A plastic collapse method for evaluating rotation capacity of full-restrained steel moment connections

Abstract

An analytical method to model failure of steel beam plastic hinges due to local buckling and low-cycle fatigue is proposed herein. This method is based on the plastic collapse mechanism approach and a yield-line plastic hinge (YLPH) model whose geometry is based on buckled shapes of beam plastic hinges observed in experiments. Two limit states, strength degradation failure induced by local buckling and low-cycle fatigue fracture, are considered. The proposed YLPH model was developed for FEMA-350 WUF-W, RBS and Free Flange connections and validated in comparisons to experimental data. This model can be used to estimate the seismic rotation capacity of fully restrained beam-column connections in special steel moment-resisting frames under both monotonic and cyclic loading conditions.U ovom clanku je predstavljen formalini metod za modeliranje loma plasticnih zglobova formiranih u celicnim gredama zbog lokalnog izvijanja i zamora materijala. Ovaj metod je zasnovan na teoriji plasticnog loma i na YLPH modelu plasticnog zgloba formiranom od krutih ploca spojenih linijama plasticnog tecenja na osnovu geometrije izvijenih plasticnih zglobova testiranih celicnih greda u krutim ramoskim vezama. Lom u predlozenom modelu je moguc po jednom od dva granicna stanja: pad kapaciteta na savijanje zbog lokalnog izvijanja; i lom zbog nisko-ciklicnog zamora materijala. Predstavljen model je razvijen za FEMA-350 WUF-W, RBS i Free Flange krute ramoske veze i potvrdjen uporedjenjem sa eksperimentalnim merenjima. YLPH model moze da se koristi za procenu kapaciteta rotacije krutih ramoskih veza izmedju stubova i greda pod monotonim ili ciklicnim opterecenjem.