Shota Urushadze

The Response of Masonry Barrel Vaults to Repetitive Static and Dynamic Loads and Example of Rehabilitation of Historic Barrel Vaults

The article will present the main results of experimental and theoretical research into non-reinforced barrel vault constructions and barrel vault construction reinforced with composites based on high-strength fibres and epoxy resin, or special polymer cement mortar. Vaulted constructions of historic and heritage buildings are extremely sensitive to deformations of the supporting construction, and their response to seismic effects may often be accompanied by cracking and mechanical vault failures. The results of research and study into the dynamic behaviour of barrel vaults brings new knowledge applicable in the prevention of vault failures in regions with an increased intensity of natural or technical seismicity, for the identification and localisation of failures using e.g. MAC or COMAC criteria. It can also be valuable in their serviceability assessment and service life extension. The second part of the article presents the results of theoretical and experimental analysis and a practical example of the stabilisation and reinforcement of 16 extensively damaged barrel vaults (with a 3.05 m span) with large lunettes situated over the cloister in the Premonstrate Monastery in Tepla (built in the 16th century), located in a seismically active region of West Bohemia.

The Influence of Bell’s Swaying on Neo-Gothic Cathedral

One of the negative aspects of technological progress is the threat to historical heritage by the impacts of technical seismicity. Dynamic load represents a significant threat to the safety and durability of historic buildings. The long-term effects of these types of loads lead to degradation of materials and connections, cause the occurrence of cracks and can increase the size of these cracks, and potentially lead to large-scale damage. Loads which would be safe for undamaged structures could become critical. This risk is present for various types of historic buildings; differences may occur due to the condition of walls, the amount of dynamic load and maintenance quality – which also includes the timely identification of damage (building diagnostics) and subsequent timely (and hence not too expensive) repairs. The aim of this paper is minimizing the effect of the bell’s ringing on the Church.

Vortex-Induced Vibration of Stay Cables, Verification on the Footbridge

Long-span footbridges rank among engineering structures with a high social significance. Their architecture design must in general satisfy matters such as attractive look, reliability and light. These requirements predestinate the bridge to be sensitive to the wind effects and the assessment against the wind becomes crucial. One of the several wind phenomena occurring on such a type of structures is termed as the vortex shedding. This flow induced excitation lying in a periodic vortices separation may arise at low wind velocity on both the main parts of a bridge structure including bridge girder with pylons and additional members such as stay cables, hand railing, etc. According to the character and intensity of the excitations, the adequate treatment to reduce or avoid the oscillations should be given. It is also performed when the vortex induced oscillations do not influence the reliability of a footbridge, but the look at the amplitudes could start panic and could start vandal’s action – increasing the amplitudes.

The “Miracle” of Post-Buckled Behaviour in Thin-Walled Steel Construction and its Breathing-Induced Limitation

Thin-walled construction represents a powerful tool for saving steel and thereby for increasing the competitiveness of steel structures. However, on the other hand, as the limit state of thin-walled structures is substantially affected by stability phenomena, the above concept can be implemented just on the condition of post-buckled behaviour being taken into account in the solution to these stability phenomena. The paper first briefly studies the factors on which the intensity of the very favourable post-buckling reserve of strength depends and then in detail turns attention to the most important among them, viz. the effect of the cumulative-damage process that becomes manifest in the case of bridges and other systems subjected to many times repeated loading.

Wind Tunnel Experimental Study of Coupled Rocking-Swivelling Model of Guyed Mast Shaft

Systematic monitoring of rotational vibration (both torsion and swivelling) of guyed mast shafts has been performed in ITAM since 2005. The occurrence of this phenomenon is conditioned by the fact that the guy ropes are attached to the construction of the shaft, i.e. out of its axis. The simple static calculation model serves for making the proof of the occurrence of the torsional moment, affecting the shaft, which is guyed by three ropes. The exact theoretical solution of the real phenomenon assumes the introduction of dynamics of guy ropes, which vibrate in 3D shapes during the shaft’s movement along the orbit and it ́s torsion (swivelling).

Problems Connected with the Application of Lamella Flanges in Steel Bridge Construction

Lamella flanges (Fig. 1) have lately grown popular with the designers of steel bridges –in their belief that these flanges provide us with the possibility of avoiding very thick flange plates in steel bridge structures. This belief is based on the assumption that the lamellas are perfectly plane and, therefore, in perfect contact everywhere, so that the loading from one lamella is transmitted into the other via pure compression, and that the perfect interaction of both lamellas is materialized by means of boundary fillet welds connecting both of the two lamellas. This simple assumption is, however, far from reality: it is not in the means of steel fabricators, not even in the means of those which are very progressively equipped, to produce perfectly plane flange lamellas. Then both lamellas exhibit unavoidable initial curvatures, which in combination form a gap between the lamellas, and consequently the directly loaded lamella is pressed into this gap. As the loading acting on every bridge is many times repeated, the aforesaid phenomenon is also many times repeated, (we can say that the lamellas „breathe“), and then an unavoidable cumulative damage process in the lamellas comes to being.

Experimental Study of Torsion of Guyed Mast Shaft

The torsion of the mast shaft has been monitored on several masts in the Institute of Theoretical and Applied Mechanics (ITAM) since 2005. The occurrence of this phenomenon is conditioned by the fact that the guy ropes are attached out of the axis of the mast shaft. An experimental mast-shaft model of 15 m height guyed in 3 directions was used for the more detailed study of its rotational motion. The excitation was realized by transversal auxiliary rope drawn by harmonic human force in resonance. The displacement of the shaft top results in translation caused by the guy force and the rotation, caused by the eccentricities of the guy-ropes, attached out of the shaft axis. The resulting movement of the shaft support is an elliptical orbit. The shaft of our experimental mast was equipped in two levels with accelerometers for registration of horizontal x, y motions. The two x, y signals in two levels were monitored and analysed.

Breathing-induced Fatigue in Thin-walled Construction

Abstract The cumulative damage behaviour generated by web breathing was analysed, the process of the initiation and propagation of fatigue cracks induced thereby was studied, and their impact on the failure mechanism and the fatigue limit state of the girders was determined. It was found out that the above phenomenon led to a significant “erosion” of the beneficial post-buckled reserve of strength. Therefore, S-N curves were established for (i) the fatigue limit state and (ii) the onset-of-the-first-fatigue-crack limit state, specifying those periods after which checks for the appearance of fatigue cracks in bridge plate elements need to be carried out.

The Breathing Phenomenon in Thin-Walled Steel Girders – Experimental Investigation and Impact on Design

Thin-walled and economic-fabrication construction. The post-buckled behaviour of slender webs and an experimental investigation into its partial “erosion” under the effect of many times repeated loading. A simple and user-friendly design method based on the authors´ experiments.

Monitoring of Torsion of Guyed Mast Shafts

Systematic monitoring of torsion (swivelling) of guyed mast shafts has been performed in ITAM since 2005. The occurrence of this phenomenon is conditioned by the fact that the guy ropes are attached to the surface of the shaft, i.e. out of its axis.