الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 176 |  |  |
| | | from | 176 | | |
Abstract
In continuous steel-concrete composite castellated beams, subjected to hogging bending, the laterally unrestrained bottom flange of the steel I-section of the composite castellated beam is under compression, therefore is sensitive to a local and/or a restrained distortional buckling phenomenon,
Distortional buckling (DB) is a buckling mode in which lateral deflection and twists arc combined with changes in the cross sectional shape This arises generally from web distortion because in most I sections, flanges are comparatively stocky and any flange distortions arc smalL Web distortion allows the flanges to deflect laterally with different angles of twist reduces the resistance of the member and consequently reduces the resistance to buckling,
Therefore the ultimate resistance of a continuous composite castellated beam is governed by either distortional lateral buckling, local buckling, or an interactive mode of the two which is sharply different from the torsional buckling mode in a bare steel beam.
An efficient nonlinear 3D finite element models have been developed using ABAQUS software is used for the analysis of both simple and continuous composite beams under vertical loads, The initial geometric imperfection and material nonlinearities were careful!) considered in the analysis, The reliability of the models is demonstrated by comparisons with experiments and with alternative numerical and analytical analyses. Different modeling techniques available in ABAQUS were used for the modeling of the shear connectors.
An extensive parametric study was carried out using the finite element models to study the effects of the change in cross-section geometries, alignment of stiffeners, web slenderness, beam length, variations in the concrete and steel material properties and the concrete slab thickness on the buckling behavior and on the overall structural behavior of continuous composite castellated beams under uniformly distributed loads.
2 groups (28 subgroup) and 1 group (1 subgroup) of continuous steel-concrete composite ~astellated beams with initial geometric imperfection, 96 beams in total are studied by means of the FE method,
Based on the findings of the finite element modeling, a number of recommendations on the methods of modeling and on the design of continuous steel-concrete composite castellated beams are suggested.
Keywords: Castellated beams, Composite beams, Distortional buckling, Finite clement.