Approximation approach for personal estimation in safety analysis of existing structures

Different studies in recent years show that many structural failures are due to errors in planning, design, construction and utilization. These are difficult to quantify and have not been considered in probabilistic design methodologies (reliability theory). In practice the designer must use his practical experiences, the actual conditions and the pure speculations when evaluating safety factor values. Therefore, the reliability of structures is not only an objective but also a subjective concept, which is a property of the designer's state of knowledge. They need a way of combining all the subjective information, which are of multivalued nature and come from multiple sourcesof estimates.

In this study an inferential method applying fuzzy set and fuzzy logic to analyze safety of the existing structures is presented.     

High-temperature internal sulphur corrosion of H 18 N 9 steel

The paper presents some results of investigations into the high-temperature corrosion of the CrNiSi steel H 18 N 9 S in atmospheres containing sulphur and oxygen. Specimens of the steel H 18 N 9 S were exposed at various temperatures to an atmosphere containing 47% Argon, 50% hydrogen, 3% hydrogen sulphide and about 0.2% oxygen. Corrosion was connected with intense internal sulphidation. This process causes a decrease of the chromium content in the metallic matrix and, consequently, γ→α transformation. In the temperature range between 830–930°C the thickness of the external scale is by 6 to 10 times smaller than that of the internal sulphidation zone.     

Zur Optimierung der Eigenschaften von Eisenerzsintern

Untersuchungen zur Reduzierbarkeit und Festigkeit von Sintern mit verschiedenem Basengrad im Bereich von CaO/SiO₂ = 0,38 bis 2,20 sowie mit verändertem Eisen(II)-oxidgehalt von 6 bis 16%. Mineralogischer Aufbau der Sinter sowie Abhängigkeit der Textur und des Phasenbestandes von Basengrad und Eisen(II)-oxidanteil. Änderungen von Mineralbestand und Textur nach der Reduktion bei 950 °C und nach schwach reduzierender Behandlung bei 500 °C.     

Epoxidation of allyl alcohol over mesoporous Ti-MCM-41 catalyst

Epoxidation of allyl alcohol with 30 wt% hydrogen peroxide over Ti-MCM-41 catalyst under atmospheric pressure and in the presence of methanol as a solvent has been studied. The influence of the following parameters: temperature (20–60 °C), the molar ratio of AA/H₂O₂ (0.5–5), methanol concentration (5–90 wt%), catalyst concentration (0.1–5.0 wt%) and reaction time (5–180 min) has been investigated. The process has been described by the following functions: the selectivity of transformation to glycidol in relation to allyl alcohol consumed, conversions of the substrates and selectivity of transformation to organic compounds in relation to hydrogen peroxide consumed. The technological parameters, at which the functions describing the process take the optimum values, have been established.     

Losses of chemical energy in hard-coal energy-utilization exothermic processes

In the sequence of occurrence, these processes are the losses in coal production, processing losses, and the losses in electrical-energy generation. These losses are evaluated.     

Robotics in Civil Engineering

Abstract: Robots have been investigated for automation of construction, maintenance, and inspection of civil works since the early 1980s. This paper describes the progress of robotics in civil engineering from the early 1980s to the mid-1990s. It focuses on the environment and motivation for implementation of robotics, identifies key centers of development, identifies regional differences, and describes progress in key areas. It also traces the emergence and change of development strategies over time, it identifies practical achievements, and it identifies key developments for the future. It concludes that despite many false starts and setbacks, significant progress has been made, and significant changes are on the horizon.     

Postfault Analysis of Operation of Distance Protective Relays of Power Transmission Lines

This paper deals with the postfault analysis of the operation of distance protective relays from the line terminals. The signals of the digital distance relays are processed in the offline regime with the aim of evaluating the particular relay operation case. First, the program enables imitating the fault-loop impedance measurements of the distance relays. Second, the two-end unsynchronized measurements of the relays are considered. The unknown synchronization angle is determined by using the developed noniterative procedure. Then, the distance to fault is calculated. It is applied for calculating the actual values of impedance for the line sections. Comparing the results of these two ways performs analysis of operation of the relays under resistive fault cases. The described postfault analysis algorithm has been tested with the fault data obtained from versatile Alternative Transients Program-Electromagnetic Transients Program simulations. The examples are reported and discussed     

Simulations and analyses of arched brick structures

The paper presents problems related to the assessment of historical objects, especially brick arch structures, in view of potential improvement of their strength using various technologies. We have presented the methodology and computer simulations used for assessment of present strain and load bearing capacity of brick arches along with a variety of reinforcement techniques. We also present arch deformation FEM analysis along with results of assessment of actual objects.