Key Engineering Materials Vol. 691

Abstract: Numerical interaction model of reinforced concrete slab and subsoil was created in ANSYS. Input data for numerical analysis were obtained during experimental loading test of reinforced concrete slab. Loading test was performed using unique experimental equipment constructed in the area of Faculty of Civil Engineering, VŠB-TU Ostrava. Analysis of interaction of reinforced concrete slab with subsoil was solved with application of inhomogeneous half-space. Application of inhomogeneous half-space allows better capture the subsoil behaviour and its increasing modulus of deformability with increasing depth of subsoil model. Homogeneous half-space this takes no account. Reinforced concrete slab was cracked during an experiment. The effect of cracks was also taken into account in the numerical model of reinforced concrete slab using derived modulus of elasticity of cracked concrete. Values calculated by all types of interaction models were compared with values measured during the loading test of reinforced concrete slab.

Abstract: This paper deals with the determination of selected parameters (the thickness and the dynamic modulus of elasticity) of concrete structures by non-destructive methods. Short overview of the literature, the description of used methods, measuring devices used during the tests, the descriptions of examined structures, and obtained results are mentioned. Two independent methods (the Ultrasonic Method and the Resonant Method, in some case with the combination of the Phase Velocity Method), had been used for determination of required parameters of structures. The results had been in good coincidence with the values mentioned in the literature. At the end of the paper, obtained results are summarized and future plans are presented.

Abstract: Corrosion of steel reinforcement is the major cause of deterioration of existing RC structures. Combined effects of moisture, temperature, and chlorides reduce the alkalinity of concrete and exacerbate the corrosion of steel reinforcement, especially for concrete structures subjected to aggressive environments, such as marine structures and bridges and parking garages exposed to de-icing salts. Glass fiber reinforcement polymer (GFRP) bars are suitable alternatives to steel bars in reinforced concrete applications if durability, electromagnetic transparency, or ease of demolition in temporary constructions is sought, that have to be demolished partially by tunnel boring machines (TBMs). The bond of GFRP reinforcement is different from steel reinforcing bars. This paper presents factors affecting the bond strength between GFRP reinforcement and concrete.

Abstract: General refurbishment of prestressed reinforced concrete bridge of Pavel Wonka in Pardubice was done in 2006. Within the preparation of refurbishment a full diagnostics of the structure was performed with the assistance of Klokner Institute, including diagnostics of longitudinal prestressed loose cables located in bridge boxes and the real condition of the corrosion was found. New inspection, including water-insulation system and condition of repaired concrete structures was held in 2015. Some of the findings and comparison of the condition before refurbishment and condition after about 10 years of operation are introduced in this article.

Abstract: The structural integrity of precast concrete structures depends mainly on the connections between the precast structural elements. The purpose of a connection is to transfer loads, restrain movement, and/or to provide stability to a component or an entire structure. Therefore, the design of connections is one of the most important aspects in the design of precast concrete structures. All connections should design with valid codes. Every precasters have developed connection details over the years that suit their particular production and erection preferences. It is common, that the structural engineer to show loads and connection locations and allow the successful manufacturer’s engineering department to provide the final design and details of the connections.

Abstract: There are many analytical methods to solve internal forces of slabs. But structural engineers work with structural analysis software, based mainly of finite element method (FEM). Interpretation of that analysis results may lead to errors during concrete slab reinforcement design. There are some methods to solve the problem. Most familiar are Wood-Armer equations, introduced in 1968. But other methods exists furthermore. It is common, that design engineer doesn’t know, which method his program uses. This article deals with common – not only Wood-Armer - methods of concrete slab reinforcement design incorporating twisting moments, design of skew angle reinforcement etc. Description of selected software approach.

Abstract: The subject of the article is to apply the European standard when appraising the element’s bearing capacity in concentrated pressure under the anchoring slabs of pre-stressed reinforcement units. Method of concentrated pressure analysis. Method of performing expertise of the effects of lateral tensile forces. Local compressive load distribution model under the surface of the reinforced concrete element. Lateral tension in the local compressive load’s distribution area. Reinforcement against tearing of the surface of elements. Application in the expertise of the class of concrete in foundations.

Abstract: Fire exposure of a construction represents an accidental load (temporary with a high intensity) and it´s appearance during service life of the construction is improbable. All structural eurocodes, which deal with the normal temperature (20°C) design of structures made from loadbearing materials (steel, steel and concrete composite, concrete, masonry and timber), include always Part 1-2: Structural fire design. Concrete, similar to the masonry, has (in comparison with other construction materials such as steel and timber), an excellent resistance against fire exposure. This is why both of these materials are used for construction of fire walls, which create barriers against the fire spreading. Fire walls separate two spaces and they are designed for fire resistance and structural stability, including resistance to mechanical impact. In the case of fire and failure of the structure on one side of the fire wall, fire spread beyond the wall is avoided. Properties of concrete and masonry walls, subject to fire exposure, are however negatively influenced. Concrete compressive strength is reduced depending on the aggregate choice. The strength of reinforcing bars is also reduced at elevated temperature, by an amount which strongly depends on the axis distance of the reinforcing bars from an edge of a cross section, too. The behaviour of a masonry wall depends on a masonry unit type and material, type of the mortar, the density of units, type of the wall construction, and applied surface finishes. In the present article we discuss basic principles of the design and assessment of various concrete and masonry fire walls and compare their effect - fire resistance period – depending on their thickness.

Abstract: The article is a review of solutions, errors and mistakes in the project design and execution and their impact on reliability and durability of structures. Were used the results of inspections of 95 precast residential buildings situated in Warsaw, build in years 1961-1994. Inspections were made in years 2005-2006 and 2014. The summary of author researches [1,2,3,4] shows that the precast concrete prefabricated buildings can achieve real duration of use not less than 100 years. Taking into account quite good maintenance, intensive modernization and greater economic value of the housing stock in Warsaw can be assumed that their service lives may reach 120-150 years.