Papers by Author: Petr Fajman

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Authors: Petr Fajman
Abstract: This Traditional joints used for the restoration of historical timber structures are not designed according to standards. A very common joint is a vertical splice skew with a key. Unfortunately, the forces mutually acting in its separated parts are not known. It is only their limits that may be derived with some accuracy, but even this is very valuable for practice. The accurate values may be obtained from measurements or experiments.
Authors: Petr Fajman, Jiří Máca
Abstract: One of the most impressive membrane structures in our country is the roofing of the K Barrandovu tram stop in Prague. Cable and membrane structures must permanently be kept under tensile prestress. The stress magnitude at zero load depends on the structural design, the final shape of the structure and its shape in production. The measurements of 2009 and 2012 pointed out the problem that some cables showed zero prestress.
Authors: Petr Fajman, Jiří Maca
Abstract: The bearing capacity of a scarf joint depends on the length of the joint and the type of connection. It is possible to use circular bolts or squared dowels. Both connection tools used in the repairs of historic timber structures are made of wood according to the requirements of the heritage authority.
Authors: Milos Huttner, Jiří Maca, Petr Fajman
Abstract: This paper presents a practical application of form-finding process of cable-membrane structures. The dynamic relaxation method with kinetic damping is used as the computation method for numerical analysis. A brief description of the construction, a description of the models and the way of solving tasks will be introduced. The correct operation of the implemented algorithm will be compared with a commercial program.
Authors: Miloš Huttner, Petr Fajman
Abstract: This paper is focused on carrying capacity testing of five different types of membrane connections. Three reference samples for each type of connection were tested for tensile strength. Low measured peak force value and especially the way breakage outside of the join indicative of a wrong material, and not on the connection. The obtained values were compared with technical datasheet of the material manufacturer, which has been non-compliance. It confirms the assumption that the material was changed, which could harm to the user.
Authors: Michal Polak, Petr Fajman, Jiri Maca, Tomáš Plachý
Abstract: The cable-stayed bridge at the inner ring road in Prague in the Czech Republic was put into operation in 1997. In 2008 a crack was found in the bridge structure area where the end beam was connected with the upper deck of the box section and where the bridge expansion joint system was anchored. The basic objective of diagnostic works, which were started immediately after the finding of the crack, was obtaining the basis for bridge structure modifications, among other things, to prevent formation of similar damages in the future. A series of diagnostic methods was used for determination of the bridge actual state and the real static and dynamic bridge behavior. One of these methods was the dynamic load test. It was focused on an examination of the bridge forced vibration which was caused by dynamic effects of a usual traffic flow. An arrangement of the test was not quite usual because the experiment was concentrated on dynamic behaviour of bridge support areas especially. The abutment area, the pylon area and the area of a pillar with the bearing with a tensile structural element were observed on the investigated bridge. The dynamic load test was performed in two stages. The first stage was focused on investigation of bridge dynamic behaviour in original structural conditions and on obtaining the basis for design of bridge adjustments. The second stage was realized after bridge reconstruction in December 2012 and verified the effectiveness of bridge modifications.
Authors: Milos Huttner, Jiri Maca, Petr Fajman
Abstract: This study is focused on the form-finding process of cable-membrane structures using the dynamic relaxation method with kinetic damping. Eight different schemas of the dynamic relaxation method are compared in the paper. The effect of mass distribution along the structure is also of interest. The efficiency and stability of each process are compared on selected 3D examples of cable-membrane structures.
Authors: Petr Fajman, Jiri Maca
Abstract: Repairs of historical timber structures lead to connecting existing and new beams. The requirements for beam authenticity make use of older ways of connecting. The first type is the splice of beams in bending with the scarf joint, rafters and tie-beams are joined with the dovetail and, finally, the connection of the main joist with the strut is by the mortise carve.
Authors: Miloš Huttner, Petr Fajman, Jiří Maca
Abstract: This paper is concerned with the selected aspects, which are discovered during a design stage of cable and membrane structures, known as “form-finding” process. The aim of this paper is the understanding of the basic principles of the form-finding process and their explanation of the very simple examples. The use of the finding a shape of a tension membrane that is in static equilibrium as an analogy with the search condition of minimal surfaces is explained. The basic principles are demonstrated on simple 2D example, in which the finding a stable minimal surface passes in the finding a stable minimal length.
Authors: Petr Fajman
Abstract: The basilica st. Jiri on Prague Castle has two towers and three bodies. The north tower is deflected from vertical about 450mm. During the last measurement it was found, that the walls were diverted too. The reasons and beginning of fault genesis have not been known yet. It can be larger self weight of tower then weight of navy. It leads to different settlements during homogenous foundation conditions. The next reasons are not clear. I investigated: tower weakening by the door opening, influence of inside vault over middle navy, foundation conditions. The results obtained from numerical model show that every mentioned reason contributed to the deflection of the tower.
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