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In this paper, an attempt was made to determine the load-bearing capacity of a bonded joint of galvanized steel elements with carbon fiber reinforced polymer (CFRP) fabric. This issue is extremely relevant to the use of bonded carbon fiber fabric as a mean of reinforcing hot-dip galvanized steel structures. This technique is used in engineering practice for both hot-rolled and cold-formed steel elements. In order to obtain the necessary parameters for modelling bonded joints of galvanised steel thin-walled elements, laboratory tests were carried out. In the first stage, four specimens made of 50 mm diameter steel cylinders bonded to 16 mm thick hot-dip galvanised steel sheet of S350 GD were subjected to the pull-off test. In this connection the SikaWrap 230C composite fabric embedded in SikaDur 330 adhesive layer was investigated. In the second stage, the axial tensile test of the bonded butt joint using the same materials was performed. In this stage, 10 hot-dip galvanised steel sheet samples of S350 GD and 16 mm thickness were tested. The discussion on the failure mechanism in the context of the bonding capacity of the composite joint was carried out. Moreover the advanced numerical model using the commercial FE program ABAQUS/Standard and the coupled Cohesive Zone Model was developed. The significant influence of the preparation method of steel element surface and the thickness of the adhesive layer on the failure mechanism of the joint and the value of the maximum failure force was shown. [ABSTRACT FROM AUTHOR]

The main aim of the study is an assessment of models suitability for steel beams made of thin-walled cold-formed sigma profiles with respect to different numerical descriptions used in buckling analysis. The analyses are carried out for the sigma profile beam with the height of 140 mm and the span of 2.20 m. The Finite Element (FE) numerical models are developed in the Abaqus program. The boundary conditions are introduced in the formof the so-called fork support with the use of displacement limitations. The beams are discretized using S4R shell finite elements with S4R linear and S8R quadratic shape functions. Local and global instability behaviour is investigated using linear buckling analysis and the models are verified by the comparison with theoretical critical bending moment obtained from the analytical formulae based on the Vlasow beam theory of the thin-walled elements. In addition, the engineering analysis of buckling is carried out for a simple shell (plate) model of the separated cross-section flange wall using the Boundary Element Method (BEM). Special attention was paid to critical bending moment calculated on the basis of the Vlasov beam theory, which does not take into account the loss of local stability or contour deformation. Numerical shell FE models are investigated, which enable a multimodal buckling analysis taking into account interactive buckling. The eigenvalues and shape of first three buckling modes for selected numerical models are calculated but the values of critical bending moments are identified basing on the eigenvalue obtained for the first buckling mode. [ABSTRACT FROM AUTHOR]

In the paper the modern measurement methods of structural deformation using GOM optical measuring systems based on digital image processing were presented. First part of the work demonstrates the results of measurement of initial geometrical imperfections of steel structural elements using the Tritop optical 3D coordinate measuring machine. The method of preparation of sigma type steel beams with a height of 200 mm, a flange width of 70 mm and a wall thickness of 2 mm is presented. Afterwards, the subsequent stages of measurements and the method of reading the obtained results and their interpretation are described. The next step presents a test stand designed to perform strength tests of thin-walled sigma beams in a four-point bending scheme. In addition, the method of preparation of beam’s surface to measurement of 3D using the Aramis system and electrofusion strain gauges is presented. The deformation values obtained for three sigma-type steel beams were compared with respect of two mentioned measurement methods. The final conclusions and recommendations regarding the methodology of geometry and strain measurement using optical measuring systems complete the work.

The main aim of the study is to develop the best-suited FEM numerical model of beams made of thin-walled cold-rolled steel profiles retrofitted by CFRP tapes. The FEM model fitting has been carried out based on own laboratory tests conducted on S type beams. The CFRP tapes are bonded to the beam at compressed or tensioned flange. The most important part of this study is focused on the investigation of boundary conditions influence in FEM model developed in Abaqus program. Moreover, the numerical models are also tested in terms of different mesh density and type of finite elements. Numerical analyses are carried out using a Newton-Raphson iterative method to solve the non-linear equilibrium equation. In the paper, special attention is paid to the evaluation of the possibility to increase the load capacity by appropriate localisation of CFRP tape. [ABSTRACT FROM AUTHOR]

In this paper, the results of laboratory tests and numerical analyses of thin-walled beams strengthened with carbon fiber reinforced polymer (CFRP) are presented. In particular, tensile tests of the steel and carbon fiber Sikar CarboDurr S tapes were conducted. Full scale laboratory tests included six sigma beams, each 140 mm high, 3 m long and with a wall thickness of 2.5 mm. The laboratory specimens were assumed as simply supported, single-span beams subjected to a uniformly distributed load. Four of the tested beams were reinforced with carbon fiber tapes, and the other two were not reinforced and were considered as reference beams. Numerical models of the considered beams were developed in the Abaqus program and subjected to validation and verification based on laboratory results. In the paper, special attention is paid to the evaluation of the possibility of increasing the critical load capacity while simultaneously limiting displacements of the beams by appropriate positioning of CFRP tape. The work completes with comparative analysis and conclusions. [ABSTRACT FROM AUTHOR]

Steel structure designers frequently encounter the need to reinforce hot-rolled compressed steel elements. This is particularly common in the case of compressed truss bars in steel truss girders. Typically, reinforcement is designed using bars or flat bars welded to the compressed element. However, welding technology is not always feasible in existing and operational steel halls due to fire safety concerns. To address this challenge, researchers investigated alternative reinforcement methods using bonded steel and CFRPs (carbon fiber-reinforced polymers/plastics) tapes. Laboratory tests and numerical analyses were conducted. Eleven 1.5 m long specimens made of 50 × 50 × 4 angle iron from S235 steel were subjected to axial compression testing. The test samples included three unreinforced samples, three samples reinforced with steel tape bonded using SikaDur-30 adhesive, and five samples reinforced with CFRP tape (SikaDur-30 adhesive was used for bonding in three cases, and 3M VHB GPH-160GF tape in two cases). The research conducted indicates that reinforcement using bonded steel tapes is the most effective method for limiting vertical displacements and deformations, as well as increasing the load-bearing capacity of the tested angles by 28.6% compared to the reference elements. Considering the high cost of composite tapes, this is valuable information from an economic analysis perspective. The absence of steel tape delamination suggests that the bonding technique can be successfully employed in this reinforcement method and can replace welding, for example in facilities where there is a high fire hazard.