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Hashmi S.S. Ahmed,G. Khushbu,M. Anbarasu,Ather Khan 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.90 No.2
This article presents the behaviour and design of cold-formed steel (CFS) web-stiffened lipped channel beams that primarily fail owing to the buckling interaction of distortional and global buckling modes. The incorporation of an intermediate stiffener in the web of the lipped channel improved the buckling performance leads to distortional buckling at intermediate length beams. The prediction of the strength of members that fail in individual buckling modes can be easily determined using the current DSM equations. However, it is difficult to estimate the strength of members undergoing buckling interactions. Special attention is required to predict the strength of the members undergoing strong buckling interactions. In the present study, the geometric dimensions of the web stiffened lipped channel beam sections were chosen such that they have almost equal distortional and global buckling stresses to have strong interactions. A validated numerical model was used to perform a parametric study and obtain design strength data for CFS web-stiffened lipped channel beams. Based on the obtained numerical data, an assessment of the current DSM equations and the equations proposed in the literature (for lipped channel CFS sections) is performed. Suitable modifications were also proposed in this work, which resulted in a higher level of design accuracy to predict the flexural strength of CFS web stiffened lipped channel beams undergoing distortional and global mode interaction. Furthermore, reliability analysis was performed to confirm the reliability of the proposed modification.
Vatankhah-Varnoosfaderani, M.,Hashmi, S.,GhavamiNejad, A.,Stadler, F. Royal Society of Chemistry 2014 Polymer chemistry Vol.5 No.2
Marine and freshwater mussels secrete proteinaceous adhesive materials for adherence to the substrates upon which they reside. It is well known that 3,4-dihydroxyphenylalanine (DOPA) is the key to understanding these mussel adhesive proteins (MAPs). In order to gain a better understanding of their complex formation and quick recovery upon rupturing, novel water soluble copolymers of N-isopropylacrylamide and dopamine methacrylate were synthesized in such a way that they have 1, 2.5, and 5 mole percent dopamine monomer with respect to the NIPAM monomer on average. The statistical distribution of DOPA-functionalities along the chain makes the material a close synthetic equivalent of the byssal thread proteins of mytili. At acidic pH, the aqueous copolymer solution behaves like an unentangled copolymer solution, but at basic pH, these catechol functionalities form a dicomplex with H3BO3, thereby crosslinking two chains, proven by B-11-NMR and gelation. The polymer solution is thermosensitive with a pH-dependent lower critical solution temperature (LCST) between 21 and 33 degrees C, depending on the DOPA-content. If 2 or more functionalities per chain are present, a gel is formed that is self-healing with very quick recovery from sustained damage. The moduli of the gels depend on the concentration of functionalities. Hence, triple stimuli responsive copolymers were obtained.