الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
In terms of the importance of cold-formed steel structural members, that plays an important role in modern steel structures due to their high strength and light weight. This study is initiated with the objective of investigating the behaviour and strength of bolted base connections for cold-formed steel frames. New configurations of bolted fixed and partially fixed base connections for cold-formed steel frames are suggested. These configurations can be used for economic and easy construction.
Verifications of the previous studies are carried out by finite element software program (ANSYS 12.0). There has a good agreement between the finite elements and previous result.
A numerical study is carried out by using “ANSYS 12.0”, different parameters are investigated for a fixed base connection that consists of double back-to-back cold-formed lipped channels, welded built-up I-shape stub with triangular stiffener plates and base plate. The channels column section is connected to the proposed welded built-up I-shape stub via transfer bolts. However, the I-shape stub is welded to the base plate and the base plate is connected to the concrete base by two types of anchorages. The first anchorage type is anchor bolts (A) and the other type is embedded plates (P) that consists of plates immersed in concrete base. Different parameters (i.e. different cold-formed column sections are chosen by their: width-to-depth ratio B/D, width-to-thickness ratio of their flanges, b/t, and depth-thickness ratio of their webs, D/t). Moreover, the I-shape stub is chosen according to its: width-to-thickness ratio of its flanges (b/t)I and the depth-thickness ratio of its webs (D/t)I. In addition, the base plate thickness, the type of anchorage with the concrete base and the arrangement of the transfer web bolts are considered. Two different patterns of the transfer web bolts are arranged as two columns. In the first pattern type (H), the transfer web bolts are placed between two columns of bolts at a distance equals half depth of column section (H= D/2). In the second type (T), the transfer web bolts are placed between two columns of bolts at a distance equals one-third the depth of column section (T=D/3).
Both large deflection analysis and elasto-plastic material behaviour are incorporated in a non-linear finite element model (ANSYS 12.0). The end conditions of the columns elastic lines are treated as fixed-free condition. The model is loaded with proportional load. The load acts through the center of gravity of the model at an angle of 45o. Newton-Raphson iteration technique is used in solving the nonlinear system of equations.
Based on the investigations, it is apparent that the stiffness of the base connections increases by decreasing both the width-depth ratio of cold-formed column section B/D and depth-thickness ratio of the welded built-up I-shape stub (D/t)I. Also, the stiffness of base connection increases by increasing the base plate thickness. Moreover, it is clear that the models with fixed base connections are more rigid than the models with partially fixed base connections. Eventually, the models with fixed and partially fixed base connections are classified as semi-rigid base connections according to Eurocode (EC3).