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Free vibration analysis of stiffened laminated plates using layered finite element method
Guo, Meiwen,Harik, Issam E.,Ren, Wei-Xin Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.3
The free vibration analysis of stiffened laminated composite plates has been performed using the layered (zigzag) finite element method based on the first order shear deformation theory. The layers of the laminated plate is modeled using nine-node isoparametric degenerated flat shell element. The stiffeners are modeled as three-node isoparametric beam elements based on Timoshenko beam theory. Bilinear in-plane displacement constraints are used to maintain the inter-layer continuity. A special lumping technique is used in deriving the lumped mass matrices. The natural frequencies are extracted using the subspace iteration method. Numerical results are presented for unstiffened laminated plates, stiffened isotropic plates, stiffened symmetric angle-ply laminates, stiffened skew-symmetric angle-ply laminates and stiffened skew-symmetric cross-ply laminates. The effects of fiber orientations (ply angles), number of layers, stiffener depths and degrees of orthotropy are examined.
Concentrically Loaded Circular RC Columns Partially Confined with FRP
Sahar Y. Ghanem,Issam E. Harik 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.5
Wrapping reinforced concrete (RC) columns with fiber reinforced polymer (FRP) composites is effective in increasing their capacity. The current state of the art concentrates primarily on fully wrapped columns and few studies dealt with partially wrapped ones. The objective herein is to evaluate the effectiveness of partial wraps (or strips) and to develop a confined concrete compressive stress.strain (fc - εc) model that accounts for partial wrapping. Three-dimensional finite element (FE) models are generated to evaluate the influence of different parameters on the behavior of concentrically loaded RC circular columns that are partially and fully wrapped with FRP. The results indicated an increase in ductility as the number of FRP strips is increased, and revealed that longitudinal steel had little influence on the confined fc . εc relationship. The proposed fc . εc model, derived from the parametric study, accounts for the effect of partial and full confinement, the unconfined concrete strength f ′c , and yielding of transverse steel. Comparison of the results generated using the proposed model with FE and experimental results are in good agreement.