s physiological, psychological and behavioral/movement parameters based on that user’s real-time needs and existing situation. It then generates thousands of alternative stress management recommendations based on the compiled Maslow’s Pyramid Tables and selects out the most rational of these for the user’s specific situation. The information compiled for Maslow’s Pyramid Tables consists of a collection of respondent surveys and analyses of the best global practices. Maslow’s Pyramid Tables were developed for an employee working with a computer in a typical organization. The Advisory system provides a user with a real-time assessment of his/her own productivity and emotional state. This chapter presents the Advisory system, a case study and a scenario used to test and validate the developed Advisory system and its composite parts to demonstrate its validity, efficiency and usefulness.

Serviceability Analysis of Concrete Beams with Different Arrangements of GFRP Bars in the Tensile Zone

AbstractExtensive experimental investigations were carried out to investigate the serviceability (deformations and crack opening width) of fiber–reinforced polymers (FRP) reinforced concrete members. However, most of the tests were limited to conventional arrangement of bars in a section. Considering glass fiber–reinforced polymer (GFRP) bars (one of the most frequently used types of composite reinforcement), this study experimentally and analytically investigated the serviceability behavior of beams with different arrangements of reinforcement bars in the tensile zone. With particular emphasis on tension-stiffening and bond behavior, the experimental program consisted of full-scale beams and bending bond specimens. The tests revealed specific features in the behavior of the beams due to distribution of tensile bars in three layers or enlarging the cover. A numerical procedure, based on local interaction of reinforcement and surrounding concrete, was applied for serviceability analysis. Several bond stres...

Stochastic Tension-Stiffening Approach for the Solution of Serviceability Problems in Reinforced Concrete: Constitutive Modeling

A number of studies have indicated that the tension-stiffening law is an important input parameter in a numerical analysis of serviceability (deformations and cracking) problems of reinforced concrete (RC) structures. The stochastic nature of concrete cracking, which results in a large scatter of experimental results, renders the constitutive modeling a very difficult task. Even data obtained from short-term tests are to some degree uncertain due to time-dependent processes occurring in concrete, such as shrinkage and creep relaxation. This article provides statistical analysis tools that can be readily applied to engineering practice. Stochastic principles are applied to modeling of tension-stiffening for the purpose of predicting not only the average deformation response of RC elements, but also bounds of these predictions that are of vital importance for practical problems. Unlike common practice, shrinkage of concrete is taken into account in the short-term numerical simulation.

Recommender System to Analyze Student's Academic Performance

A sufficient amount of studies worldwide prove an interrelation linking student learning productivity and interest in learning to physiological parameters. An interest in learning affects learning productivity, while physiological parameters demonstrate such changes. Since the research by the authors of the present article confirmed these interdependencies, a Recommender System to Analyze Students Academic Performance (Recommender System hereafter) has been developed. The Recommender System determines the level of learning productivity integrally by employing three main techniques (physiological, psychological and behavioral). This Recommender System, developed by these authors, uses motivational, educational persistence and social learning theories and the database of best global practices based on above theories to come up with recommendations for students on how to improve their learning efficiency. The Recommender System can pick learning materials taking into account a students learning productivity and the degree to which learning is interesting. Worldwide research includes various scientists who conducted in-depth studies on the different and very important areas of physiological measurements and intelligent systems. We did not manage to find any physiological measurements or any intelligent or integrated system that would take physiological parameters of students, analyze their learning efficiency and, in turn, provide recommendations.

Serviceability Analysis of Flexural Reinforced Concrete Members

Abstract The paper presents a simple discrete crack model for analyzing the deformation and crack width of reinforced concrete beams. The model is based on a non-iterative algorithm and uses a rigid-plastic bond-slip law and elastic properties of materials. Curvatures and crack widths predicted by the proposed technique were checked against the test results of six experimental beams, reported by the authors and other investigators. The article also proposes and discusses a numerical procedure for deriving the average bond stress with reference to the test data. Serviceability analysis resulted in a reasonable agreement on the test measurements.

Deformation Analysis of RC Ties Externally Strengthened with FRP Sheets

The current study has two objectives: to validate the ability of the Atena finite-element software to estimate the deformations of reinforced concrete (RC) elements strengthened with fiber-reinforced polymer (FRP) sheets and to assess the effect of FRP-to-concrete bond strength on the results of numerical simulation. It is shown that the bond strength has to be selected according to the overall stiffness of the composite element. The numerical results found are corroborated experimentally by tensile tests of RC elements strengthened with basalt FRP sheets.

Mechanical simulation of reinforced concrete slabs subjected to fire

Abstract There are many buildings and civil engineering works under construction which are at risk of fire. The fire resistance analysis of reinforced concrete structures constitutes an important part in their design. However, the analysis of the behaviour of load‐bearing members under high temperature conditions is very complicated. Various factors that influence the behaviour of the members need to be taken into account. Analytical and computation methods have been developed in the field of reinforced concrete building exposed to high temperature or accidental fire. Unfortunately, such models are computationally too demanding and their application are limited even for a simply supported reinforced concrete members (beams, plates etc). In this paper, an attempt has been made to extend application of the Flexural model to stress and strain analysis of flexural reinforced concrete members subjected to high temperature. Constitutive models and key material parameters describing thermo‐mechanical behaviour o...