الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 180 |  |  |
| | | from | 180 | | |
Abstract
Prestressing techniques have been widely applied over the last five decades because
of the advantages it provides to steel beams. Applying this technique results in increasing the
beam capacity and leading to a substantial material saving. Also, prestressing a steel beam
reduces its deflection under the same service loads, accordingly it enhances the beam
behavior from the serviceability limit state point of view.
It has been realized that most researchers give attention to the prestressed composite
structure elements. Few researchers studied the behavior of prestressed steel beams.
Therefore, the objective of this research is to thoroughly understand the structural behavior of
steel beams under prestressing condition to develop a simple and rational design method to
help the designer to assess the strength and behavior of such beams.
Prestressing a steel beam changes the loading condition from a beam to a beamcolumn,
changing drastically its structural behavior. Therefore it is necessary to investigate
the behavior of beam-column under axial force and bending moment as a first step.
Accordingly the structural behavior of beam-column structural elements is thoroughly
investigated theoretically and numerically using numerical analysis. Mathematical model has
been developed to predict the ultimate capacity of steel I-beam under axial force and bending
moments. This model is capable to account for initial imperfection. The results of the
mathematical model were verified against the nonlinear elasto plastic analysis using F.E.
analysis. Also the results of the developed model have been compared well with the
international design codes.
Finite element models were developed using ANSYS code [4] to investigate the
effects of many parameters on the ultimate capacity of prestressed steel I-beams. The
nonlinearity of both materials and geometries were considered. The developed finite element
models were verified against the results of previous researches using both experimental tests
and analytical results. Then, a parametric study was carried out. The parametric study
covered different cross section dimensions, span length, unsupported length, number of
deviators, tendon’s configuration, tendon’s eccentricity and prestressing force. The analyzed
beams were categorized according to the loading types; uniform bending moment load, line
load and single concentrated load at mid span.
iii
A method to predict the capacity of the prestressed steel I-beam subjected to uniform
bending moment is developed. The principles of the strain compatibility and the virtual work
method were adopted in the proposed method to predict the tendon traction force. Both the
tendon traction force and the pervious proposed equations in beam-column behavior were
utilized to calculate the ultimate capacity of prestressed steel I-beams. Some applications of
the proposed method were presented. The proposed method results were verified with the
nonlinear finite element analysis results.