Many structural concrete elements of dams must withstand extreme frost stress and abrasion of fast-flowing water. At present, several reconstructions of concrete overflows, chutes of dams or weirs are underway or have already taken place with the requirement for increased resistance to abrasion. From the point of view of ČSN EN 206, abrasion-resistant concretes are determined by exposure class XM, but the evaluation criteria and testing methods are insufficient. The article deals with a closer presentation of the requirements for the properties and development of concrete with high resistance to abrasion and frost and its subsequent testing.

The paper is presenting problems that are to be solved within expert opinions focused on wooden houses which foundation is designed as a crawl space.

Textile-reinforced concrete is currently a newly developed material and can be used as an alternative to traditional reinforced concrete structures.It is a combination of high-performance concrete, textile carbon reinforcement, and its synthetic matrix. The main advantages of textile-reinforced concrete are its mechanical properties, while retaining a subtle structural character,and excellent resistance against atmospheric corrosion. Currently, textile-reinforced concrete is used mainly for non-load-bearing structures; however, more widespread usage in load-bearing structures is predicted. This article serves as an evaluation of textile-reinforced concrete in load-bearing structures from the fire safety of buildings‘ point of view as well asa stating prospective limitations resulting from the requirements of the set of standards series CSN 73 08xx.

The present experience has shown, that the most serious effect of the accidental load on prefabricated panel buildings in our conditions is a gas explosion. In addition to the explosion of gas, the effect of elevated temperature during a fire is also significant. During a fire, the mechanical properties of building materials may change. These may not return to their original value at the end of the temperature load. The article describes the design of repair of the load-bearing members the panel building after fire on the 11^th floor of the panel system type T-06.

Article follows the previous treatise concerning prestressed steel tubes with just one crossarm (Machacek a Pichal [13]). A stayed column with two crossarms is investigated, while other parameters as those of tested and analysed stayed columns with one crossarm are identical. Critical loadings and decisive buckling modes of unprestressed stayed columns are solved by linear bifurcation. For prestressed stayed columns the analytical method is derived, which enables calculation of critical loading under an arbitrary prestress including the optimal one, resulting into maximal critical loading. The main study introduces geometrically, possibly also materially nonlinear analyses with initial imperfections, using software ANSYS. The nonlinear analysis is shown to be necessary even for critical loading of "ideal" stayed column, while for strength of "imperfect" stayed column, with given initial deflection, is absolutely essential. Finally are analysed impacts of material nonlinearity and numbers of crossarms, followed by practical design recommendations.

Article follows the previous general treatise concerning prestressed steel compression tubes with just one crossarm (Machacek [1]). This article deals with tests of stayed columns, numerical analyses and their evaluation. In the theoretical part the linear bifurcation analysis (2D LBA) to establish critical loads and buckling modes is presented, the geometrically nonlinear analysis to establish strengths of imperfect stayed columns (3D GNIA) and also the geometrically and materially nonlinear analysis to establish strengths of imperfect stayed columns made of stainless steels (3D GMNIA) are introduced. Numerical calculations employ software ANSYS and are validated by tests. Parametrically are investigated impacts of initial deflections, directions of buckling, material nonlinearities and the technique of the stays supports at crossarms. Results are summarized into practical recommendations.

The aim of the study was to determine the functional reliability of the historic wall of the Hvězda summer house and to assess its applicability. The article presents the possibilities of freestanding wall renovation design using optimal technologies, analysis of solution proposals and evaluation of risk factors. The actual design of the renovation was preceded by a detailed structural survey. At the end of the article, the course of implementation work is described, including the selected material solution of restoration. The Klokner Institute of the Czech Technical University participated in the material analyses and the renewal proposal was consulted with the National Heritage Institute.

