Mariusz Maślak

The history and structure of the historical covered wooden bridge built over the Osam River in the Bulgarian town of Lovech is described and discussed in detail. This bridge was completed in 1874 by Kolyu Ficheto and had a total length of approximately 86 m. The original bridge burned down in 1925. Its present structure is partially made from reinforced concrete and was opened to the traffic in 1931.

An alternative design approach, helpful in the critical temperature evaluation for a gable steel frame exposed to fire, is proposed and discussed in this article. This approach is based on the specification of a system of equilibrium formulae, generalized to the case of fire. All these equations result from the graphical identification of the redundant bending moment distribution in the frame members relating to the particular collapse mechanisms being kinematically admissible. Only such a mechanism which corresponds to the activation of a suitable sequence of the appropriate number of plastic hinges while maintaining the requirements of the classical bending moment redistribution is recognized as conclusive for the considered frame structure.

Multicriterial evaluation methodology, adequate for identification and for arrangement of different-sourced risks interrelations being specified in the building process has been presented and discussed in detail in context of sustainable building requirements. The design algorithm, proposed by the authors, is based on the generalisation of the expert-decision--approach, recommended in classical DEMATEL procedure.

The specifics of a forecast fire development in a single fire compartment consisting of a shopping hall characterised by a large area and a relatively low height are analysed in this paper. The fire initiated locally, and after initiation, depending on the ventilation conditions in the zone, more or less intensively spread to the neighbouring areas with or without full development. The propagation of hot exhaust plume was simulated within the environment of the FDS computer code. Three formal models differing in zone size and stacking height have been subjected to analysis. The influence of automatically activated smoke vents has been accounted for.

In this article, selected examples of heritage wooden bridges, which were built over the centuries in various parts of the world, are presented and briefly discussed. The overview allows the observation of not only the continuous progress in the techniques used to construct bridges of this type but also the variety of the design solutions applied.

In the second part of this article, the development of the timber bridges is shown in detail in relation to the historical and cultural contexts specific to different regions subjectively selected from around the world. For such a purpose, some iconic timber bridges are presented and discussed on a country by country basis. Their mutual comparison allows us not only to appreciate the craftsmanship of both ancient and medieval builders but also to see the diversity of the proposed structural solutions.

The acceptance in advanced fire safety analysis of the formal model according to which the probability of fire occurrence is assumed as time-independent leads to the conclusion that random fire episodes in considered building compartment can be described by the formalism of a Poisson process. In the presented paper some consequences of such adoption are presented and widely discussed as well as the foundations are determined of the equivalence between this probability and a conditional failure rate, which is interpreted as a process intensity parameter.