الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The behaviour of steel frames with semirigid
connections under earthquake excitation is investigated.
A general review of previous research concerning the
subject of semirigid connections is presented. The available
moment-rotation relationship of various beam-to-column
connections is presented. A bilinear idealization of the
available experimental moment-rotation curves for five
types of connections commonly used in practice is performed.
It 1s concluded that the rotational stiffness and yield
moment at a particular connection vary significantly by
changing the details of that connection. Therefore, it is
recommended for the analysis of frames with a particular
connection to determine the parameters of its bilinear model
from an ~xperimental moment-rotation curve of an identical
connection in a data bank, from the available analytical
expressions predicting the moment-rotation relationship for
that connection, or from the results of a full-scale test
for this connection. However, the approach used in this
research is based on obtaining the range of the parameters
of the bilinear model for each connection related to the
yield moment of the attached beam, and assigning appropriate
values for the parameters of each type of connections.
Moreover, the influence of the rotational stiffness of semirigid
connections on the fixed end moments, and the flexural
stiffness coefficients of a beam element are derived.
A general review of seismology and structural dynamics
is presented, and the methods of determining the response of
multi-degrees of freedom systems to earthquake ground
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motions are mentioned, from which the quasi-static lateral
forces approach and the time-history analysis are reviewed.
A discussion of earthquake-resistant steel structures is
presented, and a procedure for the analysis of steel frames
in seismic regions of Egypt is proposed. The general
stiffness matrix of an inelastic plane-frame element with
semirigid connections of nonlinear rotational stiffness is
derived, including second-order effects. Conversion of the
DRAIH-2D program to the microcomputer version is presented,
and the program features are summarized.
A variety of unbraced
bases either hinged or fixed,
connections are analyzed
and braced frames of column
with different semirigid
under various earthquake
excitations and quasi-static lateral forces, considering
the second-order P-6 effect and the nonlinear behaviour of
the rotational stiffness of semirigid connections, in order
to investigate their seismic behaviour. It is concluded that
x-braced frames with either fixed or hinged column bases
using any connection have the best behaviour under seismic
excitations where the bracing members are stiff enough to
control the drift, and the bending moments in columns, beams
and connections are slightly higher than their static
moments and hence, leading to a very economic design. The
same behaviour is observed fork-braced frames, but with
higher axial forces in bracing members. For all braced
frames, no yielding occurs in members or connections and no
inelastic buckling takes place in bracing members under the
chosen earthquakes. The unbraced frames with fixed column
bases have a moderate behaviour under seismic excitations
using any connection, where acceptable drifts are developed,
but the bending moments in columns are much higher than
their static moments or than those of braced frames, and
yielding occurs in frames with connections of low and
intermediate rotational stiffness. A poor behaviour under
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seismic excitat1ons is observed for unbraced frames with
h1nged column bases using connections of high and intermediate
rotational stiffness, where unacceptable drifts are
developed, and yielding occurs in frames with connections of
intermediate rotat]onal stiffness, while instability may
occur using connections of low rotational stiffness. For all
unbraced frames, a better behaviour under seismic excitations
1s obtained by increasing the initial rotational
st]ftness of connections.
Moreover, other analyses investigating the effect of
the nonl1near behaviour of the rotational stiffness of
semir]girl connections on the seismic behaviour of yielded
frames. and the effect of the second-order P-5 force on
the seismic behaviour of unbraced frames are also performed.
It is concluded that the nonlinear behaviour of the
rotational stiffness of semirigid connections slightly
changes the responses (horizontal displacements, total base
shear and bending moments in various sections) of unbraced
frames with fixed column bases using connections of low and
intermediate rotational stiffness over those of the linear
behaviour, and significantly changes the responses of
unbraced frames with hinged colt~n bases using connections
of Jntermediate rotational stiffness, while it may lead to
failure using connections of low rotational stiffness. The
same conclusions are observed for the effect of P-6 force.
Finally, another analysis invest]gating the effect of
damptng on the seismic behaviour of all frames is also
performed, from which it is concluded that for unbraced
frames damping significantly decreases the drift, the total
base shear, and the bending moments in columns, but
slightly decreases the bending moments in beams and
connections, while for braced frames damping significantly
decreases the total base shear and the axial forces in
brac1nq members and slightly decreases other responses.
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