Carbonatation of concrete (or possibly of cement grout) is a slow destructive process, which continuously causes the change of pH, the corrosion of reinforcement, up to the total loss of strength and cohesion of concrete. It seems, however, that the carbonatation process can be partially influenced by a composition of concrete mixture and by perfect dumping. Greater batches of cement, preferably portland cement, guarantee the best natural preservation of concrete. On the contrary, negative effects of carbonatation demonstrate themselves stronger in the worse dumped concrete and also in concrete with excess of batching water. Finding a suitable recipe for a concrete mixture together with a perfect processing technology lead to a significant prolongation of lifetime of concrete constructions exposed to invasive action of gaseous carbon dioxide.

The addition of structural fibres to concrete has a positive and negative impact on the long-term life of concrete. Polymer fibres, given their low flexibility module, do not always help the concrete to sustain its diverse deformations. Steel fibres on the other side create a hard skeleton to prevent varied deformation, but with the possibility of negative separation of cement paste from fibres. The state of the pore structure of fibre concrete exposed over a long period of time in the CO₂ environment can be detected using the method of determining the diffuse resistance coefficient and alternatively the method of determining the capillary elevation. During the process of long-term carbonation of fibre concrete, significant changes occur in the observed values of both physical quantities -- that is, the diffuse resistance coefficient and capillary elevation.

White tanks are structures which, in addition to the load-bearing function, must also have the function of watertightness. Watertight of the concrete is ensured by adherence to design, production and technological measures. The width of the early-age cracks that former in the structure is controlled by the reinforcement. During construction, however, joints (expansion, construction and control) are created in the structure, which must also be watertight. The joints are the most sensitive place of the white tank and therefore the most leaks are created at the point of the joints. The correct choice of the joint sealing system is the basis for the design of the watertight joint. The paper deals with the description of various joint seal and pipes through of the white tank.

The mass construction of apartment buildings using the technology of large-format prefabricated prefabricated elements in the former Czechoslovakia took about 40 years. The lifetime of these buildings is approaching their planned value. A common problem of prefabricated buildings is the creation of new openings in load-bearing structures without prior expert appreciation. The important details of the joints of the support elements have changed not only between the individual assemblies, but also during the development of the particular assembly. The article describes some problems of load-bearing structures of prefabricated buildings, which designers have to consider in their assessment.

The construction of precast hous consists of prefabricated concrete walls and floor slabs. These elements through joints form rigid spatial (so-called box) load-bearing system. The prefbricated elements of this system were designed for certain layout and static possibilities of the panel system. All additional interventions in the load-bearing structure must be thoroughly investigated. If necessary, it is also necessary to propose a suitable way of strengthening the weakened parts of the load-bearing system.

This article is focused on current situation in preparation of new generation of European standard for design of concrete structures prEN 1992-1-1. This article deals with main features and development in design principles involved in new standard. In these days there is available the 4th draft of standard for comments of national authorities and experts. The final draft of prEN 1992-1-1 should be finished this year (2020) and provided to formal vote in CEN.

Eurocodes EN 1991 for the basis of structural design and EN 1991 for actions, currently under development in the Technical Committee CEN/TC 250, should be more user-friendly in the 2^nd generation of Eurocodes. They will provide basic design procedures, new types of actions and improved theoretical models which will be applied for the design of structures. For effective and economic implementation of 2^nd gneration of Eurocodes into the systém of Czech standards, correct decision on National Determined Parameters is needed.

The article presents the basic criteria in the evaluation of structures of historical buildings. The whole procedure is described in detail in EN 13822, Annex I. The intention is also to provide additional guidance on the application of this International Standard for the construction of cultural heritage buildings. The instructions given here are to be followed in conjunction with all other clauses of the internationally applicable standard EN 13822 and other regulations.

The paper deals with the constructions from jet grouting (JG), which is one of the most modern methods of special geotechnical works. JG is the technique of mixing in-situ soil with the energy of high-pressure jet of slurry. The definitions and types of JG are given in the first part: single fluid, double fluid and triple fluid. The second part concerns JG implementation technology and also lists the necessary activities in designing and implementing JG elements and structures. In the third part, examples show the field of use of JG, including deep foundations, for which the example of static load test is given.