الفهرس 
Column lateral bracingOnly 14 pages are availabe for public view
 |  | from | 179 |  |  |
| | | from | 179 | | |
Abstract
In most common situations, the strut member in the vertical bracing system is attached to the web mid-point of the I-section columns. In certain situations due to constructional conditions, this connection is constructed eccentrically. The current Egyptian Code of Practice for steel construction, (ECP No.205, 2001) and some other specifications such as; AISC 2010 specifications do not mention a way to treat this case, as a result, most design engineers calculate the column out-of-plane axial capacity by using the standard design equations without modifications.
The current research shows that there is a reduction in the axial capacity of columns with eccentric vertical lateral bracing which reaches at most 40% compared to the ideal case. The main aim of this research is to investigate the behavior of the I-section steel columns with eccentric vertical bracing and their failure modes, determining the reduction in the axial capacity for these columns, introducing a practical solution to enhance this eccentric connection to compensate the reduction in the axial capacity and proposing a design procedure in terms of new design formulas to predict the axial capacity of these columns.
A verified non-linear finite element model has been developed and a wide range parametric study has been carried out. This model takes into account the material and geometrical non-linearities. Different parameters are examined such as: variation of the eccentricity ratios, using different columns cross-sections, variation of the column out-of-plane slenderness ratios, various locations of the bracing joints along column length and different steel grades. ANSYS 14.5 computer program is utilized in this research.
Verification study was performed under three different phases including verification with the nominal compressive strength equations provided in the AISC 2010 specifications, previous experimental work and previous results developed from non-linear finite element analysis. The non-linear static analysis is performed by using the Modified Newton-Raphson (MNR) technique and employing the Arc-length control throughout the solution routine of the parametric study. The results of this parametric study are presented in graphs to show the influence of every parameter on the reduction in the column axial capacity due to the eccentricity in vertical bracing connection.
A proposed design procedure is introduced in this research by introducing modifications to the equations of chapter “E” in AISC (2010). Comparison between the finite element results and the new proposed design formulas revealed excellent agreement. The proposed design procedure will provide engineers with simplified method to estimate axial capacity of columns with eccentric vertical bracing.