Experimental and Analytical Investigation of Deformations and Stress Distribution in Steel Bands of a Two-Span Stress-Ribbon Pedestrian Bridge

The article is dedicated to the analysis of problems related to design of pedestrian bridges with flexible ribbon bands made of steel. The study is based on test results of a bridge model that has two spans (each with a length of five meters). A simplified analytical technique has been proposed for predicting vertical deformations of the bridge structure subjected to symmetrical or asymmetrical loading patterns. The technique also allows assessing the tension forces in the ribbons, which are very important for design of such structures. The analysis reveals the importance of the flexural rigidity of the ribbons that might cause significant redistribution of stresses within the steel bands

A new method for formulating crack spacing models of RC ties

Cracking of concrete is one of the most complicated phenomena in reinforced concrete analysis and is one of the key aspects governing serviceability analysis of RC structures. Current methods for investigating cracking rely on empirical approaches that give unreliable results with errors of multiple times the real value. A new non-empirical method based on the combination of the stress-transfer and the smeared approaches is proposed for deriving crack spacing models. The stress-transfer approach governs the strain distribution of the reinforcement between the consecutive cracks whereas the smeared approach allows for the estimation of the mean strain of the element. The suggested method introduces the concept of damage zones: the bond in the area adjacent to the normal cracks is considered to be fully damaged, thus bond behaviour is non-uniform in the segment between cracks. Crack spacing models were derived using the load-strain analysis method presented in the Eurocode 2 and were shown to give results that are in good agreement with the crack spacing values taken from available experimental data

Discussion: Tension stiffening in concrete beams. Part I: Fe analysis

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Experimental Characterization of the Properties of Double-Lap Needled and Hybrid Joints of Carbon/Epoxy Composites

The effect of through-thickness reinforcement by thin 1 mm steel needles (z-pins) on the static tensile strength of double-lap joints of a carbon/epoxy composite was investigated. Two types of joints—z-pinned and hybrid (including glued ones)—were considered. The joints were reinforced in the overlap region with 9, 25, or 36 z-pins. Comparing mechanical properties of the double-lap joints with the corresponding characteristics of their unpinned counterparts, the z-pins were found to be highly effective: the strength and stiffness of the pinned joints increased up to 300% and 280%, respectively. These improvements were due to a transition in the failure mechanism from debonding of the joint in the absence of z-pins to pullout or shear rupture of z-pins or to the tensile failure of laminate adherends, depending on the volume content of the pins

Investigation of Shrinkage of Concrete Mixtures Used for Bridge Construction in Lithuania

The present paper reports results of the investigation on shrinking of the concrete mixture which is often used for casting the new bridges. The study is based on the experimental results obtained in three research projects which were performed under financial support provided by the Lithuanian State Fund of Research and Studies at the Vilnius Gediminas Technical University from 2005 to 2009. The accuracy of the most popular shrinkage prediction techniques was analysed using the test data. The analysis has shown that the Eurocode 2 method has given the most accurate predictions. The attention was also pointed on the analysis of the steel fibres influence on the shrinkage deformations of the structural concrete. The performed statistical analysis has indicated that the steel fibres application as admixture significantly reduced the free shrinkage strains. The paper has concluded that utilisation of the steel fibres is very effective way of increasing the service properties of concrete bridges