Petr Bílý

Experimental Verification of the Behavior of Protective Steel Liner of Concrete Containment

Containment is the last barrier protecting the environment from contamination in case of serious accident in nuclear power plant. Steel liner is often used to guarantee leaktightness of concrete containment and therefore the design of the liner must be done with utmost care. Several methods are used in practice to anchor the liner plate to concrete containment wall, differing in layout and type of anchorage elements used. The anchorage system must ensure full connection of the liner to the wall, liner buckling and tearing have to be prevented. The objective of the research was to determine the behavior of typical details of steel liner of concrete containment subjected to axial and shear loads. Two types of experiments were proposed. The first one was aimed at defining the response of two different types of liner anchorage system – L-profiles and headed studs – to the axial loads imposed on the liner plate. Behavior of specimens with and without initial imperfection of the steel plate was also compared. The goal of the second experiment was to determine the shear load-bearing capacity of the anchorage and to verify that liner tearing will not occur before the failure of the anchorage – this one of the main conditions of the safe design. The experimental program was successfully executed and the results are presented in the paper.

Mechanical properties and durability of crumb rubber concrete

This paper is focused on concrete with admixture of rubber powder, generally called crumb rubber concrete (CRC). The inspiration was found in Arizona, where one of the first CRCs has been created. However, Arizona has completely different climates than Central Europe. Could we use the crumb rubber concrete on construction applications in the Central European climate too? The paper evaluates the influence of the rubber powder on material characteristics and durability of CRC. CRCs with various contents of fine and coarse crumb powder were compared. The tested parameters were slump, air content, permeability, resistance of concrete to water with deicing chemicals, compressive and splitting tensile strength. The tests showed that workability, compressive strength and permeability decreased as the amount of rubber increased, but the air content increased as the rubber content increased. Photos of air voids in cement matrix from electron microscope were captured. The results of laboratory tests showed that admixture of rubber powder in concrete could have a positive impact on durability of concrete and concurrently contribute to sustainable development. Considering the lower compressive strength, CRC is recommended for use in applications where the high strength of concrete is not required.

FEM simulation of static loading test of the Omega beam

The paper deals with a FEM simulation of static loading test of the Omega beam. Omega beam is a precast prestressed high-performance concrete element with the shape of Greek letter omega. Omega beam was designed as a self-supporting permanent formwork member for construction of girder bridges. FEM program ATENA Science was exploited for simulation of load-bearing test of the beam. The numerical model was calibrated using the data from both static loading test and tests of material properties. Comparison of load-displacement diagrams obtained from the experiment and the model was conducted. Development of cracks and crack patterns were compared. Very good agreement of experimental data and the FEM model was reached. The calibrated model can be used for design of optimized Omega beams in the future without the need of expensive loading tests. The calibrated material model can be also exploited in other types of FEM analyses of bridges constructed with the use of Omega beams, such as limit state analysis, optimization of shear connectors, prediction of long-term deflections or prediction of crack development.

Analysis of laboratory compaction methods of roller compacted concrete

Roller-Compacted Concrete (RCC) is an ordinary concrete poured and compacted with machines typically used for laying of asphalt road layers. One of the problems connected with this technology is preparation of representative samples in the laboratory. The aim of this work was to analyse two methods of preparation of RCC laboratory samples with bulk density as the comparative parameter. The first method used dynamic compaction by pneumatic hammer. The second method of compaction had a static character. The specimens were loaded by precisely defined force in laboratory loading machine to create the same conditions as during static rolling (in the Czech Republic, only static rolling is commonly used). Bulk densities obtained by the two compaction methods were compared with core drills extracted from real RCC structure. The results have shown that the samples produced by pneumatic hammer tend to overestimate the bulk density of the material. For both compaction methods, immediate bearing index test was performed to verify the quality of compaction. A fundamental difference between static and dynamic compaction was identified. In static compaction, initial resistance to penetration of the mandrel was higher, after exceeding certain limit the resistance was constant. This means that the samples were well compacted just on the surface. A specimen made by pneumatic hammer actively resisted throughout the test, the whole volume was uniformly compacted.

Distribution of Stresses in Masonry Pillar with Fully Filled and Unfilled Perpend Joints

The paper summarizes the results of numerical analysis conducted with the aim to compare the distribution of stresses in masonry pillars constructed using different bricklaying techniques. The analysis was carried out in reaction to the discussion of members of Czech standardization committee TNK 37 – Masonry structures. Currently, most of masonry load-bearing structures in the Czech Republic are made from clay blocks without mortar in perpend joints. The analysis seeks the answer to the question whether it is possible, in case of the eccentrically loaded masonry pillars with unfilled perpend joints, to consider the value of design compressive strength calculated using the same approach as for pillars with filled perpend joints for the check of vertical load resistance. Supplementary comparison of the behavior of the pillars with filled and unfilled perpend joints loaded by lateral load in the plane of the pillar (corresponding to short shear walls) was also conducted. 2D FEM model created in ATENA Science software was exploited for the analysis. The results confirmed that the approaches contained in ČSN EN 1996-1-1 [1] are basically applicable for pillars with unfilled perpend joints.