Abstract:The design of multi-span structures post-tensioned with unbonded tendons may differ from the assigned one for reinforced structures or structures post-tensioned with bonded tendons. In some cases Ultimate Limit State can be reached by different loading patterns to which we got used to i.e. load cases which result in maximum values of bending moments in spans and at supports. This behaviour is related to the lack of bond between concrete and strands and the assumption that the force in tendons has a uniform value between anchorages.
Abstract:This paper covers the experimental studies of Young’s modulus of concrete on the basis of eigenfrequencies. Experiments were performed on beam elements measuring 1050×200×100 mm, using operational modal analysis (OMA). Two types of concrete with different mixtures were tested. The dynamic Young’s modules were calculated on the basis on the resonant frequencies measured in two directions. The values obtained were compared with static Young’s modules determined on concrete cylinders in axial compression testing.
Abstract:This paper presents the technical condition assessment of a RC digestion dome chamber after fourteen years of exploitation. The authors conducted experimental investigations, i.e. tests of concrete compressive strength using a scleroscope, concrete chemical analysis in the laboratory and detections of reinforcement. On the basis of the obtained results and cracks morphology, static-strength calculations were conducted. The results of the FEM numerical analysis indicated deficiencies in the bearing capacity of the dome. The widths of the calculated cracks exceeded allowable values. The authors proposed two alternative methods of chamber strengthening: pouring additional RC dome cover or post-tensioning the dome with external unbonded tendons.
Abstract:In 2014, a new tank for the storage of liquefied ammonia (capacity 22 000 m3 ) was built for the chemical industry company ‘Grupa Azoty S.A.’. The LNG terminal in Świnoujście, where two large capacity containers (160 000 m3 each) were built, is almost finished (2015). In both cases, prestressed concrete was used to build a secondary (outer) containment tank.This paper is devoted to general concepts and design considerations for secondary cylindrical, concrete containers for the storage of refrigerated, liquefied gases with temperatures between 0°C and –165°C, according to EN 14620.
Abstract:This paper presents a comparison of pressure for composite laminated cylinders leading to progressive damage of subsequent plies. Laminates made of epoxy resin with glass fibre used in various ply stacking sequences are considered. Numerical calculations based on Mathcad author’s code are performed. Results utilising last ply failure criterion are specified. The effects of subsequent ply angles on load capacity is investigated.
Abstract:In this paper, the results of the numerical analysis of pre-stressed concrete girders made of a high-strength concrete composite with a slab made of normal concrete are presented. A FEM analysis of the construction stage considering the influence of rheological effects on the behaviour of the structure was performed. Results of the analysis are presented in the work and are compared with the results of numerical analysis of the same elements, in which the time-dependent effects are not included. On the basis of these results, appropriate conclusions are proposed.
Abstract:The structural application of shape memory materials is relatively new. It is possible that these materials provide the unusual property of creating stress in steel bars in a thermomechanical way. Depending on the alloy composition and production treatment, the characteristic transformation temperatures as well as the mechanical properties of the material vary and this may limit its technical effectiveness. The present work is focused on the material parameters from the point of view of practice.
Abstract:This paper presents the results of laboratory experiments carried out on twelve clay brick masonry wallettes of two types under cyclic compressive loading. In the paper, the procedure adapted for testing is described and the results are discussed. The failure models and cracking patterns of the tested specimens are presented. The effects of the repeated load on the behaviour and mechanical properties of the wall are observed and discussed. Based on the results, the analytical formula for the determination of the failure envelope curve is also proposed.
Abstract:In one of the oldest chemical plants in Poland are two reinforced concrete towers for fertilizer granulation which were built in the nineteen-thirties. These towers have operated continuously in a very hostile environment for about fifty years. The authors of this paper have used ad hoc methods of repair and protection with varying degrees of success for several years. In 2012, the renovation of one of the towers was designed and implemented with a view to its continuous use over a period of twelve years. A new comprehensive method of protecting the tower was applied due to its relatively long-term use. The resulting tower damage, the results of chemical and structural analysis of the concrete and coating stress are presented in this paper. Furthermore, security methods applied by them and their functionality after a few years of use as well as material and construction details relating to works performed to make the tower operational over the next twelve years are presented.
Abstract:Pretensioned hollow core slabs are one of the most widely applied precast elements in the modern building industry all over the world. Due to the possibility of their use under various support or loading conditions, these elements repeatedly work under a complex stress state. Theoretical analysis of the phenomena of the interaction of shear and torsion in the above-mentioned HC elements is presented. The theoretical basis and design regulations of the computational model included in code PN-EN 1168+A3:2011 along with parametrical analysis of that model are demonstrated. The largest experimental research program of hollow-core slabs under shear and torsion conducted thus far is also briefly described – this study was carried out in Finland in 2004 and was the basis for the development and calibration of the numerical computational model formulated in Chalmers University of Technology in Göteborg, Sweden.
