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Major axis in-plane buckling resistance of I-section beam-columns under moment gradient
Published in Marian A. Giżejowski, Aleksander Kozłowski, Marcin Chybiński, Katarzyna Rzeszut, Robert Studziński, Maciej Szumigała, Modern Trends in Research on Steel, Aluminium and Composite Structures, 2021
Z. Stachura, M.A. Giżejowski, R.B. Szczerba, M.D. Gajewski
Many recent investigations refer to interpolation equations adopted in current design codes in order to propose alternative analytical-numerical formulations that allow for even more reliable reproduction of in-plane and out-of-plane buckling resistances of real (imperfect) beam-columns. Kucukler et al. (2015) developed a direct design method, the so-called stiffness reduction method, that takes into account the detrimental influence of imperfections and effect of distributed plasticity on the buckling resistance of beam-columns. Authors of this paper refined the so-called General Method of Eurocode 3 (2005) in their study of Gizejowski et al. (2019b). The study was referred to wide flange double-tee beam-columns of the size ratio h/b ≤ 1.2 (symbol H was used for such section identification). For the buckling resistance of H-section beam-columns, the degrading effect of imperfections, as well as the effect of inelastic stress redistributions across the sections and the member length were suitably included in the proposed formulation. For evaluating the in-plane buckling resistance of H-section beam-columns, the amplified second-order formulation developed introduced the model parameters which were calibrated (Gizejowski et al. 2019a). Since the developed approach would rather be considered as general but model parameters were calibrated for H-section beam-columns, it needs to be verified when postulated to be used in the buckling resistance prediction of I-section beam-columns for which h/b > 1.2. This study is entirely devoted to this issue.
First and second moments of area
Published in John Bird, Carl Ross, Mechanical Engineering Principles, 2019
The cross-sectional area of the tee beam =∑a=0.0056m2fromTable9.2.
Precast concrete beams
Published in Kim S. Elliott, Precast Concrete Structures, 2019
Determine the ultimate interface shear stress in the composite inverted-tee beam and floor slab in Example 5.8. If interface shear reinforcement is required, determine the spacing of the bars that will be positioned in the opened cores of 1200 mm wide hollow core units containing 11 cores at 100 mm spacing. Use fcki = 25 N/mm2 for the in situ infill and fyk = 500 N/mm2 for the interface shear reinforcement. The upstand of the beam has vertical shear keys conforming to BS EN 1992-1-1, Fig. 6.9.
Pseudo-Ductility Through Progressive Failure of Multi-Layered Carbon-Fiber-Reinforced Polymer (CFRP) Prestressed Concrete Beams
Published in Structural Engineering International, 2023
Ali Alraie, Nikhil Garg, Vasant Matsagar, Arndt Goldack, Mike Schlaich
In recent years, many research studies have been carried out in order to achieve ductile failure in FRP-reinforced structures. In 1999, the flexural behavior of concrete beams prestressed with CFRP tendons was evaluated.4 Later, in 2000, a full-scale test on an over-reinforced FRP-prestressed double-tee beam was performed,5 whose results were later used for the design and construction of the first US precast CFRP-prestressed concrete bridge. A design approach for vertically distributed CFRP tendons located at various depths within the cross section was developed later.6 Another full-sized American Association of State Highway and Transportation Officials (AASHTO) beam was fabricated and tested using high-strength concrete with emerging CFRP tendons for prestressing and reinforcement.7 The test showed that the beam exhibited extensive cracking and large deflections before failure of the tendons. In 2003, a unified design approach for the design of CFRP-prestressed concrete beams was proposed that was a strain-compatibility-based approach.8 This approach was validated by experimental results conducted on double-tee-beam bridge models. Furthermore, a compression-controlled failure mode was recommended as the design failure mode for the CFRP-prestressed concrete beams. This recommendation was based on the better ductility characteristics of the over-reinforced section over the under-reinforced section. In the fiber-reinforced polymer (FRP) prestressed concrete members, the concrete crushing failure mode was recommended over rupturing of the FRP reinforcement to compensate for the lack of ductility of the FRP tendons.9 Moreover, it was also concluded that, in any case, the member would not exhibit ductility as commonly observed in steel under-reinforced members. Possible solutions for improving the ductility include confinement of the concrete compression zone, use of hybrid FRP reinforcements or a combination of FRP reinforcements with different characteristics that fail at different strains, providing pseudo-ductility and enhancing structural redundancy through the addition of sacrificial rebars that do not lead to the collapse of the member once they fail.10 Finally, a combination of FRP and steel reinforcements may be used, particularly when the FRP is placed closer to the surface of the concrete and the steel deep inside.10