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New procedures for evaluating concrete in existing construction
Juřenová, Jana ; Kocáb, Dalibor (referee) ; Cikrle, Petr (advisor)
This bachelor thesis seeks to increase the awareness of the possibility of using the ultrasonic pulse method for the diagnosis of building structures. It emphasises the use of non-destructive methods, highlighting their ability to provide comparable results to traditional destructive methods of assessment, whilst minimising interference to the structure. The work includes reporting on the procedures for determining the characteristic compressive strength of concrete in existing structures as defined in EN 13791, updated in 2021. The work focuses primarily on calibrating results from non-destructive indirect measurements with those obtained destructively using core borings.
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Preparation and implementation of construction and technical survey of prestressed bridge structure
Kummer, Jan ; Kocáb, Dalibor (referee) ; Anton, Ondřej (advisor)
The thesis focuses on a visual excursion with photo documentation, the localisation of prestressing reinforcement of prefabricated beams type DS-T and the analysis of their state as well as the offtake of core drilling in order to establish their strength under pressure. In the theoretical part I describe the principles of the static effect of prestressed concrete and the basic sorting of technical survey and diagnostic methods. Furthermore I explain specific diagnostic methods for the determination of the location and state of prestressing reinforcement. The practical part focuses on photodocumentation of a bridge, the determination of the location of the beams reinforcement using georadar, (chopped probes to reinforcement and removal of core drilling samples. The conclusion provides the location of prestressing reinforcement and the level of its corrosion and grouting, the photo documentation of the bridge and a collection of samples from core drilling in order to determine the strength under pressure of the concrete.
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Determination of the formwork strength of concrete using a Silver Schmidt hardness tester
Janka, Marek ; Kocáb, Dalibor (referee) ; Cikrle, Petr (advisor)
This bachelor thesis deal with the issues of nondestructive testing of the formwork removal strength of concrete. It works with two different compositions of concrete and for both of them, it determines the relation between compressive strength and surface hardness obtained by the SilverSchimdt hammer with mushroom plunger. It shows inappropriateness of ultrasonic impulse method to determine formwork removal strength. It compares obtained relations with each other and with the literature. The goal of this thesis is to utilize determined relations for verification of minimal requested formwork removal strength during construction.
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The Influence of different Types of Fiber-reinforcement on the Behavior of Concrete Slabs
Wünsche, Dominik ; Žítt, Petr (referee) ; Kocáb, Dalibor (advisor)
The bachelor‘s thesis deals with the issue of concrete, specifically self-compacting concrete, fiber concrete and other types of concrete used. The work consists of two parts, the theoretical one, which will deal with the properties of the concrete. It describes the individual test methods used in the practical part. The test methods are the ultrasonic pulse method, the resonance method, the static modulus of elasticity, the compressive strength, and especially flexural strength. The second part is a practical part, which is processed by an experiment. In the experimental part, it will be mainly about carrying out tests of self-compacting concrete slabs and concrete with the addition of steel fibers. Subsequently, selected characteristics of concrete are determined and the whole experiment is evaluated.
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Modern statistical approach in evaluating the compressive strength of concrete in structures using the rebound hammer method
Janka, Marek ; Kocáb, Dalibor (referee) ; Misák, Petr (advisor)
This diploma thesis examines various linear regression methods and their use to establish regression relationships between the compressive strength of concrete determined by the indirect method and by the crushing of the specimens in the press. It deals mainly with the uncertainty of values measured by the indirect method, which is neglected by the usually used ordinary least squares regression method. It also deals with the weighted least squares method, suitable for so-called heteroskedastic data. It compares different regression methods on several sets of previously measured data. The final part of the work examines the effect of removing too influential points identified by Cook's distance, which may skew the regression results.
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Survey and Assessment of Masonry Buildings before Modernization
Stanislav, Štěpán ; Kocáb, Dalibor (referee) ; Cikrle, Petr (advisor)
This thesis deals with the exploration and evaluation of historic masonry building. The researched building was built in the 20th 20th century. Is located in the premises of the Philosophical Faculty of Masaryk University in Brno. During preparation for the planned modernization of the survey was conducted several objects of the university complex. In this work, however, we consider only the building named "C". It will be processed by selected diagnostic method. The findings will then serve as a basis for static analysis and follow-up activities associated with modernization.
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Influence of Air Entrainment and Curing on Development of Elastic Modulus of Concrete
Bartulíková, Radka ; Kucharczyková, Barbara (referee) ; Kocáb, Dalibor (advisor)
Master's thesis deals with influence of various factors on the concrete compressive strength and modulus of elasticity. This work concentrates mainly on the influence of early curing and air entrainment of concrete. One part of this work is the evaluation of laboratory measurement, which was carried out on cubes of standard and norm prisms. The development of elastic moduli was monitored in time to 730 days of age with respect to air entrainment and curing conditions. The second part of the experiment deals with a comparison of theoretical creep curves depending on the value of the modulus of elasticity based on different standards. Again, the air entrainment effect and influence of initial conditions are reflected.
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