الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
The use of composite beams systems consisting of reinforced concrete (RC) slabs and hot-rolled steel sections is well-studied and their design is well-described in many current specifications and codes. There is, however, little scientific and technical information available for the use of composite cold formed beam systems despite the marked potential for this system in residential and light industrial construction markets.
This thesis presents an Experimental investigation and numerical analysis using nonlinear 3-D finite element model for composite cold formed steel beams. Experimental tests are carried on full scale composite cold formed steel (CFS) beams. The steel beams consist of two cold formed steel channel sections back to back which connected to a reinforced concrete slab using new means to transfer the shearing force between them to achieve the composite action. Two groups of beams have been tested. In the first group, the composite action has been achieved using the embedment of the upper part of steel section inside the concrete slab. In the second group, the composite action is achieved using the reforming of the steel flange inside the concrete slab to act as shear connectors. The parameters studied in the first group are the ultimate strength of the concrete (fcu), height of the embedded part of the steel section in the RC slab (hemb.), effect of the interaction between shear and bending moment depending on the loading method, the direction of the applied load with respect to the beam position, and effect of encasing steel web with concrete. While the studied parameter in the second group is the spacing between the new shear connectors developed from the reforming of the steel section flange. The beams’ ultimate strengths, load-mid span vertical deflection relationships and failure modes of the beams have been recorded from the tests .The nonlinear analysis has been performed using ABAQUS/CAE. The ultimate strengths, mid -span vertical deflection and failure modes from nonlinear analysis are compared with the experimental results to verify the accuracy of the developed FE models.
For the beams of the second group with the shear connector results from the reforming of the upper flange, the resistance of the shear connector is un-known. For that, Seven push out specimens are tested so as to make a parametric study to determine the effect of the variation of different parameters on the strength of the shear connector, the steel section consists of two cold formed steel channel sections back to back of thickness ( tst ) and 30 cm height and yield strength ( fy ) which connected to a reinforced concrete columns (15cm *15cm) of 30 cm height of compressive strength ( fcu ) using means of new shear connector ,the new shear connector is developed from the reforming of a part of the steel section flange so as to be embedded inside the concrete to resist slippage between steel and concrete. The studied parameters are the compressive strength of the concrete (fcu), the yield strength of the steel (fy), the breadth of the shear connector (b), the height of the shear connector (h) and the thickness of the steel (tst).A finite element model has been used to simulate the behavior of the real test so as we will be able to study more parameters with more variations using ABAQUS/CAE, and also an empirical formula can derived to calculate the strength of the suggested shear connectors.