Jiří Štoller

Traditional risk modeling techniques, such as statistical and probabilistic methods, which form the basis of risk estimation and analysis, are not always economically or socially effective tools in construction. This is due, among other things, to the discrepancy between the planning period of a project and its implementation and sustainability. Static or dynamic methods of measuring the effectiveness of projects are commonly used, as well as operational methods to solve problems in specific decision-making situations. The inclusion of subjectivity and the lack of complete and precise information severely limits, and sometimes even prevents the use of traditional methods. Applying fuzzy set theory to model complex issues such as risk seems a desirable and justifiable measure in such a case. The application of fuzzy sets in construction is not a new issue. However, most research studies on the use of fuzzy systems in the construction industry have proved to be either too simplistic or too detailed, therefore fuzzy risk assessment matrices have been proposed. The proposed alternative risk assessment methods are based on fuzzy set theory while considering standard recommendations. The paper discusses basic information on design strategies for building structures taking into account standard recommendations for modeling and risk assessment in construction. An example illustrating the application of the proposed qualitative and quantitative risk estimation methodology to a bridge structure is also included.

Bridges are often built in complex geological-engineering conditions, on difficult soils, landslide areas or within the range of negative mining influences. These objects are classified as geotechnical category II or III and a ground investigation documentation or geotechnical design should be carried out for them. The correct investigation of the soil, design, and execution in accordance with technical knowledge, the art of construction and the Building Code are a guarantee of the safety of the facility. However, very often it is the complexity of the geological structure, concentrated vertical and horizontal loads transferred by the supports to the soil that make it necessary to use deep foundations, special methods of soil reinforcement and imposing a special technological regime during the execution of construction works. The paper pays attention to anthropogenic and natural factors, as well as those that are the consequence of inappropriate human actions at the design or execution stage. Particular attention is paid to errors in the soil analysis and execution of construction works. An example of such errors analysis is presented in relation to the implementation of a bridge structure.

The reliability of numerical simulations of the structural response of nonhomogeneous materials to high velocity loadings is highly dependent on the used material model and parameters. For nonhomogeneous materials, such as fibres, reinforced concrete is widely used for the Winfrith model, but the question of appropriate material parameters for Ultra-High Performance Fibre Reinforcement Concrete (UHPFRC) under high velocity loadings is still open. The article deals with possible method of inverse identification of material parameters of a UHPFRC slab under blast loading for a Winfrith material model. Possible application is in the field of numerical simulation of protective or critical infrastructure response to blast loading. Experimental measurement of the time–deflection curve through laser scanning using the triangulation method gave us input data for an inverse identification phase conducted in Optislang software. Obtained material parameters from a given range are optimized for blast loading and their Pearson’s correlation coefficient provides us information about their significance for simulation.

The article deals with the issue of the energy efficiency in military camps. The military camps are mostly built during military deployments in case of exercises or missions. As different kinds of temporary structures are typically used to shelter large part of the camps’ facilities, the area of improvement for better energy efficiency lies mainly in the utilization of energy efficient devices, machines and pieces of equipment that are used by deployed personnel. The resulting lower energy consumption does not only bring lower financial and logistical burden to the military units but also contribute to the lower environmental impact of military activities. And ultimately, lowering energy use, especially fossil fuel, may result in cleaner environment and significantly affect health of deployed personnel. Overall, there are many benefits brought by energy efficient devices and equipment in several overlapped areas in military camps and their surroundings.

Fortification structures, both military and civilian, are designed to resist a blast explosion to some extent. Their technical condition after a blast load must be assessed in a fast and reliable way to enable the users’ decision about the future use of the structure. Preferably, for the assessment of the protective structure, the non-destructive testing method should be used. To assess the suitability of ultrasound testing method for fortification structures built from steel fiber reinforced concrete, an investigation in a laboratory and in situ was conducted, together with numerical simulation and statistical evaluation. The numerical simulation of the blast load of a steel fiber reinforced concrete slab was conducted using multiphysics simulation software with the aim to verify basic parameters of the field experiment. During the field tests, several slabs were loaded by plastic explosive and changes in the structure of the slabs, before and after the blast load, were examined using the ultrasound pass-through method. After the field tests, the slabs were subjected to a destructive laboratory test to determine their residual strength. Subsequently, the data sets obtained from the measurements were tested using functional data analysis. The results from the ultrasound pulse method show that specimens after a dynamic blast load can in some cases increase the strength of their cement matrix.

This paper deals with analytical assessment of deflection od thick concrete slabs under shock and impact loading caused by the blast wave. The process started with the determination of the shock wave characteristics and the loading which the wave causes. Based on the experimental measurement, the peak was obtained. Subsequently, the reflected overpressure was calculated together with the transformation of the shock loading to quasi static loading. The experimental measurement to determine the strength of concrete of the concrete slab was carried out in the next step. Based on these input parameters, the deflection of the slab was calculated with analytical approach and compared with the experiment measurement, where both results show agreement. From the analytical assessment process, it can be concluded, that the analytically obtained results shows dependence on the input parameters mostly connected to the assessed material, therefore their determination is essential.

The protective structure is designed to protect the live force against the impact of a shock wave and projectiles, it cannot be diagnosed by the destructive method which devalues the protective structure by sampling. The authors are looking for a combination of suitable non-destructive technology (NDT) methods that would be used in the future to prove the degree of damage to cement-based protective structures after an explosion. This article represents the first part of an experiment designed to verify the applicability of NDT methods, to evaluate the degree of damage of the protective structure in the field. The experiment consists of three parts. The first part is a laboratory verification of the initial material characteristics of the materials used. The first test set of structural elements is made of steel fiber-reinforced concrete. The elements are evaluated using NDT methods and for comparison by destructive laboratory methods. The second part is the impact of structures using explosion and evaluation of the condition of structures using NDT methods in the field. The last part is used to verify the results of the NDT method, which ensures the residual strength of the structure in the laboratory and try to find the relationship between changes in the results of NDT methods and the residual strength. Radiography was included in the introductory and concluding parts of the experiment to verify the results. Although this method is not suitable for using in-situ, it is the only standardized method of the NDT methods used.

At present, steel fibre reinforced concrete can be classified as a composite material commonly used for load-bearing building structures. Adding steel fibers to fresh mixture improves its mechanical properties in comparison to plain concrete. The problem is, however, the production technology, which has not been standardized by regulations so far, and thus, proposals for the amount of steel fibers added to the mixture are still based on the long-term experience and performed tests. The paper describes an experiment focused on the determination and assessment of mechanical properties of steel fibre reinforced concretes with high concentrations of fibres (40 kg/m³, 80 kg/m³ and 120 kg/m³). To better understand the behavior of test specimens during the three-point bending test, the acoustic emission method was used, which is able to capture active defects. The results show that the increasing amount of fibers has the influence on values of F_Rk,0.5 and F_Rk,res,1 (e.g. for concentration 40 kg/m³ is F_{Rk, 0.5} = 13.27 kN and for 120 kg/m³ is F_{Rk, 0.5} = 21.18 kN).