Laboratory and Numerical Analysis of Steel Cold-Formed Sigma Beams Retrofitted by Bonded CFRP Tapes

Abstract

In this paper, the retrofitting method of thin-walled, cold-formed sigma beams using bonded carbon fibre reinforced polymer (CFRP) tapes is proposed. The effectiveness of the presented strengthening method is investigated by the means of laboratory tests and numerical analysis conducted on simply supported, single-span beams made of 200 × 70 × 2 profile by “Blachy Pruszyński” subjected to a four-point bending scheme. Special attention is paid to the evaluation of possibility to increase the load capacity with simultaneous limitation of beams displacements by appropriate location of CFRP tapes. For this purpose, three beams were reinforced with CFRP tape placed on the inner surface of the upper flange, three with CFRP tape on the inner surface of the web, three beams with reinforcement located on the inner surface of the bottom flange, and two beams were tested as reference beams without reinforcement. CFRP tape with a width of 50 mm and a thickness of 1.2 mm was used as the reinforcement and was bonded to the beams by SikaDur®-30 adhesive. Precise strain measurement was made using electrofusion strain gauges, and displacement measurement was performed using two Aramis coupled devices in combination with the Tritop machine. Numerical models of the considered beams were developed in the Finite Element Method (FEM) program Abaqus®. Experimental and numerical analysis made it possible to obtain a very high agreement of results. Based on the conducted research, it was proved how important is the impact of the applied reinforcement (CFRP tapes) in thin-walled steel structures, with respect to the classic methods of strengthening steel building structures.

Influence of Mechanical Properties of Steel and CFRP Tapes on the Effectiveness of Strengthening Thin-Walled Beams

“…The length of the reinforcement tapes was 175 cm. A detailed description of the laboratory tests is presented in [ 1 , 2 ]. The schematic drawing of the laboratory stand is presented in Figure 1 a (dimensions are given in cm), while its real form is presented in Figure 1 b.…”

“…In recent years, CFRP (Carbon Fiber Reinforcement Polymers/Plastics) tapes have found widespread use for reinforcing concrete and masonry structures [ 1 , 2 ]. It became possible, thanks to the introduction of transparent and simplified design procedure rules, to use tapes for this type of construction [ 1 , 2 ].…”

“…In recent years, CFRP (Carbon Fiber Reinforcement Polymers/Plastics) tapes have found widespread use for reinforcing concrete and masonry structures [ 1 , 2 ]. It became possible, thanks to the introduction of transparent and simplified design procedure rules, to use tapes for this type of construction [ 1 , 2 ]. Currently, there are an increasing number of studies describing research on the use of CFRP tapes to strengthen timber structures [ 3 , 4 ], and even cast iron structural elements [ 5 ].…”

“…It should be emphasized that the motivation to take up this topic was the need to strengthen steel purlins made of cold-formed sigma steel elements (due to snowdrifts) in one of the supermarkets in Poland. Therefore, the authors of this study conducted a study of CFRP reinforced sigma beams [ 1 , 17 ]. Each time, the research showed a satisfactory effect of the use of CFRP tapes on the limitation of strain and displacements of the reinforced elements.…”

Experimental Optical Testing and Numerical Verification by CuFSM of Compression Columns with Modified Channel Sections

“…The purpose of the finite element research described in Czapski and Kubiak [ 17 ] is to investigate the effect of residual stresses on the behaviour of thin-walled laminates loaded in compression. Szewczak et al [ 18 ] conducted a numerical analysis of simply supported beams. The beams were reinforced with special CFRP tapes.…”