Applied Mechanics and Materials Vols. 752-753

Abstract: In this article the hot water test is presented on thin UHPC slabs that are reinforced by a new type of armature. It is a textile armature, which should replace the classic metal (steel) armature. Textile armature should not only reduce the cost of production, but, because it is not susceptible to corrosion as conventional steel armature, panels can be designed with significantly less cover thickness in achieving similar or longer lifetime of these elements. The combination of UHPC concrete with a minimum thickness of cover and textile armature allows design elements weighing up to 70 % lower compared to conventional concrete elements with conventional armature. This can achieve significant savings and benefits not only in economic aspects, but also in environmental aspects.

Abstract: The paper is focused on the problems of the dynamic behaviour, failure and resistance of reinforced prestressed concrete railway sleepers, developed and verified continuously in the period of several last years. The results of dynamic loading tests are presented for the sleepers for both wide and narrow track gauge. The test results have been evaluated using the criteria for the acceptance based on the load corresponding to the prescribed crack width and the load at the moment of total fracture.

Abstract: Cold-formed steel (CFS) is known to be a thin section. Thus it is considered a weak slender steel section which limits the compression capacity of the column. The aim of this study was to determine the ultimate capacity of built-up lipped CFS (assembled with ferrocement jacket) as composite column (CFFCC) under axial compression load. Nine specimens of composite columns were prepared and tested. The main parameters that varied in the CFFCC columns were column height, cold-formed steel thickness, and influence of ferrocement jacket. There were are three different heights of the CFFCC composite column namely 2000mm, 3000mm and 4000mm used in this study. All CFFCC columns were tested under axial load by a thick steel plate. The results indicated that ferrocement jacket provided sufficient lateral support to the column web and significantly increased both the strength and ductility of the specimens under axial loading. The strength capacity of CFFCC improved significantly, about 149% greater than that of bare steel column section. It was also found that the axial load capacity of CFS-ferrocement jacket composite columns (CFFCC) had increased significantly (in the range of 20% to 40%) as thickness of CFS increased.

Abstract: Cold-formed steel (CFS) is known as slender or class 4 section due to high ratio of web-to-thickness ratio. The compressive strength of this type of section is usually very low as it tends to fail due to distortion and warping before reaching the actual compressive strength. The aim of this study is to determine the ultimate capacity of build-up lipped CFS assembled with ferrocement jacket where web-stiffener is provided as the proposed composite column (CFFCC) is under axial compression load. Nine specimens of composite columns were prepared and tested. The main parameters varied in the CFFCC columns are column height, cold-formed steel thickness and influence of ferrocement jacket and web-stiffener. There are three different heights of the CFFCC composite column namely 2000mm, 3000mm and 4000mm used in this study. All CFFCC columns were tested under axial load where a thick steel plate is used to evenly distribute the applied load. The results show the effect of providing both the ferrocement jacket to increase the confinement effect and the web stiffener to provide sufficient lateral support to the column web. A significant increase in both the strength and the ductility of the specimens under axial loading has been recorded. The strength capacity of CFFCC has been improved by about 178% greater than that of bare steel column. Also it is found that, axial load capacity of CFS-ferrocement jacket composite columns (CFFCC) were increased with the increase in thickness of CFS. The use of web-stiffener has improved the axial load capacity of the column but not that significant.

Abstract: This paper describes Finite Element Modeling (FEM) of a composite beam comprised of cold formed steel section and concrete slab designed as ferrocement. Software (ANSYS, version 11) was adopted to carry out the modeling of the proposed composite beam. Experimental tests were also been carried out for three simple supported composite beams. The proposed innovative precast composite beam specimens of cold-formed steel lipped channel sections (CFS) connected with ferrocement slab were tested till failure, under two point loads positioned atquarter length of the span from support. The results showed that close agreement was observed between the FEM and experimental results for ultimate loads and load-deflection responses.

Abstract: To ensure sustainable concrete building industry it is necessary to decrease consumption of natural resources for manufacture of concrete and reduce content of CO₂ produced during production of cement. This approach has not only ecological impact on future activities but it can also considerably reduce cost of concrete. In the Czech Republic, about 6.5 million tons of high quality fly ash is produced during classic high temperature combustion of anthracite or brown coal for production of electric energy. Fly ash produced in such way has high content of SiO₂ and low content of CaO, and it is ranked among co-called siliceous fly ash, which has outstanding pozzolanic properties. This paper describes experience from experimental development of High Volume Fly Ash Concrete (HVFAC), where over 50% of fly ash is used as substitution of Portland cement for binder. High proportion of replaced Portland cement were tested in this research; impacts on strength of concrete at the age of 7 – 180 days, consistency of concrete and other related properties were observed.

Abstract: The aim of this work was to create numerical models of the common truss-type assembling joints of L-profiles. Two different models were created – basic (simplified) model of joint and more accurate model which corresponds to the experimental specimens in preparation. Models with different end-plate thicknesses and consequently with different failure modes were solved. The results obtained from numerical models were compared with the analytical solution of such joints using the Eurocode procedure recommended in EN 1993-1-8. These results are planned to be verified and further developed based on planned experiments.

Abstract: Practical engineering structures commonly display nonlinear dynamic response when damage is present in the system. Hence, the studies on nonlinear system identification have increased within these past few years. Current study is aimed on the structural identification of nonlinear systems based on the extraction of underlying linear frequency response function (FRF). The methods chosen to obtain the FRF are the Conditioned Reverse Path (CRP) and the Orthogonalised Reverse Path (ORP) method. The well-known frequency-domain CRP method has been recognised for its ability in solving nonlinear problems; detecting and quantifying nonlinearities in structures. In contrary, the ORP is a new algorithm developed in time-domain which gives simpler formulation for describing the underlying linear dynamics of nonlinear systems. Results show that the performance of the new ORP algorithm in handling nonlinearities is as good as the CRP method. The ability of ORP method has become the aim of the current study to assess the robustness of both algorithms towards nonlinear system identification of structures with multi-degree-of-freedom (MDOF) system.

Abstract: Investigation of methods of quality improvement of weld-fabricated building constructions. It is emphasized, this issue is subject to economical, social-psychological and technical factors. To the maximum extent, quality of weld-fabricated building constructions is affected by observance of requirements for accuracy of size and shapes. Accuracy of size and shapes is subject to the values of welding deformation resulting from nonuniform heating of work-pieces in the welding process and of welding heat input. The maximum heat input is observed in the process of manual (MMA) welding, the minimum heat input is a feature of mechanized (Mig/Mag) welding). Use of mechanized methods of welding will reduce welding deformation level and improve accuracy to size of construction.Experimental investigations of butt and fillet shapes have verified the conclusion.

Abstract: In construction practice, we often encounter a situation where there is overloading of the existing columns and pillars, namely due to various adaptations and extensions. Masonry columns and pillars are usually loaded with vertical forces. Overloading these structural elements leads to the crushing of masonry. To prevent the destruction of columns and pillars it is often proposed to reinforce these elements.The paper deals with the possibilities of using new innovative materials in the reinforcement of masonry columns, namely a "green" fiber cementitious composite with the so-called "strain hardening", which uses industrial waste mainly from the Moravian-Silesian Region.